Skip to main content <#maincontent>
We will keep fighting for all libraries - stand with us!
Internet Archive logo A line drawing of the Internet Archive
headquarters building façade.
Search icon An illustration of a magnifying glass.
Search icon An illustration of a magnifying glass.
Upload icon An illustration of a horizontal line over an up pointing
arrow. Upload
User icon An illustration of a person's head and chest. Sign up
| Log in
Web icon An illustration of a computer application window
Wayback Machine
Texts icon An illustration of an open book.
Books
Video icon An illustration of two cells of a film strip.
Video
Audio icon An illustration of an audio speaker.
Audio
Software icon An illustration of a 3.5" floppy disk.
Software
Images icon An illustration of two photographs.
Images
Donate icon An illustration of a heart shape
Donate
Ellipses icon An illustration of text ellipses.
More
Hamburger icon An icon used to represent a menu that can be toggled by
interacting with this icon.
Internet Archive Audio
Live Music Archive Librivox Free
Audio
Featured
* All Audio
* This Just In
* Grateful Dead
* Netlabels
* Old Time Radio
* 78 RPMs and Cylinder Recordings
Top
* Audio Books & Poetry
* Computers, Technology and Science
* Music, Arts & Culture
* News & Public Affairs
* Spirituality & Religion
* Podcasts
* Radio News Archive
Images
Metropolitan Museum
Cleveland
Museum of Art
Featured
* All Images
* This Just In
* Flickr Commons
* Occupy Wall Street Flickr
* Cover Art
* USGS Maps
Top
* NASA Images
* Solar System Collection
* Ames Research Center
Software
Internet Arcade Console
Living Room
Featured
* All Software
* This Just In
* Old School Emulation
* MS-DOS Games
* Historical Software
* Classic PC Games
* Software Library
Top
* Kodi Archive and Support File
* Vintage Software
* APK
* MS-DOS
* CD-ROM Software
* CD-ROM Software Library
* Software Sites
* Tucows Software Library
* Shareware CD-ROMs
* Software Capsules Compilation
* CD-ROM Images
* ZX Spectrum
* DOOM Level CD
Books
Books to Borrow Open Library
Featured
* All Books
* All Texts
* This Just In
* Smithsonian Libraries
* FEDLINK (US)
* Genealogy
* Lincoln Collection
Top
* American Libraries
* Canadian Libraries
* Universal Library
* Project Gutenberg
* Children's Library
* Biodiversity Heritage Library
* Books by Language
* Additional Collections
Video
TV News Understanding 9/11
Featured
* All Video
* This Just In
* Prelinger Archives
* Democracy Now!
* Occupy Wall Street
* TV NSA Clip Library
Top
* Animation & Cartoons
* Arts & Music
* Computers & Technology
* Cultural & Academic Films
* Ephemeral Films
* Movies
* News & Public Affairs
* Spirituality & Religion
* Sports Videos
* Television
* Videogame Videos
* Vlogs
* Youth Media
Search the history of over 835 billion web pages
on the Internet.
Search the Wayback Machine
Search icon An illustration of a magnifying glass.
Mobile Apps
* Wayback Machine (iOS)
* Wayback Machine (Android)
Browser Extensions
* Chrome
* Firefox
* Safari
* Edge
Archive-It Subscription
* Explore the Collections
* Learn More
* Build Collections
Save Page Now
Capture a web page as it appears now for use as a trusted citation in
the future.
Please enter a valid web address
* About
* Blog
* Projects
* Help
* Donate
* Contact
* Jobs
* Volunteer
* People
* Sign up for free
* Log in
Search metadata
Search text contents
Search TV news captions
Search radio transcripts
Search archived web sites
Advanced Search
* About
* Blog
* Projects
* Help
* Donate Donate icon An illustration of a heart shape
* Contact
* Jobs
* Volunteer
* People
Full text of "Electronics & Wireless World 1614
"
See other formats
THE JOURNAL FOR PROFESSIONAL _ ENGINEER
ELECTRONICS
& WIRELESS WORLD
APRIL 1987 £1.95
Spectrum
analysis
techniques
Development
of an h.f.
receiver
Reducing
quantizing
processor
tone decoder
Multi-to-
single-
element
transform
PERFORMANCE WITH ECONOMY
Ш Self calibrating — =
@ High performance yet easy t
il Compact, lightweight and portable ^
№ Mains or 42V d.c. vehicle battery
Optional 24V d.c. working or internal
NiCd battery pack
№ Laboratory, vehicle or outdoor operation
№ Hard copy evidence with optional printer
№ Six picture stores/control setting memories
E AM and FM demodulation. Built-in ioudspeaker
E Broadband measurement range (300kHz to 1000MHz)
№ Direct field strength readings in dB microvolts possible
Bl Check aerial efficiency, spurious emissions,
adjacent channel and intermodulation interference, etc
_ Full colour brochure available from: FARNELL INTERNATIONAL .
WETHERBY . 1522 4DH . ИК. INTTEL +44 937 61961. TELEX 55478 FARINT G
The 352C
Communications
Spectrum
Analyser
from...
ENTER 1 ON REPLY CARD
APRIL 1987 VOLUME 93
COVER
Marconi Instruments’ 2383 spectrum
analyser. Analysis using such instruments
is the subject of this month’s feature,
starting on p.359
SPECTRUM ANALYSIS
359
Current developments in the facilities
provided by spectrum and frequency-
response analysers are explored and
explained
HIGH-PERFORMANCE
COLOUR GRAPHICS
CONTROLLER
368
Half a megabyte of memory and a new video
control i.c. make fast and versatile colour
graphics
by John Adams
INCREASED RESOLUTION
FROM AN A-TO-D
CONVERTER
373
“Dither” and an averaging technique
provide interpolation
by R.A. Beck
PIONEERS – 4
381
Charles Wheatstone made so many
inventions they could fill a book
by W.A. Atherton
A RADICAL APPROACH TO
MICROPROCESSOR DESIGN
394
Hardware details for the Novix Forth
processor
by W.P. Watson
DESIGNING А
COMMUNICATIONS
RECEIVER
409
Design techniques used in a new British
receiver, intended to out-perform Far-
Eastern competition at lower cost
by J.R. Thorpe
ELECTRONICS & WIRELESS WORLD
Mandelbrot pattern generated by John
Adams’ graphics board described on
p.368.
CLASS D AMPLIFICATION
FOR INDUSTRIAL
CONTROL
415
Recent mosfet transistors bring fresh power
and performance to pulse-duration
modulation, removing historical
limitations
by Barry Friedman
THE MULTI-ELEMENT
TRANSFORM
421
A suggestion for overcoming the two-
source limitation of the inverse square
law
by J.C. Belcher
TONE DECODING USING А
MICROPROCESSOR
428
A simple approach to microprocessor-
controlled tone decoding provides
an excellent signal-to-noise
ratio
by Christopher H. Gough
IMAGE ACQUISITION
SYSTEM
441
A low-cost sensor, when used with
processing software, is adequate for use in
security, robotics and character
recognition
by G.J. Awcock, F.W. Stone and
R. Thomas
NUMBER 1614
SCIENTIFIC INTERFACE
FOR THE AMSTRAD PCW
454
Although sold as a low-cost word processor
the PCW8256/8512 can make a useful
laboratory computer.
by Brian J Frost
ALCATEL AND ITT
456
Alcatel and ITT combine to link IT,
computers and telecommunications.
by Adrian Morant
īa eee маш
COMMENT 355
SATELLITE SYSTEMS 377
APPLICATION NOTES 385
UPDATE 390
TELECOMMS TOPICS 403
CIRCUITIDEAS 407
RESEARCH NOTES 424
NEW PRODUCTS 434-439
TELEVISION BROADCAST 445
RADIO BROADCAST 446
RADIO COMMUNICATIONS 447
FEEDBACK 450
WORKFILE 458
353
This is just a sample of our huge inventory — contact us with your requirements.
ANALYSERS
8447D Amplifier £600
OSCILLOSCOPES Philips 9816S Persanal Camputer £2550
Hewlett Packard PM5 134 Function Generator £1325 9825A apt001 -002 DeskTapComputer £700
180 TR 100MHz Scope M/F (Mint) £1500 РМ5326АМ/ЕМ Generator £1130 98256A256KRAMboord,series200 £250
1744A 100MHz Storage Scope £2350 PM55191TV Pattern Generator £600 ?862APlotter £500
Philips Wavetek 9872C 8-pen flatbed plotter £1000
PM3266 100MHzStarage Scope £4570 184 5MHz Sweep Generator £650 9915A Computer £750
PM3305P 35MHz Digital Storage £1925 1080 1 GHz Sweeper £1500 GENERAL PURPOSET&M
PM3540 Logic Anal/Scope £1500 HEWLETT PACKARD Farnell
Tektronix m
465B/DM44100MHzScope2DMM £2000 COMPUTERS im + TTS 520 Transmission Test Set £4275
465B 100MHz Scope £1450 7220АС M I8 £350
475A/DM44200MHzScope/DMM — £2500 саца д
485 350MHz Scope £4500 G. Р. Industrial
608 Manitor £1500 МЕ. 373 Fault Locatar. MINT £395
634 opt 1,20 Display Monitor £750 Hewlett Packard
2465 300MHz Scope £3450 436A Pawer Meter £1200
5223 Scope M/F (Mint) £3600 467A Amplifier £600
71041GHzScopeM/F £16000 3403C True RMS
7603 100MHzM/F £1950 Voltmeter £1850
7704A 200MHz 3406A Sampling
Mainframe £2850 Voltmeter £1250
7834 Fast Storage Scope 3465A 41/2 Digit
M/F £7500 Г Ф D.M.M. £350
R7603 100 MHz Rack 4271A 1 MHz Digital LCR
MINT M/F £1950 meter £2500
7904 500 MHz Scope 4271B Digital LCR
M/E £5500 ү” Meter £2500
A large selection of 53008 + 5305B 1300
7000 series plug-ins «агч MHz Counter £495
available at up to 60% 5381A 80 MHz
saving on list. Please Counter £225
call far quotations. WV? аы 8447А Amplifier £400
Marconi
Hewlett Packard TF 1246 Oscillator £500
141T Display TF 1313A LCR Bridge
Moinframe £2000 0.1% $750
3582А Spectrum ТЕ 2173 Synchroniser
Analyser £7500 for 2016 £450
4193A Impedance TF 2304 Modulation
Analyser £5250 Meter £450
8552 Е Section £2500 ТЕ 2603 ВЕ
8553B RF Section, Millivoltmeter £495
110MHz £2650 TF 2604 Voltmeter £425
Marconi TF 2702 Inductor
TF2330A Wave Analyser £850 Anolyser £950
TF 2370 110MHz Spectrum TF 2905/8 TV Pulse .
Anolyser £9650 Generotor £750
TF 2371 200MHz Spectrum TF2915Doto Monitor £1200
Anolyser £10500 TF2950/5 Mobile Radio TS. £1350
Tektronix Philips
7114 Spectrum Analyser P.In £10500 85A Microcomputer £995 PM55801IF Modulator £3000
308 Data Analyser £1500 | D СА эе ‘The Portable’ pe PM5581 RFConvertor £1000
ouchscreen PM5582 RF Convertor 1000
SIGNAL SOURCES 2673A Thermal Printer £550 scm za
Hewlett Packard 6940B Multiprogrammer £950
4204A Digital Oscillator £395 7470A opt001/002 A4 2-pen plotter £600 520A Vectorscope (NTSC) £3750
8007B Pulse Generator £950 7475A opt 001/002 A3/A4 521 АРА! Vectorscope £4500
8011A-001 Pulse Generator 20MHz £695 6-pen plotter £1050 51 Sampling Head £850
8601 A Sweep Generator £1750 7910H ор!01 5 Disk Drive £450 S.3A Sampling Head £1250
861 4A SignalGenerator £3950 82913A 12 inch Monitor £75 1411 Сор!ОЗТУ Signal Generator £5500
86260A Sweep Gen. Plug-in 82937AHPIBInterface £150 A6901 Isolation Monitor £275
12.4-18GHz £3500 82938A HPIL Interface £150 4041 System Controller £8800
86408 001-002 AM/FM 829394 Serial interface e206: Р ТЫ7Револшнумойше pore
SignalGenerator £4500 — §2940AGPIO Interface £350, PM107Persondlity Module ERA
8690BSweeper Mainframe £950 86B Microcomputer £650 PM 108 Personality Module £650
Marconi 9111AGraphics Tablet £850
2015-1 AM/FM Signal Generator £950 9121DSingle-sided Disc Drive £550
TF2002B AM/FM Signal Generator £995 9122D Dual Double-sided Disc Drive £875
All prices are exclusive of VAT and correct at time of going to press ® Carriage and packing charges extra ® A copy of our trading conditions is available on request
пәке ==, Electronic Brokers
140-146 Camden Street, London NW1 9PB
Fax: 01-267 7363. Telex: 298694. Tel: 01-267 7070
ENTER 85 ON REPLY CARD
==
EDITOR
Philip Darrington
DEPUTY EDITOR
Geoffrey Shorter, B.Sc.
01-661 8639
TECHNICAL EDITOR
Martin Eccles
01-661 8638
PROJECTS EDITOR
Richard Lambley
01-661 3039 or 8637 (lab.)
NEWS EDITOR
David Scobie
01-661 8632
ART EDITOR
Alan Kerr
DRAWING OFFICE
Roger Goodman
01-661 8690
ADVERTISEMENT MANAGER
Ashley Wallis
01-661 3130
Michael Downing
01-661 8640
CLASSIFIED EXECUTIVE
Susan Platts
01-661 3033
ADVERTISING PRODUCTION
Brian Bannister
(Make-up and copy)
01-661 8648
PUBLISHING DIRECTOR
Clive Foskett
01-661 3151
ELECTRONICS & WIRELESS WORLD
Guest editorial, contributed bv Bob Giddy, General Manager. NEC Electronics (UK) Ltd.
Eastern promise
t could be argued that the British industrial machine kas not always benefitted from this country's
I membership of the EEC. For the UK electronics industry to succeed in Europe, the entrenched
forces o*theother European multi-nationals must give up some of their long-held territory – а
gesture they are unlikely to offer voluntarily, particularly in those sectors regulated by local PTTs,
In the US. hawking British electronics isa little like trying to sell sand to the Arabs - many companies
have tried it, but have not prospered.
The third largest, and fastest growing, market area is the Pacific basin excluding. for the moment,
Japan. Most of this area, particularly Thailand, the Philippines and Taiwan, is part of the US capital
investment zone. These countries are cash-rich with low overheads and are already recipients of
technology transfers. As such, they are heavily dependent upon United States investment and thus are
difficult market areas for British companies.
Itisclear that new marketing areas must be sought in which new rules can be applied. We must find
markets that are able and willing to absorb our products. If "necessity isthe mother of invention," then
need is the father of demand.
The UK has а good record for innovation and design. Its reputation for reliable manufacturing has not,
until recently, been so good. A partnership with a nation possessing complementary skills to our own
would surely be fruitful.
The solutions I proposed to these two problems of finding new markets and partners may seem
foolhardy on the surface, but we do have precedents.
As partners, I suggest the Japanese. There are many similarities between the countries and our people.
We are islanders and consider ourselves somehow different to continentals. We are. or have been,
successful in developing markets. We are monarchies, with consequent political stability. The British are
famous (or notorious) for compromise - the Japanese will avoid conflict if at all possible. In both
countries, a man's word is reputed to be his bond.
The Japanese have a truly awesome reputation for manufacturing technology. It is claimed and
recognized, even by the Japanese, that they are not innovative. Perhaps this is why they modelled their
education system upon our own and may be why they so admire and respect British innovation and
design skills. The Japanese need to develop strategic friendships: their spectacular successes have
brought them problems of trade friction, dumping disputes etc. They are looking for joint-venture
partners, not partners of the purely commercial kind, of which the result is just another distributor. The
partnership must offer joint benefit, as in the British Leyland/Honda venture, where each partner's skills
complemented the others.
Asa solution to the problem of a new market area. the Comecon countries have a great deal to offer (|
did say it might appear foolhardy). The population of these countries is greater than that of Europe and
about the same as that of North America; if China is included, then it is about 2.5 times that of the US. To
cultivate the Comecon market would clearly be politically sensitive and sale of some types of equipment
would not be permitted. It must be said that it is difficult to see how the sale of a few computers, or even a
complete communications system, is going to destabilize the military status quo. However, these
equipments, if they are to be marketed successfully. must be free of restrictions on vital components – а
very real problem when a product is obtained from US companies.
The germination and growth of such a partnership, targetted at new markets, would take time to
establish. To allow for this lead-time, the next generation ofequipments should be of overriding interest.
In my own fieid of semiconductors, for example, we should aim at the rapidly evolving field of computers
and communications. As before. it will be semiconducting technology that will define the architecture of
the equipment. Starting at the very heginning, we should explore areas of interest, he it research, design,
manufacturing, or some of each. We should share the reponsibilities and agree the form in which the
marketing of these future products is to be carried out. In other words, the two partners must be
intrinsically locked together. thus avoiding the usual importer/exporter relationship. The partners
would possess complementary skills which would be harnessed and directed towards working toa
common goal.
Our two nations are a world apart, but that does mean thev are well placed to see hoth sides.
Electronics & W reless World is published monthly USPS £14.50 outside UK. Distribution: ат House, The
687540 Current issue price £1.95, back issues (if available) Quadrant, Sutton, Surrey SM2 5AS. Telephone 01-661
£2.10 at Retail and Trade Counter, Units 1&2, Bankside
Industrial Centre, Hopton Street, London 5Е1 Telephone:
01-928 3567. By post, current issue £2.25, back issues (if
available) £2.50. Order and payments to 301 Electronics
and Wireless. World, Quadrant House, The Quadrant,
Sutton, Surrey 3M2 5AS. Cheques should be payable to
Reed Business Publishing Ltd Editorial & Advertising
Offices: EWW Quadrant House, The Quadrant, Sutton,
Surrey SM2 5AS. Telephones: Editoria. 01-661 3614.
Advertising 01-561 3130 01-661 8469 Telex: 892084
BISPRS С (EEP' Facsimile: 01-661 2071 (Groups lt & 111)
Beeline: 01-661 3978 or 01-661 8986. 300 baud, data bits,
even parity, one stop-bit. Send ctrl-Q, then EWW to start:
NNNN to sign off. Subscription rates: 1 year £18 UK and
£23 outside UK Student rates: ] year £11.50 UK and
3248. Subscriptions: Oakfield House, Perrymount Road,
Haywards Heath, Sussex RH16 ЗОН. Telephone 04444
59188. Please notify a change of address. USA: $49.40
surface mail, $102.60 airmail. Reed Business Publishing
(USA). Subscriptions Office, 205 E. 42nd Street, NY 10117.
Overseas meets | agents: France and Belgium:
Pierre Mussard, 18-20 Place de la Madeleine, Paris 75008
United States of America: Jay Feinman, Reed Business
Publishing Ltd. 205 East 42nd Street, New York, NY
10017. Telephone (212) 867-2080 Telex 23827. USA
mailing ееп Mercury Airfreight International Ltd,
Inc., 10b) Englehard Ave, Avenel N.J. 07001. 2nd class
postage paid at Rahway NJ. Postmaster - send address to
the above. ©Reed Business Publishing Ltd 1986. ISBN
0043 6062
355
Not only in height is the range of Clark Masts wide but also in the
field of application. Every model, mechanical or air-operated,
has been created in response to customer requirement
and proved in service; for over 25 years.
Major users in the Communications Industry,
Broadcasting, Civil Authorities and Military
Commands worldwide, have all contributed
and benefited from Clark Masts
reliability and ceaseless engineering
improvement.
Write for your
copy of Clork
Masts Fast
Guide to Mast
Selection. and
see what we mean
CLARK MASTS CLARK MASTS TEKSAM LTD. (WW). Binstead, Isle of Wight CLARK MASTS TEKSAM NV.'WW.. Woudstraat 21
England. Tei: (0983) 63691. Telex: 86686
3600 Genk, Belgium. Tel: 011/38.08.31. Telex: 39354
ENTER 15 ON REPLY CARD
VESTIGIAL SIDEBAND
TELEVISION MODULATOR C.C.I.R/3
CRYSTAL CONTROLLED OSCILLATOR
19" RACK MOUNTING, 1u HIGH, 205mm DEEP
C.C.I.R/3 SPECIFICATION
Power Requirement 240V B Watt (available In other voltages
Video Input 1V Pk-Pk 75 Ohm
Audio Input 8V 600 Ohm CHANNEL COMBINER/FILTER/LEVELLER
F.M. Sound Sub-Carrier 6MHz {available §. MHz} ОсОО modulators
Modulation Negative
LF. Vision 38.9MHz 2 Channel Filter/Combiner/Levelier: Insertion Loss 3.5dB
LF. Sound 32.9MHz (available 33.4MHz 4 Channel Filter/Combiner/Leveller. Insertion Loss 3.548
Sound Pre-Emphasis Enables up to 4x TCFL2 or TCFL4 to be combined,
Ripple on 1.Е. Saw Filter 598
Output (any channel 47-B60MHz *6dBmV (2mV) 75 Ohm
Vision to Sound Power Ratio to 1
Intermodulation
Spurious Harmonic Output 5s daB Bg N Red wan тон Filter or com TAYLOR BROS (OLDHAM) LTD
BISLEY STREET WORKS, LEE STREET,
C.C..R./3.1 Specification as above but output level 600BmV OLDHAM, ENGLAND.
— o LLL Mmm | TELEPHONE: 061 652 3221 TELEX: 669911
ENTER 29 ON REPLY CARD
50us
356 ELECTRONICS & WIRELESS WORLD
ADCOLA
Soldering Systems
FEATURES include..
ADCOLA
Model 151
€ fume control soldering ;
station
€ 90% solder fume
removal
no moving parts
no magnetic effect
no tip voltage
no mains interference
À
A
uF
№
>
1
no real maintenance
costs (bit/tip changes
only}
variable lockable
temperature 120°C -
420°C
© total 50 watt electronic
control (+ 2%)
@ simple plug-in bits/tips
€ electrical safety approved
240V 24V
SEE US AT THE ALL ELECTRONICS SHOW - STAND 1/42
IV Soldering NEW EXTENDED RANGE...
4 ADCOLA ADIRON °
ri
105 |
1А long life bits/tips simple plug-in type suitable tor
B42LL B3BLL BSOLL BI4LL B35LL Ваа BILL 83742 B46LL B4OLL both Unit 101 and other Adcola soldering tools.
&
А.
© The basis of the total
ADCOLA soldering wave
nc op machine systems
W. B th € Simple, quiet, clean
ave а operation from
a 240V single phase
Idering — сз,
€ Complete, with air
Machine extraction and
AIDCOLA,
Low cost/high volume
Regd Trade Mo-k'
ELECTRONIC PRODUCTION EQUIPMENT
For ano obligation demonstration, please contact:
ADCOLA PRODUCTS LIMITED Gauden Road London SW4 6LH
Telephone Sales (01) 622 0291 Telex 21851 Adcola G
Sales Offices also at Bristol + Bournemouth e Preston e Glasgow
ENTER 42 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD 357
TRANSFORM YOUR CONVENTIONAL SCOPES
WITH THE SOUPADAPTUR 1111 INTO A
4 MODES OF OPERATION
D2 CH. FFTA.
00-50Н2 Span to 0-20kHz Span.
OFull ANTI-ALIAS filtering.
0200 line resolution.
040 dB dynamic range.
OSelectable LOG/LIN Amplitude.
UHanning/Rectangular weighting.
OFast update speed.
OUp їо 128 averages + peak.
OOverload indicators.
D2 CH. D.S.O.
U50kHz sampling rate (max.)
00.5% vertical resolution.
OTimebase from 5 sec/div to 1 msec/div
OComprehensive trigger facilities
OSingle shot.
01% or 2596 pre-trigger
0512 point horizontal resolution
ODisplay ‘freeze’ control
OSPLIT MODE
OSimultaneous display of frequency and time
domain.
0100 line resolution for both frequency and
time traces.
DDUAL MODE
OTime and frequency traces correlated
OSame samples used for both domains.
OSingle shot mode
OSample rate up to 100kHz,
0200 line resolution for both traces.
A REVOLUTIONARY NEW CONCEPT
IN TEST AND MEASUREMENT
OTrue real time F.F.T. analysis.
OFull Anti-Alias Filtering.
OD.S.O. with extensive triggering.
OPeriodic and transient waveform
analysis.
ORS423/232 out.
ODirect connection for plotter,
printer or computer.
ENTER 61 ON REPLY CARD
DATA ACQUISITION
LIMITED
Electron House, Higher Hillgate,
Stockport, Cheshire SK1 ЗОО
Tel: 061-477 3888 Telex: 666839
DEVELOPED AND
MANUFACTURED IN THE U.K.
IF YOU NEED
Analysers at realistic prices...
u Es к
ANRITSU EUROPE LIMITED
Thistle Road, Windmill Trading Estate, Luton,
Beds. LU1 3XJ, England.
858541
хаа а а
[à be bou
L
. . . High Performance Spectrum
Then you need to call
Telephone: Luton (0582) 418853 Telex: 826750 Fax 31303
358
ENTER 76 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD
Anritsu
Advances in spectrum
analysis
Undoubtedly the most versatile item of test equipment
used by r.f. and microwave engineers, the modern
spectrum analyser provides a host of functions that would
traced back to the work of French
mathematician Baron Jean-Baptiste
Fourier in the early part of the nineteeth
century. He showed that any waveform,
however complex, can be generated by
adding together sine waves. The converse of
this is also true, any complex waveform can
be broken down into individual sine waves.
Spectrum analysis is thus Fourier analysis,
breaking down a signal into its component
frequencies.
A spectrum analyser is undoubtedly the
most versatile item of test equipment used
by r.f. and microwave engineers. It not only
separates a signal into its component parts
but also measures power and frequency,
determines distortion, noise and intermo-
dulation, identifies spurious signals, and
evaluates modulated signals.
Before studying spectrum analysis furth-
er, examine more closely what a spectrum
analyser does and compare it with the
measurements that can be made by an
oscilloscope. Figure | shows a three-
dimensional graph with three mutually per-
pendicular axes calibrated in terms of ampli-
tude, frequency and time. The signal shown
consists of a sinewave with a second harmo-
nic. The process of signal analysis is to
display the components of such a signal.
Two-dimensional displays are used, as three-
dimensional displays are not practical.
A time-domain display of amplitude ver-
sus time is the familiar type of oscilloscope
trace. Only a single waveform would be seen
when the signal in Fig. 1 is viewed — the
waveform with the solid line — but there are
in fact two sinusoids present, as shown by
the dotted lines. As oscilloscope shows the
total waveform and does not therefore sepa-
rate out the individual components.
Analysing the same signal in the frequen-
cy domain, as would be seen on a spectrum
analyser, reveals the two separate compo-
nents. The amplitude and frequency of the
fundamental is represented by a single ver-
tical line and the second harmonic by a
shorter line, clearly seen to the right of the
fundamental.
Oscilloscopes are not so widely used by r.f.
and microwave engineers because the fre-
quency range of oscilloscopes is limited;
they are hardly ever used at frequencies
above 1GHz.
T: origins of spectrum analysis can be
ELECTRONICS & WIRELESS WORLD
have been impossible a few years ago.
STEVE GLEDHILL
TIME DOMAIN
f
FREQUENCY OOMAIN
1. Signal analysis, the relationship between frequency, time and amplitude.
Rf input
Crystal
oscdiator
Tracking generator о/р
2. Heterodyne spectrum analyser block diagram.
The display of amplitude against frequen-
cy is much more useful because spurious
signals, sidebands and noise can also be
detected. Oscilloscopes are not able to iso-
late such subtleties of complex signals.
A further advantage of a spectrum analys-
er is its high sensitivity; it can measure very
low level signals down to less than 0.1,.V
simply because it is selective rather than
broad-band. It can also display low-level
signals at the same time as high-level signals
because logarithmic amplitude scales are
used; an oscilloscope, which has a linear
vertical scale, does not have this capability.
359
IMPLEMENTATION
All r.f. and microwave spectrum analysers
have the same basic system configuration
based around the principle of a swept, tuned,
superhet radio receiver. Other techniques
are encountered for very low frequency
spectrum analysis but all higher frequency
instruments have a basic block diagram
similar to that shown in Fig.2. In practice
the implementation is more complex and
there are many more frequency conversion
stages.
Before the input signal is applied to the
mixer it passes through an input attenuator
so that the sensitivity of the instrument can
be changed. An input filter is generally also
included at this stage to avoid i.f. feed-
through. An input amplifier may also be
incorporated.
The mixer converts the input signal to a
fixed intermediate frequency, at which point
a range of band-pass filters can be switched
in to change selectivity. Further amplifica-
tion is included at the i.f. stage to increase
sensitivity. Most instruments have a vertical
scale calibrated in decibels, and to accom-
plish this the signal at the i.f. stage is passed
through a logarithmic amplifier. The signal
is then applied to a detector before being
applied to the vertical scale of the display.
Video filtering may be incorporated after
the detector. A low-pass video filter to reduce
the statistical variability of displayed noise
helps to reveal coherent signals which may
otherwise be obscured by noise.
The horizontal input of the display is
driven by a variable-amplitude ramp gener-
ator also applied to the voltage-controlled
oscillator that feeds the mixer. As the ramp
voltage is increased the receiver tunes to
progressively higher frequencies and the
trace on the display moves from left to right.
A spectrum display is thus generated.
Changing the amplitude of the ramp
generator fed to the oscillator changes the
width of spectrum which is analysed, since
the voltage-controlled oscillator sweeps over
a greater or lesser frequency range.
The applications of a spectrum analyser
are greatly increased if a tracking generator
3. A modern high resolution spectrum
analyser, Marconi Instruments 2385.
360
Frequency analysis
An alternative method for analysing the frequencies within
a spectrum is offered by a frequency response analyser
(f.r.a.) which can provide a precise measurement of gain
and phase of frequencies within a given spectrum.
he analysis of dynamic systems has
| been of interest to mathematicians
and scientists for centuries. Newton,
Laplace and Volterra, among others, all
addressed the problem of relating the
observable behaviour of dynamic systems
to some form of mathematical descriptor.
The origins of the practical approach to
dynamic analysis are, however, much
more recent. The advent of radar in the
1940s, and the consequent development of
the remote-operating weapon delivery sys-
tem, demanded the provision in quantity of
high-accuracy, fast-responding servo-
controlled actuation systems. Verification
of the performance of such systems under
operational conditions was not possible;
hence, complex test procedures were de-
vised to determine their acceptability for
operational use. The principles of practical
dynamic analysis were founded.
In 1954 Solartron, in collaboration with
the then Admiralty Research Laboratories
at Teddington, developed the first
commercially-available general purpose
dynamic analysis instrument; the VP250
Resolved Component Analyser, the fore-
runner of today’s frequency response ana-
lyser. The instrument is still in use in many
major testing laboratories throughout the
world. Since then Solartron have carved a
niche for themselves and are, they say, the
only producers of stand-alone frequency
response analysers in the world.
The f.r.a. works rather like a synthesized
radio receiver; it can sweep through the
frequencies within a range and record the
amplitude and phase response of a system.
This is displayed (in words and numbers)
on the front panel and can also be recorded
on a plotter, or transferred to a computer
for further analysis and storage.
Two new instruments have been intro-
duced, one of which is aimed at reducing
the cost of the analyses; the other increases
the frequency range and facilities.
А typical mode of operation involves the
use of an internal generator to stimulate
the system under test. The waveform fre-
quency can be automatically swept be-
tween user-defined limits with a logarith-
mic spacing of frequency increments. A
ELECTRONICS & WIRELESS WORLD
‘vernier’ facility allows the operator to vary
the frequency, amplitude or d.c. bias
manually in order to find a resonant peak,
or a null position and then set an offset for
subsequent measurement. À modulator is
included for the testing of transducers and
systems which require ап a.c. carrier.
It is also possible to synchronize the
instrument to be triggered by an external
signal, such as a tachometer output when
testing rotating machinery. The 1253 gain-
phase analyser has two input channels with
amplifiers which automatically range the
signal to ensure the best resolution and
optimum signal/noise ratios for the incom-
ing signals. It operates over the frequency
range 1mHz to 20kHz. Gain and phase
measurement accuracies are 0.1dB and
1.0° respectively. Input signals are digi-
tised to 15-bit resolution using Solartron's
patented pulse width technique, which
ensures data integrity and provides a stable
four-digit display. In common with other
instruments in the range, this analyser
uses a single-sine correlation analysis
technique to provide fast and precise
measurements of both amplitude and
phase. The correlation technique rejects
the harmonic components of a non-linear
system response, accurately measuring the
fundamental component of a signal even
when it is buried in noise. А common
analyzer measures the gain and phase
response of the system, thus minimizing
channel mismatching problems for two-
channel measuremerit. The process in-
herently rejects harmonics. Noise is re-
moved by integrating the signal over a
number of cycles. Each input can be
programmed to demodulate signals from
systems operating with an a.c. carrier.
The 40-character display provides the
menus for setting up the instrument as
well as measured data and status informa-
tion. Data is presented in either polar or
Cartesian coordinates along with the
appropriate variable (frequency, ampli-
553 FAEZUERD
T
ЕЕ:
QU. 20-03 “cits
ELECTRONICS & WIRELESS WORLD
tude, or bias). Results can be calibrated and
scaled with a constant or vector. The vector
can be a previous measurement and read-
ings can be made relative to a reference
point, or systematic errors can be nulled.
Measurement sequences can be stored
in program files internally so that regular
tests can be repeated. Keyswitch protec-
tion of routine measurement sequencies
prevents unauthorized alteration. The in-
ternal battery-backed memory can also
store up to 400 measurements for output
to a printer or plotter through the RS232/
423 or GPIB interfaces included. The GPIB
interface also offers automatic, remote,
operation.
The instrument offers a simplified level
of frequency analysis which should find
applications in production testing, quality
assurance, the testing of goods supplied
and in educational establishments.
Solartron hopes that the comparatively
low cost of the 1253 (£4800) will open up
new markets and make the instrument a
general-purpose tool for use by a variety of
laboratories and test facilities.
Enhanced frequency range and resolu-
tion are offered by the second instrument,
the 1255 (£8900), which has all the above
facilities and offers a 12-decade frequency
range, from lpHz up to 20MHz and а
130dB dynamic range, making it ideal for
testing of video amplifiers, filters. crystals,
and communications equipment, and for
many applications in electrochemistry,
solid state physics and mechanical testing.
The instrument features two indepen-
dent channels operating in parallel and
offering basic gain and phase accuracy of
0.024В and 0.2? respectively, and a fre-
quency resolution of 1:65,536.000.
In addition to frequency response
measurements the 1255 measures group
delay and can modify any results using
standard arithmetic operators. Up to nine
programs can be stored in permanent
eprom storage with keyswitch protection.
ТЕ CO: 56129
800. ODE-12
GROUP DELAY
200, E-12
s/div
_ 4-800, 20Е-12
‚елет
18.2220605+0
A general-purpose analyser is the Advan-
test TR4131 which covers 10kHz to 3.5GHz.
Input sensitivity is —116dBm with a dyna-
mic range of over 70GB. Available through
Chase Electronics, Tel: 01 878 7748.
is included, especially for r.f. types. A track-
ing generator provides a swept signal whose
instantaneous frequency, is always the same
as the input tuned frequency so that the
frequency response of components, devices
or systems can be measured over a wide
dynamic range. Figure 3 shows a modern
high, resolution spectrum analyser with
built-in tracking generator.
MEASUREMENTS
When measuring distortion the harmonics
of a signal are displayed individually, as
shown in Fig. 4. The amplitude of the
fundamental and each of the harmonics can
be measured and the total harmonic distor-
tion calculated. This figure, and the other
screen displays mentioned in this article,
was obtained by connecting a digital plotter
to the instrument to obtain a high quality
hard copy.
A typical display of frequency modulation
is shown in Fig.5, where a 1КН2 modulation
tone has been applied to а narrowband f.m.
transmitter. Spectrum occupancy can be
measured from such a display. Bessel zeros
can also be determined. A Bessel zero occurs
when the amplitude of the carrier or a
sideband falls to zero, a crucial measure-
ment for the calibration of f.m. systems.
Amplitude modulation depth, distortion and
spurious f.m. canall be readily determined.
The detection and measurement of spu-
rious signals is of great importance. Synth-
esizers, for example, can generate a number
of unwanted products and these need to be
determined. Spurious signals and noise can
be generated by all types of electrical and
electronic equipment, and interference may
be caused if such signals are radiated from
the equipment, or if the noise is conducted
along mains cables or other connecting
cables. Spectrum analysers are widely used
to track down such unwanted radiated and
conducted signals.
OPERATIONAL ADVANCES
Spectrum analysers have become easier to
use over the last 20 years. Earlier instru-
ments were highly complex and the operator
had to be skilled and needed a great deal of
361
THERES A МЕМ ALTERNATIVE
>TR4131SPECTRUM | |
ANALYSER (10KHz-3.5GHz) |
The TR 4131 with its wide frequency range is an |
ideal general purpose, portable, spectrum
analyser, perfectly suited for the measurement
of UHF harmonic and spurious signals. With a
sensitivity of -116dBm, and a dynamic range in
excess of 70dB, facililties provided include
frequency and level markers, signal averaging
direct field strength readout. This versatile instru-
ment offers remarkable cost performance savings
Features not Options: as standard
> GP-IB interface
> Direct plotter dump
> CISPR RFI/EMC functions
> Composite video output |
> Signal track
For applications requiring a tracked signal
there is a choice of two tracking generators |
ТВ 4153 (10KHz-2GHz) and ТВ 4154
(100KHz-3.5GHz)
ADVANTEST. FROM
—— |
ADVANCING TECHNOLOGY | | „Жуз к
CHASE ELECTRONICS LTD · ST LEONARDS HOUSE MORTLAKE LONDON SW14 7LY TEL 01-878 7748 TELEX 25520 CHASE С FAX 01-8765928
ENTER 30 ON REPLY CARD
in
||!
M |
|
| М Ш
ыы
Frequency 64
response and root-locus. Features include transport delays, non-linearities,
compensators etc. Inclusive price £220
€ SIGMA: A flexible package for signal generation, manipulation and analysis. Unique high-level language, forward and inverse Fast Fourier Transforms, time and
frequency domain convolution, multiplication etc. Features include flexible generation of signals and spectra, noise, non-linearities, quantisation. Inclusive price £190
All packages have been designed for rapid interaction and flexibility and are suitable for use professionally and in teaching. Comprehensive manual and tutorial session
included. Details of these and other packages available on request.
Golten &Verwer Partners
33 Moseley Road, Cheadle Hulme, Cheshire SK8 5HJ.
ENTER 50 ON REPLY CARD
QUALITY QUARTZ
CONTROL SYSTEM DESIGN
AND SIGNAL ANALYSIS FOR
THE BBC COMPUTER
© CODAS-PLUS: An enhanced version of the successful CODAS package for
control system design and simulation. Transient response, frequency
Telephone: 061-485 5435
(24 hour answer phone)
LOW COST UNIVERSAL PROGRAMMER
EPROMS EEPROMS MICROS
CRYSTALS QUICKLY
Our frequency ranges are:
.P.U. Crystals
lagen Oscillators
JOkHz 50kHz 100kHz 500kHz 1MHz 100MHz 250MHz 360MHz
Professional Crystals
We also supply quartz crystal filters,
oscillators of all types and
communication antennae.
~ :
Webster Electronics
ILMINSTER, SOMERSET TA19 90А. ENGLAND
TEL: (046 05) 5166 TELEX: 46571 FRONCY С
FAX (046 05) 5865
ENTER 52 ON REPLY CARD
362
* Completely seif contained unit
* No personality modules required
* Controlled via RS232 senal interface
© Supports Intel. Motorola and Ascii hex data
formats
* Easily controlled by most computers
* Fast and standard programming modes.
* Low and high byte programming for 16 bit data
* Byte. block and chip erase for Eeproms
EN
Price uncased £295 plus VAT.
2 St. Stephens Road : Cheltenham : Glos : GL51 5AA
ENTER 63 ON REPLY CARD
* Eproms
2508/16/32/64
2758
2716/32/32A/64/64A/128,
128A/256/512/513
27C16/32/64/128/256/512
68732/64/66
* Eeproms
2816A/64A 52B13/23/33 48202
* Micros:
8748/48H/49/49H
Tel: 0242 510525
ELECTRONICS & WIRELESS WORLD
А d8m Harmonic distortion. MARCONI A dBm Frequency modulation. MARCONI
0.0 Atten 20d8 50a TG off 2382 0.0 Atten 40d8 502 TG off 2382
-20.0 -20.0
E " ИШИ iina
-40.0 -40.0 {| | | t
: = ОДА,
E m MAII BAD: I "
-70. 0 -70.0 T
-80. 0 -80. 0 үү үү
-100.0 -100.0
DADDD | Ref 65. OMHz 10. OMHz/div Res bw 300kHz Олррр X Ref 250. ODDDOMHz 2.00kHz/div Res bw [100 Hz
Avg ц] Inc 10MHz 10ms /div Vid bw ПАН; Avg В Inc 2kHz 1 s /div Vid bw поо ня
4. Typical spectrum analyser display of harmonic distortion.
5. Typical spectrum analyser display of frequency modulation.
patience. It is instructive to study the areas
where the operation of spectrum analyzers
has been improved in recent designs.
When using a sweeping spectrum analyser
it is essential to sweep at the correct speed.
Sweeping too fast causes distortion due to
group delay variations in the filter system of
the analyser such that the displayed signal
amplitude and frequency is incorrect. Mod-
ern instruments incorporate
microprocessor-controlled sweep speed con-
trols so that the instrument always sweeps at
the correct speed. Where high resolution is
required the sweep speed may need to be as
slow as 100 seconds, and it is easy to
appreciate the gross errors that would occur
if a sweep of 100ms for example was used for
such a measurement. Sweep speed is also a
function of video bandwidth if video filtering
is used after the detector for noise smoo-
thing.
Another area where microprocessor con-
trol is now used is in the selection of
sensitivity. To increase the sensitivity of an
analyser the user can either reduce the r.f.
input attenuator or increase the i.f. gain.
Reducing the input attenuator may overload
the input mixer, which would cause distor-
tion in the instrument. The alternative is to
increase the i.f. gain, but this could increase
the noise to an unacceptable level. The
choice of which control to operate is not
immediately obvious and is even more in-
volved when one considers that the opti-
mum noise and distortion trade-off not only
changes for different signal levels but also
when different bandwidth filters are
selected. Automatic optimization of r.f. and
i.f. gain is thus an important innovation,
since it prevents the operator from inadver-
tently introducing distortion in the measur-
ing instrument.
Older instruments initially used long per-
sistence tubes to display slow sweeps. Stor-
age tubes were introduced as a better
alternative but they are expensive and un-
satisfactory for slow sweeps. Digital storage
is now used, giving added advantages: for
example, a live trace can be compared with a
stored one, or two traces can be subtracted.
Electronic graticules can also eliminate pa-
ELECTRONICS & WIRELESS WORLD
rallax error. A further advantage of modern
digital displays is that control settings can
also be shown on the screen for ease of
reading and interpretation.
Perhaps the three most significant im-
provements that the microprocessor has
provided are easier front panel operation,
synthesized tuning and programmability.
Modern instruments can be controlled from
a digital keyboard so that set-ups can be
rapidly changed. Complete front panel con-
trol settings can be held in non-volatile
memory. Synthesized tuning is a great
benefit because not only can the tuned
frequency be entered from a keyboard but
the frequency of tuning is referred to a
crystal oscillator for increased accuracy and
resolution with a reduction of frequency
drift. Synthesized tuning has other advan-
tages: sideband noise is now significantly
better because of the use of phase-locked
oscillators.
Programmability is increasingly impor-
tant. Modern spectrum analysers can be fully
remotely controlled, usually using the
General Purpose Interface Bus (GPIB).
Screen information can be dumped for
further detailed analysis, for archiving pur-
poses or for the determination of the ampli-
tude and frequencies of the individual sig-
nals.
SPECIFICATION ADVANCES
Many spectrum analyser users have not
necessarily been aware of the amplitude
inaccuracy of their instruments. There are
many sources of uncertainty in the measure-
ment chain from the input attenuator
through to the logarithmic amplifier and
display. To make matters worse the values
change with temperature and frequency. In
an attempt to improve accuracy, screwdriver
pre-set controls have been incorporated on
the front panel, but even when set correctly
uncertainties can exceed +3 or +44В. With-
out setting up, the uncertainties can be even
larger.
Microprocessor control is now used to
improve accuracy and screwdriver pre-set
controls can be eliminated. The self-
calibration routine which is used in the
instrument shown in Fig.3. is very compre-
hensive. Pressing a key on the front panel
initiates the process which includes:
—setting the amplitude and frequency of
each ofthe 12 resolution filters
— measuring and correcting for the attenua-
tion of each of the r.f. input attenuator
steps
— correcting the amplitude response of the
system by sweeping through the entire
frequency range by routing the built-in
precisely levelled tracking generator into
the input.
The advantage of this self-calibration techni-
que is that total level accuracy is improved to
a remarkable figure of +1dB for all levels
and frequencies and for any span or resolu-
tion bandwidth.
Spectrum analysers are used to assess the
purity of oscillators by measuring close-in
noise and power supply ripple. When car-
rying out such close-in measurements, it is
essential to use a narrow resolution filter. A
filter that is too wide will swamp low level
signals close to the carrier; Fig.6 illustrates
this. A signal of 50MHz is analyzed with a
span of 10Hz/division; two traces are shown.
The wider response was taken using a 10Hz
resolution bandwidth which, up to now, has
been the narrowest available on most spec-
trum analysers. The narrower response used
the 3Hz filter. The 10Hz filter could not
resolve the low level 50Hz component but
the 3Hz filter clearly shows it.
Improved filter resolution will obviously
be a very important consideration when
specifying spectrum analysers. but the shape
factor of the filter as well as the minimum
resolution bandwidth is also critical. The
shape factor is the ratio of the 604В band-
width to the 3dB bandwidth.
There is a further bonus from having a
narrower filter — spurious signals which
would othenvise be obscured by the internal
noise floor can be seen. A quality spectrum
analyser typically has a noise figure of
around 20 to 25dB and a 10Hz filter would
thus limit the noise floor to typically
— 1354Вт: а 3Hz filter would reduce the
noise floor Бу 5dB to around — 140dBm. This
363
А dBm
-25. 0
SOHz line sidebond.
Atten 20dB 50a
A
[2]
[*]
^
^
MARCONI
2382
“Lt
1
-35. 0 4 — ie ЕР А dBm Low pose filter. MARCONI 8 dBm
i -14.7 Atten 2038 a TG -10. 0d8m 2382 -14. 70
-45. 0 " |
r -19.7 -15. 20
1
-55. 0 4 : -24.7 «715. 70
П
-65.0 L -29.7 -16. 20
=75.0 -34.7 -16. 70
-в5. 0 -39.7 -17. 20
-44.7 -17. 70
-95. 0
-49.7 718. 20
-105. 0
-54.7 -18. 70
-115.0 PST -19. 20
-125. 0 =—s -64.7 E -19. 70
DADDD Ref 50. 000030MHz 10.0Hz/div Res bw 10 Hz ОАРРР Ref 12. OOMHz 1.00MHz/div Res bw [ 3kHz 0
Inc 10Н2 1 е /div Vid bw [434] Avg 4 Inc IMHz Ѕ00те /div Vid bw 2.B8kHz Avg 4
6. A 3Hz filter enables close-in hum sidebands to be measured.
The 10Hz filter would have masked this signal.
7. Dual vertical scale used to view simultaneously the overall
frequency response of a filter as well as the pass-band ripple.
aspect may be important for measurements
such as synthesizer purity and checking for
Spurs.
Many spectrum analyser users will be
surprised to realise that, until recently, a
first class instrument could only claim a
— 704Вс or —80dBc intermodulation per-
formance. Modern mixer technology and
careful r.f. design can improve this figure to
typically greater than —90dBc. An additional
benefit of a modern design is that gain
compression can effectively be eliminated so
that the operator need not normally worry
whether distortion is generated within the
instrument.
A notable facility is the ability to display a
signal with two different vertical scales at the
same time. Adjusting a complex filter for
optimum pass-band ripple and maximum
out-of-band attenuation can be time con-
suming because adjustments can affect both
characteristics. A dual vertical scale, as
illustrated in Fig.7, allows the operator to
simultaneously read out of the display store
with two vertical resolutions. In this exam-
ple a 12.4MHz low-pass filter is analysed
with one scale of 5dB/division and the other
of 0.5dB/division.
SOFTWARE FEATURES
It has been shown how the man-machine
interface has been improved and automatic
optimization of controls has made measure-
ments more foolproof. Specification points
such as accuracy, resolution and intermo-
dulation performance have been improved.
A final area of improvement is due to the
software features in an instrument. These
further improve the man-machine interface
and also provide a number of functions to
increase efficiency and reduce operator
time.
Steerable markers are particularly signifi-
cant: a control is used to move a dot over the
display so that the frequency and amplitude
of any chosen point can be determined. A
‘delta marker’ facility is particularly useful,
which displays the difference in amplitude
and frequency between two points on the
364
screen to simplify measurements such as
harmonic distortion or modulation fre-
quency.
Markers can also be controlled by key
strokes from the front panel. Functions
known as 'peak find' and 'next peak' enable
the operator to direct the marker to the peak
signal on the screen and to then identify
successively lower amplitude signals. This is
particularly valuable when measuring har-
monic distortion, since the amplitude of
each of the harmonics can be rapidly ascer-
tained; such а facility is essential when used
in a remote control application.
The reference level and frequency of tun-
ing of a spectrum analyser can be controlled
with markers. Once a marker has identified a
signal of interest the operator can simply
press 'Marker sets reference level' and 'Mar-
ker sets reference frequency' buttons to
bring the chosen signal to the top of the
screen and to the centre of the screen. This is
a great advantage over the previous manual
method. Signal tracking, another software
feature, can be used to keep a signal of
interest at the centre of the screen by
re-tuning the instrument if the signal of
interest is drifting in frequency.
Often it is necessary to make adjustments
to a device in order to meet a particular
specification. Many operators have resorted
to using a grease pencil to draw limit lines on
the screen, but modern software makes this
unnecessary, limits can now be entered from
the keyboard and the tolerance lines display-
ed electronically.
Software manipulation of a sweep is also
useful. Modern instruments can change the
traditional linear frequency display to a
logarithmic display to aid interpretation and
analysis. Software can also digitally compen-
sate for the loss and frequency response of
cables and probes. One technique, which
requires a built-in tracking generator, is to
connect the cable or probe to the tracking
generator output socket and to carry out a
frequency sweep and store the response
values in a digital memory. When subse-
quent measurements are made the values in
the memory are used to correct the mea-
sured value so that a corrected or normal-
ized display is given. A further software
facility is А-В, one trace subtracted from
another to assist when comparing two simi-
lar signals.
The modern spectrum analyser provides a
host of functions and a specification that
would have been impossible a few years ago.
The new generation of instruments are
lower in cost than their predecessors be-
cause advanced manufacturing techniques
and complex automatic testing have reduced
costs significantly. A wider range of instru-
ments is available now to cater for higher
and lower performance and for different
frequency ranges, so that expensive un-
wanted frequency coverage can be avoided.
S.J. Gledhill, B.Sc., M.I.E.E., is product manager
for spectrum analysers with Marconi Instru-
ments.
SATELLITE - COMMUNICATIONS
& GENERAL PURPOSE
IFR A-7550 - TRULY REMARKABLE VALUE
The A-7550 Spectrum Analyser is the most advanced, low cost portable
spectrum analyser on the market today. Providing frequency coverage
from 100KHz to 1GHz. Its range of features are Iruly impressive, and yet
the A-7550 carries a remarkably low price lag
AVCOM PSA-35A FOR SATELLITE T.V.
The PSA-35A provides rapid alignment/testing of satellite equipment,
measures system performance and is an ideal trouble shooting tool.
MEGURO MSA-4901 - BUDGET PRICE
The MSA-4901 covers the 1-300MHz range and includes a T.V. scan
mot E HT ication and is ideal for bench or
use.
COST EFFECTIVE
RELIABILITY.
Fieldtech Heathrow
Fieldtech Heathrow Limited,
Huntavia House, 420 Bath Road,
Middlesex UB7 OLL England.
3 Telephone: 01-897 6446.
| Fieldtec Fieidtech | Telex: 23734 FLDTEC С. 4
i Telefax: (СИЛИ) 01-759 3740. Hamim,
ENTER 92 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD
SPECTRUM
ANALYSER
Full laboratory facilities making use of your
BBC microcomputer.
* Graphical and Numerical display of
spectra
* Easy to use menu-driven software
* Frequency and phase response
measurement using impulse techniques
* Optimised FFT routine gives high
speed and 80dB dynamic range
Runs on BBC B or Master: accepts users own
data on file or waveforms ма external
digitiser.
The Structured Software Spectrum Analyser
Il software costs £200 + VAT.
For FREE demonstration disc and full details,
write to:
Structured Software
15 Athelstan Close, Bromborough,
Wirral, Merseyside L62 2EX.
ENTER 37 ON REPLY CARD
FORTHEBES “N
SIMULATION 2; 6;
Designers are turning to ‘TROSE ENGINEERS' ойуу
by knowing what is going on while free to experimen:
delays and uncertainties of physical testing. Those EI^
which creates a net list removes the chores and errors `"
Ask us too for schematic layout software
ЕСА-2 is an example of one o! our circuit simulators
Features:
Г Transient analysis timing diagrams plotted
DC analysis
AC analysis -
Fourier analysis
Tolerancing —
Temperature C
supported
Bréakpoints and polynominals supported
lo* (ехр((у`а)/(п°к`ї}}— 1)
Resistors may have inductance etc, etc
Non-linear simulation —
Full diode model
Complex components —
Variants
func
may be mp осе, ed
Macro models 64
cuit, nc t on number or s
Probe ignals may be sampled or injected
anywher e
tive mode has
terruptr
owerful editing and
Batch: mc рае is
Dua! mode -
НЕЕ capacity
HigF Speed
Reference Manual
No risk trial —
ney Back tr tal,
75 + VAT, ECA-2
y with well-known
Low price
co
martr. ‘ame Simulators and is more рекети
than any other we know available on РС
THOSE ENGINEERS software which is available from £99 supports IBM PC's and
compatibles and the range of 3BC microcomputers, As engineers in electronic and
mechanical product and process design, we welcome enquiries for other requirements
THOSE ENGINEERS LTD, Sales: 106a Fortune Green Road, West
Hampstead, London NW6 105.
Te! 01-435 2771, Telex 8950511 mark for mailbox 23332001.
ENTER 80 ON REPLY CARD
365
OFF-THE-SHELF ANSWERS ТО
PROCESS CONTROL QUESTIONS
You don't have to re-invent the wheel when you want answers
to process control questions. That's because the solutions are
now available off-the-shelf — thanks to the Essex System
The remarkable f'exibility of this system erables you to tailor
modules exactly to your requirements. It's fast. It's versatile — the
powerful Chameleon controller can be programmed in a choice of
languages. It's also comprehensive since you can add opto-
isolator, analogue and video interfaces as well as a high-speed
EPROM programmer. In short, it's a complete system.
What's more, it's much less expensive than PLC solutions. All
the more reason then to put your process contro; questions to us
> next time
Lea O Essex Electronics Centre
| ?
ү ©-5'от\зеб modules: Wivenhoe Park, Colchester, Essex СО4 350. Tel: (0206) 865089
distributed by
RCS. MICROSYSTEMS LIMITED
141 Uxbridge Road, Hampton Hill, Middlesex TW121BL
Tel: 01-979 2204
a
Colour graphics module EPROM programmer
ENTER 47 ON REPLY CARD
RACKMOUNT CASES
Opto isolated I/O module
DM 105 - Pocket DVM from
A meter to literally suit all e e
pockets - including the one | |
that holds the wallet!
Its small size offers easy one hand operation, with large, clear,
wide-angle display.
But small does not mean delicate; the DM105 can withstand a 12
inch drop without damage, due to its glass epoxy PC boards,
shock mounted display and through thermoplastic case.
Overloads are handled with similar certainty; the resistance
range is protected up to 500 de, AC voltage range to 800V rms [| |] Ps 1 (134) height, 230m depth.......................
and DC voltage ranges up to I000V
&
unting Case with lift off Covers. Front Panel 10 guage. Brushed
Removeable Rear & Side Ра
n 3U Type the Subplate is
19" Self-Assembly Rack Mo
ur
Battery life is typically 2000 hours and a LO BATT indicator нне
signats 20" battery life remaining. Width Behind Front Panel 437m (All Types).
Ranges All prices include Postage & VAT Cheques, Postal Orders Payable to
J. D. R. Sheetmetal, 131 Grenfell Road,
Maidenhead, Berks SL6 1EX. Maidenhead 29450.
ENTER 53 ON REPLY CARD
SURPLUS/REDUNDANT STOCKS
ELECTRONIC COMPONENTS
We offer cash for your surplus components
including integrated circuits, transistors,
memories, microprocessers, I/C sockets,
connectors, caps etc, etc. Top prices paid,
collection no problem. Please contact us today
with your lists by telex, telephone or letter to:
MARLOW MARKETING
Mackenzie House, 221-241 Beckenham Road,
Beckenham, Kent BR3 4UF.
Telex: 946336 MICRO G. Tel: 01-676 0800
ALSO: COMPLETE FACTORY CLEARANCES UNDERTAKEN
DC Volts: 2V, 20V, 200V, ТКУ
AC Volts: 200V, 750V
Freq Range: 45Hz - 150Hz
DC Current: 2 mA, 20 mA,
200 mA, 2A
Resistance: 2K, 20K, 200K, 2M
DC Accuracy:
+ (0.5% reading + 2 digits)
Size: 130 x 75 x 28mm
Weight: 195g
Accessories: Battery, test leads
and manual
Price £24.75 inc VAT
Please add 70p for post and packing.
This is just one of our range of quality Analogue and Digital
multimeters.
Full details and specifications from:
Cirkit Distribution Ltd
Access Park Lane, Broxbourne, Herts ENIO ТМО ЖШ
Telephone (0992) 444111 Telex: 22478 VISA
TRADE ENQUIRIES WELCOME, 4
ENTER 87 ON REPLY CARD
ENTER 90 ON REPLY CARD
366 ELECTRONICS & WIRELESS WORLD
USED TEST & COMPUTER EQUIPMENT
PHONE 01-943 4477 FOR OUR LATEST STOCKLISTS
* SPECIAL OFFERS х ^^^
GARA! MICS PLOTTERS Ук
HEWLETT PACKARD
163CD LOGIC ANALYSER £5250
4953A PROTOCOL ANALYSER £5000
RACAL STORE 4D INSTRUMENTATION
TAPE RECORDER £1950
ATLANTIC RESEARCH
Нал 4600 PROTOCOL ANALYSER £3250 чаи. e
HEWLETT PACKARD — SPECTRUM ANALYSERS
141T SYSTEMS. DC TO 18GHz USING VARIOUS RF
GOULD CONFIGURATIONS. SYSTEM PRICES FROM £4500 OSCILLOSCOPES
TYPICAL SYSTEM AS ABOVE DEC
141T/8552B/8555A 18GHz SYSTEM £7500
AS ABOVE WITH PRE-SELECTOR £9000 LOGIC ANAWSERS
RACAL
SIGNAL GENERATORS WATANABE MC6601-6Z 6 PEN RECORDER £500
SOLARTRON INTEL DEVELOPMENT SYSTEMS SERIES 11, 111 AND IV CHART RECORDING
COMPUTER PERIPHERALS AVAILABLE — RING FOR THE CONFIGURATION YOU REQUIRE TEKTRONIX
TYPICAL SYSTEM: — 225B + 721 DRIVE AND
HEWLETT PACKARD p DEVELOPMENT
EXPANSION CHASSIS £490
A FEW EXAMPLES OF OUR
INTEL
CURRENT STOCK |
PDS100/110 Personal Dev.
862908 2- 18GHz Plug In System with ext. disc drive
86222B .01 -2.4GHz Plug In
MISCELLANEOUS
MARCONI
2019 1GHz AM/FM. Phase
DRANETZ
606-3 Mains Analyser
Locked. HPIB
626 + 3 Phase Plug In
>
>
QUME
OTA субе
SCIENTIFIC COMPUTERS HONEYWELL
APPLE PRNTERSPLOTTERS
р
f
P $
MAINS TEST EQUIPMENT VERCONI v
FLUKE FREQUENCY COUNTERS.
\ VDU TERMINALS \NTEL
“SPECTRUM ANALYSIS
IBM
LOGIC ANALYSERS AND
DIGITAL TEST
EQUIPMENT
TEKTRONIX
1240/D1/D2 Logic Analyser
834 Datacomms/Protocol
Analyser
HEWLETT PACKARD
1610A Logic State Analyser
16108 Logic State Analyser
1615A Logic State & Timing
7623A/7A18/7B53A 75MHZ £1200
Storage Dual Trace £1500
SPECTRUM ANALYSERS
MARCONI
TF2370 110MHz Spectrum
Analyser
£5500
£2950 £3950
£1500
£2950
PHILIPS
PM5390 1GHz AM/FM & Video
modulation. Phase Locked #1400
£1650
£2950 £2250
£6850 £3850
Analyser
1630G Logic State & Timing
Analyser
4951A/100 Portable Protoc:
Analyser
£2950
£7950
$2500
OSCILLOSCOPES
HITACHI
V209 20MHz Dual Trace
Mains/Battery
TEKTRONIX
2445 150МН2 4 Trace
2335 100MHz Dual Trace
2235 100MHz Dual Trace
Carston Electronics Ltd
01-943 4477
3 Park Road, Teddington, Middlesex TW11 OAF Telex: 938120
£275
£2450
£1250
£875
TF2371 200MHz $ресгит
Analyser
HEWLETT PACKARD
3561A FFT Dynamic Signal
Analyser
SOLARTRON
1200 Signal Processor. D
Channe
TEKTRONIX
7L12/7623A 0.1 MHz t
1800MHz £5000
HEWLETT PACKARD
8620C Sweeper Mainframe £1950
£8500
£7250
£8750
COMPUTERS AND
PERIPHERALS
HEWLETT PACKARD
86A
85A
9121D Drive
98265
7475А Plotter
98256 256K Memory Card
IBM
PC Twin Floppy 128K memory
mono display and keyboard #750
HEWLETT PACKARD
9870A Noise Figure Meter
346A Nolse Source
S.E. LABS
6300 UV Recorder
TEKTRONIX
576 Semiconductor curve
tracer
£5500
£550
£800
£7950
All prices exclude delivery and VAT
All items advertised are fully
working and sold with a guarantee
FULL SPECIFICATIONS OF
ABOVE EQUIPMENT
AVAILABLE ON REQUEST
We specialise in the purchase and sale of top quality under utilised equipment.
Every item sold by us has been thoroughly tested and calibrated to
manufacturer's original. specification. — and carries a full guarantee.
H your requirement is not listed above, please phone. We have considerably
more items in stock, plus a facility for locating rare equipment at short notice.
xv Carston:e!! Carstonbuy Carston:o!! Carstenbuy Carstonse!l! Carstonbuy
ENTER 89 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD
367
High-performance colour
graphics controller
External hardware is minimal using this new display
controller – all the timing and display manipulation is
ter publication recently justified its use
of a less than state-of-the-art computer-
produced front cover by explaining that had
the latest technology been used, no-one
would have recognized the cover as having
been computer-generated. The degrees of
resolution and hue now possible are quite
breath-taking — in cost as well as perform-
ance.
Engineers. need to strike a balance be-
tween cost and performance and in doing so
should consider the two other vital parts of
the system: the display device and its viewer.
Consider the term high-resolution colour
graphics. Graphics, of which the display of
recognized alphabets is just one form, is the
use of patterns to convey information. Col-
our is a useful adjunct to shape in increasing
|| t is a sign of the times that one сотри-
done using programmable registers.
JOHN ADAMS
the information conveyed. High resolution
speaks for itself — or does it? High resolution
of detailed shape, of colour, or of both.
Our current colour-display medium is the
three-gun shadow-mask cathode ray tube
where three electron guns are so positioned
with respect to a mask that their respective
electron beams can only strike certain non-
overlapping parts of a screen on the other
side of the mask from the guns. This screen
is intricately patterned with three different
phosphors such that only one type is struck
by the beam from one particular gun. One
phosphor glows red when struck, one green
and one blue. Early tubes had a mosaic
pattern consisting of triads of phosphor dots;
nowadays it is common for the screen to
consist of vertical stripes of phosphor.
Imagine a display of a series of finely
SPECIFICATIONS
Resolution
Up to 640 (horizontal) by 512 (vertical) dots.
Video memory 512Kbyte d-ram.
Video format
Sync. format
Display format
Object types
Colour/grey
scale
Pixel rate
368
Analogue RGBI (Insert) with 16 levels per channel, adjustable step size.
— 4-bit digital data representing 2 or 4-bit pel data.
8-bit multiplexed data representing 8-bit pel data.
— 4-bit data representing one of the colour levels generated by pel data, the
specific colour selected being software programmable.
Programmable video display window. Combined or separate syncs.
Programmable period, pulse width and interlace. Can be programmed as
master or slave for sync. purposes.
Up to 16 objects simultaneously displayed. Display window for each object can
be defined to one pel vertically and to one or two pels horizontally depending
on display mode. Objects may be split horizontally and can be scrolled
smoothly in either direction. A drawing priority determines which objects are
placed in front of others. Objects may have opaque or transparent back-
grounds.
- Bit-mapped objects may have two, four or eight bits of video memory
representing each pel depending on the colour range required. Attributes
available are flash (programmable rate and duty cycle) and background
transparency.
— Character objects may access up to four programmable character sets each
with character matrices up to 16 dots high and with widths of six, eight or
twelve dots, or with dot widths individually programmable in two-dot steps for
proportional text spacing. Basic attributes are flash and background trans-
parency (as for bit-mapped), one of two character sets and choice from four
colours for foreground and background. Additionally, in full-attribute mode,
character-set bank, foreground and background transparency, double width,
double height, conceal/reveal, colour invert, flash, underline and full colour
definition of both foreground and background are programmable on a
Character basis.
4 from 4096, 16 from 4096 or 256 from 256 colours or grey levels, the third
mode requiring external colour-generating hardware.
Upto 25MHz, depending on chip version.
spaced red and black vertical lines on such a
tube. Provided that the line pitch exceeds
that of the red phosphor stripes the display
will, from a certain distance, look quite
acceptable. When the pitch starts to
approach that of the stripes certain lines will
vanish as their screen positions will not
coincide with a red phosphor stripe. When
the pitches are equal you may see all of the
lines — or you may see none. It is this
phenomenon which limits detail resolution
to no less that the pitch of the phosphor
stripes.
In practice, it is unlikely that the sense of
vertical in terms of image creation will line
up exactly with the stripes, reducing resolu-
tion even further. This said, it is amazing
how much interpolation the brain can carry
out, particularly with a text display. With the
proviso that it is interpolation and not
certainty which is augmenting the image,
resolutions down to the stripe pitch are
worth experimenting with.
Standard, medium and high-resolution
tubes have stripe pitches of 0.6, 0.4 and
0.3mm respectively, although the terms
standard, medium and high-resolution are
often abused in literature describing colour
monitors. For a standard 14in tube with a
1096 border around the display area, this
corresponds to approximately 420 horizon-
tal phosphor elements. High resolution
tubes will naturally give better resolution
but at a cost, not just in the tube itself, but in
the entire display device from deflection
linearity and focussing to shielding from
external magnetic fields.
Monochrome monitors consist of a single
electron gun capable of striking any part of a
screen coated with a single phosphor. Detail
resolution is primarily limited by the focus-
sing ability of the display but monochrome
monitors typically provide resolution as
good as that of the high-resolution colour
display at an order of magnitude lower cost.
Some redress can be made for the loss of
colour by the use of varying luminosity.
No mention has yet been made of band-
width. Whichever system is chosen, it must
have a video bandwidth which is at least
equal to the pel clock rate.
There is then, a decision to be made
between resolution, the advantage of colour
over shading, and cost. Once these factors
are decided a choice of monitor must be
made. Since this design generates separate
sync. and video, a monitor with these attri-
ELECTRONICS & WIRELESS WORLD
These pencils are a simple image created using 4bit/pel in bit-mapped mode and а
combined system and video clock of 1OMHz.
butes is preferable. For colour this means a
monitor with ncB and separate sync. inputs.
For monochrome displays it is relatively easy
to combine the signals into composite video
but the display is usually better with separate
signals. Next, the right type of input re-
sponse should be chosen.
There are three types of response: non-
linear (often called 1.4.1.) inputs, non-linear
with an intensity control (xcBi) and ana-
logue. Non-linear systems are designed to be
driven digitally and thus only work at one
level of intensity for each of the three
primary colours. They are simple and are
common in low-cost systems. The всв! type
is an advance in that it has a fourth digital
input which steps display luminance to give
two intensities for each primary colour. This
maintains the on-off nature of the colour
inputs but it provides 16 rather than 8
colours. ІВМ colour systems use ncBi. The
design to be described can produce 4096
distinct colours by the use of analogue
signals, and so an analogue monitor should
be chosen.
Finally the line-scan frequency has to be
ELECTRONICS & WIRELESS WORLD
chosen. Normally line-scan frequency is
15.625kHz but this low frequency has the
disadvantage that at a 50Hz frame rate, only
about 290 displayable scan lines are drawn in
the frame period, limiting the vertical re
solution. To counter this, monitors with
line-scan frequencies as high as 60kHz can
now be obtained, giving a vertical resolution
of 1000 elements. The disadvantage of these
higher performance displays is that the
shorter line period leaves less time for pel
construction and thus demands a higher
performance from the driving circuits.
This design can produce a display of up to
512 lines, for which a line-scan frequency of
31kHz would be suitable for a 50Hz-refresh
display. At this line-scan frequency, each
line lasts approximately 33us. A scan line
comprising a maximum of 640 horizontal
picture elements, or pels, can be produced
by this system in 25.6us, which is well
within the line-scan period.
Note that it is dangerous to attempt to
operate a display at a line-scan frequency
different from that for which it was designed.
In order to minimize the drive power re-
quired most scanning systems are resonant
and any significant shift away from that
resonant point increases the load on the
driving elements, resulting in their prema-
ture failure.
Some systems offer extra vertical resolu
tion by using interlaced sync. and video
techniques. There is a minimum frame rate,
about 40Hz, below which persistence of
vision fails to fill the gap between one viewed
frame and the next. To avoid the appearance
of flicker and yet permit a slower frame rate
and thus more vertical scan lines, interlac-
ing makes use of an optical illusion to make a
real screen update frequency appear to be
twice what it actually is. It does this by
drawing all of the odd lines of the display,
then the even ones alternately — and it
works, provided that the odd and even
images are similar.
Similar odd and even images occur in
television but not in computer displays,
particularly of text. To get the greater detail
in a computer display odd and even parts of a
bigger video memory are accessed when
constructing the interlaced images and so
there is no guarantee that the odd part will
bear any relation to the even one. Such
displays flicker which is very wearing, but
worse, the flicker varies according to how
different the odd and even parts are; charac
ters E, F and s flicker far more than 1, ! and /.
An ideal colour display is a monitor
capable of operating with a range of line
frequencies such as the NEC JC-1401P3A
used for the photographs in these artiles.
This monitor's screen is based upon triads of
dots rather than stripes and its dot pitch is
0.31mm. Signal inputs can be t.t.!. rcs, 1.4.1.
RGB: Or analogue and scanning and synchro
nizing to any line-scan frequency in the
range 15.5-35kHz is automatic. This permits
non-flickering displays of up to 800 by 560
picture elements.
Having chosen a satisfactory display for
mat the criteria for the display controlle:
must be established. The number of compo-
nents should be minimal and the circuits
used should be off-the-shelf, yet provide the
flexibility normally associated with custom
design chips. A new integrated circuit with
these facilities is the Matra video display and
storage device (VSDD), the 82716. in its
simplest configuration this is the nearest
thing yet to a one-chip colour-graphics
system needing only the addition of a block
of dynamic memory to form a complete unit
with a microprocessor bus interface at one
end and a sync. and analogue or digital ncBi
interface at the other. Add to this the
virtually complete software programmabil
ity of the device and the ideal is approached.
Display controllers have a block of mem
ory storing bit patterns corresponding to the
patterns to be displayed. Early controllers
were little more than address generators,
scanning sequentially through the memory
and producing synchronizing pulses for
every display row and screen of memory
locations scanned. These pulses would syn-
chronize the display with accessing of data in
memory. Separate circuitry, if necessary,
would convert the bytes of data from the
memory into a bit stream for turning the
c.r.t. beam on and off.
369
60900900
cm ANIM Ee
9000000
000000009
ooooooooo
о
-—
PN
00000000
оооооооооооооооо
a =
PY ted ыту:
о
е
°
o
©
©
°
9
о
©
©
©
©
©
о
ге
©
о
©
ө
o
9
©
$
оооооооооооо
о 0000000
б 9096695020
00000000
A very popular device of this sort is the
6845. This device is fully programmable in
terms of memory size scanned, display ele-
ments per displayed line and displayed lines
per screen. As well as simple scanning of
memory the 6845 can be made to subdivide
its address bus into three sections so that the
codes being fetched from memory can be
translated into one of several possible bit
patterns depending upon the value held in
the middle addressing section. By this
means the memory codes may be interpreted
as characters, one character code generating
a sequence of complex but predefined bit
patterns stored ina character generator.
When predefined patterns such as the
Ascii character set are being used as de-
scribed above, memory requirement is quite
modest; a 2Kbyte ram and 2Kbyte character-
generator rom are adequate. When random
graphic plotting is required then there must
be at least a one-for-one relationship be-
tween bits in memory and picture elements
displayed. If one bit represents a pel then
that pel is either on or off, precluding the use
of colour or shade. Two bits make possibile
four colours and shades, four bits provide 16,
etc. A display of 432-by-288 pels with four
bits per pel requires almost 64Kbyte of
memory.
Two schools of thought have developed
over how to handle such large amounts of
memory. One technique, as exemplified in
the NEC7220, is to have a red ‘plane’ of
memory, a ‘green’ plane, a ‘blue’ plane and
perhaps an attribute ‘plane’, the latter in-
dicating whether the element is to flash, to
be bold, to be colour-inverted etc. With one
370
0000000900
Т оо00оооофё
1-1 ame A
poooooooQ
0900000000
———
о
oooooooo
АМ
> dootee
Ж?Р
A typical example of the application of the VSDD is my p.c.b. design software using a
display of 384 by 288 pels. There are four objects in use here. The main object is a two
bit-per-pel graphics object of 40Kbytes in size representing the two layout sides. As
horizontal definition is to more than 320 pels the high-resolution moce is in use, meaning
thatthe minimum horizontal scrollis two pels (see Object descriptor, Word 1).
Sothatthe drawing cursor can be placed over any pel in the layout window, two cursor
windows are defined. Both have the attribute of blink and of background transparency (so
thattheir window outlines do notobscure layout detail). bitthe actual cross in the window
is displaced one pel horizontally in one of the windows.
Software selects which cursor is used depending upon whether the horizontal cursor
coordinate is odd or even, so even though the layout scrolls in jumps of two pels, the
cursor may be made to move in steps of one. The fourth window has simple-character
attributes, is six pels-per-character wide and uses a character generator with a
six-by-nine dot aspect It reports program status to the user. Scrolling is instantaneous as
it only involves rewriting a table parameter, not а complete window. Likewise, switching
active layout side is immediate. With a processor running at full speed this image
occupies about 25% of the available construction time.
bit per plane, i.e. four bits per pel, eight
colours plus one attribute of 16 colours (if
the attribute is bold) can be achieved.
There is a lack of flexibility in this
approach as the number of planes will have
to match the highest number of bits-per-pel
that the system will be called on to provide,
wasting memory in other modes. Newer
Systems tend to use one block of memory as
continuous display data, each pel being
represented by n sequential bits which are
fetched and then translated into one of 2"
colour codes.
Neither technique appears to work well
when graphics and characters are mixed
since to easily fit characters into a
sequentially-organized graphics memory
the cell size for the character has to be
binarily related. In practice, this means an
eight-by-eight-dot matrix, resulting in the
squat characters seen in most lower-cost
colour systems. Interspersing a character
generator rom is also a technical problem.
Most systems solve this by not storing the
character code but expanding it into its
graphic equivalent before sending it to video
memory. This takes a lot ої time, although
not as long as is taken to work out which
character is actually at a screen location!
The VSDD solves this, and several other
problems, by having just one block of mem
ory and letting the host computer instruct
the VSDD as to which areas are to be used for
graphic display, which for character display
and which for character generator storage.
The device is highly programmable; almost
all of its own registers are stored in this
memory array. These processor-like regis-
ELECTRONICS & WIRELESS WORLD
Object i
descriptor
data
entry address
To pixel
processor
Fig. 1 For bit-mapped objects, an object-
descriptor table within the VSDD contains
the object's memory address, its width, and
the X coordinate of its left-hand side. In-
formation from this table forms a pointer to
pel data in memory. |
Object
data for
objecti
in d-ram
Fig.3 With bit-map objects, information from the object descriptor
table is fed directly into a buffer whereas with character-type Ry
objects, Ascil data from video memory is combined w th the slice
number and selected character-generator base address. This
combined information is used to extract and pass pel data from
the character generator to the video buffer.
