THE R ALR PR FEINAL E I EER ELECTRON., :3 & WIRELESS WORLD

SEPTEMBER 1988 £1.95

World standard for h.d.tv? IEEE 488 interface for Z80 -based computers P.l.ds and logic probes

Flywheel step- upswitching regulator design

Alec Reeves and pulse -code modulation Dimensional approach to unified theory

Denmark DKr. 63.00 Germany DM 12.10 Greece Dn. 680 Holland DEL 12.50 Italy L 6500 IR 62 86 Main Phis. 700.00 Singapore SS 11.21' Switzerland SFr. 8.50 USA 55.95

The Gould 1604 Digita orage sci oscope

Give it a screen test The Gould 1604 digital storage oscilloscope has the memory and performance to tackle any role in low frequency electronics, mechanical or physiological R&D and test enviror ments. I '

With massive 10K word 10101 ,, memories on each of its 4 4. channels the 1604 can examine qt detail with expalsion factors up to 200 times, and resolution down to 5Ons. And it can do so much more. The 1604 has a built-in colour osciu,og_oPE plotter for instart print-outs of displayed traces, and the ability 1604-DicitrALOta to archive up to 50 traces in the MODEL Good) non-volatile memory pods. For 1K tAMoo even more capability, interface "(I WORD the fully programmable 1604 to 10K a a computer; or plug in the NEL CRANK waveform processor. atEN cN010{ FAA, The 1604 DSO has a wide range oN of automatic functions at an opozAn unbeatable price, and it's so easy to drive! Why not let it audition for you? IscAPPlesiL For further details of the 1604 or 0')DMs15 Atqfri,15 the 2 -channel 1602, contact: PAfiA 01-500 1000. AN Gould Electronics Limited oAN Test & Measurement Sales Division ieteke Roebuck Road, Hainault. Ilford, Essex IG6 3UE PRo02004H Po --L9 ikorreg Tel: 01 500-1000 Telex 263785 0 coLourz 0IIVrT-1,, goompilmorip-

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MULE I 11 ItI UN 1{1:1.1.1 Electronic. SEPTEMBER 1988 VOLUME 94 NUMBER 1631

Loran brought up to date: a new nationwide radio position -finding system is described on page 897.

KEYBOARD DESIGN 910 Details that designers sometimes overlook Jeff Wright

ANALOGUE CIRCUITS FOR COVER AUTOMOTIVE USES High -definition television will bring to domestic viewers pictures sharper even 915 than those they can see in the cinema Spike -resistant chips for cars (off -screen photographs by courtesy of Sony Rocco Shah Broadcast). A DIMENSIONAL APPROACH PAN -EUROPEAN CELLULAR EUREKA 95 -A WORLD TO UNIFIED THEORY DEMONSTRATION STANDARD 882 919 845 Dimensional relationships of common Digital radiotelephone success European promoters of high -definition physical concepts television prepare for a crucial S.K. Chatterjee demonstration BROADBAND Tom lvall INSTRUMENTATION PHILIP SMITH'S CHART -2 AMPLIFIER IEEE488-TO-Z80 INTERFACE 887 937 852 JW supplies a user's guide Wide bandwidth plus good c.m.r.r. Joules Watt Dedicated instrumentation controller for Nanno Herder theSC84and other computers SUPERCONDUCTING FETS 850 T.I. Vellacott STEP-UP SWITCHING REGULATOR NOVEL POWER SUPPLY 885 PC BUS PERFORMANCE 891 ASSERT COMPETITION 918 856 High -efficiency design for use with NiCd SCI -TECH '89 918 Two new personal computers use entirely cells. OBITUARY 918 new bus structures. N.J. Chaffey and T.A. Perkins William Nowlin 7`a'VON 11111 L.F. NAVIGATION REVIVAL LOGIC PROBE 897 COMMENT 843 867 Tracking vehicles by radio EVENTS 854, 881 Fast pulse -detecting probe based on a p.l.d. Richard Lambley B.J.Frost LETTERS 860 DEPENDENT SOURCE CIRCUIT IDEAS 864 PIONEERS THEOREM BOOKS 869 873 900 APPLICATIONS SUMMARY 871 Alec Reeves, inventor of p.c.m. Finding equivalent generators in a network SATELLITE SYSTEMS 903 W.A. Atherton which has no independent sources Harry E. Stockman TELECOMMS TOPICS 908 MULTIPROCESSOR NEW PRODUCTS 920, 927 PIEZOELECTRIC COAXIAL SYSTEMS RESEARCH NOTES 929 CABLE 875 905 TELEVISION BROADCAST 932 This third article examines the issues RADIO COMMUNICATIONS 934 involved in linking processors together Applications of a novel composite material Alan Clements Peter Johnson RADIO BROADCAST 936

ELECTRONICS & WIRELESS WORLD 841 TAYLORRF/VIDEO MEASUREMENT INSTRUMENTS

UNAOHM EP741FMS MEASUREMENTS FIELD STRENGTH METER/SPECTRUM ANALYZER Frequency Continuously adjustable via a geared -down vernier as follows MADE EASY Range: IF 38.9MHz Band I 46 to 106MHz FM Band 88 to 108MHz Band III 106 to 290MHz Band H 290 to 460MHz Band U 460 to 860MHz Frequency TV Bands -4 digit counter with 100KHz resolution Reading: FM Band - 5 digit counter with 10KHz resolution Reading Accuracy: reference Xtal +/-1 digit. Function: NORMAL: picture only

TV Monitor ZOOM : 2 to 1horizontal magnification of picture picture + line sync pulse (with chromaburst if TV signal is coded for colour] Panorama: panoramic display of the frequency spectrum within the selected band and of tuning marker Panorama Adjustable expansion of a portion of the spectrum around the tuned Expansion: frequency. Analogue 20 to 40dB. Static measurement of received signal. Scale calib- Measurement: rated in dBuV [at top of picture tube] to rms value of signal level. DC/AC Voltmeter: 5 to 50V Measurement 20 to 130dBuV in ten 10dB attenuation steps for all bands. Range: -60 to 130dBuV in nine 10dB steps for IF. Measurement ANALOGUE: brightnessstripeagainst calibratedscale Indication: superimposed on picture tube. The stripe length is proportional to the sync peak of the video signal. Video Output: BNC connector 1Vpp max on 75 ohm. DC Output: +12V/50mA max. Power supply source for boosters & converter TV Receiver: tunes in and displays CCIR system 1 TV signals. Other standards upon request. Additional (1] Video input 75 Ohm. [2] 12V input for external car battery. Features: (3] Output connector for stereo earphones. Price: £1344.00 exc. VAT and Carriage.

UNAOHM FSM5987 T.V. FIELD STRENGTH METER INPUT Sensitivity: from 20dBuV to 110dBuV (-40dBmV to 50dBmV) or 10uV to 0.3V, in eight 10dB steps. Reading: dB reading proportional to peak value for video signals; proportional to mean value for AM or FM sound signals. For botn signals scale calibrated to rms value and expressed in dBuV Two mo-e scales are available: volt from 0 to 50, and ohm from 0 to 21300 ohm. Battery status is also provided. Accuracy: +/- 3dB for bands I & III +/- 6dB for bands H & IVN Impedance: 75 ohm unbalanced; DC component blocked up to 100V FREQUENCY

Range: 46 to 860 MHz as follows: Band I 46 to 106MHz III 106 to 206MHz H 2C6 to 460MHz IVN 460 to 860 MHz Reading: 4 digit LCD readout. 100KHz resolution Price: £378.00 exc. VAT and Carriage.

UNAOHM EH 1000 TELETEXT AND VIDEO ANALYZER Function: Eye Pattern: display of RF and video -frequency teletext signals by means of eye pattern diagrams both in linear representation and lissalous figures (0 and X). Line selection: display of video signals and line by line selection. Measurement of modulation depth. Teletext: monitoring of teletext pages. RF Input: Freq. Range: 45 to 860MHz. Frequency synthesis, 99 channel recall facility, 50KHz resolution, 30 channel digital memory. Level: 40 to 120dBuV: attenuator continuously adjustable. Indication of the minimum level for a correct operation of the instrument. Impedance: 75 ohm. Connector type: BNC. Video FrequencyMinimum Voltage: 1Vpp. Impedance: 75 ohm or 10K ohm in case Input: of a through -signal. Connector type: BNC. Teletext Input: Voltage: 1Vpp/75 ohm. Teletext Clock Voltage: 1Vpp/75 ohm. Measurement, Aperture of eye pattern: Input: linear or Lissalous figures, selectable. Indication: directly on the picture tube. A calibrated scale shows percentage of eye pattern aperture. Error: the instrument introduces an error of < 5% with video input and 20% with RF input. Jitter on regen'd clock: <25ns. Line selector: Selection of any TV line between the 2nd and the 625th scanning cycle by means of a 3 digit thumbwheel switch. Oscilloscope: VERTICAL CHANNEL: Sensitivity: 0.5 to 2Vpp/cm. Frequency Response: DC to 10MHz. Rise time: pre & overshoot < 2%. Input TAYLOR BROS (OLDHAM) LTD. Coupling: AC. Input Impedance: 75 ohm/50pF. TIME BASE: Sweep Range: 20 to 10ms (1.1/2 frames); 32; BISLEY STREET WORKS, LEE STREET, 64/192us [1/2; 1; 3 lines]. Linearity: +/-3%. Horizontal Width: OLDHAM, ENGLAND. 10 divisions; x5 magnification VISA TEL: 061-652 3221TELEX: 669911FAX: 061-626 1736 Price: £1870.20 exc. VAT and Carriage.

ENTER 40 ON REPLY CARD COMMENT Predicting the unpredictable

How technological advancements will affect the future is remarkably difficult to EDITOR predict. There is no need to go back to the industrial revolution to find evidence of this Philip Darrington statement. As many of you will remember, not too many years ago experts predicted EDITOR - INDUSTRY INSIGHT that the country would soon be run by a big brother computer. Geoffrey Shorter, B.Sc. Were it not for microprocessors we might now have a big brother. Admittedly there 01-661 8639 are a few large central computers doing mainly specific tasks, and the day might still come when our destinies are determined by a central supercomputer, but the majority DEPUTY EDITOR of today's processing is done locally - in offices. laboratories, shops, factories and in Martin Eccles 01-6618638 the home. And, on the subject of predictions, who can say with any certainty whether COMMUNICATIONS EDITOR computers will eventually create jobs or cause even more unemployment? Popular Richard Lambley answers to this question are frequently evaluated from political rather than computer 01-661 3039 knowledge, which is perhaps what flawed the central -computer theory. ILLUSTRATION One of the bolder predictions made recently comes from researchers at the Georgia Roger Goodman Institute of Technology who say that by the year 2000, operators will be instructing 01-661 8690 computers in plain language, not by entering commands on a keyboard. That in itself DESIGN & PRODUCTION is not a particularly profound prediction, but researcher David Roessner goes on to Alan Kerr make a point with much wider implications. As a result of advances in computer 01-661 8676 technology, and in particular in the computer -to -person interface. he says that we will ADVERTISEMENT MANAGER be "thrown back on those skills that are uniquely human - skills such as knowing what Martin Perry questions to ask, how to interpret information, and how to judge when a 01-661 3130 computer -generated answer does not make sense." ADVERTISEMENT EXECUTIVE Our schools are certainly working hard at 'computer -education'. but might James Sherrington emphasis be turning away from teaching the disciplines of computer technology and 01-661 8640 programming -which is essentially problem solving - towards training in how to type CLASSIFIED SALES EXECUTIVE and how to use programs such as word processors, data bases and spread sheets? One Peter Hamilton hopes not. but since it has become so clear that the health of a nation relies on the 01-661 3033 success of its industry and commerce such a situation is justifiable should you put the ADVERTISING PRODUCTION long-term future second to current needs. Brian Bannister Getting and holding a job in the future, says Roessner, will require literacy, not 01-661 8648 computer literacy. If he is right, there will be problems for everyone should we decide Clare Hampton to train computer use rather than continue to teach problem solving using 01-661 8649 computers. Young people will leave school expecting to use their hard-earned training and be disappointed, employers will find a shortage of suitable staff, and the economy MARKETING EXECUTIVE will suffer through the resulting short -fall in production. Rob Ferguson Of course. nothing indicates that every future worker will need to be a computer 01-661 8679 programmer. It might be that our current information -technology managers and PUBLISHER computer programmers will evolve side by side. and jobs for everyone else might Susan Downey suddenly appear, be created, or never have disappeared in the first place. 01-661 8452 Two things are certain from this reminder that new technology might not produce the results that seem immediately apparent. One is that is that any child emerging REED from school with the ability to solve problems will make a better contribution to BUSINESS society than one emerging with a sound knowledge of how current computer PUBLISHING programs work, and the other is that any unbiased prediction of the effects of new technology is better than none.

Electrinars & Winless Worldispublishedmonthly rant Subscription Services. Oaklield House. Perrymount USPS687540. By post, current issue £2.25. hack issuesif Road. Ilaywards Heath. Sussex RH163 MI. Telephone 0444 available, £2.50. Order and payments to 301 Electronics 441212. Please notify a change of address. USA: $116.00 and Warless World. Quadrant House, The Quadrant. Sut- airmail. Reed Business Publishing [USA,. Subscriptions ton. Surrey SM2 5AS. Cheques should be payable to Reed Office. 205 E. 42nd Street. NY 10117. Overseas advertis- BusinessPublishingLtd.Editorial & Advertising ing agents: France and Belgium: Pierre Mussard, 18-20 offices:EWW Quadrant House. The Quadrant. Sutton, Sur- Place de la Madeleine. Paris 75008. United States of rey SM2 5AS. Telephones: Editorial 01-661 3614. Adver- America:Jay Feinman. Reed Business Publishing Ltd. 205 tising 01-661 313001-661 8469 Telex: 892084 REED BP East 42nd Street, New York. NY 10017. Telephone 12121 EEP Facsimile: 01-661 :19414 (Croups II & 111, Beeline: 867-2080 Telex 2:1827. USA mailing agents: Mercury Air - 01-661 8978 or 01-661 8986.:100 baud. 7 data bits. even freightInternationalLtd.Inc..10,10 Englehard Ave. parity. ale stop -bit. Send ctrl -Q. then EWW to start; NNNN Avenel N.J. 07001. 2nd class postage paid at Rahway NJ. to sign off. Newstrade -- Quadrant Publishing Services No. Postmaster - send address to the above. 01-661 :3240. Subscription rates:Iyear ,normal rate, I:23.40 UK and V.94.50 outside UK. Subscriptions: Quad- ©Reed Business Publishing I.td 1988. ISSN 0266-3244

ELECTRONICS & WIRELESS WORLD 843 "It's a pretty small battery -powered PROM programmer - sowhat?" Tools which are convenient get used alot - that justifies 0 "I'm bound to let the battery go flat." their existence. Thereis no waywe could I.Quite so. But in practice it doesn't matter. S3 switches explain all the usefulness of S3 here. off after a half-hour of non-use anyway, or when the Instead, if you're interested we're tr battery gets low. You don't lose your data. Then a going to let you see it, use it low -charge overnight or boost -charge for three and evaluate it in your own hours will restore full capacity. You can keep using workshop. We went to a lot !t when charging. So there really is no problem. of trouble to design S3 just the wayitis - no other PROMMER is all CMOS and "I already have a programmer." all SMT. So we must be con- Pity it doesn't have S3 features, eh? But vinced that S3 would be a for- here's a trick worth knowing. If you plug midable addition to your S3's EMULead into the master socket of a armoury. Now all we have to do ganger then you get an S3 with gang is to convince you. capacity.Isn'tproductionseparate from development anyway? "Such a little thing can't be powerful, like a big bench - "It looks nice. Will I be programmer - er - can it?" disappointed?" Dataman tools are designed to Yes, it can. It is more powerful. S3 leaves be used by Engineers. Not other prommers streets behind. S3 has justsoldto Management. continuous memory, which means that you Have you ever been misled can pick it up and carry -on where you left off by some mouthwatering last week. S3 has a huge library EPROMS and ad for a new product? EEPROMS. S3 can blow a hundred or more Great artwork and ex- PROMS without recharging. S3 also works re- citing promises which motely, via RS232. There s a DB25 socket on the feed your fancy? On back. All commands are available from your computer impulse you buy and (through a modem, even). Also S3 helps you develop when the thing arrives and debug microsystems by memory -emulation. you feel let down. The pic- ture looked better. The claims "What's this memory -emulation, then?" arehardly justified;not exactly It's a technique for Microprocessor Prototype Develop- misrepresentation,just ment, more powerful than ROM emulation, especially poor implementation. useful for single -chip "piggy But you've boughtit. back" micros. You plug the And you're stuck with it. lead with the 24/28 pin header It stays in the cupboard, in place of the ROM/RAM. most of the time. So how You cliptheFlying -Write - about this: buy S3 and Lead to the microprocessor use it for up to a month. and you're in business. The Softy3 is here! If you're not still thrilled code is entered using either then you can have your the keyboard ortheserial money back. interface. Computer -assembled files are downloaded in standard format - ASCII, BINARY, INTELHEX, MOTOROLA, TEKHEX. "Refund in the first month! How can you offer Your microprocessor can WRITE to S3 as well as READ. You that?" can edit your variables and stack as well as your program, if We trust S3 to fire your enthusiasm. We trust you not to use us you keep them all in S3. as a free hire -service. We bet you won't send it back. How S3 can look like any PROM up to 64K bytes, 25 or 27 series. would you manage without it? Access is l(X)ns - that's really fast. Memory -emulation is cheap, it's universal and the prototype works "like the real thing". "These things cost a fortune and take months to arrive." We wouldn't get you all excited and then let you down. It Costs S3 loads its working programs out of a £495plus VAT. That includes P & P, Charger, EMULead, Write Lead and a HELP program in ROM. S3 is in stock. Buy PROM in its socket, like a computer it today. Use it tomorrow. (That's a fair promise. But please loads from disk. Software expansion is reserve product by phone or telex to make it come true). unlimited. Upgrades will come in a PROM. Programs can be exchanged between users. How's that for upgradability? DAIAribin Lombard House, "Can I change the way it works?" Cornwall Rd. You surely can. We keep no secrets. System Variables can he "fiddled." New programming algorithms can be written from DORCHESTER the keyboard. Voltages are set in software by DACs. If you Dorset DT1 1 RX. want to $et in deeper, a Developers' Manual is in preparation Phone 0305 68066 Telex 418442

which will give source -code, BIOS calls, circuit -diagrams, etc. Ifyou purchase while this ad is current, you have 28 days to We expect a lively trade in third -party software e.g. dis- examine the goods and return them for refund. Carriage will be assemblers, break -point -setters and single -steppers for various charged at cost. The right to charge the cost of refurbishment VISA micros. We will support a User Group. of damaged goods is reserved. ENTER 50 ON REPLY CARD

844 ELECTRONICS & WIRELESS WORLD Eureka 95-aworld standard? Research teams all over Europe are racing to make ready a crucial h.d.tv demonstration

TOM IVALL

demonstration to be held ware. The race results from the at Brighton in September need to meet an important dead- ill form a significant step line - the next plenary assembly inthe European attempt to of the CCIR in May 1990. As a establish a compatible high - permanent body of the ITU, the definition television stand- CCIR is the world organization ard. It could also be crucial which makes international de- in an international decision. cisions on broadcast engineering to be made eventually by the standards. CCIR. on whether this standard Eureka 95 made a late start in will be acceptable as a world the h.d.tv stakes because the h.d.tv standard. collaborative organization was The demonstration is being only formed in 1986, immed- organized by member countries iately after the last CCIR plenary responsible for the Eureka EU95 assembly heldinDubrovnik. h.d.tv project' (an outline of this Essentiallyit was a European collaborative European scheme reaction to the possibility that was given in the March 1988 the NHK non -compatible issue. p.294). It will take place at 1125/60/2:1h.d.tv standard the site of the International could become a de facto world Broadcasting Convention, 23-27 standard for broadcasting. This September. but will not be an was the only working h.d.tv official part of the conventionBosch h.d.tv camera for Eureka 95 system (see July issue, 708710 system offered as a candidate at and will not be open to all IBCfor a description). Dubrovnik and was officially visitors.Ithas a limited ob- supported by the USA. Japan, jective: to demonstrate a working chain of Now, digital signal processing has adv- Canada. Brazil and Chile.Itincludes a hardware based on an interim h.d.tv produc- anced to such an extent, and its cost reduced bandwidth -compression technique called ion standard of 1250 lines. 50 fields per through v.I.s.i. devices, that all three can be Muse (multiple sub-Nyquist sampling second and a 2:1 interlacing factor. different from each other where it serves a encoding' outlined in the December 1984 This hardware is designed asif for a practical purpose. For example, large -area issue of E&WW, p.38. compatible broadcasting system - an essen- flicker, resulting from a combination of field Most European delegates at Dubrovnik ial feature of the European proposal. The rate and screen brightness, is exclusively a strongly opposed this 'revolutionary' non - compatibility will be with the MAC/packet problem of the display standard. It occurs compatible system because they felt it would d.b.s. transmissions to be started soon in with screen areas subtending a large angle at be disastrous for Europe. A major objection Europe (e.g. in Britain from the BSB satel- the eye because the outer part of the retina is was the incompatible 60Hz field rate. They lite now being prepared for launch). Since more sensitive to flicker than the fovea or stressed that they wanted an 'evolutionary' the MAC d.b.s. signals will be displayed central part. Component manufacturers are approach to h.d.tv starting from the other through MAC decoders on existing standard therefore now beginning to supply chip sets end - the existing base of PAL and SECAM PAL and SECAM television sets. the EU95with digital field memories for receivers to receivers in Europe. These millions of 50Hz h.d.tv transmissions would therefore be enable incoming 50 field's transmission receivers were not only a huge investment compatible with these 625/50/2:1 receivers. standard pictures to be displayed at 100Hz in domestic equipment which should be And, of course, the h.d.tv pictures transmit- field rate in order to eliminate this flicker. utilized instead of ignored: in a compatible ted via the d.b.s. channels would also be system they would also provide an displayed on new high -definition television HISTORICAL PERSPECTIVE immediate audience for the firsth.d.tv sets as and when these became available. programmes - before new h.d. receivers Demonstration of the interim production As reported in March, the Eureka 95 col- became generally available - and thus give standard at Brighton is described as a "li- laborators are proposing a single worlda commercial incentiveto programme mited objective" because it is only one step digital production standard of 1152/50/1:1 companies to produce material for the new on the way to a complete and viable system. (sequential scan) with a 16:9 aspect ratio and medium. In the past the television production stan- 1920 samples per active line for luminance As a result of this disagreement the 1986 dard was the same as the transmission (960 for colour). At Brighton they will only CCIR meeting ended in a stalemate on the standard and the receiver display standard. demonstrate an interim production stan-question of a world standard. The plenary Then standards converters working be- dard because it is as far as they can get in a assembly decided to defer a decision on tween, say 525 and 625 -line systems, showed race against time. An earlier demonstration, h.d.tv.It simply issued a report. No 801. that a production standard need not, in fact. at the 1987 Berlin radio and tv show. wasgiving details of the proposed 1125/60/2:1 be the same as the transmission (= display) little more than a statement of intent and did standard and adding a footnote expressing standard. not include any encoding/decoding hard- reservations. Even before the Dubrovnik

ELECTRONICS & WIRELESS WORLD 845 meeting there had been discussions between Another general problem already studied CRITERIA FOR HIGH DEFINITION like-minded European broadcasters, equip- by the CCIR is that of finding sufficient ment makers and government officials on A primary question that has to be considered bandwidth for world-wide h.d.tv services in the possibility of establishing an alternative by all these teams is: what is high -definition the satellite broadcasting frequency alloca- h.d.tv standard. The effect of the plenary television supposed to be? Or, more precise- tions at present available. These allocations assembly was to turn these thoughts into ly, what performance do we need from h.d.tv are at 12GHz, 23GHz, 42GHz and 85GHz. action. to justify the effort and cost of developing it? The 12GHz allocation is available for all ITU Immediately afterwards, four European Fortunately, all countries in the world con- regions and is planned for analogue trans- companies with interestsintelevision cerned with h.d.tv, regardless of support for missions in 24 or 27MHz channels. It allows broadcasting equipment and receivers gotdifferent systems, seem to agree on this. basebands of a maximum of 12MHz. So with together to formulate a definite proposal for Everyone recognizes that a large improve- h.d.tv production standards requiring initial an alternative standard and the development ment in picture quality must be achieved to vision bandwidths in the region of 30 to of equipment to demonstrate it. These were make it worthwhile. 60MHz (depending on the interlace factor, Bosch (West Germany), Philips (Nether- CCIR report No801 formally states that, 2:1 or 1:1), considerable bandwidth com- lands), Thomson (France) and Thorn -EMIrelativelyto existingtv systems, h.d.tv pression is necessary for transmission in (UK). To obtain EEC backing and financial should have twice the vertical and horizontal these r.f. channels. support, the proposal was put to a June 1986 resolution (thus four times the picture More attractive is the greater bandwidth conference of EEC ministers concerned with information), with separate luminance and available at 22.5 - 23GHz. This 500MHz, the Eureka scheme, which was founded in colour -difference signals and improved col- however, is available for satellite broadcast- 1985 for co-operation on advanced technolo- our rendition. Also it should have pictures of ing only in Regions 2 and 3, not Europe in gy (E&WW April 1986, p.7). It was acceptedwider aspect ratio. Here, everyone seems to Region 1. So there would have to be a new by the Eureka ministers and given the agree that a 16:9 aspect ratio is desirable. At international agreement to allow it to be project number EU95. A first meeting of the a given viewing distance from the screen, a used world-wide. Here, estimates have been new h.d.tv consortium was held in Octoberwider picture than in conventional televi- made that a possible r.f. channel bandwidth 1986 and included government officials sion sets makes the viewer feel more in-of about 40MHz would allow two h.d.tv from the principal countries concerned,volved with the programme material, poss- channels per country and that signal base - France, Germany, Netherlands and UK. La- ibly because there has to be more movement bands could be about 20MHz, again necessi- ter, Belgium, Italy, Sweden and Switzerland of the eyes to take in all the picture content. tating some degree of bandwidth com- joined as secondary, or 'B' participants. There seems to be general accord here that a pression. The extremely urgent research and de- viewing distance of three times the picture In the 40.5-42.5GHz and 84-86GHz velopment effort needed to catch up with the height (3H)is optimum, as against the allocations, rain attenuation is a serious formidable NHK/Sony engineering achieve- typical 6H of conventional viewing. Finally, problem and much more development ment in h.d.tv -a product of some ten years' the CCIR report specifies multi -channel would be needed to make these two bands work - is being supplied by eleven teams in high-fidelity sound. suitable for h.d.tv. All in all, says the CCIR, different countries. These are covering fun- In general the Eureka 95 project is aiming for h.d.tv on a world-wide basis there is a damentals and psycho -physics, production at a resolution of about 440 000 pixels in the requirement for an all -region BSS allocation standards and conversions, studio equip- 16:9 format (compared with about 110 000 of about 500MHz, preferably not above ment, transmission, MAC encoding/ pixels in a typical 4:3 PAUSECAM receiver). 23GHz. The second part of the latest WARC decoding, display standards, receivers, home This would be given by 900 horizontal pixels devoted to the geostationary satellite orbit. video recorders and players, programme and 490 vertical pixels. Ideally the receiver which was started in 1985 (see December material, bit -rate reduction, and overall co- display should have a screen area of about 1985 issue), is now being held in Geneva, but ordination. 0.8m2. this is not constituted to make any substan-

Two 54 MHz Two 13.5MHz sampling sampling 1250/50/2!1 625/50/21 Sound data 1250/50/2:1 frequencies frequencies quincunx pattern Vtr or telec mi Digitization Two 2-D titers shcpe / Two Selection of L To d.tIs picture at 54MHz spectra for re -samplers moving or / Line MAC MAC satellite sources sampling moving and at static shut fler encoder multiplexeruplink (interlaced) frequency static detail 13 5MHz branches notional)

Analogue 8- bi Digital assistance data video digital video r

Digital assistance data

1250/100/2:1 54 MHz /Interpolation H d tv Mode L Fromdbs or static and D -to -a Field up- display selection moving modes LouJ satellite (interlaced) converter converter (static or removes repea de-shuffler demul* :Jexer (unlink 16 9 moving) spectra 7 notional) 1250/100/2 1 54 MHz 129/50/2:1 625/50/21 (1013MHz) (13 SMH2 sampling Sound data frequency) 1250/50/2:1 Hdtv display D- to -a 1250/50/2 1 PAL /SECAM MAC MAC From d bs satellite downlink (interlaced) converter iv set (4 3) decoder demultiplexer (notional) 16 9

Composite signal

Fig.1. Simplified schematic of Eureka EU95 compatible h.d.tv encoding/decoding demonstration chain, based on interim production standard of 1250/50/2:1. Only luminance digital processing is shown.

