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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. 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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. 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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. 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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. 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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. 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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. 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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 ? 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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. 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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. 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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.