Fig.2 Information on character-type objects is held ina similar way Character
to that for bit-map objects but used differently. height
Object data
И
|
Character Base Character
generator address generator
0 +256n 1
Slice
n
—— Slice
information
256 words
one for
each Ascu
code
Character
generator
selection
descriptor
data
Char ?
Char 2
Char 1
FAD=0
T L
|
Attributes 0
Object i
descriptor
Object-
data
entry
address
Object 1
Line n«1
generator
Address
computing
unit
Object ı
Line n-1
Ч m
ELECTRONICS & WIRELESS WORLD
ters indicate the memory positions of up to
16 ‘objects’ and up to four character gener-
ators each containing up to 256 characters.
Timing parameters, object descriptor tables,
a colour look-up table and an access table are
also contained in these registers.
An object descriptor contains the 'O'
address of the object in the video memory.
the object width and the X coordinate of the
left-hand side of the object. When describing
a bit-mapped object, it also includes the
number of bits per pel (2, 4 or 8), the quarter
of the colour look-up table to be used when
using two bits-per-pel and the object blink
and transparency attributes. When describ-
ing a character object, it also includes the
starting slice of character dot row (to permit
smooth scrolling), the character width (6, 8,
12, 16 dots or proportional spacing), charac-
ter generator to be used, colour and mode.
In full attribute mode, where three bytes
instead of one are used to store information
about each character, extra attributes are
foreground and background colours, char-
acter height, character width, underlining
blinking, colour inversion, conceal/reveal
371
(as in Teletext), alternate character set and
transparency.
Figure 1 shows how parameters from the
object descriptor table are used to form a
pointer to the pel data in video memory.
Character objects use a similar process as
shown in Fig. 2. In the former case, informa-
tion accessed is fed directly into a video
buffer. For character objects the Ascii value
drawn from the video memory is combined
with the slice number and selected
character-generator base address; pel data is
then extracted and passed from the charac-
ter generator to the video buffer, Fig. 3.
The access table is a general map of the
screen consisting of as many words as there
are to be displayed lines. Within each word.
each of the 16 bits can be programmed to
turn the display of an object on or off; a set
bit results in toggling of the current display
status for that object.
A pointer to the currently-displaved line is
used to get the word into the VSDD. From
there the word can be combined with the
base address of the object descriptor table to
form a pointer to the specific object's de-
scriptors, Fig. 4. By modifying the access
table and the object's X coordinate, objects
may be shifted around the screen or display-
ed in sections down the screen as required —
in tune with the window concept.
The objects have a drawing hierarchy so
objects with a high priority overwrite those
with a low priority when they are both
mapped to appear on the same part of the
display screen. This priority can be easily
changed to bring objects to the foreground.
It is also possible to define one of an object's
coloursas 'transparent' so that a background
object can still be seen in the background.
Once programmed, the VSDD takes full
responsibility for the construction of display
of up to 640-by-512 pels as well as arbitrating
requests for video-memory access from the
host system. There is a limit to how complex
an image can be formed which is a function
of processor clock speed, display-line period,
number of objects, object type (character or
graphic) and number of host requests. The
VSDD can be programmed to only allow a
certain number of host high-priority access
per line-scan and has a 'construction-time
overflow' output which can be used to signal
to the host system that the VSDD is getting
into difficulties.
For highly complex systems it is possible
to literally piggyback one VSDD and its
memory onto another and program them to
construct each alternate line, improving
potential performance several-fold. Using
one VSDD, maximum processor speed, two
bits per pel, eight objects and a 432-by-288-
line display, approximately 2200 pels can be
constructed on a line. This could be five
full-size objects and three 8-pel ones (cur-
sors for example).
Complexity depends on the image type
since the VSDD is designed to make use of
4-гат page mode. Using page mode, а
number of adjacent memory loctions — 512
for a 256Kbit device — can be accessed more
quickly than using normal d-ram accesses:
512 adjacent locations represent 4096 se-
quential pels. This mode can be used with
bit-mapped images since the pel data is
372
Register
segment
R8 Access base
ют оет |
Video memory
Object descriptor
table entry address
Fig.4 Addressing access and object descriptor tables. By modifying the access table
and the object's X coordinate, objects may be shifted around the screen or displayed т
sections down the screen.
пез Memory mapping. To the host, VSDD looks
like two memory windows — a fixed one for
registers and a variable one for data. Immediately
after reset, the register window appears at 400 to
41F in the host memory тар.
Data
window
IFFFF 4¢
Relocatable
data »
window
base
Relocatable
register
window
base Register window
00000
indeed sequential in memory but it does not
work with character displays since the d-ram
is constantly switching between character
and character-generator accesses. [n prac-
tice, this limits the construction capability
to scan lines containing no more than about
110 plain or 96 full-attribute characters.
To the host the VSDD looks like two
512K bytes
60000 16
SFFF* 16
Relocatable
data
segment
base
40000 16
3FFFF 16
Register segment
Fixed = 00000
memory windows, the VSDD acting as the
access arbitrator. The register window is toa
32-byte segment of the video memory which
the VSDD uses to store 16 control words.
These control words define the type and size
of memory being used for display storage,
the locations of the various tables and
character generators in the memory, system
ELECTRONICS & WIRELESS WORLD
parameters such as character dot height,
interlace, priority access count etc., size and
mapping of the video memory window and
the mapping of the register segment.
Size of the data window varies. Im-
mediately after a hardware reset the register
window appears at addresses 40015 to 416),
in the host memory map. This is the only
unprogrammable feature of the VSDD;
where the data window appears in a 17-bit
address range of the host memory map,
where it appears in the video memory and
size of the data window are all pro-
grammable. This mapping is process is
illustrated in Fig. 5.
As access to the video memory has to be
arbitrated the host may not get immediate
access to it. Two techniques are provided to
cope with this non-random access. An
active-high rEapy, active-low wait signal, ко,
is provided for directly driving processors
which can extend bus cycles by testing the
state of a Rbv or warr input pin. For those that
do not, and must thus execute fixed-length
bus transactions, it is possible to program
the VSDD to work in pipeline mode. In this
mode the current read/write cycle reads or
SPECIAL OFFER
A limited number of VSDD display controllers is being made available to EWW readers at a special
fully-inclusive price of £39.86 as opposed to the normal one-off price around £64.
Theses 12MHz p.l.c.c. devices, with the full part number S82716.3, can be obtained by sending a
cheque made payable to Thame Components to Jacqueline Cole, Thame Components Ltd, Thame
Park Road, Thame, Oxon OX9 3XD. The G82716.3 па pin-grid array package is also available at
£45.80 fully inclusive. This offer is limited to one device per reader.
writes to the video memory address used in
the previous cycle, the current address being
stored and then used during the next cycle.
What actually happens in the cycle before
the current one is that, as soon as is possible.
the VSDD reads that location and stores the
value. If the current cycle is a read then this
data is immediately available to the host. If it
is a write cycle then the input data is
immediately stored by the VSDD and written
to video memory as soon as possible. This is
followed by a read-and-store of the data at
the address used in the current cycle, ready
forthe next one.
It would, of course, still be possible to
overrun the VSDD in this mode. Leaving
twenty VSDD video system clock cycles
between one pipeline access and the next will
make sure that this does not occur. One
bonus of not using the кох signal is that it can
be programmed to act as a free-access
indicator. This signal is active when the
VSDD is idling, i.e. it has finished preparing
the next scan line of data, and thus tells the
precessor that it can have full access to the
video memory.
Programming and hardware implementa-
tion of the VSDD graphics controller are
subjects of the next article. А complete
circuit interfacing to 64180 (Z80-like) sig-
nals at one end and an ксв monitor at the
other will be given, as will p.c.b. details.
Increased resolution
from an a-to-d converter
‘Dither’ and an averaging process provide
ight-bit А to D converters are com-
E mon and very convenient to use with
eight-bit data buses. However, there
are times when it is either beneficial or
necessary to achieve a higher resolution
than can be given directly from the conver-
ter. The methods described below, in some
circumstances, enable a higher bit resolu-
tion to be achieved than is directly readable
from the converter.
METHOD -
To understand how the method works, it is
first necessary to appreciate what is meant
by a converter with a particular number of
bits, and what are the implications.
Ап analogue-to-digital converter, as the
ELECTRONICS & WIRELESS WORLD
interpolation between steps
R. A. BECK
name implies, converts an analogue signal
(which therefore has an infinite number of
discrete levels) to a digital number within a
particular range: it has a quantizing effect.
The number of different levels which can be
recognized by the a-to-d converter depends
on the type of the device, but for the sake of
example, assume that it is an eight-bit a-to-d
converter. There are therefore, 2° discrete
levels, which is 256. If the a-to-d converter
digitizes voltages in the range 0 to 2.56 volts,
each quantized step is 2.56/256 = 10т\.
This means that in digitizing a direct volt-
age. a different number is produced from the
converter for every 10mV change in level.
One can imagine the converter as being a
256-rung step-ladder lying down on the
ground: each rung of the ladder represents а
quantization level change. The voltage that
the ‘ladder’ is trying to quantize can be
imagined as stick being placed between the
rungs of the ladder. If the stick is exactly on a
rung, the number given from the converter
at successive conversions will rapidly change
back and forth between the two levels. If this
happens one knows exactly where the stick is
and therefore exactly what the voltage is. If
the stick now moves between a pair of rungs,
a single, constant number will be given out
frem the a-to-d converter representing be-
tween which pair rungs the stick lies. The
voltage, at an instant, cannot be read more
accurately than the width of the rungs, and
in this case, it is 10mV.
If one assumes that the rungs are equally
spaced, one can read where the stick is
within a pair of rungs provided one is able to
condition the stick movement. The method
373
Actual
temperature
Measured
(no added wave)
Measured
(added wave) Actual
temperature
.000
180
.200
. 390
400
. 50е
. 600
.70е
- 880
900
. 900
100
. 200
. 398
400
. 508
600
-700
. 800
909
880
Measured
(no noise)
‚118
«118
‚118
‚118
. 549
‚549
. 549
-549
-980
.98e
.98e
. 980
.412
.412
.412
.412
.412
„843
.843
.843
.843
Error Measured
(noise)
. 003
.118
.205
310
811
498
575
‚731
. 809
913
‚984
085
„206
.335
.412
483
577
698
.823
.88e
. 978
s
3
=
«128
.118
‚118
. 118
‚549
‚549
-549
549
. 988
.98e
. 988
-980
+412
412
.412
.412
-412
„843
- 843
843
.883
Юю Р р ә рә | р > ә э ү» © @ © © © © © © © ©
БОШУ *
. 00h -0. 00h
104 0.004
.199 -0.001
306 . 806
401 . 01
592 .ве2
.6е3 . 083
.697 - 883
. 792 - 098
. 900 . 000
.007 .007
.095 «885
.203 . 003
.297 . 003
. 405 .005
.A99 . 001
. 594 . 006
„792 . 002
.796 004
.897 . еөз
. 2005 . 005
NIIT
100
„200
300
. 800
- 508
600
- 788
. 800
. 900
. 888
100
. 200
. 300
Ir
. 500
600
708
. 800
. 900
. 000
(EEEE о оооосоо
оооооо
менне р
РАИ
Ю Р у» һә їз | рыр > > © © © © © Ф@ © © © о
oe H $ . h Ы *
Seeoeee00008
NNONF POOR PH
© шю о Ум 2 ом ош
РР м ъ Р Pea ооо ооо
М Б
ооооооооооооооооооооо
Р юк р мї у» > > © © © © © © © жо
РЕР к Р к Р PHSB © ф © © © ч жоо
e
e.
e
e.
e
e
e.
е
e
e
1
1.
1
1
1.
1
1.
1
1
1
2
is to move the stick randomly over a number
of rungs, making sure not to permanently
pull the stick off to one side while one is
doing so. Then, a number of instantaneous
readings are taken of the stick's position and
all the readings are averaged. This reduces
the effect of the quantization. The effect is
similar to averaging the numbers 5 and 6,
5+6/2=5.5. Both the numbers are integers,
but the averaged result is between the two.
Provided the stick moves over at least two
rungs, and a sufficient number of samples
are averaged, quite an accurate result can be
achieved. In electrical terms, noise is added
to the signal to be measured and number of
readings are taken to suit the accuracy of the
result required. Noise is, of course, noisy, so
more readings must be averaged to achieve
an accurate result than one immediately
thinks; averaging about 100 samples is
usually adequate. This method can also work
for a.c. signals. The proviso is that the
trigger must be taken from the ‘clean’
source. The amount of noise which must be
added has to be controlled quite closely: if
the amplitude is not sufficiently great, the
method will not work, and if it is too large,
one can get worse readings than not bother-
ing with this method at all.
ALTERNATIVE METHOD
Adding noise to the signal prevents aliasing
caused by the sampling frequency of the
a-to-d converter and the a.c. component of
the input signal. Excellent results can be
obtained with fewer samples by using an
alternative method, provided the rela-
tionship between the two frequencies can be
assured.
Noise, by its very nature, is difficult to
generate in a controlled manner. Wave-
forms. on the other hand, are easy to
generate and control, but cause aliasing
when they are added to a direct voltage
which the converter tries to measure. The
same result of reducing the quantization
effect can be achieved by adding a controlled
waveform to a direct voltage, rather than
adding noise, provided the relationship be-
tween the sampling frequency of the a-to-d
converter and the frequency of the superim-
posed waveform in controlled.
374
Part of computer simulation of effect on
reading of noise added to d.c. (a) and of
triangular wave (b), when a-to-d converter
used in temperature measurement. Col.
umn 5 in (b) is the difference between the
start of conversion and the start of the
randomly asynchronous triangular wave.
The solution is to run the superimposed
waveform, which most conveniently could
be a triangular wave, at a frequency which
enables a high enough number of samples
over one period of the added waveform so
that aliasing does not occur, and for the
samples to be averaged over an integral
number of superimposed waveform periods.
An example of a configuration which
worked very well and which was im-
plemented in a temperature measuring cir-
cuit, was to measure temperature to an
accuracy better than 0.1 degrees over a
temperature range of —40 to +70 degrees
Centigrade, using an eight-bit a-to-d conver-
ter. The resolution obtained by using the
converter to give a single number from
which the temperature would be calculated
would be (70--40)/256 20.43 degrees.
To gain greater resolution, a triangular
wave was added to the direct voltage repre-
senting the temperature. The period was set
to 1/64 of the a-to-d converter period, so that
for each complete wavelength of the triangu-
lar waveform, 64 samples were taken and
averaged. Where on the triangular waveform
the a-to-d converter started to take readings
was of no consequence due to the readings
being averaged over one complete wave-
form, and the waveform and sampling fre-
quencies were not required to be phase
locked.
Part of a computer simulation is shown
for the temperature range 0 to 10 degrees
Centigrade, in 0.1 degree steps. The tabu-
lated results show the greatest error to be
0.013 degrees, a theoretical accuracy of
seven times better than that required of the
circuit.
The peak to peak amplitude of the wave-
form used here was the equivalent of 10
degrees or 23 quantization levels, but is by
no means critical. It should be greater than
five quantization levels and less than 20. The
a-to-d converter was set to sample at a period
of 10 ms, and the triangular waveform a
period of 640 ms. These frequencies were
chosen as they were convenient to generate
from the frequencies available on the board.
ACCURACIES
The above discussion assumes that each
quantization level is precisely equal to every
other, and this is clearly not going to be the
case. In general, the accuracy to which the
quantization levels are manufactured reflect
the bit accuracy of the a-to-d converter; i.e.
the range of accuracies usually available is in
the range 1/4 to 1 bit or quantization level.
However, one should bear in mind that the
larger the amplitude of the superimposed
waveform, the smaller the absolute error is
likely to be, as the averaging occurs over a
greater number of quantization levels.
In the example, the requirement was not
so much for absolute accuracy, as an accu-
rate reading of temperature was not re-
quired, but for the detection of relatively
small temperature changes, which might be
in the range 0.1 to 20 degrees. This techni-
que provided a satisfactory solution to what
was initially thought an insoluble problem.
Since the a-to-d converter hardware had
already been designed and it was not then
possible to change the type of converter.
PENALTIES
The major penalty for this method is likely to
be time. To achieve the required accuracy in
the example, 64 samples must be taken for
averaging. The whole cycle time for each
successive reading increases from 10 ms to
640 ms (the time taken to average the
readings can be carried out in a very short
time relative to the cycle time). However, as
the temperature changes minutely within
each 640 ms cycle time, the time penalty is of
no consequence.
Equally, in other instances where a num-
ber of conversions can be averaged without
impairment to the operation of the system,
the method can achieve very satisfactory
results.
А little extra hardware is required, along
with greater program length and complex-
ity. but as usual, one cannot get something
for nothing!
ELECTRONICS & WIRELESS WORLD
P
LOW COST DESIGN TOOLS.
FOR ENGINEERS
At fas Тре Complete sofutión:to computer aided Lirtit dèsighosthe-BM PC ht a sén ible price. |
SCHEMA £499. PROTEL £799
Design professiortal-q salty circuitifagrams rigat ort Fast establishiridstse-f.as the waris leading Т СЫ!
e screen-with this удеу Sed schematic-drawigg- о ali Board design раскаде, PROTEL-MÉB
ckage. e s you tmereate prafessióifalmtulti-laer PQ3s
extensive schegfüte symbol libegry frem-conceptto-camera-ready artwork.
3.20от yels @ up ta sixirazk Ву
@ bill of mátérials @ variety Of track. widths aneipad sizes
@ wire andnethists 6 roulli-coloured.check flots
® printand plothard copy, ө Nexirilisup»ort
@ Gerber photoplottercompatibain
Who-buye-coftwase-mithout-ovaluating iifirst? Try out SCHEMA Bnd BROTEL en-xoUr Qwn.PO-with'sur well-
Hocumente@d_evaluaticn’disks.— £25éach. Visa/Access- welcome
Schema: Enter 45:6n Reply Card | Protel; Enter46 on Réply Card
Engiseeririg Solutigns-Limited, King: ;
i +94 Street, Maidenhead, ‚ SL6
= beaa л T
Keienhona 0628) 36052. Теех84962 -F
COUNTER
TIMERS
PFM200A £75.50 + VAT
20Hz — 200MHz in 2 ranges, 4 gate times. 10mV sensitivity
8-digit LED display. Battery/mains operation
TF200 £175 + VAT
10Hz – 200MHz in 2 ranges, 5 gate times. Frequency, period,
period average, totalize. 10mV sensitivity. 8-digit 0.5" LCD.
200 hour battery life
TF600 £135.50 -- VAT
5Hz - 600MHz in 3 ranges, 3 gate times. 10mV sensitivity. 8-digit
0.5" LED display Battery/mains; complete with adaptor/charger
TF1000 £495 + VAT
DC - 100MHz on both channels, 6 gate times. Frequency
period, period average, time interval, time interval average.
frequency ratio and totalise. 20mV sensitivity. HF filter,
attenuator, trigger controls, trigger hold-off. 8-digit 0.6" LED
display. Mains operation
TF1100 £595 + VAT
As for TF1000 but with 70MHz to 1GHz prescaler (frequency
only); 10mV sensitivity
TP600 £45 + VAT
+ 10 prescaler, 40MHz – 600MHz. 10mv sensitivity
TP1000 £75 + VAT
— o 10 prescaler, 100MHz — 1GHz. 10mV sensitivity
Thandar Electronics Limitec
Ý v London Road. St. Ives, Huntingdon
—— { | [ө] fi a f Cambridgeshire PE17 4HJ, England
Telephone (0480) 64646 Telex 32250 Test
ELECTRONICS LIMITED THE LOGICAL CHOICE
ENTER 9 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD 375
RALFE - ELECTRONICS
10 CHAPEL STREET, LONDON, NW1
MARCONI TF2371 200MHz TEL: 01-723 8753/724 8074 20078 Rules овозот
SPECTRUM ANALYSER i 8555А Spectrum analyser unit
to 40GHz
400F Voltmeter 1004 V -300V 4MHz
7418 AC/DC Ditt V Meter/DC Standard
7386R Catibrator
4800A Vector impedance meter
11602B Transistor fixture for 8745A
11600B As above
8004 pulse generator
182T/8558B spectrum analyser
7045A XY Piotter Opt 001 (Time-base)
355E Programmable anenuator 1GHz 0- 12db
30Hz-200MHz frequency range 0196 & SHz resolution 100db displayed 355F As above but 0- 120db in 10db steps
' on & er. MINT n with " н "
р MNT conn и) уер EXTENDED WARRANTY SCHEME А Dial Mme
15 now available for all tems of equipment costing £1000 or more" 8701A/2A/3A Microwave link analyser
For an additional 10% of purchase price an offer a comprehensi 431C 478A Micro: '
MARCONI 2019 SIGNAL GENERATORS pans and labour wavvanty for a ful year. and we sti guarane c | | шо nente power meler
under-cut our closest competitor! Certificates of calibration to national Б
о
Standards traceability ate available upon request for certain items
Please let us quote you
Sypibesized signal generators BOKkHz-1040MHz As new condition fined with
Gi 600
IB option “Different rates available on cheaper equipmen
ос variants also available p.o.a. Limited quantity only available FROM 110MHz SPECTRUM ANALYSER
141$ Storage main-frame/85524 | F. unlv8553.
110Мн2 R.F, Unit £2500
8004 Pulse generator
NETWORK ANALYSER
e | Ty
TF2006 AM/FM Signal generator 10- 1000MHz
TF1313 14% RCL Bridge
TF2011 VHF FM Signal Generator 130- 180MHz
TF2604 Electronic mulhi-meter
TF893A Audio power meter
TF2612 MF Attenuator 0- 111db 0 1db steps
TF1020A 100W 250MHz power meter BPL Wheatstone comparator bridge With types 8412A Phase-Magnitude and 84:4A Polar display units. 110MHz
TF2301 Programmable Modulation meter BRUEL & KJAER 1402 Random noise gen Recent calibratior £2500
TF 2430 Frequency counter BOMHz è DYMAR modulation meter AM/FM
TF163S Attenuator 1GHz DYMAR 781/S RF power meter 1-30W
TF2304 А " z GPW 7620 Telegraph & Data generator
кта (Tet AVO VCM163 Valve charactarisii meter
TF1245 O-Meter with oscillator 1246 о! 7.
RACAL 9301 RF Voltmeter 1.5GHz
и 550 | RACAL a301 RF Votmeter scr * HP141T SPECTRUM ANALYSER
2019 signal generator RADFORD 1002 Low distortion oscillator
TF 2008 signal generator STODDART Receiver RFI 375-1000МН2 SYSTEM to 40GHz *
TF2170 sync box 3 RADIOMETER FRA3 А.Р. Wave analyser
2833 digital ine monitor AVERY Electronic scales 1766 25kgs
2437 100MHz counter mer TEKTRONIX 191 Signal generator
TF2807A PCM multiplex tester PHILIPS PMOASAD Voli
LIPS PM2454B Volimeter
ПРЕТЕРА атре FLUKE 871A Ditterential Voltmeter
2829 юпа! analyser
TF2015 senes sig gens from
TF2016A & 2173 ALL OUR EQUIPMENT 1$ SOLO IN EXCELLENT, FULLY
TF995A'S AM/FM signal generators FUNCTIONAL CONDITION AND GUARANTEEO FOR 90 DAYS
ТЕ1245А/1 with 1246 & 1247 Q-Meter MAIL ORDERS AND EXPORT ENQUIRIES WELCOMED. PLEASE
TF2300S modulabon meter TELEPHONE FOR CARRIAGE QUOTE. ALL INSTRUMENTS ARE
TF2330 wave analyser AVAILABLE EX-STOCK AS AT COPY DATE. GOOD QUALITY
TF2092C noise receiver TEST EQUIPMENT ALWAYS WANTED FOR STOCK PRICES SYSTEM Compnses of type 141T Storage main-trame, 85528 Е plug-in unit
TF2910/4 non-linear distortion analyser QUOTED ARE SUBJECT TO ADDITIONAL VAT and 8555A 10MHz-18GHz (40GHz with external mners) А F. plug-in £7500
TF1263S 1GHz attenuator Excellent throughout, calibration certified
ENTER 40 ON REPLY CARD
ІЕЕЕ488
TECHNOLOGY THAT |
HITS THE MARK
€ Interface system for IBM-PC/XT/AT/IC and all compatible
equipment
€ Interface system for PHILIPS PC : YES
® HP control commands (ENTER, CLEAR... etc.) implemented
® SRQ interrupt software implemented
* DMA and INTERRUPT activated by simple commands
® 64 kByte memory management for processing large
volumes of data
€ integrated control interpreter, HELP screen and HELP
functions in decoded text
€ Support for BASIC, BASIC (compiled), (TURBO-)PASCAL,
MODULA 2, FORTRAN, C and ASSEMBLER
€ Software and manual available in English, French and
German
LOOK AHEAD!
WITH MONOLITH MAGNETIC TAPE HEADS
DOES YOUR VCR GIVE WASHED OUT NOISY
PICTURES - ITS PROBABLY IN NEED OF A NEW
HEAD - FAST FROM OUR EX-STOCK DELIVERIES.
SAVE £€£'s ON REPAIR CHARGES.
Our replacement video heads
fit most models of VHS or
Betamax VCR's. Following our
replacement guide and with a
practical ability, you can do the
whole job in your own home
with our head replacement kit.
(Kit does not include video hea
TELEPHONE US NOW FOR INFORMATION OF THE
REPLACEMENT HEAD FOR YOUR VIDEO RECORDER
CATALOGUE: For our full Catalogue of Replacement
Video and Audio Cassette/Reel to Reel Heads, Motors.
Mechanisms, etc. Please forward 50p p&p.
prot a TELETEX: -2627 2214237 gizkin THE MONOLITH ELECTRONICS CO.LTD.
TELEFAX: -49 2214972078 5-7 Church Street, Crewkerne, Somerset TA18 7 HR, England
- NM. Telephone: Crewkerne (0460) 74321 Telex 46306 MONLTHG
ENTER 23 ON REPLY CARD
VMC-02 KIT ONLY £19.95 inc. МАТ. + £2.50 p&p
d)
INES GmbH, Neuenhéófer Allee 45,
5000 Köln 41, West-Germany
PHONE: -49 221438659
TELEX: -2627 17 2214237 gizkin
ШИНЫ ПГ Нм | |
TTTTTTTTTEERRRRTHTRITITITITIT
ENTER 72 ON REPLY CARD
376 ELECTRONICS & WIRELESS WORLD
Franco-German
d.b.s.
If Arianespace manages to keep
to its announced programme of
launches, both France and Ger-
many will have direct broadcast-
ing satellites in orbit by the end
of this year. Germany’s TV-Sat 1
and France's TDF-1 are due to be
launched on Ariane 2 rockets and
propelled to a slot in the geosta-
tionary orbit at 19°W.
These two d.b.s. spacecraft are
very similar, having been built
more or less simultaneously by a
Franco-German manufacturing
consortium. Called Euro-
satellite, it was formed by Aeros-
patiale and Alcatel- Thomson
Espace of France together with
MBB-ERNO, AEG-Telefunken
and ANT of W. Germany. Belgian
and Swedish firms are also in-
volved. Overall management is
by a joint committee represent-
ing the French Space Agency
(CNES), Telediffusion de France
(TDF), the German aerospace
R&D institute (DFVLR) and the
German Bundespost. The manu-
facturing programme is also pro-
viding a common, spare satellite.
The photo shows TDF-1 being
prepared for tests in an Aerospa-
tiale clean room at Cannes,
France. The central body mea-
sures 2.4m х 1.6m x 2.3m
while the total height is 6.5m.
Overall weight is 2075 kg. When
the folded solar panels are fully
extended the spacecraft is 19m
wide from tip to tip. Power sup-
plied by these solar panels is
3.2kW (at the end of the satel-
lite’s 7-year lifetime).
Like other satellites with this
type of structure, the TDF-1 and
TV-Sat 1 are stabilized in three
axes. Àn antenna position con-
trol system cancels the effect of
small angular perturbations in
the spacecraft’s orientation, so
that the 12-GHz transmitting
antenna dish is always kept cor-
rectly pointed (to an accuracy of
0.1°). Two other antennas are
mounted on the structure: a dish
for receiving the uplink signals
on 17.8 GHz and a telemetry and
command antenna.
Each satellite provides four
d.b.s. channels. In each channel
the r.f. output power from the
transponder travelling-wave
tube is 230W. When the two
satellites are in operation they
are expected to broadcast with an
e.i.r.p. of 63.5 dBW. Their cover-
TDF- 1 satellite for d.b.s.at гузаре s factory, < Cannes.
age areas, or ‘footprints’, are of
course slightly different for the
two countries but at the outer
edge of these footprints (includ-
ing the UK) the power flux densi-
ty available to receivers will be
about — 111 dBW/m?. More cen-
trally the value will be about —
103 dBW/m?. For readers who
prefer to think in terms of
microvolts-per-metre field
strength contours the last-
mentioned figure corresponds to
a field strength of 140 д\/т.
Domestic receiving dishes of
about 70cm diameter are ex-
pected to be adequate. With this
coverage the potential audience
for the d.b.s. services is esti-
mated to be 260 million Euro-
peans.
А common
satnav receiver?
А small satellite navigation re-
ceiver about the size of a
cigarette packet, costing less
than £700 and capable of giving
position-fixes in three dimen-
sions to an accuracy of a few
centimetres is a practical possi-
bility. Such a receiver could be
produced in large quantities to a
world standardized design for
use with both the American and
ELECTRONICS & WIRELESS WORLD
the Russian satellite navigation
systems now moving tawards
completion.
This is the opinion of Dr P.
Daly of Leeds University. He
offered it to an IEE audience in
London in the course of deliver-
ing the 22nd Appleton Lecture
on "Satellite navigation systems
developed by the super-powers."
Dr Daly's opinion is obviously a
very well-informed one, as he
and his colleagues and students
in the Electrical and Electronic
Engineering Department have
been studying the American and
Russian systems intensively for
many years and developing their
own receivers to work with
them.
His lecture was a survey of two
pairs of satnav systems. The first
pair was the USA's Transit and
the USSR's Cicada systems,
which are very similar and both
fully operational. The second
pair was the USA's Navstar (also
called Global Positioning Sys-
tem) and the USSR's GLONASS
(Global Navigation Satellites
System), which again are very
similar to each other but in this
case are both in a pre-operational
state. Their similarities can be
seen as part of the technological
rivalry between the super-
powers.
Transit and Cicada, described
in this journal some years ago,
rely on integrated Doppler and
work on v.h.f. at 150 MHz. It was
because of their operational per-
formance limitations that
Navstar and GLONASS were
developed, using the different
basic principle of measuring sig-
nal transit times to calculate
range and working on u.h.f. at
about 1.2 and 1.5 GHz (L band).
These new systems are better
because they are world-wide, all-
weather and continuous. As an
illustration of relative perform-
ance, Dr Daly mentioned that
with Navstar the Leeds resear-
chers had been able to make 125
position fixes in less than an
hour, whereas the same number
of fixes using Transit would take
about a week or more. Furth-
ermore, with Transit the velocity
ofthe travelling receiver — say on
a ship — must be accurately
known.
Whereas Transit and Cicada
use satellites in low polar orbits
(at about 1000km altitude) with
roughly 134-hour periods, the
newer American and Russian
systems have satellites about
half-way out to the geostationary
orbit with approximately 12-
hour periods. The GLONASS
orbits are about 1000km below
those of Navstar. Both of these
systems will be using three orbit-
al planes separated by 120°,
though at present only two of
these planes are occupied by
satellites. Navstar was intended
to have a total of 18 satellites in
full operation by the end of 1988.
But the Challenger shuttle disas-
ter has put back this programme
and at present there are six or
seven operational spacecraft.
GLONASS is in a similar pre-
operational phase with eight
satellites launched — which is
done three at a time, inciden-
tally.
Dr Daly pointed out that 17
complete orbits of GLONASS
spacecraft take exactly the same
time as 16 orbits of a Navstar
spacecraft. So after 17 GLONASS
orbits the two systems come
back into precisely the same rela-
tive positions as they had at the
beginning. He felt that this syn-
chronization, along with the
many other similarities, was a
useful characteristic that would
help in providing a common
receiver design for civil applica-
tions throughout the world.
The block diagram shows the
key sections of a Navstar GPS
377
Built-in test e
Spread-spectrum signal
[at 10-7MHz if.]
Pseudo range
measurement
р.г.п. code
generator
uipment
prn. code Carrier
tracking loop tracking
(correlation) loop
Local Data clock
Data
recovery
Control and
navigation
2808
microprocessor
plus
i/o devices
Printer
Simplified schematic showing key parts of Leeds University’s automatic GPS satellite navigation receiver.
automatic receiver developed at
Leeds. It receives the 1575.42-
MHz transmissions intended for
civil users and is suitable for
navigation in slow-moving
vehicles. To understand how it
works some readers may need a
brief outline of the Navstar sys-
tem. The basic principle is that
the user can fix his position ina
set of X, Y, Z co-ordinates cen-
tred on the Earth. To provide this
fix, his receiver measures dis-
tances from itself to transmitters
in satellites of known (though
changing) positions. The dis-
tances are computed from the
times taken by pulses to travel (at
velocity c) from transmitter to
receiver. These transit times are
measured by means of a standard
time reference for the whole
system — ‘GPS time’ — established
by caesium and rubidium atomic
clocks carried in the satellites
themselves. The receiver – say on
board a ship — doesn't need to
carry its own atomic clock be-
cause it obtains the system time
reference from the satellite
transmissions. Similarly the re-
ceiver also obtains the positions
of the satellites in the form of
orbital data sent by these trans-
missions.
Thus Navstar/GLONASS is
broadly similar in principle to a
terrestrial hyperbolic navigation
system like Decca or Omega. A
constant given difference be-
tween the transit times of signals
from two transmitters at known
positions means that the receiver
lies on a particular hyperbola. A
378
third transmitter of known posi- |
tion will establish another hyper-
bola in the same manner. Where
the two hyperbolas intersect is
the position of the receiver.
In the satnav system the re-
ceiver can work either sequen-
tially (single-channel) or simul-
taneously (multi-channel) from
the satellites. The Leeds receiver
shown here is a single-channel
type. If the height of the receiver
(2) is known, signals from three
satellites are sufficient for a posi-
tion fix; if not, four satellites
must be used. The r.f. signals
transmit digital data carrying all
the necessary timing, synchro-
nization, positional, orbital and
correction information, includ-
ing an ‘almanac’ giving satellite
positions for months ahead to
help the user. This 50-bit/s data
is transmitted by spread-
spectrum technique to counter
jamming, the received signal
being buried at least 200B down
in the noise. One pseudo-
random noise (p.r.n.) code is
transmitted for civil use, another
for military use.
Thus the receiver's job is to
acquire the p.r.n. code signals,
decode them and process the
resulting data to calculate posi-
tion fixes. It involves a mixture of
conventional r.f. engineering,
signal processing and digital
computation. The central part of
the computation is to solve a set
of four simultaneous equations,
corresponding to four satellite
inputs, to obtain distances in the
co-ordinate system.
In the single-channel Leeds
receiver (see diagram) the civil
satnav signal at 1575.42 MHz
with a power of about 10 '5W is
picked up by a small microstrip
antenna and fed to a front end.
Then two stages of frequency
down-conversion produce an i.f.
of 10.7 MHz. This is still a
spread-spectrum signal with no
tunable carrier in the conven-
tional sense. To recover the
transmitted p.r.n. code, the sig-
nal is correlated with a locally
generated p.r.n. code obtained
through the action of a code
tracking loop.
When correlation is achieved
by the loop the spread-spectrum
signal is de-spread. The compa-
ratively wide p.r.n. signal band-
width of about 2 MHz is collapsed
to that of the data — a few hun-
dred hertz. The signal then pas-
ses to a carrier tracking loop, and
conventional coherent demod-
ulation technique is used to re-
generate a carrier and recover
the 50-bit/s p.s.k. encoded data.
The block marked ‘pseudo-
range measurement' is for
measuring the time of arrival of
certain precise data signals cal-
led epochs by reference to a
10-MHz master clock in the re-
ceiver. These measurements,
along with the data recovered by
correlation etc., provide the
basic information required for
the position-fixing computa-
tions. All system control and
computation is performed digi-
tally Буа Z80B microprocessor,
using an STD bus and the C
programming language. Naviga-
tional and other data are trans-
ferred via i/o devices to a v.d.u.
and printer.
Normally the position-fixing
accuracy of a ‘straight’ Navstar
receiver is within 20m or
perhaps even 10m. But Dr Daly
explained that this could be
greatly improved by the use of
additional receiver techniques.
For example, integrated Doppler
would increase the precision to
about | metre. Then measure-
ments of code phase could be
used, and also measurements of
carrier phase, where the period is
much shorter. At the L-band
frequency used, for example, the
wavelength was about 19cm. He
said it was not difficult to make
phase measurements to a tenth
or twentieth of a period.
Dr Daly mentioned that cur-
rent research at Leeds included a
refinement called ‘differential
capability.’ This has two Navstar
receivers working together. If
receiver A already ‘knows’ where
it is, it can compute any system-
atic errors. It then transmits this
error information over a com-
munication link to receiver B, in
a format like that of a satellite
code transmission. Receiver B
can then receive, decode and
utilize this sytematic error in-
formation to correct its own
position-fixing data to the level
of accuracy possessed by А.
Satellite systems was written by
Tom lvall.
ELECTRONICS & WIRELESS WORLD
. FORTH INSTRUMENTATION
m COMPUTER
imde Б. TDS
"Ен / 9090
unn;
A powerful control computer based on the new Hitachi
6303Y and high level language Forth. 100mm x 72mm.
30K bytes RAM, 16K dictionary RAM PROM, 256 bytes
EEPROM, 16K Forth. You can attach 64 key keyboard,
LCD and [°C bus peripherals. Built in are interrupts,
multitasking, time of day clock, watchdog timer, full
screen editor and symbolic assembler. 32 parallel and two
serial ports. Single power supply and low power 3mA
operational mode.
1 off £194.95 including manual and non-volatile RAM.
Triangle Digital Services Ltd
100a Wood Street, London E17 3HX
Telephone 01-50-0442 ^ Telex 262284 (quote M0775
ENTER 31 ON REPLY CARD
EN FIELD ELECTRIC LTD.
3 Shenley Road, Borehamwood, Herts WD6 1AA. 01-953 6009
Official Orders/Overseas Enquiries Welcome/Order by phone or post. Open 6 days, half
day Thursday. Please ring for С/Р details not shown. Postal rates apply О.К. mainland
only. All test equipment carries warranty. All prices incl. 15% VAT & c/p unless stated
40V 0 2A £80 ОО, Kir
А £7500 М.
new wi
ke miches 1240 munrocker Ax 4
eads £6.95 t м Vick splay Display and board £11 00
£175.00, Ne
A £1050 NEW.
+ е
Р | SPECIAL OFFER
] NSI м
NEW AND BOXED &57 50
£6.00
“ALL OUR PRICES INCLUDE 15% VAT & CARR/PACKING UNLESS STATED. SAVE TIME PHONE
YOUR ORDER FOR QUICK DELIVERY WITH ACCESS OR VISA CARDS
ENTER 49 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD
——222 =.
Three steps ahead.
Whether your application demands a1.8° Hybrid
Stepper Motor or one of our 7.5° or 15° Permanent Magnet
Stepper Motors, we'll demonstrate how responsive a
European manufacturer can be; providing standard
variations if necessary and arranging delivery times which
compare well
We offer a choice ef phase resistances and electronic
controllers, and guarantee long life expectancy and high
reliability.
For a complete literature pack, telephone Carol Pearce
on Farnborough (0252) 513211, or complete the coupon
below. Your first step in the right direction
Г Please send me your stepper motor nformatio pack 1
Мате |
| Position
| Company
| Address
|
|
Telephone
EWW/4/87 E
Crouzet Limited
108 Hawley Lane, Farnborough, Hampshire, GU 14 8HY.
Telephone (0252) 513211. Telex 858612
SWITCHES MOTORS TIMERS PNEUMATICS
аанай!
ENTER 14 ОМ REPLY CARD
379
OSCILLOSCOPES
CROTECH SINGLE TRACE 20MHz 3031/36 £195/216
2mV 10Vidiw 40ns-0. 2s/div. Cal 0.2V. Component test
3031: CRT 1 5kV 5х7ст 3036: CRT 1 BkV 8x10cm.
CROTECH DUAL TRACE 20MHz (@2тУ) 3132 £285
2mV 10V ст Chi+Ch2 X Y mode Cal 02V
TkHz sq 40п5 О 25 ст Auto, normal or TV tng
Component comparator DC outputs 2 input. CRT 2kV
8х 10cm
HAMEG DUAL TRACE 20MHz (@2т\) НМ203-6 £314
2mV 20V'cm СҺ2+ Ch1 XY Cal О 2V 2V 1kHz sq
20ns О 2sicm Auto, normal or TV trig Component test
CRT 2kV 8x 10cm
HAMEG DUAL TRACE 20MHz ((B5mV) HM204-2 £418
ImV-50V/cm Ch2+Ch1 Sig delay X Y mode
Y out 10п 1 25s/cm Sweep delay 100пѕ 15
Cal O 2V 2V 1kHz 1MHz Z input Comp test CRT 2kV
8x 10cm
— <
w
Q m6 Oia
HAMEG DUAL TRACE 60MHz (@5mV) HM605 £583
ImV-50Vicm. Ch2+Ch1. Sig delay. X Y mode У out
5ns-2 5sicm Sweep delay 100ns-1s Cal O2V 2V
TkHz/1MHz. Z input. Comp. test. CRT 14kV 8x10cm
LEVELL
for INSTRUMENTS
HAMEG DIGITAL STORAGE 20MHz HM205 £498
2mV 20У ст Chl-Ch2 Single shot and X Y modes
20ns 0 2s cm Auto. normal or TV trig Component test
Cal О 2V 2V 1kHz 1MHz 2 input. Two 1K memones
1O0kH? sampling Y out CRT 2kV 8х10ст.
HAMEG DIGITAL STORAGE 20MHz HM208 £1460
1mV-50V/cm. Ch2+Ch1 Single shot and X Y modes.
20ns O 25s/cm. 20MHz sampling Two 2K memories
Plotter output О.1\/ ст. 105 ст CRT 14kV 8x 10cm
HITACHI DUAL 20MHz V212/222/223 Е299/395/450
ImV-12Vicrm 20MHz at 5mV СҺ1+СҺ2. X-Y Chl
output. 100ns-0 5s/cm Auto, normal or TV trigger
Cal O.5V 1kHz square Z input CRT 2kV 8x10cm
V222: Plus DC offset and altemate magnify function.
V223: As V222 plus sweep delay 1us-100ms
HITACHI DUAL 40MHz (@5mV) V422/23 Е580/650
As V222/V223 but 40MHz. 20ns/cm and 12kV on CRT
HITACHI QUAD 100MHz ((G5mV) V1050F £1095
Ch1/Ch2: 0.5mV 12V/cm. Trigger Ch3/Ch4: О 2V/cm.
Dual time bases 2ns-0.5s/cm and 2ns-50ms/cm. Signal
and sweep delay. CRT 20kV 8х1Ост.
THURLBY 8 CHANNEL MULTIPLEXER OM358 £179
Increases any oscilloscope to 8 channels. Choice of trigger
from any channel. Response DC-35MHz.
LOGIC ANALYSERS
THURLBY LOGIC ANALYSERS LA160A/B £395/495
16 data channels. Clock DC- 10MHz (20MHz for В). Binary,
Octal, decimal, or hex. formats.
COUNTERS & OSCILLATORS
COUNTERS MET 100/600; 1000/1500 £99/126/175/199
8 digit 0.5” LED. 5Hz up to 100/600/1000/1500MHz.
Resolves 0.1Hz. Sensitivity 5mV up to 10MHz. Low pass
fiter. Mains/rechargeable battery powered.
LEVELL RC OSCILLATORS TG1520/DM £99/125
3Hz-300kHz. 5 ranges, acc 296 «0. 1Hz up to 100kHz,
3% at 300kHz. Sine or square < 200,V to 2.5Vrms. Distn.
<0.2% 50Hz-5OkHz. TG152DM has an output meter.
LEVELL RC OSCILLATORS TG200D/DMP £139/175
1Hz-1MHz. 12 ranges, acc 1.5% +0.01Hz to 100kHz, 296
at 1MHz. Sine or square outputs <200.V-7Vmns.
Distortion «0.0596 SOHz-15kHz. Sync output >1V.
TG200DMP has output meter and fine frequency control.
LEVELL DECADE OSCILLATOR TG66A £330
0.2Hz-1.22MHz. 5 ranges. 4 digits, acc 0.3%
6Hz-100kHz. Sine output «30,V-5Vrms. - 2dB/ + 4dB and
V scales. Distn.<0.15% 15Hz-150kHz. Mains/battery.
LEVELL FUNCTION GENERATORS TG302/3 #136/236
0.02Hz-2MHz in 7 ranges. Sine, square. triangle, pulse and
ramp 20mV to 20Vpp from 500. DC offset О/+ 10V. TTL
output. TG303 also has a CMOS output and 6 digit 10MHz
counter with INT/EXT switch.
OTHER INSTRUMENTS AVAILABLE - FREE DELIVERY MAINLAND UK - QUANTITY DISCOUNTS - VAT EXTRA
mta
than in older tuned-type inverters.
For fuli details contact:
Tel: 0767 260997
ENTER 38 ON REPLY CARD
380
LEVELL ELECTRONICS LTD. ™
CARACAL
SINE WAVE INVERTERS
200 to 1000 VA
CARACAL produce the U.K's best range of sine wave
inverters up to 1000 VA, noted tor their outstanding
reliability and ruggedness. The use of p.w.m. technology
results in much Pipher efticiency and lower standby current
CARACAL inverters have been in use around the world Гог
many years providing backup AC power tor computers,
communications and instrumentation. They are also widely
used to provide AC power in mobile applications.
CARACAL POWER PRODUCTS LTD
42-44 SHORTMEAD ST., BIGGLESWADE, BEDS.
ENTER 24 ON REPLY CARD
Outputs
РА
Ian Р.
охоп Street, Barnet, Herts., ЕМ5 550, England
Telephone: 01-440 8686 & 01-449 5028
173MHz FM TELEMETRY RADIO LINK
№ Line of Sight Range typically over
300 metres with 1mW ERP +
over 900 metres with 10mW ERP.
№ Modular, Wall Mounting
Transmitter + Receiver
№ Direct Baseband Inputs +
№ Approved to MPT1309
№ Each Module 86 x 104 x 45mm
+ requires only 30mA dc at 7.2V
Œ ‘Add on’ Modules for Remote
Switching, Voltage Monitoring +
Serial Data Transmission.
ADENMORE LTD
27 Longshot Estate, Bracknell, Berks. RG12 1RL Tel: 0344 52023
ENTER 86 ON REPLY CARD
19” RACK MOUNTING CASES
A range of lightweight aluminium 19” rackmounting cases at
competitive prices, available in the following sizes.
Front panel, 3mm extrusion finished in dawn grey, all other panels 16 SWG
clear onodised aluminium. It should be noted that no constructional
fixings are visible on the front panel.
For finishes or sizes different from above, or for details of our range of
blank panels, vent ponels, audio and video jockfields, panel punching and
prototype manufacturing services, please call.
Please add 3.00 P&P +15% VAT
3 Darwin Close, Reading, Berkshire RG2 OTB.
Tel: (0734) 311030
Height Depth Price
1RU 89mm 28.00
TRU 153mm 28.50
1RU 254mm 29.00
2RU 89mm 30.90
2RU 153mm 31.75
2RU 254mm 32.60
зки 89mm 34.50
3RU 153mm 35.25
3RU 254mm 36.35
Kinloch & CO. Ltd
ENTER 19 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD
Р1опееу$
4. Charles Wheatstone (1802-1875) — Master of telegraphy
W.A. ATHERTON
Sir Charles Wheatstone and his family: this stereoscopic daguerreotype is in the National Portrait Gallery, London.
t is an irony indeed when a prolific
| is mostly remembered for an
invention that was not his.
Charles Wheatstone did not invent the
Wheatstone Bridge. He did however invent
the concertina. one of the first electrical
relays, the rheostat. a solar clock, improve-
ments to the mouth organ, a typewriter, a
binocular 3-D viewer similar to the modern
toys. a stethoscope which he called a mic-
rophone, and some of the best 19th century
telegraph systems — amongst other things.
Born in Gloucester on the 6th February,
1802, Wheatstone was the son of a music
seller. He was educated at a private school
but had no formal scientific education
At 21 he was living in London where he
and his brother had entered the business of
making and selling musical instruments.
Those instruments, and the related science
of acoustics, were to figure large in his life.
Although as yet an outsider to established
scientific circles, he received a visit from
Oersted in 1823. His first scientific paper was
read to the French Académie des Sciences
that year by Arago and published in London,
allat the age of 21
As part of his study of musical instru-
ments, in 1821, Wheatstone had demons-
trated an ‘enchanted lyre’. This was an
entertaining application of the transmission
of sound through a solid rod. A sounding
board, in the shape of a classical lyre and
apparently hanging from the ceiling,
appeared to play music! It was in fact
ELECTRONICS & WIRELESS WORLD
amplifying sound vibrations conducted to it
by a rod from a piano in an upper room.
This early fascination with the passage of
sound waves through a solid rod helped to
turn Wheatstone's thoughts to telegraphy,
the art of sending messages over a distance.
He described the enchanted lyre to the Royal
Institution of London in 1831 and reported
that sound travelled through a solid rod
about 16 times faster than through air. It
would, he said, travel the distance of 200
miles in less than a minute — if a suitable
conducting substance could be found. His
thought, even then, was to transmit mes-
sages. Speech, he had already found, could
be transmitted over short distances "perfect-
ly, though feeble.
The "almost hopeless difficulty" of a
breakthrough for long distances, he wrote,
“might induce us to despair of further
success." The answer, he speculated, lay
with a mechanical speech synthesizer! Bell's
telephone was to be invented shortly after
Wheatstone's death
In 1833, however, his attention turned to
electricity, and in particular the question of
its speed of transmission. It was known to be
extremely fast, so fast that no-one had been
able to measure it. Wheatstone provided the
breakthrough.
His genius lay in devising a method of
measuring the tiny intervals of time between
three sparks located at the beginning, mid-
dle and end of half a mile of wire. This
measurement of minute amounts of time
had defied everyone else. His solution, using
a revolving mirror, was simple and effective,
It became a laboratory classic. Не even
attached a siren to the hand-cranked mirror
so that the tone it generated helped him to
govern the speed of rotation
Wheastone's measurement of the speed of
electricity was much too high, but it was of
the right order and the first to be achieved.
Later with four miles of wire he revised the
figure to 192 000 miles per second, much
closer to the present-day value of 186 000
Partly as a result of this huge success he was
appointed Professor of Experimental Phi
losophy at King's College, London, a posi
tion he retained for life.
But standing before an audience filled him
with terror and he gave few lectures. At the
Royal Institution his scientific papers were
read for him by Michael Faraday who was an
enthralling speaker. It is said that on one
occasion, when due to speak himself, Wheat-
stone fled leaving Faraday to pick up the
pieces
THE TELEGRAPH
‘Who invented the electric telegraph?’ is, as
politicians say, a very good question.
To the modern mind Morse's name comes
most readily; but while he was one of the
most successful telegraph inventors, he was
not the first. Wheatstone could justifiably
claim to have invented the first telegraph
system to be put into daily commercial
operation. In partnership with W.F. Cooke
381
he installed a telegraph able to send and
receive messages between London (Padding-
ton) and West Drayton along the Great
Western Railway from July 1839 and it
operated on a daily basis for 10 years, even
being extended as far as Slough. It was from
this that the British telegraph system
sprang.
Even so, it was not the first electric
telegraph. Once the magnetic effects of a
current were known (1820) several tele-
graphs using magnetic needle detectors
were invented as the same idea came to
different people in different places.
Probably the first to produce ап ех-
perimental electromagnetic-needle tele-
graph was a Russian baron, P.L. Schilling,
perhaps as early as 1825. Although he died in
1837, samples of his equipment had been
sent to friends abroad and one of them was
seen in Germany by William Fothergill
Cooke. Fired with enthusiasm, Cooke re-
turned to England with burning ambitions
to build telegraphs – especially for the
railway companies, his first potential cus-
tomers. His partnership with Wheatstone
led to commercial telegraphy.
Amongst several remembered for their
experiments with electric telegraphy around
this time are the Gauss and Weber part-
nership in Germany, Edward Davy and Wil-
liam Alexander in Britain, and of course
Morse in America.
On his return to England Cooke sought
help to solve the problem of how to get his
telegraph to work over long distances. Over a
mile his results were poor. He turned to
Wheastone in February 1837 only to discov-
er that the scientist already had his own
ideas for a telegraph, and a knowledge of
electricity, and success with four miles of
wire. Whilst Wheatstone provided the tech-
nical expertise and scientific knowledge,
Cooke supplied the drive and vision neces-
sary for commercial telegraphy to become a
reality.
In April that year Wheatstone received a
The invention Wheatstone did not create
THE WHEATSTONE BRIDGE
In the early 1840s Wheatstone set out to obtain
a firm basis for electrical measurements:
voltage, current, and resistance. This was at a
time when Ohm's law was still not widely
known in Britain. Using Ohm's work. Wheat-
stone devised his own units and built a stan-
dard resistance. During this work he used the
bridge principle described by Samuel Hunter
Christie in 1833. Despite his giving Christie
due credit for inventing the bridge it was
Wheatstone's name which stuck.
382
Fig.1. Cooke and Wheatstone five-needle tele-
graph, 1837 (Science Museum).
опетнени"
D 25d p ee
Fig.2. A simple ABC telegraph from about 1890-
1900, bought with other ‘junk’ in an auction. Н
still works and is now in the hands of a collector.
The transmitter is on the right.
visit from the great American scientist
Joseph Henry, and learned of Henry's out-
standing work on electromagnets and their
operation through long lengths of wire. A
missing scientific link slotted neatly into
place.
А partnership was formed, at times very
acrimonious and in need of arbitration to
settle disputes. Patents were acquired, and
after trials and tribulations, success came
with the Paddington to West Drayton tele-
graph.
This was the famous five-needle telegraph
now in the London Science Museum. Five
wires were needed, one to each needle, any
two of which could be made to complete a
battery circuit. The current flowed out by
one wire and back by the other. The choice of
wires and direction of flow was dictated by a
permutating keyboard and a letter was indi-
cated on the diamond-shaped dial by the
simultaneous deflection of two needles
(Fig.1). The instruments were well designed
and made, a characteristic of Wheatstone
probably born during his apprenticeship as a
musical instrument maker.
This telegraph was a huge technical suc-
cess. In 1843 the line was extended to Slough
by Cooke, a total distance of 19 miles, using
only two needles with codes. Two years later
it achieved fame when police in Slough
telegraphed to Paddington the description of
aman who had just murdered his mistress in
Slough. His escape by train to London took
him into the arms of the constables.
. By the end of 1845 the telegraph had
arrived and the number of lines was increas-
ing. The next year the Electric Telegraph
Company was formed and Wheatstone re-
ceived the healthy sum of £30,000 for his
share of the patents. By 1870 the telegraphs
had been nationalized at a cost of some £8
million.
Wheatstone had meanwhile turned to the
design of ABC or_letter showing’ telegraphs.
These had a dial with letters printed around
the edge, only one of which would be visible.
(or indicated) at any time. The first were
essentially synchronized stop clocks with a
remotely-operated electromagnet which
could be used for stopping and re-starting
the mechanism. The user simply noted down
the letter shown each time the clock
stopped.
Later, however, Wheatstone made the
transmitter send multiple pulses down the
line, each of which stepped the receiving dial
on by one letter. Some of these devices were
little bigger than a pocket watch and ex-
quisitely made.
Although slow, ABC telegraphs were used
in a sizeable network in London from 1860.
Wheatstone’s were not the only versions;
they were made in several countries and
some remained in use up to World War I.
Much faster than the ABCs was the Wheat-
stone automatic telegraph of 1859. Its suc-
cessors were in use for over halfa century. As
with computers a hundred years later, paper
tape was used to speed transmission, the
message being coded by hand as punched
holes which then drove a transmitter at high
speed. Wheatstone's interest in coding de-
veloping into an interest in cryptography
and he even deciphered some documents for
the British Museum.
Charles Wheatstone made so many inven-
tions they could fill a book. Just one suffices
to illustrate his breadth of interests; a solar
clock which used the polarization of sun-
light to indicate time even when the sun
itself was obscured. It was used on Arctic
expeditions.
When Wheatstone died in Paris on 19th
October 1875, a renowned scientist and
inventor, he had received many and varied
honours. The medals alone are said to fill a
box of a cubic foot capacity. He sat on many
important committees, was a Fellow of the
Royal Society, and a foreign member of the
French Académie des Sciences. Both Oxford
and Cambridge Universities honoured him
and he was knighted in 1868. He refused the
Albert Medal of the Royal Society of Arts
because they offered the same award to
Cooke, his former partner. It was a bitter
legacy of the tensions and disputes between
them.
There was one unusual honour, though,
of which Wheatstone may not even have
been aware. In 1841, with Isambard King-
dom Brunel and others, he was aboard a
locomotive when Brunel set out to discover
how fast it could go. At about 90 miles per
hour Wheatstone and his companions prob-
ably held the world land speed record!
Samuel Finley Breese Morse, the American
artist and engineer, will be next in this series
of pioneers of electrical communication.
ELECTRONICS & WIRELESS WORLD
SuRTEL
UHF VHF
RADIO
TELEMETRY
Scientific
Instrumentation
Automatic Cuided
Vehicles - Machine
Control Systems – Data
Buoys — Plant Control
Mobile Terminals
Displays - Environmental
& Meteorological
Systems - Strain Gauge
Monitoring — Survey
Instrumentation
@ UHF - Digital Communications at 1200 Baud over one or two way
line of sight conditions (458 MHz nom.)
Ф VHF — As for ОНЕ but available at 173 MHz working
@ INTELLIGENCE — Microprocessor based radio telemetry providing
error checking and data formatting etc.
Outputs for VDU's, Printers, Computers,
Terminals.
Features: DTI Home Office approved to MPT 1309
weatherproof housings (IP65) — portable — rugged
high/low power selectable — standby operation reduces
battery drain — 12 volts D.C. — low power consumption
visual monitoring of operation.
Overseas customers may specify higher power options or
alternative frequency of operation — OEM enquiries welcome
MICROMAKE ELECTRONICS
1 THE HOLT · HARE HATCH - UPPER WARGRAVE
READING - RG10 9TG
TEL:0735223255 ТЕХ: 946240 Ref 19023890
ENTER 27 ON REPLY CARD
E NDITNEERITNDESOFITHRIRIE
PCB- DRAFTING - ELECTRONIC DESIGN
PCB
DASOFT PC2 The total PCB design system with
symbol footprint and schematic editors. Board
design editor complete with Auto-routing and
manufacturing software ................. sss
PCB-PADS Multi-layer PCB designer ..................
Auto-router for PCB-PADS
ORCAD Schematic capture system with net list
РОТЕ, зарина вагарна dai
DRAFTING
DRAFIX 2D Drafting with features that would
normally cost 4 times its ргісе..............................
Mailorder price seis ndis анон
ELECTRONIC DESIGN
FROM BV 14 Packages for the R&D Engineer DC
and AC Network analysis programs, Signal
processing, Active filter designs, Root locus
analysis, Transfer function analysis,
Communications design spreadsheet, Scientific
caulculator, Thermal analysis plus printer and
plotter programs ....................... each costing only
SPECTRUM MICRO CAP2 analogue analysis
program with schematic input AC, Transient,
Fourier, DC, Worst case analysis with also
temperature stepping лаарын,
SPECTRUM MICRO LOGIC analysis program
capable of handling 1,800 gates. High res timing
dia showing select waveforms and with glitches,
and spikeselt esca iive Mack cud oq nc
CALL US FOR LITERATURE
BRIGDEN TECHNOLOGY 0322 331984
UNIT 24, ERITH BUSINESS CENTRE, ERITH HIGH STREET. ERITH, KENT 038 1QY
£3,750.00
£1,500.00
£1,000.00
£595.00
£495.00
£395.00
£79.95
£895.00
£450.00
ENTER 41 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD
INSTRUMENTS
COMPONENTS
EQUIPMENT
OSCILLOSCOPES
НАМЕС wiih component testers
203/6 Dual 20 MHZ | with probes! £314.00
204 With sweep delay £418.00
205 бїрї! storage dual 20MHZ £198.00
605 Dual 60 MHZ plus sweep delay £583.00
CROTECH with componeni tester
3031 Single 20 MHZ 95cm CRT $ 195.00
HITACHI у212 dual trace 20 MHZ
8 x 10cm Р.О.А
GENERAL О$Т5т single trace 5 MHZ
T CRT £139.09
HUNG CHANG Dual trace with probes
620 Dual 20MHZ - component test £295.00
635 Qual 30MHZ Sweep delay £399.00
615 Dual 15M HZ bat ‘Mains £399.00
650 Dual 50MHZ Sweep delay £579.00
COUNTERS AND TIMERS
220/240V AC mains. 8 digit LED
Counters 0.1HZ resolution. SmV sensitivity
100MHZ 2 ranges £99.00
500M HZ 3 ranges £126.00
1000M HZ 3 ranges £175.00
1500M HZ 3 ranges £199.00
Timers 0.001HZ Resolution. 100M HZ SmV sensitlvily
ОРТО Standard model £219.00
OP100 Incl display hold. etc stopwatch, APM. etc
£285.00
DC POWER
SUPPLIES
variable output voltages
Direcl meterveading
volts and amps
243 0/24 volis 0/3 amps 0С £43.26
245 0/24 volis 0/5 amps OC £56.26
154 5/15 volts 0/4 amps 0C £33.26
29.95
£150.00
0/30V 1.54 OC wilh voll meter
0/30V 0/2 amps OC LCO display
3% digit LCO displays
508 15 range. 200mA OC. 2 MEG. £19.96 ^à
105 14 Range 2A 0С £21.50
5287 13range. plus Hte msi £26.04
55С 28 range 10A AC/OC 235.65
6010 28 range. 10A АС/ОС. 20 MEG
DIGITAL митметевз{
£33.50
578 20 range.auto- memory: hold 10А AC/OC £34.50
615 19 range. plus Hle 1251 20MEGIOA0C £30.39
5010 31 ange 104 AC/DC - buz Aua А/С £36.50
TM357 30 range 10A AC/DC * buzz £39.00
5010 EC 255010 - cap > Ме + cond £52.13
SWITCH MODE PSU's
Open Frame Models І/Р 100/240V AC
OF 406 -5V SA -23V 23тА -12V 100mA:
. тА £8.65
V2v 500 y
SK102 to Sv Jadjustabie) 10amg £7.78
GOW: 5V ЗА: · 12V 29A. + 18VIA -5v 0.24 213.00
Enclosed Model
85/97W -5V бА. -12V 4. 75А: 12V 5A
BENCH DMM'S |
£19.95
С
3210 0.1% True RMS
STOCKISTS FOR:
Accessories ө (See Catalogue)
ша HENRY'S
| | (UK orders onl
ACCESSORIES Я: БЕЙЕҮ
240V AC Input. Stabilised
3), Digit СО 10A — ann |
AC/DC 20 mag. Buzzer aic. === SS SEE! жап.
322 0.25. £ 89.00
Logic Analysers ® Insulation Testers ® Temperature meters ® Security Systems
* Public Address e Communications e Tools e Computer Equipment TV/Video
ORDER BY POST OR PHONE. DPEN 6 DAYS A WEEK FDR CALLERS.
QUDIO
ELECTRONICS
301 Edgware Road, London W2 18N. 01-724 3564
404 Edgware Road. London W2 1ED. 01-724 0323
TELEX 298102 TRANS С
EDUCATION AND ACCOUNT ENQUIRIES 01-258 1831
EE
Official orders
welcomed.
Export supplied.
| Please add 15% VAT
——
FUNCTION - sine. sq. irlangle. TTL Q/P
J500 0.1HZ 10 SOOKHZ £110.00
TG101 0.02HZ to 200KHZ £110.00
TG102 0.29210 2MHZ £160.00
PULSE Square, Complement. TTL 0/P
16105 SHZ to SMHZ £105.00
TV-VIOEO PAL VHF/UHF. 5.5/6/6 SMHZ
sound carriers RGB and SYNC 0/P's. AM/FM sound mod
Colour. etc £199.00
GENERAL EQUIPMENT
X1/X10 Probe kits [250MHZ] £10.00
200 100KHZ - 110MHZ A-C OSC £55.17
220 20н1- 200KHZ A-C OSC £78.22
СМ200 Bench Digital Cap. Meter 9.
TH301 LCD 010101 Temperature £59.50
2018 Audio Power Meter £220.00
YFSO1 Electronic insulation Tester £65.
РЕМ200А 200MHZ Pocket LED Counter £75.50
OM 358 8 CH. Scope Mulliplexer £179.00
комб 250MHZ TR, DIP Meter £43.04
2016 1HZ-1MHZ Generator 05' £180.00
ANALOGUE —
MULTIMETERS е |
1015 15 range pocket 10K/V £7.50
103$ 19 range 20K/V 104 0C £ 10.39
10282 19range 10A 0С - № 20K v£ 12.61 Ё
HC201 19 Range 20K/V 12А АС/0СЕ 15.61 >
2020 20 range 10А OC • ме 20K /V £19.09
301082 24 range 10A DC · buzzer WK/V £20.83
155m 21 range 10A AC/DC 20K/V £22.57
5050Е 41 Range FET 20MU/P £28.65
830A 26 Range 10A AC/DC 30K/V £25.17
ЕНТ МЕТЕ аы
0/40KV Direct Reading £45.00
a7 |
PROBE/PULSER =
6108 20MHZ Logic probe & bieeper £16.95
625 SOMHZ Probe & pulser 0582 50002 £22.95
07 20MHZ Logic probe £9.52
AC CLAM PMETERS With cases and leads
300 300amps {5 ranges}
500V 14 ranges] IK OMM. £32.83 Cv
4300 Autor ange Digital 300A At
500У - cont test £85.00
DIGITAL CAPACITANCE
METER 8 range Lco 200p1 to /000МЕ0
Push-button selection {6013} £55.00
ENTER 26 ON REPLY CARD
383
MicroProcessor Engineering Ltd
21 HANLEY ROAD
SHIRLEY
SOUTHAMPTON $01 5AP
FORTHS
For IBM PC and Compatibles
Modular Forth
Source Code
Workforth
Workforth Extensions:
Viewtrace
Floating Pt
Windows & Graphics
Doc Tool Pack
Workforth and all extensions
For Atari ST
Gem Forth Metacomco
For Vax, RSX-11, etc Uniforth
MPE-Forth/OS9 68K
For Macintosh, Apple, C64, Amiga, QL
etc
MasterForth by MM
Extensions: flt Pt
HIRES graphics
Proforth by HMcG
(Shareware, pay more to use it)
MVP-Forth for C. Amiga
FORTHRIGHT
£475.00
£5,000.00
£55.00
£35.00
£35.00
£45.00
£45.00
£145.00
£65.00
£175.00
£375.00
£100-£120
£45.00
£45.00
£10.00
Tel: 0703 780084
CROSS-COMPILERS
For CPM 80, MSDOS, PCDOS, CPM 68K,
FLEX, OS9 (needs workforth as host)
Targets: PDP-11, 6502 6511Q, 8080/5, Z80,
8086/88, Z8, 1802 8070, 6809, 6800/01/03/6303,
68000, 99C0, 99000.
8031/51 Bryte Forth
Forth-83 Targets:
280, 8086, 680X0 32-bit
For RT-11, RSX-11 and VMS-11
Uniforth — Prices on application
HARDWARE for PC Programmers:
Gal Programmer (MPE)
Pal Programmer
EPROM Programmer
Stack EPROM Programmer
Forth Engines:
Novix 5MIP Board
MVP Microcoded
Kaypro PC Clones
286i (AT Clone with 20Mb)
K16/2E (Lu Ye PC)
K2000 (LCD and batteries)
Amstrad PC Clones
£350.00
£225.00
£450.00
£350.00
£145.00
£795.00
£852.00
£1,225.00
£2,200.00
£1,450.00
£1,132.00
£549-£1,069.00
ENTER 79 ON REPLY CARD
R. В. WITHERS COMMUNICATIONS LTD г.
0f world famous communications products 2
584 HAGLEY HAGLEY ROAD | ROAD WEST OLDBURY, WARLEY, BIRMINGHAM B66 085 4
021-421 8201/2/3. CELLNET 0860 323056. PRESTEL MBX 214218216 FAX 0215614074
Amateur Radio. Business Radio. Radio Telephones. Sales. Service Accessories and antenna
Wacom YAESU “7 dy THE TECHNICALLY ORIENTATED
RADIO COMMUNICATIONS
100Khz to 950MHz IN ONE BOX! SPECIALISTS.
THE YAESU FRG9600/RWC МКЗ SCANNING RECEIVER
Now at last a "World First" from Ray Withers Communications Ltd. Here are
some of the unique features only available on this fine receiver:
КЛИ LW. MW SW, VHF/Low Ar-band. 137-Satelite, HF/High. Miltary. UHF/Low. ОНЕ TV
ieee Celiulai Al Beca каг, Aur, Manne, Amateur. Business Надю. Miltary. TV. Cotta te to SOME) Thes
unit i$ now autable lor usa wn any country as al Dande/Chaonel steps afe now азайа.
Pos Mode Capability. АМ/ҒМ (mde and narrow modes). LSB. USB. Video ophon available (NTSC/PAL 5 S/6MHz
Selectable Frequency Steps. Mos! modes have selectable tuning steps which allow las! and easy
frequency/c channel selechon (convenhonal tuning)
. ы Memories/Scanning. Any frequency т the п can be entered/stored «nto а memory
"cted/sc. m banks, pnonty funchon allows monitonng of important channel/frequency while де сэз
other bands/ch anneis Modes are aiso stored in memory
+ Fully Computer Compatible. Yaesu's CAT system is а slandard feature and a RS232 interface is available
pius other interfaces for popular HOME computers With Низ feature memones can be expanded and the unit can
be remote controlled ма a modem
* Clock Function. Clock funchon allows nme E and auto switch огой of the receiver
High Receiver Er ian іп the range а (уржа! recever sensitivity 15 >1 SuV for 1208 SINAD
(FM) m the range 1 6MHz-60 000MHz Med “| 12d SN SINAD (FM) below 1 GOOMHz sensitivity is nominally »6uV `$
meter funchon allows nominal heki strength measurement
* 138 Мон DC Operation. The ипи operates at 138V DC а! tA max which allows mobie/portabie/base
орегавоп
* Matching Antenna Options. Matching antennas for portable/mobwe/ixed apphcabons are avaiable ех-5ЮСК
including wide-band drscones
Please ask for full colour brochure and detailed specifications are available with
Бату 60-950МНІ, ali units now have 'N' connectors fitted for Е =” 50239 connectors
The YAESU МК2/3 RECEIVER ts only available trom RWC Lid earker models can have the extended bands and
HF module fitted and recever sensitivity/ S' meler improved, please enquire for more details and рпсез
Export enquiries welcome
Tet: 021 421 8201 come теневое) aay NG саега ENG ор LR ЕЕЕ
Telex: 334303 G TXAGWM
ENTER 6 ON REPLY CARD
384
EAI-E-IDE. LIT WY
WITH SOUND PRINCIPLES
The GATE ONE amplifier is no т hobby kit. lt is uncampromising in the elctronic and
mechanical design. the zircuit board layout, choice of componants and case finish. It looks and
sounds as good as amplifiers in the class. which is indeed what it would cost if we were to
manufacture and sell in volume through normal retail outlets.
Considerably attention has been given to the circuit layout which uses a double-sided pcb
e psu is regulated, even to the
reservoir capacitors for each channel. All
driver and pre-amp stages are de-coupled. All low lii level signals to the selector &witch are kept in
coax, not sprawled across he pcb as in many other designs. The only power wiring is from the
rectifier to the pcb and direct! e from the output stage to the heavy duty speaker sockets.
The design uses passive equalisation and tone controle with a tone cancel and subsonic
filter facility You can even introduce a subtle bass boost to compensate юг loudspeaker
deíficiency. All inputs other than the MM or MC input bypass tke front end pre-amp. The volume
control is placed directly in front of the main пор whea the oatput overload fuse is included іп
the feedback loop. The мм input sensitivit V with а 29cB overload margin and 80dB S/N
ratio ref full output, which is 40 watts per channel.
The case and pcb are manufactured to professional standards. The GATE ONE kit is £139.61 inc.
but from 1st May this has to go up to £161.00. A fully built and tested GATE ONE is currently
£179.86. Send for further details. PS: This is not just a well engineered design. it sounds superb as
well and offers unbeatable value for money.
GATEHOUSE AUDIO ww
105 High Street, Evesham, Worcs. WR11 4NP. Tel: 0386 48873.
with extensive earth plane, star supply and ground feeds.
complementaryu output darlingtons, with secondary
ENTER 82 ON REPLY CARD
KESTREL ELECTRONIC
COMPONENTS LTD.
* All items guaranteed to manufacturers spec.
* Many other items available.
‘Exclusive of V.A.T. and Post and Package’
+
+
©
+
ooooo--oooooo-
BIRRSSSSSASSSS
оосор ооо омю-ш
88800850520988*
2558053
ВЕНЫ =
оооБо ошоо ооо
оооооооооооооо
зор змо ом омм
8585588
ль = NOON=AONNN
EN28888S358858
ooooooooooooo:
ЗЕЕ Васе
0.25
Atl memory prices are fluctuating daily, please phone to confirm prices.
178 Brighton Road,
Purley, Surrey CR2 4HA
Tel: 01-668 7522
ENTER 65 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD
APPLICATIONS SUMMARY
Monostuble
mu.ti-
vibrator
V+ orlow 5
battery adj. D
V+
| 13 Веер Нтег
Timer Vu MM network /
200 oscillator
30ms sect зи
10 Piezoelectric
<
e
<
d horn driver
11 Alarm oscillator
Da.
Reference 1 enable
voltage
output
» V+
1 Mechanical /
From — 2 piezoelectric
nee js » b [ horn driver
>>” A
6 Photo/Le.d
с
Chamber adj.
V+
To 1
Bias set current > o ^^ interconnect
sources. 2k
‹ a
9 ww
V+ or output enable
piezoelectric horn feedback
ONE-CHIP SMOKE
49V Note- 1. Ins. res. 10GM,~1nA leakage DETECTOR/ALARM
C adjusts low-battery beep & led-
lonization chamber
= 100p blink rate. In the 3164 detector/alarm i.c. mos circuits
T 2. Select for sounder used. form an ionization chamber amplifier while
Pir, ане ane Mora ground bipolar transistors drive alarm devices. De-
i t 2 h Р
н. digas ыр tector input current is sub-picoamp and
alarm-output sink current is up to 300 mA.
The 3164 is designed primarily for use
with ionization-chamber smoke detectors,
but it can be used with photoelectric cham-
bers by adding a few components. Besides
triggering on detection of decreasing voltage
at the smoke detector input, the device
monitors battery voltage and produces a
beep once every 50s when battery voltage
falls below a presettable limit.
Booklet 1139 from RCA describing the
CA3164A includes circuits for a photoelec-
tric detector/alarm and photographic flash
trigger.
Pin 11 see note 3
In Fig. 28 (page 302, March) the value of R217
was omitted and the connections of R3og and
its associated capacitor were wrongly drawn.
This amended diagram shows them as they
should be. The author has also pointed out
an error in the text: in the penultimate line
on page 302. the word advantage should read p oco oi ci BIPM А, Бобы
disadvantage. Way. Harlow. Essex CM20 2DF. tel:
0279 26777
ADDRESSES:
Consumer Microcircuits Ltd
Wheaton Road. Industrial Estate East.
Witham, Essex СМ8 3TD. tel: 376
513833.
RCA Limited /Solid State Division
Lincoln Way. Windmill Road. Sunbury-
on-Thames. Middlesex TW16 7HW, tel:
09327 85511.
Їз
DS26LS32A
CE
ELECTRONICS & WIRELESS WORLD 385
Scrambler ае т ҮН condition — — 4 Receive —= ROLLING-CODE
counter (Tx) ВЕЛТИ ЕТТТ [codes [coves peset — SPEECH SCRAMBLER
Tx scrambler
released In simple speech scrambling applications.
; Secure speech { {һе ЕХ204 from Consumer Microcircuits
eae A | [ splits the voice spectrum into high and low
о/р (Tx) Топе Tone Fane Tone frequency bands and then inverts each band
i | ' about its own centre.
i Frequency of the split point is programm-
E een 32codes | 32codes | 32codes ff Reset able in 32 steps from 300 to 3000Hz. For
Sync. Í more secure operation, the split point can be
: » continually varied, as it is in this rolling-
code speech scrambler/descrambler.
1
Scrambler C | Е > | = 5 А А
counter ее! | 32 codes | 32с00е5 | 32codes [Reset Because the code is continually varving,
Scrambler C joins net SYPE No sync. tone received
Tx audio in Tx audio out
Rx audio in
Rx audio out
МО УЛ Л neuon
SNS
E | md,
a
To key code
selector
FX206 (кир
Р 72 о/р
rm [O FO ро рь
im Ilo [е іо |>
Audio switch
Tone
detector
MC 14066
1M
386 ELECTRONICS & WIRELESS WORLD
PPLICATIONS SUMMARY
the receiver needs some means of synchro-
nizing itself with the transmitter. For this
purpose, an f.s.k. data burst can be sent at
the start of each transmission. Alternatively
a continuous tone above or below the voice
hand may be sent and this tone could have
phase reversals. In the circuit shown, a
р.1.1. detects tones higher than 2400Hz.