846 ELECTRONICS St WIRELESS WORLD tial changes in the d.b.s. allocations. Howev- er, the feasibility of making the 22.5 1250/50/21 format Samples in sequence of 625/50/2:1 format band into a world-wide allocation is odd field four fields11,2,3,41 1 3 1 3 likely to be considered at this Geneva confer- 1, 3, 1,3 Yinfielo ence. 4 2

3 3 1 EUREKA 95 PRODUCTION STANDARD 2,4, 2,4 The equipment to be demonstrated at 2 4 Brighton assumes compatible transmission 1 3 1 3 in the 12GHz world-wide d.b.s. allocation. 2 4 2 An outline of the chain of hardware based on the 1250/50/2:1 interim production stan- 3 1 3 dard is shown in Fig.1. For simplicity only the luminance signal processing is shown. Fig.2. Line shuffling technique combines samples as shown to convert 1250'50,2:1 Broadly, this chain isbuilt around two signal into 625 502:1compatible signal. Numbers indicate both sample positions established international broadcast en- and successive fields in which these samples occw. gineering standards. One is the CCIR 4:2:2 digital coding standard for 625 -line studio 64p s 0 -MAC and 02 -MAC equipment, with sampling frequencies of digital assistance data 13.5MHz for luminance (y) and 6.75MHz for the two colour components (u and v). All the digital signal processing is related to these Verticalblanking interval sampling frequencies and has eight -bit re- 21 lines solution (256 quantization levels). The second broadcast engineering stan- 625 lines dard is the MAC/packet family of transmis- sion systems3 adopted for d.b.s. by the EBU Line 625sync and and recognized by the CCIR. In the Eureka 1 )service ident. data 95 scheme it is being employed as a develop- ment from HD -MAC, which itself followed from the earlier extended- or E -MAC, or Digital sound and data Vision signal enhanced C -MAC proposal (see E&WW De- 164 packets of 751 bits multiplexed analogue components cember 1984 p.37, and February 1986, p.7). . for 16.9 and 4.3 pictures Essentially the Eureka 95 version provides Fig.3. D MACformat of Eureka 95 compatible h.d.tvsignaI (not to scale). the extra vision information (pixels) needed for the 16:9 h.d.tv pictures, while allowing conventional PAUSECAM receivers with logue video signals in component form. This Fig.4, which is an elaboration of this part of MAC decoders to use only the information working standard was chosen because its Fig.1. appropriate for their 4:3 pictures in a com- simple relationship to the 625 -line television The reduced -bandwidth signals from the patible fashion. Extra digital information to standard allows efficient and economicalfilters are then re -sampled at a lower fre- assist the receiver, called digital assistance conversion. At a later stage a sequential quency, namely the 13.5MHz CCIR digital data, is transmitted as well. From the EBUsource will be introduced to give greatercoding frequency for luminance. What are MAC family, Eureka 95 will be compatiblevertical resolution and better digital proces-being re -sampled here are the eight -bit with both the D -MAC standard as intendedsing performance. At the demonstration, representations of the signals. Re -sampling for Britain's d.b.s.4, and the D2 -MAC ver- Thomson will show a 1250/50/1:1 camera asat a lower rate, called sub -sampling, has the sion, intended for cable television systems. an example. effect of spreading the samples over a longer In studying Fig.1, some readers may be Analogue luminance signals from theperiod of time, in this case over four fields. It puzzled by the block marked '2-D filters' source are digitized to eight -bit resolution at is effective for bandwidth compression with (two-dimensional filters). This term derives a sampling rate of 54MHz. This is four timesstationary pictures and static parts of pic- from the concept that television pictures are the CCIR digital coding sampling rate oftures containing movement but introduces a distributions of visual information in space 13.5MHz for luminance and has been chosen loss of resolution on moving parts. So the and time. More precisely, the individual because of the 4:1 bandwidth compressiontwo sub -sampled signals are next passed into pixels in a continuing sequence of pictures that follows, thus retaining the CCIR codinga section of the bandwidth -compression can be located inrelation to a three - standard. system that exploits the eye's insensitivity to high spatial frequencies on moving parts of dimension set of co-ordinates: horizontal, BANDWIDTH COMPRESSION vertical and times the picture. The purpose of this section is to In this context, a conventional filter such The next four blocks of Fig.1 are concernedselect dynamically from the two filtered as a low-pass type, whether analogue orwith bandwidth compression and conver-inputs an optimum signal for transmission, digital, is only a one-dimensional filter. If sion to a 625 -line signal format. Bandwidth depending on the nature of the scene con- connected in a video circuit it simply mod- compression is based on the general princi-tent. It produces a digital assistance signal ifies the vision bandwidth and therefore, on ple of first removing redundant visual in-which carries instructions for controlling a the displayed picture, alters only the hori- formation from the picture and then spread- decoding system in the receiver (see later). zontal resolution. ing selected portions of the resulting video At this point the luminance and colour A 3-D filter, which requires field delays, information over an extended period of time.components are still on the 1250/50/2:1 shapes the bandwidth horizontally, vertical- This follows the Hartley -Shannon theory on standard, though in sampled and digitized ly and temporally, so that useful bandwidth the maximum communications capacity of aform. The samples of the sub -sampled signal is represented by a volume. channel in bit/s: a trade between bandwidth, are distributed over four fields as shown in Thus a 2-D filter operates in any two oftime and signal/noise ratio is possible. the middle part of Fig.2. Here the positions these three dimensions. Sampling is applic- Here the redundant information that isof the samples are marked by numbers. Each able toallthree dimensions. Indeedit discarded consists of diagonal image fre-number (1,2,3,4) indicates the field, in a already exists in one dimension in conven-quencies and components of scene move-time sequence of four, in which that particu- tional television - the vertical sampling of ment in which the eye is not sensitive to fine lar sample has been placed by the sub - the picture by the scanning lines. detail. Two 2-D filters perform this spectrumsampling process. It will be seen that the In Fig.1 a picture source working on the shaping task. Their mode of operation will besamples are arranged in a quincunx pattern interim production standard generates ana- described in more detail later with the aid of(like the arrangement of five dots on one face

ELECTRONICS & WIRELESS WORLD 847 wpw Video at 13.5MHz sampliig frequency Re -sampler (optimun for static areas) at 13 5 MHz

Grp., Local reconstruction 2-D filter (vertical - temporal) Error SchTr lcto- measure 8 -bit digital Selection of Combiner 8 bit digital idea 13.5MHz Original digital signal smallest and video 54MHz coding error encoder sampling sampling frequency frequency Error measure 2-D filter (spatial) Locol reconstruction

Re -sampler at 135 MHz Video at 13.5 MHz sampling frequency (optimum for moving areas) Digital assistance data

Fig.4. Motion -adaptive bandwidth -compression algorithm used in 1250/50/2:1 encoding chain. This functional diagram is a more detailed version of the third, fourth and fifth blocks of the encoding chain in Fig.1. Interpolators correspond to those in Fig.1. of a gaming die), a result of the diagonal dered to improve the signal/noise perform- there are two reduced -bandwidth signals. filtering. The process is similar to that used ance. One gives good resolution on stationary in the NHK Muse system. After the MAC encoding of the v. u and v pictures but poor resolution on movement, Next, the 1250 -line signal is converted video components they and the digital sound i.e. blurring. The other gives only moderate into a 625 -line format. This is done by a and data packets are time -division multi-resolution on both stationary and moving process called line shuffling: the principle is plexed to produce the complete high - pictures. illustrated in Fig.2. Solid lines indicate one definition MAC waveform for modulating One or other of these two signalsis field while the broken lines indicate the next the transmitter. At this point the digital automatically selected for transmission - field interlaced with it. As can be seen, in a assistance data signal mentioned above is and this is the motion -adaptive part of the four -field sequence the line shuffler re- also included in the multiplex. This repre- system. To decide which is the better at a arranges samples from two successive lines sents a data rate of about 1.1Mbit/s and is given moment, the total picture is divided in each field of the 1250/50/2:1 picture into inserted in the 21 lines of vertical blanking into a large number of small blocks. Within one line of a 625/50/2:1 picture. Thus sam- period for D -MAC and D2 -MAC compatible each block the system first reconstructs two ples from odd -numbered fields (1,3) are transmissions (Fig.3). displayable versions from the two re - transferred into one 625 field while samples The receiving/decoding chain in Fig.1 is sampled signals. This is done by the two from even -numbered fields (2,4) go into the almost self-explanatory asit reverses the interpolators shown in the diagram. It then next, interlaced, 625 field. processes described above for the encoding/ compares these two local reconstructions of After this line shuffling, the resulting transmitting chain. Two alternative 1250 - the block with the corresponding part of the 625/50/2:1 luminance signal shown in Fig.1 line h.d.tv displays are available, one with incoming signal. This is done by the subtrac- passes into a MAC encoder as the v compo- 50Hz field rate and the other with 100Hztors shown, which give the accumulated nent, along with the u and v colour compo- field rate. Reception of the compatible sig- difference, or error, between the original nents (not shown), of a complete video nals on existing PAUSECAM television sets and the reconstruction. The two errors are signal. The v. u and v components are time is indicated at the bottom right. Here, the measured; and the version of the block compressed and arranged in time -division MAC decoder, in addition to expanding the which shows the smaller error, i.e. the better multiplex, all by digital signal processing. time -compressed analogue vision compo- rendition of the original picture, is selected Extra picture informationis,of course, nents, also receives a data signal telling itfor transmission. generated with the wider, 16:9 h.d.tv aspect what portion of the 16:9 picture to select to In stationary areas this system uses four ratio relative to the standard 4:3 aspect ratio. form the standard 4:3 PAUSECAM picture. fields of samples (Fig.2) to reconstruct an In the high -definition MAC encoding equip- image of high spatial resolution but poor MOTION -ADAPTIVE ENCODING ment contributed by the IBA thisis temporal resolution. In moving images it accommodated by time compressing the Returning to the bandwidth -compression uses one field of samples to reconstruct each luminance by a greater amount -a factor of part of the system, the main functions of thisimage, resulting in reduced spatial resolu- 2:1 (and colour components 4:1) instead of encoding algorithm are shown in more tion but good temporal resolution. the 3:2 factor (colour components 2:1) used detailinFig.4.Itisa motion -adaptive If the receiveristo display optimum in a conventional D -MAC encoder. scheme producing digital assistance signals pictures by reconstruction from the As a result of these higher compression for transmission to the receiving system.6 selected, more accurate, blocks, it must be ratios the image frequencies of the analogue The incoming eight -bit digital luminance'told' for each block which of the two 2-D components multiplexed in the transmis- signal with a sampling rate of 54MHz isfiltering processes has been used in the sion signal are increased correspondingly. applied to two 2-D filters for bandwidth motion -adaptive encoder. This is necessary Consequently the high -definition MAC sig- reduction as explained above. One functionsbecause the receiver decoder must apply the nal has a wider baseband width, of about in the vertical and temporal dimensions and reverse process to that of the selected 2-D 10.5MHz, than that of the conventional gives optimum performance for stationary filter in each case. Here the reverse process D -MAC signal, whichis about 8.4MHz. areas while the other functions in the hori- is interpolation, or post -filtering asitis However, this can still be accommodated in zontal and vertical dimensions, or spatialsometimes called (they are functionally the normal d.b.s. 27MHz r.f. channel. Pre - domain, and gives optimum performance forequivalent). and de -emphasis techniques are being consi- moving areas. After re -sampling at 13.5MHz To tell the receiver which of the two

848. ELECTRONICS & WIRELESS WORLD interpolators to apply to the incoming video, to locate several dominant peaks - not just the encoder in Fig.4 sends a digital control one - resulting from the motion of objects signal. Called 'digital assistance' data, this within each block. So several motion vectors control informationis produced by the are measured by each correlation process. A coding -error selection block in Fig.4. As further stage in the method is to assign the shown in Fig.1, it is multiplexed as data in principal motion vectors to particular areas the D -MAC signal and then de -multiplexed of the picture. in the receiving/decoding chain. Experiments have shown that the phase This digital assistance technique, origi- correlation technique does work well. The nally investigated by the BBC Research BBC says that for simple panning and one Department and here adopted in the Philips X velocity moving object, typical vector measurement encoding/decoding algorithm, has two im- (pixels/field period) accuracies of 0.05 pixel can be obtained, and portant benefits. One is that all processing Fig.5 Correlation surface computed from 0.015 pixel by use of a windowing process. decisions are taken at the encoding end. successive mages. as one way of deriving They also say that in most casesitis using the high quality, full bandwidth sig- motion vectors (BBC Research Depart- impossible to detect three independently nals available at the source, rather than at ment). This example results from a camera moving objects. Hardware to implement the the receiver where the signals are compress- pan, where the amount of displacement of technique is being constructed. ed in bandwidth and may be corrupted by the main correlation peak from the origin interference and a relatively poor signal/measures the velocity, here mainly in a WIDE-SCREEN DISPLAY noise ratio. In this way the performance ofhorizontal direction. Whatever h.d.tv standardiseventually the system is enhanced. The second benefit chosen, the spread of any new broadcasting 111 is that the highly complex and expensive services based upon it will depend on the signal processing hardware is concentrated availability of receivers with large, wide at the encoding/transmitting end, so that screens. Most demonstrations so far have the receiver is kept relatively simple and its used projection displays but wide-screen cost minimized. cathode-ray tubes are beginning to appear as MEASURING SCENE MOTION well. To judge from a recently introduced Sony Trinitron tube for h.d.tv, it would seem A serious limitation of this motion -adaptive that these can provide the required aspect bandwidth compression system as it stands ratio of 16:9 but not yet the desirable large is an objectionable loss of resolution on screen area of about 0.8m2. moving areas of the picture which the eye is Useful screen Figure 6 shows the 16:9 screen dimen- able to follow - say a slow sweep of a person's sions of this new tube. From these figures hand. The Brighton demonstration stops Fig.6. Screen dimensions of a new Sony one can calculate that the useful screen area short at this point and does not provides a Trinitron cc lour tube providing a display of is about 0.35m2. Deflection angle is 90° and remedy in the encoding/decoding alorithm. 16:9 aspect ratio. Outside diagonal of the the overall length, following from this, is But the Eureka 95 development teams are tube is 1048mm. 798mm, while the neck diameter is 36.5mm. now addressing this problem and hope to An anode voltage of 32kV is required. The have overcome it by the time of the next Trinitron, of course, has a screen formed by demonstration in late 1989. Figure 5 is an example, a correlationtrios of vertical phosphor stripes, with a The method being adopted is to provide at surface calculated from successive imagescorresponding aperture grille behindit. the transmitting end a refined method of obtained by panning a camera across a Across the 16:9 screen format there are 1861 responding to motion. This will measure scene. Here, the large peak showing high phosphor -stripe R.C.11 trios, while the aper- motion and supply information to the re- correlation occurs at a certain horizontal (X) ture grille has a pitch of 0.45mm. The ceiver that will result in improved resolution velocity, while there is virtually no vertical makers claim a horizontal resolution of on moving areas. (Y) velocity. If there had been no movement more than 1000. lines and a screen lumi- Essentially the refined system will mea- at all (e.g. before panning) the large correla- nance of 95cd/m2. A display monitor con- sure speed and direction of movement in the tion peak would have been stationed in the structed with this tube operates on 1125/60/ picture and will transmit this 'motion vec- middle of the surface at the origin, indicat- 2:1 and has a video bandwidth of 30MHz. tor' information to the receiver. The ing zero horizontal and vertical velocities. In Wide-screen tubes of this kind must measurement will be made in each of the Fig.5 the amount by which the peak is obviously be bulky and heavy (here05kg). small blocks mentioned above and the result displaced from the origin is a measure of the As such they provide a strong incentive to will be sent as data to the receiver via the velocity of the pan. further development of flat -screen colour digital part of the Eureka 95 signal. In the Because only phase information is used, displays for future h.d.tv domestic receivers. receiver the motion vectors will be used to the process is not confused by brightness Work is continuing in this field, for example control digital processing functions which changes and also has good noise immunity. at Philips Research Laboratories. will enable moving areas to be reconstructed It is therefore a robust method of measure- with the same resolution as stationary areas. ment. But as described so faritis only OUTLOOK FOR EUREKA 95 Several techniques for television motion capable of measuring overall motion. Real measurement have been investigated over television picture sequences, of course, con- The success of the Eureka 95 system in the years. One that looks promising at the tain a variety of different movements occur- supporting a possible world h.d.tv standard moment is called phase correlation. Here ring at the same time. will depend mainly on whether it achieves a the correlation measured is between succes- The BBC Research Department has in- satisfactory compromise between the twin sive images. A two-dimensional Fourier vestigated by computer simulation an exten- requirements of compatibility and high transform is performed on each image, the sion of the basic phase correlation principle quality pictures. A compromise cannot be corresponding frequency components are that would be able to measure the motion of avoided. In practice there is no such thing as multiplied together and a reverse Fourier many separate objects in a scene7. In this the perfect compatibility with no impairments transform is done on the resulting array. picture is divided into blocks of, say, 64 whatsoever to the existing broadcast pic- This gives a set of numbers called a 'correla- pixels square. Phase correlationisper- tures on standard receivers. And in picture tion surface', which has a peak atthe formed between corresponding blocks in quality, with the practical limitation im- coordinates corresponding to the shift be- successive pictures. This gives a number of posed by bandwidth on channel capacity, tween the successive images. The correla- correlation surfaces describing the move- perfect definition, equalling the resolution tion surface shows by its shape the direction ment present in different areas of the pic- of the human eye,is unobtainable. Two and velocity of the movement responsible for ture. researchers examining the psycho -physical the shift. Each correlation surface is then searched bases of h.d.tv have concluded8 that if a

ELECTRONICS & WIRELESS WORLD 849 television system were to be "transparent" at Further reading family. Ellt. document Tech 3258. 1986. amended a viewing distance of three times the pictureA useful. though not comprehensive survey of by document Silt i:18. height it would have to operate on a standard European work on h.d.tv is a collection of five 4. M.D. Windram. G.J. Tonge. R.C. Hills. The of at least 2270/80/1:1. This is obviously not papers under the heading EBU Studies on High - 1) -MAC packet transmission system for satellite possible with existing bandwidth con-definition Television, reprinted from the EBU broadcasting in the t.nited Kingdom. ERE' Review (Technical). No227. February 1988. straints. Review (Technical), No219, October 1986. Mainly American h.d.tv work, with some European and 5.G.J. Tonge. Extended definitiontelevision Furthermore, in all practical, bandwidth - through digital processing. Proc. Int. Broadcast- limited systems the two requirements ofJapanese. forms the entire contents of the IEEE Trans. on Consumer Electronics. vol. 34. Nol. ing Convention. 18-21 September 1982. good compatibility and high quality pictures February 1988. Earlier papers on an international 6. R. Storey. HDTV motion -adaptive bandwidth conflict with each other. You can improve front are to be found distributed in the Proceed- reduction using DATV. Proc. 11th Int. Broadcast- one, but only at the expense of the other. ings of the International Broadcasting Conven- ing Convention. 19-2:1September 1986. There are several other requirements tions for 1982. 1984 and 1986 IIEE conference 7. GA Thomas. Television motion measurement which a h.d.tv system has to meet. It must publications). for MTV and other applications. BBC Research allow satisfactory recording on video tape: Department Report RI) 1987/11. Sept. 1987. simple transfer from tape to film and vice 1. R.W. Young. Eureka and production standards 8.1. Childs and R. Melwig. HDTV standard -setting on psycho -physical bases. Ent' Review (Technic versa: the convenient exchange of high - for li.d.tv. Image Technology. December 1987. 527-528. al). No219. October 1986. definition programmes: easy conversion be- 2. Y. Ninomiya et al.. A single -channel h.d.tv 9. R. Hopkins. Advanced television systems. IEEE tween the h.d.tv production standard and Trans. on Consumer Electronics. vol. :It Nol. broadcast system - the !%luse. NI1K Laboratory existing production standards: and straight- February 1988. Some of the systems described Note No:10 '1. 1984. forward transcoding from the h.d.tv produc- here were listedinthe Television Broadcast tion standard to the h.d.tv transmission 3. Specifications of the systems of the MAC/packet column. EW1111*July l N :,age 724. standard (see The h.d.tv studio, E&WW July 1988, p.710). At the present stage of Eureka 95 develop- Superconductive j-fets ment there is a serious problem in obtaining good resolution on movement, as explained It is broadly assumed that many semicon-1Hz, the company says itis developing a above, and this will have to be overcome ductor devices are suitable for use athigher gain j-fet with even lower cryogenic before the system can be properly assessed as cryogenic temperatures. Indeed, manynoise. a whole. In the meantime, a belated recogni- semiconductors may work at cryogenic In addition to superconductivity, there tion in the USA that compatibility is. after temperatures, but few actually offer theare other applicaitons for cryogenic fets, for all, important has given rise to several more sensitivity available at room temperature.NASA, for orbital astronomy, and for the h.d.tv system proposals. Some of these have The junction field-effect transistor, howev-military. All these rely on high -impedance already been outlined in E&WW (see March er, shows little shift in performance oversensors, so they must use fets to gain the 1988 issue. pp.226-229 and 294). Including changes in temperature, and offers a uniqueadvantage of increased sensitivity and dyna- the NHK/Sony system already mentioned. solution for operation at cryogenic tempera-mic range. For example, radio astronomers, no fewer than eight h.d.tv proposals are tures, writes Ed Oxner of Siliconix. who seek and send signals far into the solar currently being reviewed in the USA alone. Most cryogenic instrumentation relies onsystem, have historically pushed the tech- Clearly the Eureka project is up against a lot indium -phosphide or germanium -galliumnology, seeking fets with a 1/f noise voltage of competition. But the demonstration at infrared sensors to monitor activity. Theseof 20nV/VHz at 10Hz at 50K. Today, they Brighton should at least give a better idea of sensors, like the common electret sensor,hope to halve that figure. As the noise what chances it has of becoming interna- present an extremely high impedance. Asvoltage is halved, the signal/noise perform- tionally accepted as a basis for a world long as the sensors/detectors operate at highance of the system is doubled. Therefore. standard. impedances, whether at cryogenic or atfocusing on astronomy, the limits are room temperatures. j-fets should be the firstpushed out by offering double the sensitivity Postscript.Just before going to press. in- choice. of former non-fet systems. formation received from the Eureka HDTV The reason why j-fets outperform bipolar In electrical utility transmission lines, for Directorate at Eindhoven suggested that the transistors when input impedances are highexample, up to 15% of the generated electric demonstration equipment at Brighton is simple. The term noise really defines apower is lost during transmission because of might differ in a few details from that shown power phenomenon, represented as E2/R orresistive wire losses. In fact, the US -based in Fig.1 . However, the interim production 12R. When j-fets are operated with a gatePacific Gas & Electric Company is reported standard and the principles. parameters and voltage, the noise power isreduced byto lose more than $200M each year through techniques to be demonstrated will remain resistance (E2/R). However, for the bipolartransmission resistance.Itis speculated, as described. transistor, which uses a base -drive current,however, that when superconductivity be- In Britain, the DTI has now increased its the noise power is a multiple of this highcomes fully practicable the web of electrical financial support to UK participants by £1.7 resistance (12R). Hence, the j-fet easily out-lines will be replaced with buried tubular million to make a total of 14.8 million. This performs the bipolar transistor when high -cryogenic dewars containing low -voltage, £1.7M will go partly to Quantel Ltd, to impedance sensors are involved. high -current superconductive transmission develop a range of h.d.tv editing and image Problems increase below the temperaturelines engulfed in liquid nitrogen. Conduc- processing equipment, and partly to Philips of liquid nitrogen (77K). At 40K, a phe-tionin zero -resistance superconductive Research Laboratories for research into pic- nomenon known as (silicon) 'carrier freeze -transmission lines, achieved with high cur- ture analysis and coding techniques. out' halts all action of the semiconductor,rents rather than high voltages, would also The 1988 International Broadcasting whether it is a bipolar transistor or a fet. Assave energy by eliminating high -voltage Convention willtake place at Brighton. the critical superconductivity temperaturecorona discharge. The initial costs of such a 23-27 September. Further information ab- rises, transistor action returns. The extent tosystem would be staggering. but these costs out the technical sessions, the exhibition which it returns depends on several factors,must be weighed against the improved effi- and other aspects of the event can be but the most crucial appears to be related tociency that would result in tremendous obtained from the IBC Secretariat. Institu- the doping concentration. energy savings. tion of Electrical Engineers, Savoy Place, Siliconix has responded to the current Other commercial applications could also London WC2R OBL. telephone 01-240 1871. interest in the superconductivity, and issee revolutionary changes. Motors for heavy actively pursuing a low -noise development.machinery that today run with large heat Although already offering a commerciallyexchangers to limit entropy might be sub- The author thanks the MI Technical Cen- available j-fet,the Siliconix Si4338mersed in liquid nitrogen to eliminate the tre. the BBC Engineering Information De- (gm= 750µS, Cgd = 1pF, typically) that offersheat exchangers. Power -station chimneys partment and the IBA Engineering Secretar- outstanding noise performance at 80K ofand acid rain might both disappear. The iat for their valuable help in the preparation 25nV/VHz at 10Hz and of 104nV/VHz atelectric car might become a worthy reality. of this article.

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ELECTRONICS & WIRELESS WORLD 851 IEEE488-to-Z80 interface A dedicated IEEE488 controller and bus buffers greatly simplify the interfacing of instruments to the SC84 and other Z80 -based computers.

T.J. VELLACOTT

John Adams presented his SC84 compu- a valid byte. Signals MUD ('not ready for data') transfer: itis optionally sent with the last ter design in E&WW just over four years and No.w ('not data accepted') are activated by byte and can be used to simplify and speed up ago. In the computer world, this is athe devices for which the byte is intended a command system. long time and most applications for whichuntil the data has been accepted and the Interface -clear command IFe is held active the SC84 would have been considered ideal devices are ready to receive the next byte. by the controller for a specific period. usual- then are now almost universally im- Pull -down open collectors drive the inter- ly only when starting up the bus. Interfaces plemented using PC -compatibles. But SC84 face lines so the logic is active -low. Also, a of slave devices on the bus are activated by still has advantages over the more modern line remains low until all the collectors the HEN command. Many fuller descriptions approach: in particular, it is adaptable, andconnected to it turn off. For this reason. the of the IEEE488 interface standard can be facilities can easily be added on plug-in cardsspeed of transferisdetermined by the found in previous articles in E&Wtt' and designed for a specific purpose, such as thisslowest listening device. elsewhere. IEEE488 interface. Bytes sent on the data lines are either Since the design was first published, thecommands or data. Commands are used by DESIGN SC84 Z80 c.p.u. has been upgraded to the the controller to order the source and At the centre of the design is a TMS9914A. more powerful 64180. which is capable ofdestinationls) of transfer. or (quasi - which connects to the 75160 and 75161 running Z80 software. This article describes asynchronously) to investigate the status of buffers designed specially for IEEE488 inter- hardware, and outlines software require- the devices on the bus. facing. Almost all of the IEEE488 interfacing ments. for an IEEE488 interface based on At any moment, the controller may desig- is performed by the 9914 alone, and it has the original Z80 SC84. It was produced fornate a particular device (including itself) to the particular advantage of being usable as a the satellite -instrument testing facility atbe a 'talker', and others as 'listeners', by controller: other i.cs do not have this capa- Oxford which uses SC84s to perform re- sending the address of the device in the low bility. latively low-level control and data collection five bits along with the appropriate com- Connection of the 9914 to the Z80 bus is to reduce the processor load on a PDP11/23, mand in the high three. Under this condi- done by the remaining three i.cs through the which has overall control of our experi- tion, all those addressed to listen receive SC84 backplane, buffering the bus between ments. Some modifications may be required data from the talker, and send handshaking the 9914 and Z80 and decoding the link- to adapt the interface for use with the 64180. after each byte. Similarly the controller may selectable port -address range of the 9914. Only one modification to the existing set pass control of the whole bus to another For interrupts, the 9914 has an open - of three cards is required so the interfacedevice, but the master controller can regain collector line which in the SC84 connects to board is very easy to install. I wire -wrapped it on demand. line 1$ of the serial timer and interrupt i.c. the prototypes, but constructionis now With five bits for address, why are there (STI) using a spare line on the SC84 back - much simpler since a p.c.b.is available only thirty-one possible addresses, rather plane on the STI card. On other computers (detailslater). For our purposes thethan thirty-two? The reason is that address this should go to a spare interrupt line. The IEEE488 socket was bolted to the end of the 31 (decimal) is used for universal negation- open -collector outputis converted to a Eurocard away from the backplane connec- for example. telling address 31 to listen has voltage level with a resistor to the positive tor, obviating the need for a flying lead the effect of making everything ignore the supply rail. connecting to a header on the card. data (nothing can ignore commands while Line Iti is unused in the basic SC84, and is its interface is active). IEEE BACKGROUND one of the eight lines on the STI that may be If more than 31 devices are required, there programmed either as a parallel i/o port or as Originally, the IEEE488 interfacing stan-are two choices. One isto use another a general-purpose interrupt input. Here I, is dard came from Hewlett-Packard, which is complete interface (not so silly as it sounds) used as an interrupt line, and the STI why itis often referred to as the HPIBand the other, which involves a lot more registers are reprogrammed to allow inter- (Hewlett-Packard interface bus): itis also work. and is probably only possible if build- rupts from this source. known as CPIB (general-purpose interface ing a complete system from scratch, is to use Address decodingisstraightforward. bus). Data passes through the interface in secondary addressing. which effectively di- There are eight registers in the 9914, the bit -parallel, byte -serial form to and from up vides one device into different sections. required one of which is selected by three to thirty slave devices, each with a unique Remaining control lines are used as fol- lines. Texas Instruments' numbering address. One cable connects all slave devices lows. Attention line ATN is activated by the system for buses is somewhat confusing. to the controller. As a parallel printer inter- controller to indicate that the data linessince the least -significant bit for the face, IEEE488 is usually very fast.Itis (No) _s) contain a command. rather than register -select pins is numbered zero, while becoming increasingly common to find data. Service -request signal silo is activated that for the data bus pins is numbered seven. IEEE488 interfaces on equipment including by a slave device to indicate to the controller Since lines connect directly to the oscilloscopes and stepper -motor controllers. that it has a problem. In a normal response, lowest three bits of the address bus, The bus consists of eight datalines the controller asks each device in turn (serial respectively, the eight registers are mapped (1)101,) and control/handshake lines (slot. polling) or in groups of eight(parallel to eight consecutive portsin memory. ATM. EDI. OM. WED. NDAC. irc and KEN). Control polling) which one initiated the service Address lines .5_3 are sent to a 74LS138 line DM ('data valid') is used by the sending request. End -or -identify signal Eui is usually one -of -eight decoder, the highest two. .,7. device to indicate that the data lines contain used to indicate the last byte of a block going to active low mum.: inputs. and the

852 ELECTRONICS & WIRELESS WORLD .5V

2c .5V 2 EEE 488 1 40 connector ov ACC Ra CC 1:5 75160

, 140 - Group select 11 10 A3 m= i 1 A0 Vcc ACC GR TR GNO link 5 - 9 1

CE 0101_ 010i D101 A2 10 6 lc 0111 WE 674 LS138' DBIN

8 GND RS0 13 lozal10c

11W1 cMi2 - RS2 RD 11;+ INT 12a Nim 31 \_ 16 0108 I13a D7 D108 D 09 A2 20 14 1 IC 4 CC or interrupt line TMS9914A (see text) 4k7 2 11 Vcc CONT DC GND 10 SRO. sRa SRO. 3a I Ma= 11 DO ATN ATN ATN 5 E01 1C3 E01 EOI 74 LS 245 DAV DAV DAV N RFD NRFL NRED -D0 NDAC NDAC NDAC 0 9 07 GNO I FC I FC 1FC 17 RES REN REN REN Z80 bus/SC84 20 21 edge connector GND TE Vcc 22 12 Shield 13 14 ICA 75162 24 23c 3 Logic GND IC 7 O See text 18-23 7474 GND

16c RESELT.

remaining three. \5_3 being used to select Z80 to IEEE488 interfacing is simplified by and the data lines using the 75160. Input 1E. one of the eight output lines used to enable the 9914 dedicated controller. Apart from pin 1 of the both the buffers ttalk enable), the 9914. a little control -signal gating. the remaining determines the sense of the flow through the Which output line to use is chosen fairly i.cs simply buffer the various buses. buffers. A fuller implementation of the arbitrarily. Number 1is used here, so the IEEE488 standard would require a 75162 registers are mapped to ports 10-171h. By instead of the 75161 to allow an overall changing the order of the inputs to the the correct (active low) sense for the chip - interface controller to take precedence over LS138 to any eight unused consecutive enable input (pin 3) of the 9914, and this temporarily -assigned controllers, but there ports, the range is selectable. signal is also gated with the line from the arc relatively few applications where this is An often overlooked characteristic of the Z80 to give an active -high IMIN signal (pin 5 necessary. Z80 is that the line not only signifies an of the 9914) to indicate that the Z80 wants SOFTWARE input/output request, as its name implies. data from the chip. but also an interrupt acknowledgment. The active -high IMIN signal is also sent to Since the IEEE488 interface is so versatile, Wheni-04 is active (low), therefore, it does the 74LS245 data buffer to indicate that it and its applications so diverse. it is difficult not necessarily imply that i/o is taking place. should send data from the 9914 to the Z80. to give much indication of what software to Whether i/o or an interrupt acknowledge is Care must be taken not to allow data from a driveitentails. Consequently I have not required is determined by the state of su peripheral onto the data bus spuriously, as included examples. Reference to the Texas which, when active (low), indicates that the the consequences are generally more dis- Instruments data book on the 9914 is essen- c.p.u. is in the first machine cycle of an astrous (and less difficult to trace) than a tial. instruction (normally the op -code fetch spurious write to a peripheral. Under SciDOS and CP/M operating sys- period). Design of the data -bus buffer is simple. Its tems it is relatively easy to set up the bus for Input/output requests cannot occur dur- chip -enable input is held permanently active read/write transfers using the often other- ing Mi. so MI being active concurrently with (low) so the 9914 data inputs usually follow wise redundant PUN: and RDR: logical de- WW) indicates interrupt acknowledgement. those of the Z80. Data is ignored by the 9914 vices. Where these devices have been allo- while MI being inactive (high) designates an until imiN is high and a are low: the decoding cated, for RS232 input and output ports. i/o request. This is why mi is connected to the ensures that there are no spurious writes toaccessing the IEEE488 interface from sepa- active -high enable input of the 74LS138. Of the chip. When the 9914 address is selected rate programs is more tedious. It is usually course, itis not a problem for computers and the W) line from the Z80 is active (low).better to have one block of general-purpose which do not use interrupts. the direction of data transfer in the buffer iscode used in different ways than to rewrite Output of the 74LS138. indicating that reversed and output from the 9914 is con-source code for each application. the address bus holds an address in the range nected to the bus. Further complications arise when adv- of the 9914 registers and that mi is not Unused gates of the 74LS02 are tied to anced features such as service requests and active, is gated with by one gate of the +3V through a resistor. As mentioned ear-secondary addressing are used, but with 74LS02 quadruple two -input Nor package. lier the 75160 and 75161 buffer output of therelatively little effort the necessary informa- This is inverted by a subsequent gate to give 9914. with the control lines using the 75161.tion can be extracted from the Texas lnstru-