Besides this and other applications, the
FX204 data sheet covers specifications and
operation of the device
400-512MHz
PREAMPLIFIER
Electrical. mechanical and performance de-
tails for a GaAs tet 400-512МН2 preamplitier
are given in Motorola note AN925. The
MRF966 GaAs fet used is a low-cost dual-gate
device designed for u.h.f. applications.
In the three-page note, Smith charts show
input/output matching networks and two
graphs show gain at noise figure and opti
mum ndise figure versus frequency with the
preamplifier tuned to 430 and 480M Hz. Two
further graphs give input and output return
loss versus frequency; the ones shown here
are for 480MHz. Circuit board, coil winding
and housing details are also given
Top of PCB
High band o/p4 High band i/p;
Frequency
nverter
High
^x band o/p
N
Mes ———-
Чыл =F
ТЕХ ———
XTAL/CLOCK
" 1MH2
—
LOAD
+ $2
Split point |? Bom
program |
a
Low band i/p4 ^X
Cx
LJ
Low bond о/р
1
4
'
---.----1
l2 ip
17 0/p "Low band i/p,
rf output
Ferrite
bead
06 to10p
20 — 20
1 16 =
= > =
E = 2
ND 12
= = л
5 hi $
w
ш 8 вй =
ё 5 5
а. 5 S
е ч. сс
B. psi
420 0
460 480
FREQUENCY (MHz)
ELECTRONICS & WIRELESS WORLD
500
460 4B0
FREQUENCY (MHz)
520 420
387
i LT
TV IF AMPLIFIER
IBM PC (and compatibles}, RM NIMBUS, BBC MODEL B,
B+ and MASTER, AMSTRAD CPC and SPECTRUM 48K
“ANALYSER” } and И compute the A.C. FREQUENCY RESPONSE of
linear (analogue) circuits. GAIN and PHASE INPUT IMPEDANCE,
OUTPUT IMPEDANCE and GROUP RELAY (except Spectrum version) are
calculated over any frequency range required. The programs are in use
regularly for frequencies between 0.1Hz to 1.2GHz. The effects on
performance of MODIFICATIONS to both circuit and component values
can be speedily evaluated.
Circuits containing any combination of RESISTORS, CAPACITORS,
INDUCTORS, TRANSFORMERS, BIPOLAR and FIELD EFFECT
TRANSISTORS and OPERATIONAL AMPLIFIERS can be simulated — up
to 60 nodes and 180 components (IBM version).
à
ө Г.
ao AAT LF!
OL
SIMPLE AMPLIFIER
Ideal for the analysis of ACTIVE and PASSIVE FILTER CIRCUITS, AUDIO
AMPLIFIERS, LOUDSPEAKER CROSS-OVER NETWORKS, WIDE-BAND
AMPLIFIERS, TUNED R.F. AMPLIFIERS, AERIAL MATCHING NETWORKS. TV LF.
and CHROMA FILTER CIRCUITS, LINEAR INTEGRATED CIRCUITS etc.
STABILITY CRITERIA AND OSCILLATOR CIRCUITS can be evaluated by
"breaking the loop".
Tabular output on Analyser |. Full graphical output, increased circuit size and
active component library facilities on Analyser II.
Check out your new designs in minutes rather than days.
ANALYSER can greatly reduce or even eliminate the need to breadboard new
designs.
Used by INDUSTRIAL, GOVERNMENT and UNIVERSITY В & D DEPARTMENTS
worldwide. IDEAL FOR TRAINING COURSES, VERY EASY TO USE. Prices trom
Full AFTER SALES SERVICE with TELEPHONE QUERY HOT LINE and FREE update service.
For illustrated leaflets and ordering information please contact Ref: WW
Number Оте Systems Ltd
Crown Street, St Ives, Huntingdon, Cambs. PE 17 4EB.
SOWTER AUDIO FREQUENCY
TRANSFORMERS
You name it! We make it!
For the past 45 years we have concentrated on the design and manufacture of high
grade audio transformers during which period our total sold exceeds half a milion We
continually take tull advantage of all the improvements in magnetic and insulating
materials and in measuring techniques utilising the most up to date instrumentation
We have a very large number of original designs made for clients ali over the world
but naturally there are certain types of Sowter Transformers which are in constant
demand These have taken into account the tendency towards small size without
Sacrifice of performance. particularly for PCB mounting. and a few of these are listed
below They can be supplied with or without mumetal shielding cans. Performance
requirements can be modified on request (utilising our readily available questionnaire)
and generally without alteration in price
We specialise in LOW COST AND QUICK DELIVERY which means a few days only or
|
|
ex-stock
TYPICAL PERFORMANCES
Sowter
Type No 3575 4652 3678 6499 4079 6471 6469
Description TMiwmiatore Tune output м primary Tune output Т? Midget mic ven high
bridging microphone high level low | combiner transformer [quahty
transformer transtormer [distortion Wanstormer [tor BT private | microphone
toro dal core [systems [transformer
impedances Пока 1080 |6000 1500 |Руѕ 60 200 |6000) 6000) |2000 Bal Ру |Py 6000 2000 Ру tor
сап be led inputs ог or 6000 Two 2000 Sy 6040 140 toading
|trom outputs Sy 5KQ down Secondanes (Bitar) 8 1
50 6000 to 1080 stepup
+ + + +— + + 4
Frequency 209: 200Нг |20Hr20&Hr |ЗОНг20ьН; |20Hr20kH; |20Hr20&Mr |300Н; 3kAMz |20Hr-20&Hz
jrange
4 | | | Же | ‘Ee
Performance | 0 148 over | 025dB over | О 548 over |-030B OSdBover | O5dBover | -O2dBover
aboverange (above range |aboverange |40Hr15kMr laboverange above range | above range
| + + + + + +
Maximum 2758 (m$ 775 rms on SaN load 26dBmat 234 1ms 06v, ро" гом тз on
Level os secondary on 6000 34Vems 30Hz at 30Hz Primary Py at 30Hz
at ЗОН;
| + + + + + + + 4
Maximum With 10V On 6000 Less than 01% at Neghgible negligible 01% at 20Hz
[Distortion rms at low source? [01% ас анг ЗОН? at 01%а
40Hz only 01% 26d8m lkMz
012%
B + E + + +
Electrostatic |Mumetal сап |Mumetalcan |Toroidalcan |Mumetalean [PCB
$creens and |1? desired at nga fixing mounting
mumetal сап lestra cost bolts
Siweiding
Mumetal can
+ + + + i
Dimensions |33mm diam |3émmhigh - 133mm diam 150mm diam 133mm diam |llimmhigh | 33mm diam
22mm high |43mm 22mm high | - 36mm high | - 37mm mgh | 19mm 22mm high
| 33mm 17mm
+ + + + + +
[Prices each h £1083 l £967 l 4967 1 41712 1 £1459 1 #389 1 41138
jat works 50 1977 50 #889 50 4867 50 #1569 50 #1337 50 #355 50 £1012
100 4927 |100 4869 |100 £841 |100 41535 |100 41308 |100 4329 |100 4992
А. 1 1 = 1 1 4 1 ыл
Е. A. SOWTER LTD. (Established 1941) Reg. No. England 303990
The Boat Yard. Cullingham Road. Ipswich IP1 2EG, Suffolk. PO Box 36. Ipswich IP1 2EL.
England. Phone: 0473 52794 & 0473 219390 - Telex: 987703G SOWTER
ENTER 21 ON REPLY CARD
388
1
|
£20 10 £195.
?
= EW'! AFFORDABLE
кла " РСВ САО
CHANNEL MICRO PRODUCTS LTD
Maximum circuit board size greater than 2’ x 2’
Telephone: St Ives (0480) 61778
ENTER 57 ON REPLY CARD
Powerful гост facility and fast screen re-draw
Full off-screen editing. Mouse & Trackball compatible
Hard copy at 1:1, 2:1 & 4:1 from Epson FX or RX printer
Plotter drivers for most popular plotters available
Low cost BBC Micro hardware keeps system cost below £1500
Software only £240
Please write or telephone for full details.
227 Canterbury Street, Gillingham
Kent МЕ7 5XB. Tel:0634 570256
ENTER 51 ON REPLY CARD
Toroidal & Е.І.
Transformers
As manufacturers we are able to offer a
range of quality toroidal and laminated
transformers at highly competitive prices
Toroidal Mail Order Price List
prices inclusive of VAT & Postage
15va 7.95, 30va 9.18, 50va 10.16, 80va 11.36, 120va 12.07, 160va 14.20, 225va
15.21, 300va 17.04, 500va 22.10, 625va 24.66, 750va 28.75, 1000va 44.82.
Also available 1k2, 1k5, 2k, 2k5, 3k. Prices on request.
Available from stock in the following voltages: 6-0-6, 9-0-9, 12-0-12, 15-0-15, 18-0-
18, 22-0-22, 25-0-25, 30-0-30. 35-0-35, 40-0-40, 45-0-45, 50-0-50, 110, 220. 240.
Primary 240 volt.
Quantity prices and delivery on request
Air Link Transformers
Unit 6, The Maltings, Station Road,
Sawbridgeworth, Herts. Tel: 0279 724425
ENTER 20 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD
HAMEG Ltd. 70 - 78 Collingdon Street,
Luton, Bedfardshire LU1 1RX.
Telephone: (0582) 413174.
Telex: 825484.
Designed and manufactured in West Germany by HAMEG, one of the World’s leading oscilloscope
manufacturers - the range of Industry’s unsurpassed Price/Performance oscilloscopes.
Quality, Performance, Value... Oscilloscope Range
i
[ч
t
_„
‘For those who compare |
"T : Zo
Ire x 7$
"ron zn =
7 1-2» Г"
Ж, | "at = в г:
©: t: ^
Dual Trace 20MHz, 2mV/cm, Algebraic Add,
Component Tester, incl. 2 probes HZ36.
£314.00 HM203-6
Dual Trace 20MHz, 1mV/cm, Sweep Delay,
Component Tester.
£418.00 HM204-2
Dual Trace 60MHz, 1mV/cm, Delay Line,
1MHz Cal. Generator.
£583.00 HM605
Dual Trace 20MHz, Digital Storage Oscilloscope
incl. 2 probes Type Н237.
£498.00 HM205
Dual Trace 20MHz, 4 x 1k memory, plotter
output, incl. 2 probes Type HZ37
£1460.00 HM208
IEEE-488 Interface Version, incl. 2 probes
Type Н237.
£1735.00 HM208
Price U.K. List ex. VAT
2 Years Warranty, Parts & Labour
ENTER 11 ON REPLY CARD
CARDMASTER CPU
e 46MHz Z80 CPU
® CP/M compatible
© User transparent MULTI-TASKING
е Upto 32K EPROM & 16K RAM
@ Watchdog crash protection
e RS232 & RS422 Comms
e 2' Z80a PIO (one uncommitted)
© On board bus buffering
© Power-on jump hardware
€ Euro-card construction
NOW FROM £124 + VAT
CUB MICROCONTROLLER
® 280 CPU
e 4 x Z80a PIO's (64 VO lines)
e 280а СТС
e 4K Battery backed RAM (2K sup.)
е 4K EPROM (2K MCV2.0 sup.)
® Powertul monitor (MCV2.0)
ө Eurocard construction
STARBURST V1.31 CMR16 NOW FROM
ACROSS ASSEMBLERFOR | _ £199.00 —
CP/MBO covers four major Bare PCB's Available
families of single chip uP’s and 1+ 10+
А uC’s C/M CPU 28.50 25.65
* 8048 inc. 8741/2 8748/9/50 C/M УО 28.50 25.65
* 6801 inc. 6800/1/2/3 68701 СМВ16 40.00 36 00
* 6805 inc. 68705 63705 а н `
Supplied with a complete set of Manuals on request
demonstration files. GNC ELECTRONICS
STARBURST V1.31 £95.00 Little Lodge, Hopton Road,
+ VAT Thelnetham, DISS IP22 1JN.
Requires Z80 CPU Tel: 0379 898313
ENTER 64 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD
а сеет
Communications
— | 2222200 T |
ICOM introduces the IC-R70
communications receiver With 99 programmable memories the IC-R7(
advanced technology continuous coverage
covers alrcrafi. marine FM broadcast. Amateur radio. television and weather
satellite bands. For simplified operation and quick tuning the IC-R7000 features
direct keyboard entry Precise frequencies can be selected by pushing the
digi! keys in sequence of the frequency or by turning the main tuning knob
FM wide/FM narrow AM upper and lower SSB modes with 6 tuning speeds
1. 1.0.5. 1 5 and 25kHz. A sophisticated scanning system provides instant
acce: the most used freauencies. By depressing the Auto-M switch the
IC-R7 automatically memorises frequencies thai are in use whilst it 15 in the
scan mode. this allows you tc recall frequencies that were in use, Readout is
clearly shown on a dual-colour fluorescent display Options include ihe RC-|
infra-red remote controller vcice synthesizer and HP- | headphones
[Please rush me details of the IC-R7000 and my nearest ICOM dealer. | ý
| Name |
| Address |
| Е Те]
| Post to: ICOM, Thanet Electronics Ltd., Dept W W, FREEPOST, |
Herne Bay, Kent СТ6 8BR. (no stamp needed). Te]: 0227 363859.
| J
ENTER 12 ON REPLY CARD
389
European
moves from
AT&T
The American giant telecom-
munications company, AT&T,
are opening new sales and design
centres in Bracknell, Berkshire,
and in Stockholm, Sweden.
These will add to the AT&T
offices in Madrid and Munich and
further facilities are planned for
France and Italy.
The British branch at Brack-
nell will offer basic design facili-
ties as well as a sales office for
AT&T products. These products
result from research at their Bell
Laboratories and claim to have
many unrivalled attributes:
their 32-bit, floating-point,
digital signal processor, for ex-
ample, which can operate at
24MHz. AT&T have also pro-
duced a 32-bit microprocessor
which is designed specifically to
work with the Unix-V operating
system (another Bell Labs pro-
duct). Their i.c. manufacturing
offers 1.75 and 1.25pm geomet-
ries with 0.9рт available soon.
The company specializes in
communications equipment and
can offer a wide range of com-
munication circuits and fibre-
optic components.
eye
Philips to sell
Pye TVT?
Philips Electronics has
announced that it is holding
discussions concerning the sale
of its broadcast transmission
subsidiary, Pye TVT Ltd, with a
potential American purchaser,
Varian Associates.
Pye TVT of Cambridge em-
ploys about 220 staff in the
design and manufacture of
broadcasting equipment, especi-
ally for tv transmission. Varian
supplies communications, medi-
cali, analytical and semi-con-
ductor equipment with a re-
ported turnover of $900 million
in 1966. The purchase of Pye
TVT would be part of Varian's
programme to strengthen its
role іп the communications
field. It had already acquired in
1985 the Texas-based Continen-
tal Electronics Company and
has considerable strength in
high-power broadcast and satel-
lite ground-station transmitters,
which would be complemented
by the Pye TVT range. Varian
390
PDATE
has indicated its intention of
continuing the Cambridge op-
erations.
In brief
For those interested in preserv-
ing the history of the telephone,
there has been founded the Tele-
communications Heritage
Group. The group will publish a
quarterly newsletter, approp-
riately called 'Exchanges' which
will include articles, and notices
for the sale of, and requests for
equipment апа information.
Although the group is indepen-
dent of BT, the Telecom Tech-
nology Showcase, 135 Queen
Victoria Street, London EC4V
ААТ, has agreed to act as a
coordinating and postage centre.
This year's subscription is £3.
Further information from the.
group through the Showcase.
А firm of London solicitors has
claimed a world first by offering
legal advice via electronic mail.
Pennefather and Co. is the com-
pany that has decided to break
fresh ground by opting for this
form of communication to
answer queries from clients. The
service is being provided on Mic-
rolink, a national electronic-
mail network. Clients of the soli-
citors can transmit their mes-
sages and receive replies using
their home or business com-
puter.
As an introduction to this on-
line service, all subscribers to
Microlink are being given the
chance of a free consultation.
They can receive one free reply
on any legal query they wish to
raise with the firm.
Philips have opened a new inte-
grated research and develop-
ment centre at its headquarters
in Eindhoven, Holland. Its prin-
cipal object will be development
of sub-micron technology (sili-
con structures with less than
lum width and spacing) in a
research cooperation between
Philips and Siemens of Germany.
Dr Marc Faktor, who spent more
than two decades researching
the optical and electrical pro-
perties of materials, was рге-
sented with BT's Martlesham
Medal. His “pioneering work has
helped to put Britain in the world
forefront of optoelectronic tech-
nology.”
Much of his work with British
Telecom concerned the growing
of crystals from vapour; building
up layers of semiconductor
material no more than a mil-
lionth of an inch thick — on
which the fabrication of today's
optical devices are based. The
techniques which he pioneered,
such as metallo-organic vapour
phase epitaxy are now sufficient-
ly well defined as to be capable of
commercial exploitation. A joint
venture company set up in 1986
between British Telecom and du
Pont is to develop, manufacture
and market optoelectronic com-
ponents and devices which stem
directly from Dr Faktor's work.
During the early 1970s he
headed a team which used orga-
nic materials to build reliable
‘directly modulatable' semi-
conductor lasers. He also devised
the electrochemical technique at
the heart of the British Telecom
` profile plotter, which produces
an accurate profile of the
electric-current carriers in semi-
conductors. This is now manu-
factured under licence and sold
worldwide. Dr Faktor left British
Telecom in 1982 and is a now a
visiting professor at Queen Mary
College, London University.
The construction of two military
communications satellites for
Nato has been awarded to British
Aerospace. The Nato tv satellite
will be virtually identical to Sky-
net 4, currently under construc-
tion for the British forces. Mar-
coni are the principal sub-
contractors for the communica-
tions payloads to be launched in
1990.
A report by Dataquest, of Califor-
nia, on the worldwide semicon-
ductor market for 1986, says that
the three top chip suppliers,
measured in US dollars, are
Japanese companies.
NEC retained its number one
position, achieved in 1985.
Second and third places for 1986
went, respectively, to Hitachi
and Toshiba. Motorola and TI
were relegated to fourth and fifth
places respectively. The places
are quite difficult to work out
because of the fluctuations in
currencies; the Japanese
attained a world growth of 4096,
expressed in dollars, but only
0.296 when accounted in Yen.
Japanese exports actually fell by
896, but this is offset by a 2.696
increase in the share of their
home market.
IEE and IEEIE lectures
and meetings
All meetings held at the IEE,
Savoy Place, London WC2;
information from the Institu-
tion, Tel: 01 240 7753, Ext.
296 or 283, unless otherwise
indicated.
24 March
Electronic filters: IEE collo-
quium
24 to 26 March
Computer aids for electrical
and electronic engineers.
Conference at the Metropole
Hotel Brighton in conjunc-
tion with the CADCAM 87
Exhibition. Details from
EMAP, Tel: 01-606 1161.
25 March
Multi-octave components
and antennae: IEE collo-
quium.
,26 March
The code-breaking compu-
ters of 1944: IEE discussion
meeting at 1415h.
Colossus and the German
cyphers in WW2: IEE lecture
by Sir Harry Hinsley. 1800h.
27 March
Evaluation of interactive sys-
tems design: IEE collo-
quium.
30 March to 2 April
Antennae and propagation
(ICAP 87): IEE Fifth interna-
tional conference at the Uni-
versity of York.
1 April
Digitally implemented
radios: IEE colloquium.
1 to 3 April
Command, control, com-
munications and managment
information systems.
Second International confer-
ence in Bournemouth.
2 April
\.1.5.1. for image processing:
IEE colloquium.
Fibre optics in communica-
tions. IEEIE lecture by В.К.
Willet of Mercury. University
of Cambridge Engineering
Laboratories. 1900h.
Details from IEEIE 01 836
3357 ext. 212.
6 April
Component tv measure-
ments: colloquium.
7 April
Software engineering — the
importance of documenta-
tion: colloquium.
ELECTRONICS & WIRELESS WORLD
Round
Australia by
microwave
The commissioning of the last
link in Telecom Australia’s
$1 billion round-Australia broad-
band microwave network has
meant a significant improve-
ment in the security of national
communications in Australia.
Telecom Australia is the national
common carrier, owned by the
Federal Government and
charged with the development of
a modern telecommunications
system in Australia.
When the link across the West
Australian/Northern Territory
border was switched on recently,
it immediately became possible
to direct Perth calls to the east
coast of Australia, via the north.
For the first time any failure in
the main trunk route across the
Nullarbor desert no longer
meant Western Australia's com-
munications could be cut off
from the rest of Australia. Just as
importantly for people who live
in the remote Kimberleys in the
north west of Western Australia,
the 455km link that now joins
Kununurra to Katherine in the
Northern Territory has given
them additional security in the
event of a cyclone disaster.
Although the towers holding
the network's parabolic dishes
are designed to withstand winds
up to 225km/h. it is still possible
for a cyclone to put a dish out of
action. It happened with Cyclone
Joan in 1984, when high winds
twisted an angle-iron, and a dish
on а tower was edged 5? off line.
On a 40km line-of-sight between
dishes the 5? was sufficient to
break the link and bring the
network down for two hours
before the dish could be re-
aligned. The completion of the
final link means that such а fault
would no longer disable the net-
work; communications traffic
could be simply redirected
around Australia in the opposite
direction, away from the fault.
Communications Highway
One. asit is called, began in 1959
with a link between Melbourne
and Bendigo. At this time, some
areas were only connected by
telegraph lines and these were
being replaced by h.f. radio links;
allowing phone calls for the first
time to the Kimberleys, for ex-
ample.
The completed network car-
ries telephone traffic, computer
data, telex, facsimile, tv and
stereo sound broadcasts. И
stretches 11,916km in a giant
continental loop. To provide
line-of-sight communications,
the 303 masts are placed at 40km
intervals in a zig-zag pattern to
prevent. overshooting into the
next section. Repeater equip-
ment is housed at the base of
each mast. In the northern re-
gions where the temperature can
rise to 50°C, the repeaters are
buried in underground shelters
to keep the temperature stable,
to within 5°C of the required
ambient. Remote repeaters are
solar powered.
- William Scholes, Sydney.
Russians cease
jamming
Skywave jamming of the BBC's
Russian-language service all but
ceased on January 20th, and,
judging from reception in Mos-
cow, so too did local groundwave
jamming - much beloved of the
Soviet Union.
The jamming began in 1949.
since when jammers have been
turned on whenever the political
climate has cooled. 1963 marked
a temporary lull. but jamming
reappeared after the invasion of
Czechostovakia in 1968. Another
respite occurred in the 19705.
At no point have the Russians
ever openly admitted to jamming
the BBC; indeed last year the
Soviet ambassador to Britain
countered such accusations with
the charge that Britain was itself
jamming Russian broadcasts.
Just why the jamming has now
stopped is not known. It could be
ELECTRONICS & WIRELESS WORLD
a desire for better relations with
Britain following the visit to
Moscow of the Foreign Office
Minister, Timothy Renton. This
is given more weight by the fact
that (at the time of writing) other
western broadcasters are still
being jammed. The approazhing
1987 World Administration
Radio Conference may also have
some bearing. allowing the
Soviets to present a cleaner im-
age in terms of spectral pollu-
tion. Cr it may turn out to be
another step in Mr Gorbachov's
liberalization policy. alreacy de-
monstrated through limited
western access to the country's
print media. — JW.
Sinclair's Z88
Having sold the Sinclair brand
to Amstrad, Sir Ciive Sinclair
has started а new company.
Cambridge Computers. Its first
product is the Z88 computer; a
battery-powered lap-top which
comes with a built-in word-
processor, BBC Basic, spread-
sheet. database, calculatcr and
diary/calendar. 32K of ram is
provided but it is possible to
plug in up to three ram exten-
sion cartridges, of 32K, 128K
and (available later) 1Mbytes.
Eproms with the same capaci-
ties can be used in the same
way.
The display offers 8 lines of 80
characters with an additional
area in which every character is
represented by a dot mapoed to
given an overview of the page
layout. There is also a menu
indication and a status cisplay
for battery level. An RS232 out-
put to a printer is provided. and
the ability to transfer files to and
from an IBM-compatible PC.
EXHIBITIONS AND
CONFERENCES
24-26 March 1987
Cadcam 87 exhibition and
conference. NEC Birming-
ham. EMAP Int. Exhibitions,
Tel: 01-608 1161
Internepcon Production
Show and conference — 'from
CAD to testing NEC Birm-
ingham. Cahners Exhibi-
tions. Tel: 01-891 5051
25-26 March 1987
Instrumentation Bristol 87
Exhibition. Bristol Crest
Hotel. Trident Int. Exhibi-
tions, Tel: 0822 4671
31 March-2 April
Scottish Computer Show
and conference. Scottish
Exhibition Centre, Glasgow.
Cahners Exhibitions.
Tel: 01-891 5051
6-8 April 1987
Offshore computers confer-
ence and exhibition. Heath-
row Penta Hotel, London.
Offshore Conferences, Tel:
01-549 5831
13-16 April 1987
Acoustics '87 conference at
the Management Centre,
Portsmouth Polytechnic. In-
stitute of Acoustics, Edin-
burgh, Tel: 031-225 2143
28-29 April 1987
Cellular and mobile com-
munications conference,
Barbican Centre, London
Value-added network services
(VANS) conference. Barbican
Centre, London
12-15 May 1987
Automan: 4th European
Automated Manufacturing
systems exhibition and con-
ference. NEC, Birmingham.
Cahners Exhibitions.
Tel: 01-891 5051
17-20 May 1987
CES — Consumer Electronics
and Technology Show. Earls
Court, London.
Organized by Montbuild Ltd,
Tel: 01-486 1951
19-21 May 1987
South-Comm 87
Exhibition of the Association
of Sound and Communica-
tions Engineers. Business
Design Centre (formerly
Royal Agricultural Hall).
Liverpool Road, Islington,
London Nl. Batiste Exhibi-
tions.
Tel: 01-340 3291
391
Small Enclosures
i Boxes in Steel
Aluminium
and Plastic
UNIT 3, FOUNTAYNE HOUSE
ROUNTAYNE ROAD, LONDON N15 4QL
Tel:01-885 2884 Теіех : 296797
ENTER 56 ON REPLY CARD
TELESCOPIC (- MASTS | PYE SSB TRANSCEIVERS TYPE SSB210
| (NEW & BOXED) 60% OFF ONLY £480 EACH
Pye base stations, high band and low band AM type F401
used condition and untested to clear only £75 each.
Pye TVT 35mm slide colour telecine equipment, looks new
no details available, offers invited
Send for our government surplus catalogue.
Callers welcome by appointment only 9 am to 8 pm any day.
All prices quoted are for UK mainland and in pounds sterling
plus VAT P&P at cost.
B. BAMBER ELECTRONICS
5 STATION ROAD, LITTLEPORT, CAMBS CB6 1QE
TELEPHONE: ELY (0353) 860185
ENTER 55 ON REPLY CARD
@ Pneumatic
© Hydraulic Ram
Operated
© Winch Operated
50 YEARS OF EXPERIENCE
IN POWER CONVERSION
1937-1987
С] DC-AC Inverters (Transvertors)
Г SINE/SQUARE WAVE INVERTERS 30 to 2000
watts, 50 (or 60) Hz, 115/230V, single phase эк P m
| AC. From 12, 24, 50, 110 or 220 Volts DC U
Hilomast Ltd.
THE STREET - HEYBRIDGE - MALDON
ESSEX - CM9 ?NB - ENGLAND
Tel: (0621) 56480 Telex: 995855
Г] DC-DC Converters Battery Chargers
[_] AC-DC Power Supplies Standby/UPS Systems
С AC-AC Frequency Changers Line Conditioners
For details:
VALRADIO POWER LTD
LAWRENCE ESTATE, GREEN LANE, HOUNSLOW TW4 6DN, UK
Tel: 01-570 5622
ENTER 13 ON REPLY CARD ENTER 74 ON REPLY CARD
392 ELECTRONICS & WIRELESS WORLD
Programs 25 and 27 Series to 512K
2516, 2532, 2564, & 2716, 2732, 2764, 27128,
27256, 27512 in CMOS & NMOS
Uses FAST Program Method.
Covers all Program Voltages.
Liquid Crystal Display shows EPROM type.
Program-Method and Program-Voltage which are set by switches
also RS232 setting if present
Two Key operation: START & RESET - pretesting is automatic
G8 reports non-blank EPROMS and correctly programmed ones.
A CHECKSUM is reported if you press both keys - six hex digits
Audible output keeps you informed - you don't need to watch it
Option - A metal Case instead of a plastic case if you prafer it
Option - A Bi-directional RS232 Serial interface to upload
and download INTELHEX. MOTOROLA S, TEKHEX, ASCII and
BINARY files
GANG-OF-EIGHT
for RS232 option
for Metal Case
£395.00
add £50.00
add £35.00
Z80 Program
Development Aid
On your TV screen you display program, registers and stack,
using MENTA's custom assembler you write 280 code and try it out
An excellent int'oduction to uP programming! Designed fcr the
School's Council to teach microsystem design, MENTA is a
microcomputer which can form the basis of an industrial-controller
or robot. TV DISPLAY - FULL SCREEN EDITING - ММЕМОМІС CODE
ENTRY - FAST CASSETTE INTERFACE SIMPLE DEBUGGING
SINGLE-STEP ОВ FULL-SPEED EXECUTION WITH OR WITHOUT
BREAKPOINTS - DISASSEMBLER (to external printer-term nal)
24 LINES FOR INPUT/ OUTPUT . GOOD MANUAL WITH EXAMPLE
PROGRAMS. CIRCUIT DIAGRAM and FULL COMMENTED SOURCE
CODE LISTING. Teaching modules are also available - Universal
Buffer, D to A. A to D. Motor control, Variable and Switched inputs
and outputs. together with Pupil Readers, Teacher's Guide and
Worksheets
MENTA with power-supply & leads £9 2
ENTER 16 ОМ REPLY CARD
ELECTRONICS & WIRELESS WORLD
Portable uP Bus Tester
An engineer needs more than a meter and a scope - tnese tools are
hardly adequate for diagncsing faults which afflict uP systems
SuperDOC is а diagnostic wool which you plug into the socket where
the uP goes; using “he handy probe you can identify address, data
and control lines in the LCD display. You can edit and keep up to
225 tasts, stored in battery- backed memory and apply them to
faulty boards. Each test prc duces a report on the built-in 24
column printer: VEMOR Y MAP - BUS SHORTS - CHECKSUM
RAMTEST - MEMORY READ - MEMORY WRITE - FILL MEMORY
INPLT - OUTPUT - ASCII PRINTOUT - HEX PRINTOUT SEARCH
DISASSEMBLY in 1302, 8035, 6800, 6802, 6809, 6502 or 280
mnemonics. Super2OC comes complete with a personality card for
each uP, which con“igures the probe correctly
SuperDOC complete as above
SuperDOC supporting only 280,
6502, 6800 & 8085
£330
£295
Bare PCB and Cable
Connectivity Testing
We offer a system of CMOS custom-chips and a micro controller
саг 3, designed by DATAMAN. Using these electronic сот зопеп!ѕ
you can put together your own Bare-Board Tester or Cable Harness
Tester for much bess than £ 1 per point, with no practice! limit on
size. We can also supply a complete system, with Bed-of-Nails
fixture, ready to use. Tellus your requirements. Ask for a cuotation
and literature
Olivetti Typewriter ET221
Interfaces
We can convert your ET221 to a serial or parallel ccmpute: printer
with contro! of boldtacinj. underlining, justification etc. The price of
а s ngle conversion includes collection and delivery (A mach
lower price for a tulk order) £195
EPROM Erasers from £39
Dataman
Lombard House - Cornwall Road
Dorcaester. Dorset DT1 1RX
PHONE 0305 68066
TELEX 418442 DATAMN G
Postage is free on orders over £100
BUT please add VAT in U.K.
Terms eheque with order or credit-card.
Money Refund Guarantee - 14 days, no questions
393
Forth processor
hardware
Using the Novix processor relatively few devices are needed to
make a complete Forth computer capable of at least 4 mips.
у first article on the Novix №4000
M in the February issue outlined Novix
architecture and design philosophy.
This article illustrates how to design Novix
based hardware, looking at the criteria that
determine its design, and describes a
working system. This design is the basis of
the NX4 board, a low cost Novix evaluation
system.
A number of factors determine which
components are used in a microprocessor
system — timing diagrams, memory map,
amount of rom and ram needed, choice of
technology, and so on. But before exploring
these in detail, we need to put together a
brief specification for the system. The aim is
to produce an evaluation system that will
give engineers an idea of the NC4000's
capabilities. The main key requirements in
no particular order are
—Low cost
— Use of readily available parts
—Highest possible performance
– Minimum component count
— Serial i/o (RS232) for interactive
programming
Some of these criteria are mutually in-
compatible (e.g. low cost versus speed) but I
will explain how to get the best performance
from the NC4000 for any particular com-
bination of devices, whether they he ram,
eprom or i/o.
The board can be used as a complete Forth
development system by connecting its
RS232 port to a computer (an IBM PC or
compatible) which is then used as a terminal
and pseudo disc drive, Fig. 1. Software,
including the serial-link handler, Forth
compiler and keyboard interpreter for the
NC4000. will be in eprom on the board, and
will be explained in the next article on
software. However, there are one or two
unavoidable forward references to the next
article made necessary by software charac-
teristics that have an impact on the hard-
ware such as reset address, interrupt vectors
and program space.
TECHNOLOCY CHOICE
As the NC4000 is an нсмоз device. it will drive
bipolar devices (standard, s, 15 and F series
t.t.l.), sos and, of course, other cmos de-
vices. Problems are only likely to occur if a
bipolar output has to be read by an NC4000
input since нсмоѕ inputs switch at below 1.5V
and above 3.5V whereas t.t.l. input
thresholds are 0.8V and 2V respectively. To
394
WILLIAM WATSON
RS232 link
Forth program NX4
for RS232 link single-board
disc and terminal Novix computer
emulation
Fig.l. Low-cost NC4000 development. The NX4 board is ideal for stand-alone real-time
applications, but also allows interactive development of those applications. Forth PC
software configures the host computer to act as a terminal and disc drive, all down the
one serial line, for the NX4 Board.
Fig.2. The memory map determines some of the eprom and ram mapping. п this design,
the eprom is mapped into the middle of the ram, which can be expanded up to 24K words
by replacing the 8Kbyte with 32Kbyte devices.
Extra paged data
using Bor X port
FFFF
Data space
only
ке ——- —— — B000 ——————
imit of
п Lm On board ram
expansion area
| 4000 ——————
| 4K ram
3000 ——————
| 8K eprom
—— 1000 —
Free for
experimentation
Program
and data
space
Processor reset
address,
Int t vector
тешр еш 0020
| &К гат
ELECTRONICS & WIRELESS WORLD
Low-memor y
variables ——_ 0000
NC 4000 NX% board
memory map memory map
Main address and data bus
т. 65 | "T аер UE:
Ta 35 Clock *
Main address and data bus
= =e
Та 40 мата у *l
Tar 75 | —
T 60 Address lines (A) ;
wede —
Twean 45 _ == Tas ly
] —
Data ouput (D)
А =
1/0 ports |—— — —»| ms
—— Tursan
T, 95 Main memory WED F
T. 100
y
Tett 50
Т.п 35 X and В port i/o bus
liri жа >. Ta m oe кыым]
——
Data stack bus X port ор X
T 75 ?
fig a amam
Ton 35 en ae Ld
T,. 45 B port o/p
um 50 Mg =
Twesh 40 _ 1/0 port WEB /
T 30 Parameter or data statk bus
T. 35
Т 30
ей 35
40
==
Data stack data(S) ^
P ЖЛ
Data stack WES N /
Return stack bus
Ts
ucmos bus drivers on-chip so extra bus . Е ева В
buffering is only required in exceptional Return stack ШО, Ж
circumstances. It is possible to load the те
address lines of a4MHz NC4000 system with ттт "БЕЙ
<500 and >300pF. Resulting output drive
voltages will be within 1.1.1. and нсмоѕ vol- т len
Return stack WER
tage levels, and the system will still function
satisfactorily. The combination of the
NC4000's relatively low clock speed (com-
m “iho pury me Le pa үн Fig.3. These timings in nanoseconds are average values based on devices with a T,, of
technology and its bus drive capability а! 65ns. Shaded waveforms represent an indeterminate transitional period. Two important
figures are T,, and Ть.. Time T,, needs to be ready early to give as much time as possible
for memory decoding. Time Тк. has to be subtracted from overall cycle time to give the
access time required for parameter (data) and return stack rams.
help to reduce noise.
NX4 board specification
For the application described here, stan-
dard components are used wherever possi
ble. However. memory decoding is done in
‘fast’ t.t.l. to leave as much time as possible
NC4009P
8K words (16K bytes) eprom
8K words (16K bytes) static ram
Separate parameter and return stack rams
for memory access.
Average 4MHz (>4, and can be uprated to >5 mips)
One serial port (RS232),
Novix 16bit B-port and 5bit X-port
On-board memory expansionto 24K words (48Kbyte).
Access to all Novix bus signals (except for stacks) provided on 64-way
DIN 41612 connector pads.
Single-width Eurocard
0.5A with on-board 5V regulator
cmFORTH in Eprom on the board, 5% in floppy disc for IBM PC/MS-DOS
solve this problem, it is only necessary to
interpose an nct buffer to perform level
conversion. Usually Nwos and cmos memory
devices have their outputs specified as being
t.t.l. compatible, but they are also implicitly
исмоз compatible.
Output lines on the NC4000 come from
CIRCUIT OVERVIEW
The №4000 is a true l6bit processor so
byte-wide memory devices are used in pairs.
All addressing is in 16bit words, whether for
program rom, ram or the two hardware
stacks. As you can see from Figs 4, 5 this Speed
means a minimum of eight memory devices. 1/0
Two eproms, ICs 9, contain а Forth oper-
ating system/development environment
with plenty of room for expansion as over
half of it is unused. Main memory ram is
provided by IC; 4. As shown, the board has
8K words (16Kbyte) of ram but, by rearrang-
CPU
Memory
Expansion
Size
Power
Sottware
ing some jumpers in the decoding and
changing the 8Kbyte for 32Kbyte rams, all
the memory space not already occupied by
eprom can be populated by ram.
The parameter stack uses the bottom 256
locations of two 2Kbyte rams IC; за as does
the Return Stack, IC;;;5. Including the
ELECTRONICS & WIRELESS WORLD
type host such as Amstrad PC-1512 with
— Full source code for cmFORTH, utilities and demonstration,
— Compiler to produce rom-based applications,
— Forth Editor to run on PC host.
— Terminal and disc emulation (for board) to run on host,
— Documentation
395
ICg(part)
NC4000
со {о [осо
llis
41612 ЛА |^
conn 13N 108
24а 13M loc |
24b " mm
Ba CN
75 a |
— 13K
13)
26b
12H
ж aG 2M
NIS
28а = mm
28b "
= к
120
29b WB
30a m 16 0
QD
128
- ИЙ
s M ho |
в
10L x
zb в |
с |
4C
6A Clock
18
8A RESET
D- Data bus
A- Address bus
Fig.4. NC4000 processor main memory eprom and ram.
№4000, this already accounts for nine of the
17 i.cs used. The remaining eight are for
generating clock signals, decoding and
RS232 buffering.
All major Novix signals, except for the data
and address buses for the two stacks, are
brought to a 64-way DIN connector, PL), so
that additional hardware can be easily added.
The speed of the 4000 makes it suitable for a
number of applications including audio pro-
cessing, vector graphics, robotics and com-
puter vision. For maximum i/o throughput
you will want to use the two on-chip i/o ports
(B and Xport) but the main memory data,
address and write-enable lines also allow you
to add extra memory or memory mapped i/o
devices.
Referring to Fig.6, the 74F138 decoder
selects memory in 4K pages, and the subse-
quent And gates then give the optimum
mapping of eprom and ram. It also uses the
low part of the clock cycle to enable the
chip-select outputs (07) as a means of
396
synchronizing the memory access part of the
№4000 instruction cycle with the actual
memory devices. This section of the circuit
also shows the switched-frequency clock
generator which can be made to adapt to
different memory access times, of which
more later.
Power, reset and RS232 drivers are shown
in Fig.7, and do not need comment, except
perhaps to note the use of a spare Or gate to
givean external reset line on connector PL,.
NC4000 MEMORY MAP
On Figure 2, the memory map of the
NC4000, there are five key points to note.
Our first article described how the NC4000
uses bit 15 to denote a ‘jump-to-subroutine’
instruction with the remaining bits giving
the destination address. The compiler effec-
tively includes a value (the address) as part of
the machine code instruction.
In the same way, the compiler can recog-
nize short literals and addresses below 2016
and compile them with other Forth actions.
As a result there is а scratch area from 0 to IF
that can be written to or read from in one
machine instruction taking, in this case, two
clock cycles.
Variable reading or writing normally takes
two instructions and four clock cycles, so
these low-memory variables are very useful
for time-critical code. One way to regard
them is as 32 off-chip scratch registers. This
part of low memory clearly needs to be ram.
More of these time-saving software details
are discussed in the next article.
The next landmark is 206, the location to
which the processor jumps when it receives
an interrupt. As interrupt code can be held in
ram or rom, it has no impact on the
hardware design — it will almost certainly be
a continuation of the ram used for low-
memory variables.
Prototype versions of the 4000 series,
designated 4000P, have a fault in that they
ELECTRONICS & WIRELESS WORLD
Parameter stack
K7 WES
2M 1 3K 1.3) 1 3H 6B I 5A | ААТ 4B 12A
1M | IL | 2J | 1H 6С | 5B | 5C | ЗА
9 pon 31415 (117 +5 +5
Stack С
NC 4000
Ра)
X4X3X2X1 X0
Fig.5. Stack ram and Xport hardware for the NC4000 processor.
Return stack
—e Ris INT
iF | 2E | 1c | 28 6NI MI 8N nM nk! d nn éL: SNI SL 1 ЗМІ а. 13F 412E 10301 13A. [7А
3F | 3E | 30 | 38 6M | 8M 12M | 13L | 12) | 13H SM] 4M | 4N | 3N ИЕ [E 111D | 12A L 105
9 [ro |n [r3 [14 [85 [e [17 s on [уз 1451617 +5 *5
Ag 8 8
EZ PP № № 7|
ЕТЕТ S
41612
19a
19b
20a
20b
will not correctly interrupt multi-cycle in-
structions. Use can still be made of the
interrupt structure but a software routine is
required to support its operation.
The address to which the processor jumps
at reset comes next at 1000), and will almost
always be the start of rom or eprom. The
reset address is on a 4K boundary which is
inconvenient given the ready availability of
8Kbyte ram/eprom devices. Using 6264 rams
and 2764 eproms, the solution is to map the
lower 4K ram from 0 to FFF, eprom from
1000 to 2FFF and the remaining 4K ram
from 2000 to 2FFF.
This is quite easily done by adding some
And gates to the decoded outputs of ICs.
Referring to Fig.6, о. feed the And gate
which generates the eprom ОЕ signal.
However Aj? is inverted at 1000 (а, active
on ICs) so an inverter has to be inserted on
line д; between the NC4000 and the eprom,
Fig. 4. This provides linear addressing
between 1000 and 2FFF.
Because the jump-subroutine address
range is limited to 15 bits, program space
has to be below 32K and it makes sense to
keep that area full of ram and rom. To make
full use of this part of memory, the circuit
has an expansion capability of up to 24K
words of ram.
Links ix; of Fig.6 allow you to select
addressing for 6264 or 62256 type devices.
Circuit ICjg maps the relevant о outputs
from ICs to give a cs for the 62256 option.
processor can still read and write above
8000, and this area is useful for data,
tables, i/o devices and so on. If a full 64K
words (128Kbyte) is insufficient, data
storage can be vastly extended by using the
Xor Bports to page in further 32K pages.
ELECTRONICS & WIRELESS WORLD
TIMING
A necessary area of study for any new
processor is its timing diagram. The
NC4000's appears to be complicated by the
fact that there are four of them, one for
each bus. However, each bus is easy to
understand once you realize that everything
is timed from the rising edge of the clock
input.
Figure 3 shows how all the signals relate
to the external clock applied to the proces-
sor. As the clock goes high, the №4000
latches any input data or program instruc-
tion, so outputs from ram, rom or i/o need
to be held stable at this time (about 5ns).
Propagation delay through memory decod-
ing and deselect delay from standard rom
and ram devices is enough to cover this. In
fact, the address buses are all stable for a
further 30ns.
The chip then carries out internal actions
at maximum speed. Any output lines, for
example main memory address and data
lines, become available on the chip's pins
the moment they have been generated;
internal latching would produce delays and
impair the chip's performance. There is a
period of transition from the previous to the
new values and these are shown as unspeci-
fied on the timing diagram. The most
crucial time on the diagram is Tas since
decoding for the next instruction can begin
as soon as it is stable. Having the data ready
1015 after the address is fine as a memory
device needs to be decoded and addressed
before data can be applied to it.
Upon receiving the falling edge of the
clock the NC4000 carries out no further
actions. Instead, the designer must use this
part of the clock signal to synchronize
decoding, chip selects and so on, since the
lower part of the clock cycle is for memory
access only. You can see from the circuit
that this synchronization is done by one of
the se inputs to ICs.
The clock must be generated externally,
and arranged so that the upper part of its
cycle is at least T,, (65ns) long, equivalent
to 7.5MHz. Running the clock with a 1:1
maik-to-space ratio at this frequency leaves
Special offer
OX6 7XT.
contact Comsol.
The NX4 board has been specially designed to accompany this set of articles and is available
fully assembled and tested, with circuit diagrams, software and documentation. Availability is
subject to stock and you should allow 30 days for delivery. Please send cash or cheque for
£286 (fully inclusive) to NX4 offer, Golden River Ltc., Churchill Road, Bicester, Oxfordshire
For this offer, Novix has supplied 300 chips at a special price; the one-off price for the
NC4000P alone is normally £205. Consequently numbers are limited and only one board can
be supplied per order. This offer is available within the UK and Eire. Overseas readers should
Enquiries about the kit, chip and associated software should be made to Computer
Solutions Ltd at Canada Road, Byfleet, Surrey KT14 7HQ.
397
only 65ns for the decode and memory
access part of the cycle — realistically only
50ns after 10-15ns has been subtracted for
decoding. While this frequency could give a
computational performance in excess of
eight mips, 45ns ram and rom are not yet
widely available and are certainly not cheap.
A low cost design forces use of lower
frequencies.
If you now look at the lower part of the
cycle and choose, say, 250ns as a practicable
access time for readily available eproms, the
clock cycle time goes up to 2х(250+15)=
530ns, or just under 2MHz, giving 2.4 mips.
This represents a performance of around
three times better than a 68000 program-
med using assembly language and running
at 8MHz, but it is still slow by Novix
standards.
Somewhere between lies the ideal; by
arranging a suitable mark/space ratio to the
clock, the processor and memory can each
be made to work at near-optimum efficien-
cy. This clock waveform could be produced
by Anding the clock signal with a delayed
version of itself. Ап alternative is to use a
high clock frequency and then divide it with
a 74HC4017 counter, icy.
By connecting one of the counter outputs
to the master-reset line, it is possible to set
up a suitable mark/space ratio. А 15MHz
clock gives a convenient clock pulse of 67ns,
and a division of five puts the lower part of
the cycle at 266ns.
Further optimization is still possible. Us-
ing a few extra components it is possible to
reset IC, using a cs line to give a mark/space
ratio which adapts to the speed of the device
being accessed. A standard crystal oscillator
feeds the clock input of the counter, IC,.
Addition of an Or gate and two And gates
allows the decoder to select the appropriate
output to reset the counter and give the
correct mark/space ratio for rom or ram. The
Or gate has a spare input which is tied low.
This can be used in conjunction with exter-
nally generated chip selects and the i/o clock
signal to give a suitable access time for
slower i/o devices.
Effective memory access time is, of
course, reduced by any decoding delays
there may be. In this design, decoding takes
place through 1С; ›, with a total delay of
about 12ns. The counter gives the following
net memory access time for its outputs after
decoding delays are subtracted.
Output stage Access time
121ns
188
254
321
388
466
533
o/c 600
COOnA NAW
This scheme allows a free choice of ram and
rom access times. Outputs three and five
provide convenient times for 120ns rams
and 250ns eproms, giving 5 and 3MHz clocks
respectively. Accessing any device outside
the board's memory map without putting a
walt signal into the Or gate causes a default
to the slowest cycle time of 600ns.
The NC4000 is entirely static and its clock
may be stopped at any point in its clock
cycle. If it is a few nanoseconds after the
398
A13
Аң,
А15
м.
| Address
bus
IC,
HC4017
74 F 138
Stack CS
Ciock
21а
41612
conn
Io clock
1a
Unused ttl inputs
tied high =
Rom ОЕ
C7
Cae
1С15
МАХ 232
x decoupling
Ext. reset
7
+10V
Fig.7. Power supply, reset and RS232 port hardware. The Maxim 232 produces RS232
levels from a 5V supply.
ELECTRONICS & WIRELESS WORLD
Address bus
Clock
Wait _Ag Ay Az SE
d ЕЗ Th Е 138
5 o 201 00
А КО Бра О aum -
LNSCN EX
Novix data bus
Dg 045 08 015
OE %HC37%% CK JOE нз» CK OE %HC37%% CK OE 74HC37% CK
07 m "vv
Do Do 045
0АС1600 JP-V
76 НС 04 16bit d-to-a
Analogue out
12-bit inverted data
Do
ADC 80Н-АН-12 __
Fig.8. Connecting a-to-d and d-to-a converters to тат
memory. The d-to-a converter is mapped to 8000,6, the
a-to-d converter to 8800,6. Latches decouple the converter
from the NC4000 so that software has only to read the data
at 8800, and the next conversion is automatically initiated.
The analogue-to-digital converter is 12bit so the top four
А0585
Analogue in
Start EOC
124 a-to-d mE
Sample
input bits are connected to ground.
and hold
rising clock edge the c.p.u. completes its
internal operations and then stops. Halted
like this, the processor draws around 504A.
STACK HARDWARE
Figure 5 shows stack hardware. Data stack,
IC узла, and return stack, ІС 11.12, rams do not
require any decoding as the stack address
lines only access the bottom 256 cells. Their
timing depends on the shortest memory
cycle time taken elsewhere in the system,
e.g. when addressing program ram.
Referring to Fig.2, the longest time taken
to output a valid stack address is Tks, or
about 75ns. Using a 5MHz clock the lower
part of the clock cycle is 133ns, so the clock
signal itself can be used to drive the ram
select lines using 120ns-access devices. Note
that the stack rams are accessed almost
every clock cycle; standard nmos devices can
be quite warm under these circumstances.
INPUT/OUTPUT
An important feature of the NC4000 is its i/o
capability. There are 21 programmable on-
chip i/o lines arranged as a 16bit port (Bport)
and 5bit port (Xport) with separate mask and
data direction registers for each port.
Ports X and B are useful in that they can
often be used to replace other hardware,
with consequent reduction in component
and manufacturing costs. In this design port
В is uncommitted and is available for experi-
mentation. You may decide to use it for
ELECTRONICS & WIRELESS WORLD
analogue/digital conversion or to extend the
data storage space. The Xport gets used for
two separate functions : serial i/o and multi-
tasking hardware support.
There is no uart chip in this design – none
is needed. The Forth system supplied in
eprom uses one X-port line for serial input
and another for output to form a software
uart. During development, the serial line is
used for communication with a host compu-
ter such as an IBM PC, which in turn is used
as a terminal and disc drive for the Novix
board, Fig.l. Software to handle this is
discussed in the next article; it is only
necessary to say that for such an arrange-
ment, a software-uart serial link is adequate.
If you refer to Fig.4 you will see that Xport
lines 0 and 4 are used for this purpose. Lines
rts and crs are included even though the
software supplied on rom does not use them.
The only restriction to a software uart is
that it limits software using the serial line to
single-tasking only. So what hardware is
required to support multi-tasking? First, for
any application that involves serial data, you
will have to add a serial device to the
hardware so that data can be transmitted and
received independently from the c.p.u. Next,
the NC4000 needs to have separate para-
meter and return stack areas for each task.
Now it is perfectly feasible to run more than
one task in 256 words of parameter and
return stack, but the software for each task
may have to be restricted.
À better scheme is to give each task its
own protected parameter and return stacks
by selecting a different area of ram. Three
Xport i/o lines are available to do this, giving
eight separate hardware task areas, neatly
fitting into the 2Kbyte ram chips. As shown,
the circuit is set up for just one task area (as
is the software supplied in eprom), but the
patch area LKs between the Xport bus and
the Stack rams allows this to be done if
required.
Adding extra hardware to the main mem-
ory bus is straightforward. Figure 8 shows
how to add standard a-to-d and d-to-a con-
verters to the memory map, which are useful
for processing such as audio frequency ana-
logue signals.
CONCLUSION
The NX4 board illustrates how to design
Novix-based hardware. A number of im-
provements could be made, such as adding a
proper uart and reducing component count
by using pals or e.p.l.ds to replace decoding
and clock hardware. Further component
reductions will be possible as 16bit-wide
memory devices become more readily avail-
able. Even with current components a
minimal system need only consist of ten
devices: two roms, six rams, a clock and an
NC4000.
À description of supporting software (a
small, but complete Forth development en-
vironment including a compiler for produc-
ing rom-compatible code) will be given in a
subsequent article.
William Watson is with Computer Solu-
tions of Byfleet, Surrey.
399
400
BUD
!
Ш
177 1
11 П
— "E.
{
ns
VH
HA
И d
i
тт
У i! /
m
tn
[ЇЇ
fi
(€: ee — —
ei ее. Copies of the 1986 Frequency Wall Chart. |
Each wall chart IS рисед at £5.75 ( including VAT)
| enclose my Cheque; Postal ог der fo, A ease то WES Payable to Reeg Business Publishing Lid
Li Please debit m Credit ü j Circle) VI /ACC /D |
Му card number, т LITT I] AI
У Card COLLIER Signature M i |
Cc c ——Ó
Е ад i ӨШ —+
Ease return this form MD pameng tc -= =
Electronics & 'reless Иона =a
Puting Posting Ltd, —
120-126 Lavender Avenue Mitcham —
Surrey CR4 ЗНР — —
am
А SS МОК
CTRONICS & WIRELE
ELE
= 7
D WA
Conguin Software Limitec
Freepost, Morden, Surrey SM4 1BR Telephone: 01-640 9130
QUICKPAD
The low cost solution to PCB design
contact us now for full information
ENTER 77 ON REPLY CARD
SPECTRUM ANALYSERS
HP8558B 1 to 1500MHz 182T Frame #5000
НР141Т 85541 8552A 1250MHz £5500
HP8551B 10MHz 40GHz £1500
HP8755A 10MHz 18GHz £750
Tektronix 491 1.5-40GHz £1350
OSCILLOSCOPES
Tektronix 465 100MHz DL Sweep £750
HP1741A 100MHz Storage £1500
HP180A 50MHz DL Sweep plug in £550
HP 183A 4 Trace SOMHz £850
НР182С 75MHz 1825А Time base £1250
Telequipment D83 50MHz DL Sweep
£325
Cossor CDU150 Dual beam 35MHz £175
Philips PM3233 10MHz £195
Various HP plug-ins in stock phone for
details
GENERAL TEST EQUIPMENT
HP8620A 1-2GHz 5.9-9GHz
8-12.4GHz £5000
HP8620A Sweeper 8-12-4GHz £2750
HP333A Distortion Meter £550
HP6544A Test Oscillator £750
Radford DMS 3 £350
Radford LOO2 DMS2 Pair £375
Marconi ТЕ2120 Wavtorm Gen £250
Wavetek Programmable Wavetorm
en £450
Marconi TF2331 Distortion Factor
Meter £425
HP400EL AC Voltmeter £200
HP3400A RMS Voltmeter £450
HP3406A Sampling Voltmeter £575
Racal 9903 Counter Timer £200
Racal 9917A Counter £385
HP3311A Function Generator £295
HP5381A BOMHz Counter £175
Wavetek 1001A 200MHz Sweeper £275
Marconi 2300 Modulation Meter £375
Marconi 2330A Wave Analyser £425
Gen Rad 1362 UHF Osc 220 920MHz £295
Gen Rad 1264A Mod UHF Osc
450-1.5GHz £395
Racal 9082 Signal Generator £1500
Marconi TF2012 400-520MHz AM FM £375
Tel: 0532 435649
M & B RADIO (LEEDS)
THE NORTHS LEADING USED TEST-EQUIPMENT DEALER
Marcon! TF 144 10Hz 72MHz
£75
Marconi TF1060 450-950MHz AM FM £195
Marconi TF 1066 10-470MHz £250
Philips PM5324 100KHz 110MHz
Sweep £350
Tektronix 521 Pal Vectorscope £1850
Tektronix R141A Colour Bar £850
Thorn TV Sync Generator £550
Tektronix 529 Waveform Monitor £250
Bradley 171B Multimeter Cal £850
Marcon: TF 1026 Freq Meter 5-1GHz £35
HP415D SWR Meter £250
Lyons PG73N Pulse Gen £250
Marconi TF 2212 X-Y Displays £65
RS Poly Scopes 2 5-1.2GHz £185
Marconi TF 1313A Bridge £450
Marconi TF2700 Bridge £195
Marconi TF2701 insitu Bridge £185
Marcon: TF1245A TF 1246 1247 £575
HP419A DC Null Voltmeter £150
Fluke 6160A Synthesizer 30MHz £275
MI Sanders No 19 Attenuators £95
Eddystone EC958 10KHz 30MHz £450
Eddystone 830/7 Recewers £350
Racal RA17L 117 etc from £175
Nagra ill Tape Decks £450
Uher 4000L Tape Decks £85
Racal 9056 Selective Analyser £250
Philips PM81 10 Mini Recorder £250
Hitachi HV62K CCTV Cameras £85
Brandenburg 807R 30KV PSU £150
Philips 1649 PSU 150У 7A £250
HP6453 PSU 0-15V 0-200A £500
Marconi TF2019B Noise Gen £235
Marconi TF2092C Receiver £450
Various Wandel & Golterman Line Test
instruments in Stock eg: Levell Generators
SPM6, Level!
Generators PS3
Meters
MISCELLANEOUS
Hars 1KW FM Broadcast
Transmitters
5KW VHF Dummy Loads
SPM 12
Signa!
£5500
£200
Ruston Diesel Alternator sets designed for
remote and unattended operation. 62КУА. 3
phase. 1000rpm, turbo charged as пем. POA
ALL PRICES PLUS VAT AND CARRIAGE
86 Bishopgate Street, Leeds LS1 4BB.
ENTER 70 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD
E M S Power Systems
EMS manufactures DC Power Supplies and
Battery Chargers both linear and switch mode
in a range from 5 VA to 3.2 KVA.
Also a complete range of Standby, UPS and
Mains Stabilizer Systems 35 VA to 1 KVA. EMS
specialises in the manufacture of customised
products and has a full design and
development facility.
EMS (Manufacturing) Limited,
Chairborough Road,
High Wycombe,
Bucks HP12 3HH.
Tel: (0494) 448484
ENTER 22 ON REPLY CARD
401
From a comprehensive
work-station to quick test sockets, Global's
breadboarding products lead the world in quality
and design. Just look at the specification of the
PB503 analogue/digital station— 100kHz
function generator, triple power supply, large
breadboarding area, logic indicators and many
other vital features for only £235.00 (plus VAT).
АН Global breadboards are guaranteed for life.
ИТҮ GO TO THE ENDS OF THE cant И
GLOBAL
SPECIALTIES
An Interplex Electronics Company
Global Specialties (UK) Ltd., Dept 13-2BB,
Shire Hill industrial Estate, Saffron Walden,
Essex СВИ ЗАС Telephone: (0799) 21682.
Telex: 817477 GSC LTD. Fax: {0799} 28146
ENTER 69 ON REPLY CARD
10 OUTLE A compact mains-powered unit with one
balanced input and ten a.c. and d.c. isolated
floating line outputs
* Exemplary А.Р. breakthrough specific
AMPLIFIER 4 ations giving trouble-free operation in
close proximity 10 radio telephones and
links
ч þa * Excellent figures for noise, THO, static
and dynamic IMD
* Meets IEC65-2, BS415 safety and І. В.А
‘signal path’ requirements.
Versatile, low cost, development systems
offering a choice of powerful multi-tasking
Also available as a kit of parts less the case
and all XLR connectors for one or ten
outlets
Broadcast Monitor Receiver 150kHz-30MHz
* Advanced Active Aerial 4kHz-40MHz *
Stereo Disc Amplifier 3 and 5 € Moving Coll
Preamplifier ж Illuminated PPM Boxes ж
PPM Drive Boards and Ernest Turner
Movements * PPM5 20 pin OIL hybrid *
Stabilizer and Frequency Shifter Circuit
disc operating systems. Available as board
level, dual floppy or Winchester plus floppy
configurations.
® 68000 microprocessor, 8 Mhz operation
® 512K dram, 128K eprom, 64K static ram
* 640x500 full colour graphics
* 80 24 character full colour text
* Dual 80 track dsdd floppy disc drives
® 20 Mbyte Winchester disc drive
© Two fully programmable serial ports
* Up to 48 parallel input/output lines
* Real time clock calendar — battery backed
* OS-9/68000, TRIPOS 3, CP/M-68K, STARDOS operating
systems
Board only — double eurocard £650
Dual floppy built system £1195
Winchester + floppy built system £1895
‘Micro Concepts |
2 St Stephens Road - Cheltenham - Glos GL51 5АА
Telephone: 0242 510525
ENTER 28 ON REPLY CARD
402
Boards ж Peak Deviation Meter ж Pro-
gramme and Deviation Chart Recorders ж
Stereo Microphone Атрійег * Stereo
Coders * Stereo Digital PPM
SURREY ELECTRONICS LIMITED
The Forge, Lucks Green
Cranleigh, Surrey GU8 7BG
Tel: 0483 275997
of Z4 EOS LNB's, LNC's, FEED HORNS,
VS ү © ANAS, ANTENNA POSITIONERS,
се? ene ZCOROTORS, LINE AMPLIFIERS, ETC.
For further details contact
24“ HARRISON ELECTRONICS
Century Way. March, Cambs. РЕ15 80W Тег: (0354) 51289
ELECTRONICS & WIRELESS WORLD
DHSS orders
Plessey ISDX
The Department of Health and
Social Security (DHSS) has
placed an order, worth around
£3.3m, with Plessey Com-
munication Systems (PCS) for
ISDX, digital private telephone
exchanges. This, the largest in-
dividual ISDX order that Plessey
has received, is for 57 systems for
DHSS offices all over the coun-
try. The systems range in size
from 48 to between 300 and 400
line capacities. Included in the
price was a ten-year main-
tenance contract.
The DHSS is currently under-
taking a three-year moderniza-
tion programme. Its new net-
work marks a change in telecom-
munications policy — purchasing
instead of renting. One of the
requirements for the new net-
work is to be able to switch
64Kbit/s ‘voice and data. This
order, according to Plessey, in-
cludes some 6,700 extensions
and accounts for around 14% of
the new exchanges required.
Where there are digital trunks,
DPNSS (digital private network
signalling system) is used to link
exchanges and a newly intro-
duced facility known as RAS II
(remote access system) will aid
maintenance.
RAS enables an ISDX to dial
automatically a special tele-
phone number in the event of a
problem and connect with the
PCS National Computer Aided
Service Centre at Nottingham.
Once the telephone exchange is
in contact with the computer,
the two machines can analyse
the problem, and very often cure
it, without human intervention.
Should the problem require the
attention of an engineer, staff at
the computer centre can deter-
mine whether the problem can
be resolved remotely or whether
an engineer must be despatched.
NATO’s new
satellites from
BAe
British Aerospace (BAe) has won
the contract, worth in excess of
£100million, to supply two com-
munications satellites for NATO.
They will provide secure military
and diplomatic communications
and be virtually identical to the
UK's armed forces Skynet 4
series currently under construc-
tion by BAe and for which Mar-
coni supplies the payloads. Sky-
net 4 services are voice, data and
telex to and from naval vessels
and fixed and mobile land ter-
minals.
Designated NATO IV, the first
of the new satellites is to be :
launched in the early 1990s. The
previous NATO satellites were
built by US company, Ford
Aerospace.
Telecomms and
IT converge at
Northern
Telecom
Northern Telecom has merged
its Communications Systems :
and Data Systems divisions in
the UK, the aim being to enable
the company to provide a better
response to market demands for
converging voice-and-data net-
works.
Norwich Union
gets distributed
digital dealing
As part of its new £800,000 tele-
communications upgrade, major
insurance company Norwich
Union will be one of the first
geographically remote financial
dealing rooms to be connected to
BT's City of London Dealer Inter-
link exchange. Users of this ex-
change system can have their
digital private wires patched
through a central exchange at
Moorgate in the City so that
circuits can be added or re-
allocated rapidly to match
changing business patterns.
The network is based on a
Thorn-Ericsson MD110 digital
PABX and handles 2976 exten-
sions plus 267 trunk lines and
private wires. It consists of a
main exchange unit at its head-
quarters building in Norwich
together with two remote sites in
Norwich and one in London to
handle dealer traffic. The private
circuits are connected to
Norwich Union's own London
PABX and then routed through
the new corporate network to the
Norwichdealing room
ELECTRONICS & WIRELESS WORLD
Dealers are equipped with 36-
key Thorn Ericsson Courier
digital programmable tele-
phones. These have built-in
displays to show each dealer the
origin and destination of any
Dealer Interlink call.
Philips adopts
Siemen’s ISDN
standard
Philips Electronic Components
and Materials Division has
adopted the Siemens-developed
ISDN-orientated Modular
Architecture (IOM) and its
associated interface as the stan-
dard for a new range of ISDN
c-mos integrated circuits. The
modularity of the IOM
architecture is claimed to make
for easy implementation of the
ISDN customer basic access.
This interface is a standard
4-wire, local point-to-poirt du-
plex interface which intercon-
nects ISDN layer 1 and 2 i.cs, or
layer 1 circuits together. By con-
forming to the IOM interface
standard, the new i.cs are suit-
able for use according to the
CCITT I-series recommenda-
tions in ISDN terminals as well
as in network terminations, line
repeaters and line cards.
Besides the 2B + D channels
required for basic subscriber ac-
cess, a 64Kbit/s M-channel and a
48Kbit/s S channel are also avail-
able. They respectively transfer
status information for local
circuit control and ISDN basic
access referred service informa-
tion (such as signals for activa-
tion, de-activation and mainte-
nance purposes).
Booming
datacom test
market
According to a report from inter-
national market research com-
pany, Frost & Sullivan, there will
be major growth in datacom test
and management markets over
the next five years. The report
“Data Communications Test,
Measurement and Network Man-
agement Markets in Western
Europe" (No.E887) projects an
average annual growth of 26.596
from a base of $154 million in
1985 to a forecast $632 million
(constant 1985 dollars) in 1991.
The study notes that the mar-
ket will be driven both by user
intolerance of system down-time
and by the increasing complexity
and diversity of communications
systems. F & S expect the most
explosive growth to be in pro-
grammable multi-function in-
struments, which embrace
analogue, digital and protocol
measuring and analysing func-
tions. Here, from a small Euro-
pean base of $4m in 1985, they
forecast the market to reach
$104m in 1991.
Analogue instruments will be
the least dynamic product class,
increasing more slowly as a
greater number of digital trans-
mission systems are im-
plemented and modems phased
out. The network management
and control segment will,
according to F&S, increase from
$64m to $268million by 1991.
Private network owners such
as banks, insurance companies,
airlines and oil companies will be
the biggest consumers of all the
groups covered in the study, with
the exception of optical time-
domain reflectometers which are
used more by PTTs.
In 1985, the UK accounted for
28% of Western Europe's con-
sumption of data communica-
tions test and measurement
instruments and network man-
agement systems. At that date
West Germany absorbed 1396,
while Italy and France took 1296
each. By 1991, the UK's share is
forecast to drop to 2596 with
Scandinavia and the Benelux
countries claiming 1496 each.
Besides analysing and fore-
casting product and country
markets, the report reviews re-
levant technology and the
country-by-country data com-
munications environment in
Europe. Individual product lines
are compared and major sup-
pliers profiled.
More information on the re-
| port, which is priced at $2,500,
from Frost & Sullivan on 01-730
3438
Cellular by the
day
A deal between Avis car hire and
Cellrent, a new company offering
Vodafone cellular telephones for
short-term hire, enables car ren-
tal clients at London's Heathrow
Airport to have the option to hire
403
а hand-portable Vodafone. Cell-
rent has identified as a prime
target the international business
traveller who wants instant
worldwide communications |
while visiting the UK. Leading
hotel chains and travel groups
will also act as outlets.
Basic rental is £4.95 per day
with billing being based on the
Meterfone facility. This feature,
unique to the Vodafone network,
allows the call charge units to be
read from the handset display. It
automatically adjusts to the
different charge rates.
Virgin hot air
sponsored by
Cellnet
The Virgin Atlantic Balloon
Challenge, the first attempt to
make an Atlantic crossing by hot
air balloon, is being supported by
Cellnet, one of the two cellular
networks. It will be providing a
number of cellphones to the
organizers of the challenge
together with Celldata equip-
ment to enable them to transmit
and receive technical informa-
tion.
The Cellnet International
Servicelink programme will en-
able the Virgin team to use cellu-
lar phones in New York as well,
where there is a different cellular
system. This scheme allows Cell-
net's customers to use cell-
phones whilst in the USA and
Hong Kong more easily and
cheaply than they might other-
wise be able to do.
Muirhead
moves to high
street
Muirhead, the UK’s first manu-
facturer of facsimile machines
and well known for the machines
used to transmit newspaper
photographs, has launched a
new range of Group 3 office
facsimile machines. The three
machines, each with an increas-
ing range of features, all have the
ability to scan A3-wide docu-
ments and have an RS232C in-
terface port for linking to an
encryption device or computer.
With the objective of expand-
ing its customer base, the com-
pany will sell through a dealer
404
Cellfax facsimile system from Muirhead, which transmits an A4
sheet in 11 seconds.
network in addition to its estab-
lished approach of selling direct.
This, in the past, has been aimed
mainly at the Blue-Chip com-
panies, corporations, govern-
ment and other public bodies —
often those needing real systems
experience.
At a time when growth is
runningat 10096 per annum and
the UK population now exceeds
70,000 machines, the market is
getting increasingly com-
| petitive. Muirhead does not in-
tend to just become a "hot-box
merchant" and aims to employ
its technical expertise to solve
| customers' communications
| problems. For example, it is
offering Cellfax, an adaptation of
| a standard machine. This is con-
| nectedto cellphones ма ап inter-
| face unit fitted with a standard
| ВТ plug and socket arrange-
| ment, eliminating the use of
| acoustic couplers which are
! often unsatisfactory. Equally im-
portant, the system provides full
error correction facilities to en-
sure uncorrupted transmission
regardless of line quality.
Telecom Gold
improves telex
facility
Telecom Gold, British Telecom's
electronic mail service, has in-
stalled CASE Beeline equipment
to provide increased capacity for
message delivery to the telex
network. While users of the
enhanced telex service will see
few outward changes, they will
benefit from an increased num-
ber of telex lines and an even
Ded of telex traffic. An addi-
tional feature is the optional
online assistance, available be-
$10 billion (£6.7 billion) in 1985
and also has overseas offices in
Geneva and Hong Kong. As well
as providing telecommunica-
tions services in the north-east
region of the USA, its companies
also: offer international market-
| ing and consulting services;
| fore each prompt, to guide new |
users.
| The Beeline equipment at
Telecom Gold combines CASE's
DCX communications exchange
and a specialized applications
processor intoa single electronic
telex switching system. This is
integrated with TG's operational
network via an X.25 packet
switching gateway. Messages in-
tended to be sent by telex are
enteredat users' terminals, word
processors or personal compu-
ters and are passed through the
network into Beeline's message
store. Here the Beeline system
takes over the message, trans-
ferring it onwards to the telex
network.
Nynex acquires
BIS
Business Intelligence Services
Ltd (BIS Group) has been ac-
quired by Nynex Corporation
(New England Telephone and
New York Telephone) in an ex-
change of shares valued at £75
million.
BIS Group. a major London-
based information technology
and marketing services orga-
‚ nization operating worldwide,
will continue to operate under its
present management. It provides
management of major organisa-
tion with a range of strategic
information and communica-
tions.
Nynex is the third largest tele-
communications company in the
USA in terms of sales which were
market cellular mobile tele-
phone services; and sell informa-
tion systems and products; etc.
Variable block
length protocol
Microcom has enhanced its
error-correcting Microcom Net-
working Protocol (MNP) with
further classes which increase
the effective line throughput
beyond that provided by MNP
Class 3 which has, for example,
been implemented by Dowty in
its Quattro dial-up modem. MNP
conforms to the ISO Open Sys-
tems Interconnection (OSI) net-
work reference model and sup-
ports interactive and file transfer
applications.
The protocol efficiency of the
new MNP Class 4 implementa-
tion is about 120% so that a
device employing it with a
2400bit/s modem will provide a
throughput of approximately
2900 bit/s. It uses an adaptive
packet assembly so that when
line conditions are poor and re-
transmissions are high, packet
size decreases thus minimizing
the amount of data that needs to
be retransmitted. Conversely,
when line conditions are good,
and retransmissions are few,
packet size increases, and so
maximizing data throughput.
Class 5 adds a real-time adaptive
algorithm for data compression
with a resultant protocol effi-
ciency of 200% while Class 6
provides a universal modem sys-
tem which will operate at a full
range of speeds between 300 and
9,600bit/s and dynamically adopt
the highest speed that can be
successfully handled.
Microcom has just received
BABT Approval for its own AX/
2400 and AX/2400c modems
which conform to MNP Class 4
and 5 protocols respectively. It
hopes to obtain approval for its
Class 6 modem by the middle of
the year.
Telecomms Topics was written
by Adrian Morant.
ELECTRONICS & WIRELESS WORLD
EXPANDABLE
CONVEYOR SYSTEM WIDE
NEPTUNE I, II = RANGE GAUGES,
Hydraulic 25Kg at SENSORS ETC FOR
using 1120mm
Е „= ~ ROBOTIC WORK-CELLS — |
IN OUR аа Ч =
stepper drive be t FREE BROCHURE. 420mm %
length 0.5 - 5.0r1
DC servos
ROBOTS
From or
£475!
INDEXING NAIAD
|| TABLE Water hydraulic/
в DC serv
ва pneumatic
WALLI is a powerful high level language (Work-cell >. " s gm
Amaigamated Logical Linguistic Instructions) for at 500mm
controlling up to 4 robots and their peripheral pot
equipment simultaneously from single computer perspex
(BBC, Apple йе or IBM PC). WALLI is supplied FREE cylinders
with any robot. stepper drive
4 steps/degree
UKs WIDEST RANGE of low
cost robotic & FMS equipment.
“5 — < 200mm
¢ 100mm
SERPENT |, Il 2 100mm
2Kgat 400 or 650mm 50093 > Gyberne ic
pplications
DOSAN p reumatik West Portway Ind. Est., Andover, Hants. SP10 3WW
SCARA steppe-/ball screw
drive
ENTER 62 ON REPLY CARD
TM357 £39 + VAT
3.5 digit 0.4" LCD hand-held. 0.5% basic accuracy: 30 ranges
TM358 £65 + VAT
3.5 digit 0.5” LCD hand-held. 0.5% basic accuracy; 31 ranges
Conductance and hpg measurement
TM452 £138.50 + VAT
4.5 digit 0.4" LCD hand-held. 0.05% basic accuracy; 31 ranges
Conductance and frequency measuremert
TM355 £85 + VAT
3.5 digit 0.5" LED bench/portable. 0.25% asic accuracy
29 ranges
TM356 £95 + VAT
3.5 digit 0.5" LCD bench/portable. 0.25% basic accuracy
29 ranges
TM351 £115 + VAT
3.5 digit 0.5" LCD bench/portable. 0.1% basic accuracy
29 ranges
sl
nics Limited
Ý v t Ives, Huntingdon
—— 9 | handar PE17 4HJ. England
Telephone (0480) 64646 Telex 32250 Test
ELECTRONICS LIMITED THE LOGICAL CHOICE
ENTER 10 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD 405
PINEAPPLE SOFTWARE
Programs for the BBC models ‘B’ with disc dri
DIAGRAM
Still the only drawing program available for the BBC micro which gives you the ability to draw really large
diagrams and scroll them smoothly around the screen stopping to edit them at any time if required
Pineapple's unique method of storing the diagram information on disc means that the size of diagrams is
limited only by the free space on disc, and not the amount of computer memory you have available. (A blank
80 track disc will allow up to 39 mode 0 screens of diagram)
The superb print routines supplied with the program enable large areas of the diagram to be printed ina
single print run in а number of different sizes and rotated through 90 deg. if required. Full use can also be
made of printers which have a wider than normal carriage available
The program 15 fully compatible with the Marconi Tracker ball described below.
PLEASE STATE 40 or 80 TRACK DISC & WHETHER STANDARD BBC or MASTER VERSION IS REQUIRED
PRICE £25.00 + VAT
DIAGRAM UTILITIES
A suite of six utility programs which add additional features to the ‘Diagram’ drawing program. The utilities
include the saving and loading of areas of diagram to and from disc. The ability to display the whole of your
large diagram on the screen at one time (in either 4*4 or 8%8 screen format). The addition of borders and
scfeen indents to diagrams, and the ability to shift a whole diagram in any direction
PRICE £10.00 + VAT
MARCONI! TRACKER BALL
This high quality device comes with it's own Icon Artmaster drawing program and utilities to enable it to be
used in place of keyboard keys, joysticks, or with your own programs
PRICE £60.00 + VAT p&p £1.75
PRICE INCLUDING ‘DIAGRAM’ SOFTWARE £79.00 + VAT p&p £1.75
TRACKER BALL for MASTER series
The Pointer ROM is supplied instead of the Icon Artmaster disc and enables the Tracker bal! to work
directly with the MASTER series computers. (e.g. to use with TIMPAINT etc.). Prices are the same as for the
standard tracker ball
POINTER
The Pointer Rom is available separately for people already owning tracker balls, and comes with
instructions for use with the MASTER computer
PRICE £12.50 + VAT
ve with FREE updating service on all software
PCB
This new release from Pineapple is a printed circuit board draughting aid which is aimed at producing
complex double sided PCB's very rapidly using a standard BBC micro and any FX compatible dot-matrix
printer
The program is supplied on EPROM and will run with any 32k BBC micro {including Master series). Also
supplied is a disc containing a sample PCB layout to demonstrate the programs features
By using an EPROM for the program code the maximum amount of RAM is available for storing component
location and ASCII identification files etc. (Up to 500 components and 500 ASCII component descriptions
may be stored for a given layout), These is no limit to the number of tracks for a given PCB, although the
maximum size of board is restricted to 8" * 5.6
Using a mode 1 screen, tracks on the top side of the board are shown in red, while those on the underside
are blue. Each side of the board may be shown individually or superimposed. A component placement screen
allows component outlines to be drawn for silk screen purposes and component numbers entered on this
Screen may be displayed during track routing to ald identification of roundels
The print routines allow separate printouts of each side of the PCB in a very accurate expanded definition
1:1 or 2:1 scale, enabling direct contact printing to be used on resist covered copper clad board
This program has too many superb features to describe adequately here, so please write or phone for more
information and sample prinouts
PRICE £85.00 + VAT
CONVERTER LEADS
Converter leads to enable the Trackerball to run mouse software and the mouse to run trackerball software
(inc. DIAGRAM). Please state which way round when ordering
PRICE £8.00 + VAT
MICROSPICE
A new addition to our range of engineering software. Microspice is a very powerful DC and AC analogue circuit
simulator package for any model BBC computer
As well as all the usual facilities available with this type of program, non-linear effects. small signal, noise
measurements and sweeps may be performed. Component values may be Swept, allowing component tolerances to be
investigated as ме!! as thermal performance etc. Comprehensive transistor modelling is incorporated using a 20
parameter Ebers Moll description. The program is supplied on disc with a very comprehensive 49 page manual
Please write or ‘phone for more information
PRICE £99.00 * VAT P&P FREE
ALL ORDERS SENT BY RETURN OF POST
ро 39 Brownlea Gardens, Seven Kings, Ilford, Essex 1G3 9NL. @ Tel: 01-599 1476 [2%]
ЕМТЕВ 60 ОМ
RAEDEK EL
SERVING THE COMMUNICATIONS AND ELECTRONICS INDUSTRIES
102 PRIORY ROAD, SCRIBERS LANE, HALL
TRANSISTORS:
TYPE:
VALVES:
TYPE: TYPE: LIST:
£
137.50
90.00
31.50
52.50
52.50
142.00
130.00
125.00
30.00
30.00
56.00
TYPE
2N3375
2N3553
2N3632
2N3733
2N3866
2N4416
2N4427
2N5090
2N5109
2N5160
2N5589
2N5590
2N5591
2N5641
2N5642
2N5643
2N5913
2N5944
2N5945
2N5946
2N6080
2N6081
2N6082
2N6083
2N6084
2501729
2801945
2SC1946A
25С1947
2561969
2561970
2561971
25С1972
25С1978
2562053
25С2237
25С2287
25С2290
MRF237
MRF238
MRF240
MRF245
MRF247
MRF433
MRF449A
MRF450
MRF450A
MRF454
MRF454A
MRF455
MRF458
MRF475
MRF476
MRF644
MRF646
MRF648
MRF901
SD1013
SD1019-STUD
SD1019-5
SD1127
SD1134-
SD1136
SD1143
SD1219
SD1272
SD1278
INDUCTION AND DIELECTRIC HEATING SPARES
INCL
CERAMIC CAPACITORS
VACUUM CAPACITORS
GRID LAMPS
CARBON FREE HOSE
WATER FLOW SWITCHES
AH211A
AH2511
AH2532
BT5
BT5B
BT17
BT17A
EF94
EF95
EF183
EF184
EK90
EL34
EL36
EL84
EL86
EL519
EL821
EN32
ENS91
EZ80
Е281
Е290
FG17
FG105
GXU1
GXU4
GZ34
KT66
KT77
KT88
ML853
ML874
орфо
SOCON
8
Qavo:
QQvO.
1 QvO3-
oooóoóoóoooóo
-NNN = № — +5 а оАо 2 — о
ом
мюфыоонофьюоло
OA2
SOLID STATE RECTIFIERS
RECTIFIER VALVES
OSCILLATOR VALVES
COOLING FANS/FILTERS
etc. etc
BACKWARD WAVE OSCILL
САТ5
IGNITRONS
ENTER 48 ON R
406
EL803S
NL SERIES
QY3-65
QY3-125
QY4-250
RG1-240A
RG4-3000
XG 1-2500
XG5-500
XR1-3200
ХА! -6400
1000's of VALVES TRANSISTORS IC's IN STOCK. PLEASE ENQUIRE ON TYPES NOT LISTED
REPLY CARD
ECTRONICS
Tel: 021-474 6000
Telex No: 312242
MIDTLX G.
GREEN, BIRMINGHAM B28 OTB. ENGLAND.
TYPE
OA3
OB2
OB3
ОСЗ
2C39A
2C39WA
2021
2E26
2K25
3-400ZEIM
3-500ZEIM
3B28
3C45
3CX100A5
4-65A
4-125A
4-250A
4-400A
4-400B
4-400C
4B32
4C35A
4CX250B
EIM AMP
4CX250B
NAT
4CX350A
4X150A
5AR4
5AS4A
5RAGYA-B
5U4GB
5V4GA
6AH6
6AKSW
6AK6
6ALSW
6AQ5A
6AQ5W
6AS6
6AS7G
TYPE: TYPE:
©
©
6AUSGT
6А78
6BA6
6ВЕб
6BH6
6BJ6
6BK4C
6BN8
6826
6C4
6CB6A
6CJ3
6CW4
6DC6
6Е5
6ЕАЗ
6GK6
6HF5
6HS6
6ЈВбА
6JE6C
6JS6C
EK7
6K11
6KD6
6KD8
6L6GC
6LO6
6011
6SL7GT
6SN7GTB
6U8A
12AT6
12AU6
12AV6
12BA6
12BA7
12BE6
12BY7A
12826
12DW7
813
934
935
2050
2050A
5544
5545
5557
5559
5727
5867А
5879
5965
5991
6130
6146А
61468
6360A
6550A
68838
6973
7027A
7199
7247
7262A
7360
7586
7587
7591A
7815AL-GE
==ANOBONNONW===-N у
SSSRaksssssSssss
6
1
8
2-6
3-10
12
ооуу
=)
6.50
5728 CETRON 55.00
807 2.90
810
812А
WE ALSO SUPPLY
EIMAC TUBES AND
ACCESSORIES
соз оз кә тә бә № = һә Оз то @ ът)
эю ә э э э огоо?
ы > сч 00 ол ощ
Фсбоблобо
AWQüupouo
ТТ ===
PRICES - CORRECT AT TIME
OF GOING TO PRESS
TERMS — PLEASE ADD £1.00
P&P AND VAT (a 15% to orders
KLYSTRONS
MAGNETRONS
RECEIVING TUBES
SOLID STATE REPLACEMENTS
THYRATRONS
TRANSMITTING TUBES
EPLY CARD
ELECTRONICS & WIRELESS WORLD
FREQUENCY MULTIPLIER
| needed a cheap but accurate wav of display-
ing frequencies from 350 to 800112 with а
resolution of better than 0.5Hz. This design
multiplies by 1000 over а 100Hz to IkHz
range and locks onto input changes very
quickly — a standard counter would requirea 82 2 ум
gate time of about 10s to give the same
resolution.
Output of the 4046 phase-locked-loop
v.c.0., which is used to drive the frequency
meter, is 1000 times the input frequency.
This output frequency is divided by three
decade dividers to provide a signal for the
phase-comparator input. Phase of the di
vided v.c.o. output is compared with phase of
the input signal and the difference output
drives the v.c.o.
Changing the number of dividers changes
the multiplication factor, but bear in mind
that the v.c.o. only works up to just over
1MHz. Response time is controlled by the
low-pass filter.
Damon lloggett
Carlisle
Cumbria,
Signal in
D
Low pass filter
Frequency counter
module
Vag +15
Vss
Divide by 1000
CLOCK CIRCUIT FOR ASYNCHRONOUS DATA TRANSFER
Besides being simpler than a p.1.1, this clock
circuit with synchronizing inputs can be
used in systems receiving asynchronous data
from several sources.
Async.
inputs
Clock
output
R
Ал
Е? ж В C
Async.
inputs Clock
output
"R <
*Ri >R | Se
ELECTRONICS & WIRELESS WORLD
Normally a fixed squarewave clock is
produced but if there is a transition on any
input, a short output pulse occurs. If output
level is high a negative pulse is added and
vice versa so positive and negative clock
edges are produced for each input transition.
Operation of the oscillator is similar to
that of the two-inverter type so its clock
period is
sin ZR
k(1—k)
where т is RC, V, is threshold voltage for a
logic-level transition. Vpp is supply voltage
and k is Vin/Vop-
Both a simplified circuit and a c-mos
version for three asynchronous inputs are
shown. With no input. clock frequency is at
its lowest so the design is useful for battery-
powered equipment.
Hernan Tacca
Buenos Aires
Argentina
Further reading
CMOS Linear Applications, С. Taajes.
National Semiconductor application note
88. 1978 (two-inverter oscillator).
Nuevo circuito de reloj para maquinas
secuenciales sincronicas, Н. Tacca, Revista
Telegratica Electronica No 831. July 1982.
Nuevo metodo de proyecto en circuitos
secuenciales, E. Capdevile, A. Barragan, М.
Vergani and В, Ahumda, Revista Telegrafica
Electrónica No 821, July 1981.
407
MULTIPLE-CORE
CABLE TESTER
A string of leds powered from a constant-
current source is used in this simple multi-
way cable tester to check for broken or
shorted conductors and crossed wires.
To test for short circuits, the cable is
plugged into connector A. A short between,
say pins 2 and 5 extinguishes diodes 3, 4 and
5. Open conductors are found by connecting
the cable to both connector A at one end and
connector B at the other. A lit led indicates
that its corresponding line is open.
K. Dvorak
Canadian Standards Association
Rexdale
Ontario
я 58V
DUAL-OUTPUT
REGULATOR
One part of a quad single-supply op-amp
forms a regulator both for its own supply
voltage and other circuits. A secondary lower
voltage output with better regulation is
available for references, etc.
Despite its simplicity, this circuit is
adequate for many applications. Perform-
ance is better than circuits using just a
higher-voltage zener diode and trimming is
possible using the op-amp feedback net-
work. Note that the two voltages very
together when the feedback network is
altered.
Current output is about 500mA using the
2A ZTX650. If more current is needed, it may
be wise to buffer the op-amp with a second
transistor.
Robert Baines
Jesmond
Newcastle-upon-Tyne
408
44
PERE ШШ
Constant current source
AMPLIFYING SMALL VOLTAGES
Common practice when amplifying small
direct voltages is to use a bandpass amplifier
with switches at its inputs and outputs. This
proposal is based upon simulation of a
resistor by a switched capacitor.
The first op-amp functions as an amplifier
and d.c.-to-a.c. converter, so the second
op-amp amplifies an a.c. signal. Attenuation
is provided by the third op-amp, which also
acts as a switch for removing switching
effects.
Two inverting and one non-inverting op-
amps are used. Resistance Req is simulated
by a capacitor C,(107!! to 107 ^F) given by
Reg= 1/C f where f is switching frequency so
Vi 7 У.С,
V.=KV,
and
Vout = x R,C,fV2=KVin
where К is 1+R3/Ro.
Kamil Kraus
Rokycany
Czechoslovakia
Vin Amplifier & | V1 V2 jAttenuator£ Vout
d.c. switch switch Е:
ELECTRONICS & WIRELESS WORLD
Designing a
communications receiver
This new British-made receiver aims to outstrip far-eastern
competition in both price and performance. John Thorpe of
Lowe Electronics outlines his design approach.
ost modern communi-
cations receivers adopt a
dual-conversion super-
heterodyne design (Fig.1.). The
multiple-conversion receiver
provides several advantages:
ФА high first i.f., higher than
the highest frequency receiv-
ed, distances the mixer con-
version image from the re-
quired coverage, and allows
its rejection by a low-pass
filter at the input. Also the
local oscillator tunes through
a sub-octave range.
@ A low-frequency final i.f. can
provide selective filters with
good shape factors, and ampli-
fiers for the bulk of the receiv-
er's gain.
Each i.f. section must have a sufficiently
nárrow bandwidth to remove image respon-
ses from the subsequent section. With the
availability of monolithic crystal filters for
the first i.f., a dual-conversion h.f. receiver
will be able to offer more than 80dB of image
rejection for its second i.f.
The r.f. filters at the receiver input are
usually arranged as a bank of fixed band-pass
filters, an appropriate one being selected to
match the receiver's tuned frequency. In
J.R. THORPE
earlier receivers these filters would have a
bandwidth typically less than 100kHz and
would be mechanically tuned, either by a
ganged tuning device or separately as a pre-
selector. In electronically-tuned receivers
this is uncommon: with a few exceptions,
there is no tracked r.f. tuning and filters are
consequently wider.
If the filter bandwidth is less than one oc-
tave the receiver system will be protected
from strong signals that can produce even
order intermodulation products
within the receiver's tuning range.
A set of suboctave filters is
commonly found for frequencies
above | or 2MHz, but below this
limit fewer and wider filters are used.
А very important function of
the input filters is to attenuate
frequencies close to the first i.f.
of the receiver and in the image
tuning range. А separate 30MHz
low-pass filter is often included
to ensure good attenuation. А
second requirement is low inser-
tion loss, since signal losses here
directly worsen the receiver's
sensitivity.
The need for an r.f. amplifier
stage will depend on the type of
mixer and on the sensitivity re-
quired. With a useful sensitivity, an h.f. re-
ceiver would produce an output signal-to-
noise ratio of 10dB for an input signal of
about 0.2uV (p.d. into 50 ohms) in s.s.b.
mode. This corresponds to an input noise
figure of around 10dB, a noise level which
will be exceeded by antenna noise in most loca-
tions using fixed aerial systems. If the receiv-
er is intended for portable use with a whip
antenna it should be more sensitive, and
noise figures of around 3dB are appropriate.
Fig.l. Dual-conversion superhet for general h.f. coverage. First i.f. is commonly between 40 and 75MHz; second i.f. js often
at455kHz because of the wide range of standard filters available for this frequency.
0 to 30MHz
r.f amplifier
eee
r.f. input bandpass filters
Tuning
ELECTRONICS & WIRELESS WORLD
1st. i.f. amplifier
tst. i.f. filter
15kHz bandwidth
Ө Local -oscillator
f 45 to 75MHz
2nd. Lf. filter
25kHz bAw for ssb.
6kHz b/w for ат.
(~) Conversion osciltator
64-545 MHz
Product detector
ssb. audio
2nd. i.f. amplifier
injection oscillator
455kHz + 1-5 КН2
409
LEVEL
FREQUENCY
Fig.2. Reciprocal mixing may reduce re-
ceiver sensitivity when a strong, unwanted
signal is present Noise at h originating
from the local oscillator b is mixed into the
receiver's i.f. passband a; this noise may
also be modulated by unwanted signal g.
с noise sidebands due to phase noise т
oscillator
d wanted signal (weak)
e unwanted signal (strong)
f wanted signal after mixing, including
local oscillator noise.
ist if. filter 45 MHz i£
Fig.3 (right). First mixer and if. filter. А
balanced output from the SL6440 mixer
helps achieve maximum gain and dynamic
range.
Local oscillator
signal
FIRST MIXER
| Е" А The first mixer and first i.f. filter must
Below: layout of the main p.c.b., showing signal and control paths. Manufacture is greatly withstand the effects of potentially many
simplified by avoiding the need for inter-board wiring, corinectors and screening. strong signals over quite a wide range of
frequencies; the performance of these stages
will directly affect the receiver's ability to
resist overload.
Antenna input Double-balanced mixers are finding
favour with many designers for several
reasons:
: ist ТЕ fliter —a useful 30 to 40dB of attenuation of the
aT. V M PT = r.f. input Е local oscillator signal fed into the i.f. filter.
— | is obtained by using a balanced mixer, with
consequently less noise fed into the i.f.
system.
- good isolation between the local oscillator
port and the mixer input port means less
—— af. pre-| | Receiver signal fed back towards the antenna.
| on ates — sensitivity of the receiver to signals at the
À | intermediate frequency is reduced by 30 to
40dB.
— P
Е |. 4 — even-order intermodulation performance
is usually very good, and consequent sav-
PO. к ings can be made in the r.f. input filters
inserfion osc without sacrificing overall performance.
The first i.f. filter serves two purposes: firstly
to attenuate signals at the image frequency
of the conversion to the second i.f., and
secondly to reduce the number of signals
that can reach, and may overload, the second
mixer. Filter bandwidths are in the range 12
2:33 ae Data from control unit to 18kHz, but this is more chosen by
internal. signals = ne available filter elements than by receiver
—M— (Control information requirements, which would call for a nar-
rower filter.
410 ELECTRONICS & WIRELESS WORLD
Matching the first mixer to the filter is
often a problem. Many mixers require a
constant impedance at their output across a
wide frequency range if they are to give good
intermodulation performance.
SECOND MIXER
The second mixer generally has only to cope
with in-band signals: the majority of out-of-
band signals are removed by the first i.f.
filter. It is often selected as a low-noise
device or is preceded by a low-noise amplifier
stage. But if there is excessive gain before or
in the mixer, the receiver’s third-order inter-
modulation performance usually suffers
badly at signal separations of 10 or 5kHz.
Gain up to the selective filter (following
the second mixer) should be kept as low as
possible whilst preserving adequate receiver
sensitivity,
Amplifier and detector stages following
the selective filter have much more effect on
resolved audio quality than on receiver r.f.
performance. The a.m. envelope detector's
linearity is critical for good quality, especial-
ly since some broadcasters now use modula-
tion levels approaching 10096 with heavily
compressed signals.
The response of the a.g.c. system can have
a marked effect on audio quality. For a.m.
reception the average (i.e. carrier) level of
the signal is best used. and the a.g.c.
response should be slow enough to stop low
frequency modulation causing excessive sig-
nal distortion via the a.g.c. feedback path.
With s.s.b. signals, a.g.c. must be derived
from peak signal levels. The attack (gain
reduction) time needs to be fast enough to
prevent i.f. amplifier clipping, but not so fast
that the receiver is deafened by impulse
noise spikes. Slow release times improve
quality, but can be inconvenient for search
tuning and for monitoring two-way traffic
when the signals are of different strengths.
OSCILLATOR PROBLEMS
The local oscillator can have a considerable
effect on the r.f. performance of a receiver.
Modern designs, with cheaper digital inte-
grated circuits, favour electronically-tuned
oscillators and frequency synthesis systems
based on quartz crystal references. These
can provide excellent frequency stability but
suffer froma number of other problems:
@ receiver tuning is not continuous as with
a mechanically-tuned oscillator, but
occurs in discrete tuning steps. For s.s.b.
reception the steps must be small enough
to resolve signal frequencies correctly; a
step size of 10Hz is considered adequate.
@ the oscillators and digital dividers pro-
duce quite large quantities of signals at a
variety of frequencies. These can affect
receiver operation in two ways: signals
picked up by the sensitive input circuits of
the receiver appear as spurious signals
which can mask stations being received or
produce annoying heterodynes; and sig-
nals may alternatively appear as sidebands
to the local oscillator out put, causing the
receiver to have spurious responses at
frequencies other than its tuned fre-
quency.
ELECTRONICS & WIRELESS WORLD
HF-125 SPECIFICATION
Coverage: 30kHz-30MHz (150kHz-26.1MHz for German market)
‘Modes: a.m., s.s.b. (u.s.b., 1.s.b. and c.w.)
Tuning: by spin-wheel, in 15.6Hz steps (step size increases with faster tuning rate); megahertz
quick selection by up/down push buttons.
Memories: 30, with lithium battery back-up
-Ļf. filter bandwidths: 2.5/4/7/10kHz; 400Hz audio filter for c.w.
Sensitivity (typical values for frequencies above 500КН2): (s.s.b.) 0.3y.V for 1098 s/n
(a.m.): 0.7р\ for 10dB s/n at 70% modulation
К.Е attenuator: user-selectable, 20dB
. Noise blanker: permanent operation, 0.4ms blank piod
Dynamic range: > 90dB at 50kHz from tuned frequency, 80dB at 20kHz (both intermodula-
tion distortion and reciprocal mixing)
Image and spurious responses: ^ 80dB rejection
- Audio output 0.75W into internal loudspeaker 1.25W into external 40 loudspeaker
Connections: antenna, 500 (50-239 socket) or 6000 + earth terminal; jack sockets for
headphones, recorder, external loudspeaker, d.c. input (12V at about 250mA)
Options: f.m. and synchronous a.m. modes; internal NiCd pack, charger and active whip
aerial; keypad frequency controller.
@ Electronically-tuned oscillators used in
frequency synthesis tend to have quite
low-Q tuned systems and as a result
produce an output with significant phase
noise. By a process known as reciprocal
mixing (Fig.2) this phase noise worsens
the selectivity of the receiver. With a
low-noise oscillator and a good quality
s.s.b. filter, selectivities of —105dB at
20kHz, improving to better than —110dB
at 50kHz from the tuned frequency are
obtainable, but more typical values are
85dB and —954В.
THE HF-125
At the design stage, the HF-125 communica-
tions receiver was required to have adequate
performance to operate well on the short-
wave broadcast and communication bands;
but an overriding objective was to produce a
receiver which could sell on the UK market
in the £300 to £400 price bracket. Designing
with a fixed price but a flexible specification
produced the following initial guidelines:
@ Standard parts and components should be
used whenever possible; specialized parts
should be producible with minimal tool-
ing costs. As a direct result of this, the
design does not require large volume
production to maintain a low price.
@ Assembly should be as simple as possible.
Asingle p.c.b. design was desirable, avoid-
ing wiring and connectors. Mechanical
assemblies should be avoided in favour of
an all-electronic design.
@ As much circuit as possible should re-
quire no alignment, and necessary adjust-
ments should be straightforward and in-
dependent. Testing and alignment proce-
dures should be provided in the control
system.
CHOICE OF MIXER
For the first mixer, a double-balanced device
was required to overcome performance de-
ficiencies in the necessarily economical r.f.
filters. A choice of three types was available:
diode ring, active ring (using fets) and
integrated circuit (a transistor tree mixer).
The transistor tree mixer, in the form of a
Plessey SL6440 integrated circuit appeared
to offer significant advantages over the other
types:
© 1: could offer a small amount of gain and
so removed the need for an amplifier stage
in the first i.f.
® No broadband г.Г. transformers were
needed at the input and local oscillator
ports oí the mixer, significantly reducing
costs. Also, the local oscillator power
requirement was small.
@ Mixer performance was relatively un-
affected by the impedance seen at its
output, allowing direct connection to the
following crystal filter.
Operating current of the SL6440 mixer
can be externally controlled, allowing а
balance between power requirement, inter-
modulation performance and mixer noise
figure. In the HF-125, the mixer is operated
with about 10dB of gain; a mixer noise figure
oí 8dB is achieved with an input third-order
intercept point of + 10dBm. This perform-
ance fits the specification very well.
The gain of the mixer is dependent on its
output impedance, and with a gain of 10dB
performance is limited by the output stages.
The 45MHz first i.f. crystal filters are of the
fundamental type, with an input impedance
of about 500 ohms matching the mixer's
output directly. With no i.f. amplifier, a.g.c.
aclion is provided by a p-i-n diode which
reduces the mixer load impedance, decreas-
ing its gain and at the same time raising its
intercept point.
INPUT FILTERS
The input impedance of the first mixer is
around 600 ohms, and since this is a conve-
nient value for a high impedance input to the
receiver, all the input filters were designed
to match it. A50 ohm input, also provided on
the receiver, is transformed up to 600 ohms
by abroad-band transformer.
Five selectable fillers cover frequency
ranges 18 to 30MHz, 10 to [8МНЁ&, 4.2 to
10МН2, 1.6 to 4.2MHz and below 1.6МН2.
Although there are too few filters to provide
sub-octave coverage for much of the h.f.
spectrum, an attempt has been made to
separate broadcast bands containing strong
signals from communications bands. Par-
ticular attention has been paid to removing
medium wave signals (below 1.6MHz) from
the higher frequencies. The appropriate
filter is switched into the input circuit by
p-i-n diodes; the high filter impedance helps
reduce signal currents through these diodes
and so prevents intermodulation.
411
2:5кНг filter
1st if filter
15kHz b/w
Conversion
signal
4kHz filter
agc
am
detector
Product
detector
10kHz filter
age
Fig.4. Second i.f. stage includes a cascaded series of amplifiers and filters. Filters are diode-switched for differenti.f. bandwidths.
The filters consist of five-pole high-pass
and low-pass sections constructed from fixed
value inductors and capacitors. There are no
adjustments; to cope with component toler-
ances the filters are designed to be wider
than their required bandwidth. Even so
there may be a variation of several decibels in
receiver sensitivity at the extreme edges of
the filter bands. The alternative type of filter
using over-coupled tuned circuits was re-
jected because of the difficulty of production
alignment.
SECOND I.F. SYSTEM
The first i.f. filters feed directly into the
input of the second mixer. This is also an
SL6440, although it operates at a much
lower current than the first mixer. Con-
figured to give about 4dB of voltage gain, it
still has quite good intermodulation per-
formance; and this, coupled with low gain in
the first i.f. (about 8dB allowing for filter
losses) ensures that the receiver's overall
dynamic range is maintained above 70dB
almost to the edges of the selective passband.
Because there is little room for worsening
the noise figure from the first mixer, the
noise figure of the second mixer is, of
necessity, very low. The receiver as a whole
achieves a noise figure of about 12dB (0.28
uV sensitivity for 10dB s/n in s.s.b. mode).
which is quite adequate for nearly all ap-
plications except perhaps for optimum 10
metre amateur band listening.
The remainder of the second i.f. stage is
based upon the Plessey SL6700 integrated
circuit, intended for a.m. receivers. It con-
tains two a.g.c.-controlled amplifiers, an
a.m. and a.g.c. detector, and an i.f. conver-
sion mixer which in this receiver is used as a
product detector. Use of this chip means that
there are only three active devices in the
whole of the r.f. and i.f. sections of the
receiver.
Multi-element ceramic filters are used in
the 455kHz i.f. for the receivers main
selectivity. Because the small four and six-
element filters cost little more'than a tuned
i.f. transformer, they were used for all
coupling between amplifiers and detectors.
The result is an i.f. system with good filter
shape factors and excellent stop-band atte-
nuation, that requires no alignment in
production. In addition four different i.f.
bandwidths are available by bypassing
selected filters.
412
The 2.5kHz filter used is an expensive
14-element device; but it gives a 6:60 dB
shape factor of better than 1:2, and is
especially suitable for reception of a.m.
signals in s.s.b. mode where a degree of
carrier attenuation is required. Careful filter
matching to achieve a flat i.f. passband
response, coupled with a linear detector in
the SL6700 produces good audio quality in
a.m. mode. The 10kHz filter immediately
before the detector improves the s/n ratio by
removing broadband noise generated in the
final i.f. amplifier.
P.L.L. SYSTEM AND TUNING
The easiest way to achieve the required
frequency stability is to use a phase-locked
loop synthesizer to produce the receiver's
local oscillator signal. Several l.s.i. devices
programmable dividers and phase detectors
- make the single loop synthesizer a
straightforward and economical circuit. Un-
fortunately it is not generally suitable for
receiver use, because the frequency steps
(i.e. tuning increments) are equal to the
reference frequency; and for the loop to
control a wide-range voltage controlled
oscillator (v.c.o.) adequately the reference
must be greater than the required 10 to
20Hz tuning increment.
Two approaches are commonly used to
overcome this problem:
-a controlled phase slip within the р.1.1.
System, where a higher frequency refer-
ence is used with fractional division im-
plemented by dividing by integers N or
№+1 for varying proportions of time.
Because the v.c.o. is divided by a number
either above or below the required value
(although the average value is correct)
there is a gradual phase change between
the oscillator and the reference, and this
has to be made up by some form of
controlled phase shift.
a multiple loop system, using two, three,
or even four separate р.1.1$ to control the
final output frequency. The loops share a
common reference, but the output fre-
quency of each loop is divided by a fixed
value before being mixed into the next
loop.
The cost advantages of a single loop p.1.1.
were so great that the system was considered
very carefully to see if its problems could be
overcome. In a dual conversion receiver
tuning is affected by both the local oscillator
Table 1: i.f. filter selection (frequencies in kHz).
—
i.f. bandwith
lst filter 2nd filter 3rd filter
25 2.5 4 10
4 7 4 10
7 7 bypassed 10
10 500(l.p.f) bypassed 10
and the conversion oscillator frequencies;
so, provided that the first i.f. is kept within
the bandwidth of its filter, the conversion
frequency can be tuned. This allows the local
oscillator to tune in steps larger than the
required tuning increments, and the conver-
sion frequency to fill in with the fine tuning.
In the HF-125, the conversion frequency
is about 44.5MHz, and a crystal oscillator is
the obvious choice to generate this. This
oscillator can be electronically tuned over a
small frequency range of a few kHz by the
control system, and although the resultant
frequency is not locked toa reference oscilla-
tor, the stability is good. In practice the
tuning range was restricted to 1kHz because
beyond this range the linearity of control
suffered unless thermal stability was sacri-
ficed. The control voltage is derived from a
d-to-a converter to allow digital tuning
control.
By tuning the conversion oscillator the
requirements of the local oscillator are eased
somewhat: it is now required to tune in 1КН2
increments. A synthesizer producing 45 to
75MHz from a 1kHz reference is feasible, but
several problems will arise:
@ the phase detector and loop filter require
very careful design to reduce sidebands on
the output (at 1kHz intervals) to an
acceptable level.
@ tuning response of the Joop will be slow.
© the р.1.1. system will not be able to correct
frequency fluctuations in the oscillator
caused by noise or mechanical vibration
to any great extent.
To offset these points, low cost of the system
and a low component count produces a
compact design; and with a c-mos l.s.i.
divider there is virtually no spurious signal
radiation and no need for screening.
PHASE DETECTOR
An important part of the р.1.1. system is the
phase detector and low pass loop filter. The
output from the phase detector will change
at the same frequency as the reference
signal, in this case at 1kHz. Signal compo-
ELECTRONICS & WIRELESS WORLD
nents at this frequency must be removed by
the loop filter to ensure purity of the local
oscillator signal. Here, a digital phase detec-
tor has the advantage that when the oscilla-
tor and reference signals are in phase there is
virtually no signal output from the detector.
Also, the capture range of the р.141. is not
dependent on the response of the loop filter.
The digital phase detector consists of a series
of edge-triggered latches.
To achieve the necessary reduction of
kHz signal in the v.c.o. control voltage, the
loop filter has a long time constant. As a
consequence the lock time of the loop is
considerable — about 600ms for a large
frequency change. This is not normally a
problem in a manually tuned receiver, but to
alleviate unpleasant noises after, say, keypad
entry of anew frequency, the receiver output
is muted until the system achieves lock.
The р.1.1. is implemented with a single-
chip Motorola device containing a pro-
grammable divider, a reference frequency
divider and a digital phase detector. The
necessary division range is from 45 000 to
75 000, and an additional dual-modulus
prescaler (divide Бу 128 or 129) provides a
17-bit counter.
| — A LOCALOSCILLATOR -
A fundamental 1c oscillator provides the
local oscillator signal over a frequency range
of 45 to 75MHz.
The varicap tuning element provides a
rather lossy capacitance, and to include it as
a major part of the tuning reactance would
result in an oscillator with a poor phase
noise performance. To overcome this prob-
lem receiver designers often use several
separate oscillators to each cover part of the
required frequency range; three-oscillator
systems are common. By this means the
required capacitance change from the vari-
cap element is reduced, and its Q can be
improved hy a small series capacitor com-
hined with a fixed capacitor to provide most
of the тс reactance. In the HF-125 a similar
effect is produced without the expense of
several oscillators: the inductance is switch-
ed to give four frequency ranges: 45 to
51МНЕ, 51 to57MHz, 57 to 66MHz and 66 to
75MHz.
Performance is quite satisfactory for a
low-cost receiver. The 1kHz sidebands оп
the oscillator output are below —454dBc.
below —60dBe at 2kHz, and at or below the
noise floor further from the carrier. Peak
f.m. deviation is about +5Hz at the lower
end of the tuning range, rising to about
+10Hz at the higher end. The latter is
audible when a pure tone is resolved, hut is
not detectable on s.s.b. voice signals. Oscil-
lator phase noise results in a receiver selec-
tivitv of about 85dB at 20kHz, and 95dB at
50kHz, corresponding to oscillator noise
levels of — 120dBc/Hz and — 130dBc/Hz re-
spectively,
CONTROL SYSTEM
The control system provides the interface
between the user and the internal workings
of the receiver. It needs to be designed at two
levels: the electronics required to control
ELECTRONICS & WIRELESS WORLD
H.F. RECEIVER DESIGN
Recent years have seen a trend towards more expensive and more feature-laden short-wave
communications receivers on the domestic market Unfortunately, many new designs have
achieved little or no improvement, or have even worsened, the ability of a receiver — to
receive.
This article looks at the design criteria, and necessary compromises, in producing a
low-cost communications receiver with good performance.
To quantify that performance, we can consider some of its aspects —
Sensitivity:
the input signal level required for the receiver to produce, say, a 10dB
signal-to-noise ratio at the output, under ideal conditions with no other
signals present.
Selectivity:
the ability to extract a wanted signal from a band containing many signals.
Selectivity assessment would include measuring filter shape factors and
their degradation by reciprocal mixing.
Dynamic range:
the level of rejection of effects due to strong unwanted signals, including
blocking, cross-modulation and intermodulation.
Stability:
Signal quality:
the extent of frequency changes with time and temperature.
the quality of resolved signals, distortion, signal-to-noise ratio, frequency
response. Also the characteristic of the a.g.c. system.
Facilities:
for example, reception modes, available filter bandwidths, noise blanker,
notch filter, memory channels, external connections etc.
Ease of use:
methods of tuning, frequency display, selection of modes and filters etc.
A successful design should balance the different performance requirements so that the
receiver is neither lacking in any one respect, nor excessively expensive because of the cost
of making one aspect outstandingly good. Features offered will depend very much on the
intended market area and the projected price.
the parts of the receiver and the user's
operating procedure. The latter forms a very
important part of the receiver's specifica-
tion, and in a domestic market is often
dominant over r.f. performance in estab-
lishing sales potential.
To minimize costs and to keep the front
panel unc!uttered, many receiver functions,
such as a.g.c. time constant and r.f /i.f. бат,
are left to automatic control with no manual
over-ride. This approach helps the less ex-
perienced user to operate the receiver.
For the control system a microprocessor
using prom for program storage was choser
so that mask programming would not he
necessary, and devices could be program-
med as required for production.
Software holds the microprocessor in a
static condition when the receiver's controls
are not operated, and with the exception of
the clock oscillator all signals in the control
system remain at a steady d.c. level. This
eliminates nearly all radiat.on from the
control svstem and allows screening to Бе
eliminated without affecting performance.
The microprocessor clock also serves as the
р.1.1. reference oscillator, reducing the num-
ber of signal sources within the receiver.
The microprocessor is supported hy а
liquid crystal display driver chip and а c-mos
ram chip with lithium battery supply backup
for the receiver's memories. These are inter-
faced through the processors i/o ports
rather than being connected to the c.p.u.
data bus for reasons stated above. The
receiver is controlled via a three-line syn-
chronous serial data bus, which is well
filtered te remove low level signals emanat-
ing from the c.p.u. A serial bus was chosen to
minimize filtering and simplify connections.
ASSEMBLY
All components are mounted on two printed
circuit boards. A small board behind the
front panel contains the microprocessor and
memory circuits, the display and all the
front panel controls. It is connected to the
main board by two right-angled connectors,
a total of 15 connections for power and
cortrol lines. The main board is mounted in
the bottom of the case, and connections on
the rear panel of the receiver mount directly
on to this p.c.b. There is no wiring in the
receiver with the exception of a cable to the
loundspeaker mounted in the top of the case.
The main p.c.b. is double-sided; the com-
ponent side is mostly covered with а ground
plane. This, with a careful component lay-
out, reduces interaction between separate
sections of the receiver; no additional
screening is required.
The local oscillator and р.1.1. system have
a separate ground plane from the rest of the
receiver circuit to eliminate circulating cur-
rents in the ground system and the metal
case. Splitting the ground plane was effec-
tive in reducing local oscillator radiation
from the antenna input. An aluminium case
screens the receiver circuits from external
signals.
John Thorpe read engineering and computer
science at Cambridge University, with spon-
sorship from Lowe Electronics. Since gra-
duating in [983 he has been with Lowe at
Matlock where he is head of development.
One of his spare-time interests is bell-
ringing.
413
Microkit
Dept. W4, 18 Coldermeadow Avenue, Cor
1415 74HC
Series Series
UM
OPD
oooooooooooooo
di» d» d» C CO Со С Мә m paas рый CO CO
Сә "M C) UD Ф Ф ке Со Со со со On CO.
bi әәә
5: 55555888
CRYSTALS
32.768KHz.
1.00MHz
1.8432MHz
2.0MHz...
2.4576MHz
3.0MHz..
Asnsoa: anona:
>> оооороооооо:
oooooo oooooo
©» б» Озь 4» о м Ou cuo
Pa b» oto OD UD
a oDuooouco
3.2768MHz
3.579545МН2
3.6864МН2 ...
4.0MHz.
4.194304MHz
4.4336 1875MHz
Баз
Фол Ф бл блл
Po paat paat et рна ра paat ыш рна (уу СУ et et е Or ке сз Со РО Р ©
PI ESSEN
UNREPEATABLE
BARGAINS
FLOPPY DISC
CONTROLLER
WD2791 ...
WD1797
WDS216
222990000005
DN (о e ры РО DO (шу P9 д ры nn
N Со СО Со == ње C) CO Co со CO.
ONLY HIGH SPEED COMPONENTS
PROCESSORS
2128
LINEAR
40% OFF
0536 741664
9.30-1.30 7 days a week
by, Northants NN18 9AJ
OUR EXTREMELY POPULAR
EX-EQUIPMENT MEMORIES)
Guaranteed UV erased. cleaned
and tested
1000's sold to delighted
customers
4116 16k x 1 DRAM
2716 2k x 8 EPROM
2732 4k x 8 EPROM
2764 8k x 8 EPROM
[№]
жж ж X HIGH-TECH ke Ж жж
МЕС V20 UPD70108
REPLI CES 0008 TO SPEED Uf ІВЫ PC 10-40%
< HIGI SPEED ADORESS CALCULATION
IN HARDWARE
+ PIN COMPATIBLE WITH BOBR
* SUPERSET OF 8088 INSTRUCTION SET
* LOW POWER CMOS
вми Y20 UPD70108-8 10.99
ВМ: Y30 UPO70116-6 12.90
x xx k X SPOTLIBHT & x x ж
8212C
MEMORIES
DRAMS 5v NMOS 150n5
(ы Техаѕ)
164 64k x 1
41265 256k х 1
4416 l6k х 4
41464 64k х 4
SRAM 5v NMOS 15015
2114 LP Ik x 4... £1.20
2128 LP 2k x 8 £2.50
SRAM 5v CMOS 150nS
6116 LP 2k x 8 £1.30
6264 LP 8k x 8... £2.30
62256 LP 32k x 8 ....£25.00
EPROM 5v NMOS 15015
2116 2k x 6
MICROPROCESSORS
Z80A CPU
o9oooooooo-ooooco
eó655259555855525959
ecmonooonouucoco ooo
ON aaa Drm
ULCLOS cwvooo
ecoece oocooo
totom tecto го о
ONL ON ONC
«л ‹л‹л лл © © ос
27256 32k x 8 250nS.....
21512 64k x 8
EPROM 5v CMOS 25015
21C64 8k x8 £3.50
21C256 32k x 8 £6.40
21C512 64k x 8 .£14.80
EEPROM 25015
2816A 2k x 8
2864А 8k x 8
BY ESTABLISHED MANUFACTURERS
ON REPEAT ORDERS
10% DISCOUNT
Orders over £25
Orders under £25
Add £1.00 p&p
Add 15% VAT
Export p&p £3
41256 150ns
£2.49 EACH
.£13.50
.£45.00
ORDER RECEIVED AND DESPATCHED BY 3.30pm SAME DAY
ENTER 17 ON REPLY CARD
zc
CRYSTALS
SAME DAY SERVICE
Any frequency from 2MHz to 55 MHz for just
£9.50 (inc p-F p & VAT). Orders received
before 10 am are completed and posted THE
SAME DAY! Just let us know; frequencies?
holder sizes? circuit conditions? (i.e. series
resonance or load capacitance). Cash with
order or use our new credit-card hotline
0703 848961.
McKnight Crystals
Dept Z
Amateur Radio Division
Hardley Industrial Estate, Hythe. Southampton SO4 6ZY
Tel: 0703 848961 Telex: 47506 Fax: 0703 846532
ENTER 75 ON REPLY CARD
414
Used equipment — with 30 days guarantee. Manuals supplied if possible. This is a very
small sample of stock SAE or telephone for LISTS. Please check availability before
ordering. Carriage all units £16. VAT to be added to total on Goods and Carriage.
Tektron
OMI
ix 2215 Oscilloscope
ONLY £475 each
OSCILLOSCOPES
#2500 COMMUNICATION RECEIVERS
A 121 5X МНЕ with NLY £140
ONLY £110 e.
MH: м
р NLY £5 ea
NOW ONLY £12 (p&p £3
ISOLATING TRANSFORMERS
£15 pap £ l
STEWART OF READING Telephone: 0734 68041
m 110 WYKEHAM ROAD, READING, BERKS RG6 IPL
Callers welcome 9am to 5.30pm. MON-FRI. (UNTIL 8pm. THURS)
ENTER 54 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD
Modulated-pulse amplifiers
revived
Recent m.o.s. transistors remove historical limitations to
pulse-duration modulated amplifiers and bring new power and
performance to industrial applications.
dvances in m.o.s. power transistor
Д" plus fresh circuit think-
ing, have propelled pulse duration
modulation power amplifiers from technolo-
gical backwaters to the forefront of sophisti-
cated power deployment. Modulated-pulse
technology provides a new level of compati-
bility with a surprising range of applications.
Besides competing against s.c.rs at the up-
per levels of ‘smart’ power, and providing an
alternative to linear amplifiers where size,
weight, heat dissipation and efficiency are
issues, p.d.m. devices span an impressive
application range, outlined on page 416.
Pulse-duration modulated power sources
now provide off-the-shelf answers for fast-
response four-quadrant d.c. supply needs,
shrink the size and heat dissipation of
variable-frequency a.c. sources and line con-
ditioners, and contribute high efficiency and
ease of voltage stabilization to u.p.s.s. They
also provide new solutions to magnet coil
energization in nuclear accelerators and
high energy physics research, plus fresh
responsiveness and power ratings for d.c.
motor drives.
Low distortion, excellent linearity, and
bandwidth of 12kHz, plus improvements
that are in the offing, add audio and public
address systems to the expanding roster of
new p.d.m. power amplifier applications.
The technology's inherently high efficiency
— upward of 90% is standard, 98% is not
unknown - maximizes operating life and
minimizes heat generation in mobile equip-
ment for robots, in-plant vehicles and re-
search submarines. Small size and low
weight promote mobility and portability,
and enable electronic control to be packed
into tight spaces without the cost and
complexities of water cooling.
Applications that demand a combination
of power and what might be called electronic
agility are particularly compatible with
p.d.m. High power function generators are
widely used in nuclear research, vibration
testing, sonar excitation, and automatic test
equipment, where subtle computer prog-
ramming must be capable of choreog-
raphing kilowatts, or even hundreds of kilo-
watts, of electrical power, and in many cases
p.d.m. amplifers do a significantly better job
than any other technology.
A linear amplifier is inherently inefficient
because of the balance of power supply
voltage not applied to the load is developed
ELECTRONICS & WIRELESS WORLD
BARRY FRIEDMAN
Vr Ун
Solenoid t
~ - leopensvalve | }
for Va> Vm
Modulation
input 3
Lower Vg; setting
opens valve for -| |e
shorter interv
Fig.1. Simple open-loop system adjusts air flow by controlling the solenoid-powered
valve's on/off duty cycle in accordance with flow rate voltage Vg set by potentiometer. So
long as modulation voltage Ум is less than flow voltage Vg the comparator switches to
+10 volts output, energizing relay and solenoid, hence opening valve for air passage.
When modulation triangular waveform Vy exceeds flow voltage Vg, comparator output
switches to zero, releasing relay and solenoid to halt air flow. Waveforms show how
higher values of flow voltage Ук produce longer valve-open periods.
Highly compact p.d.m. amplifier develops 4,506 watts heat dissipation (98% efficiency)
and is smaller than a telephone directory.
across the output transistors. In essence,
whatever the load does not recieve the
transistors dissipate. Pulse modulation
amplifiers skirt this fundamental difficulty,
rather than confront the heat dissipation
issue head on.
The panel on p.419 shows how the effi-
ciency of the simple circuit rises to a
theoretical 100% when an ideal transistor
handles rectangular wave signals. This is the
principle that p.d.m. amplifiers harness: the
power output stage is arranged to handle
only rectangular waves — hence apply full
power supply voltage to the load — regardless
of the kind of signal that the amplifier
processes. Accordingly, even though the
р.4.т. amplifier might deliver 50kW of
sinusoidal energy to a vibration transducer,
efficiency is not limited to the theoretical
78.5% efficiency ceiling of ordinary linear
amplifiers under the same circumstances.
Instead, by arranging for the power transis-
tors to switch rapidly between fully on and
fully off conditions, the output stage pre-
serves a close approximation to the ideal.
In other words, ideal transistors operating
in this mode would exhibit zero dissipation,
hence provide 100% efficiency, regardless of
the input waveshape. This is the essence of
class D operation. The design task faced by
Circuit engineers is to arrange for the output
power transistors to handle only rectangular
waves at full power supply voltage, while
adjusting their conduction periods to vary in
accordance with input signal amplitude. The
fixed-amplitude, fixed-frequency pulses are
adjusted in duration and polarity so that
with output filtering, the amplifier develops
an accurate amplified replica of the input.
WHAT TOOK SO LONG?
What's new is today’s generation of m.o.s.
power transistors, which remove the histor-
ical limitations imposed by early bipolar
designs. Today's m.o.s. power transistors
provide current and voltage ratings compa-
rable with bipolar types, but the feature that
distiguishes them most for modulated pulse
amplifiers is their speed, leading to wider
bandwidth operation, which puts the tech-
nology into the mainstream of industrial
usage. In addition, with today's switching
frequencies far above the human hearing
range, audible noise at the modulation
frequency has been completely eliminated.
In absence of output filtering, p.d.m.
amplifiers feed the load with fixed-
frequency, variable-width pulses whose am-
plitude is equal to the supply voltage. Natur-
ally, only a limited number of applications
can handle raw output pulses: they need to
be smoothed into a continuous but high
power copy of the input.
Early p.d.m. amplifier designs made out-
put filtering difficult, owing to their low
switching frequency. A typical bipolar ampli-
fier designed a decade ago switched at 500 to
5,000 Hz: consequently, inductors capable
of full-load filtering become enormous. The
inability to build such filters into the ampli-
fier, along with the bandwidth limitation
imposed by low switching frequency, has
confined bipolar amplifiers to servomotor
drive systems, where the motor’s inherent
inductance and mechanical inertia provides
416
10V
Set flow rate
Vr, Vx
РЧ
ғ
oe
For Vg; setting
Pressure tank smooths
pulsed air flow
Flow rate feedback “| Уз
Fig.2. Introduction of feedback reduces air flow’s dependence on linearity and amplitude
stability of modulation voltage. Instead, flow rate depends on gain stability of the
high-gain error amplifier — determined by the three external resistors — and the
calibration accuracy of the flow sensor. Comparator develops positive pulses for driving
the power mosfet into conduction whenever error voltage (which has negative polarity),
is more negative than the negative-going modulation voltage. Pressure tank's ability to
smooth the air flow depends on tank capacity, modulation frequency, and rate at which
Pressure control voltage is varied. Flow control system mimics the electrical p.d.m.
power amplifier, which develops a pulsed output in absence of filtering circuits.
AMPLIFIER COMPARISONS
Traditionally modulated-pulse amplifiers have been confined by bandwidth and output
distortion limitations to a niche market powering servomotors. Availability of recent m.o.s.
power transistors has eliminated historic performance limitations, enablihg p.d.m.
amplifiers to compete with a wide range of linear and thyristor power sources. In addition,
they can function as bipolar four-quadrant programmable supplies, variable frequencies a.c.
sources and line conditioners, as well as high-power function generators.
Comparison between commercial linear amplifiers, p.d.m. amplifiers, and thyristor power sources
——————————————————————
First generation Linear Thyristor Second generation
p.d.m. units Power units systems p.d.m. units
————————————————————
Power ceiling 20kW 100 КУА MW MW
Switching frequency 5kHz - 60 Hz 80 kHz
Bandwidth 500 Hz 50 kHz 5Hz 10 kHz
Linearity, d.c. 5% 0.1% - 0.05 - 0.5%
Distortion 5% 0.5% - 0.1-0.5%
Efficiency 80% 30-60% 90% 90-98%
Watts per pound’ 200-500 5-50 15-50 500 - 1500
Dollars per watt 2.00 3-0.6 1.00— 0.25 0.50— 0.30
Watts per cubic inch 5.00 0.15- 0.5 07-2 15-30
бд
p
anatural filtering effect.
Indeed, because most servomotors de-
mand modest amplifier performance, there's
been little incentive for servo system manu-
facturers to exploit new m.o.s. transistor
technology. As a result, much of the current
ferment in p.d.m. amplifier design comes
from firms outside the servomotor field
where entrepreneurial manufacturers seek
markets far removed from the restricted
niche of motor powering.
Today's m.o.s. power transistors give
* Excludes power supply; varies with cooling method. Thyristor systems don't require separate supply.
creative circuit designers the wherewithal to
extend pulsed amplifer capability to per-
formance levels previously the sole province
of linear amplifiers. The upshot is an
industry-wide upgrading of amplifier speci-
fications, where an order-of-magnitude
higher switching frequency raises noise far
beyond human hearing, achieves 12kHz
bandwidth, and permits a built-in filter to
hold switching frequency ripple below 196 of
the output voltage.
Growing compatibility between
ELECTRONICS & WIRELESS WORLD
modulated-pulse amplifiers and music re-
production will probably lead to distributed
music systems with an amplifier built in to
each loudspeaker. Instead of using a large
centralized power amplifier, low-level music
signals will then be piped, probably in digital
form, to the widely dispersed speakers. By
adding address information to each digital
music word, a jukebox-like music source
will then be able to send individual music
selections to self-amplified speakers in each
separate location.
LOW HEAT GENERATION
Reduced heat dissipation leads to lower
transistor junction temperature hence en-
hanced m.t.b.f. In addition, heat removal is
simplified, room air conditioning require-
ments are eased, and the amplifier’s bulk and
weight are significantly decreased. Water
cooling, necessary with many linear ampli-
fier applications, is also eliminated. In turn,
these attributes lead to notable application
benefits: equipment mobility for instance. or
integrally mounted electronics instead of a
separate equipment rack. Another is drasti-
cally reduced operating cost.
If a linear amplifier delivers 50kW of
sinusoidal power to a vibration transducer
for on-line reliability testing, it is very likely
to convert another 50kW into waste heat,
and total power consumption will be in the
100kW range. Ideally, of course, the linear
amplifier should operate at 78.596 efficiency
when handling sinewave signals (Page 419).
In reality, real rather than ideal transistors,
imperfect load matching and the need to
provide a safety margin of supply voltage
bring the efficiency nearer this 5096 figure
than the theoretical 78.596.
Replacing the 5096 efficient linear ampli-
fier in this application with a 9096 efficient
class D amplifier (whose efficiency is inde-
pendent of signal waveform), reduces total
energy consumption from roughly 100 to
55kW. The benefit: a tenfold reduction in
waste heat; the amplifier can pay for itself in
energy savings alone, without the simplifica-
tion of heat removal, air conditioning, and
other support needs.
PULSE DURATION MODULATION
REFRESHER
A mechanical example of pulse modulation
probably affords a more graphic and intuiti-
tive introduction to p.d.m. principles than a
direct electrical one. Figure 1 simply out-
lines basic principles, rather than extol pulse
duration modulation as a superior method
for air flow control.
Assume for explanation's sake a frequency
of 2Hz for the triangular modulation wave-
form, Ум, so that the solenoid-controlled
valve has an opportunity to open and close
twice per second, with the control circuit
determining the duration of the intervals.
The comparator energizes the relay and
holds the valve open for as long as the
instantaneous value of triangular modula-
tion voltage Vy is less than flow voltage Vg.
Viewed differently, so long as the compara-
tor's inverting input terminal is negative to
the non-inverting input terminal the com-
parator output remains at 10V. When the
ELECTRONICS & WIRELESS WORLD
+\5
S Filter averages pulsed
output to develop
feedback voltage
Remote
toad current
readout
Fig.3. Early p.d.m. power amplifiers were constrained by available bipolar transistor
performance to operate at modulation frequencies in the 500-5000 Hz range, which
meant that filter circuits capable of smoothing significant load currents would be larger
than the amplifier itself. Servomotors, which present highly inductive loads to the
amplifier, provide an inherent filtering etfect, eliminating the need in many instances for
any series inductor-capacitor network. This compatibility between p.d.m. amplifiers and
servomotors has probably led the industrial world to overlook application possibilities in
the mainstream of power usage.
In this simplified p.d.m. amplifier configuration, which only handles positive inputs, a
mosfet develops a positive output across the external load, a fraction of which is tapped
off and filtered to form the error-correcting feedback signal. The output transistor is
driven into conduction by the comparator's negative going output; in turn, the
comparator’s output goes negative whenever the error voltage is more negative than the
triangular modulation voltage.
лг
|
Drive pulses
from
comparators
-y
Fig. 5. Full-bridge output circuit, based on pairs of series connected transistors А + B and
C + D, permits bipolar operation from single-polarity d.c. supply. One constraint lies in
the need for a floating (non-grounded) load, although this drawback disappears when
a.c-only applications permit a transformer to be interposed between amplifier and
grounded load. Modern amplifier designs minimize power transistor switching losses by
sophisticated circuit design that confines pulse modulation to only one transistor in each
active pair. For instance, if a positive input signal activates series transistors А and B, itis
only necessary to apply modulated pulses to transistor А; transistor B in this pair can
remain fully on for the duration of the positive input. Likewise, transistor D can be held
fully conducting for negative inputs, while transistor C provides the pulse modulation.
417
modulation waveform exceeds the flow vol-
tage, the inverting input is positive relative
to the non-inverting terminal, which drops
the comparator's output from 10V to zero
and closes the valve.
Different levels of flow voltage established
by the control potentiometer, produce com-
parator triggering earlier or later in the
modulation cycle. Higher Vg values mean
that the modulation voltage exceeds Vg for
only brief periods at the tip of each modula-
tion cycle.
Comparators may have an open-loop gain
of 100,000:1 upwards. For 10V operation,
this means that а 10V/100,000 = 0.1mV
potential difference between the compara-
tor's input terminals will develop maximum
output. If the comparator is operated from
dual-polarity d.c. supplies, the output can
swing to maximum in either direction,
depending on whether the inverting input
terminal is more positive (negative output),
or more negative (postive output), than the
non-inverting terminal. lt takes a 0.2mV
difference between Vg and Ум to switch
output polarity from — 10 to +10V.
CLOSING THE LOOP
Feedback, Vp, from the flow sensor intro-
duces sensor calibration as the system para-
meter responsible for flow rates commensu-
rate with potentiometer setting, Fig.2. In
the open-loop arrangement, Fig.l, system
accuracy depended on the linearity and
amplitude stability of the triangular mod-
ulating voltage Ум, as well as comparator
d.c. stability, potentiometer supply voltage
stability, and so forth. A whole collection of
error sources get into the act.
Use of feedback eliminates most error
sources dnd ties performance to the flow-
meter reading. Feedback also accelerates the
system's response to a change in flow set-
ting, because increased flow setting im-
mediately produces an exaggerated error
voltage and ап overcompensating initial flow
rate. As the tank pressure builds up and
forces a faster flow through the sensor,
increased feedback reduces the excessive
voltage until equilibrium is attained at the
high flow setting.
The pressure tank smooths out air flow
pulsations, but also prevents the output flow
from responding immediately to new flow
settings. One can visualize computer con-
trolled applications in which a digital-to-
analogue converter replaces the manual
potentiometer for generating flow voltage.
For rapid computer-commanded changes in
flow rate, tank capacity becomes an impor-
tant factor in the system’s responsiveness.
Modulating frequency is another crucial
ingredient in responsiveness.
Since air flow control is analogous to a
p.d.m. amplifier’s power control, these con-
flicts between responsiveness and output
smoothness also arise in amplifier design
and application. Modern p.d.m. amplifiers
minimize the effect of this conflict by using
modulating frequencies in the 100 kHz
region. Doubtless, future mosfet circuits
will push the switching frequency higher
and useful bandwidth with it.
418
Vin DER.
tapok \
I—
Summing amplifier
reverses error-
signals polarity
Transistor A Transistor B
ПОТ
Drive pulses and conduction period
Fig.4. A half-bridge output circuit, using complementary p-channel and n-channel power
transistors, enables the p.d.m. amplifier to handle both positive and negative input
signals, including the sinusoidal waveform shown. The drawback to this simple output
circuit is its requirement for a costly dual-polarity d.c. power supply. The full bridge
output circuit of Fig.5 permits bipolar operation from a single-polarity d.c. source.
Modern amplifiers incorporate internal Converters to provide the various operating
voltages required by the amplifier's signal handling circuitry.
Upper transistor A develops positive output pulses in response to positive input signals
(and negative error voltage), while transistor B develops the negative output pulses in
mirror image fashion. The waveforms show how the amplifier's internal filter smooths the
variable width output pulses to produce a sinusoidal replica of the input. Actual
waveforms shown are representative (for the sake of explanation) of an unfiltered
resistance load. A choke input filter alters the voltage pulses and causes a phase lag in
the sinusoidal output. Modern p.d.m. amplifier designs operate at high modulation
frequencies so that a relatively small filter can reduce the output component at
modulation frequency to acceptable levels.
ELECTRONICS & WIRELESS WORLD
SIMPLESTPDMAMPLIFIER |
The simplest p.d.m. amplifier handles only
positive inputs, and develops a train of
output pulses having the same polarity as
the input — Fig.3. The non-inverting ampli
fier operates much as the feedback
controlled air flow system, Fig.2. but re-
quires an inverting amplifier to develop a
negative-going feedback signal from the
amplifier's positive output. The feedback
voltage then opposes the amplifier's input to
produce error voltage Vg. which adjusts the
duration of output current pulses. The com-
parator develops negative drive signals for
the power transistor whenever error voltage
amplitude exceeds (is more negative than),
the modulation voltage. For ease of intuiti
tive circuit understanding. the sawtooth
modulation waveform is presented in both
Fig.2 and Fig.3 with negative-going polarity:
the idea is to maintain the appearance of
compatibility with the error signal's inverted
polarity. In reality, the sawtooth modulation
voltage would ordinarily vary uniformly ab-
out zero, and the error amplifier would
automatically adjust its output to produce
whatever transistor drive pulses were neces-
sary for the desired on-off duty cycle.
For descriptions sake. this primitive
amplifier incorporates no output filter. In
stead, a small internal RC filter smooths a
fraction of the pulsed output for use as
feedback. Remote current readings are pro-
vided by a low value resistance in series wih
the load: a highly stable d.c. amplifier feeds
current signals to а remote indicator
Fancy footwork is necessary to create a
power amplifier capable of developing + 150
volts output. Fig.4, output p-channel mosfet
A operates during positive amplifier input
signals and develops a positive train of 150V
output pulses in response. Conversely. the
second power transistor B, an n-channel
mosfet. responds to negative amplifier т
puts with —150V output pulses. The filter
smooths the pulsed output to. create an
amplified replica of the original input.
One disadvantage of the half-bridge power
output circuit of Fig.4 is the need for two
power supplies. which adds considerably to
system cost and bulk. Another drawback
occurs when driving highly reactive loads:
reactance can cause a transfer of power
supply to the other, building up excessive
and damaging power supply voltages.
Commercial amplifier designs may use
many output transistors connected in para-
Пе! to achieve desired power levels. A fortun-
ate attribute of m.o.s. power transistors is
their positive temperature coefficient for
on-resistance. This characteristic aids load
sharing between transistors. А negative
coefficient would decrease resistance with
temperature, causing the hottest semicon-
ductor junction to hog most load current
and immediately launch into a self-destruct
spiral of ever-worsening temperature rise
and current imbalance.
Biasing the comparators (one positive,
one negative) and using a modulating vol-
tage with peak-to-peak amplitude slightly
less than the sum of the bias voltages
ensures that each comparator responds only
to its assigned error voltage polarity. (Note
ELECTRONICS & WIRELESS WORLD
EFFICIENCY DEPENDS ON WAVESHAPE
Chart shows how efficiency of an amplifier circuit depends on the waveshape being amplified: a fact of
physical reality that prevails even though ideal transistors are used. А varying fraction of the power supply
voltage is developed across the transistor. leading to transistor energy dissipation in the form of heat, but for a
rectangular wave signal, the entire power supply voltage is developed across the load, permitting a theoretical
100% efficiency.
In normal operation, many factors conspire to reduce linear amplifier's efficiency below the theoretical
| ceiling established by signal waveshape. For instance, less-than-ideal transistors introduce resistance into the
circuit. contributing loss of output voltage and internal heat dissipation. Also. itis necessary to provide a safety
margin between peak output voltage and the power supply voltage; this too violates the conditions for
maximum theoretical efficiency. Operating linear amplifiers at reduced power — equivalent to using a larger
amplifier than the application requires — is another source of efficiency degradation. Driving low resistance
loads is no problem for p.d.m. amplifiers. which can feed short circuits without efficiency degradation or loss
of stability; linear amplifiers suffer extreme efficiency losses when driving low resistance values — most of the
power supply voltage is developed across the output transistors rather than the load.
t= — к= - - —+
ч
eV Instantaneous power dissipation
м Load power, №, = М» х!, = V2/R,
Total power, Wy = Vs xl, = М.М /Вь
Averaged over time, T
т
Load power = 1] VUR, dt
о
T
Total power — y МММ /В, dt
о
д Ty2
= A СКЕ. tie TIN
Amplifier efficiency is ratio of т W dt T [K *
useful power + total power x 100% = -= -
PI AE
ills TIGR
For sinusoidal signals (consider only half
cycle signals because simple amplifier will
not handle complete cycles) maximum effi-
ciency becomes
т
Pul V sin? wt dt
f Ё
100% х
о =?
se. v sin2 wtdt
T
ZR,T
7
= 100% x = 100%х 4
"RT
For sawtooth signals
м. = iv
so maximum efficiency becomes
Batt в 1
bul tvs PNE
re ze T : 17875
EE m = 2
RT | с E
Рог square wave signals the ideal transistor
would dissipate no power because it would
apply the entire power supply voltage to the
load.
Efficiency is therefore 100%.
Input
Wave Ratio Percent
signal shape Wil Wr efficiency
Sine СА ти 785
Sawtooth | AYL 213 667
Square 4 00
419
DC-SERVO АМ!
MQDEL 217
Off-the-shelf p.d.m. modules with 500W
continous rating 1500 peak, provide ele-
gant solution to control c.c.tv. camera's
illumination.
that the error amplifier produces an error
voltage of opposite polarity to the amplifier
input). The waveforms of Fig.4 illustrate the
biased comparator operations, which are
perhaps less readily understood than the
configurations of Fig.2 and Fig.3.
A full-bridge power output circuit reduces
power supply cost by permitting bipolar
operation from single-polarity supply, Fig.5.
Each comparator in this basic configuration
now commands the operation of two series-
connected power transistor pairs А+В and
C+D. In high power amplifiers, of course,
many parallel-connected transistors are rep-
resented by each single transistor.
Today's new levels of p.d.m. amplifier
power and performance expand applications
into the full spectrum of industrial usage,
where they provide compact economical
alternatives to linear amplifiers on the one
hand, and fast-response competition to
thyristor power systems on theother. Figure
6 outlines the basic schematics for coil
drives, function generators, and smart pow-
er sources, in addition to traditional motion
control applications. Once the rebirth of
p.d.m. technology is widely appreciated,
further innovative uses will enlarge the
roster of p.d.m. problem solving.
Barry F. riedman is vice-president of market. -
ing at Copley Controls Corp, 375 Elliot
Street, Pewton, Maryland, USA.
Seven p.d.m. power amplifiers are paralleled to
feed fast-rise computer-contoured 160-amp
current pules into magnetic resonance imaging
system's 500 uH, 50 т!) gradient coils. Data
compiled by magnetic resonance imaging by
equipment manufacturer compares new design
based on p.d.m. technology with earlier system
built around linear amplifiers. Size and weight
reductions permit development of compact,
mobile imaging system. Figures show results for
single-axis gradient coil supply; entire system
uses three identical supplies.
420
+
Г
>
og
сої
REFL a E
us j
COIL DRIVER
+
Speed А
command
Servo/
motor \
Tachometer
G3
"n РА
MOTOR CONTROL
60Hz
Osc
Current
Voltage
Current
i < +
Speed
ub
Computer
om
AC POWER SOURCE
+ o (Floating)
Output
to device
under test
interface
Com
FUNCTION GENERATORS
е " V
* <
Input 65Vrms ©
Output
с 115
V
C
Fig.6. Four basic schematics illustrate use of p.d.m. technology in different application categories:
Coil drive; motion control; power delivery and function
different kinds of amplifier uses and power levels.
3 NMR DRIVE VOLTAGE
160 AMP PULSE
generation. Each category spans many
GRADIENT COIL
SEPARATE AMPLIFIERS
DRIVE ADDITIONAL
GRADIENT COILS
ELECTRONICS & WIRELESS WORLD
Multi to single-element
transform
A suggestion for overcoming the two-source limitationn of the
inverse square law by resolving complex force situations, both
those involving non-point sources and those involving any
he concept of force is by way of being
] the most important concept in phy-
sics, simply because it is the basis of all
natural phenomena. Moreover, it is the one
feature common to the three main types of
phenomena — gravitational, electrical, and
magnetic. It is embodied in the classic force
equations of both Newton and Coulomb,
normally expressed as Fg = GM,M,/d’, and
Ев = Q,Q,/eqd”, respectively.
These equations describe particular situa-
tions involving two sources of force. In more
general situations involving three or more
sources of force, these particular equations
or concepts are not applicable. The difficulty
which this brings about is exemplified by
what are variously described as the many-
body problem, the three-body problem and
the three-charge problem.
Be that as it may, the general problem can
only be overcome by arriving at a high-order
concept of force, which is to say a general
concept as distinct from the particular con-
cepts of the force equations.
The thinking used in scientific research
today has its basis in inductive logic, a
technique notoriously prone to error. Thus,
whereas some progress can be made from
the level of fact to the level of theory — ona
level with a first-order concept — any de-
velopment toward higher-order concepts
becomes well nigh impossible. It is for this
reason that scientific theories in general
tend to be particular concepts describing
particular situations.
The application of recursive logic, by
contrast, enables a researcher to develop
high-order concepts at will, and in consequ-
ence it has been found possible to arrive at a
higher-order, more general concept of
force!.
In what follows, an introduction to this
concept is made by way of a transform, a
device which literally transforms the many-
body situation to its more recognisable
two-body form. In use, the transform is
subject to a certain imposed discipline, one
aspect of which is the recognition of a zeroth
element or body, known as the reference
element. Because of this, the two-body situa-
tion becomes a single-element situation,
involving a reference element and a single
source element.
To illustrate the potential value of the
transform in research, an examination is
ELECTRONICS & WIRELESS WORLD
number of point sources.
BY J.C. BELCHER
made of simple configurations of elements,
chosen for the short computer programs
which describe them. The use of the trans-
form in arriving at the centre of force of a
body is also demonstrated, and the oppor-
tunity is taken to effect a convincing intro-
duction to cataclysmic force!
MULTI-ELEMENT TO SINGLE-
ELEMENT TRANSFORM
The force exerted on a reference element, Ay,
by a number of elements N is defined as
F,-kA ARE? ]
where К is a constant of proportionality, Ay
the magnitude of the reference element,
typically unit mass, unit charge, or unit
pole, Ag the resultant magnitude of the N
sources which equals A,cos0, A»cosü»* ...
-Awcosüy, Re the resultant distance be-
tween Ag and A, in the direction of the
reference vector, which equals R,^*59^« x
К,А2сов0 АЕ ж р, Ахсоз®МАк (A. is the magni-
tude of the xth source, R, the radial distance
of A, from Ау, and Ө, the angle subtended by
R, to the reference vector.
This general equation simplifies to the
more particular equation expressed by the
classical equations when N = 1, which is to
say when it involves two sources A, and Aj,
Ag = A,cos 0
ВЕ = R,^icostA = В,
from which
F, = КАА, cose /Ry?. 2
Two important features of this equation are
- The presence of the direction cosine, cos Ө,
which correctly describes Е; as a vector
quantity, a feature not normally brought
SUMMARY
The multi-element transform effectively ex-
tends the application of the two-source basic
force equations to the solution of more
complex force situations involving any num-
ber of sources.
In practical terms, it also provides a useful
application in the determination of the cen-
tre of force or centre of gravity of a body or
source of force, whether of regular or irregu-
lar profile. In certain source configurations it
also predicts the existence of a new form of
force, potentially thousands of orders of
magnitude greater than the force normally
predicted by the basic force equations.
to light in the customary expression of the
classical force equations (apart from one
notable exception, the definition of
Coulomb's equation in Harnwell's text 2),
— The implication that Е is the force exerted
on A, by the presence of A), and not vice
versa. In more complex applications of
equation 1, in which A, is itself a multi-
element array, there are occasions when
the force exerted on A, by А, is not equal to
the force exerted on Ay by Aj.
In the general analysis of arrays of elements,
the presence of the constant k becomes an
irritating accompaniment. The convention
adopted, therefore, is to make units of such
value that becomes equal to unity and can be
disregarded.
In the general case, therefore, when Ay =
land k- 1, equation 1 simplifies to
Fy = Ак/ Re
ARRAYS OF ELEMENTS -
Any array of point sources, simulating a
massive body or charged body, is conve-
niently represented by an array of elements
of unit magnitude, each occupying unit
volume of space or unit volume of area, as
the case may be. In this manner, each
element is located in two or three dimen-
sions relative to the centre of the array, this
centre being ideally the centre of force of the
array, or more often its geometric centre. A
typical arrangement involving a circular
array is shown in Fig.1.
The analysis of array characteristics 15
essentially an analysis of the array's force
characteristics, followed by its proximity-
profile characteristics*, each set of charac-
teristics being divided into the external
characteristics, common to all arrays, and
the internal characteristcs, often peculiar to
the type of array in question.
In this short article, only the force charac-
teristics of arrays are examined, because a
meaningful study of proximity effect and
* Sources of force in the basic force equations are
essentially point sources, having no linear dimensions,
and taking up no volume in space. When such sources
can no longer be regarded as point sources — when they
are in close proximity — then the basic equations no
longer hold true. What happens is that the force equation
is subject to a qualifying factor, the ‘proximity-profile’
factor, the value of which depends on the proximity to the
seurce, and to any irregularity in its profile.
421
profile effect calls for a detailed analysis of
many types of different arrays of elements
and constitutes an article in its own right.
The force characteristics of a spherical
array of elements — simulating the classical
spherical body — in which distance is mea-
sured in terms of radius, are found to be as
follows.
- Magnitude Ag is essentially equal to the
intrinsic magnitude A, the arithmetic
sum of all the magnitudes of the elements
within the array.
- Distance Ry is essentially equal to the true
distance between the reference element
andthe centre of the array.
- Force Fy is Ag/Rre’.
The internal characteristics of such an array,
although essentially in agreement With clas-
sical theory, nevertheless give a more de-
tailed explanation of the factors involved:
1. Magnitude varies directly with the dis-
tance d from the centre, being maximum at
the surface and zero at the centre, i.e. Ap =
Ad.
2. Distance is unity, i.e. К = 1.0.
3. Force is Fy = Ag/1? = Aid.
The force characteristics are, of course,
modified by proximity effect. This effect is
most noticeable over the range defined by
the two inverse points of the array, d = 2 x
radius and d = 0.5 x radius, and reaches a
maximum value at the surface or perimeter
of the array. Its effect can be determined,
however, at distances as great as 1000 x
radius, and as small as 0.001 x radius.
RING ARRAY OF ELEMENTS
The force characteristics of a ring array of
elements are exceptional in that they de-
monstrate a capacity in natural phenomena
to combine a pleasing simplicity of form
with a mathematical complexity of struc-
ture. More to the point, these characteristics
are entirely open to discovery by even the
most casual researcher.
The analysis is conveniently undertaken
by the use of program 1*, a self-contained
program in BBC Basic which both simulates
the necessary array of elements, and carries
out the required analysis. On running the
program, it calls for an input of the number
of elements, N, and then goes into a repeat
cycle for the input of the distance in terms of
the radius along the x-axis between the
reference element and the centre of the array
itself. Within the repeat cycle two for-next
loops determine the value of АЕ using
PRoccalcl and of Rg using proccalc2, which
two procedures essentially carry out the
required transform.
Because the simulation of a uniform ring
is effected by a series of discrete point
sources, simulation error is likely to be
encountered if the value of N is very small.
By contrast, if the value of N is very large,
then the analysis calls for the calculation of
trigonometrical functions involving very
small angles and computing error becomes
prominent. Thus a value of N — 100 is an
optimum figure to input on running the
program.
* Pressure on space led us to hold back these simulation
programs — they are available from the editorial office in
return for an s.a.e.
422
Distance
Fig. 1. The simulation of any non-point
source of force of uniform material is
conveniently effected by dividing it into
unit or partial areas or volumes with a
point source of unit charge or magnetic
pole at each centre of gravity. Each point
source is identified by its value, Аз for
example, and located relative to the origin
by coordinates, Хз, Үз, and Z3. (Dimensions
are in terms of the effective radius of the
body which is of unit-length.) The analysis
of the array of elements thus simulated is
carried out relative to the reference ele-
ment, Ao, conveniently located on the
x-axis at a distance measured in terms of
the radius. The reference vector is normal-
ly concurrent with the x-axis, although this
can be rotated in steps over a full 360^ to
provide data for a polar diagram of the
force exerted on the reference element.
Relative to the reference element, an ele-
ment is located in terms of the polar
coordinates, Ёз, Өз, where cos Өз is the
direction cosine relative to the reference
vector.
In the print-out, the relationship between
the computed results and the theoretical
results for Ag and Rg are given at the side as
an assessment of the accuracy of the simula-
tion and computation.
At d=10,000, the value of Ак = 100,
showing no sign of proximity error. The
value of В; < 10,000, and this shows the
presence of computing error. At — 100, both
values properly show the presence of prox-
imity error, and computing error is essen-
tially absent. Proximity error is predictably
£reatest at d = 1, and this is seen to be the
case.
At d < 1, the value of Ag varies directly
with half the distance. The value of Rc, on
the other hand, is essentially equal to the
base of natural logarithms, КЕ = e! =
2.7182818. This becomes most obvious at d
— 0.001, whereas at smaller distances, i.e.
0.0001, computing error once again become
prominent.
lt is interesting to compare the following
results internal to the array perimeter, with
statements 1, 2 and 3:
4. Magnitude varies directly with half the
distance from the centre, being maximum at
the perimeter, and zero at the centre, i.e. Ag
and А; 9/2.
5. Distance is equal to the base of natural
logarithms, i.e. Re = e! = 2.71828 etc.
6. Force is Fy=A,d/2e?.
SHELL ARRAY OF ELEMENTS __
The hollow enclosed spherical shell, or
equipotential surface, is an important fea-
ture in contemporary physics. Since, by
assuming the validity of the inverse square
law, an attempt is made to demonstrate that
the force on a reference point source within
such a surface must be zero everywhere.
Conversely, proof that such a force is indeed
zero thence confirms the validity of the
inverse square law.
This reasoning would appear to be based
on a misconception of the three-body prob-
lem and its rigorous solution. Since, it
argues, a source of magnitude 9 units at a
distance of 3 units, exerts the same force as a
source of 4 units at a distance of 2 units. п
isolation, the two sources do indeed exert a
force of 9/32 = 4/2? = | unit. Taken
together, however, this simplicity no longer
applies, and use of the multi-element trans-
form will show that, where the two sources
are opposing, the resultant force is
0.290389882 units in the direction of the
larger source. It is at this point, therefore, at
which the transform comes into dispute
with contemporary theory.