ELECTRONICS & WIRELESS WORLD 853 ments book. For operation of the interface from SC84, the STI data sheet will also be necessary to find out how to interrupt the main processor. Software sets the IEEE488 address bus by Conferences and writing to one of the registers in the 9914, which is why I have not included the cus- tomary dip switches. For our purpose this was more appropriate since the various exhibitions SC84s could have their software exchanged to change their functions. As the address was specified in software,it moved with the 5-9 September, oxford: Science 68. 150th annual 23-27 September, Brighton: International function of the computer, not with the meeting of the British Association for the Broadcasting Convention I IBC88). with 100 tech- hardware. Advancement of Science. Special events include nical papers covering d.b.s. and cable systems, exhibitions in the University and at Oxfordrecording. studio and o.b. equipment. measure- Polytechnic, concurrent conferences organized TESTING ment techniques and new services. and an exhibi- by other learned societies, a scientific film festival. tion supported by 200 companies from Britain and The easiest way to test the interface is to a day of debates on problems now confronting abroad. Details from IEE Conference Services on connect a printer with an IEEE488 interface science, a family science day - and a re-enactment 01-240 1871 ext.222. by BBC Television of the celebrated confrontation to it. Epson provides plug-in cards for some between Bishop Wilberforce and T.H. Huxley over 27-30 September, Birmingham NEC: Test + of its models, which allow the printer to evolution and the origin of Man. which took place Transducer '88 exhibition and conference. Elec- behave both as an addressed device (printing in Oxford at the BA meeting of 1860. Among the tronics in Engineering Design and Design En- only when told to listen by the controller) highlights of this year's conference are a day's gineering shows. Details from Trident Interna- and as a bus monitor. when it prints (in symposium on molecular electronics, a session on tional Exhibitions Ltd in Tavistock. 0822-614671. hexadecimal form) the contents of data lines educating the engineers of tomorrow, and a28 September, London: one -day conference. na)1_8 as each byte is transferred (slowing lecture by Dr David Jones ("Daedalus" of the New Liberalisation of European telecommunications - the bus down to do so). Each command sent Scientist), who promises to demonstrate to his preparing for 1992. IBC Technical Services. 01- is also printed in bold type, which is very audience some intriguing physical phenomena. A 236 4080. useful. programme is available from the BA in London. 01-734 6010 ext 381. 3-7 October, Cascais.Portugal: international Connecting other devices to the bus is conference on the theme New Directions for Unix. then quite straightforward, but some inter- 6-8 September, Wembley, London: Coil Windingwith tutorials and showcase. Organized by the faces do not seem to behave as expected, so it International exhibition and conference. DetailsEuropean UNIX systems User Group, telephone is as well to have tried your software with a from Bush Steadman and Partners. 0799-26699. ( Royston. Hertfordshire) 0763 73039. device that is known to work and is under- 6-11 September, New Delhi: Electronics India 5-11 October, Cologne: photokina - world's fair stood. 88. Details from the general manager. Trade Fairof imaging systems. KolnMesse. Messeplatz I. Authority of India. Pragati Maidan, New Delhi. Postfach 210760. D-5000 Kiln 21 (Deutz): telefax Further reading India: telex (India) 031-61022 COMX IN. (0221) 821 2574. Adams. 1.11.. SC84 Microcomputer. Electronics September and 9-11 September, Eastbourne: Tecdoc'88, tech- 4-6 October, San Diego. California: international October 1984. nical documentation and communication. orga display research conference, organized by IEEE TMS9914A General Purpose Interface Bus (GPIB) nized by the Society of Electronic and Radio Electron Devices Society and others. Details from Controller. Texas Instruments. Manton Lane, Technicians. One of this year's themes is translat- the Advisory Group on Electron Devices. 201 Bedford MK41 7PA. ing documents into other languages - 1992 is not Varick Street. suite 1140. New York. NY 10014. far off. Details from Consert, 57-61 Newington Causeway, London SEI 6BL, tel. 01-403 2351. 17-19 October, IEE. Savoy Place. London: fourth Timothy Vellacott is 23 and in the second international conference on satellite systems for 12-15 September, University of York: IERE con- mobile communications and navigation. Details year of a Doctor of Philosophy course in the ference on electromagnetic compatibilityfrom IEE Conference Services. 01-240 1871 ext. Department of Atmospheric, Oceanic and le.m.c.). The conference will be preceded by a 222. Planetary Physics at Oxford. He is involved tutorial day and accompanied by an exhibition. with building part of the PMIRR satellite Details from the conference secretariat on 01-240 18-20 October, Brighton: Southern Electronics instrument to be flown on NASA's Mars 1871. Show. Details from Trident International Exhibi- tions Ltd in Tavistock. 0822-614671. Observer mission in 1992. 13-15 September, Novotel. London W6: Power Timothy's 1EEE488 interface was de- UK 88 and Enclosures 88 (note change of dates). 24-28 October, Monte Carlo: international sym- signed in 1985 when he was a vacation Conference topics include battery technology.posium on automation, concentrating on cell student in the Department. The satellite r.f.i./e.m.i. shielding, smart power, connectioncontrol and quality management systems for the instrument mentioned in the articleis design for the enclosure industry. Contact: SCS manufacturing industries: accompanying trade !SAMS, a stratospheric and mesospheric Exhibitions Ltd at Portsmouth on 0705-665133. exhibition. Details from ISATA in Croydon. 01- 681 3069 or 01-686 1329. sounding pressure -modulator radiometer 13-16 September, Alexandra Palace. London: being built by Oxford. Rutherford Appleton EPoS/EFTPoS 88 - retail automation show and 26-27 October, Wembley Exhibition Hall. Lon- Laboratory and British Aerospace. and to be conference. including technical sessions. Details don: Instrumentation Wembley. Details from Tri- flown on the Upper Atmospheric Research from RMDP Ltd in Brighton. 0273-203581/3. dent International Exhibitions Ltd in Tavistock. 0822-614671. Satellite in the early 1990's. ISAMS will 14-17 September. Washington D.C.: National measure temperature and concentrations of Association of Broadcasters' Radio '88. Details 1-3 November, Barbican. London: ITEX - In- gases involved particularly in the chemistry from NAB at 1771 N Street. N.W.. Washington formation Technology Exchange. New event of ozone on a global scale. D.C. 20036. tel. (202) 429-5420. which will display the latest commercial applica- tions of i.t. research and development, linking 19 September, London: one -day conference on Alvey. Esprit and other research programmes. digital cordless telephones ICT-2. telepoints etc.). Supported by DTI. Cahners Exhibitions. 01-891 Fee: £245 +v.a.t. IBC Technical Services. 01-236 5051. 4080. 3-6 November, Los Angeles. The DTI is again 20-24 September, Besancon. France: interna- providing support for British companies wishing tional exhibition of microtechniques, Micronora to exhibit at AES: details from the Sound and Eurocard p.c.bs for this design are available 88, with the theme cad/cam stamping andCommunications Industries Federation in from Combe Martin Electronics. King machining. Details from French Trade Exhibi- Slough. tel. 06286-67633. Street. Combe Martin. North Devon for £9 tions. London. 01-225 5557. fully inclusive (UK or overseas). The boards 14-18 November, Paris: International Exhibition 21-25 September, Olympia. London: Personal for Electronic Equipment and Products, PRONIC. are single sided, silk screened and compati- Computer World Show. Details from Montbuild Details from French Trade Exhibitions, 01-225 ble with SC84.s Z80 backplane. Ltd. 01-486 1951. 5566.

854 ELECTRONICS & WIRELESS WORLD ELECTRONICA-MUNICH

`1° 8-12 NOVEMBER 1988 WIN A WEEKEND IN MUNICH Electronics & Wireless World in association with Electronics Weekly isoffering everybody who books one of the business trips listed below to Electronica, a chance towin a TRIP FOR TWO to MUNICH for the weekend following the show. The leading electronics newspaper and technical monthly, inassociaticn with Commercial Trade Travel, will fly your partner over on Friday morning viaGatwick, giving you a full weekend in Munich. We will then fly you and your partner home onSunday. The draw will take place on Friday the 21st October and the winnerannounced in the November issue of Electronics & Wireless World and the 26 OctoberElectronics Weekly. Good Luck The Hotels The Tours MUNICH SHERATON HOTEL FLIGHT DEPARTURES FROM FLIGHT DEPARTURES FROM This de -luxe hotel is situated in the fashionable Bogenhausen district of GATWICK HEATHROW Munich, close to the English Gardens and 10 minutes from the airport (Scheduled services of Air Europe) (scheduled services of Lufthansa) and downtown area All rooms have private bath/shower, WC, hair TOUR A -3 days (2 nights) TOUR D -3 days (2 nights) dryers, direct dial telephone. TV. radio and video service and =that Tuesday, 8 November Tuesday, 8 November The hotel has fashionable bars. restaurants. and night club as well as a depGatwick 07 15 depHeathrow 09 45 large swimming pool. sauna and fitness centre Opposite the hotel there arr Munich 10 00 an Munich 12 20 is a pedestrian shopping centre with several restaurants. bars and a Thursday. 10 November Thursday, 10 November 11 25 iepMunich 12 20 cinema Inthe Autumnof1988isproposedthatthe U-bahn depMunich (underground train) will be opened linking the hotel downtowr area an Gatwick 18 00 arr Heathrow 15 20 and exhibition grounds TOUR B -3 days (2 nights': TOUR E -3 days (2 nights) Thursday, 10 November Thursday, 10 November depHeathrow 09.45 REGENT HOTEL dep Gatwick 07 15 arr Munich 10 00 arr Munich 12.20 This brand new first class hotel is situated in the city centre, close to the Saturday. 12 November main railway station and exhibition grounds It is possible to walk to the Saturday. 12 November depMunich I I15 depMunich 12 20 fair grounds in 20 minutes or on the U-Bahn (underground train) it is lust arr Gatwick 12 00 arr Heathrow 15 20 2 stops The hotel has a fine reputation.all rooms have private bath -shower. WV, radio and TV. =mbar and direct dial telephone The TOUR C -3 days (4 nights) TOUR F -5 days (4 nights) hotel has a fashionable bar and elegant restaurant. It also has a sauna. Tuesday. 6 November Tuesday, 8 November 09.45 solarium, whirlpool andcoiffure. depGatwick 07.15 depHeathrow arr Munich 10 00 arr Munich 12 20 Saturday. 12 November Saturday. 12 November CONDOR HOTEL depMunich 11 15 depMunich 12 20 This 5 -star hotel is situated in the City Centre, close to the main railway arr Gatwick 12.00 art Heathrow 15.20 station and within15 minutes walk, or lust 2 stops on the U-Bahn (underground train) from the exhibition centre. All rooms have private The Costs bath/shower, WC, direct dial telephone. radio and minibar. The hotel INCLUSIVE PRICES PER PERSON has a breakfast room. bar and spacious lobby area. (TWE - sharing twin bedded room with facilities) (SWE- single room with facilities)

MODERN HOTEL HOTEL MODERN CONDOR REGENT SHERATON This 3 -star hotel is situated in the City Centre. close to the main railway station and within 15 minutes walk, or lust 2 stops on the U-Bahn Accommodaticn TWE SWE TWE SWE TWE SWE TWE SWE (underground train) from the exhibition centre. All rooms have private bath/shower. WC, radio and TV, minibar and direct dial telephore. The TOUR A and b 295 340 305 360 340 450 360 450 hotel has a breakfast room and bar TOUR C 575 450 385 490 450 650 475 650 TOUR D and E 420 470 455 495 470 575 485 565 TOUR F 490 575 499 599 575 750 599 750 INCLUDED IN THE ABOVE PRICE Scheduled flight services of either AIR EUROPE or LUFTHANSA, in flight catering as appropriate to the timeof day travelling. all airport taxes, accommodation on a bed and breakfast basis inclusive of service charge and taxes: private coach transfers airport tohotel and return, a cocktail party at the Exhibition Grounds, season ticket entrance to ELECTRONICA including catalogue :the entrance tothe Exhibition is £29 per person), assistance upon arrival and departure in Munich of a Commercial Trade Travel representative COMMERCIAL TRADE TRAVEL are the only company offering tours viaGATWICK To make your reservation please ring Ray Gardner on 01-491 1312 orfill in the coupon and send to: Ray Gardner, Commercial Trade Travel Ltd, Aspen House, 25 DoverStreet, London W1X 3PA.

Name Name Address Address

Tel. No: Tel. No: ENTER 60 ONREPLY CARD

ELECTRONICS & WIRELESS WORLD 855 INSIGHT EXTRA

PC BUS PERFORMANCE NUBUS VS MICRO CHANNEL

\ vo new computers have been TABLE 1. EXAMPLE COMPUTER SYSTEMS introduced recently which This analysis of two use entirely new bus struc- NuBus Micro Channel T Computer Apple IBM PS 2 tures for add -in cards. Apple new personal computer bus Macintosh II Model 80 Computer's Macintosh II uses a personal Microprocessor 68020 80386 Clock speed 16 MHz 16 MHz computer version of the NuBus. IBM's new structures includes Card slots 6 8 Personal System/2 family uses an improved Add -in card NB -DMA -8-G MC GPIB Operating syst Macintosh PC DOS personal computer bus called the Micro comparative measurements Wait state 100 ns 62.5 ns Channel Architecture. This article presents a comparison of the two buses and the two based on plug-in computers, and includes a technical ex- and a PS/2 Model 80. The Macintosh II is run amination of certain measured system char- GPIB boards. by a 16MHz 68020 microprocessor and the acteristics using GPIB/IEEE488 boards Model 80 by a 16MHz 80386. The d.m.a. which have been developed for both buses. controller in the PS/2 runs at 8MHz, while The Apple MacintoshII and the IBM the Mac is equipped with a National Instru- Personal System/2 computers are attracting Micro Channel is a general-purpose compu- ments NB -DMA -8-G board containing an a great deal of attention from add -in board ter bus which supports 8.16, or 32 bit 82380 d.m.a. controller running at 10MHz. manufacturers. The article covers some of microprocessors, peripherals, and memory. The Macintosh II has six card slots, one of the technical aspects of designing cards for PS/2 Models 50 and 60 are equipped with which is used by a display adapter and these machines. 16bit 80286s, and Models 70 & 80 use the another which is occupied by the NB -DMA - The Macintosh II is a 32 -bit 68020 -based 32bit 80386. Models 50 and 60 support the 8 -G card. The Model 80 has eight slots, with computer which uses a personal computer 16bit version of the MCA, and Models 70 & one taken up by a disc controller and a version of NuBus a general-purpose 32 -bit 80 support both 16 and 32 -bit add -in cards. second slot used by National Instrument's computer backplane bus conceived at MIT MC-GPIB card. and developed further by Texas Instruments. Performance examples The MacintoshIIruns the Macintosh At present, the IEEE P1196 committee is The performance specification listed in the operating system and the Model 80 runs PC formalizing the NuBus specification into a panel are all theoretical in nature. To deter- DOS3.3. Slave cards on the Macintosh II can form suitable for acceptance and publica- mine how each bus actually performs,I introduce wait states of 100ns each, and on tion. examined two add -in card examples and the Model 80 each wait state adds an addi- The IBM PS/2 family currently consists of discuss the measurements obtained. tional 62.5ns to the transfer. six computers, three of which use the new Table 1gives a comparison of the two The NB -DMA -8-G, in addition to its 82380 Micro Channel Architecture (MCA). The computers used: a Macintosh II computer d.m.a.c. and bus master circuitry, has an IEEE488 interface which responds as a NuBus slave. The measurements described RTSI BUS use the NB -DMA -8-G both as NuBus d.m.a. 1 master and slave. Trigger Bus MC-GPIB is an lEEE488 interface for the 1ma DRO S x Control Interface Micro Channel. It can respond as a bus slave a to and also contains arbitration circuitry to NMR V 4 clods allow it to be used in conjunction with the Pnsocale,

Master DMAC d.m.a. controller on the mother board. Interlace Counter/Timer System GPM DMA Requota Slave performance LL In this example, I treat the NB -DMA -8-G and DATA BUS M the MC-GPIB cards as bus slaves and mea- o ADDRESS BUS co sure some of the timing parameters which z are of interest and which affect i/o perform- GPIB ance. a. Slave GPIB Direct Access Port Trans Interface Turbo488 cewers A block diagram of the NB -DMA -8-C is shown alongside. For performance testing, I NMR had the Macintosh II's 68020 execute a simple i/o write test. The test programs, shown on this page, transfer data to and GPIB GPIB from the 16x 16 bit, fifo memory in the Interlace Trans Controller ceivers Turbo 488 integrated circuit on the card. The same test was performed on the PS/2 V Model 80 using the code shown. A block

ELECTRONICS & WIRELESS WORLD INSIGHT EXTRA diagram of the MC-GPIB card, right, identi- fies the Turbo 488 and circuitry that perform slave functions which are quite similar to those on the NB -DMA -8-G. Table 2 gives a summary of the perform -

TABLE 2. SLAVE TIMING PERFORMANCE

Macintosh II PS/2 Model 80 and NB -DMA -8-G and MCGPIB Type 16 bit i o 16 -bit i o Read cycle (min) 403 ns 375 ns Write cycle (min) 403 ns 375 ns (byte s) Measured' o read 703K 533K The two boards and computers compared in these tests are National Instrument's MC-GPIB rate (byte's) Measured r'o write 703K 533K interface for the IBM PS/2 (above and below), and the NB -DMA -8G combined d.m.a. rate bytc /s) controller and 488 interface (page 856). Measured interrupt 35 ps 7.3 !, s latency ance obtained using the test programs and the two different systems. The fifo read and write cycle times are theoretical best -case values. Note that the NB -DMA -8-G adds 200ns to the fastest possible transfer cycle on Address the NuBus. This extra delay is due to fifo U) Latches synchronization arbitration and access time. CO Similarly, the MC-CPIB adds approximately Data CPS GPI8 Transcervers Turbo4t8 .nterface "franscervers-- 125ns to the minimum Micro Channel cycle. -J -0 Controller These delays establish maximum theoretical w transfer rates of 2.5 x 10616 -bit transfers per Bus Interlace second (5Mbyte/s) for the NB -DMA -8-G and Logic 2.67 x 106 16 -bit transfers per second DMA and (5.3Mbyte/s) for the MC-GPIB. POS Interrupt The actual programmed i/o rates obtained O Log c using the i/o read and write test programs CC Address are 0.7Mbyte/s for the NB -DMA -8-G and Decode 0.533Mbyte/s for the MC-GPIB. As you can see, bus speed is of less importance in this example than microprocessor performance (execution time, program memory speed, on -chip cache, instruction set, etc). One final slave timing characteristic was measured for both systems: interrupt re- sponse time. For this test, the time between when the card generated the interrupt re- quest on the bus to when the interrupt service routine was entered when measured. The 35µs interrupt latency for the Macin- tosh II is indicative of the interrupt service queue used by the Macintosh Operating System rather than hardware performance features of the 68020. The 7µs interrupt latency for the PS/2 Model 80 is a close indicator of actual hardware performance, since no intervening interrupt service soft- ware overhead is incurred in PC DOS.

Bus master performance To measure bus master performance and, in particular, d.m.a. performance, we use the 82380 d.m.a.c. on the NB -DMA -8-C to trans- fer data to and from the MacintoshII motherboard and the fifo on the card. For the Micro Channel, we use the arbitration circuitry on the MC-CPIB in conjunction with the PS/2 Model 80 d.m.a.c. to transfer data to and from the motherboard memory and the fifo on the card. The results of the test are shown in Table 3. Burst mode fetch and deposit d.m.a. transfers were used on both machines. Transfers on the NuBus were 16 bits wide for i/o accesses (fifo reads and writes) and 32 bits wide for memory. (The 82380 automatically

ELECTRONICS & WIRELESS WORLD 857 INSIGHT EXTRA

TABLE 3. BUS MASTER PERFORMANCE For example, if you were developing a high Macintosh II PS.2 Model 80 performance. intelligent peripheral proces- and NB.DMA-8-G DMA transfer and MC-GPIB sor card for the Micro Channel, you may be Comparative type burst dual burst dual forced into developing two versions: one Data width 16/32 16i16 with a 16 -bit interface and one with 32 -bit Master latency 300ns 500ns overview I/O read 500 ns 750ns interface. I/0 write 500 ns 750 ns The small board area available on Micro The table lists some of the primary features Memory read 1.1 p s 375 ns Channel cards makes development more of the PC -style NuBus and the Micro Chan- Memory write Ups 375 ns nel bus. The NuBus is considered a synchro- Transfer rate 1.9M 1.8M difficult. In many cases. the developer will be (byte, s) nous bus. All bus transactions are referenced forced into designs which require gate arrays to a single. 10MHz clock signal. Transac- or other asics and/or surface -mounted com- tions on the Micro Channel bus are asyn- performs source and destination hit width ponents. Both of these solutions lengthen chronous and are not referenced to a specific adjustments. The master latency times show clock signal. development time and, except in very high The 10MHz + 0.01% clock on the NuBus how long it took from the time the card volume cases, increase manufacturing costs. has an unequal duty cycle of 25:75. The requested use of the bus until the time it At National Instruments, itis easier to Micro Channel bus provides a 14.31818MHz received bus control. design for the NuBus because of its synchro- + 0.01% clock signal but does not use it for The i/o read and write times indicate the bus timing. nous nature. The separate address and data Micro Channel Architecture provides for time taken to access the fifo by the d.m.a. lines on the Micro Channel do not turn out separate memory and i/o address spaces controller. The memory read and write to be of advantage because timing require- while NuBus provides for a single address times show how long it took for the d.m.a. ments force addresses to be latched much in space. I/O addresses on the Micro Channel controller to access system motherboard are 16bits wide. providing 64K bytes of i/o the same way that they are latched on NuBus address space. ram. Note thatit should he possible to implementations. Memory addresses on the NuBus are substantially increase the performance of Although I don't have quantitative, mea- 32 -bits wide and allow up to 4Gbytes of ram the Macintosh II in this example by using a sured data to support this next conclusion, it or rom to be individually addressed. The high-speed ram. PC -style NuBus add -in 16 -bit version of the Micro Channel uses a isobvious that a portion of the Micro 24 -bit memory address, which translates to card. Channe! bus bandwidth is utilized by the 16Mbytes: the 32 -bit version provides a full The data transfer rates are given last. The arbitration process, and that the percentage 32 -bit. 4Gbyte memory address space. Macintosh II is able to overcome its relative- used increases as more devices contend for Data can be transferred on the NuBus as ly slow memory access time by transferring bytes. 16 -bit halfwords, or 32 -bit words. The the bus. Unlike the Micro Channel. NuBus 16 -bit version of the Micro Channel can 32 bits as opposed to 16 bits on PS/2. arbitration occurs in parallel with normal transfer 8 or 16 -bit data. while the 32 -bit hus traffic. version can handle 8, 16. 24 and 32 -bit data. Results For i/o intensive applications involving Bit, byte. halfword, and word significance is Both machines provide powerful platforms the same on both the NuBus and the Micro large blocks of data, I feel that it is essential Channel. for add -in i/o cards, and both have distinct for the computer system to provide d.m.a. On the NuBus, cards are given 1/16th of advantages and disadvantages, as well as transfer capability. The MacintoshIIre- the total 4Gbyte address space 1256Mbyte). unique characteristics. Some of the features quires that this capability be provided by the NuBus allows up to 16 cards in a system and that are common to the Macintosh II and the each card is given I/16th of the total 256M add -in cards, themselves. The PS/2 uses a card address space (16Mbyte per card). The PS/2 Model 80 are high speed. 32 -bit microp- clever scheme which allows cards to use a card automatically assumes itsproper rocessor. memory, and bus: automatic card d.m.a.c. on the motherboard. Unfortunate- address by sampling four signals on the configuration at power on (no jumpers): ly, the one on the PS/2 Model 80 is limited to NuBus connector whici, provide a card powerful interrupt mechanism: and support identification code. 16 -bit transfers. Perhaps future members of Micro Channel cards use the Programm- for multiple add -in cards. Some of the the PS/2 family will offer full 32 -bit support. able Option Select IPOS) feature to deter- dissimilar features are listed in Table 4. The Micro Channel provides refresh sup- mine i/o addresses. Add -in card address information is stored in a non-volatile r.a.m. TABLE 4. MACINTOSH II AND PS/2 MODEL 80 port for dynamic ram. add -in cards. This available to the microprocessor. At power - FEATURE COMPARISON eliminates the expense of refresh circuitry on -time, the microprocessor reads the on each ram card. It does, however, utilize address informationi from the n.v. r.a.m. Macintosh II PS 2 Model 80 bus bandwidth (less than 5% on the PS/2 and configures each card in the system. NuBus Micro Channel Model 80). This characteristic is probably Using the POS mechanism, add -in cards may industry standard custom edge connector occupy any free portion of the available connectors multiple versions of bus paralleled on the NuBus, however. by in- memory or i/o address space. 'one standard bus small board area creased access times during memory refresh medium board area asynchronous bus synchronous bus serial bus arbitration and bus access collisions. Data transfers. A minimum single data parallel bus arbitration integral d.m.a. Accessing the Macintosh ll motherboard transfer on the NuBus consists of two clock no integral d.m.a. refresh circuitry on ram from an add -in master NuBus card is cycles (a start cycle and an acknowledge refresh circuitry on cards cycle,of 200ns, which translates to a slow memory access fast memory access agonizingly slow by today's standards. The 20Mbyte/s transfer rate see Tables. The PS/2 family offers acceptable access to its Micro Channel minimum cycle is 200ns. motherboard memory. Perhaps future ver- which, for 32 -bit data transfers, translates to I feel that the 96 -pin DIN connector used 20Mbyte/s. The 10MHz 80286 microp- by the PC -style NuBus cards offers advan-sions of the Macintosh ll will correct this rocessors used in the PS/2 Models 50 and 60 tages over the edge fingers defined by the deficiency. support a minimum cycle of 300ns. which translates to 6.7Mbyte/s. The 16MHz 80386 Micro Channel Architecture. primarily in Models 70 & 80 have a minimum cycle of terms of mechanical real iabi I i ty. 250ns, or 16Mbyte/s. The higher - The multiple versions of the Micro Chan- performance 20MHz 80386 version will be nel make it more difficult to develop add -in able to support the full 20Mbyte/s transfer Nowlin is engineering vice-president with rate of the Micro Channel. cards that can be used on all machines and at National Instruments Corporation. Austin. Texas. the same time offer maximum performance. represented in the UK hy Amplicon Electronics.

858 ELECTRONICS & WIRELESS WORLD INSIGHT EXTRA

Interrupts. The PC -style Nubus provides an Bus masters. NuBus arbitration priority is CARD SLOT ID fixed and depends on the card slot ID. with interrupt request signal for slave cards called 9 t0 11 12 13 slot number 15 having the highest priority. non -master requests. or NMRQ. As im-

Figure 1 shows the relationship of the plemented on the Macintosh II, each card NuBus slot IDs for the Macintosh II. generates a separate interrupt request signal The Micro Channel defines 18 levels of to the 68020 microprocessor on the mother- fixed priority, see Table. The arbitration level board. Each slot's interrupt has a prog- used by an add -in card is normally controlled DISK rammable priority. Interrupts on the Macin- by a Programmable Option Select register CARD SLOTS DRIVES on the card which allows a limited form of tosh II are level sensitive as opposed to edge programmable priority. sensitive. MAIN LOGIC BOARD The Micro Channel implements a share- ID -c able. level -sensitive, multiple -line interrupt mechanism. A total of 11 shareable interrupt DMA transfers. The Micro Channel compu- lines are available on the bus. Priorities are ters are equipped with an eight -channel 16 -bit transfer counter, providing the ability shown in the Table. d.m.a. controller. Add -in cards can use the to transfer 64K 16 -bit words (128K bytes) or d.m.a. controller to perform data transfers 64K bytes with a single d.m.a. operation. using the standard Micro Channel bus arbitration mechanism. The d.m.a. control- ler on PS/2 Models 50 and 60 runs with a 10MHz clock. and the 16MHz Model 60 d.m.a.c. runs at 8MHz. The Macintosh II does not provide a d.m.a. controller on the backplane. For d.m.a. comparison, we used the NB -DMA -8-G card, MAIN FEATURES OF NUBUS AND MICRO CHANNEL Fig.2. This provides the Macintosh II with a general-purpose d.m.a. controller for the MicroChannel interrupt priorities PC -style NuBus in addition to a 488 bus NuBus Micro interface. It uses an Intel 82380 controller Channel NMI Parity. watchdog tinter. running at 10MHz. Type synchronousasynchronous Arbitration time-out An analysis of the d.m.a. capabilities of the Frequency Channel check IRQ 0 Timer Macintosh II equipped with an NB -DMA -8-G I 0 address width 16 bit Memory address 32 bit 24:32 bit IRQ 1 Keyboard card as compared to a 16MHz IBM PS/2 width IRQ 2 Cascade interrupt control - Model 80 with built-in d.m.a. controller is Data width 8/16/32 bit 24/32 bit IRQ 8 Real time clock shown in the Table. The analysis is theoretic- Card addressing Geographic POS IRQ 9 Redirect cascade al and assumes best -case conditions. slot IRQ 10 Reserved Each configuration can support eight Data address linesMultiplexed Separate IRQ 11 Reserved Multimaster yes yes IRQ 12 Mouse independent channels. The 82380 on the Bus parity Optional no IRQ 13 Math coprocessor exception NB -DMA -8-G can perform 8. 16, or 32 -bit Number of cards 16 8 IRQ 14 Fixed disc data transfers: the PS/2 Model 80 can per- IRQ 15 Reserved form 8 or 16 -bit transfers. The Model 80 RQ 3 Serial alternate d.m.a.c. transfers data using a fetch and Theoretical maximum bus transfer RQ 4 Serial primary deposit technique. called flow -through or rates RQ 5 Reserved dual -addressing. The 82380 normally uses RC 6 Diskette Single cycle 20Mbyte/s 20Mbyte/s RC 7 Parallel port the same fetch and deposit method, but can Block 37.6Mbyte/s - RQ 8-15 are cascaded through IRQ 2 also support single address or flyby d.m.a. Block size 16 (64byte) - transfers. For this theoretical analysis,I assumed that the data transfers can be performed in Bus masters the minimum time possible: for both Micro Number (max.) 16 16 Mechanical comparison Arbitration Parallel Serial Channel and NuBus. Micro Channel Burst capabilities allow the d.m.a.c. to Priority Fixed Programmable NuBus Fairness Yes Programmable keep the bus as long as necessary. Assuming Bond area 52 in' 35 in that no higher -priority master is using the MicroChannel arbitration priority Nurnber of i.cs 74 50 NuBus, we can determine the maximum (i 0.7 in2,i.c.) 0.8 in Arb level Assignment Intncard spacing 1 in transfer rate obtainable using burst mode. Component height0.55 in 0 6 in For the NB -DMA -8-G, this time is 600ns per Connectors 96 pin DIN Card edge 32 -bit fetch and deposit cycle 16.67Mbyte/s) -2 (highest) Memory refresh -1 n.m.i. and 400ns per 32 -bit flyby cycle (10Mbyte/s). 0.7 d.m.a. On the PS/2 Model 80, the memory 8-E Reserved refresh arbitration level will override any F System microprocessor burst transfer in progress. Since a memory Bus connectors and signals refresh takes place an average of once every Theoretical maximum d.m.a. transfer NtiBus Micro Channel 15.8µs,this will limit the number of 16 -bit rates (byte/s) 1616 VE3232 MMS fetch and deposit transfers that can be 16MHz Macintosh II PS/2 performed during a burst to 25. Using this Total active pins 96 112 132 174 182 with NBDMA8GModel 80 fact. the maximum burst data transfer rate Digital bus signals 51 76 76 107 107 that can be achieved is 3.1Mbyte/s. Number of :Flannels 8 8 8 Total power 23 12 12 18 18 The 82380 d.m.a.c. on the NB -DMA -8-C is DMA transfer type dual single dual 5V 11 7 7 10 10 equipped with a 24 -hit transfer counter. Cycle steal transfer 12V 2 3 3 6 6 5.0M 6.7M 2.0M itto transfer a maximum of rate 12V 2 2 2 2 2 allowing Burst mode transfer 0 16Mbyte/s with one d.m.a. transfer opera- 52V 8 0 0 0 rate 6.7M 10M 3.1M G-ound 22 17 22 26 28 tion. Maximum transfer Other and 0 7 22 23 29 The custom d.m.a.c. on the PS/2 Model size 16MB 16MB 128KB rrserved 80. and on Models 50 and 60, contains a

ELECTRONICS & WIRELESS WORLD s19 FEEDBACK

started their own companies. am wholeheartedly in favour of'golden -eared' fraternity. and Better, nicer Thank you for expressing his basic premise. that engineer-provided a ready market for the these very necessary sentiments. ing progress must be founded on publishers of the magazines connector Clyn S. Craig. objective and reproduciblewhich catered for this area of The review of 'Electronics and Microdyne c.c.. measurements, and on specificpublic disquiet. technical goals. Opinions. While I arrived on the transis- computer acronyms' byPhil Edenvale. Brown IEIVW July) mentions Transvaal, however august their author.tor audio amplifier design scene that BNC (asin connector) South Vrica. cannot be anything other than arather too late to fall into the stands for Bayonet Nut Cou- possible corroboration that thepitfall of class -B crossover distor- pling. technical targets sought by thetion and I was aware enough to engineers are correct, or an in- A more interesting version is F.m. offer designs which were not given by Chet Heyberger and dication that the desired speci-slew -rate limited. I am sure there broadcasting fication is, in some way. less thanare other things which I did not Marshall E. Pryor in 'The XYZs of adequate. do as well asIshould. simply using a Scope' (Tektronix. Regarding the comment in Radio However, thefactthatthe because I do not know sufficient- Beaverton. 1981) in which BNC Broadcast in your July issue - 'subjective sound' pundits ever lyfully the performance stan- means "Bayonet Neill- "listeners have failed to respond got their foot in the door of thedards I should seek to meet, or Concelman": named forPaul to the 'listen on f.m. exhorta- standards laboratory in the firstthe tests which I need to apply. to Neill. who developed the N series tion' "- the basic reasons for this place is the engineers' own fault,disclose the faults which a care- connector at Bell Labs, and Carl are the design of domestic re- in that when transistor ampli-ful listener with good program- Concelman, who developed the C ceivers (the proposed BBC re- fiers were first introduced, as anme material and ideal listening series connector. ceiver mentioned in the June 'improvement' on the existingconditions might perceive. Roy Fursey. issue would be a giant leap for- valve -operated designs. they suf- Taking one specific point aris- Netherburv. ward) and the programmes that fered from large amounts of re-ing from Mr Self's article. I think Dorset. are available on f.m. sidual crossover distortion - lesshe. like the audio engineering The BBC must take the blame I am afraid I must take issue with than 0.1%. perhaps, at full out-worldingeneral, places too the statement that BNC stands for the latter, with their policy ofput power, hut several percent at frequency -hopping. Imagine much reliance on steady-state for Bayonet Nut Coupling (book normal listening levels. The en- how long we would have been tests. such as his low signal -level reviews. &Wit' July 1988). It is gineers. and the manufacturers't.h.d. measurements on different stuck with 405 -linetelevision in fact short for Bayonet Navy sales blurbs. said they were ex-types of capacitors. which appear had the same policy been applied Connector, being a development cellent.hut the man inthe there. You switch on BBC( on to have convinced him that there of the "N" or Navy type coaxial street, and his wife, thought theyare no effective performance dif- 625 at 5p.m. on Saturday and the connector. SMA. SMB and SMC were nasty to listen to. as indeed announcer says 'BBC] program- ferences between different capa- are variants of the Sub Miniature they were. mes continue on 405 only: on citor types. This may. indeed. he connector. All this information We, as engineers, havingperfectly true under steady-state can he found in Hewlett Pack- 625 we have the third in the tardily admitted our error in this series "Spanish for the Hard of conditions. ard's professionalr.f.testgear matter, then went on to stabilize Hearing". It is my opinion that the pur- catalogue - which contains a Reinforcing the 'listen on our amplifier designs, which hadsuit of steady-state linearity has great deal more very useful in- a.m.' attitude is the fact that, massive amounts of negativenow been carried to such lengths formation (and doesn't cost feedbck to improve the steady- after twenty years, the BBC's that the hulk of the residual c£24!). state linearity, with dominant most popular channel has no differences between specified Andrew Emmerson. lag compensation, usually across f.m. service except in the London electrical performance and appa- Northampton. the second gain stage within the area and the Radio Times lists rent sound quality lie in the - overall feedback loop, because programmes as on a.m. normally inadequately specified this particular technique led to What was surprising from the - behaviour of the audio system the hest high frequency t.h.d. School leavers survey mentioned was that 40% under discontinuous or tran- figure. This led, in turn, to aud- do listen to f.m. at some time, sient signals, which make up Mr Linsley -Hood's letter in your ibly objectionable slew -rate despite all the efforts to discour- such a large proportion of music April issue touched a responsive limiting effects, the existence of age them from so doing. or speech. Itis in this respect chord. which was again overlooked in S.J. Hampton. that many components. particu- In the early 'eighties I was the specification, but made the Shoreham -by -Sea. larly capacitors. exhibit a range employed by a major South Afri- amplifier sound poor, especially West Sussex. of known and measurable de- can recruitment company, in- at higher output levels. fects. volved in placing technicians and Once again, the man in the With regard to the transient engineers. Pseudo audio street noted that there were dif-performance of audio equipment During this time we saw a ferences in sound quality be-in general. it is certainly possible number of young persons who Iread with interest Mr Self's tween similarly specifiedde-to distinguish between systems were both "inspired and inquisi- article (July) on the contempor- signs. and that what we said washaving adequately low steady- tive". but lacked paper qualifica- ary attitude to audio engineering superb might not provide thestate waveform distortion, but tions. Even in this country of and its products. and I am grate- sound quality he expected. This,with large differences in their (electronics) opportunity. they fulthat EMI' has provided a and a few dozen other similarresponse to step changes or had difficulty finding positions forum in which this matter can oversights gave the potentialother waveform discontinuities. commensurate with their abili- he debated. buyer of audio equipment the However, since these differ- ties. Since Mr Self invites com- incentive to seek opinions basedences in transient response are In the end most of them opted ments. I would like to offer a few on listening trials, conducted byseldom measured and the per- for the only other option. and thoughts on this topic. Firstly. I respected figures among theformance. in this respect. is sel-

860 ELECTRONICS & WIRELESS WORLD FEEDBACK

dom defined. it is possible that indirected at the converted. Itis ducts (Letters. July.HiFi News)? I. for one, believe the follow- the eyes of thelay user thesafe to assume that, had he offer- Could it be that, bearing in mind ing (amongst other things - the differing units will appear to beed it to the editorial office of anythe questionable expertise of list is purely representative, but identically specified, which leadsof the well-known hi-fi comics, itthose to whom their product is one could go on and on): toa consequent. but dis-would have met with the enthu- entrusted. they regard a "good" (i) any subjective audible dif- appointed. expectation of iden-siasm accorded to a dead rodent. review just as damaging as a ference between, say. amplifiers. tical sound quality. I cannot but agree with every"bad" one? Looking at a couple which can be shown to exist by I would point, in this context.word, and I say this with feeling, recently, a very expensive ampli- means of astatistically well - to the substantial improvementshaving contributed regularly to fier was measured as having an controlled double-blind trial. which have been made in soundthe emerging hi-fimagazine overload of 23dB on a CD input of can be explained in terms of quality during the developmentworld in the distant past. review- 100mV sensitivity. Another, in measurement and current scien- of both cassette recorders anding as well. But what l find muchwhich a CD player measured tific knowledge: compact disc players, as betweenmore disturbingisthe steadypoorly. yet sounded the "best". In (ii) it is possible to make one's early and later designs of theerosion of ethical standardsboth cases, the reviewers had own perfectly competent if mod- same systems, of which much ofwhich the review "industry" (Isome degree of engineering estly powered amplifier, whose the improved performance is due use the word advisedly): the de- qualification - yet not one word performance need not sensibly to to significant improvements interioration of technical compe- of explanation. These two exam- be improved any further. for less the accuracy of reproduction oftence and what appears to beples are far from isolated. Read- than .150: transient -type signals rathercovert corruption as well. Strong ers of this magazine will need no (iii) loudspeaker cables have a than to any lessening of harmo- stuff.' Yes,itis - but there isexplanation from me, as to the small resistance, even smaller nic distortion. more than enough evidence of itsabsolute failure in this instance reactance, and that is the end of Overall. I simply do not believe truth. to justify public trust. it - discussions of skin -depth, or that we yet know enough about On the question of standards, Like Doug Self,Ifear this worse. transmission lines. are the importance. in audio terms. for a start: amongst those re- nonsense is going to be with us a ludicrous at audio frequencies: of some of the electrical short-viewers who actively lobby while yet. Experienced engineers ( iv)differences between comings of components, or ofmanufacturers and importwill run a mile, rather than take electro-mechanical transducers. the waveform distortions arising agents for work, very few haveon a review commission these and recording techniques (mic- in the signal chain due to compo- any academic qualifications ordays. This is not to say its end rophone placement etc.) far out- nent imperfections or injudi- training whatsoever: Iusuallycould not be hastened. Reputable weigh anything else in subjective cious circuit design - which lead refer to them as the "ex -shopmanufacturers could go public terms. to effects which can be both assistant" brigade. From them.and disown all reviews. until the All this seems really very ob- demonstrated and measured -we cannot really expect anything magazine business puts its house vious, and yet such is the current for us, as engineers, to be able to other than their own concept ofin order. Those reviewers who do seizure of the high ground by the say that there will be no audiblewhat is acceptable. Sadly, thatstill enjoy some respect and are subjective extremists. that I. an difference between componenttiny minority who do have anclinging to the wreckage - amateur at that. feel obliged to 'A'.having one set of knownengineering background have mere handful, sad to say - should state it. Can I put in a plea for defects, and component 'B' now been fully corrupted by what cease their ambivalence. Aban- people to stand up and say so if which has another. different, set. I referto as the "Emperor'sdon all that euphemistic custard they honestly can't tell the differ- or between systems of which clothes" syndrome. They either poured over a dubious product: ence between amplifier A or B. only some of the performancejoin the Subjectivist chorus - or emulate the little girl in the fairy and not be intimidated into characteristics are identical. lose work. Simple as that. It isn't tale and cry "But thisis rub- thinking that they have got cloth This is not intended as a justi- helped,either, by universitybish!". I'd like to think it was ears. rather than golden ones. ficationfor high -tensile -steel academics who lend a gloss ofpossible, but you know they have Let us have the courage to shout control knobs or mains wiringrespectability by contributinga living to earn. Meanwhile.I "The kingisn't wearing any made from single crystal copper. largely unreadable treatises fromshall go on doing my best at the clothes!". but as a plea that we should try to their ivory towers. university where I teach and nip John Howarth, assess the significance of the We must remember, and this this rubbish in the bud as soon as Hull, electrical phenomena we domust not be interpreted as a I see it. Humberside. know about, and can measure.justificationforallthis non- Reg Williamson, before either saying that defectssense. that hi-fiis now about Kidsgrove. It was with some interest and due to this cause don't exist or consumer durables. like washingStaffordshire. relief thatIread the article by that the effects that they do powder. Change the perfume and D.R.G.Self. As a professional en- introduce must be inaudible - inthis is the New. Improved Hi-Fi Three cheers for Doug Self and gineer with an interest in high - view of the fact that most avail- Amplifier: and a sycophantic re-his spirited attack on the lunatic quality sound reproduction, I able programme materialis view press obligingly dances tofringe of thehi-fifraternity. have always thought of subjectiv- already degraded. the industry's tune. More power to his elbow. ism as withlittletechnical J.L.Linsley Hood. Ethics? Who pays for those I would like him to know that foundation and even less com- West Monkton, trips to shows abroad? Not the there are plenty of us out here mon sense. Somerset. magazine, that's for sure. Whywho are strictly amateurs so far Iwould not, however, have are some advertisements refused as audio engineering and hi-fi been moved to put pen to paper Could it be that my stiff neck is by at least one well-known maga- are concerned, but who are were it not for an article pub- due to the vigorous nodding ofzine. with no explanation given? nonetheless enthusiasts and who lished in the June 1988 edition of my head whilst reading DougWhy does at least one of our have some sort of rigorous scien- Hi-FiAnswers.The item entitled Self's article? Alas. I fear that inleading high -quality audiotific training, who finditim- 'Free of charge' in my view trans- your august journal, his wellmanufacturers, Quad. openly possible to swallow some of the cends by orders of magnitude reasoned arguments are largelydiscourage reviews of their pro- nonsense currently propounded. any other writings on subjective

ELECTRONICS & WIRELESS WORLD 861 rFtEDBACK

audio.Initthe author (Mrseveral events and seminars for a loss to understand his difficul- system. The symmetry of the J.Hughes) puts forward thecompanies in the Yorkshire and ty. The constant is usually writ- force law demands that, if charge theories of a Mr P.Belt claimingHumberside area. We also take ten as 1/flare and has the value isto be given an electrical that the sound of your hi-fiis partinevents which bring 9x 10" Nm2/C2 where F isin dimension, then not one but two affected by such perverse thingstogether other members from newtons. (41 and q., in coulombs equal dimensioned constants as the number of CDs on yourEurope. At present I am prepar- and r in metres. This number is must be introduced, one associ- shelf, your wristwatch and evening a programme which will easy to remember and is wrong ated with each charge in the whether your sofa has three or(hopefully) demonstrate the by about 0.1%. equation, i.e. that Coulomb's law four legs. etc. changes in electronic technology In my experience, eft occurs by must be written Much more worrying is thefrom the turn of the centuryitself far more frequently than theory that all unused mainsthrough to the present day. The 1/47reft: hence I would not like to F = qi q2 powered appliances in the home concept is to illustrate, by meansbe writing 1/4irke whenever I r2 7Tc k must be "neutralised" by short-of a series of circuit diagrams. meant the constant represented ing the live and neutral pins ofnot only how the technology has by eft if I were constrained to be where an/k is equal to 1/4 -n -e0. If the mains plug with a piece ofchanged but how the "technolo- using standard notation. If Mr the consequences of this split are wire and crocodile clips.gical information" has changed. Boag wants another symbol as systematically followed through, Although the author does statei.e. the way the presentation ofstandard, I suggest he advocates and the fact that some over- that appliances must be unplug-circuit diagrams as well as thesomething looking vaguely like familiar equations were original- ged, the implications for safety ininformation content therein haseft_ as is the case with Planck's ly derived in the Absolute Elec- the home are clearly worrying ifchanged. The period 1908 toconstants h and h = h/2. trostatic System and contain readers believe the rest of the 1988 in 10 year segments has suppressed dimensional factors article. After telephoning thebeen chosen to illustrate this Finally. the equation is not forgotten, it can be shown editorial department ofHi-Fitheme. that E and D have the same F= 1 '1012 dimensions, and that at any Answers to check if the article I am therefore requesting any . was genuine (which it was) I haveof your readers who has, or can flare r2 point in a vacuum both take the written to both the magazine andget. access to circuit diagrams same value. expresses a relationship between The usual introductions of SI the publishing company to com- from these years if they would be pure numbers. A mathematician If. as Mr Belt claims, all so kind as to send me a copy. lam units fail to take account of these would not accept, for example, suppressed dimensional factors. items in the listening room thatsure the engineers working foran answer F = 10 newtons - he carry a static/electromagneticthe larger corporations would he and introduce some legerdemain would insist that the force is F into the handling of Gauss's charge should be neutralized,willing to dig amongst their arc-newtons, the distance apart is r perhaps the listener should re-hive materialto find a good theorem. errors which lead to a metres. etc., ensuring the quan- number of unexpected dimen- tire to another part of the houseexample of their past work. tities are pure numbers and giv- whenever the hi -ti is operating,These diagrams need not be sional distinctions. Thus E and D ing the answer F = 10. Givenare assigned different dimen- as he/she could be carrying aoverly complex, indeed simplic- this,I do not understand what large static charge and is de- ity is probably a more effective sions. and take different values at Mr Boag is trying to do at the end the same point in free space. This finitely a source of electro-way of getting our message of his letter by dividing the mag- magnetic interference! across. result, which physicists of the nitudes of a charge by a coulomb, generation of Jeans and Edding- In conclusion. subjectivism in Any contributions to this of a distance by a metre, and so the area of hi-fi has now movedprogramme would be gratefully ton would for good physical on.I suggest he consults the reasons have rejected out of way beyond the realm of goodaccepted and of course yourmaths department of his uni- sense and one wonders where itname and company would be hand, leads to the mystic notion versity for help. of the 'impedance of free space'. can possibly go from here. acknowledged in the final pre- Peter F. Vaughan. S.J. Shorey, sentation. The logical structure of the SI Coutant Electronics Ltd. electrical units is sound enough. Dartford. Thanking you in anticipation. Ilfracombe. Bill Herdman. and their utilityfor practical Kent. Devon. Dean Clough. purposesis unquestionable. Halifax HX3 5AX However the expedients adopted West Yorkshire in deriving them created a single Diagrams, T R Boag's vision in the July'Coulomb Constant' suffering letters of a madman wandering from incurable schizophrenia, please about at a Royal Society Soiree. which imposes a heavy burden Wagner, and introducing himself to all on anyone trying to understand I am writing on behalf of the and sundry as 'the Coulomb Con- rather than merely to use elec- Calderdale Business and Innova- Debussy and stant'.isperhaps even more tromagnetism. Nevertheless I tion Centre (CBIC) with a special appropriate than he realises. In believe that this burden can he request to your readers. electro- the original absolute version of relieved by changes falling well CBIC is a member of a Euro- magnetism the electrostatic units there is no short of complete destruction of pean network of centres set up to dimensional constantinthe the SI Valhalla for practical units. help small companies inall Ihave read the letter by T.R.Coulomb equation. since the aspects of their business develop- Boag in the July issue of EWW.equation itself defines the unit of C.F. Coleman. ment. In particular we deliber-concerning the constant lc in Felectrical charge in terms ofGrove. ately encourage such companies = k,.q (tar. the expression link-purely mechanical quantities. Oxfordshire. to use modern technology to ing the magnitudes of the force F Instead there is a purely numer- their advantage. As part of our between charges q1 and q2 sepa- ical factor, which is specified in work we are planning to stage rated by a distance r. and I am atdefining aparticular absolute

862 ELECTRONICS & WIRELESS WORLD No chargetoevaluate repairs. Noextra premium foremergencyrepair work. No limitonthetypeof motorised products we'll repair. No needto testrepaired items. No high levels of inventory. No lengthy downtimes. No problems, in fact. That's what Omega service abilitymeans.

Yes, we have been repairing and refurbishing all your motors for over a generation. Yes, our service expertise covers all your electronic and electromechanical requirements. Yes, we are a BSI 5750 registered company. Yes, we do have a highly -skilled technical team to solve all your difficulties. And yes, we are in the forefront of technology... scanticipating your future needs poses no problems.

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The dynamic force in motion. ENTER 52 ON REPLY CARD

15.5 centre101UeVelOpIllelllUlI CICIIIMILS =1A4 Hi " /HZ + /H4 ;increment HULL HLLLH L L L ; 17 ;Loop A3 * /A1 + /A4 * A3bit3 Bangalore HLLLH HLLHL L L L ; 18 ;here /AO + /A4 * A3 * India HLLHL HLLHH L L L ; 19 ;until reset

ELECTRONICS & WIRELESS WORLD 865 FCIRCUITIDEAS CIRCUITIDEAS

subcarriers on satellite tv broadcasts, butvided by the 'audio output' through the loop FM quadrature i.c. with modified values, it may be useful forfilter. With values shown, the simple Col- works as a p.1.1. n.b.f.m. pitts voltage -controlled oscillator operates Inside the chip are a limiting amplifieraround the i.f. of 10.7MHz. detector and phase detector, so by adding an external Values of C1,2 were determined empirical- v.c.o. and loop filter a phase -locked -looply for various frequency deviations and the Normally, the CA3089 and its many deriva-demodulator can be realized. loop filter was optimized for high-fidelity tives are used as quadrature f.m. detectors, In the circuit shown, i.f. input is con-music. Threshold performance is consider- and work well where distortion is the prim-nected as usual so the a.g.c. and signal -levelably better than the quadrature detector, but ary design criterion. In some applications,outputs function normally. One input of theof course distortion is much greater. however, noise and threshold performancephase detector connects internally to the i.f.;M.L. Christieson are more important. This idea was designedthe other input comes from the externalCrowborough for demodulation of weak wideband audiov.c.o. Control voltage for the v.c.o. is pro -East Sussex

-612V

100 A =150kHz Ci =68P C2 omitted A 50kHz Ci = 22P C2 =10P Audio output to de -emphasis stage 11

1 If amplifier 10u Phase 1 and detector II From limiter 1 i.f. filter 330 47k

3 1 Bias 10 -1 47k 10k Ci 22p CA3089 6 1 1n IHA12411etcI 15k

13 15 41 51 14j

1k

a.g.c.meter 4n7

Loop filter Oscil ator

NEXT MONTH Magnetic heading sensor. Using a pen- Interfacing and signal processing with dulous flux valve detector to obtain a C. Programming in C has many advan- direct -current heading signal for air- ELECTRONICS tages;thisarticledescribes how to borne telemetry. The device is compact, & WIRELESS WORLD exploit the language in interfacing a can be remotely sited and is free from microcomputer to the outside world. e.m.i. emissions. Telemetry heading sensor

Fast Fourier ast Fourier transforms of sampled tnnsforn of sampled Butterworth low-pass filterwith signals. A proceduretoenablethe waveform, equalization. Kamil Kraus shows that a accurate determination of unknown fre- Remotely low-pass Butterworth with equalization quencies. The author suggests that the controlled Wien oscillators leads easily towards the implementation f.f.t. algorithm does not require a re- Optocoupling of a higher -order crossover filter. peating waveform and that the waveform in automatic in the window is "considered" in isola- test equipment tion. Pioneers - J.C.Mameell Bi-directionalopto-coupling. Ifyou Remotely controlled Wien oscillators. A need to avoid trouble with earthing and novel Wien -bridge oscillator design us- noise,opto-couplingcouldbethe ing analogue switches and photoconduc- answer. But if there is a computer and a tive cells to provide a coverage of 10Hz text fixture at each end, it might not be to 1.3MHz. easy; R.A. Beck shows the way.

866 ELECTRONICS & WIRELESS WORLD Fast logic probe

Putting the logic of a logic probe into a p.I.d. results in a fast and versatile unit no larger than much simpler designs.

13.J. FROST

Recently, in a popular compendium of Equivalent circuitry inside logs block PAL electronic circuits I found no fewer Logic input than 24 logic -probe circuits. With so many logic -probe designs around, I feel that IC2B 3 I must first justify my version. Its main IC2A 2 feature is that it captures pulses too short to Logic valid 02 r-7478 7404 display on an oscilloscope. Sometimes simp- ly connecting the capacitance of an oscillo- 7404 scope probe removes erroneous pulses and causes a faulty circuit to work perfectly - 10 until the oscilloscopeis removed. Being 111B IC20 Low built around a programmable -logic device. 6 7404 5 the probe is small and simple, yet it includes :Cc Logic valid pulse -analysis features. 7408 7404 Two types of pulse that I frequently en- 7404 counter are problematical enough to justify 1C3A the probe's pulse -detection facility. They are Logic pulse Logic delayed glitches.i.e. pulses that cause erroneous 2 circuit operation, and pulses such as proces- 7486 sor chip -select signals. Neither type of pulse is easily made repetitive, and although pro- Pulse set inL. 114A IC2F Pulse indication cessor strobes can be made repetitive by 3 13 12 suitable programming, some means of de- Reset pulse lat- 2 tecting these as single events certainly justi- 7600 7404 fies adding to the logic -probe circuitry. A major feature of the probe is its ability to IC4B classify pulse widths into several bands; the 6 probe differentiates between fast glitches, This circuit repeated typical processor strobes and strobes that are 7400 three times too long to be valid. Of these pulses the glitch is the most important since the probe must illustrate the presence of pulses that Fig. 1. Logic of the logic probe is program med into a pal to save space. affect present-day advanced logic such as 74F and 74AC series. Most logic probes have a pulse -indication facility based on either a monostable multi - Probe circuitry falls into two sections, device will always be set on any pulse and is vibrator or pulse -stretching principle.If namely the logic -state indicator and the used together with a reset time constant to only edge indication is required, a 74F or pulse analyser. Circuitry shown in Fig. 1 and clear all the bistable devices after a predeter- 74AC bistable i.c. with a delayed reset pro- the peripheral components of Fig. 2 will give mined display period. vides about the fastest detector. This sim- you an insight into the operation of each plicity diminishes though when detection section. Logic -state indication is simply a PROGRAMMING THE PLD from any input edge is required. matter of determining whether the probe Any circuitry that responds to both edges input is high, low or. with the aid of a Other articles have described the principles must preserve the bandwidth needed for window comparator, open circuit. Leds in- behind programmable gate arrays so I will glitch -detection. When the basic logic -probe dicating the logic state are driven directly. not give the full programming process. List level -detecting circuitryis added to the Being based on a set -reset bistable device, 1, produced using a simple text editor, is pulse -detection circuits, it becomes difficult the pulse analyser is almost as straightfor- passed through a proprietary logic -compiler to accommodate the number of chips re- ward. Probe input passes through an program and a programming file is produced quired inside a reasonably -sized case. It is exclusive -Or differentiator which produces a forsending to a device programmer. not surprising that simple transistor -based low -going transition on any probe input Advantages of this method of logic imple- probes are so popular. transition. This output feeds directly to the mentation are apparent from List 1, where Each probe function requires only simple first set -reset bistable device which is im-you can see that the device inputs and logic, but brought together, these functions mediately set on the shortest input pulse andoutputs are declared first with a pin name represent an untidy mixture of gates and so provides glitch detection. assigned to a pin number in quite arbitrary inverters. This mixtureisideal for im- Four more set -reset bistable devices are order and with a polarity that is indicated by plementing in programmable logic. My fed with the differentiator output but viaan exclamation mark. Thus pin 1 is the probe design has a single programmable - increasing CR time -constants, such that logic -probe input, true high, and pin 2 the logic array providing the logic -probe func- only pulses that exceed each time -constant feed from the window -comparator circuitry, tions and pulse -analysis facilities with few will set the corresponding bistable device but true low. The two leds indicating the additional components. and illuminate its led. The glitch bistable logic state connect to output pins 12 and 19,

ELECTRONICS & WIRELESS WORLD 867 Tri-state check and input protection

.5V Input supply to probe

R14 P1 8 0A47 Low drop -out regulator Pulse display LM393 LM2931Z-5.0 IDA Pulse Pulse Pulse Pulse 1 2 12 Ti Glitch 5V 14 13 5V 100p R13

C7 C8 C9 C10 330 R 330 R 330 R 330 R5 2k2 LM393 1p 10n 10n /16

OV R20 100k 1C1B Ds D

Logic block UI

Logic input 1 12

Valid logic 2 13 RaTie 3

IlTe 3 14 PT f2

Logic delayed 4 15 NE-re Pulse 16 Pulse GI RI Pulse Ilse 6 17 Pulse T2 set 7 18 krrilTeTT: ogic display 1M5 C41p ulseT3 set 8 DulseT4set 9 .5V

OV 11 19 R9 R7 330 Pe 330 Logic state constant Allows probe to detect pulses 100RC2.r 16V8 /1 In of either polarity OV 06 07

VO Low High

R12 T 141-C1.r 1n 1M5 C5 1p R10 +0V OV Glitch is any pulse 100k T1 is pulse >100ns Pulse reset constant c3.r1n T2 is pulse >1ps Determines length of time - OV P11 13 is pulse>100ps that pulse indicators are lit T4 is pulse >10 ms

C6 100n . 0V .Eg Lattice GALI6V8-25LP Pulse time -constants

which are both true low, and the equations by another with correct connectivity but Fig.2. These simple interfacecircuits that relate their indication to the input with a more hidden actual function. connect to the pal to form the complete states are: The logic equation for implementing such logic probe. a bistable device tends to look like this: /* drive HL display leds directly from logic flexibility that makes pal devices so attrac- input'/ /* latch any pulse at all */ tive. Another advantage of this logic defini- pulse_C = (pulse_C & !reset_pulse) # high_led = logic_input & logic_valid: tionisthat the logic compiler used to low_led = !logic_input & logic_valid: pulse_C_set: translate these equations into device data An ampersand indicates the logic And func- Here. the output pin of the bistable device also allows a file of test highs and lows to be tion and an exclamation mark indicates ('pulse_C') appears on both sides of the hypothetically placed on the device input inversion. Thus the 'high_led' pin is true equation, indicating its latching capability. pins and a print-out of the effect on the (pin 19 goes low) when the 'logic_input' pin The hash sign represents the logical Or output pins to be obtained prior to program- istrue(i.e.pin 1 ishigh) And the symbol, and the equation output must be- ming the device. Such simulation provides a logic_valid' pin is true (pin 2 low). Com- come true if the input pin 'pulse_C_set' good chance of first-time success. pare this with the logic -gate equivalent becomes true, irrespective of the state of the Implementing discrete logic with pal de- circuit of Fig. 1 and the similarities should output: this is the SET action. Presence of a vices is an interesting and rewarding sub- be clear. true 'reset_pulse' causes the expression ject. A useful publication containing data This principle can be used to synthesize '!reset_pulse' to become false and any and applications information is the AMD any logic function and the bistable devices self -latching cannot be maintained: this is Programmable logic handbook, available are constructed in a similar way, but need the RESET action. This equation is directly free to designers. slightly more explanation. When seen on a equivalent to a cross -coupled Nand -gate pair A fast mos version of the popular 16L8 pal circuit diagram a set -reset bistable device is and displays exactly the same instability of providing up to 18 inputs or 8 outputs is often drawn showing a cross -coupled gate output when both input lines are simul- used here.Its mos inputs provide little pair which conveys both the essential sym- taneously low. loading to the probe tip and allow conve- metry and the circuit connections. Some As with any program listing these equa- nient CR network component values:its drawings do not, or cannot illustrate a gate tions and pin definitions are easily changed high speed provides pulse detection down to pair in this way and place one gate followed without changes to hardware, and it is this single nanosecond figures.