Be that as it may, the success achieved
with the simple ring array of elements led
directly to similar research on the shell
array, where the problem has been one of
array simulation, since poor simulation pro-
duces not only incorrect results, but entirely
misleading results. The simulation of the
shell array itself suggests something on the
lines of locating dimples on golf balls, but
the spherical trigonometry involved does
not make for easy calculation where uniform
distribution of surface area is to be achieved.
The final simulation had its basis in a
regulation pattern, drawn with a felt-tip pen
on a six-inch rubber ball and composed of
eight 90° spherical triangles, each with three
quadrants of radius 45? drawn at each
right-angle together with a smaller spherical
triangle at the centre, making a 36-element
array. Although composed of a small num-
ber of elements, this array is nevertheless
exceptionally accurate in its representation
of a spherical surface.
The simulation and analysis of the shell
array is embodied in program 2, the simula-
tion details being held in the pata state-
ments. Because the number of elements is
fixed at 32. the user need only input the
required distance. In numerical terms, the
intrinsic magnitude of the array is set at А =
1.0, which makes for ease of analysis.
As e"? = 1.648721271, and it appears
fairly obvious that, in the general case within
the surface of the shell, Вк = e'^. Under
similar circumstances, Ag = (24)A,d.
The internal force characteristics of the
shell array of elements, therefore, may be
expressed as
7. Magnitude varies directly with two-thirds
of the distance from the centre, being max-
imum at the surface and zero at the centre,
i.e. Ag=2A,d/3.
8. Distance is the square root of the base of
natural logarithms, i.e. Re = 1.658721271.
9. Force Fy = 2d/3e = 0.245253338 dis-
tance.
CENTRES OF FORCE OF HALF-SHELL
ARRAYS
A useful facility afforded by the use of
Multi-element Transform is the determina-
tion of the centre of gravity, or in more
ELECTRONICS & WIRELESS WORLD
general terms the centre of torce, of any
given body or array of elements. In the case
of symmetrical arrays, of course, such a
centre is at the geometrical centre of the
array itself. A problem arises, however, when
the profile of the body or the array is highly
irregular in outline, since under these cir-
cumstances a formal solution presents diffi-
culties.
This particular use of the transform can be
conveniently demonstrated by calculating
the centre of force of a half-shell array.
The simulation of the shell array is effec-
tively that of two half-shells in close juxtas-
position. If the reference element is at some
distance greater than the radius, then the
half-shell adjacent to it is composed solely of
elements having negative x-ordinates, and
the half-shell remote from it is composed
soley of elements having positive x-
ordinates. The convention adopted here is to
refer to these two half-arrays as the adjacent
array and the remote-array, respectively.
To determine the centre of force of the
adjacent array, run program 2 after having
deleted lines 80 and 100, thereby exculding
the elements having positive x-ordinates.
Enter the program with distances of 4000,
and 1000. The results are
distance Re (distance — Rg)
4000 3999.464226 0.535774231
1000 999.4644563 0.5355436802
Reload the program, this time deleting lines
70 and 90, thereby simulating the remote
array. Thence repeat the above sequence
obtaining the following results
distance Re (Rg - distance)
4000 4000.535907 0.535407
1000 1000.53616 0.53616
The mean value of these four difference
values is 0.5357, and it follows from this that
the centre of force of a half-shell in general
terms is at a point approximately 0.5357
radius from itscentre of curvature.
'CATACLYSMIC' FORCE
A significant development arising from early
studies involving the transform, it is unex-
pected prediction of the existence of a
particular type of force of extreme magni-
tude. Over the years, this force has been
identified with a certain type of force in
Nature which gives rise to events of cataclys-
mic proportions, and has been called а
cataclysmic force. That the predicted force
and the actual force are indeed one and the
same thing, would appear to have become
well established. This is confirmed in par-
ticular by the application of the transform to
the analysis of gravitational tidal forces
obtaining within the Sun's core, in which its
prediction of solar phenomena is in excellent
agreement with recorded observation.
Which is to say 'cataclysmic' force ex-
erted essentially by a configuration of slow-
moving planets over a period of weeks or
months. coincides with the occurrence of
large sun-spots or eruptive prominences.
The same force, on the other hand, exerted
by a configuration of fast-moving planets
over a few days, coincides with the presence
of minor sunsports and minor prominences.
In complete contrast, a notable period of
ELECTRONICS & WIRELESS WORLD
Electron
Fig. 2. The negatively charged electron is
normally bound to the group by virtue of
the electrical attraction of the two positive-
ly charged protons, and by the gravitation-
al attraction of their combined larger
masses, causing the electron to orbit the
pair about their соттой axis іп a state of
equilibrium. In the absence of the electron,
the two protons would normally experi-
ence mutual repulsion and fly apart, but
the 'cataclysmic force' set up by the pre-
sence of the electron in this the three-
charge situation effectively guards against
this.
little of no solar activity, the period of the
controversial Maunder Minimum, is seen to
have taken place during a time when the
application of the transform points to a near
absence of planetary configurations found to
have given rise to cataclysmic tidal force.
An examination of 'cataclysmic' force, on
paper at least, suggests it to be the outcome
of some form of mathematical chicanery.
This is understandable, since it has its basis
in a certain mathematical paradox, the
dominant negative direction cosine. Under
normal circumstances, negative direction
cosines exhibit no abnormal behaviour when
paired ой with their counterparts, the posi-
tive direction cosines, and we have seen
evidence of such normality in the simulation
and analysis of both the ring and shell arrays
of elements. If, however, a hollow array is
opened out at one side to produce an open
hollow array, the balance between positive
and negative direction cosines becomes lost.
In consequence, should the negative direc-
tion cosines predominate, the resultant dis-
tance, exhibits a net negativeindex, so much
so that, in the ultimate, Rg — zero, and by
the same token, Fy = infinity. This, then, is
the essential basis of ‘cataclysmic’ force.
A demonstration of this force, entirely
innocent of any form of chicanery, can
conveniently be arranged by running prog-
ram 2 in an adjacent array mode, inputting
values of distance in incremental steps from
d = 0t00.5837 X radius.
THE THREE CHARGED-
BODY PROBLEM
Careful examination of the multi-element
transform, in its association with 'cataclys-
mic' force, shows the resultant distance
will exhibit a negative index if the magni-
tudes ої the sources or elements themselves
exhibit negative signs. Although not a fea-
ture of gravitational force involving massive
bodies, it is nevertheless perfectly obvicus
that such a condition can obtain when
electrical charges or charged bodies of oppo-
site polarity are involved.
The ultimate example of the three
charged-body problem is perhaps the best
represented by the simulation and analysis
of the forces obtaining within the atomic
nucleus. In this demonstration it will be
assumed that the nucleus consists of two
nucleons, a positively charged proton and a
neutron exhibiting a net charge of zero.
Because a neutron can be likened to a
postively charged proton orbited by a nega-
tively charged electron, this substitution
will be assumed, giving rise to three charged
bodies, two positive and one negative.
It seems likely that the negatively charged
electron will see the two positively charged
protons as being a single composite source,
having twice the mass and twice the positive
charge of a single proton. Under these
circumstances, the electrons is likely to
orbit the two protons in combination, as
shown in Fig.2, from which it is seen that at
any given time the three elements are likely
to form an isosceles triangle in space, with
the electron at the apex of the triangle, and
the protons at its base.
The forces exerted on one or other of the
two protons can be determined by running
program 3 and inputting selected values of
the apex angle in the range, 0 — 180°.
The force exerted by the opposing proton
is shown as F, and is normally repulsive in
nature as indicated by the negative sign. By
contrast, the force exerted by the electron,
F, is attractive in nature as indicated by the
positive sign.
Predictably, when the angle is zero, the
two protons are infinitely close together and
the Coulombian force is a repulsive force of
infinite magnitude. Thus the two protons
suffer mutual repulsion. When the angle is
158° or more, however, the ‘cataclysmic’
force experienced between each proton and
the solitary electron is one of mutual attrac-
tion of infinite magnitude. Hence, the two
extremes of force. That the forces on the
protons are zero when the angle is 180°, is
not a serious restriction, because the orbital
motion of the electron will immediately
restore the status quo.
The cataclysmic energy involved in the
atomic nucleus is, of course, well recognised
as nuclear energy. A potentially less hazar-
dous form of cataclysmic energy. however,
would appear to be a feature of the cataclys-
mic array, and, editor willing, this will form
the subject of a further article.
References
1. Belcher, J.C. Unit radius and the resolution of
inverse square law forces. International Journal of
Theoretical Physics, vol. 15, no. 10 1976, pp755-
731.
2. Harnwell, G.P., Principles of Electricity and
Electromagnetism. McGraw-Hill, New York,
1949, 2nd Edition, p11.
John Charles Belcher, MIERE, retired from
British Telecom in 1984, but since 1967 a
major concern has been research into re-
search techniques, particularly successful,
he says in the case of the powerful thinking
technique, recursive logic, which led to an
“extensive and detailed understanding of
natural phenomena in general, described by
some 300 original equations.”
423
£2.5 million for
advanced vision
system
A major research project to
produce a prototype Advanced
Vision System is to involve four
UK organizations:
Thorn-EMI Central Research
Laboratories;
Laser-Scan Laboratories
(Cambridge);
Royal Signals and Radar
Establishment (Malvern);
and
University College London
The project cost is £2.5M to be
spread over three years. The
Alvey Directorate is providing
£1.6M, the remainder being met
by the non-university collabor-
ators.
The vision system's principal
function is to process stereo im-
ages of a scene to produce an
array of depth values, which are
the distances from the viewpoint
to surfaces of objects. Like the
human visual system, the
machine will utilize stereo paral-
lax to calculate depth, having
determined the correspondence
between points in the different
images. The depth arrays consti-
tute 2.5D representations of
scenes providing important, but
not full, information on the 3-D
shape of objects present. The
machine will employ photo-
grammetric techniques, includ-
ing the recognition of control
features, so that absolute
measurements can be obtained.
There are numerous applica-
tions for such a system. One
example is industrial inspection,
where images are produced by
two or more television cameras,
and the 2.5-D representation
forms the basis for automatically
measuring shape variations.
Another example occurs in the
preparation of maps and terrain
data bases, where images are
obtained from spaceborne or air-
borne sensors in two or more
viewing positions. Here the 2.5-
D information can form the basis
for a relief map. Both these ap-
plications are to be used in the
research programme, the data
coming from an industrial in-
spection cell for the first exam-
ple, and from the French SPOT
satellite for the second.
The market potential for a
2.5-D vision system is considered
424
to be substantial — provided that
it is accurate and fast. To achieve
the necessary accuracy, further
development of existing stereo
matching techniques is re-
quired, and is included in the
research programme. To achieve
the necessary speed, the system
is not being implemented on a
. conventional single-processor
computer but on a network of |
Processors running in parallel.
In this way, the intensive com-
putation required can be speeded
up by a factor approaching the
number of processors in the net-
work. The processors in the net-
work will be transputers, manu-
factured by Inmos. The complete
2.5-D vision system, running in
‚ real time, is to be operational by
the end of the three-year project.
Een
Star wars laser?
| Formerly classified details have _
recently emerged of a develop-
ment in free electron lasers that
could become a front runner in
the race for a directed-energy |
beam weapon. Ап ll-member
group from the Lawrence
Berkeley and Livermore Labor-
atories has demonstrated a
mirror-less laser amplifier that
uses an electron beam from an
accelerator to boost the energy
from a 50kW magnetron to near-
ly 1.9GW. The 4kA electron beam
is pulsed once per second and
comes from an experimental test
accelerator (ETA).
Energy transfer from the elec-
tron beam to the microwave
beam takes place in an ‘undula-
tor’ (also called a ‘wiggler’). The
name derives from the interac-
| tion which takes place along an
oscillating path. The undulator
consists of a linear array of
pulsed, air-cored electromagnets
generating alternating dipole
fields. If the dipole field, the
electron energy and the input
microwave radiation are in step,
then lasing action occurs. For
‚ maximum energy transfer (up to
4096), the laser output
wavelength is related to the un-
dulator period divided by the
square of the electron beam
energy. 2
Extending the laser
wavelength from microwaves to
the more militarily useful near-
infra-red therefore demands a
considerable increase in beam
energy. Increasing the overall
power demands also an increase
in the electron beam pulse re-
petition rate, something which
various US teams are working
on.
The Los Alamos National
Laboratory are, for example,
developing a radio-frequency
electron injector with a signifi-
cantly increased ‘brightness’.
This is important because the
laser output can be no greater
| than the power of the beam that
pumps it.
. To produce an effective SDI-
type infra-red beam weapon
demands not only that these
problems be solved: there are
other fundamental physical
constraints. Microwaves of the
frequency used (around 35GHz) -
can be kept parallel by means of
waveguides using well known о
technology. Shorter wavelength
infra-red radiation will depend
for its guidance on focussing
effects which, as yet, are still at
the theoretical stage.
SDI, it seems, still has some
way to go.
Biocomputers
Japanese style
Japan's Ministry of International
Trade and Industry's Agency of
Industrial Science and Technol-
ogy (MITI/AIST) is planning to
launch a biochip research pro-
ject that will cost an estimated
110M yen for the first two years
alone. It's an attempt to circum-
vent what the Japanese see as the
inherent limitations of silicon
technology itself and of von
Neumann architecture. The aim
ofthe MITI project is to design an
artificial intelligence capability
basedon the information proces-
sing principles employed in the
nervous systems of relatively
simple animals. As yet, MITI are
saying little about which organ-
isms they have in mind or indeed
what biomolecules or modelling
techniques they'll be employing.
To begin with, scientists will
develop non-invasive means of
analysing the workings of animal
nervous systems to try and dis-
cover how memory and learning
are accomplished. The resulting
data will then be used to design
models that mimic these proces-
ses. Later in the project they'll be
looking at how living molecules
and cells organize themselves to
. carry out highly complex func-
tions.
Ultimately the intention is to
develop chips based on biological
principles that can circumvent
the limitations of today's sys-
‚ tems. MITI gives no indications
| of what architecture might be
employed — or even what fabrica-
tion technology. But, however
futuristic this approach might
seem, the prospect of ultimately
developing a highly intelligent,
low-consumption computer,
based on relatively slow active
devices, isn't as far-fetched at it
might seem. Each of us already
has one sitting inside our skulls!
. Biocomputers
Russian style
According to G. lvanitskiy,
Director of the Institute of
Biophysics of the USSR Academy
of Sciences, microtechnology
based on organic substances will
become a major force in compu-
ter research and development in
the next 10 to 15 years. Ivanitskiy
Starts from. the basic premise
that living systems employ
highly efficient energy conver-
sion processes that operate at
room temperature. Soviet efforts
are therefore being directed to-
wards a biocomputer based on
energy-efficient ‘organically
grown’ sensors and switching
devices.
Many such devices, says Ivan-
itskiy, already exist in primitive
form. Molecular biology has
made it possible to design trans-
‚ ducers with high sensitivity and
selectivity. At the Institute of
Biophysics, protein-based de-
vices have already been de-
veloped to measure tiny changes
in chemical reactions. Optical
transducers based on biolum-
inescence are also the subject of
research that could extend to the
development of new non-volatile
biological memories. For exam-
ple, the bacterium Halobacter-
ium halobium uses a pigment
called bacteriorhodopsin to con-
vert light into electrochemical
energy. It'sa process very similar
to that which takes place in the
retina of the human eye.
According to lvanitskiy, bac-
teriorhodopsin could be used not
just as a transducer but as the
basis of a memory device. Scien-
tists at the Institute of Bio-
physics have discovered that de-
hydrated bacteriorhodopsin can
be stopped at one stage of the
ELECTRONICS & WIRELESS WORLD
|
transduction process without —
losing the image printed on it. |
Films based оп bacteriorhodop-
sin could thus, in principle, be -
acted on by lasers to record, read
and erase data. The Russians
believe that the contents of a.
large library could be stored on
one 30cm 'biochrome' disc.
As for processing data, Ivanits-
kiy predicts that systems based
on discrete bits will give way to
biological films in which data is
processed through waves of
chemical reaction. He speculates
that protein crystals could act as
media through which moving
plane waves could perform the
equivalent of 10!? operation/s in |
the space of lcm? |
dOXGIa eT a ats
Compute-a-
drug |
Dr Lindsay Sawyer is one of a |
team from the Department of |
Biochemistry at Edinburgh
University who is using 3-р :
computer graphics to perform
what amount to conjuring tricks —
with complex protein molecules.
Anyone who has seen even sim- |
ple biochemical molecules mod-
elled with coloured sticks and
balls will know immediately how
complex these structures are.
When it comes to larger mole-
cules of the sort that abound in
our bodies this 'meccano'
approach is hopelessly in-
adequate.
Dr Sawyer has been attemp-
ting to study the reactions of a
milk protein, beta lactoglobulin
(BLG), using an Evans and
Sutherland PS300 vector display
device in conjunction with a host
computer and a Leeds l.c.d.
stereopsis viewer. The viewer
consists of a pair of spectacles
with l.c.d. shutters in place of the
usual lenses. This enables alter-
nate frames (which correspond
to each half of the stereo image)
to be presented sequentially to
the right and left eyes.
Using a molecular graphics
package called FRODO,
developed by Alwyn Jones of the
University of Uppsala, it is possi-
ble, using any input device such
as a keyboard or a mouse, to
manipulate the images in real
time. It's possible, for example,
to turn a ‘molecule’ around and |
see how it best fits with another
molecule. Using this approach,
Dr. Sawyer has been able to.
Stereo pair of molecular graphic. To see in 3-D these pictures should ideally be cut out and placed in a
binocular viewer. Alternatively the illusion may work if the pictures are separated by a sheet of thin
card, normal to the paper.
provide an ‘intelligent guess’ as
to the structure of the chemical
complex that forms when BLG
binds to certain other molecules
such as vitamin A. This is valu-
able because such complexes are
. not always easily amenable to
X-ray crystallographic analysis.
The images, if viewed in 3-D,
display all the atoms in their
different colours.
The value of this research isn’t
just in its ability to speculate on
complex molecular processes.
Given the structure of one pro-
tein, it should be possible in
theory to design another mole-
cule that would fit onto or into it
to modify the protein’s prop-
erties in predictable way. That in
turn is a possible route to new
drugs. There remains of course
the job of actually creating the
new molecule using some sort of
genetic engineering. And when
you have created it, it may turn
out to be toxic when tested on
animals. Ah well, back to the
(3-D) computerized drawing
board!
Magnetic fields
—the health
risks
An international meeting held
last summer at the A.N. Marzeev
Research Institute of General
and Communal Hygiene in Kiev
examined the biological effects of
exposure to static and time-
ELECTRONICS & WIRELESS WORLD
varying magnetic fields at ex-
tremely low frequencies of up to
300Hz. The job of this task group
was to produce a final agreed
version of a document initiated
by the International Radiation
Protection Association (ІКРА)
and commissioned by the World
Health Organization (WHO).
The document, which is
summarized in a paper published
_ by the National Radiological Pro-
tection Board (Bulletin No 78),
| provides an extremely clear and
concise overview of what 15 pre-
sently known of the dangers of
magnetic fields.
Of static fields, the group con-
sidered that there is no evidence
of any adverse effects on human
health due to short-term expo-
sure to static fields of up to 2
` Tesla(T) or to chronic exposure
to fields of less than 100mT. |
However, it is felt that there is
insufficient knowledge of possi- |
ble effects in certain key areas:
@ long-term exposure to the
nervous system and the car-
diovascular system:
@ certain metabolic reactions
that involve radical pairs; and
@ the use of magnetic reso-
nance systems for medical diag-
nosis involving fields over 2T.
. More studies, says the group,
| should be carried out into the
cellular tissue and whole body
responses to such static fields.
Turning to alternating fields,
the task group was particularly
concerned about reports of an
increased incidence of cancer in
Such fields are commonly no
greater than 0.1-1.0uT. The
group concludes that studies so
far have been inconsistent and
raise more questions than they
answer. Further well-designed
epidemiological studies are
deemed necessary.
Laboratory studies, however,
show no adverse clinical or phy-
siological changes in subjects
exposed to 50Hz fields of up to
5mT. At greater flux densities,
people sometimes report seeing
flashing lights – magnetophos-
phenes — caused by induced cur-
rents in the retina of the eye. At
extremely high e.l.f. fields of
0.5T or greater, acute health
hazards, such as heart fibrilla-
tion exist. It isn't known, howev
er, whether the hazard is a direct
result of the magnetism or of the
electrical currents which are in-
duced as a consequence.
In respect of alternating fields,
the task group concludes that
comprehensive new studies are
needed to assess the risk, if any,
of cancer; also the risk to
embryos in the case of exposure
during pregnancy and finally the
effects of induced currents on
nerve tissue.
What seems to emerge overall,
however, is the extreme difficul-
| ty of demonstrating any phy-
‚ siological effect at all, let alone а
|
|
hazard, of the sort of magnetic
fields that are likely to be en-
countered in the average labora-
tory or workshop.
Research Notes is written by
| the vicinity of a.c. power lines. john Wilson.
425
01-208 1177 Теснхомлтс Lro 01-208 1177
DISC DRIVES
BBC Computer & Econet Referral Centre
АМВ15 BBC MASTER £385 (a) AMB12 BBC MASTER Econet £315 (a)
AMCO6 Turbo (65C ~ 02) Expansion Module £93 (b)
ADCOB 512Processor £195 (b) ADJ24 Advanced Ref Manual £19.50 (c)
ADF14 Rom Cartridge £13 (b) ADF10 Есопе! Module £41 (c)
ADJ22 Ref Manual Part 1 .£14(c) A0J23 Ref Manual Part II £t4 (с)
BBC Masier Dust Cover £4.75 (d)
BBC MASTER COMPACT
A tree packet of ten 3.5" DS discs wilh each Compact
SYSTEM 1 128K Single 640K Drive and bundied software £385 (a)
SYSTEM 2 System t with a 12° Hi Res RGB Monitor £469 (a)
SYSTEM 3 System 1 with a 147 Med Res RGB Monitor £599 (a)
Second Drive Kit £99 (c) Extension Cable for ext 5.25” drive £12.50 (d)
View 3.0 User Guide £10 (d)
BBC Dust Cover £4.50 (d)
ADFS ROM (for B with 1770 DFS & B Plus) £26 (d)
ACORN 280 2nd Processors £329 (a)
Viewsheet User Guide £10 (d)
1770 DFS Upgrade lor Model B £43.50 (d)
1.2 0S ROM £15 (d)
Universal 2nd Processor £75 (b)
MULTIFORM 280 2nd Processor £289 (b)
TORCH 280 2nd Processor ZEP 100
TZDP 240: ZEP 100 with Technomatic РОВООР dual drive with built-in monitor stand
ACORN IEEE Interface £265 (a)
£229 (a)
£439 (a)
META Version 11 — The only package available in the micro market that will
assemble 27 different processors at the price offered. Supplied on two 16K
roms and two discs and fully compatible with all BBC models. Please phone
for comprehensive leaflet £145 (b).
We stock the full range ol ACORN hardware and firmware and a very wide range of other
peripherals for the BBC. For detailed specifications and pricing please send for our leaflet.
PRINTERS & PLOTTERS
EPSON STAR NL10 (Paralle! Interface) .£??? (a)
EPSONLX-86........ " £199 (a STAR NL10 (Serial Interface)............£279 (a)
Optional Tractor Feed LX80/86 £20 (c STAR Power Type
Sheet Feeder LX80/86....... i c (Daisy Wheel). .£229 (a)
X800 329 (a
БАЕО, £449 (a BROTHER НЯ20 £329 (a)
EXBUD £409 (а) COLOUR PRINTERS
LQ800 (80 col) £439 (a
EC CUM -Eseg la} Inlegtex Jet Printer £525 (a)
Dotprini Plus NLO Rom for
TAXAN Epson versions for FX, RX, MX
КР815 (160 cps) .£269 (a) and GLP £28 (d)
KP915 (180 cps) £369 (a)
PLOTTERS
JUKI Taxan АЗ (6 col. Ва! bed)... £679 d
6100 (Dalsy Wheel) .£259 (a) Hitachi 672 £459 (a
Graphics Workstation
NATIONAL PANASONIC (A3 Plotter) .£599 (a)
KX P1080 (80 col) £159 (a) Plotmate A4SM .£450 (a)
PRINTER ACCESSORIES
We hold a wide range of printer attachments (sheet feeders, tractor feeds etc)
in stock. Serial, parallel, IEEE and other interfaces also available. Ribbons
available for all above plotters. Pens with a variety of tips and colours also
available. Please phone for details and prices.
Plain Fanfold Paper with extra fine perforation (Clean Edge):
2000 sheets 9.5" X 11° £13(b) 2000 sheets 14.5" X 11° £18.50(b)
Labels per 1000s: Single Row 3; X 1 7/16" £5.25(d) Triple Row 2-7/16° X 1 7/16" £5.00(d)
MODEMS
All modems carry a full BT approval
RT256 3 PORT SWITCHOVER
SERIAL INTERFACE
Зпрыу1 output or t input/3 output
manual channel selection. Input
MIRACLE TECHNOLOGY WS Range
output baud rates, independently
5.25" Single Drives 40/50 switchable:
TS400 400K/640K
5.25" Dual Drives 40/80 switchable:
TD800 800K/1280K .
3.5" 80T DS Drives:
TS351 Single 400K/640K
TD352 Dual 800K/1280K.......
PD352 Dual 800K/1280K with integral mains power supply
PD853 Combo Dual 5.25"/3.5" drive with p.s.u
PS400 400K/640K with integra! mains power Supply
PD800 800K/1280K with integral mains power Supply ч
PD800P 800K/1280K with integral mains power supply and monitor stand
PS351 Single 400K/640K with integral mains power supply .
£114 (b
.£129 (b
.£199 (a)
.£229 (a)
£249 (a)
. £75 (b
£119 (b
£135 (6
£187 (b
.£229 (a
3M FLOPPY DISCS
Industry Standard floppy discs with a lifetime guarantee. Discs in packs of 10
5\4” Discs
40TSSDD £10.00 (d 40TDSDD
80T SS DD £14.50 (d 80T DS DD
3%" Discs
80TSSDD £20.00 Я
d
80 TDS DD £25.00
51550}
FLOPPICLENE DRIVEHEAD CLEANING KIT
FLOPPICLENE Disc Head Cleaning Kit with 28 disposable cleaning discs
ensures continued optimum performance of the drives. 5'4" £12.50 (d)
3v2" £14.00 (d)
DRIVE ACCESSORIES
Single Disc Ceble £6 (d)
10 Disc Library Case £1.80 (d)
50 x 5\42” Disc Lockable Box £9.00 (c)
Dual Disc Cable £8.50 (d)
30 x 51⁄2" Disc Storage Box £6 (c)
100 x 5\27 Disc Lockable Box £13 (c)
——————M—————————————————
MONITORS
RGB 14" MONOCHROME
1431 Std Res £179 (a TAXAN 12" HI-RES
1451 MedRes £225 (a KX1201G green screen............. .£85 (a
1441 Hi Res £365 (a KX1203A amber screen..... £95 is
MICROVITEC 14" RGB/PAL/Audio PHILIPS 12" HI-RES
1431AP Std Res £199 | BM7502 green screen £75 (а
1451AP Std Res ._ £259 P BM7522 amber screen .£79 (а
All above monitors available in plastic or 8501 RGB Std Res. £139 (а
metal case.
ACCESSORIES
TAXAN SUPERVISION 620 Microvitec Swivel Base .£20 (c)
12° — Hi Res with amber/green options Taxan Mono Swivel Base with
IBM compatible £279 = clock..... £22 (с)
Taxan Supervision И! £319 (a Philips Swivel Base £14 (c
BBC RGB Cable £5 (d
MITSUBISHI Microvitec. . £3.50 (d)
XC1404 14" Med Res RGB, IBM & BBC Taxan £5 (d)... . Monochrome £3.50 (d
compatible е £219 (а) Touchtec — 501 £239 (6
UVERASERS
UV1T Eraser with built-in timer and mains indicator
Bullt-in safety interlock io avoid accidental exposure
to the harmful UV rays.
Itcanhandle up to 5 eproms ata time with anaverage
erasing time of about 20 mins. £59 + £2 p&p.
UV1 as above but without the timer. £47 + £2 p&p.
For Industrial Users. we oer UV140 & UV141 era-
sers with handling capacity of 14 eproms. UV 141 has
a built in timer. Both offer full built in safety leatures
EXT SERIAL/PARALLEL
CONVERTERS
Mains powered converters
Serial to Parallel £48 (c
Parallel to Serial .£48 (с
Bidirectional Converter .£105 (b
selectable 7 018 bit, oód/ever/none
parity. Hardware or sottware
handshake. 256K butter. mains
à UV140 £69, UV 141 £85, p&p £2.50,
\!$4000 V21/23 (Hayes Compatible,
Intelligent, Auto Dlal/Auto Answer). £149 (b) powered £375 (b) Serial Test Cable Serial Mini Patch Box Serial Mini Test
WS3000 V21/23 Professional As WS4000 PB BUFFER Serial Cable switchable at both ends AllowS an easy method to Monitors RS232C and CCITT
and with BELL standards and battery back up
for memory £295 (b)
allowing pin options to be re-routed ог
linked at either end — making it possible
lo produce almost any cable
V24 Transmissions.
indicating status with dual
colour LEDs on 7 mos!
teconfigure pin functions
without rewiring the cabie
assay. Jumpers can be used
Internal buffer for most Epson
printers, Easy to install. Inst
Supplied,
WS3000 V22 Professional As WS300 V21/23 PB128 128K £99 (c) configuration on site and reused £22(d) | significant lines. Connects in
but with 1200 baud full duplex £495 (a) Available as M/M or M/F £24.75 (d) Line. £22.50 (d)
\!$3000 V22 bis Professlonal As V22 and
2400 baud full duplex. .£650 (a) CONNECTOR SYSTEMS
WS3022 V22 Professional As WS3000 but AMPHENOL RIBBON CABLE
with only 1200/1200 £395 (a) 1.0. CONNECTORS EDGE CONNECTORS SONES
WS3024 V22 Professional As WS3000 but ТҮ ceu cage CONN ECTOR m end смо DC) Ab um ue aoe um
( ) -way à
with only 2400/2400 .. £570 (b) Čo ахла commodore эл “Sip | 36 way зи Convoncs 7 2O-way asp беу 200
x way 15 - (solder) E
WS2000 V21/V23 Manual Modem £95 (b) 2 day (исо - Mop | 24 мау plug IEEE (solaer) 26way 120р беу 20р
А х ма — p г
DATA Cable for WS series/PC or XT £10 (d) A D ios "E Bbcr w-
DATATALK Comms Package 2x 28 way (Specium 200p 220° | 500p (IDC) 500р DiL HEADERS
И purchased with any of the above 2х 35 мау 2509 - PCB Mtg Skt Ang Pin T kd ue
P В x 43-way p 4 700p 36 750 p
modems £70 (c) D CON N ECTORS 25 22-may 190p = 24 way 700p 36 way 750p 16 pin 50p 110р
PACE Nightingale Modem V21/V23 No of Ways ans way M „Б GENDER CHANGERS 18 pin 60p -
Мапиа! £75 (b) 9 15 25 37 0 2 20 pin 75р -
2х50-жау($100сопп, 600p 5 way D type
Ж" MALE: 24 pin 100p 150p
(Oter limited to current stocks) She 180 180 290 952 [EURO CONNECTORS | maie 1o Mate. со юр — Z3
SOFTY II IDC 175 275 325 DIN 41612 Plug Skt EE
This low cost intelligent eprom programmer can program 2716, 2516. FEMALE: 2 х 22 way ^ ОР 2338 21р Female to Female DN
2532. 2732. and with an adaptor. 2564 ang 2764. Displays 512 byte StPin 100 140 210 380 wey agran P p
page оп ТУ has a senal and ры Ang Pins 160 210 275 440 3 x 32 way St Pin 260p 300p RS 232 JUMPERS ATTENTION
allel /O routines, Can be used as an emulator, cassette interface Soider 90 130 195 290 3X32wayAngPin 375p 400p (05 way Di Alt prices in this double page
Sohyll £195.00 (b) ioc 195 325 375 IDC Skt A* E 400p 24" Single end Mals £5.00 | advertisment are subject to
ea fer d StHood 90 95 100 120 IDC Skt A * C 400p 24: Single end Female TE change without notlce.
- " 4 I]
v VEO 190 Ms For 2 X 32 way please specify 24 MateMaie © E ALL PRICES EXCLUDE VAT
SPECIAL OFFER
spacing (А +B, A +С).
"Male Female £9.50
Please add carriage 50p
unless indicated as follows:
2764-25 £2.50 (d);
TEXTOOL ZIF MISC CONNS IL SWITCHES
27128-25 £2.75 (d); SOCKETS 24-pin £7.50 21 pin Scart Connector. 200p m. 90p 6-way 105p (a) £8 (b) poris £1.50 (d)
6264 LP-15 £2.80 (d); 28-pin£9.10 40-pin 12:10 8 pln Video Connector 200р 8-way 120p 10-way 150p £1.
Using ‘Prestel’ type protocols. For information
TECHNOLINE VIEWDATA SYSTEM. TEL: 01-450 9764
and orders — 24 hour service, 7 days a week
426 ELECTRONICS & WIRELESS WORLD
LINEAR ICs? COMPUTER COMPONENTS
74 SERIES 74273 2.00 | 7415273 1.25 Skái 0.65
74276 1.40 | 7415279 0.70 0:25
7400 озо | 74278 170 | 7415280 1.90 0.25 LM710 0.48 | TBA 1% Тм545С0 34.00 EPROMs 75154 — 1.20 NEYBOARD
7401 0.30 | 74279 0.90 | 7415283 0.80 | 74Coo 0.70 0.24 LM711 +оо | TBasoo 9.0 Тм599С1 5.00 75159 2.20 ENCODE As
7402 озо | 74283 1.05 | 7415290 0.80 | 74С04 0.50 0.25 LM723 0.60 | T8A810 9.90 | 1602СЕ 6.50 | Ты999 5.00 | 251645 350 | 33160 500 Í avs2376 11.50
7403 0.30 | 74742 3.20 | 741529214.00 ‹ 74008 0.70 0.60 LM725CN 300 | 18420 0.80 | 26504 10.50 | тмб99м 18.00 | 2516-35 5.50 | 35161 650 `
7404 0.36 | 74290 0.90 | 7415293 0.80 : 74С10 070 0.75 І LM733 0.65 | ТВлвгом 075 | 6502 4.50 | тм5991 14.00 | 2532. 4.50 | 35162 750 | 740922 5.00
7405 0.30 | 74293 0.90 | 7415295 140 | 74С14 0.50 1.20 | AY-3-1350 350 | {M741 0.22 | TBA920 2.00 | 65C02-2MHz 2532-30 5.50 | 75172 400 | 740923 600
7406 0.40 | 74298 1.80 | 741529714.00 | 74С20 0.70 0.35 | AY-3-8910 490 | | м7747 0.70 | TBASSO 2.25 12.00 | 280РЮ 2.50 | 2564 1100 | 75182 0.90 .
7407 0.40 | 74351 2.00 | 74.5298 100 | 74C32 100 0.90 | АҮ-3-8912 500 | (m7as 0.30 | TC9109 5.00 | 65024 ZB0APIO 2.75 75188 060 ВАТ
7408 0.30 | 74365A 080 | 745299 220 | 74C42 150 0.95 | CA3019^ 1.00 | мүр 4. TCA210 3.50 | 65028 280СТС 2.50 | 2708 4.80 | 75189 060 AMENS |
7409 030 | 74366A 0.80 | 7415321 370 | 74C48 150 0.90 | CA3020 3.50 | (moi 1. TCA220 3.50 280АСТС 275 | 2716*5V 3.50 | 33365 үс
740 0.30 | 74367A 0.80 | 7415322А 3.90 | 74С73 100 2.70 | САЗО28А 110 | miso 3. TCA270 3.50 2800АВТ 6.50 | 2716-35 5.50 | 35350 0.80
74! 030 | 74376 1.60 | 7415323 3.00 | 74C74 1.20 0.75 | CA3046 0.70 | Lm1830 2: TCA940 1.75 0 i 2ВОАОАЯТ 7.00 | 2732. 450 | 33451 050
742 озо | 74390 110 | 7415324 320 | 74C76 100 0.99 | CA3059 3.25 | гмив7т 3, TDAI004A 5.00 2732A-2 9.50 | 75452 сө
7413 050 | 74393 1.20 | 7415348 2.00 | 74C83 2.00 0.36 | CA3060 3.50 | (1872 3.00 | TDA1010 2.25 Y 2800МА 7.00 75453 070
7414 — 0.70 | 74490 1.40 | 74.5352 1.20 | 74C85 2.25 0.55 | САЗОВОЕ 0.70 | | муве 6.00 | Т0А1022 4.50 à 280АРМА 7.50 | . 75454 0.70
746 0.36 7415353 1.20 | 74CB6 0.50 0.36 | CA3085 1.50 | \м1а89 450 | TDA1024 110 PIRA O een M cand 1150
7417 0.40 74,8356 210 | 74C90 190 0.95 | CA3086 0.60 | {m2917 3.00 | 1011705 3.00 280450700219 | 2732435 $50 | 72755 oes | AYSIOISP 3.00
7420 030 74.5363 1.80 | 74C93 150 3.60 | CA3089E 2.50 | (3302 0.90 | TDA2002 3.25 | 100 | (270825: 200 ея AY51013P 3.0
7421 оё ШАС 745364 тво | 74695 160 9.90 | CA309040 375 | \м3900 080 | TDA2003 1.90 : гвоврю 500 | 27564-28 6.00 492 085 | сом 300
7422 0.36 745365 0.50 | 74C107 1.00 0.35 | CA3130E 0.90 | (м3909 1.00 | TDA2004240 , ZBOBCIC 5.00 втв 120 | IMé402 4.50
7423 036 | 741500 0.24 | 745366 050 | 74С150 500 1.20 | САЗИЗОТ 1.30 | (39r 180 | TOA2006 3.20 j ZeoBDART 9.00 | 27128-2512.50 | E728 120
7425 0.40 | 744501 0.24 | 7415367 0.52 | 74C15) 2.00 0.55 | CA3140E 0.45 | LM3914 350 | ТОА2020 3.20 i 27256-25 400 | сть 120 МЫ
7426 0.40 | 74.502 0.24 | 7415368 0.50 | 74С157 250 6.55 | CA3I40T 1.00 | \м3915 3.40 | TDA20302.50 | Bocasa 750 BT96 120
7427 0.32 | 74.503 0.24 | 745373070 | 74С160 180 0.55 | САЗ!а6 2.25 | 1 м3916 3.40 | TOA25935.00 | 3086 2200 вт? 120 | 6MHz 375
7428 0.43 | 74.504 0. 7415374 0.70 | 74С161 1.80 1.50 | CASIGOE 150 | (413600 1.50 | ТОА2653 7.00 s 27512 Р.О | атов 120 | 8MHz 450
7430 030 | 741505 0. 7415375 0.75 | 74С162 1.80 340 | CA3!6!E 2.00 | 451513. 2.30 | TDA35607.50 | во; £120 27512251400 | ал595 140 k
7432 0.36 | 741508 0. 74,9377 1.30 | 74С163 „80 110 | САЗ162Е 6.00 | м51516 4.50 | ТОАЗВ10 7.50 | 80878 #160 | 201 4.00 | TMS27165.00 | ве 140 SOUND &
7433 0.30 | 741509 0. 74.5378 0.95 | 74С173 1.00 9.55 | CA3I89E 2.70 | мвз3712 2.00 | ТОА7000 3.50 | 8088 17.50 RT BILS97 1.40 VISION
7437 030 | 741510 0. 74.5379 1.30 | 74C174 1.50 2.20 | САЗ240Е 1.50 | мС1ЗюР 150 | TEA10027.00 | 8741 15.00 | 21078 5.00 CONTROLLER 811598 1.40
7438 0.40 | 74.511 0. 74.5381 4.50 | 74С175 1.50 0.48 | CA3280G 3.00 | 1413 0.75 | TLO6ICP 0.40 748 2111А-35 4.00 8815120 4.50
7439 0.40 | 741513 0. 7415385 3.25 | 74C:93 1.50 0.32 | 07002 6.00 | мС145в 0.45 | 1.062 0.60 2114 1.50 | сятѕ027 18 00 i
7440 0.40 | 741514 0. 7415390 0.60 | 74C194 1.50 0.60 | 0АС1408:8 3.00 | мС1495 300 | Т.0624 0.90 2114 250 | САТ5037 1200 | 9602 3.00 CRYSTALS
7441 — 0.90 | 744515 0. 7415393 1.00 | 74С195 150 115 | ОАС08003.00 | мС1496 070 | TLO7! 9.40 CRT6545 9.00 | 9636A 160
7442А 0.70 | 741520 7415395 100 | 74C221 2.50 0.80 | ОАСО808 3.00 | мсззаор 2,00 | TLO72 0.70 2147 EF9364 8.00 | 9637АР 1.60
7443A 1.00 | 741521 0. 74.5399 1.40 | 74C244 2.00 0.70 | 06308 3.00 | wc340: 0.70 | TLO74 тло EF9365 25.00 я 32 768KHz 1.00
7444 140 | 744522 0. 74.5445 1.80 | 74C245 2.25 0.80 | HA1366 1.90 | C3403 0.65 | 11081 0.35 4116 2.00 | EF9366 25.00 16432MHz 2.25
7445 070 | 741524 0. 74.5465 1.20 | 74C373 2.25 6.65 | 1С17106 6.75 | мезосм 4.10 | 1.082 0.55 4116-20 EF9367 36.00 2 00MHz 2.25
7446A 1.00 | 741526 0. 7405467 1.20 | 74C374 2.25 1.00 | ICL7611 0.95 | мк502409.00 | TLO83 0.75 EF9369 12.00 2 35760MHz(L
7447А 100 | 741527 0. 74.5490 1.50 | 74С902 1.20 0.75 | ICL7650 4.00 | м902 5.00 | Tloas 1.00 41256-15 300 | MC6845 6.50 2.00
7448 1.00 | 74528 0. 745540 1.00 | 74C9! 9.00 0.65 | ICL7660 250 | м922 4.00 | TLO94 2.00 MC6B45SP 6 50 2.45760MH2(S)
7450 0.36 | 741530 0. 7415541 100 | 74С912 4.50 3.80 | 1С18038 4.00 | мм6221А 3.00 1.20 MC 6847 6.50 2.50
7451 0.35 | 741532 0. 7415608 7.00 | 74C922 6.00 2.50 | ICM7555 0.90 | NEs29 2.20 3.20 SFF96364 8.00 2.5MHz 2.50
7453 0.38 | 741532 0. 74.5610 25.00 | 74C923 6.50 0.75 | ICM7556 1.40 | wEs3: 120 1.20 4t64-1T TM59928 10.00 3276MH: 1.50
7454 0.38 | 744533 0. 74.5612 25.00 | 74C925 6.50 0.75 | LC7120 3.00 | мЕ544 1.90 6.00 3 5795MHz 1.00
7460 0.55 | 741537 0. 74.5624 3.50 | 74C926 7.50 0.90 | LC7130 3.00 | мЕ555 0.22 | ULN200!A 075 4.00MHz 1.50
7470 0.50 | 744.538 74.5626 2.25 0.70 | LC713! 3.50 | мЕ556 0.60 | ULN2002A 0.75 4416-15 3.50 4194MHz 200
7472 045 | 74540 0. 74.5628 2.25 1.00 | LC7137 3.50 | мЕ564 4.00 | ULN2003A 0.75 4532-20 2.50 а 49MHz 1.00
7473 0.45 | 74542 0. 7415629 1.25 2.40 | 12347 1.26 | №565 120 | ULN2004A 075 201771 20.00 | 4 9152MHz 250
7474 050 | 741543 1. 7415640 200 При 0.36 | 12351 0.66 | мЕ566 150 | ULN2068 2.90 Д AD7581 15.00 |. 201791 20.00 | 5.00МН: 1.50
7475 0.60 | 74548 0. 7415640-1 3.00 0.50 | 12353 0.90 | wEs67 1.25 | ULN2802 1.90 5101/5501 4.00 | А0С0808 11.90 | 201793 20.00 | 5068MMz 175
7476 0.45 | 74549 1. 74.5641 150 | 7441500 0.45 2.40 | 17355 0.90 | wEs70 4.00 | ULN2803 1.80 5514/5114 4.00 | А0561 20.00 | 201797 22.00 | 600мн: 1.40
7480 0.65 741.551 0. 74.5642 2.50 74ALSO2 0.45 1.40 | LF356N 1.10 NE571 3.00 | ULN2804 1.90 5516 4.00 АМ25510 3.50 WO17D 24.00 | &13aaMHz1.40
7481 — 180 | 74.554 0. 7415642-1 3.00 | удА 504 050 1.40 | LF357 100 | wE592 о9о | UPC575 2.75 5517АР 400 | №25 52521350 | wo169115.00 | 700мых 1.50
7483А -1.06 74.5643 250 | 2440504 050 240 | (2398 4.00 | nessaop 150 | UPC592H 2.00 3 = AM25.S2538350 | wD214312.00 | 716MHz 175
7484A 1.25 7415643-1 300 | 74ALS10 045 1.70 | LMIOCLH 450 | wrss3se 1.60 | UPCIS6H 3.00 6116Р-3 3.50 | AM26LS31 120 | wo2793 2700 | воомнг 1.50
7485 — 130 | 74LS74A 0.35 | 7415644 3.50 | 744.520 0.45 0.45 | LM301A 0.30 | мєѕѕзар 120 | UPCII8SH 5.00 6116L2-3 AM26LS32 1.20 | №02797 27.00 | ввєтмнг 175
7486 0.42 | 74LS75 0.45 | 7415645 2.00 | 74A,S32 0.45 0.90 | LM307 0.45 | wEssaaap 1.50 | XR210 400 s AM79100C 25.00 10.00MHz 175
7489 210 | 74LS76A 0.36 | 7415645-1 400 | 7441574070 0.48 | LM308CN 0.75 | Op.o7EP 5.50 | XR2206 4.50 585; : DACBOCBI-V 10 50MMz 2.50
74904 0.55 | 741578 0.42 | 74.5668 0.90 | дс 180 0.60 | LM310 225 | PLLoza 5.00 | ХН2207 3.75 ` 62642.15 3.40 20 10,.70MHz 1.50
7491 0.70 | 74LS83A 0.70 | 74.5669 0.90 | 2д[5139 150 1.50 | LM311 0.60 | nCai36 0.55 | ХА2211 5.75 DMe:3: 6.00 CHARACTER 0048; 200
7492A 0.70 | 74585 0.75 | 74L9670 170 | 71415244 400 750 | LM31B 1.50 | Cats: 2.00 | XR2216 6.75 6514-35 4.00 | OP8304 3.50 MRI ORME 12.00мнг 1.50
7493A 0.55 | 74.586 0.35 | 7415682 250 | 7.415245 475 7.50 | LM319 1.80 | ЯС4195 1.50 | XR2240 1.20 6810 200 | 053691 3.50 14.00мНг 1.75
7494 110 | 74.590 0.48 | 7415683 3.00 | 74415572 260 300 | LM324. 0.45 | 904558 0.55 | ZN404 1.00 745189 1.80 | 058830 1.40 | 993251 790 | уа зімн: 1.60
7495A 0.60 | 74.591 0.90 | 7415684 3.50 | 7:л1с7: 450 2.60 | LM334Z 115 | 550240 9.00 | 23414 9.80 745219 2.25 | 058831 1.50 | #082514 1% | |, 7бмнг 250
7496 0.80 | 741592 0.35 | 7415687 3.50 | 74aLS580 250 4.20 | LM335Z 1.30 | бАА1900 16.00 | 2М419Р 1.75 058832 1.50 15.00мнг 2.00
7497 290 | 74.593 0.54 | 7а 56ва 3.50 4.50 1.60 | 57296364 800 | ZN423E 1.30 9341 6.00 | 058833 2.25 16.00MHz 2.00
74100 1.90 | 7445958 0.75 | 7415783 16.00 6.50 9.40 | 51490 3.00 | ZN424E 1.30 р 058836 1.50 17.734MHz 150
74107 0.50 | 74.596 0.90 4000 SERIES 2.00 0.60 | SN?6013N 3.00 | 24425Е8 3.50 93425 6.00 | 058838 2.25 18.00MHz 1.50
74109 0.75 | 74.5107 0.40 3.50 0.50 | 5м76023м 3.00 | ZN426E8 3.00 07002 8.00 DUM 18.432MHz 1.50
74110 0.75 | 7415109 0.40 4000 0.20 7.00 3.00 | SN76033N 300 | ZN427E88.00 MC1488 0.60 4 19.969MHz 1.50
7411 0.56 | 7415112 0.45 4001 0.24 7.00 SN76115N 215 | ZN428E84.50 MC1489 0.60 | $AA50206.00 | 20.000MMz 1.50
74116 — 170 | 7445113 0.45 745 SERIES TS 0.46 | LM380N 1.59 | Sw764894.00 | ZN429E8 2.25 = MC3446 2.50 | 5АА50307.00 | 24 000MM? 175
74118 — 110 | 7415914 0.45 4006 070 1.20 | LM381AN1.70 | 576495400 | ZN447E 9.00 2822 4-00 | wc3459 450 | Saasoa 16.00 | 48 ооомне 175
74119 170 | 7415122 0.70 | 74500 0.50 | 4007 02 0.36 | LM381N .3.09 | 3476660120 | 2м448 1 750 24810, 2.50 | wcS3470 475 | saAsoso900 | nemir 23
74120 1.00 | 74.5123 0.80 | 74502 050 | 4008 060 0.40 | LM383 3.25 | 52025642700 | ZN449E 3.00 185050 2.00 | MC3480 8.50 PXO1000 12.60
74121 0.55 | 7415125 0.50 | 74504 0.50 | 4009 0.45 1.50 | LM384 2.20 | Spesis 7.50 | ZN4SOE 7.50 18540130 200 | MC3486 225
74122 0.70 | 7415126 0.50 | 74505 050 | 400 0.60 1.25 | LM386N-1 100 | 7A7120 4.29 | 24459СР 3.00 745188 180 | MC3487 2.25
74123 0.80 | 74.5132 0.65 | 74508 0.50 | 4011 0.24 1.30 | LM387 270 | TA7130 140 | ZN1034E 2.00 745207 2.25 | мСа024 5.50
74125 0, 7415133 0:55 | 7450 050 | 4012 0.25 2.00 | LM391 1.80 | rA7204 1.50 | 24А10406.60 | iossaC-5 320 | 745248 180 | MC4044 5.50 Please note
74126 — 0. 74.5136 0.45 | 7451 0.75 | 4013 036 1.20 | LM392N 110 | ТА7205 0.90 | 744134Н. 23.00 | 8256 1800 All prices are subject to
74128 0: 74.5138 0.55 | 74520 0.50 | 4014 ово 1.50 | LM393 085 | 1747222 150 | ZNA234E9.50 | ус. 5400 MC14411 7.50 change without notice
74132 0. 74.5139 74522 0.50 | 405 070 0.48 | LM394CM 400 | тузлу 1.50 i MC 1.4412 7.50 ge win
74136 р 745145 0. 74530 0.50 4016 0.36 0.55 | LM709 0.35 8259C-5 4.00 75107 0.90 Only current prime grade
74141 0. 7405147 1. 74532 0.60 | 407 055 3.20 | 75108 0.90 components stocked
74142 2. 745148 1, 74537 0.60 | 4018 060 0.80 8275 29.00 75109 120
74143 74.5151 0.65 | 74538 0.60 | 409 0.60 2.25 VOLTAGE REGULATORS 8279C-S 4.80 75110 0.90 We also Stock a wide
74145 745152 2.00 | 74540 05 | 4020 080 а 225 8282 400 75112 160 range of: Transistors,
74145 f 74.5153 0. 74551 0.60 | 4021 0.60 | 4014 -80 7 75113 1.20 iod i lasti
nS : TUS 24964 pas | 4021 050 | 4063 100 1A FIXED VOLTAGE PLASTIC TO220 ава аво | 2816301500 | 25112 140 D oes Ke pasi с.
74148 7415155 0. 74974 0.70 | 4023 озо | 40173 120 TWE МЕ 8287 во | 2+8 30.00 | 75115 1.40 Беа
74150 1: 745156 0. 74585 558 | 4024 oas | 40174 100 5V 7805 0.45 7905 0.50 8287 280 | 930625655 | 75121 140 Thyristors and Zenors
74151A 0. 7415157 0. 74586 1.00 | 4025 024 | 40175 1.00 6v 7806 0.50 7906 0.50 8755A 16.00 | 76x 6) 4.50 | 75122 1.40 Please phone for details
74153 0. 74.5158 0. 745112 1.50 | 4026 0.90 PEG a 6V 7808 0.50 7908 0.50 | 75150Р 1.20
74154 1 74151604 0.65 | 745113 120 | 4027 04 . 12V 7812 0.45 7912 0.50 OTHERS
74155 тЫ 74514 120 | 4028 060 | 40194 1.00 15V 7815 0.50 7915 0.15 OPTO-ELECTRONICS
74156 0. 7415162А 0. 745124 3.00 | 4029 075 | 40244 150 18V 7818 0.50 7918 0.50 x BPX25
74157 0. 74\5163А 0: 745132 1.00 | 4030 0.35 | 40245 1.50 24V 7824 0.50 7924 0.50 0.125) BPX34 3.00
74159 2. 74.5164 0. 745133 0.60 | 4031 125 20857 tes ТА FIXED VOLTAGE PLASTIC TOS; RED T/L2090.12 BPw21 :
74160 А 7415165А 1, 745138 1.80 4032 1.00 3 . GAN 14.211 0.16 1222 018
74161 i 7ALS166A 745139 1.80 1035 1.25 | 40374 180 Fu 78.05 ie и EE YEL R212 0.20 | ти22 сахл,
74162 Т. 745168 1. 745140 1.00 | 4034 2.50 | В0С95 0.75 Ву 78108 0.30 15V 79115 0.50 Rect LEDs MAN74/DL704 1.00
74163 t 7415169 1. 745151 1.50 | 4035 0.70 | 80С97 0.75 12V 78.12 0.30 (R/G/Y) 0.30 MAN71/DL707 à
74164 1. 7415170 140 | 745153 1.50 | 4036 250 | 80C98 0.75 15V 78L 15 0.30 СКО (Bicelour MAN4640
74165 f 74LS173A 100 | 745157 2.00 | 4037 1.10 > 1.00 | 74C925 6.50 MAN6610
74166 $ 74LS174 0.75 | 745158 2.00 | 4038 1.00 R 10 LBD 74C926 6.50 M 1 H
74167 4. 7405175 0.75 | 745163 3.00 | 4040 0.60 CHEER ый Bar Graph 74928 6.50 NSE S
74170 1 7415181 2.00 745169 5.50 4041 0.55 FIXEO REGULATORS Red 2.25 ORP12
74172 i 74.5183 1.90 | 745174 3.00 | 4042 050 LM309K А SV 1.40 Gree 2.25 | 241040 6.70 SFH305
74173 1. 7415190 075 | 745175 3.20 | 4043 060 LM323K ЗА 5V 3.50 TIL31A
74174 1. 74.5191 0.75 | 745188 180 | 4044 0.60 78HOSKC 5А бу 5.40 - TI
74175 А! 74.5192 0.80 | 745189 1.80 | 4045 100 78H12 5A 12V 6.40 ЕВ 205510200 | LM3914 3.50 TOS
74176 оо | 74151944 0.75 | 745194 3.00 | 4046 — 0.60 78Р05 10A 5V 9.00 КЕТИ 630 ИЯ A TiLB1
Me. Heo [v reise ы ло | dos 4080 VARIABLE REGULATORS 71729 1.00 | џ0м6118 3.20 оо
74179 150 | 7415196 0.80 | 745196 350 | 4048 055 LM305AH 2.50 FND357 1.00 | т
tov : 6 17300 1.00 UDN6184 3.20
74180 1.00 | 7415197 0. 745200 4.50 | 4049 036 LM317T 10-220 120 FNDSOO/TIL730 | MANr9'0 1.50 2
74161 340 | 7415221 745201 3.20 | 4050 0.35 LM3TK TOS 240 1.00] Манао: 250. 0.142003 0:99 OPTO-ISOLATORS
74182 1.40 | 7415240 745225 5.20 | 4051 065 LM3371 : 2% КЕТЕИН... J ULN2004 0.90
74184 180 | 7415241 0. 745240 4.00 | 4052 060 LM350T 10A * VAR 4.0€ С 100 DISPLAY vid
74185A 180 | 7415242 0. 745241 4.00 | 4053 060 | 7 7 ULN2802 1.90
Jioc mE ЕЕ 748244 400 | 4053 000 LM396K 10A 4 VAR 15.00 MAN?1/DL707 ME ULN2083 1.80
74191 130 | 74LS244 070 | 74825! 250 | 4055 ово TOHHOSRE SA SV x АО MIS M 100
74192 — 140 | 7415246 0. 745257 2.50 | 4056 08 78HGKC 5A4 VAR 6.50 MAN4640 2.00 eau
74193 115 | 74.5247 1. 745258 250 | 4060 070 78GUIC TAA VAR 2.25 15492 0.70
74194 $ 74.5248 745260 1 T
74198 080 | 745249 748261 200 | 4060 0% ТӘНСКС ЗА МАЯ 675 LOW PROFILE SOCKETS BY TI WIRE WRAP SOCKETS BY TI
74196 74.5251 0.75 | 745283 2.70 | 4067 2.30 meus pes. ane
74197 110 | 745253 0.75 | 745287 225 | 4068 025 SWITCHING REGULATIONS on. deb au dee сарп 22р goorn сп ырп бор .24pn 7Ub
74198 745256 0.90 745288 2.00 4069 0.24 ICL7660 2.50 lápin 10р 20pin 18р 28pn 26р 14рп 35р 20рм 60р 28р 80р
74199 2. 74152457400 | 745289 2.25 | 4070 0.24 563524 3.00 Юра dip: 'ézpn 208 “орип Зор | lean MWp 2269 бар. 4Opin^foop
74221 j E 0.70 | 745299 459 4071 . 11494 100 Е —
74251 1. 74.5259 1.20 | 745373 4.00 | 4072 o. L497 | ,
74259 1. 74.5260 0.75 | 745374 4.00 | 4073 . 78540 2.50 DOM SKTS, ps ace renin = рп Р ү А
74265 0. 74.5266 0.60 | 745387 2.25 | 4075 . RC4195 1.50 Е :
F PLEASE ADD 50p p&p & 15% VA
ECHNOMATIC Li Tb ЗЕ ADD Sop pip & 15% VAT
MAIL ORDERS TO: 17 BURNLEY ROAD, LONDON NW 10 IED O:ders from Government Depts. & Colleges etc. welcome
ENTER 83 ON REPLY CARD
Tel: 01-723 0233 4 lines. Telex: 922800
SHOPS АТ: 17 BURNLEY ROAD. LONDON NW10 = Detailed Price List on request
305 EDGWARE ROAD. LONDON W2 Minimum Telephone Order £5
Stock stems аге normally by return of post
ELECTRONICS & WIRELESS WORLD 427
Tone decoding using a
microprocessor
A simple approach to microprocessor-controlled tone decoding
results in excellent performance in noisy conditions.
operate through a repeater site over-
looking the service area. So that many
user groups can use the same r.f. channel
through a particular repeater, it is common
for user groups to be allocated a certain
sub-audible tone which is continuously
transmitted along with the speech. This
continuous tone-controlled suppressed
squelch, abbreviated t.c.s.s., enables the f.m.
receiver output only for that particular user
group. In this way, users are not subjected to
a torrent of unwanted transmissions. The
system commonly uses one of about thirty
tones in the band 67 to 250.3Hz.
Because decoder input noise comes from
an f.m. receiver, the noise characteristics are
difficult either to calculate or to measure.
This article discusses measurement of f.m.
noise characteristics of a typical f.m. mobile
receiver and specific microprocessor techni-
ques used to produce a useful decoder.
Two basic approaches to implementation
are period measurement which is capable of
modest s-to-n ratio performance for tones
up to around 10kHz, and correlation filter-
ing giving excellent s-to-n ratio performance
for tones up to around 500Hz.
Quality of the output voice channel is
measured by means of a sinad meter giving
signal + noise + distortion/noise + distortion
and this measurement is done at lkHz.
Sensitivity of an r.f. receiver is commonly
defined as that r.f. level which gives a 12dB
sinad reading on the audio output. A charac-
teristic of any f.m. receiver is that output
Levee radio telephones usually
Noisy
input
Reference
waveshape
Quadrature
reference
waveshape
428
C.H. GOUGH
signal quality degrades slightly towards the
12dB sinad point as r.f. input level is de-
creased, but then degrades very rapidly
below that point. Further, the output noise
characteristic is ‘clicky’ or ‘raspy’ and quite
different to Gaussian noise.
For a mobile receiver, signal level varies
rapidly by perhaps 20 or 30dB as the vehicle
travels down the road. Any decoder must be
relatively immune to noise bursts from this
variation, and yet capable of detecting the
presence or absence of tone within about
250ms. Further detection bandwidth may be
Noisy input
Sampled analogue
delay line with
Clock
Reference
waveshape
limited to +2.5% or less. References one and
two partially define the characteristics of
sucha decoder.
Usually decoders like this are preceded by
an analogue filter, then a hard limiter to
remove decoder dependence upon the audio
signal level. However, this process is very
non-linear — it removes some noise spikes
and emphasizes others. Also the analogue
filtering never completely suppresses voice-
channel signal and the hard limiter can
emphasize this problem.
With the introduction of microprocessors
into f.m. land-mobile radio telephones, it is
necessary to design an optimum tone decod-
er using a microprocessor. Reference 3
describes one attempt at a practical imple-
mentation.
Filtered
output
Peak level
detector and
comparator
dc output
бс. level
comparator
Fig.l. Two basic implementations of a
correlation detector — a matched filter at
top (a) and a quadrature correlator at
bottom (b).
ELECTRONICS & WIRELESS WORLD
GENERAL CORRELATION
Two basic approaches to the detection of a
tone are shown in Fig. 1. Іп (a), the matched
filter uses the complete stored replica of the
reference waveform after each shift through
the shift register to determine correlation
between the reference and the incoming
signal. Between each sample, n multiplica-
tions and n additions must Бе performed. In
Fig. 1 (b), after each sampling, only two
multiplications and two additions into the
integral are required.
This approach however inherently in-
creases decoding time. At the end of the
integration period, the integrators are reset
to zero. If the incoming sinusoid started at
the middle of the integration period, it is
unlikely to be recognized for 1% integration
periods; worst-case delay approaches two
integration periods.
A matched filter gives optimum detector
performance in the presence of Gaussian
noise ^". Figure 2 gives the basic frequency
behaviour of such a filter and Fig.3 shows
typical amplitude response as the normal.
ized input frequency is swept from zero to 2f.
There are two important features of Fig.3:
For low values of n the output is skewed,
which is quite correct. As n becomes large,
the integral approaches the Fourier trans-
form, the curves approach sinx/x and the
asymmetry disappears.
— If a sinusoid is cross-correleated with
another sinusoid, frequency selectivity is
poor unless many cycles are used.
As the number of cycles cross-correlated
is pushed up, so is filter selectivity. However,
two other factors are important. Firstly the
number of taps along the delay line is not
infinite, because finite time is required for
generation of the integral. Secondly, the
filter can respond to multiples of the fun-
damental because of aliasing.
From the Nyquist criterion at least two
samples per cycle are required at the max-
imum frequency. However for equal sam-
pling at two samples per cycle, the relative
phase of the reference and the incoming
sinusoid is important, since a phase shift of
90° makes the difference between full output
and no output from a matched filter.
Referring to Fig. l(a), output sample
sequence E(k) from the stepped delay line is
M-I
У = (flk—n) hin)
0
з
where К is output sample number, incom-
ing sinusoid ЯК) is cos((k2a/M)+8), filter
correlation pattern h(n) is cos((n27/M)+8),
and Ө, 8 are relative phases.
M-I T
Е У Vicos| "52" 2n+0-8]+
Vocos [ones]
fe
= соз [&2т+ө+8]+
M-1 -
“ж cos [2m ee]
ELECTRONICS & WIRELESS WORLD
Input signal
m!
(a)
At 8-0
т К
1 = Í cost cosft dt
т
where f is the normalized frequency
difference between the incoming and
reference sinusoids
n
I =f 1 cos(1-f)t + $ ©05(1+{7)+ dt
E EF) sin (tf + (гр) sinis т 571
п Ғ=1,-1
A very large
number of taps
At 8-0
1: [сов nt cos nft dt
Er
where n is fne number of cycles used by
fhe matched filter
T
=. 1 u 1 И
1 "Л z 60$ (1-1 nt + т cos UO f)nt
. Sin(l- fom, sio(lef)or #1, -1
n (1- f) n (If)
|
|
| =n f=1,-1
L
Fig.2. Tapped delay line detector using a single sinusoid cycle (a) and using multiple
sinusoid signals (b).
Cycles Half - power bandwidth |
1 0-84
2 0-4366667
4 0:22
8: 666666Е -02
LIZED 07Р
NORMA
NORMALIZEO I/P (FREQUENCY)
Fig.3. Peak output and half-power bandwidth for the detector of Fig.2 (b) using 1,2,4 and
lOcycles.
The first term is desired output, while the
second is an error term. If M—3, then the
second term is zero so the minimum integer
sampling rate is three samples per cycle.
Figure 4 gives plots of proportional band-
widths versus number of cycles in the
matched filter Гог a number of waveshapes.
As the waveshape used for cross-correlation
progresses from a sinewave to a 1:1 square-
wave then to a 16:1 rectangle wave (all of
zero mean value), fewer and fewer cycles are
required to achieve a given bandwidth. The
limit is reached when the waveshape used is
reduced to an impulse; in this case, barely
more than one cycle is required to determine
frequency of the incoming waveshape.
Such selectivity is bought at a high cost
Since a correlation detector like this will
respond to almost any incoming signal or
noise. А sinusoid waveshape gives excellent
noise immunity and rejection of harmonics,
but from Fig. 4, a bandwidth of 596 (i.e.
+2.5%) requires 16 cycles for correlation.
Figure 4 includes the curve for the common
analogue filter approximation for rise time.
If incoming signal f(t) consists of N cycles,
each cycle with period T, then energy in the
ensemble, E, is
» NT >
| f а=] f “(t)dt
0
2т
EI | f(9)d0.
Table 1 shows this evaluated for four particu-
lar waveshapes. If it is accepted that filtering
over a number of cycles will reduce noise to a
Table 1. Sine and squarewave zero means.
Waveform, Energy in Scaling
zero mean wavetrain factor К
Sine ТМА? 1
Rectangular 1:1 2тТМА? 2
1;7. 0.2857тТМА? 0.2857
1:15 0.1333: TNA? 0.1333
429
0:5
о
N
ean = €
01
0:02
PROPORTIONAL BANDWIDTH Ад,
$
0-01
NUMBER OF CYCLES (Муг)
Fig.4. Numerically calculated graph showing the relationship between correlation
waveshape and normalized bandwidth.
near-Gaussian noise characteristic, then
standard matched filter theory may be used.
Average s-to-n ratio for a sinewave plus
noise is
А2/2,
№
Standard matched filter theory gives the
peak-output s-to-n ratio as
Ѕ№МКАу= =
where т is noise spectral density with white
noise characteristic, N, is total noise power
and B is noise bandwidth. Substituting from
Table 1, then for the previous equation.
SNRo p =2 En TNA'K -4nB.TNK.SNR
Design of a tone decoder for the t.c.s.s.
application revolves around a trade-off be-
tween bandwidth given in Fig.4 and factors
T, Nand К in the previous equation.
If limited spurious response to odd har-
monics can be tolerated, then the square-
wave has a clear s-to-n ratio advantage over
other waveshapes.
However, for the t.c.s.s. application, the
reference may be rectangular but the in-
coming signal is merely a hard-limited
noisy sinusoid. For low s-to-n ratio opera-
tion, the reference waveshape should
emphasize the signal where the peak of the
sinusoid is.
In practice the reference waveform is not
critical; a rough three-level or five-level
approximation to a sinewave is quite accept-
able.
430
PERIOD MEASUREMENT
If the incoming signal is relatively noise free
before hard limiting, a microprocessor
equipped with a hardware timer can readily
make a period measurement to an accuracy
of the maximum instruction execution time.
Thus, an incoming sinusoid period can be
determined accurately to within a few mic-
roseconds if the sinusoid is guaranteed to be
free of any d.c. or transient offset. This is
most easily implemented if the microp-
rocessor is given an interrupt pulse on each
positive (or negative) zero crossing; this is
approximately equivalent to the incoming
tone being reduced to an impulse.
For a high s-to-n ratio, probability density
of zero crossings can be found if some
approximations are made:
— If the noise passband extends beyond the
frequency of the sinusoid to be decoded,
then distribution in time of one zero
crossing is statistically independent of the
previous zero crossing.
~ Around the point of the zero crossing, the
sinusoid may be approximated by a
straight line of slope Aw.
— The noise voltage has a Gaussian distribu-
tion.
- There is only one zero crossing per half-
cycle.
This requirement implies a high s-to-n ratio
and a relatively low upper cut-off frequency
for the bandpass filter.
A noise voltage sampled infrequently with
respect to the upper cut-off frequency of a
passband filter has this Gaussian amplitude
distribution
муд) = voce – 1
where с is the r.m.s. voltage and p the
mean direct voltage.
z
At the point of zero crossing of a sinewave,
the amplitude distribution of sinewave plus
noise can be scaled to give a distribution in
time at the instant of zero crossing.
g,- 9X2 9v.
Aw А2т
when normalized toa frequency of 1Hz.
Input s-to-n ratio should be such that the
instant of zero crossing is within a certain
error bound А. For example, a t.c.s.s. system
may require a 596 bandwidth so A is +0.025
in this case. Since the point of interest is at
the zero crossing of the noise-free sinewave,
the mean p is zero and the error limit on the
time axis is:
йе. AU
Ат ^ o 2mÀ
1 А : S 1
SNR= (4) — SNR = 2. p
However, if the decoder averages the periods
over each cycle, then the required SNR;
reduces by V/N where N is the number of
cycles:
SNR; hr.
For the example of a 596 bandwidth, SNR;
reduces to 5.5 for 16 cycles. This derivation
is not suitable for use when s-to-n ratio is
less than four. It does however indicate that
at modest s-to-n ratios fast decoding is
possible. Further, using a small timer
interrupt-service routine it is possible for a
microprocessor to directly decode a 10kHz
tone without use of aliasing techniques.
DISTRIBUTION OF ZERO CROSSINGS
Figure 5 shows the arrangement used to
measure the period between adjacent posi-
tive zero crossings of the output signal from
an f.m. receiver. It is necessary to eliminate
all noise contamination from mains fre-
quencies for these results to be valid.
Figure 6 shows normalized distribution of
periods between successive positive zero
crossings. The normalized measurement in-
tervals were 0.05 and 1000 samples were
taken for each curve. These graphs show that
a received tone is more likely to be con-
taminated by a spurious zero crossing if it is
low in the analogue-filter passband.
For the particular receiver, the 12dB sinad
sensitivity is — 118dBm. At this level, prob-
ability of correct detection of a tone by
period measurement, i.e. correlation with
an impulse-like reference, is poor, particu-
larly when the tone is low in the filter
passband.
These results indicate that best decoder
performance is achieved when the most
analogue filtering is done before hard-
limiting the signal.
To be continued.
ELECTRONICS & WIRELESS WORLD
References
1. EIA RS220-A Minimum standards for land
mobile communication continuous tone-
controlled squelch systems (CTCSS), Electro-
nic Industries Association 1979.
2. MPT1306 Code of Practice, Continuous tone
controlled signalling system (CTCSS) for use in
the land mobile services, HMSO, London 1978.
3. Labedz G.P., Continuous tone-coded squelch
system implemented in an eight bit micro-
computer, International Conference on Com-
munications, Denver, Colorado, June 1981.
4. Introduction to communication systems, F.G.
Stremler, Addison-Wesley 1982.
5. Communication Systems, S. Haykin, Wiley
1983.
6. Turin G.L., An Introduction to Digital Matched
Filters, Proc. IEEE vol. 64 no 7, July 1976.
7. Rice S.O., Mathematical analysis of random
noise, BSTJ23 (1944) pp.282-332 and 24 (1945)
pp.46-156.
8. Rice S.O., Statistical properties of a sinewave
plus random noise, BSTJ..
9. Rice S.O., Noise in f.m. receivers in the sympo-
sium proceedings of time series analysis, ed. M.
Rosenblatt, pp.395-422, Wiley 1963.
10. Roberts J.H., Angle modulation: The theory of
system assessment, IEE Telecommunications
Series 5, Peregrinus 1977.
11. Tozer T.C. and Kollerstrom J., Penalties of
hard decision in signal detection, Electronics
Letters, vol.16 no5, 28 Feb 1980.
Chris Gough works as a design engineer with
Tait Electronics in New Zealand. Before that
he worked as an electronics technician for
the DSIR, and in 1984 he gained his BE
(Hons) from the University of Canterbury.
His interests include r.f. design, signal pro-
cessing and instrument design.
200mV to SVp.-p
(must not clip)
Signal f.m.
generator receiver
Butterworth &th order
S0Hz to 325Hz
Modulated at
rate f.m.
Square
wave
generator
MC 14013
MC 14520
+ 00-0)
Personal computer
Fig.5. Hardware test arrangement for measuring the period between adjacent positive
zero crossings.
Fig.6. Normalized distribution of periods between adjacent zero crossings in a noisy f.m. signal
using 1000 samples for each curve and 0.05 measurement intervals.
— 400
500-
400
300
SNRie = 208
No carrier present
ELECTRONICS & WIRELESS WORLD
300
200 SNR, = 008
100
SNRie = -2dB
431
LLOYD
RESEARCH
LTD
This catalogue describes three cost-
effective eprom programmers for R&D
and production. The L2100 can program
two devices with different data simul-
taneously. There is also a larger eight
socket version with 2M bits of ram. Both
versions have full editing facilities and
RS232 ports. They progra
1M bit and 87C64, 63701V
eproms to
and 63705V,
2532(A). etc. There is also a production
copier. Prices from £895.
WEST HYDE
CIRCLE 68
FOR FURTHER DETAILS.
The largest West Hyde catalogue is now
available with details of the largest and
most comprehensive range of enclosures
and accessories in Europe. lt contains
over 100 pages describing everything
from 19" equipment to small, general
purpose cases as well as handles, knobs,
opto-electronic components and panel-
ware.
This edition includes many new items
and important additions to existing pop-
ular product ranges.
ENTER 67 ON REPLY CARD
Happy Memories
Part type
4164 150ns Not Texas
41256 150ns
41464 150ns.
2114 200ns Low Power
6116 150ns Low Power
6264 150ns Low Power
2716 450ns 5 volt
2532 450ns...
2732 450ns....
2732A 250ns .. T
2764 250ns Suit BBC
27128 250ns Suit BBC.
27256 250ns
Low profile IC sockets: Pins
Pence
1 off 25-99 100 up
.95 .90 .87
.2.15 1.95 1.85
3.35 2.99 2.79
1.75 1.60 1.55
1.40 1.25 1.20
.2.40 2.15 2.05
(275 2.60 2.45
‚5.40 4.85 4.50
‚2.60 2.40 2.25
3.30 2.85 2.75
.2.45 2.20 2.05
‚2.75 2.60 2.40
3.70 3.45 3.30
8 14 16 18 20 24 28 40
5 9 1011 12 15 17 24
Please ask for quote on higher quantities or items not shown.
Data free on memories purchased, enquire cost for other
Write or ‘phone for list of other items including our 74LS series
and a DISCOUNT ORDER FORM.
Please add 50p post & packing to orders under £15 and
VAT to total. Access orders by ‘phone or mail welcome.
Non-Milltary Government & Educational orders
welcome for minimum invoice value of £15 net.
HAPPY MEMORIES (WW),
FREEPOST, Kington,
Herefordshire HR5 3BR.
Tel: (054 422) 618
(No stamp required)
ENTER 71 ON REPLY CARD
432
e DATABANK e.
SEMICON
INDEXES
SEMICON
INTERNATIONAL
SEMICONDUCTOR
INDEX
CIRCLE 7
FOR FURTHER DETAILS.
. This index quotes the major character-
istics and maximum ratings of over
85,000 international types of both dis-
crete and integrated semiconductor de-
vices.
The index is in three volumes in a
loose-leaf format to enable updating from
a service offered by the publishers.
Volume 1 is on TRANSISTORS, Volume
2 on DIODES and SCRs and Volume 3 is
on digital and analogue INTEGRATED
CIRCUITS.
In addition, each volume contains pin-
out diagrams and alternative manufac-
turers and distributors.
CARSTON
ELECTRONICS
We sell all types of test equipment from
the simplest to the most sophisticated and
specialised.
All of the high quality second user
equipment we supply is fully calibrated
and meets the manufacturers original
specification. All equipment is fully
guaranteed.
We also buy good quality under utilised
equipment.
ЕЕ
C$ooOO!unooconoogdoooonnooooóoooo EI
VALVES AND TRANSISTORS
Telephone enquines for valves, transistors, etc
Retail 749 3934. Trade and Export 743 0899
FIELD TELEPHONE, CABLE TYPE 010
FIELD TELEPHONES TYPE ‘J’. Tropical, in metal cases
10-1пе MAGNETO SWITCH-BOARD. Can work with
every type of magneto telephones
POSTAGE AND PACKING CHARGES: £1-£3 50p, £3-£5 бор, £5-£10 80p, £10-£15 £1.00, £15-£20 £1.50.