868 ELECTRONICS & WIRELESS WORLD List 1. These equations, representing the logic within the logic probe. are used to produce the fuse plot for the programmable logic device. OOKS I" Inputs /** Pin 1 = logic_input; I' high is high. low is low - Pin 2 -- !logic_valid: /* low if a valid logic level ..' Circuits, signals and devices by Michael Pin 3 -- !reset_pulse, /'true to reset the pulse capture * Julian (of Bristol Polytechnic). Longman

Pin 4 - logic_delayed: I' delayed i/p provides auto pulse info Scientific and Technical, £14.95. Well -filled Pin 5- !pulse_G_set I' set pulse glitch latch textbook on electronic engineering for first Pin 6- !pulse_t1set / set pulse tl latch and second year degree and diploma stu- Pin 7 = !pulse_t2_set / set pulse t2 latch *. dents, designed to meet the need of readers Pin 8 - !pulset3set I' set pulse tl latch *.r approaching these topics for the first time Pin 9 - !pulset4set I' set pulse t2 latch : although not geared to any particular sylla- I" Outputs **/ bus. The author's treatment is primarily / descriptive. but he supplies extensive mathe- Pin 19 !high_led: / high display led matical support as well. Text is comfortably Pin 12 !low led; /' low display led set out with many diagrams. An attractive Pin 17 !logic pulse: /' pulse circuit drive'/ feature is the statement of learning objec- Pin 16 - pulse_G: 1' low if pulse at all '/ tives which appears at the start of each Pin 15 = !pulse_t1; / low if pulse _AI 'I chapter and the list of key points to remem- Pin 14 = !pulse_t2; / low if pulse >t2'1 ber at the end. Soft covers, 515 pages. Pin 13 = !pulse_t3: / low if pulse >t3 Pin 18 = !pulse t4: % low if pulse >t4'/ / Logic Equations / Programming Windows:the Microsoft ; drive HL display leds directly from logic input / guide to programming for the MS-DOS high_led -logic_input & logic_valid: presentation manager. Windows 2.0 and low_led = !logic_input & logic_valid. Windows/386, by Charles Petzold. Microsoft /' generate pulse drive from exclusive -Or of input and delayed input / Press (Penguin Books). £22.95. Weighty logic pulse -(logic_input & !logic_delayed) technical manual for the C programmer, # (!logic_input & logic_delayed): providing detailed coverage of all aspects of / latch any pulse at all*" Windows in comprehensible form. Section pulse_G = (pulse_G & !reset_pulse) # pulse_G_set headings include basic concepts (creating I' latch any pulseti i and displaying windows), getting input pulsetl- (pulse_t1 & !reset_pulse) # pulse_tl_set /* late). any pulse .A2*/ (from keyboard, mouse and timer. using pulse_t2= (pulse_t2 & !reset_pulse) # pulse_t2_set resources (memory management, icons. / latch any pulse :>t3 / cursors, menus, dialogue boxes), the

pulse t3 - jpulse_t3 & !reset_pulse) # pulse_t3_set graphics device interface (bitmaps. meta - / latch any pulse >t4 files. printers and fonts), data exchange and pulse_t4 (pulse_t4 & !reset_pulse) # pulse_t4_set links. Soft covers. 852 pages.

The programmer's PC sourcebookby Thom Hogan. Microsoft Press (Penguin Books), £22.95. Excellent all -in -one reference work for the PC user, covering chips and hard- ware, interfaces, DOS commands and util- regulator. Due to their current -mode out- HARDWARE DETAILS put. low -dropout regulators are prone toities, disc usage, function calls and support tables, interrupts, mice, extended memory All of the circuitry can he built into a probe instability if the required decoupling capaci- (Lotus -Intel -Microsoft) support. and Micro- case like the one available from RS and other tances are not present. soft Windows. The informationis exten- suppliers, and is easily accommodated on For the best glitch -catching performance. the piece of perforated board that comes ensure that the shortest possible ground sively indexed and cross-referenced; details of sourcesaregiventhroughout. with the case. The leds can he glued into wire connects the probe circuit to the circuit Soft covers, 525 pages approximately A4 size. small holes drilled in the case in groups of under test. This connection performs the two (for the state indicators) and five (for the same function as the ground clip on an pulse display). All components are easily oscilloscope probe and has the same charac- obtainable except for the pals; I will he happy teristics: i.e. it can be ignored for general. The early British radio industry by Rowland to supply these for readers without program- uncritical checks, but if working with nar- F.Pocock. lanchester University Press. ming facilities (details later). row pulses with wide bandwidth it is essen- £27.50. Early means pre -1900. the era when A small amount of power supply circuitry tial. Remember that all common logic fami- the main customers for radio equipment is shown in the diagram. Any 5V logic supply lies except 4000 series c-mos have an edgewere Europe's navies. The author, tracing could he used to power the probe directly but rate -of -change that is equivalent to band- the development of the infant art and the to ensure that it does not suffer damage, the widths in excess of 100MHz. government response to it (the British Gov- supply circuitry shown should he included. A programmed pal for this design can heernment's, mainly), provides a political and It consists of a low voltage -drop regulator obtained by sending £9.99 to Dorset Design economic history rather than a technical which only loses about 0.2V at full current and Developments at 8 Rohinswood Drive. one: no diagrams or photographs illustrate and a germanium diode to provide reverse - Ferndown. Dorset BH22 9RZ. This price his text. Did you know that Britain's indust- voltage protection. includes postage and packing. rial decline was recognized as long ago as Probe input thresholds remain at 1/3 and 1867, and was even then being attributed to 2/3 of 5V whatever the supply voltage, hut a failure to encourage scientific and technic- supplies above 8V should not be used for al education? Those who ignore the lessons extended periods. Do not omit the luF Brian Frost is ttith Dorset Design and of history are doomed to relive them. Hard decoupling capacitors on both sides of the Developments covers. 184 pages.

ELECTRONICS & WIRELESS WORLD 869 TECHNICA. The Complete SYSTEMS LTD DIGIAC 1050 Introductory

Trainer

The DIGIAC 1050 features: - Self cor tained module with steel case and integral power upplies. Two curriculum texts available - FT02 - An AcCelerated Introduction to The DIGIAC E ectricity/Electronics FT04 - A Comprehensive Study of the Fundamentals 1050 has been o' Electricity/Electronics specifically 26 independant circuit blocks with different configurations covering resistors, capacitors, designed to inductors, op amps, diodes, relays, transformers and provide a single digital logic circuits. self-contained On -board switched faults - concealed by a lockable cover. trainer that covers Screen -printed circuit layout. a.c./d.c. fundamentals, Comprehensive Instructor's manuals available for semiconductor circuits and digital electronics. both curriculum texts.

For full details on the DIGIAC 1050 send for LJ Technical Systems Ltd. our full colour brochure or call us on Norwich Francis Way, Bowthorpe Industrial Estate. (0603) 748001. Norwich. NR5 9JA. England.

ENTER 24 ON REPLY CARD HIGH QUALITY Toroidal LOW PRICES & E.I. 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 9.12, 30va 9.48. 50va 10.16, 80va 11.02, 120va 4 1-11GHz SATELLITE TV 12.23, 160va 14.44. 225va 16.37, 300va 18.05, 500va RECEIVING EQUIPMENT 26.46, 625va 30.66, 750va 34.14, 1000va 49.40. Also available 1k2, 1 k5, 2k, 2k5, 3k. Prices on request. RECEIVERS, LNB's, LNC's, Available from stock in the following voltages: 6-0-6, FEED HORNS, ANTENNAS, 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. ANTENNA POSITIONERS, 240. Primary 240 volt. POLOROTORS, LINE AMPLIFIERS, ETC. Quantity prices and delivery on request For further details contact: HARRISON ELECTRONICS Century Way, March, Cambs PE15 8QW Air Link Transformers Unit 6, The Maltings, Station Road, Tel: (0354) 51289 Sawbridgeworth, Herts. Tel: 0279 724425 ENTER 22 ON REPLY CARD ENTER 25 ON REPLY ('MU)

ELECTRONICS & WIRELESS WORLD APPLICATIONSSUMMARY

.lcc1 SLEEP \la 2 I 31-4 3,4EN ;41 1N4935 I pk=VRs Vref /RS 1Y

Vref .(R3/(R243))X5V 1PR Chopper frequency=036/(R6xCi) SN74HC112' 3Y 10 4A *I unused inputs hgh) IC 2a 1PR 10 3A SN74HC''. 10 ICsa a STEP SN74HC 386 1CK SN754411 L293

2PR DIRECTION 20 1A 2CK Motor 28Orn4/phase with series 2Q 2A resistance and inductance of 3711 1C5b and 80mH respectively ICTh 1,2EN

L TLC 3702 IC 6b 5V 10k Oscillator Ds -8 All 1N4935 104 39k 10n 20( 20

4 2K IC2b OR33 R Vref 620 10k VRS

Constant -current EMI suppression Series stepping -motor drive Capacitance inductance Capacitor type (nH) Residual inductance in a capacitor, which (P.0 A brief stepping -motor overview, a circuit depends on electrode construction and lead Leaded monolithic ceramic0.01 5 for normal and half-step motor control, and Leaded monolithic ceramic 1 6 lengths. combines with the capacitance to Leaded disc ceramic 0.0022 4.5 this constant -current driver circuit are con- form a resonant network. In e.m.i. suppres- Polyethylene tained in the application brief for TI's terephthalate film 0.03 9 sion applications, this resonant point can SN754411/L293 stepping motor controller/ Mica 0.01 52 significantly reduce the capacitor's effective- Polystyrene film 0.001 12 drivers. Polystyrene film 0.1 100 ness. Motor -winding LR time -constant causes Solid tantalum 16 5 Aluminium electrolytic motor current to respond slowly to stepped These illustrations, from Murata's "EMI countermeasure" guide, give residual in- for r.f. use 470 13 inputs. Consequently, during high-speed Aluminium electrolytic 470 130 ductance values and insertion operation, motor speed may never reach its losses of typical two -terminal capacitors. rated value. This chopping circuit allows the motor he be operated from a high -voltage For a publication of its size. the guide does sion techniques and explains the advantages not contain much text, hut it iswell provided supply, so afaster current increaseis of three -terminal capacitors. Data sheets for possible. with large illustrations. It presents a sum- many of the company's suppression devices mary of ti ,e fundamentals of e.m.i. suppres- Audible motor noise is avoided by correct are included. choice of frequency -determining compo- nents R and C 120kliz). Peak motor current 0 is set by Vim.. and R,. Tantalum C

20- Al electrolytic Osc C 147p) Vref Monolithic ceramic C (1p) VRS Monolithic ceramic 60-, chip C1101

Monolithic ceramic chip C (10n) 80- 0 Monolithic ceramic - C (10n)- - 1w 100,

05 1 2 5 10 20 50 100 200 500 1000 OV FREQUENCY (MHz)

ELECTRONICS & WIRELESS WORLD 871 APPLICATIONSSUMMARY

Small -area networking Hardware for a simple small -area network ri nter Net work can consist of little more than a number of driver access universal asynchronous receiver/trans- node node mitters capable of operating in 'multi -drop' mode. Such a network is the subject of note AN990 from Motorola, entitled "A small -area network using the MC68681 duart." In multi -drop mode the serial frame bit. Clnormally used for parity checking, signals an Net wor k Printer Net work address when high, or data when low. This access driver access node node node feature allows a number of terminals with receiver/transmitters to be linked serially to the same controller and individually written to. With a simple polling mechanism, the terminal controller can also determine 1421=116 whether individual terminals have informa- tion to send back to it.

Ram Address Addres 2Kx8 switches Motorola St Martin's Way, Cambridge Rd Bedford MK42 OLF 0234 47188 Muirhead Vactric 38 Croydon Rd. Beckenham Kent BR3 4BE Rom 8Kx 8 01 650 4888 Texas Instruments Technical Enquiry Service Manton Lane, Bedford MK41 7PA 0234 223000 Murata Electronics 5 Armstrong Mall Southwood Farnborough. Hampshire GU14 ONR 0252 523232 Ire

set of charges within the cells. These repre- sent the position of the pattern, and its corresponding moire fringes. The c.c.d. correlates the pattern position with a prede- termined reference position on the disc.

Optical shaft encoder Minimum charge transfer with five -second Maximum charge resolution transfer Normal rotation encoders rely on sensing brochure called "The Microgon Encoder", is radial coded slots or holes on a disc. Ina 38mm rotary position encoder with a contrast,a new encoder technique de-resolution of 4.94 arc seconds (the first units veloped by Muirhead Vactric involves should be available early in 1989). charge -coupled sensors arranged in a ring so On the encoder disc are two concentric that sensing over the whole disc surface is tracks -a pseudo -random binary track and a possible. bar track - which form the moire fringes by Resolution is further increased by takinginteracting with the c.c.d. elements. The advantage of the c.c.d's analogue sensing light source is pulsed to form instantaneous nature. The results, described in a briefpattern images on the c.c.d., resulting in a

ELECTRONICS & WIRELESS WORLD 872 Pioneers

21. Alec H. Reeves, 1902-1971: inventor of pulse -code modulation.

W.A. ATHERTON

Tune in or fade out: that was the advice edge. or better still,by just one short given by Alec Reeves in 1971 to en- fixed -duration pulse whose position relative gineers and managers to help them to a fixed time represented the amplitude of face the next fifty years of electronics. Reeves the signal at that instant (Fig.1). This tech- himself was a man highly tuned to his nique, known as pulse -time modulation or subject. He was the inventor of pulse -code pulse -position modulation, was used in modulation and conceived the idea of the many early s.h.f. radio links. wartime Oboe precision navigation system. Pulse -time modulation was an important His keen sense of the way ahead for telecom- invention but it did not solve the original munications was evident again in 1960 when problem since noise could affect the position he led a team on a then futuristic project to of the pulses and so produce distortions. achieve communication using optical waves. These effects would be cumulative if passed The advent of lasers and fibre -optic cables through many repeaters. Reeves still wanted eventually made that possible. C.K. Kao, the to approach the telegraph situation where father of fibre -optic cables, was employed at only the presence or absence of pulses the same laboratories and has recalled the mattered: for that he needed not only to inspiration of working among men such as sample the signal but also to convert the Reeves (see Pioneers 16, Electronics & Wire- amplitudes of the samples into some sort of less World April 1988). telegraph. To do this he needed analogue -to - For that next half century Reeves foresawAlec Reeves at the age of 63, holding a digital and digital -to -analogue converters. personal global telephone numbers which circuit board from a demonstration model He now fell back on his earlier work at would go with you anywhere in the world, of a p.c.m. system (by courtesy of STC designing counting and timer circuits using and 700 -line opto-electronic picturephones Technology Ltd). the Eccles -Jordan bistable. These he com- in colour and with stereo sound. For mass bined with pulse -time modulation (p.t.m.). storage he suggested 1012 bits per cubic By converting the analogue signal to p.t.m. centimetre as an achievable long-term digital timing and counting circuits. In 1927 and measuring the time intervals with his ITT opened new laboratories in Paris to target. That would enable an hour of colour counter he designed an analogue -to -digital which Reeves was transferred. There he television programmes to be stored in a converter. Similarly he showed how to con- stayed until the German takeover in 1940. cubic centimetre of material. The ultimate vert back from digital to analogue. In his would be .one bit per atom, and there are 1938 patent Reeves suggested a sampling P.C.M. around 1022 atoms per cubic centimetre in a frequency of 8kHz (twice the baseband fre- solid. Generally what was needed to face the In Paris the ITT group was looking at ways of quency of 4kHz ) and 32 amplitude steps (25). next half century, Reeves suggested, was a using the s.h.f. and u.h.f. bands for radio P.c.m. did all that Reeves had asked of it revolution in thought. telephony links. The main problem was except for one thing:it was difficult to Pulse -code modulationis one of thenoise. Ever since A.G. Bell's invention of achieve with the technology of the day. foundation stones of modern telephony. It "speech -shaped current" the telephone had Widespread implementation had to await the has especially good immunity to noise and used analogue circuitry. Frequency -division era of cheap transistors and integrated cir- has been used to transmit pictures and data multiplexing had made multiple channel cuits. By that time the STC patents had from space. The first American photographs transmissions possible. But to Reeves. expired and STC made no money from from Mars came via a p.c.m. system. telegraph -style pulse techniques, used with them2. After the war p.c.m. was developed in Reeves's patent was filedinParis on 3 time -division multiplexing, seemed an a number of centres, especially atBell October, 1938, though he had conceived the attractive alternative to analogue methods. Laboratories where its feasibility was proved idea the previous year. As you read this, Pulse -amplitude modulation was tried and in 1947-1948 by a team led by the famous p.c.m. is 50 years old. found to work, but the varying amplitudes of Harold S. Black, inventor of the negative - It may seem strange that a British inven- the pulses suffered from noise as badly as did feedback amplifier. tor filed his invention in France but the analogue techniques. explanation is simple enough. At the time he In 1937 Alec Reeves came to the conclu- OBOE was working in Paris at the laboratories of sion that what was needed was a return to the International Telegraph and Telephone the fixed amplitude pulses of telegraphy. In 1940 Alec Reeves fled from France leaving Corporation (ITT). They had great tolerance to noise since they his belongings behind - although, I am told, Alec Harley Reeves was born at Redhill in were either there or not there.Digital a suitcase was returned thanks to help given Surrey, on 10 March, 1902. He graduated telephony became his target. by "a man he met in a pub". He joined the from Imperial College, London, in 1921 and Today's preoccupation with digital techni- Royal Aircraft. Establishment at Farn- two years later joined the International ques makes it hard for us to imagine the borough but was transferred to the Telecom- Western Electric Company. This was part of mental struggles that such ideas posed fifty munications Research Establishment then ITT and the forerunner of Standard Tele- years ago. Reeves first tried using the width located at Swanage. There he was in charge phones and Cables (STC) and its laborator- of the pulses to represent the amplitude of of a number of groups of which one, Group ies, STL. There he worked on the first the signal (Fig.1). This is now known as 17A, had the task of developing a new commercial transatlantic radio telephone pulse -width modulation (p.w.m.) He soon long-range blind bombing system conceived circuit and was one of the first to use the realised that the width could be represented by Reeves and code -named Oboe. By now he Eccles -Jordan bistableflip-flopto build by short pulses for the leading and trailing had laid aside previous qualms about work -

ELECTRONICS & WIRELESS WORLD 873 ing on offensive systems. The operational Marshal "Bomber" Harris later wrote, "Bom- system was worked out by F.E. Jones in ber Command's main offensive began at a discussion with Reeves in April -May 1941 precise moment - the moment of the first Signal but the principles came from Reeves. Air- major attack on an objective in Germany by borne trials began in September. a remark- means of Oboe". It was a far cry from a able tribute to the small team which had comment in one headquarters file written at produced all the equipment'. the time when the principles of Reeves's idea An enormous amount of work and re- was being considered. Perhaps worried by sources were needed to develop and use the transponder needed inthe aircraft. Oboe even though its principle was remark- Pulse amplitude I whose transmissions could be detected by ably simple. Oboe relieved the bomber crew modulation the enemy, a Government scientist wrote of of the responsibility of deciding when to Oboe. "If I had the power I would discover release the bombs and gave that job to the man responsible... and sack him so that ground -based radar operators hundreds of he would no longer waste not only his time miles away from the action. The entire and effort but ours also by his vain system relied on very accurate distance Pulse width imaginings"1. Instead of being sacked. modulation measurement of the aircraft by two widely - Reeves was honoured with the OBE in 1945 separated radar stations and on knowing the for conceiving the most precise bombing

Pulse time 11 111 1 111 11 111 exact range of the target from the two modulation system of the war. stations. This latter requirement necessi- tated the accurate alignment of the Ordn- SAINTLY Pulse code 11 L 1. 1111 1 1 1 1 ance Survey with the continent of Europe - modulation 1000 00.,, Bic; 1c00 whilst the war was raging. A raid on After the war Reeves rejoined STL where he stayed until his retirement in 1970. After Florennes in Belgium (described by R.V. Fig.1. The path to pulse -code modulation. that he formed his own consultancy and Jones in his book Most Secret War) helped Over a couple of years in the late 1930s performed work on optical communication check this alignment. Reeves progressed towards digital tele- systems for the British Post Office until his Oboe made use of the fact that British phony by a series of steps including mod- ulating the amplitude, the width, and then death on 13 October. 1971 at Harlow in radar could make range measurements bet- Essex. He had no next of kin. As well as his ter than it could make directional ones. As the position (timing) of pulses. Finally, in two main claims to fame, p.c.m. and Oboe, the bomber neared its target it flew on a p.c.m., only the presence or absence of he held about 100 patents and had worked on circular course at a fixed distance from radar pulses mattered. the first short-wave radio telephone link station A (Fig.2): this would ensure that it between Spain and South America. passed over the target, or rather just short of Reeves has been described as "saintly". It it to allow for the tangential motion of the is a poetic description and one which does falling bombs, which were usually dropped not spring easily to the lips of engineers from 30 000 feet. Signals from station A told "If I could find the when describing colleagues. Professor K.W. the pilot whether he was on track or to the left or right of it. A second radar station. B. man responsiblefor Cattermole has written that anyone who knew him would remember his kindness and also tracked the bomber: when this was at this fantastic Oboe I generosity, his charitable work, personal the correct range from the station the signal integrity and sincerity. He devoted time. was given to release the bombs. would sack him..." money and emotional commitment to help- Oboe was tested over bombing ranges in ing rehabilitate young delinquents back into Wales and near Stranraer, the latter some the community and bore the breaking of 250 miles from the radar stations. Practice trust with the faith that "the right thing to bombs dropped by Mosquito aircraft from do was the right thing to do". He was a keen 30 000 feet gave an average radial error of Fig.2. Oboe. By means of a transponder in mountaineer and encouraged a love for sport 150 yards.3 the aircraft, radar stations A and B could in young people, and did not mind recalling The first Oboe -controlled sortie against both monitor accurately the distance from being beaten at discus -throwing by a 12 - enemy targets took place on 20 December. them to the bomber. Flying along a curve 1942. By the end of the war the RAF had centred on A. the bomber released its year -old girl. He received many honours besides his flown about 10 000 Oboe -controlled raids bombs when instructed to by station B. For which had marked the targets for nearly the Florennes raidin December 1942 OBE: a CBE, honours from the American IEEE and the Franklin Institute, and a 120 000 bombers. The US Air Force had also station A was at Trimingham and B at trophy and cheque from ITT. The most used Oboe on more than 1600 missions. Air Walmer. unusual one however was a British postage stamp and first-day cover issued in 1969 which commemorated one of the most im- portant inventions in modern telecom- munications - pulse -code modulation.

References I. K.W. Cattermole, Proc. IEE. vol.126. 889-892. September 1979. 2. P. Young. Power of speech: a history of STC. Allen & Unwin, London. 3. F.E. Jones. unpublished paper lby courtesy of SIC). 4. R.V. Jones, Most secret war, !famish Hamilton. London. 1978.

Next in this series of pioneers of electrical communication: James Clerk Maxwell -A British scientist second only to Newton. Tony Atherton works at the IBA Harman Engineering Training College. Seaton. Devon.

874 ELECTRONICS & WIRELESS WORLD Multiprocessor systems In this third article, Alan Clements looks at how microprocessors communicate with each other.

up to now I have been looking at the topology of multiprocessor systems \ vith little or no consideration of the actual connections between the processors. Here I describe some of the ways in which processors are linked together and examine the various issues involved in linking them.

COUPLING Possibly more than any other factor, the required degree of coupling between proces- sors in a multiprocessor system determines how the processors areto be linked. A tightly -coupled multiprocessor system passes data between processors either by means of shared memory or by allowing one processor to access the other processor's data, address and control buses directly. When shared memory, sometimes called dual -port ram. is employed to couple proces- sors, a block of read/write memory is arranged to be common to both processors. One pro- cessor writes data to the block and the other reads that data. Data can be transferred as fast Fig.1. Processors linked by a shared bus. as each processor can execute a memory access. LaterIwill look at the design of 0 Parallel data link dual -port ram and the problem arising when Thatis.latencyis the time that elapses 0 Parallel data link with fifo buffers between both processors try to access the same block of between a processor requesting a data transfer processors memory simultaneously. and the time at which the transfer actually 0 DMA channel The degree of coupling between processors takes place. A high degree of coupling is 0 Shared bus is expressed in terms of two parameters: the associated with large transmission band- transmission bandwidth, and the latency of widths and low latencies. As you might expect. 0 Shared common memory Here. I will describe only interprocessor links the interprocessor link. Transmission band- tightly -coupled microprocessor systems need involving shared memory or buses. width is defined as the rate at which data is more complex hardware than loosely -coupled moved between processors and is expressed in systems. SHARED BUS bits per second. For example, if a 68000 writes The way in which processors are linked can a byte of data to an 8bit parallel port every 40. be listed in order of their degree of coupling as One of the most popular ways of tightly - the bandwidth of the linkis8bitf4lits or follows: coupling processors is to permit two or more 2Mbit/s. However, if a Ifibit port is used to 0 Serial data link processors to share the same bus in an move words at the same rate, the bandwidth arrangement of time -division multiplexing. rises to 4Mbit/s. Fig2. Processors linked by a block of That is, the bus is allocated to a processor only Latency of an interprocessor link is defined shared memory common to both proces- for a fraction of the available time. as the time required to initiate a data transfer. sors. It is possible for more than two processors

A D

A

CPU A

A -address D- data C- control Jai Ram

ELECTRONICS & WIRELESS WORLD RIW F2/1,;2 RAW.] ENABLE.] Address ENABLE 2 buffer ADDRESS2 ADDRESS,' 1

R/171 CS

Dual port ram

D1R DIR Data It Data buffer buffer

1

Access Access AS2 request Myles+ Arbiter il5S2 Mer DS2

1

'T4C1(2 Arbitration clock

Fig.3. Structure of a shared memory common to two processors. to share the same bus, allowing the general ory and operate on their own data. When one SHARED MEMORY bus topology to he realized: this is why the processor wishes to communicate with shared bus is so popular. It should he im- another. it takes control of the system bus In the final method of linking two processors a mediately apparent that if a number of proces- through its bus -control unit. Now itcan block of memory common to both processors sors do try to access the common bus all the access the resources of another processor by is used. As I have already stated, common time, the throughput of the individual proces- controlling the system bus. memory is often called dual -ported rani. sors will be very low. When I introduce the VIEhus in a later Fig.2. It is, in fact. possible to have n -ported Figure 1 shows how a shared bus system is article, you will see how the 68000 bus control ram thatis shared between n processors. arranged. Each of the three processors. A. B facilities hilt lei and ismck) simplify the designBecause multiprocessor systems based on and C. has its own local buses through which of multiprocessor systems. shared memory have very h 1W latencies due to it accesses its own local memory and. possibly. their tight coupling. I will discuss the design i/o ports. For much of the time. the processors Fig.4. Timing of an indivisible test and set of multiprocessor systems with shared mem- execute programs stored in their local mem- (TAS) instruction. ory in more detail.

DESIGNING MULTIPROCESSORS S7So St Si 53 Sz, S5 S6 57 $859 SlO S11 S12 513 S1: S15 Sx, St2 Sts Si*si_ WIT! I SI IARED MEMORY

CK In the example of Fig.2. the two processors have entirely separate buses together with their own local memory and i/o resources as A1-23 appropriate. However, each processor is also

AS asserted for duration cc TAS cycle able to read from or write to a block of dual -ported memory common to both their address spaces. Figure 3 provides further details of the arrangement of this memory. For the sake of simplicity,byte -selection details are not included. Each processor in Fig.3 has its own data and address bus buffered on to the dual -port ram buses by means of two pairs of three -state buffers. Processor I accesses the dual -ported memory when ENABLE! is asserted and proces- sor 2 accesses the dual -port ram when ENABLE., is asserted. As the outputs of the buffers are Data from memor y Data from 68000 connected together, only one set of buffers at a Indivisible read /modify/write cycle time may he enabled. Therefore. both proces- Internal sors cannot access the memory simul- Read memory operation Write to memory taneously. 101 ,1 Inputs cs and RAV to the dual ram are also buffered by three -state bus drivers. However,

ELECTRONICS & WIRELESS WORLD s76 in this case it is necessary to pull up both Ls and kW when neither processor is accessing the bus, in order to avoid spurious memory accesses. IC3 PRE 0 D ARBITRATION RECITgE1 CK CK!CR) So far so good. The real problem in designing a a shared memory system lies in the selection

of a suitable mechanism by which a processor Arbitration K is granted access to the shared memory. Each clock processor in Fig.:3 may attempt to access the PRE AN. 1.1.Nand Los BB dual -port ram by asserting its REQUEST2 a ENABLE 2 lines and by placing the appropriate address CK 1C2a CK 1C2b onAl a Access requests from both processors are fed to an arbiter circuit to decide which processor will he granted access to the shared CK memory block. Some arbiters have a clock input (not necessarily the system clock) that determines the points at which the request inputs are sampled. That is. the requests are sampled periodically by a sampling clock. This Fig.6. CircLit diagram of a two -input asyn- and must wait until the memory becomes clock has important implications for the chronous arbiter taken from a Motorola free. When both processors request a memory reliability of the system as you shall soon see. application note. Latches ICI, are driven access almost simultaneously, the arbiter If one processor requests the memoi-y and by a non -inverted clock signal and latchesmust decide which processor may proceed the other does not, the requesting processor is IC2,1, by an inverted clock to ensure that and which must wait. granted access. Equally. once a processor has REQUEST? and REQUEST? are not sampled at the The arbiter is an interesting device, not been access, the other is locked out same time. least becauseitis impossible to design a Fig.5. Arrangement of dual -ported ram in a multiprocessor system.

PU2 Bus to CPU1 Bus '

IIIM11114 41ff

LS245 LS245 Ram Ram Data Data buffer A buffer 3 1 32k x 8 32k x 8 DIR Upper byte Lower byte

CS 1,T.'

DIR E DR Data Data buffer buffer 4 2 LS245 LS24

R/W1 R/W LS244 LS244 U UDS Address Address and 071 and LDS control control buffer buffer 7 0-11 "1 5

CS (active when shared memory accessed I E E

Address Address buffer buffer 6 8 Lc24. LS244 ENABLE 1 I I ENABLE 2 4 1. Arbiter Request) Reques

Address Address decoder decoder 2 1

DTACK1 DTACK2

ELECTRONICS & WIRELESS WHOA) 77 cessor B does the same. Processor B will read 8Ons the semaphore after A has read it and it too will set the semaphore: each will think that it 125MHz has sole possession of the shared memory. CK 1_,T5111 -L-11_11 The above is not a theoretical, abstract or irrelevant problem. It has serious consequ- 12.5MHz - ences in multiprocessor systems. For exam- CK ple, in a geographically distributed system a Requesti travel agent may aks for a seat on a certain Request? gets bus Idle gets bus Idle IdleContention flight. The computer system interrogates the data base and finds, say, a single seat free.