Over £20 £2.00 but below 2kg Parceis over 2kg at Cost
ie aoe abet ep eb НЫ
28222225EZzZ5
aco
eéucuacou
4.60 | вот"
6.25 | 812A
NEW PYE EQUIPMENT
& SPARES
HARNESS "A" & "B" CONTROL UNITS
"A" "Я" "J17 722,
Microphones No 5, 6, 7 connectors, frames,
carrier sets, etc.
COLOMOR (ELECTRONICS LTD.) 170 Goldhawk Rd, London W12
Tel: 01-743 0899 or 01-749 3934. Open Monday to Friday 9 a.m. - 5.30 p.m.
ENTER 78 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD
Luca wi Ha SOR atta X LA
оооло o uio e e ч
© eo
(OUDoopoounoooo
“|
LOW COST DESIGN TOOLS
FOR ENGINEERS
Why should EPROM Programmers and similar devices be so expensive?
We have found two products which beat all the price barriers.
OCTAGON EP-8 8 GANG OCTAGON EP-1
EPROM PROGRAMMER £499 EPROM SIMULATOR £399
This highly acclaimed German product measures only Turn your IBM PC into an EPROM Simulator and develop
270 mm x 170 mm x 30 mm high. Its strong metal programs for any microprocessor system — without
construction and simplicity of operation makes it equatty tedious EPROM burning and without the high cost of an
suitable for a production or development environment! ССЦ emulator.
© 8-gang simultaneous copying —— @ Add-in card simulates up to 64K bytes of EPROM
@ all popular EPROM makes and sizes y @ ribbon cable connects to your target microprocessor's
@ 32 character alphanumeric display ‘ne EPROM socket
© RS232 down-line-load fadi Ф accepts binary or hex load files
The first truly professional E b th ББ ( }Weran also supply most cross- assemblers/compilers to
the £500 price barrier! | || таква complete low cost development system.
Programmer: Enter 43 on Reply Card
Simulator: Enter 44 on Reply Card
Engineering Solutions Limited, King's House,
18 King Street, Maidenhead, Berks. SL6 1EF
Telephone (0628) 36052 Telex 84962 Fax (0628) 74928
SMALL SELECTION ONLY LISTED — RING US FOR YOUR
REQUIREMENTS WHICH MAY BE IN STOCK
е ————————————- ———
Racal Solid State Communication Recel- Telephone seis type F L and J - large quantity
vers - RA1217 — Mechanical digit readout 1 n slock £6 to £15 depend: ол апа
30MC/S £300. Racal RA17L Communi- quantity, РОН Don 10 Telephone р -
cation Receivers SOOKC/S to 30MC/S in 30 half mile canvas containers
bands 1MC/S Wide - £175 - All receivers are air Viewing infra-red riscopes
tested and calibrated in our workshop eyepiece 24 vot DC supply £100. 1
supplied with dust cover operation Original cost to Government over £11,000. EA
instructions — circuit — m fair used condition Static Invertors — 12 or 24 volt тры - 240 volt
Racal Synthesisers — (Decade ^ frequency AC sinewave output — various watteges. P.O.R
nerators) MA250 - 1.6MC/S to 31.6 MC/S - XY Plotters and pen recorders vanous
100. MA lor use with RA17 receiver P.O.R. Signal Generators various РОА
£100. MA2 - precision frequency standard TF 893A Power meter £50. Racal
5MC/S MOS 100KHz — £100 to £150, RA137 frequency counter type 836 £50. Tektronic
апа ВАЗ? ~ LF convertors 10 to 980KC/S ~ £40 plug-ins — 1A1 £50. 1A2 £40. 1A4 £100. M £50
to £75. RA98 SSE-ISB convertor – £50. RA121 Al items ае bought direct from Н.М
SSB-ISB convertor ~ #75. Plessey PR155G Govemment bei Surplus equipment. Price ts
Solid State receivers — 60KC/S — 30MC/S - £300 ex works SAE ior enquines. Phone Юг
Transte! Matrix Printers AFIIR 5 level appointment ie demonstration of any items
baudot code ~ up to 300 bads — юг pnnt out on also availability or price change УАТ. and
plain teleprinter paper £50. Army Field carriage extra.
EXPORT TRADE AND QUANTITY DISCOUNTS
JOHNS RADIO, WHITEHALL WORKS,
84 WHITEHALL ROAD EAST, BIRKENSHAW,
BRADFORD BD11 2ER. TEL NO: (0274) 684007
WANTED: REDUNDANT TEST EQUIPMENT - VALVES - PLUGS - SOCKETS,
SYNCHROS ETC. RECEIVING AND TRANSMITTING EQUIPMENT
L- C- R Meter
0,1 uH — 200 uH
1 WH — 2 mH
10uH- 20mH
100 uH — 200 mH
1 mH — 21H
0,1 pF — 200 pF
1pF- 2nF
10pF— 20nF
100 pF — 200 nF
1nF- 2uF
10nF- 20ygF
100 nF — 200 uF
R: 0,1 Ohm — 200 Ohm
1Ohm- 2kOhm
10 Ohm — 20 kOhm
100 Ohm — 200 kOhm
1kOhm- 2 MOhm
10 kOhm — 20 MOhm
Tel: (0822) 853585 DIPL.-ING FRANZ BRAUNSCHMID
ol aah МАТ Inzersdorferstr. 119/23, А-1100 VIENNA, AUSTRIA
ENTER 35 ON REPLY CARD ENTER 39 ON REPLY CARD
холла SSSA яна 15.555 el
IEEE 488 CONTROLLERS FROM
MOORDENE ASSOCIATES
TTTPTPTPPRRRRRRRRRRRRSRRRISISSRRRRSRARRRSRRRAAI
IBM PC and clones including Amstrad PC1512.
Half length interface card, software including Turbo Pascal. IEEE 488 cable and
Comprehensive operating manual £270
Acorn ‘В’ and Master
Interface in separate case, software in PROM, IEEE 488 cable and comprehensive
Operating manual £250
New software for existing owners of Acorn GPIB controllers which offers compatibility
with the new IEEE 488.2 standard £28
All controllers olfer a command structure which follows the IEEE 488.2 standard. This
simplifies the control cf existing GPIB devices, reducing the number o commands
needed and Is compatible with new devices using IEEE 488.2 fo:mat commands
Designed, manufactured and supported in Great Br tain
***»»*2?
*
*
*
*
*
®
*
For more information contact
„МООВОЕМЕ ASSOCIATES
Axtown Lane, Yelverton, Devon PL20 6BU.
ELECTRONICS & WIRELESS WORLD
433
High-resolution
monitor
Designed for use as the basis of a
graphics workstation, the CBT Ultra-
high resolution monitor will find
uses in cad/cae, electronic
publishing, document storage and
retrieval and the like. The monitor
has a rotatable screen which can be
used in the upright – ‘portrait’, or
horizontal – ‘landscape’ modes and
the housing includes tilt and swivel
for ease of use.
The monitor has a 300MHz video
bandwidth and a raster format of
2301 lines with 1728 pixels/line. This
works out at about 8 pixels/mm (or
200 per linear inch) and the
company, Consolidated Business
Technology, claim tobe the only
monitor manufacturers who keep a
magnifying glass in their showroom!
The monitor includes a frame-
store memory for four images
(16Mbit). The refresh rate is 100Hz
(2:1 interlace); line rate is 125kHz
and the video rate is 288Mbit/s. The
video ram has 8-bit direct memory
access with a data rate of up to
5Mbit/s. It is possible to read to or
write from any byte in the four pages
and to dump any of the pages toa
printer.
EW PRODUCTS
Analogue c.a.d.
New from Hi-Tek CAE is the Daisy
Analog Design series of advanced
c.a.e. tools which make the analogue
design cycle faster and easier.
The system is based around
Dspice, Daisy's circuit simulator,
which provides a fully-functional
analogue simulation which is easy to
use and takes all its parameters from
the entered circuit diagram.
During analysis, Dspice can
perform the functions of voltmeters,
ammeters, multi-channel
oscilloscopes, network analysers,
and other familiar laboratory
instruments. Engineers can perform
d.c. time and frequency domain
analyses, including a wide range of
common subanalyses such as d.c.
transfer curves, Fourier analysis, and
noise analysis. Dspice can also be
used for sensitivity analysis,
providing key information on critical
design elements that cannot be
obtained through traditional
breadboarding.
The Daisy Analog Design series
also includes ChipSim, an optional
high-speed circuit-level simulator
for transient analysis of digital 1.5.1.
and v.1.s.i. designs. ChipSim uses
advanced relaxation algorithms
The company tells us that their
design goals were (a) no compromise
on the image quality and (b) ease of
interfacing to other equipment. They
believethat they have achieved both
of these. There is a wide range of
optional peripherals, mainly for
memory storage (e.g. optical discs),
input (document digitizers), output
(high-resolution plotters) and
communications including
interfaces for VME, facsimile and
Ethernet. There is to be an adaptor
card for IBM AT-like computers, and
a larger monitor able to display АЗ
documents with 8Mbits/image.
Consolidated Business Technology
Ltd, 14 Parkside, Ringwood
Industrial Park, Ringwood, Hants
ВН24 350.
Tel: 042547014.
which are optimized to deliver
detailed circuit information at speeds
significantly faster than multi-
function DSPICE algorithms.
Hi-Tek CAE, Beadle Trading
Estate, Ditton Walk, Cambridge, CB5
8QD. Tel: 0223215055.
NEXT MONTH
Logic analysis. A logic analyser is
one ofthe essential tools in the
design, testing and monitoring
of digital equipment. Our feature
\discusses the use and application
ofthe instrument.
Marx generator. Ап inexpensive
method of generating unipolar
pulses of several million volts
amplitude at very high currents.
The incredible Scophony.
Mechanical systems of television did
not come to an end after the 30-line
Baird transmissions in 1935. Tim
Voore describes the Scophony back
projection system that provided a
33 in-diagonal picture in 1938.
Current, or voltage? Joules Watt
asserts that nothing is pure and very
little ever simple, so that there is
434
Experimental
high-voltage
generator
measurement
Coprocessors
for the 68020
power mos
and bipolar
devices
=== =
Morse —the
American
Leonardo
often confusion over whether
amplifiers amplify voltage or
current, or a mixture of both.
Building blocks in active
compensation. Single op-amp, first-
order blocks for the realisation of
actively-compensated amplifiers and
integrators.
Power mos v. bipolar. It is possible
that power mos will gradually replace
bipolar power devices. This article
offers a comparison of the two
technologies.
Colour graphics controller. John
Adams discusses interfacing the
VSDD colour-graphics controller to
produce a high resolution graphics
board with RGB output at one end
and microprocessor-bus signals at
the other.
ELECTRONICS & WIRELESS WORLD
Soldering to solder
The problem of soldering metal
components to an existing pre-
soldered joint has been solved by the
use of abismuth-tin alloy witha
melting point well below that of
ordinary solder. Melting at 137°C,
the alloy is used in an extruded wire
form to ensure the accuracy
frequently necessary when soldering
components for electronic
equipment. The manufacturers can
adjust the composition of the alloys
across a wide range of low melting
points, anywhere between 20? and
300°C. MCP 137 – one of the most
popular alloys in the MCP range - has
the further advantage, unlike
conventional solder, of having no
lead content. Mining and Chemical
Products Ltd, Alperton, Wembley,
Middlesex HAO 4PE. Tel: 01-902
1191.
Conveyor system for
automatic soldering
Closed-loop conveyor lines are the
speciality of PAF Ltd. Each of the
lines, in atypical installation, is ona
single level in the shape of a
rectangle, and uses PAF's twin-tape
conveyors to transport the cards
which are fitted in jigs on carriers.
This highly-efficient closed-loop
system incorporates PAF's 90? twin-
tape transfer units at three corners,
automatically synchronized with the
carriers, and an Electrovert flow-
soldering and board cleaning
machine. |
To facilitate the processes involved
in flow soldering and cleaning, the
boards are raised as they pass
through the machine, and a higher-
level conveyor takes the carriers a
short distance to a PAF twin-tape lift
and transfer unit.
The component inserters sit along
the outside of each line and are in
easy reach of the parts, which are
held in 10 or 20 tray, foot-operated
PAF rotary carousels located
opposite them on the inside of the
line. PAF Systems, Sanders Road.
Fineden Road Industrial Estate,
Wellingborough, Northants NN8
ANL. Tel: 0933 222195.
Soldering
equipment
Arange of tools, machinery and
materials for soldering is available
from Solbraze Ltd. They produce a
wide range of soldering irons from 30
to 500W; flame, induction and
resistance heating tools; andalarge |
number of different solder pots for |
dip soldering. The company
specialises in tailoring machines and |
jigs for specific applications.
Solbraze Ltd, Bilton Road, Erith,
Kent А8 2AN. Tel: 0322 341411.
ELECTRONICS & WIRELESS WORLD
Robot for solder masking
A low-cost robot has been developed
for the application of solder-resist
materials to printed-circuit boards.
The Polar Robot comes from
Crantech Robotics. The machine can
be programmed easily and quickly on
the production line to deal with any
spot-masking configuration
required, in any combination of
mask patterns — lines, dashes, dots,
squares, etc, as intricately as the
application requires.
In batch production, the machine
| canrecall anumber of preset
programs at the touch of a button.
| Evendifferent combinations of head
thickness can be incorporated into
the same program by use of an
inbuilt device known as the speed
multiplier. The Polar is claimed to
carry out its task far more accurately.
swiftly and economically than is
possible by hand application.
Asthe robot can deal accurately
with solder masking. it can also be
used for other applications, such as
the dispensing of solder paste.
adhesives and encapsulating
materials. All that is needed is a
change of dispensing valve and
product feed line; the substitution of
solder paste (or adhesives or
encapsulant) for solder mask; and
calling up of the appropriate
program. At its basic installed price
of around £13 000, payback is
between six and eighteen months,
depending on the type of application.
Crantech Robotics Industrial
Systems Ltd, Unit D3, Gedding Road,
Hoddeston Herts EN11 ONT. Tel:
0992 445935.
Soldering thermometer
Where the temperature of a soldering
iron may be critical, it is possible to
use the WSI 500 thermometer. It has
a built-in sensor mounted on the
front panel, surrounded by a bit
cleaning sponge, with a liquid-
crystal readout. The instrument has
a temperature range of —50to
+750°C, with an accuracy of 0.596
(+1 digit) calibrated to BS4937.
West Sussex Instruments Ltd, 12A
Corc nation Buildings, Brougham
Road, Worthing, W. Sussex BN11
2NW. Tel: 0903 212303.
Static-free
desolderer
A low-cost static-free desoldering
tool has been added to the anti-static
range of OK Industries. It has been
manufactured in accordance with UL
and MIL standards and satisfies MIL/
B/817025 2nd barrier electrostatic
free material requirements. lt is
provided with a bayonet type
conductive tip which is easy to clean
and change.
The DP3 is available ex-stock and
costs £5.75 (+ tax & delivery). Tips
are 95р. OK Industries UK Ltd,
Dutton Lane, Eastleigh, Hants SO5
4SL. Tel: 0703 619841.
ORAS + AER ee
Hot-air resoldering
Designed for repairing surface
mount boards, the new System 1000
uses directed hot air exhaust to
desolder and resolder s.m.ds and
dual-in-line components. The
system features an X and Y board-
holding mechansim on linear
bearings, with a panel size from 0 to
600 by 400mm and two hot air tubes
which can be individually extended
or retracted by means of a control
knob. Additionally, the temperature
of either of the tubes can be
individually controlled, for a
particular application.
The System uses a blower fan to
pass air through both the upper and
lower tubes, each of which is
equipped with a heat controller to
monitor the temperature of the air as
it passes through thetube. Oncethe
tubesare extended forward, hot air is
directed through a special disc plate
fitted to the tube's endand onto the
substate for repair. The system has
been designed to be portable, and
weighs only 10kg. Sohlberg-Surtech
Ltd, Intec 2, Wade Road,
Basingstoke, Hants RG24 ONL. Tel:
0256 470848.
Wave soldering
Good soldering is combined with
pleasing design and good, sound
manufacture in the lemme Italia
range of wave soldering machines;
according to Electrautom Ltd, who
are the UK agents.
The IM range is well established т
Europe but is newly imported to the
UK. Their design has improved the
image of such machines which are
traditionally dirty and smelly
Electrautom Ltd, Etom Buildings,
Quarry Wood, Aylesford, Kent ME20
| 7NA. Tel: 0622 70188.
435
LANGREX SUPPLIES LTD
limax House, Fallsbrook Rd., Streatham, London SW16 6ED
RST те!:01-677 2424 Telex:946708 RST
вотка гун ! MJE MU 11€226l 1.20 ZIX 4 2.
i Ч BD?17 BFW MJE370 s ШЕР ý D ТАМЫ Жан
ASLI0 р ВРэ\к ШАМ г [ мез Е ПРЗУА s f zix% 2 2 EN
А5717 › BDX10 BEXsi 2 MJESPU ПІРА 1х5 ШЕ
ASZM 1ч E вр? > BARKS — 02) MIS?I ПРА 0 INUIA INIAN
7 t BDYI ? BE XN7 2 МИ: 2955 11Р32А : IN" I^ 3 ? 022 БОЗ
BDY x ! BI Ххх МЈЕ M55 $ ПРАЛА ШЕП АТ) INAS
BDYoo ВРУ 2 MPPI < ИРЗА IN4O0? (ц мам
REIS BEYS) р МРЕНЫ ПРА — 03 мз м [ >м 5 NAN
Hl 152 BrYs? 4 MPI 105 E 12А 2 ІМ мы эмэ эми?
BIST ВРУ MPSAt6 IPO INAUUS н | 2N2:9 2N4124
BE 154 Hr yog МРУА 56 ocn 11Р117 мин ч 2N21s4 4 2N4126
HFIS9 BSX 9 MESUOT | 1 TIPI25 ) {мл 005. Е Эм424%
BEIM р BSN» 2 МРУ TIPIN s Fins oe f миц 2N42KK
BF loh 5 BSX?I 2 MPSU Sh ПРИ! IN414x Т 2N200: j ману
BC107 BEIA? B1 106 у NESSS ПР? INSU IN? NIS эми
ВСТО Р BF173 ВГУ шек NK 14 7 TIPIS Г экз» эман
вө 4 : ? ni? ЕП NKT403 5 1 р 11Р137 ) ! 2N2007 ? JN 4402
BCH A BFI7K BUH NK 1408 ^ ПР!40 «5 ! 3N?9?4 t 245457
BCII4 ; Br179 I BUMA 2 OAS E TIPIS ` 9 2 2N2925 ON 545
BCIIS 2 BE Ix) \ ПАШ ОА? f ТІРІ42 2№2926 25459
ВС Y ВЕ! ? BY 1% ОА S ; Т1Р2955 мик 95017
ВС117 " BFIx? ВҮ177 Aa? $ ? 5 ГЕР?95%Т ‹ RT 5 EN ] ET
BCIIS J 42 ВЕ! хз BZX^I ' OA 2 ОС12 TIPMISS [ 28024
ВС125 0.35 [Im Series ОА7ч TIPMISST® 0.4 2 55125
ADI BCI36 35 à ’ BFIxS HZ Ухх Г OASI ( 2514) 2 2 j 3511
ADIDI тх BCIHS ' BCY?0 BE 194 Scri Oaxs | Т 05170 NAUK "EM NIU
ADIA? BC I0 I ВСУ71 1 BF 19s BZ Y9i N OAM) ; ZSVK 2N706 А уз?
ADZi 1: BC137 ү ээ BCY7? BF 196 r QAI 75272 n мл Е 2 EST
ADZ12 ВС147 > f sezi s Brio? Ол»5 ZSY8 $97 | 2м 2N3703 36392
AVION BCl4s „л? f BDNS s [ вкл» TT 2 5 ЕЗ эку! 25 N3704 | NOS
АЕ У ВС149 ' BDNI 2. ВЕ: ОА? 5 s 54 ZIX 0 INIA р 2м375 Em
ALVIS BCIS7 ) BDI24 BFNI "ric OAT 5 ZINI 241132 мм 28745A
AVII BCI5N ' BDI [Eh BF Оди) x хмм 3 INIM 2N3707 $746 А
AF117 n BCISY 17 BDI 3 [ sr i OA ZI РАКЕТ JNIWA 0 2N370x | е
AF 139 вет ] BD135 ВЕ? QAZ?n хм? 2N мы мую
АНА 5 BCI70 BD136 BF?s9 "Ri Олий ) РААТ 2
А 29 BCI7I ‚ BD137 BF Ў ОСІБ РАТ
АРАП BCI7? р Вризх BE337 Ex OC» ^ ZINA
AFZI? | [| вст BDI í RF3AX f 5 h oc? В имВ КАКЫ
ASY 6 ВС177 ВО130 BFS21 G ocn RINY ГАРЕТ
ASYM BCI7S ВО! BFS?x СМИЗ?КА OCH ков Га
ASZI5 BC179 BDIN! BFS) KS 1A E
ойо
GUSI
GXUI
GXU?
GXU3
GXU14
GxUso
СҮ!
GZ32
GZ33
6214
6237
ктө!
KT66 Я
KT7? Gold
et
12AY7A
12B4A
12BA6
12BE6
12BH7
12BY7
NEITT
12E 14
12E1
ЕЕ
- х0
AIRM
А2067
*
әй»
z
55020225555
NNNVUN—ONNw&
32585523555:
м
=
ЕО. wwe
skesssgens
v--an
БЕРЕ
ET
=
=
E:
T
8
8
Tinta ee ta лч
БЕ:
ЕРЕ
8855885
RR3-250
RR3-1250 45.75
S130 6.00
S130P 6.00
STV280-40 14.00
STV2NO-8O 21.00
$041 5.00
5042 10.00
Т003-10 35.00
TDO3-10F 35.00
50.00
37.50
37.50
60.00
--
BRN Zwan ЗЕ
ыы
8
&
M
>
FEEFEE
.25
50
50
00
00
50
so
so
so
25
sO
75
so
Лә Бур шшк Жл T о в в в этә; р
BS BARASSERSRSSSRBSESSSASSUSSESB
ВЕРЕ
Be HN мм-ә?
ЕРЕ ИРЕР REI i
Чч!
8388382:
-LERBPEELFERIYPTELEERI
EE
E
СЕНО
258
З= 773719
E
——5
saa
ж
SSS
— —— NN SERI TNT
S22
ЮК —ызк———©@
х
рч
ИИА
= S
= $855
Du ls оошо
—
M
Éxos3ES----2&5
681118 6K
©
£22
UICE SOIT I EI EIS RT TES
EBSSUEEJES UJSBSSESEUEBSEROSÉOSERBUBSEZEDSBUBABU
m
a
-
-e
Reesesazssascs
6SA7
5
5
KSS
SsEEDESSÉEERÉE
Ppa
Raa
лю о а мото N ооз БС оо юкә
жа
25
>
2
5
8853
moo
Ж—— киэ
25528
82322
SSH an eheSb
БЕРБЕР
мы М NO ҺӘ МӘ — А Д d FA —
esas
Bare
РЕ
R
$5825
Вы ---нмо-аамлыьы кә әкә
л
©
аро acum
Ree
яз
оо
ООУОЗ. 10 26.25
OQ V03-20A
48.38
ООУ 40A "
46
QOV-
7665
002706-40А
62.20
0037 12.50
QVvori2 6.80
"
Ei
2585655112565 57508558833
s
Dew NNR = ON NN нь В молю SEN
—
NETS
PEE
es
E Баа
8355583555555
5
Large stocks
Prices on
application
РЕ:
BSS choesessess Beusch seesschh sce sehashsase see ssgngezzss
we®Bss
2
TINA eA eRe
О ф de кә EN WEN КӘ e Lad чә ш ш шә шә КӘ!
PETI
888
ә
a
5
Ер
I AAS7U
i 2 74170 I AAGMIS
BIG Unskirted M + [ T ч 7.ци 7 7. m ? 74172 4 ГАА
/ ө! 15 7 N р 74173 д ВАЗ
B7G Skirted à SU'P7 MILI pl 743 ^ S \ E 7 (he 74174 ВАК)
П 5 6422 7193 \ 5 4 г; 5! 74175 | ВАЗ М!
BUA shirt 5х 07 ч I i 3 " ‚7 эх HSS 7417 IBASSUQ
BUA Unskirte : 4 65 74 159 4 I ВАЗ
VPE Lan А : Ы е м UT › 1ЗАб7А
А Skiried р 7-3 a ' i
BYA Shirte | . ‘ ! : e ^ к и y nul ; ВАЗИ
$5 p 7 7 2 А | 74192 ВАЛИК)
Rees ч Au "t 7 " M К 71193 р IHATSID
Lindl 655 VENT, | : 2 1: 1и s : 74191 | I BASNDO
pe T м Ы / f 4195 ГАУ
Nuvistet base 5 VORIWA 5 7 E 7 ‹ 747 S | \ MS TS S
^ud Ni \ R517B8. 100 1 i \ 76 ‚ 5 74197 1 ICAO
Valve screening VORSITC Mod v x [ \ 1155 74198 м IC АТА
сап adf sizes 0 i `Р! ТЕ 1 М JN ГР & 711 74199
Terms of business; CWO. Postage and packing valves and semiconductors £1.00 per order. CRTs £1.50. Prices excluding VAT. add 15% Telephone: 01-677 2424/7
Price ruling at (ime of despatch s
In same cases prices of Mullard and USA valves will be higher than those advertised. Prices correct when going to press Telex: 946708
Account facilities available to approved companics with minimum order charge £10. Carriage sed үүнү | £1. on credit orders Е. & О.Е.
Over 10,000 types of valves. tubes and semiconductors in stock. Quotations for any types nol listed. S.A .! Open to callers Monday-Friday 9 a.m. – 5 p.m.
ENTER 34 ON REPLY CARD
436 ELECTRONICS & WIRELESS WORLD
HP portable
Also from Livingston Technical
Sales, comes the The Hewlett
Packard 8590A RF Spectrum
Analyser, offering features previously
found only in high-performance
models, but it comes ina
lightweight, sturdy package
weighing only 13.5kg. It is equally
suitable for hench applications, in
r.&d, manufacturing environments
and for field use; for stand-alone or
systems applications, It has the
versatility to handle virtually any г. f.
signal measurement requirement.
The instrument covers the 10kHz
to 1.5GHz frequency range (1.8GHz
optional), with — 115 to +30dBm
amplitude range. Designed for easy
manual operation, the 8590A is the
first HP spectrum analyser to have
both dedicated pushbuttons, for
frequently-used functions, and
menu-based softkeys, with access to
more than 80 additional functions.
Most measurements require only
frequency, span and amplitude
selection, the analyser automatically
adjusting remaining parameters for
an optimized c.r.t. display. Optional
HPIB, HPIL RS232c interfaces
enable fully programmable, and
direct output of results to printer or
plotter.
More than 100 built-in functions
aid measurement and data handling,
including signal track and marker
functions, automatic performance of
complex measurements, trace
arithmetic and trace storage.
Coupled with the HP 8444A
tracking generator, the HP8590A
performs evaluations such as
stimulus response measurements,
e.g. frequency response and
insertion loss. Further addition of
the HP 10855A broadband amplifier
and the new HP 11940A close-field
probe yields a swept, broadband
sysem for e.m.i. troubleshooting.
The unit is availahle for sale ex
stock from Livingston Technical
Sales or on short term rental from
sister company, Livingston Hire. at
£200 a week.
EW PRODUCTS
SPECTRUM ANALYSERS
| Portable analyser for
satellite reception
Especially designed to cope with
tv.r.o. installation and service
problems, the Avcom PSA-35 is a
| lightweight portable instrument,
which operates from a.c. mains or
internal rechargeable batteries. The
frequency coverage is from under 10
to over 1500МН2 and from 3.7 to
4.2GHz in 6 bands (including the
current 12GHz for 1.n.bs. The
instrument has a built in power
block and power for 1 .n.as and b.d.cs.
It will accurately measure wide band
signals commonly used in thetv.r.o.
industry, and is ideal for accurate and
rapid testing and alignment ot
satellite equipment.
Optional extras include a signal
| sampler, aterrestrial interference
survey horn anda carry case. For
further details contact Fieldtech
Heathrow Limited, Huntavia House,
420 Bath Road, Longford, Middlesex,
UB7 OLL. Tel: 01-897 6446.
анны
Synthesized
spectrum analyser
Up to3.6GHz from 10khz with an
input sensitivity of —1314Вга anda
minimum resolution bandwidth of
30Hz are provided on the TR4135
synthesised spectrum analyser from
Advantest.
The increased use of the upper
u.h.f. banda tighter control of
frequency harmonics have created a
demand for measurements to be
made up to and beyond 3GHz. This
analyser costs less than £16,000
| Anin-built frequency counter with
1Hz resolution is included, together
with adjustable marker display of
frequency and level. Log. frequency
displays are possible with a direct
hard-copy capability. Facilities are
provided for field-strength and
CISPR interference measurements
for ATE applications. GPIB controls
are available with an optionat
tracking generator to 3.5GHz.
Advantest products are available
from Chase Electronics Ltd, St.
Leonards House, St Leonards Road,
Mortlake, London, SW14 7LY.
Tel: 01-787 7748.
1GHz analyser from
Farnell
From Farnell comes the 352C
portable spectrum analyser,
designed for ease ofuse in
monitoring spurious radiations in
teh range 300kHz to 1GHz. Five
sweep ranges have three
measurement bandwidths from
2MHz on the widest range to 9kHz on
the narrowest, (3MHz) range. The
instrument may be used as a fixed
tuned receiver over the full
frequency range and both a.m. and
f.m. demodulation is provided with
an internal loadspeaker for output.
The display has long persistence
green phosphor with 488 lines on a
C.r.t. screen. All control functions,
including error reduction and
system monitoring are
microprocessor controlled. Up to six
front-panel settings can be sored and
controlled. The internal picture store
can be output to a printer for hard
copy. Farnell Instruments Ltd,
Sandback Way, Wetherhy, W.Yorks
1.522 4DH. Tel: 0937 61961.
ELD ELE оон леч LAT OE TE LE IEG OE TE EE M
Portable Tek analyser
Tektronix has introduced a new
generation v.h.f /u.h.f. spectrum
analyser priced at around £7 500; the
10kHz to 1.8GHz TEK 2710. The
instrument provides a 5MHz i.f.
bandwidth filter, 10 ? frequency
accuracy. four-trace digital storage,
full marker/delta marker control, a
comprehensive time domain
measurement capability; and many
"built-ins" not available on current
lower cost spectrum analyzers.
The standard TEK 2710 has
resolution bandwidths down to
3kHz; there is an option for 300Hz
resolution. Frequency accuracy is
10° or + 10kHz at 1GHz centre
frequency on the standard 2710. with
an option for accuracy of5 x 10^ or
+500Hz at 1 GHz centre frequency.
An optional built-in frequency
counter provides readout resolution
to the nearest hertz and rapid
frequency measurement when in
wide spans; any signal 10dB above
displayed noise will be counted.
When the counter is used in zero
span (time domain), it will measure
the frequency content of the
demodulated signal e.g. modulation
frequency.
On-screen dynamic range is 80dB
and vertical scaling is selected from
10, 5 and IdB/div with reference level
units of dBm. dBmV., dBV. dB/p.v
dBu W. and dBu V/m available. The
ТЕК 2710 accommodates both 500/
dBm and 7592/dBmvV operation.
Sensitivity is —117dBm at 3kHz
resolution. A built-in preamp may be
switched into the conversion chain
which will boost sensitivity to
129dBm. An additional 10 dB of
sensitivity is available if the 30011z
resolution option is included. The
comprehensive time domain
capability of the instrument makes it
of particular value in making
communications measurements.
Included are lps (02 sec/div sweep in
а 1-2-5 sequence for maximum
flexibility in expanding the display.
Analogue display for gray-scale
enhancement and 5MHz system
bandwidth (including c.r.t.) that
minimizes amplitude measurement
ELECTRONICS & WIRELESS WORLD
distortion. A.m./f.m. detectors with
audio amplifier, built-in speaker and
headphone jack permit listening to
demodulated audio. A new, optional
video monitor mode permits viewing
the demodulated, rasterized video on
the c.r.t. ofthe TEK2710.
The instrument includes marker/
delta markers with tront panel
control for peak find, next right and
next left manoeuvres. Other marker-
related functions are available via a
frequency/marker menu. Markers
function in both the time and
frequency domain and include off-
Screen measurement capability.
Digital storage display includes a
four-trace capability. A.B and C
displays may be stored and viewed,
with the D display always remaining
current. This resul's in
enhancement of signal comparison.
Acquisition of the analogue signal
may be on the basis of positive/
negative peak processing where
signals “buried in the noise” may be
discerned: or positive-peak-only
processing that provides best
horizontal-scale display resolution.
Ensemble signal averaging may he
selected between тіп. max, mean ог
min/max values. Ease of use is
enhanced by logically grouped:
dedicated front panel controls for
primary functions. The TEK 2710
includes comprehensive secondary
control capabilities that are accessed
viaa set of five clearly marked menu
keys. А user-de finable key provides
single keystroke measurements that
are programmed and executed from
the front panel. Operation is further
simplified by an auto calibre routine,
and automatic resolution, sweep and
r.f. attenuation modes which
eliminate operator traps and keep the
analyser in a calibrated state.
Additional options available
include Centronics interface, battery
operation and rackmount
configuration, GPIB and RS232
interface and a tracking generator
will be available at a later date.
Tektronix U.K. Ltd.; Fourth Avenue,
Globe Park, Marlow, Bucks. SL7
1УБ. Tel: 06284 6000.
437
The Archer 780 SBC
The SDS ARCHER - The 280 based single board
computer chosen by professionals and OEM users.
* Top quality board with 4 parallel and 2 serial ports,
counter-timers, power-fail interrupt, watchdog timer,
EPROM & battery backed RAM.
* OPTIONS: on board power supply, smart case,
ROMable BASIC, Debug Monitor, wide range of I/O &
memory extension cards.
from £185 + VAT.
ENTER 32 ON REPLY CARD
The Bowman 68000 &BC
The SDS BOWMAN - The 68000 based single board
computer for advanced high speed applications.
* Extended double Eurocard with 2 parallel & 2 serial
ports, battery backed CMOS RAM, EPROM, 2 counter-
timers, watchdog timer, powerfail interrupt, & an
optional zero wait state half megabyte D-RAM.
* Extended width versions with on board power supply
and case.
from £295 + VAT.
ENTER 33 ON REPLY CARD
Sherwood Data Systems Ltd
Sherwood House, The Avenue, Farnham Common, Slough SL2 3JX. Tel. 02814-5067
HART — The Firm for QUALITY
LINSLEY-HOOD 300 SERIES AMPLIFIER KITS
Superb integrated MosFet amplifier kits with an unbeatable pedigree
Circuit design by John Linsley-Hood and engineering by HART
Ultra easy assembly and set-up with sound quality to please the most 3 = @ к
discerning listener. Ideal basis for any domestic sound systems if Car
quality matters to you, Buy the complete kit and save pounds off the
individual component price
IN VIEW OF THE EXTREMELY RAPID CHANGE TAKING
PLACE IN THE ELECTRONICS INDUSTRY, LARGE
QUANTITIES OF COMPONENTS BECOME REDUNDANT.
WE ARE CASH PURCHASERS OF SUCH MATERIALS AND
K300-35, 35 Watt, Discount price for Comptete Kit £98.79
K300-45, 45 Watt. Discount for Complete Kit £102.36
RLHA4&S. Reprints of Original Articles from HiFi News £1.05 по VAT WOULD APPRECIATE A TELEPHONE CALL OR A LIST IF
LINSLEY-HOOD SYNCHRODYNE AM RECEIVER
Very high quality kit for this recent design featured in ‘Wireless World’. Advanced construction
system, approved by the Author, uses 3 double sided PCBs in a stacked layout for total stability, ease
of construction and minimal wiring. This module will form the AM section of an ultra high quality
AM/FM switched bandwidth tuner to match our 300 series amplifiers. Power supply and tuning gang
will be included with the FM section
K450 JLH Synchrodyne Kit Special Price £59.95
LINSLE Y-HOOD SUPER QUALITY FM TUNER
The long awaited ultra high quality FM companion to the Synchrodyne AM receiver. Novel circuit
leatures ready built pre-allgned front end, phase locked loop demodulator and advanced sample and
hold stereo decoder. Clrcults featured in ‘Electronics Today International magazine February and
March 1987. Complete kits for FM only or combined with the Synchrodyne are cased to match our 300
Series amplifiers, Send for details.
AVAILABLE. WE PAY TOP PRICES AND COLLECT.
R. Henson Ltd.
21 Lodge Lane, N. Finchley, London, N12 8JG.
5 mins. from Tally Ho Corner
Telephone: 01-445 2713/0749
HIGH QUALITY REPLACEMENT CASSETTE HEADS
Do your tapes lack treble! A worn head could be the problem Tape
heads are constantly Improving and fitting one of our latest
replacement heads could restore performance 1o better than new! 4 ]
Standard mountings fit most decks and our TC1 Test Cassette will Dx А
таке it easy to set the azimuth spot оп. As we are the actual =
importers you get prime pars at lowest prices, Ali our heads are
suitable for Dolby machines
HC20 Permalloy Stereo Head. Good quality standard head fited as Ofiginal equipment on many
decks £7.66
HSt6 Sendust Alloy Super Head. Quite simply the best Longer life than permalloy higher output than
ferrite, fantastic frequency response £14.86
ENTER 18 ON REPLY CARD
TARGET ELECTRONICS
16 Cherry Lane, Bristol BS1 3NG. Telephone: 0272 421196
Telex No: 946240 CWEASY С. Quoting: 19013485. Easylink No: 19013485
==
—
S
HQ551 4-Track head for auto-reverse or quadrophonic use. Full specification record and play head £14.60 AL EN: y
Special Olfer Stereo R/P Heads £2.49 ==:
4-Track Auto-Reverse Play Head £3.50 Subminiature D type pluc £1.55
HS9510 2/4 Stereo DC Erase Head £6.70 соппес tore Gold plated а ыз
HQ751E 4/4 Erase compatible with HQ551 £39.70 contacts Solder bucket ©
Full data on these and other heads in our range are contained in our free list
terminals RS232 WALL PLATES LB.MJPC
HART TRIPLE-PURPOSE TEST CASSETTE TC1 one: ба With 25 pin 'D' sockets DOE d oss
One Inexpensive test cassette enables you to set up VU (Dolby) level, head azimuth and Sav trials hao 2 Amstrad
tape speed without test equipment. Vital when fitting new heads. Complete with instructions £4.66 ет ái 4 T 6128/464 — 12M 795 695
JLH QUALITY AM RADIO 9-way hood 34р 25р Солк. Эй Su eura
Sets of Parts available now. including Short Wave coils. Рий kits ready later. Send for tist 15-way male 44р 33р болой
зума дар Centronics 1.8M -550 495
Send for your FREE copy of our lists with full details of our complete range of Kits, Components. 15-way hood 38p 28p
PCBs. Cassette Heads and Decks: ~ Overseas please send 5 IRCs for Аитай Post 25-way male 60p 48p 3
25-way female 65р 95р
Please add VAT to all prices. Postage on orders ир to £10 - 50р. £10 to £49 — £1. Over £50 — £1.50.
25-way hood 42p 32p
= Aii pices exclude post packing and VAT
— catalogue availathe
| ELECTRONIC KITS LTD
1, Penylan Mill, Oswestry, Shropshire SY10 9AF
24 hr SALES LINE (0691) 652894 Please add VAT
ENTER 8 ON REPLY CARD
438 ELECTRONICS & WIRELESS WORLD
— m SPECTRUM ANALYSERS
Analyser for test and education
Part of the Lab-Volt analogue
communications training system is
the 9405 Spectrum analyser. It has
been designed for the study of audio
and r.f. signals in the frequency
domain. Combined with an
oscilloscope, the power levels of the
frequency components of an input
signal can be displayed on the
oscilloscope screen.
The analyser can display frequency
components from 0 to 30MHz, or
from 85 to 115MHz, with the centre
frequency being displayed опа
digital readout. The input signal level
is from —70 to +30dBm. The output
spectrum can be directed tothe
oscilloscope or a recorder/plotter.
The input impedance is switch-
selectable between 50 and 1М and
inputs can be attenuated in five steps
from 0 to 40dB. The bandwidth
resolution is set automatically to the
optimum for the range selected,
SA каз аай |
between 100 and 50kHz.
The analyser incorporates a digital |
memory for the oscilloscope display
witha refresh rate of 30Hz.
Frequency scan is selectable between
2khz and 1MHz/volt. With the
oscilloscope set to 1V/div, a total span
of 20khz to 10МН2 сап be displayed. |
А ‘по scan’ position can also be
selected. Lab-Volt UK, Unit 6,
Cromwell Mews, St. Ives, Cambs
PE17 4BH. Tel: 0480 300695.
Analysis of power-line spectra
Anew disturbance waveform
analyser from Dranetz is claimed to
be the first of its kind to feature
screen-based operation. The touch-
sensitive screen displays self-
explanatory menus for easy
operation, and full disturbance
waveform detail derived from high-
speed sampling detectors.
The Series 656 not only monitors
power line disturbances on four
channels but also offers the option of
an eight-channel environment
analyser enabling monitoring of
temperature, humidity, r.f.i. etc. By
capturing, displaying, analysing and
storing vital information, the
instrument helps to eliminate the
hazards that threaten reliable
operation of sensitive electronic
equipment.
Setup and report parameters are
simply programmed using the screen
or keyboard, and an RS232c interface
is provided for remote operation. The
disturbance waveform is stored in
non-volatile memory for analysis and
display, mass storage being provided
toallowan extended period of
disturbance monitoring.
Disturbances are analysed on-screen,
stored опа disc, or printed out using
the integral thermal printer. А zoom
facility enables areas of the
disturbance waveform, selected on
the touch-sensitive screen, to be
ELECTRONICS & WIRELESS WORLD
expanded for further analysis. The
656 can also be programmed to select
disturbances with user-defined
characteristics for investigation.
Software support includes а
variety of standard report formats for
the generation of records, including
easily-interpreted summaries and
relevant disturbance waveforms, to
help production of site histories.
The eight-channel ervironmental
input board accepts 0 to 10V or 4 to
20mA inputs from external probes
and transducers.
Livingston Technical Sales
Limited, 2-6 Queens Road,
Teddington, Middx TW11 OLR.
Tel: 01-977 0055.
EW PRODUCTS
Analyser and DSO
combined
! Having the functions of both a
spectrum analyser and a digital
storage oscilloscope, the
| Scopadaptor 9060 is used with a
‘host’ two-channel oscilloscope. The
instrument is a two-channel digital
signal processing unit with input
attenuators-amplifiers, anti-aliasing
filters and a-to-d converters. It
provides analogue outputs to the
oscilloscope together witha trigger.
In the FFT mode it acts as a
spectrum analyser with a bandwidth
of 40kHz. The high-speed monolithic
d.s.p. allows updating the display, at
the slowest frequency, every four
seconds and at high frequencies,
every second. Averaging in binary
steps from 1 to 128 is provided,
which is useful when testing
equipment using white noise. Other
features include the ability to
| compare, or subtract the signals.
The instrument will also convert
an oscilloscope into a digital storage
device. The Scopadaptor has 512-
bytes/channel. Memory is read
continuously by the screen refresh
circuitry at the sweep rate of the
oscilloscope.
Both functions can be combined in
one display for a single signal. This
| can be used fora continuous signal
but is particularly useful for single-
shot capture and analysis. Data
Acquisition Ltd, Electron House,
Higher Hillgate, Stockport, Cheshire
SK1 3QD. Tel: 061 477 3888.
Analyzer in software
Structured Software's Spectrum
Analyser ll runs on the ВВС
microcomputer and provides
facilities previously found only on
expensive dedicated hardware.
Typically, a waveform is displayed,
windowed if necessary, and its
spectrum computed and displayed in
approximately 15 seconds using FFT.
Digital readout of waveform and
calibrated spectrum are available
under cursor control.
For transfer function and
transmission loss measurements,
input and output waveforms are
considered together: both the
amplitude ratio (in dB) and the
relative phase can be displayed.
The analyser software is disc-
based, and is easily adapted to
process files in any format generated
by the user. As supplied, it is directly
compatible with the Data Harvest
VELA data recording system: the
combination provides a complete
analyser working from analogue
input signals.
The price of the Spectrum Analyser 11
software is £200. Further details
from Structured Software, 15
Athelstan Close, Bromborough,
Wirral, Merseyside. L62 2EX.
Tel: 051 334 3290.
439
Hitachi Oscilloscopes leading the way оп £299
in performance and pricing! +VAT
The highest quality
The Hitachi nam2 is synonymous with quality and reliability and
- і is backed Буа 2 угаг or 3 year warranty оп every oscilloscope.
eee CE | Е m : | The keenest pricing
| a | With prices start ng at only £299 for a 20MHz dual-trace model
IRPEF rae г. 1 ® ean № “ Hitachi's price-performance ratio can not be bettered
= - 3M B m The largest range
Now totalling 18 models the Hitachi range covers bandwidths
from 20M Hz to 150M Hz and digital storage models to 60M Hz.
The fastest service
We сап supply ary Hitachi 'scope immediately from stock and we
back it with full calibration and after-sales service.
x For colour brochu-e giving specifications and prices ring (0480) 63570
рае Thurlby Electron cs Lid., New Road, St. Ives, Cambs. PE17 4BG
ENTER 58 ON REPLY CARD
Thurlby 1905а £349.v4
A complete high performance bench DMM
g h E | € 5% digits; 0.015% асс; 1uV, IMQ , 1nA.
не с 0 g 9 = єз зз i ® Full ac and current functions as standard
A sophisticated computing and logging DMM
€ Linear scaling with offset; null/relative
€ Percentage deviation; running average
€ dBV, dBm general logarithmic calculations
€ Limits comparison; min and max storage
€ 100 reading timed data logging
€ RS232 and IEEE-488 interface options
Thuriby Electrcnics Ltd ГЈ [22]
New ces St.lves, Cambs. PE17 486 [| Thurlby ER
Tel: (0480) 63570 designed and built in Britain
ENTER 59 ON REPLY CARD
ROTEGH 3132...
THE WISE DECISION
рап You Afford Less?
The 3132 salves three requirements at
one go. 1) 20MHz; 2 mV/div Dual Trace
Scope. 2) Triple DC, P.S.U. + 5V; + 12V
(Floating common). 3) Component
Comparator, for comparing active and
passive components.
= € —
a — HÀ
ac.
ete
All for the price of a Scope.
rpm o
LÀ
dj s > T £285 Exc. ута Delivery
=. = Why pay a little less, for a lot less?
| | у
Crotech instruments Limited САМ YOU REALLY COPE WITHOUT OUR SCOPE"
2 Stephenson Road, St. Ives, Huntingdon, Cambs. РЕ17 4WJ Just phone or write for your free copy of our
Фя Те!ерһопе: (0480) 301818 catalogue.
ENTER 73 ON REPLY CARD
440 ELECTRONICS & WIRELESS WORLD
Image acquisition system
G.J. AWCOCK, F.W. STONE AND R. THOMAS
A low-cost solid-state sensor, coupled with suitable image-
processing software, is more than adequate for many
applications in robotics, security and character recognition.
selected as the basis of an image process-
ing system for no better reason than its
familiarity, or ease of display on standard
monitors. However, the quantity of data re-
quired to represent a high-resolution image
is a major factor contributing to the inacces-
sibility of computer vision; and so it is essen-
tial that very careful consideration of the the
system requirements should result in a
sensor specification which is adequate, and
no more.
A conventional tv camera produces an
analogue video signal which is continuous in
the horizontal axis but discrete in the vertic-
al axis, by virtue of the raster scan method of
picture reconstruction. The maximum re-
solution in the vertical axis is approximately
574 lines, with interlace, and because the
horizontal:vertical aspect ratio of a standard
tv screen is 4:3 this implies a horizontal
resolution of approximately 765 picture ele-
ments (pels, or pixels). Thus the number of
pels required to represent a full-resolution
picture is 574 x 765 = 439 110.
If, in addition, each pel is represented as
one of 64 grey levels. і.е. a grey-scale
resolution of six bits, the quantity of data
which must be acquired for each picture will
be a grarid total of 2 634 660 bits for a mono-
chrome signal! Thus the scale of the problem
of acquiring images and storing them in a
personal computer becomes obvious.
In addition, a new picture is generated
every 40ms, leading to a throughput re-
quirement which makes real-time camera/
computer interfaces both complex and cost-
ly. This problem has been tackled to some
extent for static or slowly changing images
by the development of slower multi-frame tv
intertaces, which build up their images over
a number of consecutive frames. This eli-
minates the problem of video-rate a-to-d
conversion and considerably reduces the
cost of an interface. but it does nothing to
I many cases the broadcast tv format is
ELECTRONICS & WIRELESS WORLD
PC
= е з 115 22
app toss a PUR
Fig.1 (above). Raw image acquired by the
1S32 sensor: the picture shows light falling
on another 1532.
Fig.2. Micron Technology's 1532 optic d-
ram: a 64K memory device with a transpa-
rent lid. Price is about £40.
>
Se
ease the problem of storing this quantity of
data within the computer.
Solid-state image sensors should otter
hope of a simpler interface, since the data is
inherently discrete in both the horizontal
and vertical axes. Generating distortion-free
raster scan video is then a relatively simple
problem for digital electronics.
Unfortunately, the best known of solid-
state sensors, the charge-coupled device
(c.c.d.), does not have many advantages over
conventional vacuum tube cameras in low-
cost applications.
In general, c.c.ds have been designed with
the full tv standard specification in mind,
offering spatia! resolution of typically
380x488 pels with continuous grey-scale
dynamic range of typically 1000:1. Thus they
da very little to ease the problem of excessive
image data; and a sensor free of blemished
photosites (i.e. light-sensitive cells that are
defective in some way) costs considerably
more than а complete normal tv camera.
There is, however, a relatively new solid-
state image sensor which is ideally suited to
experiments with computer vision. The de-
vice is the 1532 optic d-ram (Fig.2) from
Micron Technology, which is based upon а
64K dynamic ram and thus offers 65 536
pels, each having a one-bit grey-scale. The
pels are organized into two banks of
128x256, separated by a thin dead-zone,
which effectively makes one of the banks
redundant for use with normal optical sys-
tems. Hence the working resolution of the
device is 128x256, making it well suited to
the high-resolution screen modes of many
popular computers. The one-bit grey-scale
maps well on to the limited range of colours
usually offered in such modes.
The hardware interface to be described
here uses only half of one bank of pels (a
128x 128 "quadrant ), because the elongated
shape of each pel (13.6х8.8 microns) makes
this resolution match the aspect ratio of the
441
Fig.3. The raw image (top) can be en-
hanced by software (middle) and proces-
sed further (bottom) into a form suitable
for character recognition purposes.
computer monitor screen most accurately.
Image data from a quadrant may conve-
niently be stored in 16K-bits (or 2K-bytes).
The binary grey-scale of the system may at
first seem a limitation, but it should be
remembered that many image processing
Schemes 'threshold' their grey-scale data at
an early stage to produce binary images for
their descriptor extraction algorithms to
work on.
However, this system should not be
thought of merely as an educational toy,
since many applications such as robotics,
security and character recognition (Fig.3.)
etc., are perfectly well served by binary
images. Indeed, with the careful use of
lighting to emphasize the features in the
Scene, some industrial inspection tasks
could be undertaken by systems making use
of this sensor. In addition, the small physical
size of the 1532 opens up some unique and
exciting applications: for example. in the
field of robot vision, with the sensor
mounted in the end-effector of a robot arm,
the so-called eye-in-hand mode of opera-
Поп“.
_OPERATION OF THE OPTIC D-RAM
A 64K d-ram consists of 65 536 memory
cells, which, for reasons of economy of
silicon and efficient access, must be orga-
nized as a matrix; or, as in the case of the
1532, two matrices, each of 128 rows by 256
columns (Fig. 4). Thus when row and col-
umn addresses are supplied to a d-ram
matrix the row address is responsible. in-
itially, for selecting the bank of cells to be
accessed and, ultimately, for selecting which
of the rows of cells is connected to the set of
column data input/output lines. Each of
these lines is terminated by a bidirectional
*Pugh, А.. Second generation robotics and robot vision:
Robotic Technology pp. 1-9. Peter Peregrinus Ltd on
behalf of the IEE, 1983.
442
sense amplifier; and the column address
must meanwhile select which of these sense
amplifiers is connected to the data in and/or
data out buffers during read and write cycles.
Each photosite in the 1532 is one d-ram
cell. consisting of a small capacitor con-
nected toa fet analogue switch, which allows
the row-selection of its associated capacitor
as the target for write or read operations.
When row-selected, all the cells in this row
will be connected to their column data
in/out lines, but only one sense amplifier will
be activated and connected to the outside
world. Then the process of writing to the
target cell involves storing a voltage on its
capacitor, whilst reading it involves conduc-
tion of the charge stored there to the
selected sense amplifier for regeneration.
In isolation, regeneration would not be a
difficult task, but since the cells are con-
nected in a matrix the output of each
selected cell switch is connected to a column
data in/out line along with 127 other cell
switches in their off-state. This results in a
considerable capacitive loading upon the
data line, of the order of 20 times the cell
storage capacitance. Thus, when a cell capa-
citor is connected to the data line, the charge
it stores must be re-distributed between
itself and the line capacitance now con-
nected in parallel, this results in an attenua-
tion of the voltage used to represent the data
by a factor of approximately 21. The speci-
fication of the 1532 states that in the normal.
memory, mode of operation a voltage grea-
ter than 2.1V on the cell capacitor will be
interpreted as a logic 1 ; and assuming an
attenuation factor of 21, this implies a
threshold for the sense amplifier of 100mV'
There is a further task, related to re-
generation, to be dealt with by the d-ram's
internal circuitry: that of refresh, if the
capacitor in the cell were totally loss-free
there would be no need for refresh, since any
voltage stored on the capacitor would re-
main constant for ever. However. capacitor
leakage is inevitable, and it is necessary to
provide a mechanism that can read the
contents of each cell and, upon re-
generation to the required logic level, write
it back into the appropriate capacitor. This is
ajob that the sense amplifiers are well able to
perform, and indeed their design ensures
that refresh takes place automatically when
any cell is read. Alternatively the user may
initiate a refresh-only cycle which performs
the same function but without enabling the
data output buffer.
It is left to the user to ensure that the
refresh operation takes place sufficiently
often to avoid loss of data in normal memory
applications. To reduce the problem of time
overhead due to refresh, a read or refresh
Cycle to any address in а row will cause
Fig.4. Block diagram of 64K d-ram, showing basic memory cell configuration.
Row
address
buffers
(
RAS
TAS Timing and control
м
Row Half memory array
decode
Column decode
256 Sense! Refresh amplifiers
Column decode
Half memory array
Read/ write select
transistor
Row select
Storage
1 capacitor
Data OUT
register
To 127
other cells
To 255
other cells
Column data
IN/OUT line
ELECTRONICS & WIRELESS WORLD
refresh of that whole row to take place. т
addition to accessing the particular cell as
desired. This thoughtful aid to normal d-ram
applications proves to be rather less than
helpful when the device is used as an optical
sensor, as we shall see later.
Loss of charge on the cell capacitor is a
nuisance with regard to data storage, but is
tolerated because of the significant space
and power savings that d-rams offer over
other, static, memory cells. However, а
relatively recent development has allowed
this same mechanism to be exploited as a
light sensor, since it can be shown that when
these capacitors are subjected to light ener-
£y. the rate of discharge becomes pro-
portional to the intensity of the incident
light, as well as time elapsed since re-
generation. Light sensitivity is well known
in other applications of silicon and is due to
the generation of an electron when a photon
is absorbed in the bulk of the material.
In the case of d-ram cells, the plates of the
capacitors are fabricated in silicon and the
electrons which result from photon absorp-
tion serve to reduce the charge stored there.
Thus the decay of capacitor voltage with
time exhibits a characteristic such as that
shown in Fig.5; it is clear from this that the
time taken to decay below the logic 1 /logic 0
threshold is now dependent upon the level of
incident illumination.
Conversely, a fixed time delay between
initialization (or re-generation) of the cell
and its subsequent interrogation will effec-
tively set a threshold level of illumination. If
the incident light is above this threshold
then the cell voltage will be interpreted as a
logic 0; if below, the sense amplifier will
read, and re-generatea logic 1.
The net result is two-state, or binary.
detection of illumination, provided that no
refresh operation has been performed in the
interim. Extreme care should be taken to
avoid reading or refreshing any cells in the
same row of the matrix as those undergoing
exposure, and careful thought must be given
to the initialize-expose-interrogate cycle to
be employed.
It is also necessary to be aware of some
peculiarities of the 1532, which stem from its
having been designed primarily as memory
device. rather than as an image sensor.
Firstly, the two banks of cells store their data
differently, so that the least significant. or
upper bank (rows 0 to 127), must be initial-
Vss CAS Dout Ae Аз А, А5 А]
Quadrant 1
UPPER ARRAY
LOWER ARRAY
Хз Spatial grid coordinates ХО
=
Analogue Din Write Ld А М А) Мс
threshold
Fig.7. Layout of the IS32 device. A dead-
zone between the upper and lower arrays
makes half the device unusable in most
optical systems. Only one quadrant is used
in this design; it gives a working resolution
of 128 x 128 picture elements.
ELECTRONICS & WIRELESS WORLD
STORAGE CELL VOLTAGE
Fully charged level
Threshold voltage
Low
Average Light level
Fig.5. Characteristics of storage cells in the 1532 optic d-ram. Decay time of the capaci-
tor depends on the incident light level.
ROW address
Counter 1532
0; Ag (5)
Q6 Аз (12)
Qs Ay (6)
а, А2 (7)
аз A, (11)
02 А5 (10)
0, Ag (13)
Qo ) ——“»
|
COLUMN address
Counter ` 1532
Q7 ——— h IS)
Q6 — — Аз 02!
Q 5 —— r (61
44 ——————————————————— 42111
Q3 ————————————— — A, (1)
02 Ag (13)
Q1 о
Qo | +
Fig.6. The 1532 chip is designed primarily as a memory device, not as an image
sensor. To correct image distortions caused by the irregular layout of its photo-
sites, a two-stage linearization process is required. The first step consists of manipu-
lating the row and column addresses.
ized to logic 1, whilst the most significant.
lower bank (rows 128 to 255), must be
initialized to a logic 0. Thus, after exposure,
if the cell remains in the same state as that to
which it was initialized, then the pel must be
interpreted as dark (black); if it has changed
state, it must be treated as white.
If data from the 1532 is to produce a
Ee aa
C126
C127|C125
code pas id
C126
па шс
С127
№ R125
C126 | С124
EST АЕ
С126 с |]
Fig.7b. This close-up of Quadrant 1 illus-
trates local scrambling of addresses which
remains after the hardware address de-
scrambling of Fig.6. Software correction is
needed to eliminate it and so linearize the
resulting image. Blank cells represent
pcints having no light sensitivity, such as
the fet associated with each photosite.
R127
C125
443
meaningful picture. the screen pels must Бе
mapped with exactly the same spatial inter-
relationship as the photosites on the surface
of the chip. Unfortunately, this is nota trivial
task because the logical addresses of the cells
of the 1$32 do not correspond directly to
their physical positions: consecutive addres-
ses applied to the device will not necessarily
access adjoining cells on its surface. This
makes it necessary to apply a two-stage
linearization process, of which the first stage
consists of the application of the address
de-scramble logic recommended by the
185325 manufacturer (Fig.6).
The mapping that results is shown in
Fig.7(b). Notice that there is still an element
ot local scrambling and also that only half
the surface area of the chip is available for
photosites, the rest presumably being occu-
pied by the switching fet that each cell needs.
Thus, the second stage involves generating a
mapping scheme which has twice the resolu-
tion in the column axis to accommodate
‘space-pels’ which represent the inactive
areas of the chip surface, since these must be
included for a picture of the correct aspect
ralio.
Additionally, an algorithm must be ap-
plied to sort out the local scrambling evident
in Fig.7, and, furthermore, a slightly differ-
ent algorithm is required for each of the two
Serial
interface
Bit-rate
generator
Power -up
reset
444
Table 1: characteristics of IS32 quadrant
Number of active pels 16384
Layout 256 x 128 grid
Array dimensions 2210 876.8 microns
Pel dimensions 6.4 x 6.4 microns
Array aspect ratio 252-1
cell banks. In the picture which emerges
trom this process, 50% of the pels represent
active photosites in the 1532 and can take
either black or white states, whilst the
remainder are space-pels which may Бе
displayed in the user’s chosen background
colour. The use of an enlarged mapping
matrix with the inclusion of space-pels re-
sults in subjectively pleasing images with an
absence of the annoying ‘cogging’ at straight
black/white boundaries that would other-
wise be present.
If required, simple picture pre-processing
may be carried out to cause the ‘space-pels”
to agree with the majority of
their nearest neighbours.
This type of enhancement I——]
will he essential if the |]
image is to be used for ` A
further work such as \/
edge detection, and
has been applied in
Fig. 3 (middle). 1532 Optic
О-гат and support
Command
decoder
RAS/CAS
generator
Address descrambler
Clock
controller
Row t
counters
Variable delay
generator
Address multiplexers
In the next article, the authors introduce a
hardware interface for the 1532 which en-
ables it to be driven via a personal computer
over an RS-232 serial link.
Graeme Awcock is a lecturer at Brighton
Polytechnic and is reading part-time tor a
doctorate in computer vision techniques for
low-cost robotic systems. Previously he
worked as a senior design engineer at Com-
puting Devices. which he joined atter gra-
duating trom the polvtechnic in 1979.
Bill Stone designed the prototype imaging
system as his tinal-vear project at Brighton
Polvtechnic. Since graduating he has been
working as a development engineer for MEL
at Crawlev and is currently involved in the
design of electronic support measure svs-
tems.
Ray Thomas gained his Ph.D. researching
into high-permeability magnetic materials.
Subsequently he spent seven vears in the
electronics industry before joining Brighton
Polytechnic as a lecturer in 1977. His in-
terests are in microprocessor applications
and computer vision systems.
Fig. 8. The hardware, to be described in
the next article, occupies two boards: a
double Eurocard for the control system
and а small p.c.b for the 1532 sensor.
Sensor p.c.b
Main board
Shift
register
Buffer
Image data
store (ram)
Column
counters
ELECTRONICS & WIRELESS WORLD
Digital tv
There is a deep-rooted belief
among broadcasters, including
some engineers, that television |
technology is changing at a fas- |
ter rate than ever before. It is
forgotten that d.b.s. has been
under development since 1965
(and was implied in Arthur C.
Clarke's 1945 article in this jour-
nal); that digitalization of
broadcast-quality video was first
demonstrated in the mid-sixties
at Bell Telephone Laboratories;
and the concept of "The digital
future of television studio cen- |
tres" was propounded by John
Baldwin (IBA) as long ago as |
1972. He suggested then that
while the time when domestic
receivers would receive tv signals
in digital form was still some way
off, and not likely to have signifi-
cant practical impact “before ab-
out 1990”, studio complexes
based on the use of digital tech-
niques would be possible "now"
(i.e. 1972) and that it could well
be that "by 1976 the cost of a
digital studio complex would be
less than its analogue equiva-
lent."
By 1987 it is possible to build
experimental component digital
production units (such as the
ITCA one at Thames Television,
Teddington described in the |
February "Update" column,
pages 197 to 198) using the by no
means low cost Sony DVR1000
recorders now in production and
due to be delivered to customers
very soon. There are also in
widespread use many "digital is-
lands" within studios including
the special effects and picture
manipulators that, in order to
justify their cost, now seem to be |
used (over-used?) on every possi-
ble occasion.
But the large all-digital studio
complex at comparable cost to
current analogue "production
factories" still seem as far away
today as they did at IBC72!
What has happened is that
analogue systems have con- |
tinued to develop and, indeed,
analogue-component systems
promise to provide most of the
promised advantages of digital
video at substantially less cost.
The industry is buzzing with
speculation as to the future role
of the %-inch all-purpose М.И
component v.t.r. machines
| rather more than about the over-
£100,000 DVR1000 machines,
though these, offering superb
quality even after 20 genera-
tions, will certainly fill post-
production role in studios pro-
ducing high-cost commercials. A
major problem with digital v.t.r.
machines is that their high pow-
er consumption largely rules out
their application in portable
battery-operated machines.
Communication engineers in
the early 1970s were in the habit
of suggesting that if valves had
| been developed after transistors
they would have been hailed as
the answer to all problems. To- |
wards the end of a well-attended
IEE colloquium, TV studios from
| AJD, Brian Scott (Thames Televi-
sion) echoed this by comment-
ing that if analogue television
had just been discovered we
would all be hailing it as a mar- |
vellous system with a big future.
He added that new technology
has improved the stability of ana-
logue systems, although we will
still need digital techniques,
even where they remain more
expensive, for some things that
cannot be done analogue. The
pressure for more digits is now
coming more from production
teams than from engineers.
. Better pictures
There remain engineers who be-
lieve that the first priority, ahead
of h.d.tv, should be to ensure
that the pictures transmitted on
the existing 625-line 50Hz inter-
laced standard are of the highest
possible quality. In due course
this could be followed by the
improvements possible with
"component" rather than "com-
posite" working, MAC transmis-
sion on d.b.s. and steady, flicker- |
free displays with progressive
(sequential) scanning made
possible by digital processing in
the receivers, and, later, for
d.b.s. wide-screen pictures by
means of compatibie, enhanced
systems.
In recent years, despite many
improvements, the quality of the
transmitted pictures, particular-
ly with material acquired from
overseas, has tended to fall, part-
ly due to distribution on multi-
generation tape rather than on
ELECTRONICS & WIRELESS WORLD
16 or 35mm film. Similarly, UK |
producers have strained after
“realistic” mood lighting that
often results in “noisy” pictures |
when compared with program-
mes produced in well-lit studios.
Bits all round
An interesting three-part pre-
sentation by BBC research en-
gineers (A. Oliphant, J.T. Zubr- |
zycki and N.H. Gilchrist) showed |
how digital signals couid be
routed in a flexible manner
around a large studio complex
using optical-fibre cables and a
combination of time-division
and frequency (wavelength) divi-
sion multiplexing. There is no
requirement to "switch" the
optical cables, since all sources
will be available at all destina-
tions.
It became clear that this is still
largely a "paper" design though
virtually all of the technology is
currently being developed else-
where for broadband telecom-
munications applications, in-
cluding local area networks, |
с.а.у etc. The BBC work is seen
as meeting a possible require-
ment for the BBC Television
Centre in the mid-1990s.
Essentially the system uses
optical fibres in conjunction
with distributed feedback (d.f.b.)
lasers. Each laser would be mod-
ulated by a 2 Gbit/s stream and
would produce a narrow line-
width output at a specific optical
wavelength. The d.f.b. laser is a
semiconductor laser diode with a
diffraction grating etched over
the active region, resulting in
coherent light output at only the
one wavelength strongly re- |
flected by the grating. This optic- |
al part of the system follows the |
work of Olson et a/ at Bell Labs.
At present d.f.b. lasers are com-
mercially available for only the
two main optical wavelengths
now being used or advocated for
telecommunications.
It was claimed that the system,
though conceived as being used
to route 4:2:2 digital signals,
would be capable of carrying
h.d.tv signals. These would use
the capacity required for four or
five 4:2:2 channels, but could be
multiplexed into the 2Gbit/s bit
streams.
Television in
bits?
Certainly the IEE colloquium
brought forth many expressions
of continued faith in digital tech-
niques in the studios and post-
production areas. Duncan Tho-
mas (BBC) while showing him-
| self by no means fully committed
to bits, stressed that it was now
too late to put the clock back and
that eventually digital tv will win
through.
Most of the papers described
systems based firmly on CCIR
Recommendation 601, the 4:2:2
component-digital standard with
an initial bit-rate of 213 Mbit/s.
While this system includes provi-
sion for hierarchical systems,
both upwards and downwards,
the basic system, as several
speakers pointed out, imposes a
"brick-wall" filter on luminance
at 5.5 MHz and would require a
complete re-think for h.d.tv.
(higher-definition television).
There was, however, nothing but
praise for the trend to digital
sound. This is seen as an entirely
practical means of removing
many of the traditional degrada-
tions of analogue sound.
What could have been fore-
| seen as a confrontation between
component and composite digit-
al v.t.r. machines was the juxta-
position of a paper by Carlos
Kennedy (Ampex) on his com-
panies development of the
ACR225 composite “cart”
machine - and the proposed use
of this composite system for stu-
dio and transportable machines
— with the paper by John Ive
(Sony) on the DVR1000. But the
| sparks did not fly. Indeed, Carlos
Kennedy made a convincing case
that, because of the strained eco-
nomic situation of many US pro-
duction companies, it is certain
that composite 525-line NTSC
| will remain in use for many
| years. Composite machines can
fit comfortably into composite
environments without dis-
couraging Ampex from con-
tinuing development of 4:2:2
component machines.
Television Broadcast was written
by PAT HAWKER.
445
IO BROADCAST
|
Portable stereo |
The difficulty of receiving “noise-
free” stereo from v.h.f./f.m.
broadcast transmissions without
the aid of a reasonably good
roof-top aerial array is well-
known. The problem has been
with us for a long-time. The BBC
is in process of an expensive
conversion to mixed (circular)
polarization in order to improve
reception with portable tele-
scopic aerials and car radio whip
aerials, but there remains the
basic 12dB or so difference be-
tween what is needed for mono |
and that required for good
stereo.
The growing popularity of
large stereo portable receivers
and walk-about headphone sets
incorporating radio as well as
tape-cassette facilities has
tended to highlight the problem. |
A couple of years ago, CBS, in
collaboration with the US
National Association of Broad-
casters, began testing their com-
patible FMX system. This was
claimed as permitting good
stereo reception (on sets fitted
with a special decoder) over vir-
tually the same coverage area as
the mono transmissions. CBS
promoted the system in Europe.
Some engineers were doubtful as
to the performance of FMX and
its effect on conventional receiv-
ers in severe multipath condi- |
tions, but the BBC undertook to
investigate the system provided |
that CBS would loan FMX encod-
ing and decoding units. Many
months went by, however, with
no sign of the experimental
equipment reaching the UK. The
situation has been further com- |
plicated by the reported closure
of the CBS laboratories con- |
cerned with FMX, although pre- |
sumably CBS still holds the pa- |
tents. The prospects for any early
UK trial, let alone operational
use, now seem remote.
Some listeners are suggesting |
that the UK national and local
v.h.f. services should be replan-
ned with extra transmitters to
provide much stronger signals in
the centres of towns. This would
not only be a horrendously ex-
pensive undertaking but would
also upset the current frequency
planning under the 1984 WARC
allocations.
More realistic are the sugges- |
tions that receiver front-ends
446
should be made more sensitive
by reverting to the use of at least
some discrete transistors along-
side the integrated-circuit de-
vices. It would also be sensible
for portable receivers, if provid-
ing stereo, always to have co-
axial sockets fitted to permit |
their use with effective external
aerials. There also still seems to
be a need to get the message
through to more listeners that it
takes a great deal more signal to
provide good stereo reception
than is necessary for mono.
A listener in Paignton sug-
gests that the problems faced by |
v.h.f. broadcasting in the UK go
back a long time, with little
serious effort by either broadcas-
ters or Government to promote |
"superior" v.h.f. as the main ser-
vice, but rather only as sup-
plementary to m.f. services. In
many areas v.h.f. (even mono) is
too weak for good reception on a
lot of portable radios, although
the increasing use of circular
polarization helps (unfortunate-
ly it can in some areas increase
multipath distortion on high-
fidelity equipment). Manufactur-
ers, he suggests, aim at selling
portable radios as cheaply as
possible with little regard to
their sensitivity or audio quality.
When coupled with "unfriendly"
tuning arrangements and un-
clear tuning dials this all serves
to discourage v.h.f. listening by
the general public. Part duplica-
tion, part splitting of the m.f. and
v.h.f. transmitters confuses the
public with few broadcasters
wanting to risk losing audiences
by encouraging them to move
away from the m.f. outlets. In a
local survey he found 10 per cent
of homes with an external v.h.f.
aerial, presumably mostly for
stereo. Compared with South
London this is a very high figure.
There are still more old Band
ИШ television aerials to be seen
than aerials for Band II!
Copyright
reform delayed
Whether the marketing of R-DAT
cassettes and machines will
finally get under way in Europe
this spring, as the Japanese in-
dustry hopes, or whether it will
be further delayed by the con-
tinuing arguments about the
need to incorporate anti-copying
| devices to protect the CD indus-
try, is only one of the problems
that continue to accumulate
over the whole field of intellec-
tual property and patent legisla-
tion.
A recent unannounced trial in
the UK by the Werner video
software company of the “Mac-
rovision” anti-copying system |
for VHS video tapes seems to |
have done little to inspire confi-
dence in an anti-copying system
that can be rendered largely in-
effective by relatively simple
modification of existing VHS
| machines and is not designed to
prevent copying on Betamax
machines.
| nificant evidence of any large-
scale copying by video libraries.
Macrovision, developed by John
Ryan, formerly with Ampex, is
| intended to stop the copying of
videos or the programmes on
premium cable channels by the
the colour-burst reference sig-
nal. This results in fuzzy pictures
with spurious or no colours
replayed on VHS machines.
Japanese industry continues
to resist the appeals of the inter-
national recording industry,
concerned at the possible impact
of R-DAT on the CD digital discs,
that an anti-copying chip should
be built into al! R-DAT machines
and different sampling rates, etc.
industry is stil! hoping to obtain
better copyright protection by
means of EEC and US legislation.
The problem is heightened by
the likelihood of blank R-DAT
tapes becoming readily obtain-
able at a time when pre-recorded
tapes may be very limited in
choice.
The 1986 Government White
Paper prepared by the DTI (“In- |
tellectual property and innova-
tion” Cmnd 9712) proposed
radical changes which the DTI
saw as being necessary to en-
courage industrial innovation, to
keep abreast of the new copying
and recording technologies and
to simplify and reduce the cost of
obtaining patent and design pro-
tection. One of its many propos-
als was to legalize home taping of
audio (but not of videos or com-
puter programs) while introduc-
ing a compensating 10 per cent
The trial did not produce sig- |
addition of phase-modulation to `
when tapes are copied and then |
should be used. The recording |
levy on blank audio tape cas-
settes.
However although the White
Paper was generally welcomed,
the proposed levy ran into а lot of
flak from tape manufacturers —
as did some of the proposals for
restricting to the original manu-
facturers the supply of special
Spare parts.
The White Paper has not been
followed up by the expected Gov-
ernment Bill. There was no men-
| tion of any new copyright legisla-
tion in the Queen's speech at the
opening of Parliament last au-
tumn. This virtually ensures that
no bill based on the DTI propos-
als will appear before the General
| Election, if ever, and the whole
question could become en-
meshed in EEC directives and
the extremely complex web of
the very different intellectual
property legislation in different
countries.
Meanwhile further significant
advances seem likely to be made
during the next decade over the
whole field of magnetic record-
ing. Progress in packing density,
access times, transfer rates and
magneto-optical recording may
| increasingly come to overwhelm
information-storage and record-
ing systems based on optical and
photographic techniques. It is
foreseen that before very long it
will be possible to record as well
as play back compact discs by
using magneto-optical tech-
nology.
In recent years, the US has
encouraged more university re-
search and education in magnet-
ic recording with specialist cen-
tres at Carnegie Mellon Universi-
| ty, Pittsburgh and the University
| of California at San Diego
(UCSD).
| Radio Broadcast was written by
PAT HAWKER.
Guide to
Broadcasting
Stations
The 19th edition of GBS is
now available at £6.95 or
£8.70 by post from book-
shops or from Heinemann
Newnes, Freepost 10, London
WIE 7YZ.
ELECTRONICS & WIRELESS WORLD
CB, RIS and the
Home Office
In November 1981, following
several years of public con-
troversy, the first 27/934 MHz
CB licences were issued in the
UK. The initial response, though
more muted than forecast,
quickly raised the number of
licences to over 450,000, despite
continuing protestations that
the licences ruled out the use of
amplitude modulation (a.m. and
s.s.b.) and that the 27 MHz chan-
nels did not coincide with those |
widely used elsewhere. The
growth of both illegal and legal
ing 1986, most of them only
intermittently. RIS raided 70 of
these on 209 occasions, with 74
prosecutions (only about one
prosecution for each three
raids). DTI are satisfied that they
have adequate resources to keep
this problem under control.
With Radio Laser back on the air,
| therearethree unauthorized sta-
CB was reflected in a massive |
surge in the number of com- |
plaints of interference to tv re-
ception made to the old Radio
Interference Service, still then
operated by British Telecom |
teams and providing free inves-
tigation of interference to radio
or television.
The number of CB licences
began to fall after the first year
and currently are down to
122,920, about one-third of the |
peak figure. RIS became the
DTI's own Radio Investigation
Service with a significantly re-
duced staff and a £21 fee was
introduced during 1985. This re-
sulted in a dramatic falling off in
interference complaints made to |
the DTI (from about 1900 to 375 |
per month). Many viewers have
been seeking assistance from the
broadcasters, who have neither
the resources nor the legal
powers/experience/diplomatic
approach of the DTI. One result |
has been to increase personal
antagonisms and conflicts be-
tween the parties concerned,
particularly where the CB oper-
ators and radio amateurs are
operating in full accordance with
the terms of their licences and
the problem arising primarily
from the lack of ‘immunity’ of
many consumer-electronics re- |
ceivers and appliances.
The smaller RIS has concen-
trated its activities primarily on
attempting to close down illegal |
‘pirate’ broadcasters, though it
has proved more successful at |
tracing and seizing transmitters
than catching and prosecuting
people.
According to a recent reply by |
Lord Lucas, Parliamentary
Under-Secretary of the DTI, 83
land-based unlicensed UK broad-
casting stations were active dur-
tions broadcasting from two
ships off the UK coast, with RIS |
now proposing to allocate furth-
er resources to coping with this
problem.
CB is one of the services for
which the Home Office is re-
sponsible for policy, the DTI for
spectrum regulation. It is ex-
pected that the UK government
will adopt, during 1987, a recom-
mendation (T/R 20.02) by the
Conference of European Posts
and Telecommunications
(CEPT) that there should be a
common (harmonized) Euro-
pean allocation between 26.965 |
and 27.405 MHz for frequency-
modulation only. The UK gov-
ernment is continuing to resist
pressures from "a few" CB enthu-
siasts to permit the use of single-
sideband, on the grounds that it
is more likely to cause interfer- |
ence to other users of the radio
spectrum.
The Merriman Committee
commented on the need for im-
proved monitoring and policing
of the air-waves and it is perhaps
‘unfortunate that in many Euro-
pean countries the "pirates" (CB
and unauthorized broadcasting)
have shown that persistence
often brings the reward of licens-
ing or toleration. Would CB ever
have been authorized on 27 MHz
in the UK otherwise? Commun-
ity radio, which has a genuine
place in the broadcasting spec- |
trum if finally it comes, will owe
its existence to the pirates — just
as the origins of Independent |
Local Radio can be traced to the
pirate ships of the 1950s.
The Spanish authorities are
planning to spend some &26-
million over the next few years in
policing the radio spectrum, in-
cluding establishing main sur-
veillance centres in Madrid, La
Coruna, Barcelona and Valencia,
50 smaller monitoring units, 14
mobile units and a satellite sig-
nal sampler. The fixed and
mobile units will use modern d/f
systems to trace illegal transmis-
sions, although it seems unlikely
that any great effort will be made
to close the several Fundred "pri-
ELECTRONICS & WIRELESS WORLD
vate" radio broadcasting stations | fact that the user is not making a
that have existed for many years
in Spain.
Mobile safety
codes
The inclusion in the new edition
of The Highway Code of the
recommendation against using
handheld microphones or tele-
phone handsets while driving,
together with the injunction that
“you should only speak into a
fixed, neckslung or clipped-on
microphone when it wou!d not
distract your attention from the
road" is clearly putting increased
responsibility on the users of
mobile radio. What does or does
not "distract attention" tends to
be a highly subjective judge-
ment, on which the parties to
any legal dispute are unlikely to
agree.
But the new recommendation
has served to concentrate minds
on the general problem of mobile
radio safety. The independent BT
Road Safety Committee has re-
cently drawn up a new and stiffer
Cellphone Safety Code which is
being sent to all existing Cellnet
customers and brought to the
attention of other cellular radio
services. More stress is being
placed on the not-always-
call does not mean that there are
no transmissions, since the
transmitter automatically re-
plies to the interrogations.
The new Cellnet code includes
the recommendation: “Always
switch off your Cellphone when
at a refuelling point even if you
are not refuelling your own car.”
Whether this practice has been
observed fully in the past is open
| to doubt. Some installations are
|
wired to be switched indepen-
dently of the ignition.
In papers presented in 1975 at
IEE and IERE conferences, a
Bradford University team includ-
ing Dr Peter Excell, G.H. Butch-
er and D.P. Howson reported
that “practical tests” had shown
that a potential hazard exists
during the fuelling of a vehicle
containing an operating trans-
mitter, or parked close to
another vehicle containing one.
This arises from the possibility of
a spark occurring at the most
hazardous point, between the
fuel nozzle and the tank inlet.
They wrote: “Existing injunc-
tions not to operate a transmitter
while fuelling a vehicle contain-
ing it need to be strengthened:
transmitters should not be oper-
ated anywhere within fuelling
stations. Possibly electro-
mechanical interlocks could be
| applied to advantage here.”
appreciated need to avoid trans- |
mitting while refuelling or while
on the forecourt of a petrol-
filling station. Unlike conven-
tional mobile radiophones,
where the user has direct contro! |
vered in their safety codes. It is
| less likely to be known by the
over his transmitter, cellular
radios are subject to frequent
“interrogation” of the mobile
unit by the base station to check
that the vehicle is still within the |
same “cell” area. Most cellular
radios stay “оп” as long as the
ignition switch is turned on; the
It is recognized that sparks are
more likely in the case of the
higher-power mobile h.f. trans-
mitters as used by a few radio
amateurs but this hazard has
long been recognized and co-
large number – now well over
100,000 — of users of cellular
radio.
Radio Communications was
compiled by PAT HAWKER.
447
EN
INTEGRATED CIRCUITS
PHONE
0474 60521
4 LINES
STKO25
STKO78
STK085
STK433
P. M. COMPONENTS LTD
SELECTRON HOUSE, SPRINGHEAD ENTERPRISE PARK
SPRINGHEAD RD, GRAVESEND, KENT DA11 8HD
TBA54C
TBAS40Q
ТВА5500
TBA560C
TDA2532
TDA2540
TDA2545A
TDA2451
1.95
1,95
2.15
2.15
TELEX
966371
TOS—PM
CATHODE RAY TUBES Please add £3 additional carriage per tube.
AN124 2.50 1.00 3TK435 TBA460CQ TDA2560 215 CME822Ww 19.00 DH3-91 55.00 M38-103GR 65.00
AN2140 250 1.50 STK437 TBAS70 TDA2571A 4.50 CME822GH 25.00 0H7.91 45.00 M38- 120W 65.00
AN240P 280 1.70 STK439 TBA651R TDA2581 2.95 CME1428GH 45.00 DP75 35.00 M38-120WA 65.00
AN612 2.15 MC1349P 1.20 STK461 ТВА720А 1042593 2.95 CME1428W 39.00 DP76 35.00 M38-121GHR 65.00
AN7116 1.50 МС1351Р 1.50 STK463 ТВА7500 TOA2600 6.50 CME1523W 39.00 DN13.78 35.00 M38-121LA 65.00
ANTMO 3.50 МС1357 2435 TATOOTAP ТВАВОО TDA2610 3.50 CME 1431GH 39.00 F16-101GM 75.00 M38-122GW 65.00
ANTAS . 150 merasa 158 TALI oa TBASIOAS ТОА2611А 1.95 CME 1431W 39.00 F16-101LD 75.00 M3B-140LA 65.00
ANM 3399 || MOMS 399 ТАД BABIOR TOA2640 3.50 CME202GH 45.00 F21-130GR 75.00 M38-142LA 65.00
BA521 3.35 МС 1496 1.25 ТА71ЗОР TBAB20M < d F21-190LC ЕВ
Е ТОА2680А 2.75 CME2024W 45.00 21-130LC 75.00 M38-341P31 65.00
CANC. à 46 D cd ^ 95 ADAM 1808200 TDA2690 2,45 CME2325W 45.00 F31-10GM 75.00 M38-344P39 65.00
CANE qu MC1723 050 TA7204P TBA92. TDA3310 2.95 CME3218W 45.00 F31-10GR 75.00 M40-120W 59.00
HAT366W 350 МС3357 275 TA7205AP ТВА950:2Х 235 TDA3560 5.50 CME3132GH 45.00 F31-10LC 75.00 M43-12LG/01 65.00
НА1377 350 мі231 1.75 ТА7222АР 784990 149 UPCS66H 2.95 CME3155W 45.00 F31-10LD 75.00 Md4-120LC 65.00
HAT156W 1.50 MSM5807 675 TA7227P 4; TCA270 150 UPCS75C2 2.75 CRE1400 25.00 F31-12LD 75.00 М50-1206Н 65.00
HA!339A 2.95 PLLOZA 5.75 TAT3OP 1.80 TCA270SQ 1.50 UPC1025H 1.95 CV1450 35.00 F31-13GR 75.00 M50-120GR 65.00
НА\398 2.75 SAASOOA 3.50 TAT313AP 2.95 TCA650 3.50 UPCIO2BH 1.95 21526 19.00 F31-13L0 75.00 M50-120GV 65.00
НА!551 — 2,95 $АА!025 7.25 TA7321P 2.25 TCA9AC 1.65 UPCIO32H 1.50 CV2185 15.00 F31-121G 75.00 MS50-120LC 65.00
LA123 1.95 SASS60S 1.75 TA7M6P 250 TDA440 350 UPCiI56H 2.75 С\2191 19.00 Fa1-123LC 185.00 ЗЕЗА/РЗ1 40.00
LA4031P 1.96 5455705 1.75 TA7609P 3.95 TDA1001 2.95 ОРС1158Н 0.75 С\2193 15.00 F41141LG. 185.00 SE4/D/P7 45.00
LA4102 295 SASSBO 2.85 TAT6INAP 2.95 TDA1002A 2.95 UPC1157C2 1.95 Cv5119 85.00 F41-1421C 185.00 SE42BP31AL 55.00
1А4140 — 2.95 519178 7.50 TAA3I0A 3.50 ТРАТООбА 2.50 UPCIIBIH 1.25 Cv5320 85.00 M7-120W 19.00 SE428P31 55.00
LA4400 4.15 SL1310 1.80 TAA320A 3.50 ТОА1035 2.50 UPCIIB2H 2.95 CVX389 55.00 M7-120GH 19.00 SESFP31 55.00
LA4420 1.95 5.1327 1.10 TAAI50A 3.50 TDA1037 1.95 UPCI185H 3.95 D9-110GH 39.50 M14-100GM 45.00 T948H 65.00
LA4422 2.50 5113270 1.10 ТАА570 1.95 TDA117¢ 1.95 UPC1191V 1.50 D10-210GH 45.00 MI4:1001C. 45.00 V5004LD 59.00
[А443 2.50 SN76003N 3.95 TAAG61B 1.95 TDA1190 — 2.15 UPC1350C 2.95 D10-210GH68B 65.00 M17-151GVR 175.00 V6048CAL 59.00
144461 395 SN76023N 3.95 TBA700 . 1.70 TDA 2700 UPC1353C 2.45 D10-230GH 35.00 MI7-151GR 175,00 V6048J 49.00
terio 12 SN76033N, (2:55 TBAT20AS/8ICI ТОА1327 UPCI365C 3.95 D10-230GM 35.00 M19-100W 45.00 V6064BP31 55.00
terio 350 SNZGUION: 10:09 SASBTIU 100 042002 UPC2002H 1.95 D10293.GY/90 55.00 M19-102W 55.00 V6069GH 55.00
perian — S850 SNTGTISN 1:25 TBARS огоо Rew 555 0.36 D13-30GH 49.50 23-110GH 55.00 V6070P31 65.00
LM324N 0.45 SN76131N 1.30 TBA396 075 TDA2004 E ото D13.51GU26 5665 И FA Мец kd
LM380NB 1.50 SN76226DN 2.95 TBA440N 2.55 TDA2005 5 4 а ыр, ‘ н
LM380N14 1.75 SN76226N 1.05 TBA4800 125 TDA2006 723 0.50 013-51GM/26 85.00 M23-112GM 55.00 V7031GH 59.00
LM383T 2.95 SN76533N 165 TBASIO 2.50 TDA2020 741 0.35 013-456 Н/01 55.00 M23-192GV 55 00 V7031/67A 59.00
LM3900N 3:50 SN76544 2.65 ТВА5100 2.50 TDA2030 747 0.50 D13-610GH 59.00 M23: 112GW 55.00 V7035A 49.00
M51513L 2.30 SN76650N 1.15 TBA520 1.10 ТОА2522 748 0.35 D13-511GH 59.00 M23-112KA 55.00 V7037GH 45.00
M51515L 2.95 jN76660N 0.80 TBAS20Q 1.10 TDA2523 7805 0.65 013-611GM 59.00 M24-120GM 59.00 VB004GR 65.00
M51521L 1.50 57К014 7.95 ТВА530 1.30 TDA2524 7808 0.60 D13-630GH 59.00 M24-120LC 59.00 VB006GH 65.00
MB3712 2.00 STK015 7.95 T8A5300 1.10 TDA2530 7815 0.65 D14-150GH 75.00 M24-120WAR 59.00 V8010A 65.00
014-150GM 75.00 M24-121GH 55.00 ЗВР! 11.50
80232 BFT42 0.35 R23 0.58 D14-162GH/84 59.00 M?8B-12GH 55.00 ЗОР! 11.50
SEMICONDUCTORS BD233 0.35 BFT43 0.35 92323 0.56 014-172GR 55.00 M28:13LC 49.00 3H/OBM 55.00
BD234 0.35 BFW392 0.85 R2540 2.48 D14-172GV 55.00 M28B-13LG 49.00 3WPI 18.50
BD236 0.49 ВЕХ29 0.30 HCA16334 0.90 014-1736 Н 55.00 M28-13GA 49.00 4EPI 30.00
AAY12 025 BC1B3L 0.09 BD237 0.40 BF X84 0.26 RCA16335 0.80 014,1736М 53.00 M28-131GR 55.00 5ВНРІ 30.00
АС125 020 BCIBALB 0.09 80238 0.40 ВЕХ85 0.32 SKESF 1.45 D14-173GR 55.00 M28-133GH 55.00 SBHPIFF 30.00
ACI26 0.45 BC204 0.10 80242 0.65 BF X86 0.30 TIP29 0.40 D14-181GH/98 65.00 M31-101GH 55.00 5ВНРЗ1 30.00
ACI27 0.20 BC207B 0.13 BD246 0.75 BFX68 0.25 ТІР29С 0.42 014-1816.) 55.00 M31-182GR 55.02 5СР! 10.00
AC128 0.28 2088 0.13 80376 0.32 BFYSO 0.21 TIP30C 0.43 D14-181GM 53.00 M31:182GV $3.00 5TO1A 15.00
к 00/35 8C212 985 80410 0.65 ВЕУ51 0.21 TIP31C 0.55 D14-181GM50 59.00 M31-184W 65.00 бЕР7/5 38:00
2r BC212L 0.09 BD434 0.65 BFYS2 0.25 ТІРЗ2С 0.42 014-182GH 59.00 M31-184GH 85.00 138P! 13.50
к Hea E23 0.09 80437 0.75 BFY90 0,77 TiP33C 095 014-2008Е 89.00 M31-184P31 65.00 13ВРА4 17.50
с! 43 5 BD438 0.75 BLY48 1.75 ТІРЗАВ 0.95 D14-200GA/50 85.00 M31-185W 69.00 17DWPA 25.00
AC176 0.22 Bc213L 0.09 BD520 0.65 BRY39 0.45 ТРАТА 0.45 2006 р Чү
AC176K 031 ВС214 0.09 RO TIPAIC 0.45 014:200GM 75.00 M31:190GH 55.00 32J/1085 69.00
тт ЕЧ BC214C 0:09 Враз [ы А 025 TC bap D14-210GH 75.00 M31-190GR 55.00 1273 39.00
АС187К 0.28 BC214L 0.09 80589 0.45 BR103 0.55 ТІР47 ^ 0.65 D14-270GH/50 75.00 M31:190LA 55.00 1564 45.00
| Ко: = bj Я 014.310 110.00 М31:1916У 55.00 1844 80.00
AC188 0.25 BC237B 0.09 80701 1.25 BAC4443 1.15 TIP120 0.60 ^.
ACIBBK 0.37 BC238 0.09 80702 1.25 ВТ100АЮ 20.85 TIP125 0.65 D14-320GM/82 65.00 M31-220W 59.00 9442E1 75.00
АСУ17 1.15 BC239 0.12 80707 0.90 BT!06 1.49 TIP142 1.75 DIVI CHOGHNM 45.00 M31-270GY 65.00 95447GM 78.00
AD149 0.70 BC251A 0.12 BDX32 1.50 БИШ 1.20 TIPI61 2.95 014.340КА 45.00 M31-271P31 65.00 95449GM 75.00
AD161 0.39 BC252A 0.15 ВЕ115 0.35 ВТ119 3.15 TIP2955 0.85 016-100GH 65.00 M31-271GW 65.00 770963 78.50
AD162 0.39 BC258 0.25 КАШ 0.35 BT120 TIP3055 0.55 вова 59.00 M31-271W 65.00
С258 А ВЕ119 0.65 But05 11591 0.20 16-100 65.
M^ wed EC oge ро gs f auim MEC | село өю | SPECIAL OFFER
AF IVA 195 BC300 0.30 BF 154 0.20 BU124 2N1308 1.35 D16-100GH/97 65.00 WIREWOUND
AF118 295 BC301 030 BF 158 0.22 80126 2N2219 028 D18-160GH 69.00 High Reso'uhan Philips 127
i ae BF160 0.27 BU204 22222 029 D21-106H 65.00 M31-325GH £35.00 each coiis RESISTORS
AF116 2.95 BC303 0.26
AF117 295 BC307B 0.09 BF167 0.27 BU205 2N2905 0.40 DG7.5 55.00 trans available
REVS; oe BCI 090 ВЕ173 0.22 BU208 243053 0.40 087.6 35.00 4 watt 2R4-10K 020
AF124 0.65 BC328 0.10 Bei? 0.38 BU?08A 243054 0.59 087 36 55.00 M36-141W 75.00 7 watt R47-22K
AF125 0.35 BC337 010 Сашы 025 0200 ee A 022 067 32 45.00 M36-170LG 75.00 11 watt 1R-15K
E ct я U32 d 06132 45. 101GH 6 17 1R-- 15K
AE 126 0.32 ВС338_ Ere 8F180 0.29 BUA07 2N3703 012 з ры мз “ш ш „ДЕ
AF127 0.65 3 BF181 0.29 BU500 2N3704 0.12 А
жю ою | ваз ою | Sme ота | Rem Ae Өз VIDEO SPARES & HEADS
AF1SO 0.60 BC478 0.20 BF182 0.29 81526 233706 0.12
AF178 195 BC527 0.20 BF184 0.28 BU80Y 2N3708 0.12
AF239 0.42 BC547 0.10 BF185 0.28 BUY69B 243733 9.50
AFZ12 375 BC548 0.10 BF194 0.11 MJ3000 2N3733 2.75 VIDEO BELT KITS
0.10 BF195 0.11 MJE340 2N3792 1.35 ч =
Ай а Н т 0.14 BF196 0.11 MJE520 244427 1.95 Ака! У59300/9500/ Sanyo УТС 5500 3.75
отта ВС557 0.08 BF 197 9.11 MPSA13 2N4444 145 VIDEO HEADS 9800 3.75 Sanyo УТС 9300... 3.75
AU113 5.95 F 1 MPSA92 2N5294 3HSS Suitable for Most JVC and Ferguson 3V16 450 Sanyo VTC 9300P 3.90
BCIGIA б! Besse Ош ROM в MRF237 285296 Ferguson models 29.50 JVCH HR 3330/3600 4,50 Sharp VC 6300 3.75
BC 1078 H 10 BCY33A 1.60 ВЕ200 0.40 MRF450A 2N5298 3HSS(H) Sultable for Hitachi JVC НЯ 3360/3660 4.50 Sharp VC 7300 3.75
BC1088 — 0.12 BD115 0.30 BF241 0.15 MRFA453 2N5485 VT5000, VT8000, VT6000 УТ8500, Panasonic NV 300 4.00 Sharp VC 8300 375
0.10 BDI24P 059 BF245 0.30 МАЕ 454 245496 VT7000 33.95 Panasonic NV 20008 3.75 Sharp VC 9300 3.75
сто. 012 BD131 0.42 BF257 0.28 MRF455 2SA715 4955 Surtable tor most National Panasonic 3000B 3.75 Sony SL 30008. 3.75
асс 012 50332 ous BF 258 0.28 MRF475 25С495 Panasonic Models. 33.95 Panasonic NV7000 3.50 Sony SL 8000/8080. 4.50
D 33 a BF 259 0.28 MRF477 250496 4HSS(UIN) Suitable for Panasonic Panasonic №\86008/ Sony SL C7/J7 4.00
8С114 on EO) 040 ВЕ271 0:26 MRFB38 28C 1096 Models 370 and 380 33.95 86 10B/VOII 3.75 Toshiba 5470
BCIIGA 0.15 80135 0.30 BF273 0.18 2561106 Р
BC117 0.19 BD136 0.30 BF336 0.34 2$С1172% t
. AMIX VI EADS
ә ом | CENE | Bko? o% 2501173 eE ла SANYO ORIGINAL VIDEO PARTS
BC н 25 с ED TaS ба ВЕЗЗ8 0.32 251306 Toshiba 5000 Seres and I SANYO ORIGINAL
3 0.20 | BF355 0.37 25С1307 PV2400 39.50 PART NUMBER MODEL DESCRIPTION
BC140 0.31 80140 0.30 BF362 0.38 2801364 -B Suitable lor Sony 818000, 4-529-10800B VTC5150 Вее! Motor 3 6W 9.95
ВС141 0.25 80144 1.10 Е: 291449 RSV-3-8 Suitable lor Sony 518000
С д 87363 0.65 setae $8080. SLD7ME 39.50 4-527T-23501 VARIOUS — Motor Assy 9.75
8C 142 0.21 BOISOC 0.29 BF371 9.25 2501678 SA-10-R $ийаше for Sony SI 4-527V-51000 5150 Capsion Motor 29.95
80159 0.65 BF394 0.19 25С1909 DSA:10-A Suhabi ony SLCS,
BC 143 0.24 5 6 F2 . 2261802 SLC6. SLC? 39.50 143-0-4904-00900 FVHP615 Gear Idler Assy 5.95
acura got 0-9 180 ВЕ? 992 2861954 Sanyo Head lor 143-2-457T-05900 VTC9455 Stopper Reel Base 0.55
BCI4BA 0.09 80166 0:95 BFa58 0:36 5861957 УТС9300/9500 49.50 143-0-545T-01701 VARIOUS Pinch Roller Assy 8.95
Вова 0.09 Boye 072 BF4 0.36 2561969 Sanyo Head tor УТС 143-0-545T: 01700 VARIOUS Pinch Roller Assy. 1.95
BC149 0:09 80181 0:45 Ры 0.68 3 5300/5000 49.50 143.0-551T-VTC9300 Idler Assy 0.95
8C157 0.12 80182 0.70 BF494 0.45 143-0-661T-03800 VARIOUS — Loading Roller 0.95
BC158 0.09 80163 эло BF495 0.45 143-0-662T-01201 VTC5150 Вее! Dnve Putiey 8.50
BC159 9.09 BD20 0.83 BF595 0.23 143-0-9974-00100 FVHP615 — Mod Kit IC ВАбЗ04А 1.95
BCI74A 0.09 80202 0.65 ВЕ997 025
BC177 0.15 80203 0.78 iy ў
BC178 0.15 В0204 070 Hier о Video Head Cleaning Tape (VHS Automatic wevdry) 6.50 VIDEO ALIGNMENT TAPES
ВСтв2 0.10 B0222 0.46 BFRBB 0.30 28C2371 Video Head Aerosol Cleaner " | 0.85 $-2P Colour Bars 30 min 49.50
BC182LB 0.10 B0223 0.59 BFR90 1.50 250234 0.50 Video Copying Lead and Connector Kit Z/V 7.95 S-3P Stairsteps 30 min 49.50
BC183 0.10 B0225 0.48 BFR91 175 R2010B 1.45 3SK8B 0.95 =
BY208-800 0.33 IN400 . VARICAP TUNERS PUSH BUTTON UNITS
DIODES | 352525 55 | mo ooa | LINE OUTPUT TRANSFORMERS | EMTMULTPLERS |
Bv223 0.90 IN4004 0.05 ITT CVC20 6.35 ELC1043/05 MULLARD DECCA. ITT CVC206WAY 7.95
BY298-400 0.22 1N4005 0.05 ІТТ СУСЗО 6.35 ELC 1043/06 MULLARD 8.65 ITT VCV5-7-WAY 10.19
Ever 800 0.22 13007 0.06 DECCA 10: 7.95 PHILIPS G8.550 6.96 U321 8.25 PHILIPS G8 (550) 6-WAY 14.49
YX10 0.20 N4148 0.02 A 1700 MONO 9.95 RANK Т20 6.91 0322 8.25
BYX36-150A IN4448 0.10 A 173 8.95 THORN 3000/3500 7.57 U324 11.00
0.20 145401 — 012 A 2230 peu THÓRN 8500 8:00 200MA QUICK BLOW FUSES
BYX38-600R INS402 0.14 СЕС 2040 8.95 THORN 9000 8.00 100MA peach
9.60 45403 0.12 GRUNDIG 1509 15.45 UNIVERSAL TRIPLER 5.45 200MA - 5 AMP бавен
BYX55-600 0.30 145406 — 0.13 SRINDIG 510-6010. 2222. 5011-6011 Bos
BYX7 1.75 N5407 0.16 пынан ШОШ,
1-600 1. и b 13.45 VA1040
агро 03$ | мыш оле ITI CVC20 8.20 REPLACEMENT VA1056S 20MM ANTI SURGE FUSES
S4B 8.00 17744 0.04 ІТТ CVC30 8.25 УА1104
CS107 1650 ITT923 0.15 PHILIPS GB в50 | ELECTROLYTICCAPACITORS | vassso ТООМА-ВО0МА 15р each
OA47 0.15 ITT2002 PHILIPS 69 8.99 VA1097 1A-SAMP 12p each
ОА90 0.10 PHILIPS 611 13.99 DECCA 30(400-400/350V)
OA91 0.15 ZENER РУЕ 725 10.95 DECCA B0/100 (400:305¥)
OA95 0.10 E ЯВМ T20A 1240 | DECCA 1700
OA202 0,20 DIODES TANDBERGE 9 11.15 (200-200-400-350V) m
142109 5.00 TELEFUNKEN 711A 11.18 GEC 2110 (600/300V) HEAT SINK COMPOUND PUSH PULL MAINS SWITCH
1N238 5.00 BZX61 Seres THORN 159 9.50 ITT CVC20 (2007400 FREEZE IT (DECCA, СЕС. HANK THORN
IN23C 5.00 0.15 THORN 8000 23.50 PHILIPS G (600/300%) SOLDA MOP ETC) 1.02
IN23ER 5.00 BZY88 Senes THORN 9000 9.95 PHILIPS G9 (2200x 63V) SWITCH CLEANER PYE IF GAIN MODULE 6.99
IN22WE 5.00 0.10 THOAN 9800 2240 PHILIPS G11 (470/250V) W040 ANODE САР {27кУ) 0.69
448
ELECTRONICS & WIRELESS WORLD
РНОМЕ
0474 60521
4 LINES
А SELECTION FROM OUR
Р. М. COMPONENTS LTD
SELECTRON HOUSE, SPRINGHEAD ENTERPRISE PARK
SPRINGHEAD RD, GRAVESEND, KENT DA11 8HD
STOCK OF BRANDED VALVES
714 24.50
834 7.50
998 11.50
2087 11.50
2134 14.95
2293 5.50
35.00
37.50
27,50
11.50
24.00
24.00
4.00
4.00
59.75
39.00
39.00
6.00
14.00
0.70
1.25
2.00
4.50
2.50
2.00
55.00
25.00
27.50
22.00
20.00
20.00
55.00
1134 32.00
1148A 115.00
11491 195.00
1150 135.00
1534 32.00
29.50
СЗ 0.90
1K 1006 3.50
CV Nos pnces
оп request
)3A 27.50
53 1.20
ЈА41 22.50
)A42 17.50
)^490 4.50
)A100 125.00
)AF91 0.70
)AF96 0.65
C70 1.75
290 3.50
9C X-4-5000
25.00
IE TIC 28.50
JET18 28.50
ЭЕТ22 35.00
DET23 35.00
DET24 39.00
DET25 22.00
DET29 32.00
OF91 1.00
0592 0.50
0:96 0.65
OF97 1.00
DH63 1.20
OH77 0.90
DH79 0.56
DH149 2.00
OK91 0.90
DK92 1.20
0135 2.50
0163 1.00
DL70 2.50
Dc73 1.50
0192 0.95
Dc93 1.10
[7.94 2.50
0.96 2.50
DLS10 13.50
DLS16 10.00
DM70 2.0
OM160 4.50
Dv51 1.50
DY86/87 0.65
0%802 0.72
E55L 49.50
EBOL 29.50
ESIL 12.00
Е82СС 4.50
E83CC 4.50
E83F 5.50
Е86С 9.50
ЕВ8С 7.95
E88CC 3.50
EB88CC Siemans
Special 5.95
E90CC 7.95
E90F 7.95
E91H 4.50
Е92СС 3.95
Е99Е 6.93
Е 30% 18 50
E182CC 9.00
E180F 6.50
E186F 8.50
E188CC 7.50
EIT 15.00
E280F 19.50
283CC 12.00
E288CC 17.50
E610F 29.50
E1148 1.00
EASO 1,00
EA52 35.00
EA76 1.95
ЕА79 1.95
ЕАВСВ! 0.70
ЕАС91 2.50
EAF42 1.20
ЕАЕВО! 2.00
EB34 1.50
EB41 3.95
EBs! 0.85
EBC33 250
EBC41 1.95
ЕВС 1.50
EBC90 0.90
EBC9) 0.90
ЕВЕ80 0.95
ЕВЕВЗ 0.95
Eeres 0.95
ЕВЕ89 0.70
ЕВЕ9З 0.95
EBL! 2.50
EBL2 2.00
EC52 0.75
EC70 1.75
Есе! 7.95
Ece6 1.00
ЕС88 1.00
EC90 тю
EC91 5.50
ЕС92 1.95
1.50
7.00
1.10
12.00
3.50
3.50
3.50
1.15
ЕСС81 Spec
Quality
Ecc82 0.65
ECCB2 Phiips
1.95
ECC83 0.65
ECC83 Вгитаг
135
ECC83 Philips
1.95
ECC83 Siemans
2.50
ECC83 Tungsram
1.50
ECC85 0.75
ECC86 2.75
ЕСС88 0.95
ЕСС91 2.00
ECC!80 072
ЕСС189 1.95
ЕСС8015 3.50
ЕСС803$ 4.95
ECC804 0.60
ЕСС2000 1200
ECFeo 1,15
ЕСЕ82 1.15
ECF86 1.70
ECF20 185
ECF202 1.65
ECF801 0.85
ECF805 2.50
ECF806 10.25
ЕСНЗ 2.50
ЕСН4 3.00
£CH35 3.50
ECH42 1.50
ЕСНВЇ 1.00
ECH83 1.00
£CH84 1.00
ECH2000 150
ECL80 0.60
ECL82 0.79
ECL 2.50
ECL84 0.74
ЕСІ85 0.69
ЕСІ86 0.95
ЕСІ 80 0.69
EF37A 2.50
EF39 1.50
ЕРА! 4.50
ЕҒ42 3.50
EF50 2.50
EFSS 4.95
EF70 1.20
EF71 1.50
EF72 1.20
EF73 1.00
ЕРВО 0.55
ЕРӨЗ 3.95
EF85 0.50
EF86 2.25
EF86 Мипаға
4.50
ЕҒВЭ 1.50
EF91 1.95
EF92 2.15
EF93 0.95
EF94 0.95
EF95 1.95
€F97 0.90
EF98 0.90
EF183 0.65
EF184 0.65
€F730 1,80
EF731 3.50
EF732 3.50
EF800 11.00
EF804S 19.50
EF805S 19.50
EF806* 14.50
EF812 0.65
EFL200 1.50
EH90 0.72
€K90 0.95
EL32 0.95
233 5.00
2.50
EL34 Mullard
Philips 4.50
EL36 1.95
EL37 9.00
EL38 6.50
Elat 3.50
EL42 2.00
ЕКВ! 6.95
EL83 7.50
2184 Вита! 0.95
EL84 Mullard 2.95
EL85 4.50
ELe6 1.25
EL90 1.75
EL91 6.00
EL95 1.75
EL153 12.15
EL'83E 3.50
EL18P 3.50
EL36C 5.75
EL500 1.40
EL504 1.40
EL509 5.25
Et519 6.95
EL802 3.65
ELB21
EL82
EMT
ЕМА
EMBO
ЕМ81
EMB4
ЕМ85
Емв?
EN32
ENS)
EN92
EX3
ЕҮ51
ЕҮВ!
Eva3
Eves
EYB6/87
ЕҮВВ
Ev91t
Ev802
Е240
Е241
Е280
E28
E290
F606
FWA/800
GTN175M
GTR150W
GU20
6450
GXUI
GXu3
GXuS0SS
GY501
GY802
6230
62731
6232
6233
6234
6237
HAAI
HABCBO
HBC90
HBC91
HF93
HF94
HK9C
HL2K
412300
нат
HL420D
HL90
HL92
HL130D
KT63
KT66 USA 3,95
KT66 GEC 17.50
KT66 Sp Yellow
бро! 19.50
KT6? 9.00
КТ77 Gold Lion
10.95
КТВ! 7.00
КТ88 USA 10.95
KT88 G Lion
18.95
KTW61 2.50
KTW62 2.50
KTW63 2,00
KT263 2.50
L102/2K 6.95
1102/2 1200
187-20 95.00
(598 6.95
M502A 60.00
537A 60.00
M5143 155.00
M8079 5.00
мвов? 7.50
M8083 3.25
M899 7.50
M8096 3.00
M6998 5.50
"8099 5.00
M8100 5.50
M8136 7.00
M8137 7.95
M6161 6.50
M8162 5.50
M8163 5.50
м8190 4.50
MP195 6.50
M6196 5.50
M8204 5.50
Me223 4.50
MB224 2.00
M6225 3.95
MEI401 29.50
ME1402 29.50
ME1501 14.00
MH4 3.50
MHL6 4.00
ма 4.50
MP25 195.00
MS4B 5.50
MU14 3.50
MZ1-100 125.00
N37 12.50
N78 9.85
OA2 0.85
OA2WA 2.50
OAR 2.50
0.85
OB2WA 2.50
Oc2 2.50
ОСЗ 1.50
OD 1.70
OMA 1.00
OM58 3.00
OM6 1.75
ORP43 2.50
ORPSO 3.95
P61 2.50
Р41 2.50
PABCB 0.75
PCB6 0.75
0.75
PC92 3.50
PC97 1.10
1.10
PC900 125
PCC84 0.40
РСС85 0.55
PCC88 0.70
РССВ9 0.70
РСС189 0.70
PCCS05 0.70
PCC806 0.80
PCE82 0.80
PCF80 0.65
PCF82 0.60
PCF84 0.65
PCF86 1.20
PCF87 0.40
PCF200 1.80
PCF201 1.80
РСЕВОО 0.40
PCFeO1 1,35
PCF 602 0.60
PCF805 1.25
PCF806 1.00
PCFBOB 125
PCH200 1.50
PCL82 0.85
PCL83 2.50
PCL84 0.75
PCL85 0.80
PCLB6 0.85
PCL800 0.80
PCL805 0.90
PE1-100 69.00
PEN25 2.00
PENSODD 2.50
PEN45 3.00
PEN45DD 3.00
PEN46 2.00
PE06-40N 42.00
PFL200 0.95
2.50
Р\ 36 1.75
Р\ 38 1.50
РІВ! 0.72
РАВТА 0.72
PL82 0.60
PLE: 0.52
РІ84 0.78
PLES 1.00
Р\ 95 2.95
PL302 1.00
PL345 12.50
PL500 1.10
Р 504 1.15
PL508 1.75
PL509 4.85
PL519 4.95
PL802T 350
Р\820 2.95
Рі 5557 29.50
PY32 0.60
PY33 0.50
Pyar 0.70
РҮВ2 070
РҮВЗ 0.70
РҮВВ 0.65
PY500A 1.95
PY800 0.79
PY801 9.79
083-300 54.95
083-1750 139.50
085-3500 595.00
QE03-10 4.95
QE08-200 145.00
OF 40 65.00
ОР25 1.00
00Е02-5 19.50
ООЕОЗ-12 7.95
00Е03-20 35.00
00Е06-40 45.00
ООМ02-6 19.50
ООМ03-10 5.50
ООУ03-10
Mullard 15.00
00\03 25.00
00\06-40А
Mullard 4500
QOVO07.50 63.50
00203-20 42.50
0$7520 1.50
QS75/40 3.00
0592/10 5.00
059510 а.85
QS106/45 4.00
05150715 6.95
0515030 1.15
0515045 7.00
051200 3.95
051202 3.95
051203 4.15
051205 3.95
051206 1.05
051207 0.90
051208 0.90
051209 3.15
051210 1.50
051211 1.50
051212 3.20
ELECTRONICS & WIRELESS WORLD
Qs1213 5.00
OS1215 2.10
QS1218 5.00
QU37 9.50
Qvo03-12 5.75
Qvos-25 2.50
Qvoe 29.50
0\08-100 145.00
Qv2-2500 45.00
QY3-125 65.00
ОҮ4.250 70.00
Оү4-400 76.00
Rio 4.00
R16 12.00
А" 1.50
НВ 2.50
R19 2.50
R21 1.20
91169 55.00
AGI-125 4.95
RGt-240A 14.50
RG3-250A 3.50
RG3-1250A 35.00
RK2K25 6250
RK-208 12.00
RL16 1.50
RPLIG 12.00
ЯРУ! 3 2.50
RPY43 2.50
RPY82 2.50
RR3-250 15.00
RR3-1250 35.00
RS613 45.00
RS68 54.95
RSS688 5215
56Е17 5.95
S6F33 28.95
S11E12 38.00
A30/2K 12.00
S1041K 10.00
S1091K 15.00
5130 5.59
5130Р 5.95
5.00
182.300 4500
183-2000 395.00
TDt-100A 25.00
1003-02 35.00
703-12 4.00
тооз 5.50
ТР25 1.50
TSP4 7.00
пи 1.50
TT21! 45.00
TT22 45.00
TT100 69.00
TTR-31!MR 65.00
TY2-125A 85.00
түл 400 85.00
TY6.600W
365.00
Tys2 375.00
U18 2.75
U19 11.95
U24 2.00
U25 0.90
U26 0.90
u37 9.00
ual 6.95
uso 2.00
u82 3.00
u19 0.70
U192 1.00
Ur93 0.65
U251 1.00
UBO! 0.75
UABCBO 065
UAF42 1,00
UBFBO 0.60
2.25
4.50
4.00
UBL21 1.75
ucg2 1.20
UCCBA 0.70
UCC8S 0.60
UCF80 1.00
UCH21 1.20
UCH41 2.50
UCH42 2.50
UCHB1 1.00
UCL82 1.75
UCL83 2.50
UF4t 1.15
UF42 1.15
ЧЕВО 1.75
UF85 1.20
UF89 2.00
Ut 41 5.50
UL44 3.50
UL84 1.50
utes 0.85
Uu5 3.50
Uu7 8.00
uug 9.00
ЧҮ41 3.50
Uv85 0.70
V235A/1K 250.00
V238A/1K 295 00
V246A/2K 315.00
V2406/1K 225.00
V241C/1K 195.00
\339 3.50
Va53 12.00
VLS631 10.95
vP4B 4.50
VP133 2.00
VR75-30 3.00
VR101 2.00
V105/30 1.50
VR150/30 1.15
МТ52 2.50
vu29 4.50
vu3as 1.50
w21 4.50
№77 5.00
w729 1.00
W739 1.50
x24 4.50
X66/X65 4.95
X76M 1:95
1.50
хС25 0.50
XFW47 1.50
XFW50 1.50
XG1 00 75.00
XGS 22.50
XL628FT 7.50
XNP1 2.50
XR1-1600A 49.50
XR 1:3200A 79.50
XR1-6400A
149.50
YX 25.00
Y65 6.95
YD1100 75.00
YJ1060 26500
YL102¢ 42.50
YL1060 195.00
YL107 195.00
YL1071 195.00
YL1290 65.00
77? 1.20
2302С 12.00
7359 9.00
2505 15.00
2520M 4.00
Z521M 8.00
27000 3.00
7749 0.60
7759 19.85
28030 18 95
ZA100" 12,50
ZA1001 1.50
201005 8.00
ZM1020 6.00
7M1021 8.00
241023 7.95
ZM1041 14.00
ZM1082 9.00
ZM1064 10.00
ZM1177 9.00
ZM1202 55.00
ZM1263 4.00
822 10.00
2K25 35.00
2K 25 Raytheon
75.00
2K26 95.00
2K29 250.00
2к4е 140.00
2K56 250.00
Х?А 5.00
34/1078 42.00
3A/108A 9.00
34/1998 11.00
3A/110B 12.00
ЗА/141К — 11.50
3A/147J 7.50
10.00
395
3.95
1.10
4.50
0.95
3.35
1100.00
4CX250B
49.00
4CX250B EIMAC
4D:
4CX250BN 75.00
4CX250K EIMA:
95.00
4CX125C EIMAC
4CX350A
4CX350F
4XC 15008
125.00
95.00
79.50
5A152M 9.00
5A163K 1000
5A170K 6.25
A-180M 9.00
5А-206К 10.00
5АМ8 2.15
5АМВ 1.20
5AR4 2.00
SAUA 1.50
58 110м 10.00
5B.254M 14.50
58.255M 19.50
5B-256M 15.00
5B.257M 15.00
5B-258M 14.50
5С22 125.00
SCLBA 2.50
5J180E 2950.00
5RAGB 5.50
SR4GY 4.95
5T4 5.95
546 2.95
5U4GB 450
5V4G 1.50
5Y3GT 1.95
5Z4GT 50
6/3012 0.70
6А/203к 9.00
6A7 4.95
6A8G 50
6ACT 2.00
64G5 1.50
6AG7 1.95
6AH6 2.50
SAJA 2.00
6AJ7 2.00
бАК5 1.95
6AK6 2.50
6AL5 0.60
6AM4 3.25
6AMS 600
6AM6 1.95
6ANS 4.50
6ANBA 3.50
6AQ5 1.75
6AQ8 085
6AR5 5.95
6ARB 3.95
6А55 1.50
6AS6 2.50
6AS7G 4.50
6AT6 0.75
бАТВ 75
6AU4 2.00
6AU5GT 450
6AU6 0.95
6AV6 0.75
6AWBA 2.50
бАХАСТ 1.95
6AY3B 1.95
6AZ8 450
687 2.80
688 150
6810 1.95
6ВАб 0.95
6BA7 4.50
6BABA 3.50
6BE6 0 95
68666 3.06
6BH6 1.95
6BHB 1.50
6BJ6 150
6BK4 4.00
6BK7A 1.95
6816 85.00
6818 1.15
68M6 115.00
6BM& 0.54
684 1.65
6846 1.65
6847 4,59
6BN8 3.95
6805 0.75
6807A 0.72
6BL7GTA 3.95
68R5
6897
6898
6BRBA
68S7
68wa4
68W6
68w7
68\/8
68х6
68X7GT
6826
6827
604
6C
6С6
6C8G
ec
6C18
6CA4
6CA7
ecas
6CB6
ENTER 36 ON REPLY CARD
6.95
3.95
6CL6 325
6CLBA 1.50
6CNS 1.60
6CM7 2.95
6CS6 0.75
6CS7 0.95
6Cwa 6.50
606 2.50
6066 2.35
60.8 0.95
60к6 1.50
5.95
60068 2.50
6DT6A 1.50
60/4 2.15
6Е5 3.95
6EA4 4.95
6EA7 2.50
6EAB 2.50
6ЕВ8 175
6EMS 2.50
6EM7 2.50
6EU7 1.95
6EUB 1.75
6EV7 2.95
6EWS 2.95
6EW7 4.50
6F! 2.00
6Е5 4.95
6F6 2.50
6F6G 2.00
550
6F12 1.50
6F13 3.00
6F14 1.00
6F17 2.75
6F21 2.50
6F23 0.60
6F24 1.25
6F25 1.25
6F28 1.25
6F32 1.25
6F33 17.00
6FG5 1.95
6FQ7 2.95
6566 5.50
6GE5 3.95
6GHBA 0.80
6GK5 1.50
6GK6 1.95
6GM6 2.65
6GS7 2.15
6GV7 2.50
6Gw6 2.50
6Gwe 250
6GY5 3.95
6H1 9.50
6H3N 2.50
6H6 1.95
6H6GT 1.95
6HF5 $.50
6НЕВ 2.50
6HS6 4.95
6.4 2.15
6J4WA 3.15
695 2.50
6J6 2.00
67 4.15
6JB6A 4.50
6JE6C 6.50
6JU8 2.50
6JS6C 6.50
6576 4.15
6K7G 2.00
6K8G 300
6KD6 6.50
6KMB8 2.50
6KT8 2.95
6.1 2.50
eL'5 3.15
6L19 3.95
6L6GC 295
6L6GC(GE) 5.75
6L6GT 1.95
61020 1.15
eLF6 7.50
6L6GAY 5.50
SYLVANIA
618 2.50
6.06 6.50
6Q7GT 1.20
687G 3.15
654A 1.50
6SA7GT 1.35
6SC7 1.50
6567 2.50
6SH7 1.35
6SJ7GT 1.20
6SK7 1.35
6SK7GT 1.35
6SL7GT 0.85
6SN7GT 1,35
6SQ7 1.35
6557 1.95
6U4GT 1.75
6U6WA 3.50
608 4.15
6UBA 1.50
AUDIO TAPE HEADS
MONO HEAD
AUTO REVERSE
STEREO HEAD
VALVE AND CRT BASES
3.95
5.50
0.25
0.25
1.50
0.70
0.35
› 0.60
0.75
0.20
0.50
3.00
0.35
SK406
SK410
VALVE CANS
87 and Bs 0.35
ANODE CAPS
6V6G 1.25
6veGT 1.50
6vGG 1.00
6Y6G 3.95
6X2N 1.00
6x4 1.50
645GT 1.00
6x5GTY 1.00
6x88 225
7A6 4.50
7A7 2.00
7AD7 1.75
7AU7 1.50
786 3.50
787 2.50
75 3.50
7C6 2.50
7E7 2.50
7н7 3.50
737 5.50
7YA 2.50
888 2.50
8810 2.50
8805 1.95
BFQ7 1.95
1002 1.25
10DE7 2.50
10EW7 2.95
10F 1 0.75
10GK6 1.95
10P14 2.50
10P 18 0.78
10.012 0.65
11E2R 45.00
1163 55.00
1193 5.50
12Аб 3.95
12AD6 1.50
12AH7GT 4.95
12AL5 1.00
12AT6 1.25
12AT7 145
12ATTWA 2.50
12AU6 1.50
12AU7 0.65
12AV6 1.95
12AV7 2.50
12AX7 0.65
12AX73 7.95
12АХ7 ЧА 250
12AY7 3.95
12A77A 1.95
12B4A 4.50
12ВАб 1.50
128Е6 1.95
128H7A 2.50
12816 1.75
12ВҮ7А 2.75
12C8 2.50
2CAS 1.95
12СХЕ 1.20
120 3.50
120WaA 3.50
12Е 19.50
12Е 14 38.00
12GN 3.95
12HG 4.50
12HG7A 4.50
12J5GT 3.95
127767 3.50
12328 2.95
12к5 1.95
12K7GT 1.50
1.95
12SA7GT 1.95
1256 4.75
12SH 1.95
12SK 1.95
25? 1.50
1250761 1.95
12SN7GT 1.85
12X4 1.95
1257 4.50
1303 3.20
1307 3.20
1309 3.20
13DE? 2.50
13097 2.95
13Е 445.00
13EN7 3.50
'6GYs 2.95
178E3 2.50
17DW4A 2.95
17Ew8 0.95
17328 4.50
1803 6.00
18685 3.50
19AC5 3.50
19AUAGT 2.50
1966 9.00
1963 17.00
энг 35.00
19H4R 25.00
1915 33.50
1906 9.00
20A2 10.50
2007 0.70
20.25 7.95
2001 0.95
20P% 0.55
20Р: 0.60
20Р4 1.95
20Р5 1.15
TELEX
966371
TOS—PM
404A
927 15.00
1927 25.00
4687A 9.50
4212E 250.00
4313C 4.00
43280 9.00
29KQ6 6.50 5636 5.50
30017 0.40 5642 9.50
30C 18 1.48 5651 250
3F5 0.95 5654 1.95
3oFL1 1.00 5663 1.95
30FL2 1.35 5670 3.25
0.95 5672 4.50
1.10
1.25
0.45
0.60
30t 1 0.60
30PAMR — *.00
30P12 1.00
30P 18 0.60
30Р19 1.00
ЗОР 1 2.50
ЗОР 13 0.60
ЗОР 14 1.75
31JS6C 5.50
33A/158M 19.50
35A 4.50
35L6GT 2.00
3523 1.85
38HE7 4.50
40KD6 5.50
42 6.95
47 6.00
50А5 1.50
socs 0.95
50СО6С 1.15
SOEHS 1.50
50JY6 2.95
52KU 2.00
53CG 15.00
615РТ 4.50
7581 3.50
75С1 2.50
6550 ВСА 15.00
6688 6.50
6870 11.50
6887 9.50
68838 9.95
6973 5.95
7025 2.50
7027А 4.50
OVER 4 MILLION VALVES IN STOCK
4,000 + Different Types
Please enquire for types not listed
Specialty selected and matched valves.
available on request
CALLERS WELCOME
OPEN MON-THUR 9AM-5.30PM
FRI9AM-5.00PM
*24-HOUR ANSWERPHONE
SERVICE"
ACCESS & BARCLAYCARD
PHONE ORDERS WELCOME
UK ORDERS P&P £1
PLEASE ADD 15% VAT
EXPORT ORDERS WELCOME
CARRIAGE AT COST
PLEASE SEND YOUR
ENQUIRIES FOR SPECIAL
QUOTATIONS FOR LARGE
REQUIREMENTS
449
Airmac
One of our readers, who was
associated with the firm Airmec
(not Airmac) telephoned to tell
us that the receiver taken to
Poland by Mr Bar (February let-
ters) was probably made by that
company, which was a subsidiary
of Radio and Television Trust.
They exported sets under the
Airmec name, but used the name
Philco, under licence from
America, for export. The Airmec
name is no longer used.
Our informant still possesses a
1947-vintage Airmec receiver,
which works well, having needed
only a replacement electrolytic
in 40 years of service. – Ed.
Police radio
The article by Jack Davies (Janu-
ary 1987 issue), brought back a
flood of memories as I was one of
the ETE/Mullard/Philips team
that installed and commissioned
the synchronous f.m. system for
the Lancashire police.
The system was based on the
Philips IGO (impulse governed
oscillator) concept used for fre-
quency and audio locking of a.m.
broadcast transmitters operating
on the same frequency. The de-
sign and development of the sys-
tem started in 1947 when Philips
Electrical was approached by the
late Inspector Frank Gee who
had read a paper describing the
Philips IGO work. Philips Trans-
mission Equipment Ltd., in
Balham did the initial study for
the Lancashire police. The de-
velopment work was handled by
a small group of engineers led by
the late Christopher Bailey work-
ing in a makeshift laboratory in a
disused laundry in Wandsworth.
Frank Gee and Eric Jones, then
the commercial manager of the
Mullard/Philips communica-
tions activities, were the driving
force behind the project. Many of
the team in Wandsworth and
Lancashire were licenced
amateurs.
Jack has a good memory as,
apart from one or two minor
details, his description of the
system is correct. The original
two-station arrangement at Bil-
linge and Barnacre was a crude
lash-up to prove the system. A
preset variable delay was in-
cluded to equalise the different
path lengths between the wire-
450
EEDBACK
linked base station and the radio- ] mon knowledge and has been
linked slave transmitter. After
these intitial tests a more sub-
stantial set of prototypes was
produced for installation in the
Force HQ, Hutton. This was also
a single-frequency system and |
was designed to work with up to
six remote slave transmitters.
Initially only four slaves were
used, as it was found that they
provided full coverage of the
county.
The updated master unit used
a more sophisticated variable-
lock system to provide the neces-
sary audio delays and the fre-
quency off-set facility mentioned
by Jack. It was never intended
that those prototypes would have
an extended life, and develop-
ment work continued both in
Lancashire and at Wandsworth
to provide multi-channel opera-
tion and many other facilities
that were likely to be required for
future expansion of the system.
From the experience gained
with the Lancashire units, Gee
and Bailey produced a compre-
hensive specification for a set of
production equipment to replace
the prototypes. In 1950 Mullard
had formed a new company Mul-
lard Equipment Ltd, (later MEL)
which merged with ETE. A
Mobile Radio Division of MEL
was established at the same time
under Christopher Bailey and
took over the responsibility for
the Lancashire units. In early
1953 contracts for the replace-
ment production system were
being negotiated between Lan-
cashire and Mullard when. for
policy reasons, Mullard decided
to discontinue v.h.f. mobile
radio activities. As reported, the
Lancashire Police Wireless De-
partment continued to use and
simplify the system to provide
greater reliability and ease of
servicing before it was finally
closed down in 1968.
R.L. Glaisher (G6LX)
Croydon
Planck and the
fine structure
It is unfortunate that the deep
| relationship that is ‘thought’ to
exist between Planck's constant,
h and the so called atomic fine
structure constant, a as was sug-
gested by Ove Tedenstig (EWW
Feb. 1987) is not really new.
Already this relationship is com-
well established since the early
development days of quantum
physics. Most general text books
on the subject show that « is
given by
= “ch (1)
However. the classical rest
radius of the electron r, is de-
rived from the following:
2
е
2
= тїс
(2)
<
^
where e is the charge of the
electron and m, is its rest mass.
Therefore, substituting for е т
(1) and re-arranging results in
h = 22m,r.c(a-1)
This leads us nowhere new ex-
cept, perhaps, to that of compli-
cating furthermore the subject.
M. Zaman Akil
Regent's Park
London
Insanity
Mr W. Scott really ought to
straighten out his wife for talk-
ing about the insanity of en-
gineers (Feedback, January,
1987).
All these standards are in-
flicted on us by desk-pilots with a
lack of imagination and arro-
gance that | associate with civil
servants, despite Bernard Jones
having taken me to task for
calling them such (November.
1986).
The most recent of the mains
wiring codes is so baífling and
silly that it has earned a send-up
in Punch (30th July, 1986. p.29).
Shortly after the end of the
war, a committee of intelligent
men (obviously engineers) sat at
Whitley and worked out a colour
code for circuit wiring in RNSS
equipment. In 1951. when a sci-
entific assistant, | was told to
clear out a lot of files and saw the
word "secret", which naturally
persuaded me to look into them.
1 found the Whitley code and
| have used it ever since in every-
| thing | have built, also putting
tiny numbers beside every wire
in my diagrams to indicate its
| colour in accordance with the
resistor colour code. No one
| smote me with the Official Sec-
rets Act, even after | sent the
code to WW (May, 1960, p.256).
Yellow. Signal; Red. Steady
positive potential; Orange. signal
at a positive potential; Blue,
steady negative potential; Green,
signal at a negative potential;
Black, earth; Brown, signal at
earth potential; White, pure a.c.
(any frequency); Mauve, any-
thing needing distinguishing
from the above.
Although one colour some-
how got lost in transmission
(grey) the meaning of it could be
deduced from the other nine.
This was the only code | have
ever seen that was able to make
the transition from valves to
transistor circuitry unaltered.
It may not have been the ori-
ginal intention, but from this
code comes naturally the only
three colours for wiring a mains
plug that will offer protection to
persons handicapped by all
known types of colour-blindness:
white live
£rey neutral
black earth
Acolour code for mains wiring
that can be safely used under the
light of sodium lamps calls for a
level of intelligence that I fear
may prevent it from ever becom-
ingan officially ratified standard.
John C. Rudge
Harlington
Middlesex
Hands-on
Engineers
Regarding 'Hands-on En-
gineers', by К.Е. Young, there
cannot be many engineers who
will disagree with his thesis that
"engineers should have had leng-
thy shop-floor experience with
working plant and equipment".
But what about the corollary that
| they should continue to have
that experience no matter what
level or sharpness of speciality
they attain? Maybe, like military
reservists, they should be called
up for their annual refreshment.
The element of snobbery
should not be overlooked, either.
Could anything be more absurb
than. for example, the sight of an
Experimental Officer walking
alongside the quite lightly-
loaded trolley of instruments
being pushed by a Shopman
(new-style ‘labourer’). And what
about the Technician's (new-
style 'craftsmen') mate — possibly
also styled Shopman - who is
condemned by fortuitous cultu-
ral and economic circumstances
to be forever a fetcher and car-
ELECTRONICS & WIRELESS WORLD
rier? And then there is the pathe-
tic reluctance of ‘qualified’ en-
gineers to seek help from their
supposed juniors, because that
would be demeaning; or to pay
adequate attention to their sug-
gestions, of which the most
damaging variation is the ‘not-
invented-here' syndrome.
Service in a warship in war-
time is the place to experience
the results and the sometimes
fatal consequences of these atti-
tudes and practices: doubtless
other Services could claim simi-
lar suitability. And not only war-
time, for I recall vividly the pre-
war loss of the new submarine
HMS THETIS with most of its
crew and some of its builders,
within Liverpool docks, because
a test-cock on a torpedo-tube
inner door was blocked with
paint; and because the Davis
escape apparatus would not work
unless the ship was on an even
keel.
I recall, too, my own weaknes-
ses arising from excessive 'chalk-
and-talk' learning — partly, it
must be conceded. from wartime
shortages of time and equipment
- and from my unscientific
jumping to conclusions without
experimental verification of
them. For'example: having abso-
lutely no hands-on experience of
the use and care of lead-acid (or
any) batteries, | used to keep а
gyro-compass alarm battery
trickle-charged by the ingenious
device of a torch bulb connected
between the charging terminal
and the battery, when the alarm
system was in use at sea. | could
tell that the battery was fully
charged by the colours of the
positive and negative plates in
the glass battery case. However,
when the alarm system was cal-
led for when а gyro-compass
broke down, the battery would
not sound the heavy-current
alarm bell though, fortunately, it |
was able to light a red warning
lamp on the bridge of the main
escort vessel on the Russian con-
voy. But (and Гат not sure of the
relevance of this to my argu-
ment) nohody recognized it as an
alarm! | was called from ту
hammock to "get this damned
red light switched off’: it was
irritating the Officer-of-the-
Watch! In direct contradiction to
Murphy's Law, it was the spare
compass that had broken down.
К was 20 vears later that I
learned that lead-acid batteries
cannot be continuously trickle-
EEDBACK
charged, or regularly topped-up
after only slight use, but must be
occasionally discharged fully if
they are to retain their capacity.
It seemed that the battery manu-
facturer learned this at the same
time as I did, for his engineers
had approved my charging
arrangements. Their alarm
sounded when a large number of
expensive teak-encased auto-
mobile batteries were returned
under guarantee within only a
few months. It was another 15
years or so before research had
perfected lead-acid portable bat-
teries that could be continuously
trickle-charged.
Very likely the relatively
‘junior’ engineering grades who
normally looked after the ship's
Low Power System batteries
would have made a better job
than | did of ‘my’ alarm batteries.
My point is that I thought | knew
about them because | had been
taught about them. You have to
learn through your finger ends
and through the consequences of
your mistakes and incorrect
assumptions — which necessarily
entails lots of opportunities to
make mistakes.
Finally, in supporting R.E.
Young's plea that a "managing
engineer s" career demands that
at least the classical seven years
should be spent unJer appren-
ticeship conditions", | believe
that Sir George Stapledon was
right to urge the value of every-
one doing an apprenticeship in
some form of craft. Apart from its
value in inculcating a real feel for
material and process, it would, I
believe, reduce the appalling
trend towards full-time con-
sumerism that is making most of
us little different from the unfor-
tunate geese who are forcibly
stuffed to make pate de foie gras.
Ronald Gill
Allestree
Derby
Relativity
Although I havent read М.А.
Scott Murray's relativity article
in your December issue, I have
followed the resulting corres-
pondence with some interest.
There is a fundamental error
in everybody's thinking here, as
to why the Earth is designed as
an oblate spheroid. As every
schoolboy knows. the Earth is
this shape due to the constant
pressure applied by the wing
ELECTRONICS & WIRELESS WORLD
nuts situated at each polar cap. À
quick glance at any model of the
Earth on our readers desks will
confirm this fact.
R. Thomas
Dorking
Surrey
The main thrust of Dr Murray's
interesting article "If you want to
tell the time ..." (ЕФИМ, Dec.
1986) hinges on the statement in
the last sentence in the box.
However he does not tell us why
we must “not identify" the two
terms with each other. Nor is
there any reason why we should
at first sight, since although STR
is recognised to be а special case
of СТК, so that any STR effect
must necessarily be a GTR effect
as well, the opposite is by no
means always true. We may have
one of these "one-way" cases
here.
It seems hardly necessary to
follow in detail how Einstein
reaches his conclusion of a rate-
change of Vev?/c? seconds per
second in his 1905 paper. He
uses the well-known device of
treating a curved path as a suc-
cession of instantaneous linear
paths in order to apply a linear
equation to a curved case. We
should now consider the situa-
tion from the viewpoint of the
accelerated, GTR case.
The moving clock is con-
tinuously accelerated towards
the fixed clock, with an accelera-
tion of wr. GTR tells us that a
clock under acceleration has its
rate altered by а factor which
equals its "acceleration poten-
tial" divided by c^. In this case,
the acceleration potential of the
moving clock relative to the fixed
one will be seen to be:
R
Potential — [^ar = W R”
0
(since when К = 0, P = 0 and the
constant of integration therefore
|^ 0). We now have:
Rate change = №? В?/с?
= Yoy"/e?
where у = мВ.
We have to conclude that far
from “not identifying” the two
terms with each other, we can-
not avoid it. They are the same
term, merely derived by different
routes. In my opinion, Dr Mur-
ray's argument therefore fails.
In passing. | think that this
also finally disposes of the "Ding-
le Question". Viewed from the
GTR standpoint, one clock is
under acceleration and the other
is not, so there was never any
symmetry in the situation, and
hence no question.
On a quite different tack, | am
most grateful to Prof. Waldron
for his very authoritative over-
view of the present ‘state of play’
on the second postulate (Feed-
back, December. 1986). It seems
that | can go on breathing for a
little while yet, hoping for an
explanation of split spectra to
gallop to the rescue, because in
my simple-minded fashion I have
always had the idea that, since it
appears to describe precisely the
characteristics light possesses in
the aether, its disproof would not
only scupper the theory of re-
lativity, but blow a nasty hole in
the only other theory І know
about as well. Of course, I will
still have to come to some sort of
terms with the ‘resonance’
theory Dr Aspden espouses
(Feedback, Nov. 1986). In order
to get the arithmetic right, I find
that his c’ (>c) has got to be the
speed relative to the aether. This
means that we have an entirely
new aether to deal with, capable
of supporting an infinite number
of different light-speeds. | con-
fess that my mind boggles madly
when try to define its character-
istics. It mucks up relativity -
and everything else — with a
vengeance!
Alan Watson
Pollenca
Mallorca
Your correspondent Lee Coe
(January 1987) seems not to be
aware of the relativistic Doppler
effect, the theory of which may
be found in any undergraduate
physics textbook.
According to the relativistic
model, the Doppler effect arises
from the Lorentz contraction of
the space and time coordinates,
and not from a change in wave
propagation velocity as is
assumed in the classical model.
The classical and relativistic
results differ by the Lorentz
factor
М1 — vc
and for ordinary speeds the re-
sults are virtually identical.
H. Pursey
New Malden
Surrey
451
OMPUTER
HOT LINE DATA BASE
x DISTEL 1
{ Тһе ORIGINAL FREE OF CHARGE dial up data?
* base. Buy, browse or place YOUR OWN AD for;
* goods or services to sell. 1000's of stock items, °
* Spares and one off bargains. Updated daily.
$ ONLINE NOW. CCITT, 8 bit word. no parity.
e For 300 baud modems call 01-679 1888
For 1200-75 baud modems call 01-679 6183
*6906600099009099600060000205^5060600060000099
FREE only £29.95 it becomes a SUPERB
HIGH QUALITY * COLOUR * TV SET
Thefabulous TELEBOX an INVALUABLE MUST forthe owner of
ANY video monitor with a composite input. colouror monochrome
Made by a major UK Ca as a TOP QUALITY, stand alone UHF
tuner and costing OVER £75 to manufacture. this opportunity to
give your monitor a DUAL FUNCTION must not be missed! The
ELEBOX consists of a compact stylish two tone charcoal
moulded case. Containing ALL electronics tuner. power supply etc
to simply plug in and convert your previously dedicated computer
monitor into a HIGH QUALITY COLOUR TV SET. giving a real
benefit to ALL the family! Don't worry if your monitor doesn't have
sound- THE TELEBOX even has an inlegral4 watt audio amplifier
tor driving an external speaker. PLUS an auxilary output lor Superb
Quality television sound via your headphones or HI FI system etc.
Other features include. Compact dimensions of only 15.75 wx
75 9х3.5 h latest technology. BRITISH manulacture, fully «
tuneable7 channel push button tuner, Auto АСС circuit, SAW filter.
LED status indicator. fully isolated 240v AC power supply for tota
safety. Mains ON-OFF switch etc. Many other uses
LIMITED QUANTITY - DON'T MISS THIS OFFER!!!
ONLY £29.95 OR £24.95 if purchased with ANY of our
video monitOrs suppied BRAND NEW with full instructions and 2 YEAR
warranty. Post and packing 3.50 "When used with colour crt
COLOUR & MONOCHROME
MONITO
'SYSTEM ALPHA' 14 COLOUR MULTI INPUT MONITOR
Made by the famous REDIFFUSION Co. for their own professional computer
System this monitor has ali the features to suit your immediate and future
requirements. Two video inputs. RGB and PAL Composite Video. allow direct
Connection to BBC/IBM and most other makes of micro computers or VCR s
including our very own TELEBOX An internal speaker and audio amp may be
Connected to computer or VCR for superior sound quality. Many other features
PIL tube, Matching BBC case colour, Major controls on front panel Separate
Contrast and Brightness - even іп RGB mode Separate Colour and audio
controls for Composite Video input, BNC plug for composite input. 15 way D
plug for RGB input, modular construction etcetc
This Must Be ONE OF THE YEAR'S BEST BUYS. PC USER
Suoplied BRAND NEW and BOXED complete with DATA and 90
guarantee ONLY £159.00 as above ORIBM PC Version£165.00
5 Day'D skt £1.00, ВМС skt 75р BBC interface cabie £5.50
DECCA 80 16 COLOUR monitor. RGB input.
Little ог hardly used manufacturers surplus enables us to offer this specia
converted DEGCA RGB Colour Video TV Monitor at a super low price only
£99.00, a price for a colour monitor as yet unheard of! Our own interface
Safety modification and special 16 high definition PIL tube. coupled with the
DECCA BO series TV chassis give BO Column definition and quality found only
on monitors costing 3 TIMES OUR PRICE. The quality for the price has to be
Seen to be believed! Supplied complete and ready to plug direc! to a BBC
MICRO computer or any other system with a TTL RGB output Other features
are: internal speaker. modular construction, auto degaussing circuit, attractive
TEAK CASE compact dimensions only 52cm W x 34 H x 24 D. 90 day
puarantes Я used units are supplied in EXCELLENT condition.
NLY £99.00 + Carriage
DECCA 80, 16 COLOUR monitor. Composite video Input. Same as above
model but fitted with Composite Video input and audio amp юг COMPUTER
VCR or AUDIO VISUAL use ONLY £99.00 + Carr
RE DIFFUSION MARK 3, 20 COLOUR monitor. Fitted with standard 75 ohm
Composite video input and sound атр This large screen colour ТАП is ideal
for SCHOOLS, SHOPDS, DISCOS CLUBS and other AUDIO VISUAL apple
cations Supplied in AS NEW or little used condition ONLY £145.00 + Carr
BUDGET RANGE EX EQUIPMENT MONOCHROME video monitors.
All units are fully cased and set for 240v standard working with composite videc
inputs Units are pre tested and set up for ир to 80 column use Even when
MINOR screen burns exist - normal data displays are unaffected 30 day
guarantee
2 КСМ 320-1 B/W bandwidth input will display up to 132 x 25 lines £32.95
12 GREEN SCREEN version of КСМ 320-1 Only £39.95
9° KGM 324 GREEN SCREEN fully cased very compact unit Only £49.00
Carnage and insurance on all monitors £10.00
" 77 А LJ
) ‚ , 1.
GOULD OF443 enclosed. compact switch mode supply with DC regulated
Outputs of +5v w 55a, * 12v @ 0.5a, — 12v © О 1a and -23v © 002a Dim 18 x
11x6cm 110 or 240v input BRAND NEW only £16.95
GOULD G6-40A 5v 40 amp switch mode Supply NEW £130.00
AC-DC Linear PSU for DISK drive and SYSTEM applications Constructed on a
rugged ALLOY chassis to continuously supply fully regulated DC outputs of +5v
Your monitor from its computer! For
day
© З amps. —5v @ 0.6 amps апа +24v @ 5 amps Short circuit and очегм tage
protected 100 or 240v AC input Dim 28 x 125 x 7 cm NEW £49.94
Carriage on all PSU's £3.00
"ҮҮ ие ы
a j a Manufacturers BRAND NEW surplus
DEC LA34 L'ncoded keyboard with 67 quality goid plated switches оп X-Y
matrix - ideal micro conversions etc £24.95
AMKEY MPNK-114 Superb word processor chassis keyboard on single PCB
with 116 keys Many features such as On board Micra Single 5v rail full ASCII
coded character set with 31 function keys numeric keypad cursor pad
СУ and 9600 baud SERIAL TTL ASCII OUTPUT" Less than half price
У Only £69.00 with data Carnage on Keyboards £3.50
Double sided 40/80 track disk drives
CENTRONICS andsystem expansion ports andifthat’sn
B' disk drives either in double density or IBM format The
numeric keypad and text editing keys even its own integral microproces
USER programs eliminating” lost
a green ante glare etched screen with full swivel and tilt mov
2.2. user manuals and full 90 day guarantee Full d
PC2000 System
with CPM Etc
COST OVER £1400
WAREHOUS]
iy THE "ALLADINS' CAVE OF COMPUTER AND ELECTRONIC
Professional Business System
4 А cancelled export order and months o! negotiation enables us to offer this professional
PC СРМ system recently on sale at OVER £1400 ata SCOOP price just over the cost of
the two internal disk drives! Or less than the price of a dumb terminal
Not a toy. the BIG BROTHER of the EINSTIEN
PC2000 comprises a modern stylish three piece System with ALL the necessities for the
SMALL BUSINESS. INDUSTRIAL, EDUCATIONAL or HOBBYIST USER Used with
tne THOUSANDS of proven tested and available CPM software packages such as
WORDSTAR, FAST. DBASE2 etc
BE BEATEN
The central processor plinth contains the 64K, Z80A processor, DUAL TEAC 55Е 5'4
PSU, 4K of memory mapped screen RAM. disk controller RS232,
jot enougha ready to pluginto STANDARDB DRIVE portforupto FOUR
y. detachable keyboard features 32 user definable keys,
Sor which allows the main 280A to devote ALL its time to
character’ problems found on other machines The attractive, detachable 12° monitor combines
ement for maximum user comfort Supplied BRAND NEW with CPM
ata sheet and info on request
PC2000 Business System with CPM
AST Sales and
Purchase ledger. supports up to
9000 Accounts. VAT etc
COST OVER £1700
y £499
Carriage & Insurance
1Mb per drive)
and Ready to Run
SURPLUS SPECIALS ON
PRESTEL - VIEWDATA - TELEX
PLESSEY VUTEL. ultra mpact unit, shghtly larger
than telephone features A STANDARD ОТМЕ
TELEPHONE (топе dial with 5 CRT montor and
integral modem etc for direct connection to PRESTEL
VIEWDATA etc Designed to sel! to the EXECUTIVE at
Over £60 Our pr BRAND NEW AND BOXED a:
y £99.00
DECCAFAX VP1 complete Professio PRESTEL
Syste Simline desk top unit Ntaining Moder
Numeric keypad CP PSU etc Connects direct 1
Standard B lour monitor Many other features
nciude Printer output. Full keyboard input. Cassette
por! ес BRAND NEW with DATA А FRACTION OF
COST only £55.00
ALPHATANTEL. Very compact unit with integral FULL
ALPHA NUMERIC keyboard. Just add a domestic TV
receiver and you have a superb PRESTEL system and
va PRESTEL the cheapest TELEX service be
found" Many features CENTRONICS Printer output
Memory dia etc Supplied complete with data and
DIY mod tor RGB or Composite video outputs AS
NEW only £125.00
Post and packing on ali PRESTEL units £8 50
EX-STOCK INTEGRATED CIRCUITS
4164 200 ns D RAMS 9 tor £11 4116 ns
£150 2112 £10.00 2114 £250 2102 £2.00
6116 £2 50 EPROMS 2716 £450 2732 £3.00
2764 £4.95 27128 £550 6800 £2 50 6821 £1
68A09 £8 6BBO9 £10 8085A £5.50 8086 £15
8088 £8 NEC765 £8 WD2793 £28 8202А
£22 8251 £7 8748 £15 280А DART £650
280A CPU £2.00. Thousands of IC's EX STOCK
send SAE for list
| DISK DRIVES |
Japanese 5% half height. BO track double sided disk
drives by TEAC. CANON TOSHIBA etc
Sold as NEw with 90 day guarantee ONLY £85.00
TEC FB-503 Double sided HH 40 ТАК NEW £75.00
SUGART SA400 SS FH 35 ТАК £55.00
SIEMENS FDD100 SS FH 40 ТАК £65.00
Carriage on5% drives £5.50
Brand NEW metal 5'« DISK CASES with interna! PSU.
OSKC1 for 2 HH or 1 FH drive £29.95 +pp £4.00
DSKC 2 for 1 HH drive £22.95 +pp £3.50
DKSC 3 As DSK1 LESS PSU £12.95 +pp £2.50
OSKC 4 As DSK2 LESS PSU £10.95 +pp £2.00
8 ІВМ format TESTED EX EQUIPMENT.
SHUGART 800/801 SS £175.00 +pp £8.50
SHUGART 851 DS £250.00 +pp £8.50
TWIN SHUGART 851 's2 Mb total capacity in smart case.
complete with PSU etc £595.00
MITSUBISHI M2894-63 8 DS1 Mb equiv to SHUGART
SABSOR. BRAND NEW at £275.00 +рр £8.50
ОУЗАМ 8 Alignment disk £29.00 + pp£1.00
Various disk drive PSU s Ex Stock SEE PSU section.
HARD DISK DRIVES
DRE/DIABLO Series 30 2.5 Mb front toad £525.00
Exchangeable version £295.00. ME3029 PSU £95.00
DIABLO 44/ DRE4000A, B 5+5 Mb from £750.00
| СОС HAWK 5+5 Mb£795.00. CDC9762 80 Mb RMO3
etc £2500.00.
PERTEC 03422 5+5 Mb £495.00
RODIME 5'4' Winchesters ex-stock from £150 CALL
Clearance items- 5010 as seen - No guarantee
ICL 2314 BRAND NEW 14" Mb Removable pack hard
disk drive. cost over £2000 with дааа ONLY £99.00
ВАЗЕ 6172 8. 23Mb Winchesters £199.00
Unless stated ай drives are refurbished with 90 day
guarantee Many other drives and spares in stock - call
sales office for details
All prices quoted are for U.K Mainland, paid cash with order in Pounds Sterling PLUS VAT Minimum order value
Minimum Credit Card order£ 10.00. Minimum BONAFIDE account orders from Government Depts. Schools. Universities and
established companies £20.00. Where post and packing not indicated please ADD £1.00 + VAT. Warehouse open Mon-Fri
9.30-5.30. Sat 10.30-5.30. We reserve the right to change prices and specitications without notice. Trade, Bulk and Expon
32 Biggin Way, Upper Norwood, London SE19 3XF
Telephone 01-679 4414 Telex 894502 Data 01-679 1888
DON’T MISS THE CPM Deal
ultra slim92 ke
] [ ү : i , j 7
|
SPECIAL BULK PURCHASE of these compact. high
|RS232
1000's OF
BARGAINS
FOR CALLERS ^^
EQUIPMENT а
omputer. the DUAL PROCESSOR
the PC2000 specification. at our prices. CANNOT
PC 2000 Wordprocessor System
with CPM and TEC FP25 daisywheel
printer
NOW only £799
NMODEMS І
Join the communications revolution with our super
range ot DATA MODEMS, prices and specifications
to suit all applications and budgets
BRAND NEW State of the art products
DACOM 0512123 Multi standard 300-300, 1200:75
Auto answer etc. £268.00
DACOM DSL2123AQ Auto dial, smart modem with
multi standard AUTO SPEED detect. and data buffer
with flow contro! etc £365.00
DACOM DSL2123GT The CREAM of the intelligent
modems auto dia autc all index butfer
etc etc £498.00
Steebeck $81212 V22 1200 baud FULL DUPLEX
sync or async optional auto dia £465.00
TRANSDATA 307A Acoustic coupler 300 baud full
nly, RS232 interlace £49.00
Ex BRITISH TELECOM full spec, CCITT. ruggedised
bargain offers Soid TESTED with data Will work on
any MICRO or system with RS232 Interface.
MODEM 13A 300 baud unit опу 2^ high fits under
попе CALL mode onty £45.00.