REQUEST1 which the client then hooks. But suppose that in another town a second client also requests a seat on the same flight. He or she may be told REQUEST2 that the flight is free because the first client has not yet booked the seat. The outcome is that the seat becomes double -hooked. A Fortunately, most data bases have software that avoids this dilemma. Once a client has asked if a seat is available, that section of the B data base cannot he read by another user until the original transaction is fully completed. The 6800(1 microprocessor has a test -and - AA setinstruction. TAS.designed specially for multiprocessor applications. ATAS instruction reads the contents of BB the specified effective address and, if clear. sets the least -significant hit of the byte tested in one indivisible operation. That is. it does not E NABLE release the memory between the action of reading the semaphore and that of setting it.

ENABLE? The action carried out by a T.Ns instruction is called an indivisible read. modify and write operation. Figure 4 provides the timing diagram of a Fig.7. Timing of a dual -ported ram arbiter. TAS instruction. which lasts a minimum of 20 perfect arbiter. It is an asynchronous device is in use by another processor and is thereforeclock states and includes a conventional write access followed by a conventional read access. because a processor may request a memory unavailable. Like any other memory access, both read and access at any instant if its clock is independent In order for processor A to take control of write operations can he extended by delaying of the arbiter's clock. Therefore, there is a the shared memory.itfirstreads the data -transfer acknowledge signal ifrAcx as re- finite probability that a processor may request semaphore. Remember that both processors access at the exact moment ( in practice a can physically access memory. subject only toquired. However, unlike other read-followed- is not finite sampling window) that the arbiter is the state of the arbiter. If the semaphore is set.hy-write cycles. the address strobe negated between the read and the write making a decision. In this case, the state of the processor A must wait. since B is already using accesses. Therefore, in any multiprocessor system is undefined. the memory. If the semaphore is clear. proces- system using shared memory, the arbiter No matter how well an arbiter is designed. sor A may take control of the shared memory must he arranged so that it will never recind a the problem of a simultaneous access request by setting the semaphore and thereby locking processor's access to the shared memory and sampling clock edge can never be elimin- out B. ated. Simultaneous changes at a bistable Simple? Well. not really. Assume that pro- while its address strobe is asserted. device's data and clock inputs are called meta- cessor A reads the semaphore and finds it stability. It is possible however to reduce the clear. Processor A will then perform a write MEMORY ARBITRATION problem to acceptable limits. For example, an operation to set the semaphore and to gain An arrangement of a practical dual -port ram arbiter may be designed that fails once every. possession of the shared memory. Now sup-with 64Kbyte of shared memory is given in say, fifty years. A mean time between failureof pose that at an infinitesimally small periodFig.5. Two 32K -by -Shit i.cs provide the 32K 50 years represents, of course, a high degree of after processor A requests the memory, pro-words of shared memory and eight bus drivers reliability by everyday standards. Note that a form the electrical interface between the ram failure due to a metastability problem is a soft Fig.8. GeneratingDTACKina dual -portedand processor I or processor 2. Processor data failure. ram. Another problem associated with shared of memory, common to almost all forms Iii*t) when CT.,1 and multiprocessor systems. is in ensuring reli- U ,t/CM) asser ed REOUEST1 Vcc able communication between the processors (E1) via the shared memory. For example, suppose UDS1 that processor A writes a block of data to the LOS1 dual -port memory for processor B to read. SHIF T

Processor A will want exclusive use of the ENABLE 4 shared memory for the entire duration of this from arbiter operation. Since processor A cannot lock out 12.5MHz arbiter clock processor B by a hardware technique,itis necessary for A to pass a message toB. High when UDS1/ LD'i asserted during Ut indicating to it that it wishes to have sole access by Processor 1

access to the memory. DIACK1 Typically a flag bit, called a semaphore. tiltl Select l;nk for aDpropriete delay forms one of the memory locations and. when set, indicates to a processor that the memory

ELECTRONICS & WIRELESS WORLD 878 indeterminate. The metastable state can last lines are buffered by 74LS245 bidirectional outputs of both Or gates (A and B) going low for up to about 75ns before the output of the transceivers, whose data direction inputs are simultaneously. The cross -coupled feedback latch settles into one state or the other. For controlled by the BAN signal from the processor inputs to the Or gates (ENABLE' and EN 11iI.E., ) are this reason a second pair of latches is used to bus to which they are connected. The data currently both low. sample data at the input latches after a period buffers are enabled by ENABLE' when processor On the next rising edge of the clock, the Q output of latch ICL, (i.e. As) and the Q output of 80ns. 1 has access to the memory and by EMMY, Thus. 80ns (one clock cycle) after REouEsr, when processor 2 has access. of latch (i.e. BB) both go low. However, as sees a rising edge clock first. its Qhas been latched and output Bis forced low, the Address lines.s!13 from processor 1 are latch output of latch IC'h. ENABLE., goes low. Its buffered by two 741.5244 octal three -state bus output goes low one half a clock cycles (40ns) drivers enabled by Emmy'. Lines Al 13 from before latch IC is output also goes low. complement. EMISI.E.i. is fed hack to Or gate IC.;, forcing input .s high. After a clock cycle is processor 2 are similarly buffered and enabled Earlier. I said that when a latch is clocked at also goes high. Because ENAISI.E2 is connected to by EMI the moment its input is changing, it goes into latch IC h's active -low preset input, latch IC Three 74LS244 three -state buffers are re- a metastable state in which its Q output is quired to buffer the 15 address lines and the Ills and LDs control lines from the proces- Fig.9. Timing of DTACK during execution of a TAS instruction. sors. Each of these three lines is pulled up to a logical one state (on the ram side of the buffers) by resistors, to avoid accessing the CPU1 ram when neither ENABLE'nor ENNBLE2is CK -11-1:11-1-5111-L-ULF asserted. CPUI-H Two Or gates (And gates in negative logic Ai_:3 terms) permit the processors to perform byte or word accesses to the ram. These gate upper data strobe VI PS with cs from the arbiter to AS1 j select the upper byte. and Los with cs to select the lower byte. LIDS1 Address decoders 1 and 2 are driven from [5Si J processor1 and processor 2 address buses respectively. Each decoder is enabled by its own processor's address strobe. For example. R/1741 if processor 1 requests a memory access by addressing the 32K block selected by address C St decoder 1. the decoder output (op.:sr'is REQUEST1) asserted. Assuming processor 2 does not require the bus. the arbiter asserts ENABLE' and F111 (reset shift reg I buffers 1. 2. 5 and 6 are enabled. This permits processor 1 to access the memory exactly as in any other access to static ram. Note that es ENABLEI from the arbiter is asserted to enable the ram. AArbitration delay if either ENABLE' or ENNBLE., is asserted. Should processor 2 request the ram. the action is SHIFT

identical to that above, except that buffers 3.4. DTACK idelay DTACK delay 7 and 8 are enabled by ENNRLE.,. Figure 6 is an example of an arbiter for OTACKI \A 1 dual -ported ram. taken from Motorola ap- plication note AN881. Each processor em- ploys its address bus together with Ns and Fig.10. both arbitration logic and memory refreshing areprovided by the 74LS764 strobes ros is to produce a memory access controller. request whenever it wishes to write to or read

from the shared memory. Memory request DTACK signals BEQuEsri and worEs-L. are sampled by two positive -edge triggered latches. The latch to he clocked first locks out the other latch. so Port SE Li that the latter cannot respond to a request at Access its input. The secret of the arbiter is its use of request D ram and REQ1 control an antiphase clock to provide different sam- grant SE L2 Arbitration pling points for the request inputs. signals logic Timing for the case in which both proces- RAS/CAS/MP>, RECI2 timing sors request the bus simultaneously is shown GNT in Fig.7. As you can see, processor 2 wins the

request and processor 1 must wait until processor 2 has relinquished the bus. That is. RCK (Refresh ck)

processor 1 does not have to try again,it CK simply waits for the memory to become free.

Processor 1 determines that the bus is once ROW/COL more free by the eventual assertion of its data -transfer acknowledge signal. Initially, the arbiter is in an idle state with Address latch both request inputs inactive -high. Therefore. Memory A2 and both 1) inputs to latches are high and in address row/col MA0-6 mpia a steady state condition. Outputs A.in. ENABLE' Address to and EN.Vil Esi are all high. d -ram Suppose thatItic.(tasiiand IfEquEsT.,are asserted almost simultaneously when the clock is in a high state. This results in the

879 ELECTRONICS & WIRELESS WORLD is held in a high state. At this point. ENUL.F:I is negated and Assert SE Li to asserted, permitting processor 2 to access the grant REri.1 bus. The access is completed by the genera- tion of a ofwK I(described later) and by the negation by processor 2 of its AN and rl,Jl.us outputs.

When processor 1 relinquishes the mem- RECO ory. HEouEs-r., becomes inactive -high. causing J first then nu and finally i svtl.Ey to he negated

as the change ripples through the arbiter. SELL Once ENABLE, is high. ENARLE2 goes low. causing the output of Or gate IC:; (i.e. s) to go low. This is clocked through ICI,,_,, to force Es 11tI low GNT and therefore permit processor 1 to access the memory. Of course. once I'.\.\III.EIis asserted. and assertion of mocEsT., is ignored. RAS The remaining aspect of the dual -ported

ram to he considered is the generation of WG irrAciii and la by the arbiter. Many circuits (Write gate( which produce a 1,1 uK response to the asser- tion of the processor's address strobe follow- ing a valid address would nut he suitable for a CAS dual -ported ram. A glance at Fig.4. the timing 5 diagram of a TAs instruction. reveals the diffi- DTACK culty unique to TAs. This is the only instruction that requires two handshake cycles (one to acknowledge the read cycle and one to ack- Fig.11. Timing of the LS764 arbitration sequence. nowledge the write cycle) while As is con- tinually asserted. Fig.12. Dual 68000 system using a 74LS764 controller.

Vic d Refresl- clock T

WALK

C P DTAIK R P RE01 RE 02 Decode

LS764

SELL 57.

A1-18CASEN RAS WG MA 7.8

3 -state 3 -state buffer buffer 74F 1244 74 F1244 or Or 74F 244 A 74F2,4

F139

t

Data Data buffers buffers 74F 245 74F 245

I US WE A0..8 CZ RAS WE A0.8 Ri aA0.8 CZ RAS tit. A 0.. 8 CAS 256k x8 256k x 8 758k x 8 256k x8

SS() III( Iiji)\ It.N.A. uillt1 I) Figure 8 shows how DTACK1 for processor I is not in progress and the other request input generated from ups' (or UN), REQUEST', and is not active, the so. output corresponding to Conferences ENABLE' from the arbiter. Basically, orAcki is the active iico will go low to indicate that the generated in the normal fashion by holding a access will he granted. Output (.NI then goes and Exhibitions shiftregister (741S164) ina clear state high and its low -to -high transition indicates whenever Koms-ri (i.e. csil is inactive -high. that a memory cycle is about to begin. and then using the shift register to shift a If an access or refresh cycle is in process8-12 November,Munich:Electronica 88,13th fairfor components and clock pulse along when it is enabled. In this and the other processor has not requestedinternational trade assemblies in electronics. Associated conferences case, the shift register is also reset when ill's' access by asserting itsxi:o signal, the NEL output corresponding to the active Ho will include sessions on quality assurance, component and Los' are negated. Consequently, the cir- testing techniques and sensor elements for mass - cuit generates the two consecutive MACKI.S go low to indicate that access will be granted.market products. Organizer: Miinchener Messe- required during a TAS operation. Figure 9 However.,Nii. will not go high until theund Ausstellungsgesellschaft mbl I.Messe- provides a timing diagram for the IYMK current cycle has been completed. Aftergelande, Postfach 12 1009. 0-8000 Munchen 12. generator. Note that irmk., is produced in an completion of the current cycle. (NT willte1.189) 51 07-0. identical way. except that the shift clock is automatically be asserted high. derived from the complement of the arbiter If access to the dynamic ram is requested22-24 November,IEE, Savoy Place. London: clock. by both processors. the initial arbitration fourth international conference on electricalsafe- Now the hardware design of a dual -ported phase determines which processor is to gaintyin hazardous areas. An accompanying exhibi- ram is complete. In use it may be accessed by a access to the memory by asserting the tionisplanned. Details from the conference secretariat. IEE Conference Services, 01-240 1871 processor as follows: appropriateSEI. output. This arbitration takes place irrespective of whether or not aext. 222. Shared - EQU $F00000 Location of refresh cycle is in progress at the time the memory memory access is requested. Request contention is25-27 November. Windermere:Institute of block arbitrated, as discussed earlier. by samplingAcoustics 1988 autumn conference onnoisein and abound buildings. Institute of Acoustics. 25 Sem DS.WI First word= the loio inputs on opposing phases of the Eli11HU. semaphore arbitrer's clock. Chambers Street. Edinburgh When GNT becomes active -high, address inputs II1, are latched by the74LS764 and20-22 December,University of Nottingham: In- theNI 9 signals propagated to theNIN stitut.. of Physics annual solid-state physics con- ference. Details from the loP in London. 01-235 LEASemi, (AO) Point to row -address outputs. One half clock cycle semaphore later. column -address inputs on AI -1,; are 6111. Wait TAS (A01 Test and set propagated to m and the active -high semaphore column -address strobe. cAs. asserted. Once23-25 January, 1989,Bahrain: Middle East Elec- BM1 Wait Repeat until os is asserted, the controller will wait three tronic Communications Show and Conference. semaphore clock cycles before negating los. making it incorporating the Middle East Commputer Show. Ltdin set four clock cycles in duration. Contact: Overseas Exhibition Services As RAS is negated, the MACK output becom- London. 01-4861951. }Critical es active -high to indicate that data on the section 23-26 January. 1989,Bahrain: Middle East Elec- dynamic -ram data lines is valid (or that thetronic Communications Show and Conference. proper access time has been met). All con-incorporating the Middle East Computer Show. troller outputs are held in their final state in CLR.B (AO) Clear Contact: Overseas Exhibition Services Ltd until the processor accessing the dynamic semaphore London, 01-4861951. ram negates its REvsignal. When the request The address of the semaphore is loaded into is negated, all controller outputs assume25-26 January. 1989.Fleming Park. Eastleigh: \IP and the TAshimi loop repeateduntil the their inactive states and any impendingInstrumentationSouthampton. Details from Tri- semaphore is found to have its seventh hit refresh cycles are serviced. dent International Exhibitions Ltd in Tavistock. clear (i.e. mil w ur not taken). When hit seven A refresh cycle is triggered by internally0822-614671. Further dates in 1989 for exhibi- of the semaphore is clear it is set by the rs to generated refresh requests. The refreshtions in this series are 22-23 February at the enable the processor to take control of the clock is divided by 64 to produce periodicHarrogate Exhibition Centre. 21-22 March at Filton. Bristol. and 14-15 June at The Forum. shared memory. refresh cycles and then arbitrated with the The next part of the program is called the outputs in the second stage of arbitra- Livingston. critical section because it is the region that tion. 7-9 February, 1989.Wembley. London: surface must he executed to completion without any Refresh cycles always take priority overmount and related technologies exhibition and other processor accessing its data. Once the processor accesses. At the start of a refresh conference.Smartex.Details from MGB Exhibi- critical section has been completed. the cycle, the 9bit refresh address is placed ontion Ltd. 01-302 8585. Prospective authors of shared memory is de -allocated by cry r I vi) >1%,,,; for a half clock cycle and then its isconference papers should submit a 200 -word which resets the semaphore. asserted for four clock cycles, followed bysynopsis to the chairman of the technical commit- three inactive -high cycles. The inactive -hightee. Smart Group. 3 Lattimore Road. Wheathamp- DYNAMIC RAM CONTROL period of 1( %, allows time for the dynamic ram stead. I lertfordshire ALA 8OF. Both arbitration logic for dual -port memory precharge period. I introduce VMEbus and look at some of20-23 February. 1989,Genoa. Italy: European and the controller and interface to a block of Advanced Manufacturing Systems Exhibition and the special-purpose i.cs that simplify inter- dynamic ram are included in the 74LS764 Conference. Cahners Exhibitions. 01-891 5051. facing 68000s to VMEbus in the final section dynamic -ram controller. Fig.I0. Request signals ur:oi and woare the of this series. 21-24 February, 1989,Birmingham NEC: Which access -request inputs from ports 1 and 2. Computer?Show. Cahners Exhibitions. 01-891 and sm.! and sEI.are the corresponding 5051. access -grant outputs. All other inputs and outputs are largely self explanatory. Typical 6-9 March, 1989,Swiss Federal Institute of timing of an access by processor 1 is shown Technology. Zurich: 8th international Zurich in Fig.11 and a circuit diagram of a dual symposium and technical exhibition on electro- 68000 system based on the 74LS764 is magnetic compatibility. Details from EMC Sym- posium Zurich. ETII Zentrum - KT. 8092 Zurich: shown in Fig.12. teL (Switzerland) 01-256 2790/2788. A microprocessor requests access to the Alan Clements BSc.. PhD.. is a Reader in the dynamic ram by asserting the appropriate School of Information Engineering at Tees- mi) input. If a dynamic -ram refresh cycle is side Polytechnic.

ELECTRONICS &WIRELESS WORLD 881 A dimensional approachto aunified theory

Dimensional relationships of common physical concepts.

S.K. CHATTERJEE, M.A.

Itis possible to reduce the conventional The expressions for Newton's Law P = mf The expression for m = L3/T2 is derived by dimensional expressions,in terms of and Einstein's Law E = mc2 can be expressed Clerk Maxwell' as follows. If (as in the metric length, time and mass (inertia) or force, to as P = m1114 and E = mL2/T2 and, substitut- system2) the unit of mass is defined by its terms containing length and time only. Some ing m = L3/T2, we obtain for these two laws attractive power, the acceleration of a mass m advantages accrue and tabulating the result- at a distance ris by Newton's Law m/r2. ing expressions in the way shown in Table 1 n L3 L L' P = X = Suppose this attraction to act for a very small clarifies relationships previously obscured by T- T- T interval of time t on a body originally at rest, the complexity of a three-dimensional format. and and to cause it to describe an interval of space The chart does not show all the many s, then by the formula of Galileo scientific concepts now in use, since itis E. I m intended primarily to be introductory and G = A t.2 T- T- I 2 r indicative: but it will.I hope, interest those familiar with the dimensional techniques now increasingly being used. It is obvious that all the non -dimensional parameters and numbers, such as Reynolds. :ATTIC canna,

Froude, Densitometric Froude, Richardson. srtra TOMMY,.

etc., are merely ratios of the values tabulated TNITETTON I and that they are finitein number, for practical purposes. Although the tabulation lataLarran ear= T. L.ranarrwrn can extend to infinity, the concepts suscept- mamma 1111Cyle011011 TOLIA111 VOLUM WOGS TYCT SPESTFIC VOLLTIT IRIOCITTI I111 ITOOTTRACT ible to measurement are confined to the first TONSIMLITT 110,011, TOTIPLTION six powers on each axis. ULF MOM= What is perhaps not so obvious is that the I table also shows the laws or rules of Nature TLOTTIRICAL CallTOCITTITT TITS 141.11(0 araterrnrr and theirrelationships as interlinked by 11111111110 Newtonian calculus. One can make several deductions from the tabular array, but it is

COMITITTS1 LTTV WON TOMO enough to point out here that it might have 6161111102 been preferable for scientists to use a natural Sin MI unit of measurement based on Napierian e, IT L.I and a representative velocity such as c or, L T more accurately, the constant for the ratio of VOLANI. MT TANA length to time for the particular case; and in general in the study and measurement of IMKT= FULD

natural phenomena. TES'M 1 YOOLILII ATTSLTIOATION MUT 011.1111/01TT ilegATIS The Michelson-Morley experiment, and VOLUM 11.11811T MIKA =MTV MB/ subsequent endeavours to establish the velo- city of light and other forms of electromagne- tic radiation, are open to another interpreta- tion - that of establishing a ratio of length to time in this universe. In this paper the 0 0 L. L.T. meaning of these experiments is to be taken as 0 L. 0 establishing the connection of the dimension length to that of time in an absolute sense, instead of its being measured in units familiar L.0 L.0 0 0 L.0 to the scientist. Those units are arbitrary, despite the attempts of Wren and the Abbe Pittard in 1670 AD to relate the unit of length to the unit of time by the beating of a 0 0 L.0 L L.T. pendulum in a gravitational field. That these experiments, such as the Michelson-Morley, have also established that the value so obtained is a physical constant of the universe is accepted.

882 ELECTRONICS & WIRELESS WORLD hence G = I (non -dimensional). Alternative - whence P=G -Gmm x ly. GM = cm3/s2. but M = m = L VV. so again 9f s . L m - ,I.e. M = -r. T - = I . that is, volume (L') and density (1/12) con- =c11::11L2=6 L! T' Although Heisenberg believed at least three jointly, which is in line with Newton's defini- 1 V / 1 fundamental constants were necessary to tion for mass ("Quantitas materiae est mesora determine the masses and the other prop- but ejusdam orta ex ilius densitae et magnitudine erties of elementary particles (e.g. atomic conjunctem") in his Proposition I in ref.' (see nuclei of the lighter elements)itis only also p.5inref)). Inpractical units necessary. as will be shown later, tohave two- T' 1 T-/ 1 T- Heisenberg4 confirms this when he takes the measured values of Planck's constant and the velocity of light, assumes a length of roughly ATONIC MNVIIIONT 10-13cm. and forms an expression which in its MCNMOMAL 10110DTN. dimension corresponds to a mass, its value MTPOIT MY STUMM!me being of the order of magnitude of the masses TIRENNAL COPYL111. name rien leallirrre DOLTTIONN 6COORTJUIT inarTre. Of Intern of the elementary particles. In dimensional terms this becomes

TONfonason =WIWI fLNCTRIC MTNITSITY Olanerie ROW velocity of light cm/s L/T T. ACMILIDATIOO Felarnn nnenetar Olr.inaT rinfnefe Planck's Constant erg/s L 'IT twoucTue= length cm L whence Mmmc rua Cann Ottnillien COIrrirener rinnrrir viSODorre rOLO Mann lailefirrtTe neem .01.11.rre Otennrrire reionne IWMIOILITT CISCOLOTION °Men,' or naCTUCTIT elerairre IltxLI=f

a..comer CONDUCTITIT, tcrorno oterucerrere T noon. vir.OrTri iticrolc rifOocelom In these circumstances where mass has the VORT:CtTl MONITTC INDUCTION NACMITIC ODIN IITIMMTINI rowan money dimensions of L'/T' the Gravitational Con- MDCMCNCT stant G is non -dimensional. since':

Mechanical

Diffusivity L2/T

IT 0 T L L3/T2 Acceleration L/T2

TI Le Tr Lt T. 0 Dynamic viscosity L2/T3

Electromagnetic L2/ T L Tjt Electric flux

///'' \ Magnetic field Magnetic p.d. Magnetic flux L/T2 L2/T2 L3/T2 N -TM 011001/M an,ireneel Moreno noonloce noternina Ibl .."/// Electric field MR. L2/T3 TfLOMIT IMMNIM MCOONISATINO OOMPTICIMIt MONITIC MOOTTa Mr TOLL* NMOTIC NOMINT

NOLDDOLD NININTIOLT T.7

° =TM OATINT ° I yl --f-111:111TCP. MIDOMM Or INSTOTULLAND MOOONNTIoN 10 NIMOBTICIMINT Om VINT Of MOIL Thermal COMM TOLTO CoMMOI MTIOMTV OMM MILTMC MN MR MOW I Thermal diffusivity

a. .1j nworscomunJJ mO, MMOMM Nome or anon CLIOONT ONONINTV 101nomneram antan Itileilite IND. eomo. =WWI OMMTM Monne mean MMMOIR. ACTION IMMO orneerennanMOM ONO4 Temperature Entropy Ortenoneno Onforree renal an maMOMne ma nmoncOan gradient

MINNS 1TINOITT MOTO., MOM NIOtOrIT NoONLENT Mina TOMB.ON MASTIC NONNI= COMMON COMM, TOACTIT Thermal conductivity IMINOCM/UNIT LIMN

Electrostatic

MEM Magnetic flux

Electric field Electrostatic Electric flux P.

Magnetic field

883 ELECTRONICS & WIRELESS WORLD namely length and time, and their ratio. dimensional form in Table 1 - which is to he As11depends on the physical characteristics So far I have dealt with the dimensions ofunderstood as one entity embracing all others of the media, it is more accurate for experi- mechanical quantities. and it must be stressed which are manifested as Hilbert geometries in ments carried out under terrestrial conditions that only those properties susceptibleto space and time. to calculate the value of the masses of the measurement are being investigated. Other From the time of Newton, for whom the elementary particles using these values rather meanings of the worddimensionare not Book of Nature was written not in mathema- than the constant c, that is, m = E I.LE rather applicable to this enquiry. tical symbols but in the form of a cryptogram, than m = E/c2. The dimensions of entropy, the heat weight and of Boole, who believed that dynamical and Table 1 of the unified theory extends to plus of Zeuner (defined as i)(,)/01'1. are derived from other actions seemed not only to be measur- and minus infinity. It still has many gaps such the equation (dQ/Blx = work done orable in themselves but also to be connected to as the entities of chemical, biological and energy, where itC)is the quantity of heat.each other, even to the extent of mutual social sciences. However, provided that these whereas those of temperature t) are derived convertibility, it is perhaps only now that it is can be expressed in terms of dimensional from PV = mRt) where P is pressure, Vpossible to display - through tabulation in equations including, if unbalanced, one or volume, and R is the Universal Gas Constant (aterms of L, T and c - the fundamentally more constants, the values of which are pure number). Thus using P = IL'/T1)x UV, abstract nature of the entities of science in the determined by dividing one side into the V = L3, m = 1,3/T2. R = 1. gives= L2/T2, and form of Hilbert spaces of many dimensions. As other, it will be found that these constants entropy = LIT2. These are then substituteda consequence, one obtains a consistent either turn out to be non -dimensional num- in the dimensions for thermodynamic con- theory applicable to the very large and the very bers or to have dimensions in terms of L, T or cepts. small. uniting the many concepts susceptible c, which are then substituted into the original Since electrostaticpermittivityp.and to measurement by a dimensional approach to equations to give a dimensionally magnetic permeability E are essential lyof the a unified theory. homogeneous expression. In many problems same kind or quality. and p. E = 1/C-,,itis Omitted so far are Planck's large numbers the time element (1/1") can be disregarded, reasonable to substitute p. = 1/c and E = 1/c in for L, T and M, which relate all three entities but it becomes significant in studies of the the electrical entities. through Planck's Constant. the velocity of very large (cosmology) and the very small There remains one more step before I can light and the gravitational constant.in (nuclear physics), and in problems involving establish that Table 1 shows the interconnec- numerical terms measured in the c.g.s. sys- frequency. tions of the entities by means of the Calculus tem. as a further confirmation. I now express my great appreciation to Dr of Newton. Consider the volume of a sphere There are. Ibelieve, a number of other John Amson and Dr Christine Crow for its 4/377 r3, and its surface area 47r r2. One can see. expressions which are relevant to the under- help, to St Andrews University for the use of by extending these two expressions backwards standing of a unified theory based on dimen- its libraries, and to the members of ANPA and forwards that we have an infinite sequ-sions. and the ones which spring to mind for their courteous and critical appreciation of ence most readily arisein Heaviside's Impulse the views now made public.