ODEM 20-1. 75-1200 baud Compact unit for use
as subscriber end to PRESTEL. TELECOM GOLD,
MICRONET etc £39.95 +pp £6.50
MODEM 20-2 1200-75 baud Same as 20-1 but for
computer end £65.00 +pp £6.50
DATEL 2412. Made by SE Labs for BT this two part
unit is for synchronous data links at 1200 or 2400
baud using 2780/3780 protocol etc Many features
include 2 or 4 wire working, self test auto answer etc.
COST OVER £800. Our price ONLY £199 +pp £8.00
DATEL 4800, RACAL MPS4800 baud modem, EX
BT good working order, ONLY $295.00 +рр £8.00
SPECIAL OFFER
MODEM TG2393. Ex ВТ up to 1200 baud full
duplex 4 wire or half duplex over 2 wire line. ONLY
£85.00 PER PAIR +рр £10.00
For more information contact our Sales Office.
duplex originate
Peete ters
speed matrix printers, Built in Japan for the Hazeltine
Corporation this unit features quality construction
giving 100cps bidirectional. full pin addressable
graphics, 6 type fonts. up to 95 single sheet or
tractor paper handling. #5232 and CENTRONICS
parallel interface. Many other features BRAND NEW
and BOXED COST £420 Our price Only £199.00
RECHARG E BATTERIE.
Dry Fit MAINTENANCE FREE by Sonnenschein
& Yuasa
A300 07191315 12v 3Ah NEW £13.95
A300 07191312 6v 3Ah NEW £9.95
Equip £5.99
АЗОО 07191202 6-0-6v 1.8Ah TESTED Ex
DU TERMINALS
Standard VDU data entry terminals
at give away prices!!
QUME QVT108 отет product, state of the art
terminal with detachable keyboard. 12’ Green screen.
2 раде ВАМ. ТУІ 925. Hazeltine, ADMSA emulations.
software setup 25 x 80. Clock Swivel and tit base.
Pnnter port, Function keys ес BRAND NEW and
BOXED AT ALMOST HALF PRICE Only £425.00
AJ510 - EX RENTAL, 280 controlled. 15 green
screen 24 x BO display. graphics, cursor addressing.
printer pon etc. Very good Condition TESTED complete
with manual only £225.00
ADDS 520 - Dumb terminal, used. 12 b/w screen
interface апа primer port, TESTED.
ONLY €125.00. Carriage on terminals £10.00
100'5 of other terminals in stock, CALL for more details.
.00.
FX
ELECTRONICS & WIRELESS WORLD
|
|
|
|
ERS — PRINTERS — PRINTERS — PRINTERS
SUPER DEAL? NO - SUPER STEAL
| THE FABULOUS 25 CPS “TEC STARWRITER"
Made to the very
highest spec the TEC
STARWRITER
FP1500-25 features a
very heavy duty die cast
shassis and DIABLO
type print mechanism
giving superb
registration and print
quality Micro: processor
electronics offer full
DIABLO/QUME command
a fraction of its original cost
E E
ympatability and tu
ETC. Many other features include br directional printing switchable 1
full width 381mm paper handling with up to 163 characters per
rollers tor single sheet or Continuous Paper, internal buffer. standard RS232 seria
TELETYPE ASR33.-
DATA 1/0 TERMINALS
Industry standard, combined ASCII
110 baud printer, keyboard and 8
hole paper tape punch and геаде!
Standard RS232 serial interface
Ideal as cheap hard copy unt
or tape prep. for CNC and NC
machines. TESTED and in good
condition. Only £250.00 floor
stand £10.00. Carr & Ins. £15.00
И ПИ
EX NEWS
SERVICE PRINTERS.
control ма СРМ WORDSTAR
or 12 pitch
пе. friction feed
interface with handshake. Supplied absolutely BRANO NEW with 90 day guarantee
and FREE daisy wheel and dust cover. Order NOW or contact sales ftice
able £10.00. Tech
information. Optional extras RS232 data
Feed £140.00 Spare daisy whee! £3.50. Carriage & |
NOW ONLY £499 + VAT
for more
an £7.50. Tractor
км )£10.0
Compact ultra reliable quality built unit
made by the USA EXTEL Corporation
Often seen in major Hotels printing up ‘о
the minute News and Financial inform
ation, the unit operates on 5 UN'T
BAUDOT CODE from a Current loop
RS232 or TTL serial interface. May be
DIY PRINTER MECH |
connected to your micro as a low Cost
printer or via a simple interfa е and filter
to any communications receiver 10
enable printing of worldwide NEWS
Brand New surplus of this professional printer
TELEX and RTTY services
Supplied TESTED т
second hand
chassis gives an
outstanding opportunity for the Student. Hobbyist or Robotics | condition complele with DATA, 5O and
constructor to build a printer - plotter - dlgitiser etc, entirely to their 75 baud xtals and large paper roll
own specification. The printer mechanism 15 supplied ready Бы. | ТУРЕ AE11
aligned and pre tested but WITHOUT electronics Many features 50 Column ONLY £49.95
include all metal chassis, phosphor bronze bearings 132 character | Spare paper roll f гАЕ11 £4.50
optical shaft position encoder, NINE needle head. 2 x two phase 12V | ТУРЕ AF11R 72 ‹
stepper motors for carriage and paper control, 9.5 Рарег platten etc тозе Ree £65.00
etc. Even a manufacturer's print sample to show the unit's capabilities"! ASCII/BAUDOT £185.00
Overall dimensions 40 cm x 12 cm x 21 cm
Sold BRAND NEW at a FRACTION of cost ONLY £49.50 + pp £4.50
20,000 FEET OF ELECTRONIC
Carriage and Insurance £7.50
AND COMPUTER GOODIES
ENGLAND'S LARGEST SURPLUS STORE - SEEING IS BELIEVING!
DEC CORNER
MAG TAPE DRIVES
POP 1140 System comprising of CPU, 124k
memory & MMU 15 line RS232 Interface
ВРО2 40 MB hard disk drive
TU10 9 track ВОО ВРІ Mag tape drive. dua
track system. VT52 VDU. etc etc Tested and
uang, £3.750.00
BA11-MB 3.5" Box, PSU, LTC £395.00
DH11-AD 16 x RS232 DMA
interface £1,900.00
OLV11-J4 x EIA interface £350.00
DLV11-E Serial Modem support’ £190.00
DUP11 Synch. Serial data i/c £650.00
00200 Dilog - multi RK controlier £495.00
0211-В 8 iine А5232 тих board £650.00
KOF11-B M8189 PDP 1123
PLUS £1,100.00
LA3O Printer and Keyboard £80.00
LA36 Decwriter EIA or
20 mA loop £270.00
MS11-JP Unibus 32kb Ram £80.00
MS1 1-LB Unibus 128kb Ram £450.00
MS11-LD Unibus 256kb Ram £850.00
PDP11/05 Cpu Ram, i/o etc £450.00
PDP11/40 Cpu. 124k MMU £1,850.00
RT11 ver 38 documentation kit £70.00
RKO5-J 2.5 Mb disk drives £650.00
KL8 JA PDP 8 async i/o £175.00
M18E PDP 8 Bootstrap option £75.00
VT50 VDU and Keyboard
20 mA £175.00
VT52 VDU and RS232 interface £250.00
E Give your VT10O a Birthday! :
E Brand New VT100 Keyboards :
E only £85.00 Н
Sesvesaoetoscocssassetasesuevesoeone setesaacoo
1000's OF EX STOCK spares tor PDP8, PDP8A
PDP11, PD P1134 etc. SAE. for list. or CALL
sales office for details
ALL TYPES OF COMPUTER EQUIPMENT AND
SPARES WANTED FOR PROMPT CASH
PAYMENT.
1000’s of other EX STOCK items including POWER SUPPLIES, RACKS,
EQUIPMENT, CABLE, CONNECTORS, HARDWARE, MODEMS, TELEPHONES,
Many EX STOCK computer tape drives and spares by
PERTEC, CIPHER, WANGO, DIG!DATA, KENNEDY
etc. Special offer this month on DEI Cartridge {аде
drives ONLY £450.00 each.
CALL FOR DETAILS
All in one quality computer cabinet with integral
switched mode PSU. mains filtering. and twin fan
cooling. Originally made tor the tamous DEC РОР8
computer system costing thousands of pounds
Made to run 24 hours per day the psu is fully
screened and will deliver a massive +5v DC at 17 amps. +15v DC at
1 amp and -15v DC at 5 amps. The complete unit is fully enclosed
with removable top lid, filtering, trip switch, power and run leds
mounted on ali front panel, rear cable entries, etc. etc. Units are in
ооа but used conditio supplied for 240v operation complete with
ull circuit and tech. man. Give your system that professional firish
for only £49.95 + carr 19° wide 16 deep 10.5 high. Useable area
16° w 10.5'h11.5'd
Also available less psu, with fans etc. Internal dim. 19 м. 16 d. 10.5 h
£19.95. Carriage £8.75
66% DISCOUNT ^
Due to our massive bulk purchasing programme, which enables us t bring you the
best possible bargains, we have thousands of ICs. Transistors. Relays Caps. PCBs
Sub-assemblies. Switches etc etc. surplus to OUR requirements. Because we don't
have sufficient stocks of any one item to include in cur ads we are packing alf these
items into the BARGAIN OF A LIFETIME. Thousands of components at giveaway
prices Guaranteed to be worth at least 3 times what you pay. Unbeatable value and
perhaps one of the most consistently useful items you w | every биу!" Sold by
weight
2.5kls £5.25 pp £1.25
1Okls £11.25 + pp £2.25
ELECTRONIC
COMPONENTS
EQUIPMENT
5 kls £6.90 + £1.80
20kls £19.50 + pp £4.75
GE TERMIPRINTER
—
`
A massive purchase of these desk top
printer terminals enables us t ffer you
these quality 30 or 120 printers
at a SUPER LOW PRICE against their
st of ove 1000 t
omprises of full QWERTY electr
keyboard and printer mech with print
face similar to correspond e Quality
typewriter Variable forms tractor unit
enabies full width up to 13.5 0
column paper, upper ower ase
standard RS232 senal interface. interna
vertical and honzonta! tab settings
standard ribbon adjustable bauc
rates, quiet operation plus many other
features Supplied complete with manua
Guaranteed working GE30 £130.00
GE1200 120 cps £175.00
ntested СЕЗО £65.00 Op
stand £12.50 Carr ё Ins £1
SEMICONDUCTOR
‘GRAB BAGS
па! floor
Mixed Semis amazing value ntents
n de transistor ада пеа
їпас<. diod bridge recs. е e
A эмсез guaranteed brand new fu
pec with nufacturers markings. fully
guaranteed
50- £2.95 100+ £5.15
TTL 74 Senes. A gigantic purchase of ап
across the board" range of 74 TTL series
ICs enables us to offer 100 xed
‘mostly TTL" grab bags at a price which
two or three chips in the bag w
or Пу cost to buy Fully guaranteed г
C's full spec. 100+ £6.90,
200+ £12.30. 300+ £19.50
MAINS FILTERS
CURE those unnerving hang ups and data
glitches caused by mains interference with
professional quality filters SOSA mat h
box size up to 1000 watt 240 V
Load ONLY £5.95. 112127 ompact
mpletely cased unit with 3 pin fitted
socket up to 750 watts ONLY £9.99
The amazing SOFTY 2 The ‘Complete
olkit" for copying. writing. modifying a
sting EPROMS of the 2516. 2716
2532, 2732 range. Many other functions
nclude integral keyboard. cassette inter
face. serial and paralle UHF modulator
ZIF socket et
ONLY £195.00 + pp£2*
'GANG OF EIGHT Melligent 28
controlled 8 gang programmer for ALL
single 5v rail EPROMS up to 27128 Wi
copy 8 27128 in ONLY 3 MINUTES. Interna
LCD display and checking routines for
IDIOT PROOF operation. Only £395.00 +
pp £3«
‘GANG OF EIGHT PLUS" Same spec as
above but with additional RS232
мепасе for down line loading data from
computer etc. ONLY £445.00 + pp £3.00
Data sheets on request
COOLING FAN
Keep your hot parts COOL RELIABLE
COLING FANS ЕТА! 126LF21 24 ade eQuiprne
38mm £9.95 ETRI 99XUO! 2 E
От. 92 92 an NEW
GOULO J8-3AR 3
240v a NEW £695 MUFFIN-CENTAUR
BOXER standard 12 12
240v.3 blade NEW at £10.50 ted EX EQUIPMENT
£5.50. Low г BUHLER 69.11.22 6
а
went fe M
62 2 £35.00 OUR PRICE
ONLY £13 95 2 3
DC fa PANSONIC ЕВ. 12C12H v ade £18 00
PAPST 4124X 24 28 lade £18.00.
100's of other fans Ex Stock
all fo Post & Pack 5 (
RELAYS, TRANSFORMERS, TEST
VARIACS, VDU'S,
PRINTERS. POWER SUPPLIES, OPTICS, KEYBOARDS etc. etc. Give us a call for your spare part
requirements. Stock changes almost daily.
Don't forget, ALL TYPES and QUANTITIES of electro
ENTER 84 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD
ic surplus purchased for CASH
453
Scientific interface for the
Amstrad PCW
The Amstrad PCW8256/85 12 is marketed аз a low-cost
word-processor, but it can also make an excellent
Ithough marketed for small business
Д т Amstrad's PCW
machines are supplied with powerful
CP/M and Basic software, a large internal
memory (256K or more) and the ability to
handle graphics on screen and printer.
This design exploits the features of the
8256 to provide a simple. general-purpose
interface that can be used to generate,
record, analyse and plot complex waveforms
or voltages without the need to purchase
extra peripherals. It offers both analogue and
digital input and output and uses modular
circuitry which can perform as a complex
function generator, waveform recorder, pat-
tern simulator, or general purpose measur-
ing system for software measurement or
control of analogue or digital real-world
parameters.
Its facilities also allow the investigation of
such techniques as digital signal processing,
network analysis, speech and music synth-
esis, and can help in the teaching of elec-
tronic theory.
The unit was first designed to allow simple
programmable measurement and waveform
generation for applications in the d.c. to
upper audio-frequency range: for example.
battery discharge curves, speech and music
waveform synthesis and capture or monitor-
ing and storage of one-off events that other-
wise are not suitable for an oscilloscope.
However, it became apparent that signifi-
cant power came from the inclusion of
analogue output as well as input, thus
permitting waveforms to be replayed. edited
or created directly from software.
With the ability to use over 85% of the
Processor memory for data storage (exclud-
ing the large memory disc within the com-
puter), the unit has been used for
e digitizing or synthesizing music and
speech
e waveform capture
@ measuring voltages
€ waveform storage, plotting and manipula-
tion
e replay from waveform library to oscillo-
Scope, chart recorder etc.
e controlling or monitoring t.t.l. logic
ө measuring network transient response.
А block diagram of the scientific interface
is shown in Fig.l. The processor bus avail-
able at the rear of the computer is buffered
and decoded to communicate with five sepa-
rate modules: two analogue to digital con-
454
computer for the laboratory.
BRIAN J. FROST
- ve supply for
a-to-d converters
and 1/0
3h digit Analogue
dual -stope protection
a-to-d
& conditioning
converter
8-bit 10ps
successive-
-approx
converter
Address
decoding
and :
buffering 8-bit 1р5
d-to-a
converter
(Fig2)
B-bit ttl
output
8-bit ttl
input
Ñ
Amstrad 8256 or 8512 computer
ELECTRONICS & WIRELESS WORLD
verters, one digital to analogue converter
and a simple digital input and output.
Circuitry between these functions and the
outside world provides conditioning and
protection against damage, an important
point that has often been considered trivial
in other designs.
To keep the design as simple as possible,
software control has been adopted for all
data transfers. For example, waveform gen-
eration is performed simply by outputting
data bytes via the eight-bit d-to-a converter.
Such data can be created by Basic programs,
derived from user-written functions that
generate sine, square, triangle or even ‘fun-
ny’ shapes, or supplied by replay of previous-
ly recorded data captured by the a-to-d
converter and stored in the disc waveform
library. The interface's versatility results
from the large memory available.
Although they provide greater speed,
more hardware-intensive techniques such as
d.m.a. were not considered here since the
aim was not primarily to exceed the upper
audio band but rather to provide circuitry
that would interface easily to existing lan-
guages, besides being simple and flexible in
construction and use.
ANALOGUE 1/0 DEVICES
Despite certain performance restrictions im-
posed by the software approach, the choice
of devices used for the analogue i/o is still
fundamental to the design and so it is worth
identifying the trade-offs available.
It became clear that for analogue input no
single a-to-d converter would allow
measurement to be made at high-speed,
with good resolution and at reasonable cost.
It is a point of interest that there is no other
semiconductor sector where the trade-off
between performance and cost is more
marked than in analogue data converters.
Despite continuous improvement in value
for money, popular converters are still of two
main types: successive approximation and
integrating. Each has advantages and dis-
advantages. A successive approximation
converter is fast (often less than 505$ con-
version time) and is readily available from 8
to 12 bit resolution. In contrast, an integrat-
ing is much slower (often less than 25
conversions per second) but easily provides
greater precision with the equivalent of 12 to
16 bits resolution. Integrating converters
also have a certain inherent immunity to
noise and mains pick-up and in many cases
offer auto-zeroing and dual-polarity logic.
To offer good precision and yet high-speed
measurement, a low-cost device of each type
has been included in the design, with switch-
ing so that the final choice can be decided by
the application. The devices selected are a
high-speed eight-bit successive approxima-
tion converter sampling at up to 100k
samples per second, and a low-cost 32-415
b.c.d. dual-slope integrating converter that
provides 0.0596 resolution as well as dual-
polarity, auto-zero and noise rejection, at a
speed of around 15 conversions per second.
Choosing the digital to analogue conver-
ter is rather easier since an eight-bit device
allows good waveform resolution and a speed
of operation limited only by software. De-
spite this software speed limitation, sine
ELECTRONICS & WIRELESS WORLD
Пу
7515 245
Amstrad connector
Fig.2. Address decoding and buffering module plugs into the Amstrad bus connector.
Referred to as
‘card bus’
in following circuits
To Figs & to9 inc
for chip selects
© — м мш) о — м ow
waves well into the kilohertz region can be
generated. High-frequency waveforms are
easily cleaned up using simple RC filtering
since the sampling harmonics do not appear
until around 30kHz.
To be continued.
Brian Frost, C.Eng., M.LE.E. graduated
from Bangor University in 1974 with a
degree in electronic engineering. Until re-
cently he was in charge of the design of
automatic test and manufacturing equip-
ment at STC; now he is with Deltest Systems
working on advanced analogue specific a.t.e.
His spare-time interests include writing
and an involvement with Remap, a UK-wide
network of engineering working voluntarily
to make special aids for the disabled. In this
field he is working on radio communication
aids for the deaf. He is also a licensed radio
amateur, G6UTN.
COMPONENTS
The interface is available fully assembled
and tested at £139, or in the following kit
stages:
Kit A: printed circuit board with connector
for address decoding circuitry of Fig2,
£16.50.
Kit B: address decoding circuitry of Fig.2,
inciuding p.c.b, connector, and all compo-
nents fully assembled and tested, £31.50.
Kit C: complete interface including case,
p.cbs, components, connectors, switches
and interconnecting cable, £117.50.
Prices include postage and packing but
please add v.a.t. at 15%. Orders or enquiries
should be addressed to Placepower Ltd, Unit
24, Longs Industrial Estate, Englands Lane,
Gorleston, Norfolk NR31 6BE; telephone
0493 603771.
455
Alcatel and ITT
converge on IT
the establishment of a new telecom-
munications company, Alcatel NV. This
new alignment will be instrumental in plac-
ing greater stress on information technology
and the convergence of telecommunications
and computing. A joint venture consisting of
the telecommunications activities of the ITT
Corporation worldwide and all of Alcatel of
France and Cables de Lyon activities under
the management of the Compagnie Générale
d'Electricité (CGE), the company is active in
110 countries, with annual sales of $12
billion and some 150 000 employees. CGE
group controls 55.6% of the company and
ITT owns 37%.
At the same time as bringing together
these resources the new company will make
existing and prospective customers (includ-
ing PTTs and thus, effectively, governments)
re-examine their procurement policies and
is therefore a realignment of the industry.
This is especially so in public switching,
where a country rarely has more than two or
three suppliers, and so this can be seen as
another step in the rationalization in the
market-place. In other areas it could well
bring the benefits of economies of scale.
In the short to medium term, the out-
come will probably be less than the sum of
the individual parts. This is due to the
difficulty of merging two companies which,
because of their very size, overlap in a
number of product areas. Thus, an amount
of rationalization will be required — some of
which will no doubt be traumatic. Even
before this occurs, it will already have
changed the centre of gravity of the telecom-
munications industry.
With sales forecast to reach $12 billion
this year, the new organization becomes the
world's second largest telecommunications
supplier with a broad spread of activities
including public switching, business sys-
tems, cables and a variety of consumer and
industrial products. It claims to be the
world's largest international supplier of pub-
lic network equipment and to have market
leadership in digital switching and transmis-
sion equipment, including advanced fibre
optic systems. However, while in the fullness
of time Alcatel will have a higher profile,
many people in the UK will not even recog-
nise the name even though many more will
know ITT.
ITT has occupied an important place in
the UK for many years. Probably most widely
known in the High Street are the tv sets
bearing its name and STC (once Standard
Telephones & Cables) was one of its UK
subsidiaries. Even though it no longer has
control, it still holds 2496 of STC's shares.
Last year Alcatel and ITT had total sales in
public telecommunications of around $5
billion and, in digital public switching
J anuary | saw the start of a new era with
456
ADRIAN J. MORANT
together they have 37 million lines either
installed or on order in 76 countries. The
new company will develop and market both
the Alcatel E10 and ITT's System 12. Alcatel
is a pioneer of digital switching. having
supplied the world's first digital public tele-
phone exchange, which was commissioned
in France in 1970. Since then, with 765 E10
exchanges in service, over half of the French
network is already digital while the whole of
the country can benefit from the 64k-bit/s
switched bearer service to transmit data and
image. Fully compliant with the latest
CCITT standards, the system will allow for
smooth migration from PSTN to ISDN.
ITT entered the business much later.
Nevertheless, almost two million equivalent
lines of System 12 have been handed over to
PTT customers in 14 countries while the
total order book has now reached 14 million
equivalent lines for 21 countries over the
next 10 years.
Today five subsidiaries of the new com-
pany (SEL in West Germany. BTM in Bel-
gium, FACE in Italy, Standard Electra in
Spain and STK of Norway) are principally
involved in production and development of
System 12 under the central co-ordination
of a public switching headquarters based in
Brussels. These companies are involved in
technology transfer to other manufacturing
subsidiaries of the new company, in direct
export to world markets and in joint ven-
tures and licence agreements for local pro-
duction in countries which include China,
Turkey and Yugoslavia.
It has been announced that development
will continue on enhanced features for Sys-
tem 12 (which in recent times has involved
R&D expenditure in excess of $100M per
annum) to meet PTT requirements for
ISDN-related services. However, System 12
deliveries have been running late and the
view has been frequently voiced that the
design is flawed. While ITT could not deny
that there were delays, it, and now Alcatel,
assure everyone that these problems are
things of the past.
In West Germany, the Deutsche Bundes-
post has started Europe's first large-scale
ISDN field trial. This trial includes a System
12 exchange in Stuttgart to which 400
full-ISDN subscribers will be connected. In
Belgium, the PTT is the first one in Europe
to introduce CCITT No.7 common channel
signalling links between exchanges for
handling both signalling and call charging
information. This feature is being im-
plemented on System 12s throughout the
country. Other systems include a combined
exchange in Denmark handling traffic
equivalent to a 40 000 line local exchange
E
— ái el ess BEBBELIZLLLLILLLEOLULLUULULLLLULLLLLLULUOELULLLLÁLDEZGEERAULQBRSE)AAAALAAANGAR'HÓGZÓíLUANN
and a group of exchanges in Norway, equip-
ped for 70 000 lines. which interconnect
local and toll exchanges with remote sub-
scriber units. It does appear, therefore, that
System 12 is getting over its early problems.
In radio links Alcatel is Europe's largest
and the world's second supplier with over
100 000km of equipment already in service.
In submarine cable links, it holds 2596 of the
world market outside the USA. This amounts
to some 31 000 nautical miles of submerged
cable containing 3 400 repeaters.
In addition to conventional copper cable it
has a new generation of digital optical fibre
systems. These activities stem from Cables
de Lyon together with the fibre optic activi-
lies of ITT in the USA. This is possibly one of
the reasons that STC has been excluded from
the joint venture, even though ITT owns a
large proportion of its shares. After all, STC's
expertise in submarine cables — including
optical — is in direct competition.
In terms of subscriber services, Alcatel
switches are central to the French videotex
service. The growth of this network, which
now serves over three million subscribers; is
in part due to the French government's
electronic telephone directory project. This
ensured that there was a large installed base
that would attract information providers.
Similarly in mobile communications, the
group manufactures both u.h.f. and v.h.f.
network equipment and mobile units and
has joint agreements with different Euro-
pean manufacturers to develop a 900MHz
digital cellular radiotelephone system which
it hopes will be adopted as the future
European system.
In business systems the new company will
have sales of around $3.2 billion (£2.5G). As
well as producing over 10 million telephone
instruments, Alcatel has its existing range of
p.a.b.xs and telephone key systems while ITT
brings its Office 2000 system. This latter is
broken into three basic elements essential to
a user's information management system:
telecommunications (orientated towards
private systems); data communications
(host/computer orientated systems) and
computing where ITT has a family of small
business computers. It encompasses a com-
plete range of hardware and software rang-
ing from telephone handsets and peripherals
like facsimile machines up to powerful
super-minis that link to mainframe compu-
ters.
Altogether, this is enough to make a very
powerful group with enormous resources.
However, success in many of its areas of
operation is not only determined by tech-
nical and direct commercial considerations
— politics and even national aspirations are
involved. The broad spread of product mix in
telecommunications and IT will provide
many opportunities but only time will tell.
ELECTRONICS & WIRELESS WORLD
R Е P RI NTS a ready made sales aid
Е ВА А] ВМА) FOR PROFESIONAL ЕМЫ)
ELECTRONKS ELECTRONICS ELECTRONICS
& WIRELESS WORLD & WIRELESS WORLD & WIRELESS WORLD
— =
P.c.b.
con nector
Earthquake
prediction by
radie
Indu.trial
solderi
technology
Orthegonaltty
and Walsh
introduction
Television
standards
conversion
———— ”
Mobile
police radio Single-ended
-e > € conductance
Recording
Parameters
forape - revisited Designing
hte = -s toroidal
Distortion g МАКС 87 transformers
n АРС Sciertific
interace for
Electronics
pioneers -
new series
PCW3256/
8512
If you are interested in a particular article or advertisement in this publication why not take advantage of our
reprint service.
We offer an excellent, reasonably priced service.
For further details and a quotation.
Ring Kaye Locke on 01-661 3779
. Th IBM User:
Willesden Transformer Co Ltd ELECTRONIC Engineers | Foree.
ENGINEERS |a uus
* Toroidal - 10mm i.d. to 350mm o.d. * useful | 'ouradven
lighthearted prices people | оправе 365
* Laminated — From 1VA to 5KVA *
* Ferrite — For s.m.p.s. etc. *
ж Just released ж
MITEYSPICE
incorporating the unbeatable
Microspice circuit simulator
Probe around Miteyspice's
computer model of your circuit
More informative, more fun and
faster than a breadboard. Plot the
AC & DC characteristics, quantify
bandwidth with the digitising
А quality product at a competitive price
Cursor, sweep componenti, (£119 + VAT)
investigate t ture and noi
Approvals to DEF 05.21 + BT to 5/50 Pt. | (20 param Ebers Moll model) and. P.C.B.
when perfect, lay it out and etch it
accurately with PCB using an
ordinary DM printer. These
programs have too many superb
features to cover here, please send
for details
Pineapple's acclaimed “a utility |
thoroughly recommend” Julian
Rogers Micro User March '87
circuit board ganing program
(£85 + VAT)
REGAL WORKS, STANDON, HERTS
ENTER 730N REPLY CARD
Editorial Feature List
MAY 1987
Logic analysers are clearly indispensable to
those working on digital system design or
maintenance. This feature presents the
characteristics of those available and discusses
applications.
MUTEYSPICE +
Ф 313452419
JUNE 1987
Batteries. Recent developments in battery design
Postal address, callers by appointment
mean that an investigation into the new types Tel: 106a Fortune Green Road Tix:
available is needed. We discuss design and 01-435 pate bii te 8950511
applications and characterize the types on the 2771 АК 23332001
market.
For further advertising details please ring
Ashley Wallis on: 661 8641
THOSE ENGINEERS Ltd
(also at Fairoaks Airport, Chobham)
ENTER 81 ON REPLY CARD
ELECTRONICS & WIRELESS WORLD 457
66
uality can’t be put in at the end:
you've got to build it in from the
beginning,” seems to be the con-
ventional wisdom behind Quality Assurance
(QA). New government standards may be
encouraging this attitude, but if there’s a
"revolution" taking place in the QA world, its
happening slowly.
“A cultural change is taking place in QA,
and it’s not before time,” according to Mike
Perry from the British Standards Institute,
“the next five years should be very exciting.”
Perry says the move to higher quality is
coming from the top downwards. The new
corporate philosophy, according to Perry, is
‘Total Quality Management’ (TMQ). TMQ, an
American phrase with its roots firmly in
Japanese management practice, calls for
productivity to go hand-in-hand with quali-
ty. The idea is to involve all members of the
workforce to keep the customer satisfied at
every level. In some Japanese plants, for
example, production line workers have been
able to send components back to the pre-
vious work station when they are not satis-
fied with the quality of the piece.
The British government is seen to be
promoting TMQ with the introduction three
years ago of BSI 5750. Made up of three
parts, BSI 5750 introduces the art of statis-
tical process control, so that any flaws can
readily be identified and put right. The idea
behind BSI 5750 is for major companies —
such as British Aerospace (BAe) and British
Telecom (BT) — to put pressure on their
sub-contractors to conform to quality stan-
dards. Quality becomes the responsibility of
the sub-contractor. The government is
therefore using the purchasing power of
these giant corporations to bring smaller
companies into the quality line.
Parallel with the commercial develop-
ments have come a new set of military
procedures. The new NATO AQAP standards
replace the old 0251 MoD standards. Again,
the responsibility for maintaining standards
lies with the sub-contractors. When certified
by MoD inspectors, the company is then
visited around four times a year to make sure
things are up to scratch, according to an
MoD spokesman. The Мор also has a veri-
fication workshop where more detailed in-
spection work can be undertaken.
So what sort of people are being taken on
in the QA business? The general standard
seems to be an HND followed by three to five
years of experience. The favoured age range
seems to be 24-38 but, as with all these
guidelines, they're only approximate. The
average pay package for a suitably qualified
and experienced engineer is around
£12,000.
Steve Ollerton from Data Engineering
Recruitment said that, while they prefer two
to three years experience, a shortage of good
QA engineers means they'll take somebody
with 12 months under their belt — so long as
the experience is directly related.
458
VY
Quality assurance
QA is big business at BAe's Stevenage
plant, with a staff of 850 out of a total
workforce of some 6 500. These people cover
all aspects of the spectrum from technicians
to engineers. These include calibration en-
gineers using proprietary test equipment.
BAe recently passed through its AQAPS
procedures with "flying colours" according
to personnel manager Richard Aubigne.
Aubigne says AQAPS covers all areas of the
plant including quality planning. “AQAPS
takes the skill away from people," said
Aubigne. "You can't do things your own way
and that's no bad thing as you can't miss
anything out this way." BAe currently has a
vacancy list for 20/30 QA people – right
across the board. Officially, for engineers
BAe requires an HNC with six years of
experience. However, with such good train-
ing facilities, the company is willing to take
people on with the right qualifications and
thentrain them up themselves.
Aubigne said calibration engineers seem
to be the hardest to come by "Some take
months to recruit — others take a couple of
years," he said. With such a specialized area
and modest salary, Aubigne said BAe is
finding recruiting the right engineers very
difficult indeed.
David Hunt from Interlord — a
Wimbledon-based recruitment company —
said there’s a large demand for QA engineers,
not just in this country but in Northern
Europe as a whole. Hunt maintains the
demand for British QA engineers persists
because of their high reputation for getting
the job done. Providing the engineer is
fluent in that country’s language, a well
qualified person is widely sought after. Hunt
added that the change to BSI 5750 and
AQAPS standards has led to more work for
the QA engineer. “As companies carry on
picking up new standards there's an in-
creased requirement for quality personnel,"
he said. There seems to be a shortage of
experienced people in all engineering fields.
QA engineers are in especially short demand,
according to Hunt, because of their loyalty
to one particular company. Hunt puts this
down to QA being regarded as a highly
desirable and interesting occupation.
At Plessey Semiconductors, QA personnel
come from the general graduate training
programme which takes on 25 to 40 people
each year. Vacancies are then filled as they
appear. À small proportion of engineers
cross over from electrical engineering. A
Plessey spokeswoman said it isn't any more
difficult to find QA's than any other type of
engineer — but that's hard enough!
Mark Wright from the Independent
Broadcasting Authority agreed with Hunt
insomuch as he has a very low turnover of
Quality Control staff. The IBA employs Qual-
ity engineers to monitor the technical quali-
ty and broadcasting standards of local sta-
tions. They also make sure broadcasting
equipment is up to specifications. Wright
said the IBA looks for degree-educated peo-
ple with two to three years experience. When
it does have vacancies it can't fill internally
the IBA advertises through the trade press.
While degrees are preferred by some large
companies, it seems most QA engineers take
the HNC/HND route. According to Graham
Smith from the Southampton Institute of
Higher Education, the courses are very
"hands on" practical courses, with the
theory to back it up. At HND level the
students, most of them on day release from
electronics employers, have 6/7 assignments
to complete. Smith said these assignments
are very sophisticated and a lot of emphasis
is placed on presentation with people being
groomed to become QA managers. After
finishing the HND, some students go on to
take the Engineering Council Part Two
exams, which on completion give chartered
engineer status. Smith said these exams
require six passes which can take up to three
years part-time study to complete.
Southampton also runs courses for those
people who work in QA ona day-to-day basis
at the technican level. This is a City and
Guilds 743 course, teaching Quality Control
techniques to mature people who are often
trying to be upgraded to inspector level.
With the introduction of the new standards
there is increased company demand for
training. To meet this demand South-
ampton is running courses specifically de-
signed for each company, either in-house о?
at the company’s premises.
BSI 5750 will eventually affect all manu-
facturing companies. Many larger ones,
such as BT, have already come into line and
are applying pressure on-their sub-
contractors to do the same.
Mike Perry said the job of the QA engineer
is bound to change quite dramatically. Pre-
viously a works engineer given the quality
hat, as well as many others, the QA manager
is adopting an ever more important role. The
QA manager needs to be able to gain the
respect of all departments within the orga-
nization as quality becomes an all-pervading
issue. The QA manager also needs to be able
to bend the ear of the chief executive officer,
who alone can authorize the required levels
of expenditure.
QA engineers are therefore going to have
to be of senior management status. Pay
scales seem slowly to reflect demand for
highly skilled personnel. With a large num-
ber of companies seeking to adopt the BSI
5750 standards the demand is set to in-
crease. However, it seems unlikely most
companies will be able to offer the salaries
currently on offer to some QA consultants.
According to Perry, figures of £35 000 are
not unheard of. As I said, a revolution may be
taking place but it's certainly happening
slowly.
Workfile is written by Stephen Horn, Em-
ployment Editor, Electronic Weekly.
ELECTRONICS & WIRELESS WORLD
^
Advertisements
accepted up to
12 noon March 27
for May issue
Progress from initial concepts through prototype
construction to the pre-production phase using CADMAT
techniques. Analogue and digital circuitry, incorporating
microprocessor systems, is designed and developed by our
engineers who are involved with both hardware and sottware
considerations. The broad field of activity means that engineers
can expect to move to challenging new projects every few years
according to their interest and aptitudes.
Working conditions are pleasant, the surroundings are
attractive and the support facilities
are superb. Relocation expenses are
available and shared ownership
housing schemes may be negotiated
PPOINTMENTS
DISPLAYED APPOINTMENTS VACANT: £23 per single col. centimetre (min. 3cm)
LINE advertisements (run on): £5 per line, minimum £40 (prepayable).
BOX NUMBERS: £11 extra. (Replies should be addressed to the Box Number in the
advertisement, c/o Quadrant House, The Quadrant, Sutton, Surrey SM2 5AS).
PHONE: SUSAN PLATTS, 01-661 3033 (DIRECT LINE)
Cheques and Postal Orders payable to REED BUSINESS PUBLISHING and crossed.
Design Electronic
Communications Equipment
We are now looking for voung men and women who have
electronic engineering degrees and relevant experience (2 vears
minimum). Appointments will be made on a scale ranging trom
£10,302 to €13.642 per annam but substantial improvements to
this scale are agreed and will lead to а minimum upper salary
limit of (14.458. The career prospects in the longer term are
excellent including epportunities for promotion in the salary
range £14,260 to 517,840.
For an application form or further details please
write to:
The Recruitment Officer.
H ER MAJESTY'S GOVERNMENT HM Government Communications
COMMUNICATIONS CENTRE
Centre, Hanslope Park.
Buckinghamshire MK 19 7BH
in the nearby city ot Milton Keynes.
: HANSLOPE PARK:
levels from around £8,000 — £25,000.
of your application.
TJB ELECTROTECHNICAL
PERSONNEL SERVICES,
12 Mount Ephraim,
Tunbridge Wells,
Kent. TN4 8AS.
Tel: 0892 510051
(24 Hour Answering Service)
ELECTRONICS & WIRELESS WORLD
Electronic Engineers -
What you want, where you want!
TJB Electrochemical Personnel Services is a specialised appointments
service for electrical and electronic engineers. We have clients throughout
the UK who urgently need technical staff at all levels from Junior Technician
to Senior Management. Vacancies exist in all branches of electronics and
allied disciplines - right through from design to marketing - at salary
If you wish to make the most of your qualifications and experience and
move another rung or two up the ladder we will be pleased to help you.
All applications are treated in strict confidence and there is no danger of
your present employer (or other companies you specify) being made aware
Please send me a TJB Appointments Registration form.
m
неа ge
Electrical/
Computing
Technician
PADDINGTON COLLEGE
25 Paddington Green, W2
Tel: 01-723 8826
To provide a full Technical
service in the Electrical/Electronic
Laboratories and to provide
technical support for the College's
Computer Centre at Saltram
Crescent. Includes preparation of
materials for all levels of practical
classes. £8,643- £9,957 inc.
Applicants should have at least
ONC, OND, BTEC/TEC Higher
Certificate, Advanced City & Guilds
or equivalent qualifications in
appropriate subjects, plus a
minimum B years relevant
experience (including training).
Application forms and further
details are available from the
school or college concerned.
Completed application forms
should be returned to:
PER/PS5b, Room 336a, The
County Hall, London SE1 7PB.
Closing date: 30th March 1987.
Inner London
Education
ILEA IS AN EQUAL
OPPORTUNITY EMPLOYER
459
| APPOINTMENTS |
a
Working n LIVEDEN
неа Education С
TYPE-SETTING SYSTEMS
Repair and service of digital and
: communication systems. Experience of
Electrical/ 28000 useful
Computing £12,000 + Car E.C. London
eos BROADCAST EQUIPMENT
Technician Test and service of multi-processor
PADDINGTON COLLEGE video systems |
25 Paddington Green. W2 £9,000 Middlesex
Tel 01-723 8826 CELLULAR RADIO
To provide a full Technical
Service in the Electrical/Electroni
aboratories and to provide
technical support for the College <
Computer Centre at Saltram
Crescent. Includes preparation of
materials for all levels of practica
Classes £8,643-£9,957 inc
Closing date: 30th March 1987.
Repair of R.F. Communications
equipment. Analogue experience usetul
£9,000 Camberley
RADIOCOMMS
Develop and support a wide range of
digital communications
£12,000
RADAR SYSTEMS
Repair of microwave communication
Middlesex
1 links
Computing & . cree Essex
Micro-Electronics SECURITY SYSTEMS
Technician Repair of analogue and digital signalling
systems
WESTMINSTER COLLEGE UN Berks
Battersea Park Road. SW11 4JR
Те! 01-720 2121
GRADE 5: responsible for the
day to day provision of a technical
service in relation to the с olleges
Computing dnd Information
Technology facilities on all sites ot
the college. Duties include setting
up, checking and ensuring
Satisfactory functioning and first
line maintenance of computing
equipment. £8,643-£9,957 inc
Closing date: 3rd April 1987.
Hundreds of other Electronic and
Computer vacancies to £15,000.
Phone or write:
Roger Howard C.Eng. M.LE.E. M.LE.R.E.
CLIVEDEN RECRUITMENT
92 Broadway, Bracknell,
Berkshire RG12 1AR
Tel: 0344 489489
Applicants should have at least
ОМС, ОМО. BTEC/TEC Higher
Certificate, Advanced City & Guilds
Or equivalent qualifications in
appropriate subjects, plus a
minimum8 years relevant
experience (including training
COMMUNICATIONS
CONSULTANT/
ENGINEER
HF/VHF/UHF/RTTY
BASE AND MOBILE PABX/
PAGERS
Widely experienced Afria and
Middle East.
If you need communications
you need reliability whether
its installation, maintenance
or advice, get an expert.
Contact
FREMAR
CONSULTANTS ON
TEL (0722) 742284 or
TLX 477019 ASR-G
Application forms and further
details are available from the
school or college concerned,
Completed application forms
should be returned to:
PER/PS5b, Room 336a, The
County Hall, London SE1 7PB.
Inner London
Education
Authority
ILEA I$ AN EQUAL
OPPORTUNITY EMPLOYER
TRAINEE
КАР! О
OFFICERS
‘ooking for o secure shore-based job which otters
a rewarding career in the forefront of modem Tele
3 communications technology... then consider
joining GCHQ os o Trainee Radio Office
Training involves а 32 week 1 iol
course, [plus 6 we u cannot
touch type) after which you will be
appointed RADIO OFFICER and undertake
Ovoriely of specialist duties covering the whole
of the spectrum from DC to light
We offer you: Job Security · Good
Career Prospects · Opportunities
for Overseas Service · Attractive
Salaries... and much more.
lo be eligible you must hold or hope
to obtain on MRGC or HNC ino
Telecommunications subject with
an ability to read morse at рт
Anyone with PMG, MPT or 2 years relevant radio operating experience is обо eligible
The Civil Service is on equol opportunities employer
Are you
Salaries: Starting pay for trainee
or over entry will be at £6,572. Alter training on RO will start ot £9,758 rising by 5
annual increments to £14 387 inclusive of shift ond weekend working allowance
Write or telephone for on opplication
fom to:-
age pointed to 21 years. For those одеа 21
THE RECRUITMENT OFFICE, GC
OAKLEY, PRIORS ROAD, CHELT
OR TELEPHONE (0242) 32912/3
ROOM A/1108
М. GILOS (152 5А)
PART-TIME TUTORS,
ENGINEERING. Part-time tutors
required in the following subject areas:
Basic electronic skills; Digital and
analogue electronic engineeering. Posts
available throughout the UK.
enhancing their pay, or recently retired
professional persons anxious to retain
contact with their subject areas. Please
write to Academic Consultants. c/o
Group Four Marketing Services, 138
High Street, Eton, Near Windsor
Attractive rates of pay and ideall suited BerkshireSL4 6AR. 386
for College Lecturers interested in
ATTN FREMAR CONSUL
ELECTRONICS RESEARCH
AT THE
UNIVERSITY OF ESSEX
Graduates who have (or final year students wh expect to obtain) a first or upper
second class honours degree are invited to apply for research leading to a higher
degree (M.Sc.. M Phil. or Ph.D.) in the following area:
Hardware/Software/Systems
£900 - £25,000
As a leading recruitment consultancy we have a wide selection of opportunities
for high colibre Design, Development, Systems and supporting staff throughout the UK
W you have experience in any ol the following then you should be talking to usfor
your next! career move
ARTIFICIAL INTELLIGENCE + IMAGE PROCESSING + ANALOGUE DESIGN
MICRO HARDWARE & SOFTWARE + GUIDED WEAPONS + С + PASCAL
ADA * RF & MICROWAVE + ELECTRO-OPTICS + SIMULATION + Cil
REAL TIME PROGRAMMING я SYSTEMS ENGINEERING * ACOUSTICS
SONAR + RADAR + SATELLITES x AVIONICS + CONTROL + ANTENNA
VLSI DESIGN
Audio Engineering
Computer Systems - Information Systems
— Man-Machine Interaction
Computer-Aided Design
Digital Transmission
Display Systems
Image Processing
Optical Communications
Performance Engineering
Radio and Satellite Systems
Opportunities exist with National, Internationol and consultancy companies offering
excellent solories ond career advancement
To be considered for these ond other requirements contact John Spencer or
Stephen Morley orforword o detailed CV in complete confidence quoting Ref. WW/66.
- € —— БЕР SIF STS Recruitment, 85 High Street, Winchester,
Further information and application form available from: Professor D.E. Pearson Hants 5023 9AP. Tel: (0962) 69478 (24 hrs).
Chairman, Department of Electronic Systems Engineering (EWW). University of
Essex. Wivenhoe Park, Colchester CO4 350
ELECTRONICS & WIRELESS WORLD
460
MAINTENANCE
SUPERVISOR
Communications
Outside Broadcasts
We are looking for an Engineer equal to the challenge of running
the Maintenance and Test Area of our largest centre of Mobile
Radio Links in the country.
The equipment ranges from Satellite ground station and Radio
link control vans, through SHF, UHF and VHF video and audio
links to radio telephones and digital audio equipment.
You should hold an HNC, B/Tech Higher Diploma or Degree in
Electronics Engineering and have some experience of one or
more of the types of equipment listed.
Good opportunities for promotior will exist for the right
applicant.
Salary: £13,194 - £16,796 plus an allowance of £597 p.a.
200 tv]
Ext. 316.
The job is based in West London and relocation expenses will
be considered.
For further information contact John Sewell on 01-992 5344
For application form contact (quote ref. 5580/WL) BBC
We are an equal
opportunities employer
mm mm um eee UN um mm mm um та um шы ыш шш тщ
І
CAPITAL APPOINTMENTS LTD
THE UK's No. 1 ELECTRONICS AGENCY
If you have HNC/TEC or higher qualifications and are
looking for a job in design, test, customer service, technical
sales or similar fields:
Telephone new fer our free jobs list
We have vacancies in ail areas ef the UK
Salaries to £15,000 pa
01808 3050
(24 hours)
CAPITAL APPOINTMENTS LTD
76 WILLOUGHBY LANE, LONDON N17 OSF
(291)
Пы um um um uum шш шш шш плюш um шш шш шш ыш ыз шш ыз
University of London
KING’S COLLEGE LONDON (KQC)
Appointments, London W1A 1AA. Tet 01-927 5799.
Completed application forms should be returned by 10 April 1987
DEPARTMENT OF ELECTRONIC & ELECTRICAL ENGINEERING
ELECTRONICS TECHNICIAN
– GRADE 6
Required for interesting and varied work for Electronics research
and teaching including protot
pe design and development and
servicing and maintenance ol a wide range of commercial
electronic equipment. Experience and qualifications in
Electronics (particularly digital) at an appropriate level are
essential.
Salary £9,708 to £11,424 per annum inclusive (under review).
Further details and application forms from Mr M. E. Cane,
Departmental Superintendent, King's College London (KQC),
Department of Electronic & Electrical Engineering, Strand,
London WC2R 2LS or telephone Mr Alan Dimes, 01-836 5454,
ext 2736.
| ARTICLES FOR SALE | FOR SALE
URERS, WHOLESALERS
BULK BUYERS. ETC.
LARGE QUANTITIES OF RADIO. TV AND
ELECTRONIC COMPONENTS FOR DISPOSAL
SEMICONDUCTORS. all types, INTEGRATED CIRCUITS, TRANSISTORS.
DIODES, RECTIFIERS, THYRISTORS, etc. RESISTORS, C/F, M/F, W/W, etc
CAPACITORS, SILVER MICA, POLYSTYRENE, C280, C296, DISC
CERAMICS, PLATE CERAMICS, etc
ELECTROLYTIC CONDENSERS, SPEAKERS, CONNECTING WIRE, CABLES,
SCREENED WIRE, SCREWS, NUTS, CHOKES, TRANSFORMERS, etc.
ALL AT KNOCKOUT PRICES — Come and pay us a visit ALADDIN'S CAVE
TELEPHONE: 445 0749/445 2713
R. HENSON LTD
21 Lodge Lane, North Finchley, London, N.12
(5 minutes from Tally Ho Corner)
VHF-FM BROADCAST
EQUIPMENT
A special range of high quality
transmitters, power amplifiers, stereo
encoders, UHF repeater links,
compressors, antennas. Powers 10w to
1kw. Built to high specifications at an
economic price. Meets IBA & Full
Broadcast specifications.
Phone now for prices and delivery:
Cyberscan International,
3 Eastcote View, Pinner,
Middx HAS 1AT. Tel: 01-866 3300 me
INVERTERS
DC-AC High Power
Gardners sq. wave type GR75108
VP: 50V DC 85A
O/P: 240V 50Hz 4kVA £300
Also 2kVA £200 - 1kVA £150
H&D Sinewave 600W
VP: 24V DC
O/P: 230V 50Hz 600VA £240
CVT's: Cetronic Reguvolt 6kVA £290:
5kVA £250; 4kVA £220; 2kVA £160
GREENWELD ELECTRONICS LTO
443 Millbrook Road, Southampton.
$01 OXH. Tel: (07C3) 772501/783740
ELECTRONICS & WIRELESS WORLD
TEST EQUIPMENT
FOR SALE & WANTED
Buyers and Disposal Officers contact
COOKE INTERNATIONAL
Unit 4, Fordingbridge Site
Main Road. Barnham,
Bognor Regis.
West Sussex PO22 0EB
Tel: 0243 68 5111/2
G.W.M. RADIO LTD
40/42 Portland Road, Worthing, Sussex.
Tel: 0903 34897
Constantly changing stock of interesting
tems for callers Recewers test equipment
componerts etc Pye pocketlone РЯ! TX
units with battery and circuits £12 inc p&p
Meters survey гадас No portable
radiation detectors untested О
information. ауаіабіе £15 inc p&p Васа
Decade Frequency Generator МА 3508 TX
Drive Unit MA79 synthesizer for callers
Radiotelephones,
Terminal Units, Test
Equipment, Ex-RAF
Radar and Instrumen:s.
Brent Electronics & Comms.
49 Seaview Street. Cleethorpes.
South Humberside DN35 8EL.
Tel: 0472 690383.
[ GOLLEDGE —
ELECTRONICS] —
QUARTZ CRYSTALS
OSCILLATORS AND FILTERS of
all tvpes. Large stocks of standard
items. Specials supplied to order
Personal and export orders welcomed
SAE for lists please. OEM support thru:
design advice. prototype quantities,
roduction schedules. Golledge
Slectronics, Merriott, Somerset YA16
5NS. Tel: 0460 73718 (2472)
BRIDGES waveformn transistor
analysers. Calibrators. Standards
Millivoltmeters. Dynamometers. KW
meters. Oscilloscopes. Recorders
Signal generators sweep, low
distortion, true RMS, audio, RM,
deviation. Tel: 040 376236 (2616)
SEMI CUSTOM IC DESIGN. Very
low cost power, fast delivery, eraseable
Special 1.6.5. standard logic, PAL
replacement. protoyping,
microprocessor peripheral application.
Design changes easily carried out. All
designs copy protected. Price starts at
as little as £50. Glenavon Electronics at
0733-133385 388
W&G - SIEMANS - STC
communications & cable test
equipment. Level meters — generators -
receivers etc. S.A.E. lists: J.B. Pattrick
191 193 London Road, Romford, Essex
RM79DJ 0708 44473 415
461
ARTICLES FOR SALE
TEST EQUIPMENT
FOR SALE
All equipment т pertect condition includes
B&K 2010/1902 superhet analyser
B&K 2305 level recorder with 4 pots
B&K 4440 gating system
B&K 2971 phasemeter
B&K 2206 precision sound level meter with
capsule
B&K 2426 auto range milivoltmeter
Enquire for full ist of B&K
HPB6, 3 25 disc drive. biodata microlink Hl.
HP7475A 6 pen plotter, other accessories
Tektronics computer 31, 152 and 2 ~ ОМ501
mutimeters HP3580A spectrum analyser
Sound technology 1700A distortion
measurement system Philips 6652
programmable high res timer counter Datron
1065 autocal DMM Sennheiser universal UDM
550 AC/dB meter Kemo VBF/14 band pass/stop
fifler Technon ! M D analyser Wayne Kerr B221
universal bridge
Please call Angus McKenzie for full list —
01-349 0511 strictly 9.30am-5.00pm.
Component Testing Bridges – Avo, В&К,
£97. Portable Variable 15A DC stabilised
PSU, £85 Portable oscilloscope. £45 B&K
2603 Microphone Amplifier, £55 Nashton
Coulometric Plating Gauge. £65 2KV
stabilised PSU, £49 BTL Electrolytic
Analysis Apparatus, £120 BTL Кай
Fischer water content analyser. £98
Electrothermal Melting Point Apparatus,
£79 Optical Pyrometer. £89 Laboratory
Thermostatic Heated Bath, £69 Tektronix
Oscilloscope dual trace, £135. Portable
Bradley oscilloscope. operates from mains,
тіегпаџехіегпаї 12У batteries. auto-charger
with boost. 20MHz, £179 Aminco
Photomultipher Microphotometer, £65
High Power White Light Stroboscope, dual
tube, £135. Tektronx 'Q' plug-in for
transducers, strain-gauges etc, £35 Апо
Velometer, meter & two range selectors for
Precision аҥ velocity measurement. £95
Avo ЕНТ meter, 0-15Ку. 0-30Kv, £35.
Record Chart Recorder, £65 Centnfuge,
£49 Electrostatic EHT Meter, 0-15Kv. £20
Stablished variable PSU. 6V metered, £20
Leak Detector, £25. Marcon Signal
Generator Tektronix plug-ins. L', £35. "E
£25. TEL: 040-376236
STEWART OF READING
110 WYKEHAM ROAD,
READING RG6 1PL.
TEL: 0734 68041
TOP PRICES PAID FOR ALL
TYPES OF SURPLUS TEST
EQUIPMENT, COMPUTER
EQUIPMENT, COMPONENTS
etc. ANY QUANTITY
WANTED FOR CASH,
SURPLUS AND
REDUNDANT BROADCAST
EQUIPMENT
Particularly medium-wave
transmitters, FM transmitters,
studio links (STL), studio
furniture, affects, cart
machines, ААЗ carts.
COMP SHOP HI-TECH
311 LONDON ROAD
CAMBERLEY, SURREY
Tel: 0276 29219
404
WANTED: Who has experience and
can develop a radar receiver with the
frequencies 9.41 and 34,36 GHz for
radar car speed control detection?
WALLFASS, P.O. Box 1244, D-405
Moenchengladbach, W-Germany.
852582, tel 2161-88555.
Tix
380
PLATINUM, GOLD, SILVER
SCRAP, melted assayed and paid for
within 24 hours. Relay contacts, p.c.b.s,
thermocoupoles, crucibles, plugus,
connectors, etc. Totally free sampling
service. Send samples or parcels
(registered post) or contact Eric
Henderson, 0773 760661. Steinbeck
Refineries (UK) Ltd, Anchor House,
Anchor Road, Eastwood, Notts. 406
ЕШ ИИИИИАИИ
CIRCOLEC
THE COMPLETE ELECTRONIC SERVICE
Artwork, Circuit Design, PCB Assembly, Test & Repair Service, О.А.
Consultancy,
Service.
Prototypes, Final Assembly. Full PCB Flow Soldering
Quality workmanship by professionals at economic prices,
Please telephone 01-646 5686 for advice or further details.
TAMWORTH MANOR
302-310 COMMONSIDE EAST, MITCHAM
IMPORTS/EXPORTS of all kinds of
Electronics and Computers. Please send
your enquiry or product details to
DEDICATED MICROPROCESSORS
LTD, 299A Edgware Road, London W2
IBB, England, or Telex 945922
GLADEX-G for the attention of Mr.
C.Paps. {300}
PRINTED CIRCUIT BOARDS
single and double sided manufactured
to your specifications. We offer quality
and fast service (same day on
prototypes) at very keen prices, We
supply copperclad material cut to size.
Artwork service available. Mondo
Circuits Ltd. 35 Grosvenor Rd.
Twickenham, Middx. 01-891 5412. 413
| ARTICLES WANTED | WANTED е
| When replying to
| classified advertisements,
|
|
readers are recommended |
|
|
|
to take steps to protect
their interest before
sending money
462
(1391)
TURN YOUR SURPLUS
i.cs
transistors etc. into cash, immediate
settlement. We also welcome the
opportunity to quote for complete
factory clearance. Contact COLES-
HARDING & CO, 103 South Brink,
Wisbech, Cambs. 0945 584 188. (92)
P.C.B's DESIGNED. Artwork
capacity available for single/double
sidod, P.T.H. and multi-layer P.C.B's,
also silk screens, solder masks, labels
etc. For C.A.D./photoplot, artwork &
hotography. contact Mr. Williams, 49
Westbourne, Honeybourne, Evesham,
Worcs, WR11 5PT. Tel: 0386 832152.409
WANTED
Test equipment, receivers,
valves, transmitters, com-
ponents, cable and
electronic scrap and quan-
tity. Prompt service and
cash. Member of A.R.R.A.
M & B RADIO
B6 Bishopsgate Street
Leeds LS1 4ВВ
0532 435649
SWINDON
RALLY
OAKFIELD SCHOOL, MARLOWE AVE., SWINDON
Sunday 10th May, open 10.30am, adm. 50р.
Radio & Electronic Equipment, Components,
Computer Equipment &
Software. Refreshments,
Entertainment for the Whole Family.
DETAILS: G8SEM QTHR.
TEL. 066689-307
ARTICLES FOR SALE
HV capacitors, Pulse Generators, Tektronix
Time/Mark Generator, £79. Plastic
Packaging Неа! Sealer, £29. Tektronix
probes. £12.50. HV Stablished PSU,
stabiliser may be senes or parallel, 1.7Kv.
ТАЛАА. £95 АнсгаН Radio Test Set, £35.
Densitometer, £35. ignition Analyser, £39.
Blue Steel Missile. Efectroruc section, and
Others, (collectorsimuseums) 5 for £50.
Vacuum pump assembly, £125.
Stereoscopic, binocular, prismatic
microscope, £195. Precrsion С & В boxes,
Precision Capacitance Bridge, £49 PSU's
various, Linear audio sweep generator, with
vanety of facilities, £69 Advance 50Kc/s
Generator, sine/square, £35. Wayne-Kerr
Source & Detector for AF Bridges, £69 ea
20A steel cased variable resistance, £40
Micro-spot Welding Head, £59. Kent
Chromalog Recorder. Marconi Frequency
meter/Counter timer, £75. pH electrodes,
Зресйк-юп Electrode, — Fluorme. £20.
Laboratory Hydrometers £5 ea. various
Pye Gas Pressure and Flow Controller. £45.
Portable Oxygen Cylinder (& oxygen) with
control valve, £35 Modulation meter (FM/
АМ), £69. etc etc 040-376236
TEST EQUIPMENT FOR SALE. 3
pallets, as one lot, including Tektronix:
7633 scope, 4 graphic display units,
8002 development system + ice for Z80
and 8085 incl. 4024 terminal incl. SW
discs + doc, 611 storage screen. C12
camera, 6046 diff. probe HP 140A scope
+ 3 plug-ins, Prowest PMA7 22” PA
RGB colour monitor. Philips LDK 65
telecine periscope + electr. SMS 3000
dev. system for 8х 300 micro controller,
Zilog Z80 development system,
complete Bryants A3 X-Y recorder.
Culton 147 L-R-C bridge, narda high
directivity — 10 db couplers, etc... etc.
Viewing at Peaks Store House, 135
Ditton Walk, Cambridge. Any time
9-1600 hours weekdays.
DISH AE Radar dishes 32° фа 5 deep new,
£26 50 RX AD94 24v DC ИР 2xL W and 4х SW
2/18 5Mc's with сис £85 VEHICLE NAV TS b
Sperry see lisi £95 RAPID DISCHARGE caps
215Uf 2 5Kv Pk ex photo tlash £14 50 lamps etc
available MONOC SIGHTS 5,275 £750
VARIACS 240v at В amps £36 REC PAPER press
ink fric teed В wide Gould £6 50 BIRO METERS
Spares for thro плех 30Ua лем £1250 AUOIO
TAPE ! 14 dia new £14 50 BLOWERS med size
Single ended 115v new £1450 CAPS 2700Uf
250v £450 33 00001 60v 2 for £6 50 ROT INV
18v DC ИР 230v 180w 50с/5 C/P £45 CT471 ELEC
multimeters with AF probes £75 АХ AE PRE
AMPS 162/174 Mc/s 4 OPs 12/24v DC £1650
PHILLIPS PM5508 TV Рай Gen £85 COAX TEST
& CONNEC LEADS see list MULTI TRACK FM
RECORDER WITH H/Bks £165 Prices are
inclusive List 39 available on request
A. H. Supplies, 122 Handsworth Road,
Sheftield S9 4AE. Tel: (0742) 444278.
BUYING OR SELLING TEST
EQUIPMENT OR COMPUTERS
For our free monthly catalogue
containing an up-to-date list of
equipment write to or phone:
David Maxfield on 048 641 3000
Albury House, Albury
Guildford GU5 ЭВР
SPECTRUM ANALYSERS - Н/Р 140S/
8552B/8553B 1KHz-110MHz - £2,500;
8553B RF plug-in – £995, 1827/8558B
0.1-1,500MHz - £4,950, Singer SSB-50-
20Hz-40MHz (160MHz with external sig-
gen). Single sideband analyser - 10Hz
resolution — £1,175, Marconi G.C.H.Q
Surveillance Receiver – Superb specs –
10KHz-30MHz, fully synthesised, 1Hz
resolution — Type 2540 — £1,495.
Matching HF Drive Unit, Type 1540 -
synthesised, all modes - £850.
icrowave power meter (10MHz-
12GHz +), 1uW-10mW - £495, BWO
Tube for H/P 8551B spectrum analyser –
£395 (tested 50mW o/p) Eddystone
Panoramic Adaptor 1061 (new) — £395.
All above equipment is in excellent
condition, with manuals. Tel: 01-866
3300. 3 Eastcote View, Pinner,
Middlesex HAS 1AT.
* Stop Press: 2Kw FM Broadcast
Linear (cancelled order) - £4,500.
SILLY PRICED T.T.L.
OWING TO DISCONTINUED
PRODUCTION WE HAVE ON OFFER
300 7415123 60 7415138
4,000 7405165 80 741500
100 7415163 1,5005 Volt Reg+
50 741574 3500741505
15 №28 3,100 7415365
100 741504
PRICE GUIDE! HALF OF YOUR
LOWEST NEW PRICE
WILL SELL SEPARATELY
PHONE: 0276 29219 (SHOP)
Comp Shop Hi-Tech,
311 London Road, Camberley,
Surrey GU15 3HE 403
FOR SALE. 2 Boards and 18MB Hard
Disk Drive for Olivetti M40 ring
Graham Ledger 01-647 4747. 385
HONEYWELL VIP7700R
TERMINALS, used, reconditioned
with manual £125 each. Tel: Gary 0268
419523 or Phil 04024 45676. 399
BOX Nos
Box number replies
should be addressed to:
Box No............
c/o Electronics &
Wireless World
Quadrant House,
The Quadrant,
Sutton,
Surrey SM2 5AS
ELECTRONICS & WIRELESS WORLD
до ое are expected to conform to rules and standards laid
down by the Advertising Standards Authority. Most do. The few that
don't we'd like you to write in about.
And if you'd like a copy of these rules for press, poster and cinema
advertisements, please send for our booklet. It's free.
The Advertising Standards Authority.
We're here to put it right.
ASA Ltd.. Dept. Y, Brook House, Torrington Place. London WCIE 7HN
This space is donated in the interests of high standards of advertising
CLASSIFIED ADVERTISEMENTS
-
Use this Form for your Sales and Wants
PLEASE INSERT THE ADVERTISEMENT INDICATED ON FORM BELOW
To “Electronics & Wireless World” Classified Advertisement Dept., Quadrant House, The Quadrant, Sutton, Surrey SM2 5AS
@ Rate £5 PER LINE. Average six words per line NAME
Minimumi £40 Tore syable). Sid esse ios dC Luar tulit Piece реа ре RAG a B C M КЛ С,
@ Name and address to be included in charge if ADDRESS
used in advertisement.
@ Box No. Allow two words plus £11
@ Cheques, etc., payable to “Reed Business
Publishing” and cross “& Co.” 15% VAT to
be added tte eee eee eee eee ee ee ee eee eee ee eee ee ИРИСИ „+++, жаз» ә
ENCLOSED
NUMBER OF INSERTIONS..
PLEASE WRITE IN BLOCK LETTERS. CLASSIFICATION .....
ELECTRONICS & WIRELESS WORLD 463
SURPLUS COMPUTER HARDWARE
(ТҮ SCRIBE 11) WORD PROCESSING SYSTEM.
Professional system originally selling at around £6000
without printer. Now offered with software included & а
variety of different options available. This system is
available from us ALL BRAND NEW at the cost of current
budget systems, but with office-quality performance &
features.
SOFTWARE INCLUDED:
*DATABASE — allows informabon storage & retrieval by
user-selectable criteria.
*EDITING — including easy reformatting, global search &
replace, save & move, cursor control etc.
*AUTOMATIC LETTERWRITING — with merge, glossary
file tor much used phrases etc.
*МАТН$ FUNCTIONS — screen maths allows addition of
rows, columns & complete tables.
*PROGRAMMABLE COMMANDS — allows format
Changes, accessing record block files, prompts etc.
*HELP FILES — quicker to use than the comprehensive
manual supplied.
*BASIC COMPILER.
HARDWARE INCLUOED:
*SCREEN/WORKSTATION — dual processor (16 bit
TI 9995 & ZBOH) with 128K memory, 12" green screen
25 x 80 character display with slow scrolling. QUME
printer interface.
*KEYBOARD — low-profile keyboard additionalty has 43
Clearty marked dedicated function keys.
*OISC DRIVES — dual SHUGART 5%” DSOD drives
each 430K capacity formatted. €295.00
OPTIONS:
*10mbyte MiniScribe WINCHESTER disc drive (£195).
*NEC Model 3500 35cps daisy wheel printer (£295).
*NEC Model 7700 55cps daisy wheel printer (£395).
*128K additional memory with spelling check software
(£40)
*Communications
hardware &
software (£95)
**COLOUR LEAFLET
HITACHI Model 305$ 3" disc drives. With SHUGART
compatible interface (34 way edge connector) & suitable
for BBC with DFS, AMSTRAD 664/6128, TATUNG
EINSTEIN & many others. 250K (double density
unformatted) per side reversible; 40 track: standard power
connector for 12V & 5V; overall power consumption
typically 3.7 W. Supplied BRAND NEW with connector pm-
Out details etc. but uncased. Data cables only are available
for AMSTRAD & BBC (£7.50) and TATUNG (£10.00).
£29.95
HITACHI Model 3050 double sided 3" disc drives.
As above, but double sided (500KB unformatted
accessible without tuming disc over). Not suitable for
AMSTRAD 664/6128.
*Over 2000 Model 305 drives already sold by us
TOSHIBA Model T300 IBM compatible PC system.
With 6mHz 8088 processor, 256KB RAM, single halt-
height 5%” floppy disc drive (640KB), high resolution
green display, serial & parallel interfaces. Included are MS-
DOS Ver. 2. MICROSOFT T-BASIC & comprehensive
diagnostic disc. Available options include a high resolution
Colour monitor, graphics cards etc.
BRAND NEW £325.00
AS ABOVE but with dual floppy disc drives.
TOSHIBA Model T100 CP/M system. With 64KB
RAM, dual 500K 5%” floppy disc drives, serial & parallel
interfaces & high resolution green display.
BRAND NEW.
DEC РОР 11/73 system. With 1MB RAM, twin 20MB
WINCHESTER disc drives, single 8" floppy disc drives &
DLV11-J quad serial interface.
с4500.00
DEC РОР 11/23 system. With 256КВ RAM, single
20MB WINCHESTER disc drive, single 8° floppy disc drive
& XENIX operating system.
€1800.00
ПТ Model 3500 FACSIMILE machine. Very compact
Group It machine allows document transmission & reception
over phone line. EX DEMO.
MATMOS PC. Available without disc drives onty. 64KB
Z80A based keyboard sized machine with RGB.
composite video outputs & UHF modulator. Serial, parallel,
cassette & peripheral bus interfaces are provided, together
with à ROM port. MICROSOFT BASIC is in ROM. Office
Quality machine originally sold at £350 by its big-name
manufacturer. BRAND NEW.
*Over 1000 already sold by us £49.00
MATMOS TERMINAL. MATMOS PC as above but with
additional plug-in menu driven terminal emulation ROM
offering RS-232 communications up to 9600 Baud. (ROM
Please note
*VAT & CARRIAGE must be added to all tems. Carnage is
£3.00 + VAT for 3° disc drives, and £10.00 + VAT for most
other items.
*SAE please, for further details of any item and complete
Stock list.
MATMOS Ltd., 1 Church Street,
Cuckfield, W. Sussex RH17 542.
1 { 5 (0444) 414484/454377
exe COMPUTER APPRECIATION, 111
S si ss]
EIU Northgate, Canterbury, Kent CT1 1BH.
(mmatmos & COMPUTER APPRECIATION
(0227) 470512. TELEX 966134 COMPAP
ENTER 25 ON REPLY CARD
INDEX TO ADVERTISERS
Appointments Vacant Advertisements appear on pages 459-463
PAGE PAGE PAGE PAGE
Adcola Products Ltd................. 357 Electronic Brokers Ian P Kinlock...... ertt 380 Ralfe Electronics...................... 376
Aden Moore Ltd........................ 380 Ltd...354 Advert Card Back Cover Ines СтЬһ................................ 376 Semicon Indexes 144................ 432
Advertising Standards Author...457 EMS Manufacturing Ltd ......... 401 JDRSheetmetal
дент: 366 h 438
Airlink Transformers Ltd........ 388 Engineering Solutions.....375,433 ^ Johns Radio Le Data Systems
...433 Stewart of Reading......
Anritsu Europe Ltd.................. Essex Electronic Centre........... 366 Kestrel Electronic 384 Structured Software.
Bamber B Electronics EWW Edit Feat. List - Langrex Supplies .... ..496 Surrey Electronics ... "E
Brigden Technology ................. EWW Wall Сһагь..................... Level Electronics... 2380 Sowter E.A. sss 388
Carston Electronics Ltd....367,432 Farnell Instruments А Lloyd Research Ltd. ....432 Target Electronics....................
Caracal Power Products........... 380 f р Inside Front Cover Marlow Marketing.. ....366 Taylor Bros (Oldham). а
Channel Micro Products Ltd....388 Field Electric et rnc. 379 M&B Radio (Leeds)... 1401 Technomatic Ltd ...............
Chase Electronics Ltd .............. 362 Fieldtech Heathrow ................. 365 McKnight Crystal Co... :414 Telonic Instruments
Cirkit Holdings PLC ................ 366 Fluke (GB) Ltd .......... Advert Card Micro Concept ...................362, Ltd ее Inside Back Cover
Clark Masts Ltd ...................... 356 Gatehouse Audio............... ......384 Microkit Ltd ...... Thandar Electronics ......... 375,405
Colomor Electronics Ltd .......... 432 Global Specialist Corporation 402 Micromake Ltd | Thanet Electronics Ltd ............ 389
Computer Appreciation........... 464 GNC Electronics .................... 389 Microprocessor Engineering....384 Those Engineers Ltd.........365,457
Conquin Software .................... 401 Golten & Verwer Partners....... Monolith Electronics Со... 376 Thurlby Electronics ................. 440
[ruin песаи. Tc 3719 Hameg Oscilloscopes........ P Moordene Аз50с..................... ...433 Triang è Digital
@........ snnm green H a Memories eeasssenessssnuafdZ NiumharQna Quetame 4999 “^еГу!Се5...............................
Cybernetic Applications .......... 405 eae Electronics ..... De E R viria eias = Valradio Power ...............
Data Acquisition Ltd Hart Electronic Kits ........ ; : посв ня: Webster Electronics ...........
Dataman Design ...................... Henry’s/Audio Electronics.......383 PineappleSoftware................. 406 West Hyde Development
Dipl-ing Franz Braunschmid 433 Henson Ltd (R) ; РМ Components Ltd.........448,449 — Willesden Transformers
Display Electronics........... 452/453. {НПотазе наа Raedek Electronics ................. 406 Withers Communication (R)....384
OVERSEAS ADVERTISEMENT AGENTS
France and Belgium: Pierre Mussard, 18-20 Place de la Madelaine, Paris 75008.
United States of America: Jay Feinman. Business Press International Ltd, 205 East 42nd Street. Mew York, NY 10017 – Telephone (212) 867 2080 - Telex 23827
Printed in Great Britain by E.T. Heron (Print) Ltd, Crittall Factory, Braintree Road, Witham, Essex CM8 o and typeset by Graphac Typesetting, Imperial House, 108 The Broadway, Wimbledon
SW19, for the proprietors, Reed Business Publishing Ltd, Quadrant House, The Quadrant, Sutton, Surrey 5М2 5А$. Q Reed Business Publishing Ltd 1987. Electronics and Wireless World can be
obtained from the following: AUSTRALIA and NEW ZEALAND; Gordon & Gotch Ltd. INDIA: A. H. Wheeler & Co. CANADA: The Wm, Dawson Subscription Service Ltd., Gordon & Gotch Ltd.
SOUTH AFRICA: Central News Agency Ltd; William Dawson & Sons (S.A.) Ltd. UNITED STATES: Eastern News Distribution Inc., 14th Floor, 111 Eighth Avenue, New York, N.Y. 10011
464 ELECTRONICS & WIRELESS WORLD
Simply Superior.
Meet GOM 7000. With band widths of 60, 100 or 200 MHz,
Technologically superior oscilloscope built-in digital storage and С.Р].В. capability,
measuring systems from Kikusui. depending on model.
With all the waveform measurement data Simply superior oscilloscopes you have
right where you need it. to see. |
Right where you're looking - on the C.R.T. Ask for data or demonstration.
‘Screen text display of sensitivity settings, = A
timebase speeds, tay times, iiie cul С Om O. OO
and frequency read out OSCILLOSCOPE MEASURING SYSTEMS
Telonic Instrumants Ltd., Boyn Valley Road, ?
Maidenhead, Eerks., 516 4EG.
Tel: (0628) 73933.
Telex: 849131.
| = "un A-S и * |
vatt даа, 0
ra of uf 4 1 1 4 iai*
--=——>7т= Ж
ЕМТЕК 76 ОМ REPLY CARD _
-
2955 Radio Communications
Test Set £5,750
1 test functions, including full duplex radio test
2382/80 Spectrum Analyser £13,470
and Display £5,480
2022 AM/FM Signal Generator
10kHz to 1GHz £2,950
Revolutionary design: fast and casy to usc
High clarity CRT shows all settings plus
measurements in digital or analog forms
Tones encode/decode facilities
38 instrument settings in non-volatile memory
Spin-wheel frequency/level control in addition to
front panel buttons
Single and two-port operation.
2305 Modulation Meter 500kHz
to 2GHz 45,418
SOOKH2 to 2GHz frequency range
Outstanding 0.5% basic accuracy
Exceptionally fast auto-tuning, with low noise
Modulation analysis including frequency and power
Non- volatile memory to store user scttings
Excellent stereo separation
Automatic self-calibration, advanced diagnostics
through
ELEC
BROKERS
Audio to UHF coverages: 100Hz- f00M Hz
Outstanding resolution, with 3Hz minimum
resolution filter bandwidth
0.025dB amplitude resolution
Superb level accuracy + 1dB, with auto calibration
Frequency response better than +0408
Fully GPIB programmable capability
Two steerahle markers for levels and frequencies
Selt calibration for repeatability of measurements
=
a
=
а
©
ш
6960 Option 001 Digital RF
Power Meter £1,900
Simple push-button or systems application
Unparalleled accuracy, through sensor correction
Non- volatile storage of trequentlv-used settings
W or dB readings, plus offset capability
Single- key auto-zero operation
Average factor selection to reduce noise or improve
resolution, advanced GPIB facilities
Wide frequency cover: IOkHz to 1000MHz
Compact. rugged and lightweight
Comprehensive modulation: AM/FM/PhM
Simple push-button operation, large LCD display
Non-volatile memory for 100 settings
The perfect service/maintenance tool
2440 Microwave Counter 20GHz
£3,650
Wide frequency Coverage: 10Hz to 20GHz
High sensitivity and resolution
Fast acquisition time: only 200ms typical
High-stability oven-controlled crystal oscillator
Overload capability up to 27dBm
High AM/FM tolerance
Built-in GPIB
Electronic Brokers are now
distributors for a full range of Marconi
Test Instruments including Signal
Generators, Microwave Counters,
Power. Meters, Modulation Meters,
Spectrum Analysers, Radio Communication Test Sets and other
general testand measuring equipment.
and a colour brochure please contact our Sales Office.
ENTER 3 ON REPLY CARD
or further information
The first name in test equipment distribution
Electronic Brokers 140-146 Camden Street, London, МММ SPB
Fax: 01-2677363 Telex: 298694 Tel: 01-267 7070
All prices exclusive of VAT. Prices correct at time of going to press (UK only ). ‘Trading conditions available on request.