4 1 Theory and his fascination with the special titr 8;Tr Orr' Wr case of Euler's Integral: 3 3 Symbols used or dimen- 8r 8rr 87r2 Kw,'87r' 8zr" -f-6!e sional variables standard MMass m mass 0 temperature 1 1 1.21.2.3 1.2.3.4 n! =e' L Length r,s length µmagnetic of terms found inthe expansion of the permeability exponential expression 8 r er or 8 r exp(r), i.e. TTime t time E electrical [X6 X5 X X 8 r exp (LI. Thus, on the horizontal axis in + +-+-+ + X + I permittivity 6! 5! 4! 3! 2! f acceleration G.K Universal Gravit- Table 1, there is shown ation Constant L L3 L1 c.v velocity k Einstein constant as a shorthand for the terms 8 w L"/n! Heaviside's final (unpublished) researches" Q heat R Universal Gas n= 12.... + x led him to formulate a unified field theory in Constant On the vertical axis of Table 1 there is similarly which electromagnetism is co -related with P pressure V volume shown mass properties and in which thereisa

1 1 1 1 1 reciprocal relationship between radiation and T T2 TI Tx matter. This is a somewhat similar idea to Professor Jennison's modelof an electron as The inverses of these L and T terms are also a phase -locked cavity: mass equals a volume References shown and yield Table 1divided into quad- (L3) and two frequencies 1/T,etic and 1/ rants indexed by L". 1/L". I. 1/T". Into this Of equal interest is Euler's Gamma 1. J. Clerk Maxwell. A Treatise on Electricity and table can be inserted all the modified dimen- Integral and its relation to the Logarithmic Magnetism. Vol. I. lst.Ed. Clarendon Press. Oxford, sional expressions in terms of L, T, and their Spiral, the Golden Section and the Fibonacci 1873. lArt.5.61. Vol.1. 3rd.Ed.Reprinted. Dover. ratio c, and the permutations and combina- Series. 1954. [Art.5.61. tions of these expressions which for most There is one more relationship which is 2. Anon. Going Metric. HMSO 1967. practical entities seem to be confined to the pertinent to this discussion, and which is as 3. Isaac Newton. Philosophiae Naturalis Principia Mathematica .Thirdedition. London1726. first six or eight powers. follows: An additional analogy which bears on the IDefn.l. ProP.1I interpretation of the tabulations is the Col- G = 1, 4. W. Heisenberg. Physics and Philosophy. Geo.Al- umn Analogy of Professor Hardy Cross' where NEWTON len & Unwin, 1958. 5. G.W.C. Kay & T.FI. Lahy. Tables of Physical and itis the mathematical identity between the G = K = kc2/87, Chemical Constants. Longman, 13th Ed. 1966 moments produced by continuity in a beam. EINSTEIN'" [pages 15.161 bent or arch, and the fibre stress in an and hence 6. J.A. Ewing. The Steam and other Ileat Engines. eccentrically loaded short column: this has C.U.P. 1922. [page 1221 the dimension L/T1. k= 1 /c2 = 7. Hardy Cross. 'The Column Analogy'.BuL215. Similarly, the equations of Poisson and CLERK MAXWELL Eng. Exp. Stn.Univ.of Illinois, 1930. Laplace have applications in several branches i.e. non - 8. H.J. Josephs. 'Some unpublished notes of Oliver and is the result of G being 1. Heaviside'. Heaviside Centenary Volume, I.E.E. of physics due to their dimensional identity in dimensional. This indicates that instead of each of the disciplines. They are equations of 1950. writing E = mc2 one should now write 9. R.C. Jennison. What is an Electron?',Wireless energy and have dimensionality L5/T1. World.June 1979. [page 471. Thus thelaws(e.g. Newton's) orrules(e.g. E= m. 10. A. Einstein. The Meaning of Relativity. Methuen Column Analogy) are shown in generalized & Co. 1950. [page 861

884 ELECTRONICS & WIRELESS WORLD APPENDIXA -PROPOSITIONS 1: TI IAT the ratio measured as the velocity of light. c, can be interpreted as a ratio of dimensions I. Novel power supply Length and T = Time in the study of natural phenomena, and that 'c' is TI IE basic physical constant. 2: THAT the dimensions of physical entities can he expressed in terms of a representative length L needs sponsorship and/or a representative time T. 3: TI IAT these concepts so expressed can he tabulated as shown in Table I. By switching capacitors using mosfets 't is 4: TI IAT the tabulation indicates that the entities are connected by a calculus (of Newton) and can he possible to build a power supply that is split to form entities of a lower order: for example: 'isolated' from the mains. yet does not need a 1.1 L'` L L I transformer. Transferring charges via - = x or -x - T T- T- I T switches is not a new method of providing 5: THAT each concept so defined exists in a space-time of a multi -dimensional geometry consisting of isolation - take the flying capacitor for scalars, vectors, quarternions (Hilbert spaces, in general). For example: (a) mass exists in a space example - but applying the approach to consisting of three dimensions of length and two dimensions of time (or frequency = I/T): power -supply design probably is new. (b) the quantum of action LIT.' exists in a space with five dimensions of length and three of time. Aubrey Sandman. who has applied for a being the time integral of energy f E dt. patent for the charge -transfer supply, says 6: TI IAT each of the geometries is conservative. e.g. exhibits conservation of mass. or of power. or of that switching -capacitors will simplify p.s.u. energy: hut that interchange occurs in physical systems. design and result in lighter products. And, if 7: TI IAT Table 1 provides a metric for an aether in which all the entities operate. his assumptions are correct. the theory 8: TI IAT throughout the tabulation there are time and length integrals and differentials connecting could also result in efficiencies approaching the concepts, and that these operate in general from minus infinity to plus infinity. 9: TI IAT is c is a constant. then LIT is constant. (Thus, if L increases. then T must increase to preserve those obtained from switch -mode supplies. the constant ratio. When T increases. la decreases in numerical terms. Therefore the greater the t' ut without the same r.f.i. problems.

distance over which L is measured. (i.e. frequency) diminishes. Thus there is a shift to the red in , Mains 'isolation' provided by the circuit is

the observed spectrum which cannot he equated to a velocity of recession as in the Doppler Effect). , of what most people would envisage as isolation, hence the inverted commas. By APPENDIX B-SIMILAR OPERATIONS isolation, Aubrey means that the positive Operation = Integration Differentiation and negative rails of the supply are always Mathematical L io isolated from the mains by a power mosfet in dx T x its off state. As a result, either the positive or negative sides of the supply could potentially Electrical * be connected to earth without causing cur- V = --1- V,.dt V - CR -CR rent in the neutral line. Mechanical Babhage 13abhage / W Unified Theory xLor xT x I/T or x

I. N.B.- = C and x - L or T * Equivalent electrical circuits

Integration Differentiation Then:

C lo- Vs Vo Vs R Vc,

L L 1 L T x = m I ( I T T T-

Examples (13) - He argues that by including protection P dl. = 11T' x I. = - energy or work done. - L' f < x x Ill ' - circuits, such as crowbars. the switching - I T I T capacitor supply could be as safe as a L' I L' . -impulse or conventional isolating supply. We pointed P - _ -x - = 1-y1 - WC ) 01, T' L T' momentum. lx out that BS has difficulties with the opto. L ' L ' isolator, which puts a piece of plastic be- 1E dI- x T - Planck's constant. x x tween the mains and the user, so it would T'' L 1 T T certainly find a semiconductor isolator hard

L' 1 L' , ac aUT 1 E x -- T. -= power. 7 n.b. - = - - to accept. Remaining optimistic. Aubrey said T ax a L T "I'll have to have a chat with BS". N.B. The quantities on the right -hand -sides are Although Aubrey has a working circuit, he isdecaying atthe rateK. Ifthe substance Will has one or two problems to sort out. For constant or conservative in any closed system. proportional to its concentration. then KAC is added to the right-hand of the equation. i.e. xample, to get the best results the power The equation of conservation of mass (sometimes mosfet pairs need to operate as close as called the convection -diffusion equation) K L. possible to their safe -operating limits may be written as KAC - x-x-- IT2 .e.K -1 T throughout the entire capacitor -charging If there are two (lows in opposite directions then cycle, providing a few milliamps while their m 1H2- -[ drain -source voltages are high and a few tIX (IX () = LT, ± amps when their capacitor is almost fully

la) ( ) (13) (y) ;aged. He says that he has this problem where isthemainflow.and Aisthe cross-section under review. The corresponding !most solved. where equation for conservation of volume. i.e. L'.is Another problem is that d.c. output from then the circuit is at 300V. On paper. Aubrey's L ;1 solution to this problem looks interesting. A ...area:C = = V...velocity: ;it ax but he has yet to work out the practical details. To develop his ideas further, he i.e. constant diffusion/concentration needs sponsorship. Is anyone interested? If L - m =-L ...mass: I)_diffusion so. telephone 01 608 1282. (T)/

ELECTRONICS & WIRELESS WORLD 885 PHILIPS PM3217 50MHz dual -trace. dual 21GHz Spectrum Analyser limebase oscilloscopes completewithcarrying systemtype1821 main cases. handbook and probe C400 each VAT frame with 8559A plug-in

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ENTER 38 ON REPLY CARD

Used equipment - with 30 days guarantee. Supplied with Manuals This is a very small (E) EPROM PROGRAMMER 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. OSCILLOSCOPES SPECIAL OFFER AT ONLY £300 EACH 1200: 02 5.. 114o. (I 0,. ' 15 000 III' [1000 16t., 15. 13 500 15= 13000 1st,, Is. (1000 110 (1200 11 000 TRIO OSCILLOSCOPES , ,, £ 1 200 0800 110 1600

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ELECTRONICS & WIRELESS WORLD Philip Smith's chart Having described the Smith chart in detail in thefirst part of this article in August. JW concludes by giving someexamples of its usage

JOULES WATT

Last month. I traced the development of circle on the chart, you get the bandwidth circle to position z,. Read off the impedance the Smith chart and showed how it is over which this aerial will operate for the as 0.72 - j0.53 which, on a 5011 system, applied to the presentation of condition before you connected the series would be (36 - j26.5) ohms. transmission -line impedance problems in a inductor, as well as that after. Now have a go at stub matching. A single visual manner. although it has many uses in The next example shows how a shift in short-circuited transmission -line stub pos- stability, matching and related problems in positionalonga transmission line changes sesses two variables - its length and where other types of circuit. Now, we can have a the impedance. Suppose you have a zi. of 1.8 you have connected it across the line. Both look at a few examples of the chart in - j0.5 and you want to know theimpedance parts of the admittance. the real and the impedance plotting and stub matching. at a point 1.1 back along the line. Enter the imaginary, come under control because of chart at this point inFig.12.By the way. the this. In particular, you can adjust the real angle from the entered point to either the 0 part to 1 and eliminate the imaginary part EXAMPLES or x position in the direction towards the altogether. Across the line is the operative generator defines the electrical length of the word. It indicates that we should work in You should find plotting impedances termination. This length gets you to a point terms of admittance, and that is how the straightforward. For example, the impe- of pure resistance, either the high value chart should be interpreted now. I have left dance z1, of a certain radio aerial might vary (choose x) or the low one (choose 0). I have this example as the general case; see Fig.13. with frequency according to Table 1. An chosen the open line, so the length is 0.28. Enter the chart at y!.. Immediately, you have impedance plot crossing the real axis of the The "S = 2" circle upon which z1, sits, shows the electrical length of y,, and the v.s.w.r. on Smith chart shows where your resonances the v.s.w.r. on the line. Move round the the line, if you want them. As you move back are. In this example, label the resonant chart a further 1.1 towards the generator. along the line towards the generator. even- frequency "1" on the aerial impedance plot, The impedance locus moves along the Stually you will strike the circumference of Fig.11. We have normalized values again - theg = 1circle. At this point yi = 1 + jb. If this time with respect to frequency. If you you connect the stub at this point, arranging now connect an inductance with normalized S LOAD for it to contribute a susceptance of - jb. reactance j1.4 at f = 1, in series with the then the line sees a perfect match at this aerial, the new impedance plot. zi.' 0 junction and the job is done. You on the chart, shows resonance qkt40, can easily see this form, lowered to about 0.875f. If 05 O. = gi. + jb!. you draw a maximum y! = 1 + j 1 tolerable s.w.r. Y. = y.. = yi + >7 = (matched)

8 -o

0

60 0

44Vietfrtiv; 4 0 4.:Alltl! 1&.:Al#0

The Smith chart as it is familiarly seen. You can buy books of them from the engineer- Si0-4" ing graphical suppliers

ELECTRONICS & WIRELESS WORLD Table 1. A typical list of impedance values with frequency for a microwave aerial. AERIAL I t

0 8 080116 11 1: 0.80 JO 48 0 9 090 11.26 0.90 10.26

1 0 120 100 1140 1 20 10 40 5

1 1 150 11 54 1.50 4. 12 54 1 2 117 13 38 220 1168 220 +J05 .J20

1 1 GHz L - 11.2 nH

You will not find sliding a stuh up and down .J30 coaxial transmission lines very easy. A stan- .J025 dard method to overcome this problem uses two variable short-circuit stubs atfixed J5 0 positions on the line, as Fig.14 shows. A number of people beginning the use of the Smith chart find the treatment of this double stub difficult to visualize (geometry again?). hut following it through the illus- fik4atlt trates the usefulness of the chart very well. Moving towards the generator through the distance di transforms the admittance of the !Vela load. yi., to some value yi across 1 - 1: see _J50 Fig.14 inset. Stub No 1 adjusts yi so that, at zi -10 25 further distance 1.2 hack along the line, an 04is admittance value y., appears across 2 -2 with 130 a normalized real part equal to 1. Therefore *op at 2 -2.y.. = 1 + jb., so that stub No 2 has the JO 5 111. J2 duty of adding susceptance - jb, there. so tuning out the + jh2 to leave a matched line. 1111-j1°5 We do not yet know the value of b2, but -1 whatever it is, y., at 2 -2 sits somewhere on Fig.11. The Smith chart allows the locus plots of impedances and admittances over the "g = 1" circle of the chart. To arrive wide bandwidths: the effect of changes can be instantly observed (especially with forward at position 1 - 1. the whole of the "1 automatic plotting equipment see last month's bibliography). circle has to move round the chart toward the load through the distanced.,in wavelengths, carrying all its circumferential points - including the unknown point re- levant to the problem. At this stage you can see how much susceptance stub 1 has to add across I - 1 to move the admittance yi along z= a constant conductance circle to get on to the shifted "g = 1" circle. This move arrives Zin at and identifies the relevant point. (There might be two points. How would you inter- pret the other one? On the other hand, 0 j2 suppose the move along the constant con- ductance circle failed to intersect the shifted "1" circle at all. How would you handle that?) .) Notionally, you now journey back along 0125+1 111:r.01240:71i0 the transmission line to position 2 - 2 .J5 0 carrying the known point back to the normal t< "g = 1" circle position. Stub 2 tunes out the remaining susceptance, as already men- I tioned, and this final move takes the point Towards into the centre of the chart. In other words, generator you have matched the line.

The Smith chart, then, after alittle practice, answers questions about impe- dance very quickly and with engineering accuracy. I hope you now agree that it forms -J0 25 Zin one of those 'analogue' applications that 041dhlr4 come through the 'digital' revolution un- 4111111#4015 ° diminished - in fact enhanced, as its regular appearance on computer v.d.us testifies. j05

z=-1653/1110_5 '311A

Fig.12. Finding the whole range of impedances anywhere back along a transmis- sion line (in other words, all the points on the circumference of the standing wave circle). as shown here, points up the value placed on the original use of the chart.

888 ELECTRONICS & WIRELESS WORLD Seminars, training Fig.13. The effect of the single shunt stub placed across a transmission line forms a courses classic first example of the use of the 20-23 September. University of Southampton Smith chart Microelectronics Centre. Practical course on cir- cuits and systems in silicon. Contact the confer- d wavelengths ence office at Sira Ltd. 01-647 2636. 18 October, Chislehurst. Kent. Tutorial on adap- tive and self -tuning controllers: principles and limitations of conventional p.I.d. loop controllers. Sira Ltd. 01-647 2636. 27-28 September. University of Essex. Colches- ter: STEbus applications seminar and trade ex- hibition. organized by the STE Manufacturers and .j 3 0 Users Group. Topics include networking, multi- .j0 25 proce:.sing. rom-based target systems, data- comms. system development using intelligent .j50 slaves. Details from STEM on 07357-4976 (fax 51551 or at P.O. Box 149. Reading. Berkshire RG6 31113. Among the summer events organized by the Institute of Electrical Engineers are vacation Towards generator schools on switching and signalling in telecom- munications networks 14-9 September. Birming- ham): measurement technology. d.c.to v.h.f. (4-10 September. Birmingham): telecommunica- tion network design and performance evaluation (11-16 September. Glasgow): electromedical technology 118-24 September, Canterbury). A -j0 25 school on plasma processing of semiconductor materials is being arranged for December. Details from the IEE in London. 01-240 1871. A series of one -day workshops on p.c.b. design tools is being staged at Cambridge by Iii-Tek CAE. Rate; this year are 22 September. 21) October. 24 November and 15 December. Fee is £200. Iii-Tek CAE. Dillon Walk. Cambridge CBS 8QD. tel. IC23-213333. Commercial courses covering a wide range of %A 0.15X subjects including artificial intelligence. super- 1s. computers. digital processing. communications and technology management are organized by Integrated Computer Systems. Fee for each two- day course is £250. Details from ICS Publishing Company on 0372-379211. European Silicon Structures offers courses on custom silicon design at is own premises or the customer's. Details from ES?. at Bracknell on 041-525252. Force Computers. which specializes in VMEbus products, has produced a brochure describing its training courses and seminars. Contact Force Computers (UK) Ltd. 1 !lolly Court. 3 Tring Road. Wendover. Buckinghamshire 111)22 (iPE. tel. 0296 625156. EVENTS Towards 14-16 March. 1989. Birmingham NEC: Internep- generator oil'. Semiconductor International. Special topics Y- 00 0 are hybrid manufacture. p.c.b. sub -contracting. .ind custom silicon. Both exhibitions will he accompanied by conferences. Details from Caliners Exhibitions in Twickenham on 01-891 5051. 16.17 March, 1989. Olympia. London: Cable & -j0.25 Satellite 89 exhibition and conference. The ex- -j3-0 hibition continues fm a further two days during which it is open to the general public. Details from Monthuild Ltd. 01-486 1951. -j05 -120 17-19 March, 1989, Brighton: Defence Oceanol- Wandt- movements along the line ogy International 89. embracing technology from 'Band if susceptonces shifted sub -sea to satellite. Spearhead Exhibitions, 01- shunted at 1-1 and 2-2 5 la 5831. by the stubs 5 -tiApril.1989. London: fifthInternational Fig.14. The double -stub tunerneeds a surprisingamount of thinking to see it Logistics Conference, organized by the Society of through. The chart helps greatly. Follow the argument in the text and you should I.gistics Engineers. Details from Consert. 57-61 Newington Causeway. London SE1 6131.. tel. 01- see what is happening. !32351.

ELECTRONICS & WIRELESS WORLD 889 60 MHz Universal Oscilloscope 2 Channels, max1 mV div.. Delay Line Component Tester. Timebase- 2.5s-5ns incl. x 10. Sw aDelo Triggering DC to 80MHz,e

The HM 604 is a new innovative general purpose oscilloscope satisfying a wide range of exacting requirements in laboratory, production. and service. The dual -channel measurement amplifier can be readily checked on the built-in fast-risetime 1MHz Calibrator from probe tip to CRT screen. Another important feature is the internal delay line for observations of the leading edge of a signal. As in dual -time base oscilloscopes. the HM 604 features a calibrated sweep delay mode, allowing smallest waveform sections to be expanded up to 1000 times. The HM 604's most outstanding feature is the automatic After -Delay Trigger mode to nsure extremely stable displays and jitter -free measurements of asynchronous signal sections and bursts or pulse trains, independent of amplitude fluctuations. An active TV -Sync -Separator further enhances trigger quality and in the alternate trigger mode, two signals of different frequencies can be compared. At only £575 plus VAT the HM 604 from HAMEG again sets a new price performance standard representing decades of successful design experience! another winning scope from Hameg.

All Homeg Oscilloscopes are suppled with 2 probes rooms loud and HAMEG yours wall amity on in sir unlentt 70-78 Collingdon Street, Luton, Bedfordshire LU1 1RX rot'0105ewhoCOINIpare Telephone (0582) 413174 Telex 825484 Fax (0582)456416 ENTER 32 ON REPLY CARD TIME AND FREQUENCY The Company is Registered to Def-Stan 05-2; (AQAP- 1 * Synchronisation of remote sites. RADIO CLOCKS * Time Stamping GMT/BST. CHRONOMETERS * Quartz master/slave systems. Accurate off -air standard (MSF Rugby). STANDARD FREQUENCY* Calibration and reference for timers, counters, RECEIVERS frequency meters. Generators, Readers with high speed tape search TIME CODE and control. Timecodes IRIG A, B, vela, EBU, INSTRUMENTATION NASA, XR3. Analogue, digital and self -setting analogue types (desk, wall or console mounting). DISPLAYS * Public time displays for airports, bus, railway 8 stations and factories. 7 5 A computer network monitoring and management WATCHDOG system for synchronisation and fault reporting of MI up to 64 independent computers. * Feasibility studies and consultancy. 1.1 CONSULTING AND * Small quantity manufacturing and test services. MANUFACTURE * System design. All the above can be supplied with a wide range of options and interfaces including Airborne, Military and Commercial versions. Customised systems available. European Electronic Systems Limited, Maldon, Essex CM9 GSW, UK. Telephone: 024 541 5911Telex: 995917 EULEC G Fax: 024 541 5785 ENTER 9 ON REPLY CARD

890 ELECTRONICS & WIRELESS WORLD Step-up switching regulator

An f.m. switching regulator producing 44V from seven NiCd cells at an efficiency of over 90% for currents of 1.5 to 60mA

N.J. CHAFFEY and T.A.PERKINS

any of the portable stimulation con- R f trollers produced by the MRC Neuro- logicalProsthesis Unitrequirea 1M supply of between 25 and 44 V. To save on the 12 gpA 01 number of cells in the battery. flywheel -type. Tri 13 8V2 step-up switching regulators have been used for most of our stimulation controllers ZTX 504 0204 Rti\,.0.324pA designed in the last two years. Do OR1 We found that commercial switching - 1N4448 142k5 regulator control i.cs were disappointing - 11DQ06 Volo particularly in stability, efficiency, quiescent Rp 1N4 current and the large number of outlying 448 IRFZ 12 components needed. For scarcely any more 3M3 components a much more predictable and fM9 1 "I'150p C2 =-=220,u efficient voltage converter may be based on 44V 25V standard op -amps or comparators. The f.m. Si switching regulator described here is de- signed V, I, to 10 V battery (seven NiCd cells, giving 8.5 V for most of the discharge curve) whilst Rs R7 maintaining an efficiency of over 90% for 1M8 100k loads from 1.5 to 60 mA. Useful efficiency 7V cutoff 1660)JA 180+'/6%1 is maintained down to only 400 µA 153pA C3 4700 load -a dynamic range of 150:1. which is due to the low quiescent current of 368 ILA for 62 05 25V 8.50 V input. Since very little has been 1M published on switchers for use below 5 W and as 80% seems generally accepted as Fig.1.Switching -regulator circuit diagram. "good- efficiency - usually quoted at full load with a load -current dynamic range of about 5 :1 - we thought our design might be useful to others. Output voltage can readily he ancel. E1. is given by Ei. = V,2T,-/2 AL N2. altered by changing the ratio of a potential El. = L 11,2/2 = V, I, T (1) divider. Best of all, the design is simple and By definition can be made compactly, most of the compo- nents being available in surface -mount ver- Where L is the inductance of the choke. IL is V, I, =V11100 sions. the peak current in it. 1, is its mean current The circuit shown in Figure 1 consists of averaged over the whole cycle of period T, four main parts: the parametric feedback and V, is the input supply voltage. whereriis percentage overall efficiency. V circuit which sets the output voltage: oscil- the output voltage. I the output current. lator: the flywheel voltage converter: and a 11, can be obtained from: and 1, the mean input current (including low -battery -voltage cut-off. that of the converter control circuit). At full 11, = V, T,/l. = 2 I, (2) loadinthis design, the control circuit TIIE FLYWHEEL CONVERTER current I, is quite insignificant (about 0.1% T, being the input pulse width. L is related toof I,,, - see Tables 1 and 2). I, may then be Taking the flywheel converter first, there are the number of turns N in the inductor taken as the same as I, and the overall three phases of operation. Initially the in- efficiency the same as the converter efficien- ductor is charged from the input supply: in L = A1, N2 (3) cy -rt.. the second phase itis discharged to the By using equations (1). (5) and (6) and output: and in the final phase it is essentially where AL is taken from manufacturer's data. crudely approximating rl = 100%. a rough disconnected. From equation (3). equation (2) may becalculation can now he carried out. Suppose Charging the inductor. In the first phase, rewritten V,= 8.5 V. Al. = 250 nil, N = 35. T, = 351.Ls when the mosfet Tr, is turned on, energy EL (keeping it simple). V = 44 V and I = 60 is stored in the choke. Presuming that the 11, = V, T,/(Ai. N2) 14) mA: then E1 = 144 µJ and T, turns out at current rises linearly with time (true for a 55p.s. Note designs with T, < I, are not constant inductance with no series resist- and hence feasible! For Fig. 2. the situation is T, =

ELECTRONICS & WIRELESS WORLD 891 Table 1: choke :14mm x 8mm N48 pot core) and switch (IRFZ12)

PARAMETER SOURCE/FORMULA THEORY SOURCE/FORMULA MEASURED

nominal A, /u, Data Book' 250nH/159 nominal AR Data Book' 115 u!) N turns 0.375 mm Cu wire 35

L zero bias inductance L AM' 306.25µH no adjuster -6% 284µH R, coil resistance R, AaN2 0.14 1! 0.2 1! I,,, mean coil current 329 mA E, energy per cycle V,272/(2ALNI 144 µ.I 166 u.I I, peak coil current 1/,T,/(ALN2) 0.97A -21:1, T, 1.17 A d.c.-biased inductance "V,T, I, 244µH

I magnetic path length Data' 20 ram A cross sectional area Data' 25 mm2 A, minimum cross section Data' 19 mm2

B mean flux density u, IL *V,T, (AN) 340 mTesla-V,T, (AN) 325 mTesla Fig. 2. Operation at 8.50 V,. 43.5 Vo, 727 ohm B, maximum flux density Data' 390 mTesla (A,k1) 436 mTesla 1,, saturation current -V ,TL,, 1 19 A load : 7l = 93%. (a) oscillator output at 5V/div; (b) choke charge current at 1 A/div; max. Ve, for IRFZ12 Data Sheet' 50 V (c) Tr2 drain/choke at 20 V/div: (d) Vo at 0.1 R2,,,,, for IRFZ12 Data' (ll 101c, 0.20hrn Typ(il 8.5 0.2 C,,,, output capacitance Data' in 8.5Ve. 240 pF 1/(47.-2f1) Co 309 pF V/div. VR ripple voltage pk-pk E,N.CIL(e.s.r.) 15 mV ? -50 esr 75 mV R, series res, Tr2 on R5, RdsonRita 0.5 ohm 0.11.! wiring! 0.61! R,05, 0.3 ohm 33.5µs, T, = 59.5µs. V = 43.5 V and = R,.. series res. Tr2 off R,, 93%. Table 1 summarizes key data for the Notes 1.2 and 3: see references. flywheel converter, along with the required Rough estimate based on: V,- 8.5V. V.44V.10 60mA. T, - 3511s. nominal At and II100%. then T, - 55 is -Conditions: V,8.5V. V.43.5V.1 60mA. T,- 33.5us. then- 93% and T, - 59.5us formulae. To simplify assembly of the pot -Based on: V,10V. Le,244µH and see Fig. 3 for 29µs:'1 92% core, the adjuster was omitted: a 6% induct- ance reduction can be expected for this. Table 2: oscillator, regulation and low -voltage cut-off

Saturation. The usual relationship between PARAMETER DATA USED & (EQUATION) VALUE the voltage across a coil and the rate of 7 time constant R,C. 142.5 kohm & 150 pF (Fig.1) 21.38 is change of magnetic flux linking the turns of V lower trip point Fig.1 & (15) 0.661V, V, = 8.5V 5.62 V 0.920V, V,= 8.5V - 7.82 V that coil may be written for our purpose V,, upper trip point Fig,.1 & (16) V, 0.071V, (bearing in mind the flux is initially zero) delay correction for V. , t2.5µs. T21.38irs. V,,, V, & (17) V.,' corrected V,,, V, 0.071V, 0.929V, time from V., to Vii V,0V0. V & (18) 0.3407 B = V1T,/(AN) (7) Tr, oscillator output low T21.38us & (0.3407 2.5µs) 9.8µs ---1111"PHS. 721.38µs. V,.Vi, & (17) 0.588V, where B is the flux density and A the effective time from V' to V,,, Yr.-V, V. Vr,- V, Vol & (18) 1.642-r cross-sectional area of the core. If the pulse T, oscillator output high 7.21.38115 & (1.6427 2.511S) 37.6 is T oscillation period T. + T, 47.4 u.s width Ti exceeds the time T, at which the flux expected mark: space ratio T,/T, 3.84:1 density reaches saturation both magnetic nwastil vd T Tr, drain disconnected. V, 8.5V 9.5,s hysteresis losses and current increase rapid- measured T, Tr, drain disconnected. V, 8.5V 37.7 s ly. Using the 'rough' example quoted above, measured T,, Tr2 drain disconnected. V, -- 8.5V 472 ,s a peak flux density estimate of 340 m Tesla is I,,, measured supply current Tr2 drain disconnected. V,8.5V 373 ir A 15 91 Ok obtained, which seems safe compared with I, static current Fig.1:14 16 lic the manufacturer's saturation flux density Ire free osc. dynam. current Tr, drain disconnected: V,8.5V. I,,, I. 282 irA lei dynamic current,10=60mA V. - 43.5V & V, = 8.5V : 40(47.2,59.5) 224µA value of 390 m Tesla (see again Table 1). This I, control circuit current 10 - 60mA. V, = 43.5V & V,- 8.5V: I, 315 RA last figure, however, is for a uniform toroidal V, set voltage - high Fig.l. V,0.6, Si open. h,t150 & (19) 44.1V core. For a pot core of non -uniform cross- V,, set voltage - low Fig l Vb. = 0.6.51 closed, N.= 150 & (19) 25.0V section, it may be more pertinent to substi- V. measured output voltage V= 44.1V, I = 0 - 60mA 8. V, -7.5 -10.0V 42.744.7V V. measured output voltage V,.,=25.0V.1.=0- 34mA & V, = 7.5 -10.0V 24.224.6V tute the minimum cross-sectionA,,,(if V,., low battery cut-off Fig.1 & (20) 7.0 V known) for A in equation (7). Where the ferrite data is not available, a more conserva- As free -running oscillator. n.b. timing independent of V, tive limit of 300 m Tesla is probably safe Icf K.L. Smith. 19854). With V, = 10 V, Fig.3 illustrates the start of saturation where the current changes much greater than 10% of the pulse is in B x N/A when T,.sc T, sc N2. (8) slope dramatically upwards after 29p.s. some saturation, the efficiency falls alarmingly! As and V, constant. shown in Table 1. equation (7), with T, also 10% before the end of the input pulse. Thus. if saturation is a problem, the flux Fortunately the reduction in efficiency from substituted for Ti, then yields a maximum Fig.3 of 436 m Tesla. density may be reduced for the same power 93% to 92% is acceptably small. However, if flux density for by lowering N and reducing the timing agreeing with the manufacturer's value to periods as N2. within 12%. This approach is limited by the speed of It should be noted that as the coil current the control circuitry. Conversely if no reduc- approaches the saturation current thetion in inductance is detected, N may he inductance is not constant. For IL just short increased to take advantage of the reduction of 1,0,. Table 1 shows the inductance 1.d,is in quiescent current possible with slower some 14% less than that without d.c. bias. Acontrol circuitry. Alternatively, a smaller pot NW. by-product of this inductance reduction is core may be used in this case. that the energy EL is correspondingly in- creased, equation(1) still applying if Ld, is substituted for L and 2 In, T,/T, for From equations (2). (4) and 15). it may be Discharge phase. When Tr, is turned off, the seen that to vary N while maintaining thechoke current continues to flow (i.e.it same power (hence holding I,,, and l con-flywheels), discharging the stored energy stant too), the timings T, and T, should boththrough the only pathway available - via the Fig.3. Operation at 10.0 V,. 44.1 Vo, 727 ohm be kept proportional to N2 and then equation diode D3 to the output capacitor C2 at the load:= 92% (a), (b), (c), (d) as for Fig.2. (7) may be rewritten output voltage V,,. In this phase of the cycle.

ELECTRONICS & WIRELESS WORLD 892 the step-up voltage V, is across the inductor Cp = 1/47r2f2L) (13) in such a direction as to reduce its current to zero in time Td Here. Table 1 shows that C constitutes be the overwhelming bulk of Cp. The energy Td = Vi TiNsu (91 needed to charge Cp with voltage V, is I

where = Cp Vsu2/2. (14) a

Vs = V + Vd - Vi (10) For Fig.2, Ecp is 0.2 which is negligible compared with the El, value of 166 p..1 but Vd being the forward bias voltage of the diode provides a warning of possible significant D. For Fig.4 a 0.1 ohm resistor was tempor- loss at higher operating frequencies. arily placed in series with Di and a pair of Fig.4. Choke charge and discharge cur- differential probes connected across it to THE OSCILLATOR rents(a) oscillator output/at 5 V'div; (b) show the discharge current. Superimposed choke charge current at 0.5 A div:(c) The relaxation oscillator in Fig.1is built choke discharge current at 0.5A div. on thisisthe charge current waveform derived from the voltage on the 0.1 ohm around one of the two comparators in a TLC 3702. This c-mos i.c. typically has quiescent resistor in series with Tr.,'s source, giving a The 13 term may be ignored in a rough good illustration of how closely equivalent current consumption of 110 per compara- estimate. When the load current 1 dis- tor and 2.5 is switching delay for 5 mV are the peaks of the charge and discharge charges C below V. Tr,isturned off, overdrive at its input. The push-pull outputs currents in the choke and how close to linear allowing a high pulse from the oscillator to are the slopes for these currents. Taking Vd which swing fully rail -to -rail make it ideal deliver energy El. to C after the end of that as 0.4 V for a Schottky diode, equations (9) for driving the mosfet Tr2. Ignoring for thepulse. In equilibrium, pulses are permitted and (10) indicate a Td value for Fig.2 of moment the switching delay, the capacitorjust often enough (f.m. control) to maintain C, should he charged and discharged via R, 8.2µs, some 7.7p.s being observed. V oscillating around V,. Fig.5 illustrates between a lower trip point V1, and an upperthe off-load condition where only the inter- trip point Vu, given by Ripple. It may he shown that the peak -to - nal load of the parametric feedback circuit peak capacitative ripple voltage V, in capaci- itself applies. For all but about 200 p.,s out of V1, = R, R,V,/(R, R2 + tance C may be approximated as + R,12:1) the 52 ms final phase of the cycle, V is such 115) that Tr, supplies only sufficient current V, EL/V C (111 through R, to hold C, just above VH, keeping and Tr., off as long as necessary. Wasted current by presuming that the entire energy E1, is is minimal. a powerful demonstration of the delivered to C in negligible time, and by Vu, = (R, R2 + Rd WW1 + R, R., intelligence of negative feedback. + R2 R, (16) equating energies before and after the choke In practice. Tr, does not turn off instantly discharge. At the low operating frequency as V,, falls below and the residual current here (< 20 kHz) the action of the capacitor's The voltage on C, may be obtained from slightly shortens the choke charge pulse T. effective series inductance le.s.1.1 may be The speed with which Tr, turns off is directly ignored. The total ripple VR may then be Vr, = Vr e-1/1. T = R, C, (17) related to the speed with which V falls estimated by adding in the contribution due between choke discharges. i.e.I,,. Thus it where Vr, is the voltage across R, at time t to a presumed peak discharge current 11, may be reasonable to expect pulse width to and V,is the initial voltage across Ri. through the capacitor's effective series re- decrease linearly with decreasing l(see Conversely, the time taken to reach voltage sistance (e.s.r.) Fig.6for measurements). Although this Vrt is given by: pulse width modulation causes the incon- VR = ELNC + (e.s.r.). (121 venience of making pulse -width prediction t = T In (V,.Aird (181 more involved, it does have the considerable Unfortunately it may not be easy to predict advantage of extending the dynamic range of the e.s.r. value prior to using the compo- Using equation (17). Table 2 shows howthe regulator. Rapid optimization of timing the trip points are affected by the switching nent. As shown in Table 1. an e.s.r. estimate may be carried out by setting V,toits delay and hence, using equation (18). how of 50 mil accounts for most of the 75 mV p -p minimum value, monitoring V at high ripple seen in Fig.2. The value of C may the high and low output times may besetting off load, then applying the maximum seem unnecessarily large, but is required in obtained for the free running oscillator.1 and varying R,tillthe drop in V is our case to cope with the heavily pulsatile Agreement between the theoretical andacceptable. A check should be made at load of a stimulation controller as well as to measured periods is within 0.3 maximum V, that the off load V is still reduce e.s.r. The mark:space ratio for the free -sufficiently restrained and that the core is running oscillator was chosen to be about 4 : not then excessively saturated with max- 1, virtually as high as is practicable with this Final phase. The inductor has acrossit imum I (see again Fig.3 ). Table 2 shows the parallel capacitance Cp made up of the circuit. The intention was to maximize the output capacitance of the mosfet. the El, available per cycle (hence making regula- reverse capitance of D,,, the self capacitance tion easier) and also to minimize the of the coil. etc.Itis. therefore, a parallel required for a given power level so as to tuned circuit, one end of which is per- reduce resistive ( i.e. 12R) losses. manently connected to the input supply V. At the end of the discharge phase, the choke REGULATION has no current but still has voltage V, across The parametric feedback circuit of Fig.1 it,kickingitinto a damped oscillation limits V by turning on Tr', hence forcing centred on V. Here, as > V,. the first the oscillator and Tr,off. whenever V downstroke of this ringingis caught at exceeds V, which is given by: ground by the integral diode in Tr, (restor- ing a tiny amount of charge to the input V, = (R, + Rb)(V, + + R,, I3/11,, supply). Thereafter, ringing proceeds with a 119) Fig.5. Operation of parametric feedback at peak -to -peak swing of about 2V,. gradually 8.50 V,, off load: T, = 52 ms. (a) oscillator decaying away. The frequencyf of this where V, is the zener voltage and V, is the output at 5 V/div; (b) Ct/lit at 5 V/div. N.B. ringing (537.5 kHz for Fig.2) provides the base bias voltage of Tr,. h11 its current gaintrip point at 5.6 V; (c) Tr2 drain/choke at 20 value of Cp by and its collector current when turned on. V/div.

ELECTRONICS & WIRELESS WORLD 893 - 96 the oscillator being just held off by Tr,. In this circumstance, the internal load current 1, drawn from V by the parametric feedback -95 circuit is T

fqn.y tr tes f = + 13 = + Rh) + V/R,. (28) 30 tn c t 21s - 94 VI The consequent input current In neces- sary to maintain I,,, is: - 93

= V1,/VoiC (29)

2 92 50 60 which for the above conditions comes to 265 L.;,r2(m;.,

Fig.6. Pulse width T, and voltage converter efficiency II, for 8.5 V, to 44 Vu conversion - The remainder of the control circuitry in versus load current. these circumstances consumes a static cur- rent L of 91 µA (see Table 2). The total percentage PRn of the input energy EL lostquiescent current In can then be estimated in RSrin is from Measured Theoretical Imaximum difference Piton = 200 R,n .173L. (22) l = I, + 10 130) t. 2%)

Eso. During the choke discharge, Tr2 does notwhich here amounts to 356p.A. This theore- contribute to the series resistance. so a lowertical value is just 121JA short of the measured value Rsidr applies. Thus from equations (9).quiescent current. The total input current I, (10) and (22) and presuming PR0 is small,for any external load current I can now be the percentage PRo. of EL lost in FLA- is, to a confidently predicted by first approximation r. 10frr. 101.4JA 1mA I, = V (I + 1;)Nr,1c + I, (31) LOAD CURRENT : --- 200 R,01; T; Vi/I3L (V + Vd VA. Fig.7. Total efficiency Ti for 8..5 V, to 44 Vo (23)and hence the overall efficiency TI by equa- conversion -versus load current. tion (6). measured range of V for both the 44 V andThe percentage Pd lost in the flywheel diode The resulting efficiency curve for I from the 25 V settings. While regulation at the D may be written as 20p..A to 60 mA is shown in Fig.7, together higher voltage is merely adequate for our with seven measured points which agree purposes, that at the lower voltage is re- Pd = 100 Vd/V (241with the theoretical curve to within 1.2%. latively much better because of the lower It would appear that other losses are power required. Fig.6 shows a line for pulse Assuming all these losses are small theynegligibly small. width T, versus l for V1 = 8.5 V and the 44 V may be combined by the Binomial Theorem setting, this line being linearly interpolatedto give a simple estimate of converter effi- DESIGN PROCEDURES from measurements at the four points V, = ciency Tle The design procedure may be summarized as 7.5 V and 10.0 V with I = 0 and 60 mA. p firstly finding an EL Auch that Tc> Tcf Agreement between the line and the points = 100 -P- Ron -R..it Pd (25)(equations (1),(5) and (6) and Table 2). measured at V, = 8.5 V is within 0.2 !Ls. Secondly equations (7) and (8) are used so If the coilis tightly and evenly layer -that saturation is avoided. Note the full -load LOW VOLTAGE CUT-OUT wound and the enamelled copper wire dia-T, in this design is about 10% less than that meter and N are chosen so as to exactly fill The fourth section of the regulator is almost of the free oscillator's Th. Once the timing is the bobbin, then the coil resistance R can be self explanatory. When V, is below Ku,. the known, efficiency may be predicted by equa- obtained from comparator output is high and, being wire- tions (22) to (31). Ored via a diode to the same input to the Having obtained the appropriate values R,= AK N2 (26) oscillator as for the parametric feedback, for the parametric feedback components forces the oscillator off. V,, is given by from the intended V and equation (19). the where AR is a constant given by the manufac-regulator's performance may then be tested turer. In practice, although equation (26) is V, = 2.5 (R5 + Ro)/R6. (20) in practice. Finally. it should be noted that a useful guide, not all the above conditionsthis circuit is tolerant of considerable com- apply and R is consequently rather higher As well as protecting a flat battery from ponent variation. Hence a wide range of (see Table 1). R,n may be written as large currents, this circuit also ensures that. input and output voltage and current is at power on. Tro is held off until V, is high possible. R,,, = R, + Rd,n + Rte + R55. (27) enough to ensure proper operation of the regulator. Consequently. the circuit may be References where R.isthe wiring and connection 1.Siemens Ferrites Data Book 1982/83, pp. switched on at the 44 V setting with max- resistance which is not negligible unless 153.154. imum load with equanimity (power on sett-great care is taken with the circuit layout. In 2. Ibid. p.38. ling time is then 140 ms). a production circuit, R, would be omitted.3. International Rectifier Data Sheet No PD9440. As PR,f is much smaller than PR,,, a rough4. Smith, K.L.. 'Switched -Mode Power Supply'. LOSS ANALYSIS estimate for R,ffis sufficient (see againElectronics & Wireless World. October 1985. pp.61-64. Presuming that the choke currentIin- Table 1). Using equations (22) to (25) and the creases linearly on charge, the energy ER,, T, values indicated by the solid line in Fig.6.Acknowledgement dissipated in the total resistance R,,,n in lc may now be obtained for 44 V output withOur thanks to P.E.K. Donaldson for his en- series with the inductance is given by 8.5 V input as shown by the dotted line in couragement. T, that figure. For instance, the off load estimate is 94.5% and that at full load 93.8%. N.J.Chaffey, Ph.D. and T.A.Perkins. M.Sc. Elton = R" dt =1L' Rsn T,/3. (21) In Fig.1, the current values indicated byare both at the Medical Research Council's Hence from equations (1) and (21) the arrows apply for V, = 8.5 V. V = 44 V and forNeurological Prosthess Unit.

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ELECTRONICS & WIRELESS WORLD 2496 L.f. navigation revival Britain's first new long -wave radio network for decades is being set up by a Swindon company, Datatrak. It forms one half of a system for tracking vehicles on the move.

For afleetoperator, knowing each RICHARD LAMBLEY °lice bLildings. Besides, hardware for an LE vehicle's exactlocation provides a system is much cheaper. worthwhile boost to efficiency. At the Since last November the system has been very east it can help improve scheduling. r innini. in the London area, though Data- But with valuable cargoes such as cash or t-ak is now expanding it to cover the entire bullion, or tobacco or spirits, the informa- country. Eventually the long -wave network tion could reassure you that a load was safely will comprise 18 sitesin a grid layout: onitway; oritmight warn you that station:covering the south-east areat hijackers were at work. Heathrow Airport to the west of London. Datatrak's system is centred on a small Pomner Marshes, Selscy Bill. Kineton (near electronic module carried by each vehicle. Stratford-upon-Avon) and St Neots. Power Using positional information obtained by level in each case is about 1.5kW delivered to monitoring Datatrak's I.f. signals, this unit the antenna, though it is difficult at such determines its exact location and reports it frequer cies to achieve a radiation efficiency automatically by radioto a monitoring better tan about 20 per cent. point. Any v.h.f.or u.h.f.radio linkis These stations, operating inthe135- suitable (incluchng the new Band Ill trunked 145k1h-, region, are organized in groups of systems), though the company offers its own eight: each transmits in turn, sending a pair dedicated data network: this can handle of frequencies within its time -slot. A com- some 2000 vehicles on a single radio chan- plete sequence of transmissions. the primary nel. For dealing with the flow of position -iavigation cycle, occupies 1.68 seconds. reports Datatrak offers a bureau service. Time -dots for a further eight stations are operated by Securicor (which is one of its nterleived between the first set. parent companies - the other is the George On the vehicle, the receiver module looks Wimpey group, whose interests in offshore for the six strongest signals and then com- surveying were the source of much of the putesis position by measuring the trans- radionavigation expertise behind the sys- mission path delays. With three signals, it tem). At the bureau, information is collated can geL a rough fix: with six, the intersecting and sent out to individual customers via lines box itin more closely and the fix modems and telephone lines. becomes highly reliable. A status signal from For land vehicles, an 1.1. radiopositioning the urit indicates the degree of confidence. system offers important advantages over the An output, in the form of map grid coordin- satellite systems increasingly being used in ates. is available from the unit on a V.24 the air and at sea. To obtain a fix from the CPS satellites, it is necessary to have a path to three of them - and that is difficult to One of Datatrak's If antennas: the com- arrange in city streets overshadowed by tall plete If chain will consist of 18 stations.

'I VrT11411111re V. WIDVI VCC WADI ri 897 The vehicle -mounted module is fully auto- matic. A 68008 processor computes the vehicle's position by reference to the If signals.

serial port for users who wish to take it no further. A special feature of the Datatrak system is that the pairs of I.f. signals are frequency - modulated slightly: the complex signal which results can yield a much greater positional accuracy than was possible with earlier systems. A fix can be to within 50 or even 10 metres. In additional, the receiver -VOMOMMIIMA can initialize itself from cold anywhere - every fix is an absolute one.

11111111111111111 For relaying data back from the vehicle, MIIMININO MM. Datatrak has two frequencies in the 170MHz 11111111111011 EMI a.. 1111MR911111111111111111111116. region and a network of 25 base stations. 111111111111111111111011111 ARMORS, NOMOMMOWOM ARM MU mainly at IBA sites. Expansion outside the NIIIMINOMMOR Anummilm south-east will entail a move to u.h.f. chan- NMEIMMOMMIUM a MMUUMUUM IIMMOROMMOMO MRMUMMURIBUt nels around 400MHz. Each vehicle has its OMMOMMOMMY 41111111 .ft0111111 MUMEMMUOMAIL, own pre-programmed time -slot. synchro- MOMMOMM lilaMA. ARM MMUMMUMUMUMUUM nized by the 1.1 navigation signal, during MOWNIMMOM AWE. fEM UMMUUMMUMUUMMUI which it sends a 30ms burst of data contain- mor 1111111.11111111111M111111111111M11111 ing its position, status. direction and speed. 11111U ABM I 14111111111=111111111111111111111111111111r OM mumilMI Direction and speed (accuracy is to within ME Mr MEWNEEL,. 1111111111I five miles per hour) are obtained by compar- NNW11111011111r ing the two most recent fixes. Some 150-160 NM, 'N1111111111111111111111111111111 base stations will be needed to cover the IWIL 111111111111111I1E1111111111111111' whole country, each linked by private lines ma to a data centre and interconnected to allow MIIII. 11111M11111111M1111111RIST roaming. In England there will be four data 11111111116. AMIE MINN 11111111P"'14111111= 111/111'I 41111MIIIIIIIIIIIIIIIIIII centres, in London. Loughborough, Swin- ottamiimrQ,_ib... AIIIIIMMIIIMIIIIIIMImm....dammuu,rrommirik/ ...... masal.._ don and Leeds. mom i l IMMIIIMIllik How often your vehicle transmits a fix IIIIIIIIIIIIII quill`MIEU".:" ' ' -Nil 'p d11111111111011111111 depends to some extent on what you are 1111111111111111 Ilr' - ,, ,,-,' - 'W IIIIIMIIIMEMBh. allik : 1 lE1111111111111VAMMER= ` willing to pay: for a bullion van, a fix every 1111WIRMINIMM1111b...,...millIMMIIM/ -it AINNIIMINIIIIIIIII few seconds might be needed, since any EINORIIIIIIIIIIIIIMMIIIMIIIIIIIIMIIIIP: .illho.1011111MMIIIIIIIIIIIMIII deviation from its planned route could mean "T11IIIIM1111111111111=111111111111,:s 11111111111111111111111111111111M111111V trouble. With other types of vehicle, a fix 'ffiiiMMEEMEMMIENF: 'Iii11.1111'."iliMMI1 every minute would be enough. Datatrak's full service includes the use of an emergency alarm: when the driver hits the button, the system reports it immediately and the vehi- cle continues to transmit its position every four seconds until the emergency is over. One early customer for the system is Cellnet. which will use the system for com- piling field -strength maps for its cellular radiotelephone network. Measuring vehicles will be able to log signal measurements direct to tape or disc together with their exact location, cutting out a lot of tedious manual data entry. Another user could be London Regional Transport, which has been investigating the system's potential for help- ing to reschedule buses caught in traffic jams. The vehicle -mounted unit for Datatrak costs just over £1000: and the running cost. including the bureau service, is about £85 per month. Further details from Datatrak Ltd. Hargreaves Road. Croundwell Indust- rial Estate. Swindon. Wiltshire SN2 5AZ: tel. 0793-722549.

Left: top -of -the -range displayisa high - resolution colour screen on which each vehicle's position is re -plotted every few moments. Advanced software will make it possible for a warning to be given auto- matically if a van deviates from its planned route. Less ambitious users can opt for a simple telex -style printer instead.

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ELECTRONICS & WIRELESS WORLD ti99 Dependentsourcetheorem Finding equivalent generators in a network which has no independent sources.

HARRY E. STOCKMAN

many of today's networks contain de- pendent sources only, in fact the majority of the semiconductor - equivalent networks belong to this group. While the Thevenin-Norton theorem readily yields equivalent generators when the net- work contains atleast one independent source, it fails when the network is free of R1N RIN such sources. Still, we wish to be able to (bl construct equivalent generators in all cases; methods to obtain such generators are dis- cussed in the following. Although the net- work is put in the handy configuration of a calculate quantities such as RIN and v/e. this port be replaced by a generator generator, in reality it remains passive, with obtaining impedance in series with the open -port its "source" controlled by a current or a voltage or in parallel with the closed - (4) voltage outside the port. The dependent RINI= (A+ kR2R23 port current, respective voltage and v/e=R31R,-k1/(A+ kR21 (51 sources we are concerned with presently are current appearing with the initial of the basic kind kels) and kils). A most direct way of obtaining RIN from the values they have in the given network. A simple example of a network which constructed generator in Fig.1(b) is to apply and the generator impedance being the contains a dependent source only is shown the Compensation Theorem, change ex into port looking -in impedance when all by the one to the right of the port in Fig. I (a), a resistance and then just sum the two sources are removed. and this network might well represent a resistances. The driving network may be represented transistor. One method to construct an There exists a short-cut to the determina- by a series -form or parallel -form generator, equivalent generator is that of the Source tion of input and output impedance, contri- and may consist merely of the source to such Transformation Theorem, in which we col- buted by the Port Immittance Theorem, a generator, asisthe case inFig.1(a). lapse the given network in steps from rightassuming, however, that the transfer func- Additional network theorems are listed in to left, thus ultimately obtaining a series - tion is known, and in this case it is given by the reference. form generator and a parallel -form gener- (5). The theorem states that the denomina- ator like the ones shown in Fig.1 (b) and (c). tor of (51, set to zero, contains both the input Reference Such equivalent generators, however, are and the output impedances. It states that the StockmanI I.E. "Transient Analysis Aided by never independent of the driving network on input impedance is the negative of RI, thus Network Theorems". Sercolab. 1984. Box 767. E. Dennis. MA 02641, USA. the other side of the port, and we must -R1 = RUN and that the negative of R: is the consult the equations for the entire system output impedance, thus -R3 = Rout. when we wish to switch variables, for exam- Whenever the proper transfer function is ple to make the source a function of e instead known, this theorem saves time. To find RIN of i. Since the driving voltage and current we must add R1 to RUN'. We find for Rorr: are the same before and after the trans- +k)124R (6) formation, we may express the equivalent -R3= RorT= (RI source as a function of either. If the transfer function is not known. we Another method is contributed by the may stilluse the indicated short-cut by Dependent Source Equivalent -Generator introducing -RUN in the given network as a Theorem, which makes the segregated replacement for e and R1 and, in a subse- "dead" network alive by prescribing that the quent operation, -Rorr as a replacement for source retains the initial value it has in the R3. An analysis of the network yields the given network. This means that we deter- formulas for RUN and R017. This is in accord- mine the value of i in the given total ance with the Theorem, which is a collateral network, and then treat ki as an independent to the Tellegen theorem, and the proof rests Dr Stockman was born in Sweden. He source when determining the open -port with the Tellegen theorem. As we replace e received his M.S. degree from the Royal voltage and the closed -port current. Ex- and R1 by -RUN. we cut off the signal supply to Institute of Technology in 1938. continuing pressing the equivalent sources ex and ix as the network under investigation, but at the as Assistant Professor of Radio Engineering current sources, we find, with R23= li.,+ R3 same time we introduce a negative resist- at the Institute. During the Finnish -Russian and 12112,-F R 1 R3+ R,R3=A, ance, and indeed one that equals the positive war. he served as a radio adviser and was resistance it "sees". Accordingly, we create awarded the Liberty Cross by Field Marshal e' = k 12, i/R.,3 III instability and thus the currents and vol- Mannerheim. In 1941, Dr Stockman went to ix = k R, i/A (2) tages we need to analyze the network. the United States on a Ford Fellowship and Rx = A/R, 3 (3) The Dependent Source Equivalent Gener- gained a S.D. from Harvard. He eventually We note that the relationship ex/ix = Rx, ator Theorem has the following formulation: became Head of the USAF Communications typical for the Thevenin-Norton theorem, A linear network with dependent Laboratory and later formed his own com- also holds for this theorem. sources only. provided with an accessi- pany, Sercolab. in the electronics education We may use either equivalent generator to ble port for a driving generator. may at field.

900 ELECTRONICS & WIRELESS WORLD FIELD ELECTRIC LTD. 01-953 6009. Fax: 01-207 6375 3 SHENLEY ROAD, BOREHAMWOOD, HERTS WD6 1AA.

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902 ELECTRONICS & WIRELESS WORLD FSATELLITESYSTEMS

Geostationary latitudes between 45'N and 63.4°N. loops? As a means of providing sat - corn services the Loopus system A novel idea to solve the problemhas been designed to meet two of congestion in the geostation-main requirements. One is to ary orbitisthe geostationarygive global coverage for the loop. It doesn't use the conven-maritime mobile satellite service tional Clarke orbit at all hut has- that is. coverage of areas on three satellites moving in threeEarth where ground stations can elliptical orbits as shown in Fig.see the appropriate satellite at a 1(a). The orbital planes are angu-minimum elevation of 5°. The larly spaced by 120° from eachother requirement is to provide other. The orbital elements arespot beam coverage for the fixed chosen so that the three satel-satellite service (FSS). Here the lites follow each other in thecomsat beams would give five same track in a co-ordinate sys-spots on the Earth's surface, four (0) tem rotating with the Earth. aswith a diameter of about 3000km shown in Fig. 1(bl. each and one with a diameter of Fig.1. Loopus system using three satellites to form two geostation- As a result of this arrangementabout 1000km. All the spot -beam ary loops: (a) three elliptical orbits as seen by a fixed observer; (b) there are two small geostation-footprints provided by one such the satellites' track as seen from within a frame of co-ordinates ary loops. 180° apart, positioned Loopus would be in the northern rotating with the Earth. A second, independent 'upside down' above particular points on thehemisphere, butit would be system could be used as well, to give good coverage in the Earth's surface. Observers on thepossible to have another, similar. southern hemisphere. Earth would 'see' a satellite inindependent system serving the each loop, moving round itinsouthern hemisphere as well. made necessary by the fact that spin -stabilized space -craft eight hours. There would be a One problem that had to be in each geostationary loop the shaped like a solid three -pointed satellite in each loop at all times:considered in devising this un-communication task has to be star (pictured overleaf), with so- as one satellite leaves a loop, theusual techniqueisthat thehanded on, every eight hours. lar arrays fixed on the six edges of next satellite in the sequence ofcoverage areas change as each from one satellite to the next. the points of the star. Like all three enters it. They pass in andsatellite moves round its geosta- All these difficulties have been others in the series, Oscar 13 is out of the intersection pointstionary loop. This is because oflooked into by the originators of basically an educational aid, seen in Fig. 1(b). the varying distance and angle of the Loopus scheme and solu- allowing amateur radio com- As mentioned briefly in ourthe spacecraft relative to a given tions have been proposed. It re- munication over much greater May issue report on an IEE dis-point on the Earth. mains to be seen whether these distances than would normally cussion on the geostationary The coverage areas are defined inevitable complexities are justi- be possible in the v.h.f. and u.h.f. orbit (p.489), this proposal com-as those areas in which the powerfied by the benefits offered by the bands used. es from Germany and has beenflux density on Earth, during the system. Apart from the relieving There are four transponders in put to the European Space Agen-entire passage of the spacecraft pressure on the limited resource the spacecraft. One, with cy. It is the joint work of threefrom the intersection to the topof the geostationary orbit, the 435.5MHz uplink and 145.9MHz West German organizations: theof the loop and hack again, cor- Loopus system would also pro- downlink, has a bandwidth of aerospace company MBB/ERNO,responds to at least the p.f.d. vide two other benefits. It would 150kHz. The second has a the communications engineer-generated at the top of the loop at give better coverage of polar re- 1269.45MHz uplink and a ing firm ANT Nachrichtentech-the 3dB contour. A study hasgions than the g.s.o. does and 436.85MHz downlink, with a nik, and the country's centralshown that by taking the p.f.d. as would allow single -hop connec- bandwidth of 250kHz. The third aerospace research and develop- a basisfor determining the tions between Earth stations on transponder operates on a ment body DFVLR. They haveperiphery of the coverage area. opposite sides of the world pro- 144.45MHz uplink and a called the system Loopus (geo-the changes in path attenuationvided these were in the same 435.95MHz downlink, while the stationary loops in orbit occu-are more or less compensated by hemisphere. fourth uses a 435.6MHz uplink pied by unstationary satellites). changes in the satellite antenna and a 2400.7MHz downlink. A For each of the elliptical orbitsgain which affect the edges of the digital communications experi- in Fig. 1(a). the orbital elementscoverage area. So the size of ment isincluded in the last- (defined in the November 1987these areas remains practically New amateur mentioned transponder. The issue.p.1158) are as follows.constant and only minor de- radio satellite antennas are a mixture of v.h.f. Apogee is 39 117km. perigee isformations occur as a result of rod,u.h.f.dipole and helical 1 238km and inclination is 63.4°. changes in the satellite's angleOne of the three spacecraft laun- types. The semi -major axis of therelative to the Earth. ched simultaneously on the first Because most of the world's ellipseisa distance of Another problem arising fromflight of the new Ariane-4 rocket radio amateurs live in the north- 26 585.7km while the eccentric-the varying position of each com-was a further communications ern hemisphere between the lati- ity is 0.7132 and the argument ofsat as it travels round the geosta-satellitefor radio amateurs. tudes 30° and 60°. satellites in perigee is 90°. In this path eachtionary loop is that it affects theAmsat IIIC. It becomes the latest the third Amsat generation have satellite has an orbital period ofparameters of the radio link be-member of the well known Oscar been put in orbits designed to be 11 hours. 57 minutes. 47tween Earth and space. As aseries (orbiting satellitescar- the most useful for these re- seconds (there's German preci-result, various compensationrying amateur radio) and will be gions. Amsat IIIC/Oscar 13. as sion for you!). One version of thistechniques have to he introducedknown as Oscar 13. the third member of this third system would produce geosta-- especially, for example, for the The new Oscar was built by generation, carries on this policy tionary loops above Europe atchange in received carrier fre-Amsat-Germany under the inter- and has an elliptical orbit which 10°E and above the Pacific Ocean quency caused by the Dopplernational programme run by the gives much better coverage of at 170'W. Both loops would be ateffect. Further complications areAmsat organization. It is a 150kg these northern regions than

ELECTRONICS & WIRELESS WORLD 903 [SATELLITESYSTEMS

elled themselves into their re- New satcoms spective finalorbits as stated operator elsewhere. A further success for the The first private company to ownAriane -3 space vehicle came on and operate an international sat -22 July. with the launch of the corns service outside of the offi- IndiansatellitelnsatIC (see cial Intelsat. Eutelsat and Inter -January issue. page 57) and the sputnik organizations is the USlast of the five European Com- firm Pan American Satellite, amunications Satellites. When subsidiary of Alpha Lyracom ofcommissioned. ECS-5 will be re- Greenwich. Connecticut. It ownsnamed Eutelsat 1-F5 and will Fig.2. The Amsat IIIC a single spacecraft, the PAS -1provide a range of telecom- or Oscar 13 amateur comsat, which was launched bymunications services to Europe radio communica- the first Ariane-4 rocket alongincluding telephony, business tionssatellitelaun- with Amsat IIIC (see report else-services. and radio and television ched in June this year. where) and Meteosat P2 (Januarydistribution. ECS-5 will replace issue p.58). From its geostation- Eutelsat 1 -Fl, which will then be would be possible from, say a al years. but now seems more ary slot of 45°W, PAS -1 will beavailable to carry new services in geostationary one. This elliptical likely to go ahead as a definite able to relay international trafficaddition to acting as an in -orbit orbit has an apogee of 36 000km. project. After two years of nego- between Europe and USA andspare. ECS-5 is one of the three a perigee of 1500km. an inclina- tiations, a basis for international between Latin America and theEutelsat craft built by British tion of 57° and an orbital period co-operation on design, develop- USA. as well as covering the Aerospace. of about 11 hours. Immediately ment, manufacture and opera- Caribbean area. after launch from Kourou, tion has been agreed between the Although providing an inter- French Guiana, the satellite was four main partners: USA, national service, Pan American placed in a transfer orbit with an Europe. Canada and Japan. Satellite will not be competing Intelsat VII inclination of 10° and was subse- NASA will be responsible for the directly with the main world quently moved into thefinal American work and ESA. repre- organizations in public telecom- transponders elliptical orbit by the reaction - senting eight member states. for munications. The company will propulsion motor mentioned the European contribution. be concerned principally withThe new Intelsat kit series of above. The USA will provide the over- private business satellite com-comsats announced last year The Oscar series started in allspace station framework: munications and will not link(December 1987 issue. p.1232) December 1961 with a spacecraft operating sub -systems including into public telephone networks.will each carry 36 transponders. carrying just a simple 145MHz life support and 75 kilowatts of In the UK, uplinks to PAS -1 willFor C band there will be sixteen beacon transmitter. Later satel- power: laboratory and living be provided by British Telecom.72MHz and ten 36MHz trans- litesintroduced transponders quarters: and an unmanned free - However, the comsat is also like- ponders. For Ku band com- and became progressively more flying platform that willbe ly to be assisting with nationalmunications the spacecraft will sophisticated in spite of cost con- placed in polar orbit for Earth services for Latin Americanprovide six 72MHz and four straints.Britain's contribution observation. countries which might other- 112MHz transponders. sofarto the international Canada will provide a mobile wise be unable to afford them. These high -power satellites amateur programme is the Uni- servicing system to be used in In engineering design PAS -1 iswill allow the use of smaller versity of Surrey's UoSat-1. cal- conjunction with the assembly. fairly conventional, being a mod-Earth station antennas and will led Oscar 9 and launched in maintenance and servicing ofified version of a standard RCA replace the present Intelsat V -A October 1981. and UoSat-2. cal- parts of the space station. Japan Astro-Electronics Series 3000comsats at the end of their life in led Oscar 11 and launched in will contribute an 'experiment satellite. It has 24 transpondersthe Pacific Ocean region. They March 1984. The new Oscar 13 is module', which is a permanently and operates in the C and Kuwill have the ability to switch C an improved version of Oscar 10. attached pressurized laboratory. bands, normally working to band capacity between the east- which was built by Amsat- ESA, through the associated Col- small and inexpensive Earth ter-ern and western hemispheres Germany and launched in June umbus programme, will provide minal antennas. and will give simultaneous Ku Pis:1 a pressurized laboratory module The three satellites launched band coverage of three regions in permanently attached to the on the first Ariane-4 flight on 15the Pacific area which can be manned base: an unmanned Jung had a combined mass ofaltered while the spacecraft are Space station free -flying polar platform to 3513kg. As already reported inin orbit. Later on, The first two work in conjunction with the USthe July issue, the Ariane-4 de-spacecraft are expected to be agreed polar platform: and a 'man -sign. whichis much morelaunched in mid -1992 or early tended free flyer' to be serviced at powerful than the preceding 1993. Elaborate radio communications the manned base. Ariane-3, allows various com- The penultimate Intelsat V -A between space and ground will Some time ago there was a binations of engines and boos-spacecraft, F-13, was successful- be needed when the Western sharp riftbetween the Amer- ters to be used to suit differently launched on an Ariane-2 rock- world's permanently -manned icans, who seemed to want to use loads.Inthis case the 44LPet in May this year and is sta- space station eventually goes the space station partly for milit-version was employed, with twotioned at 53°W., The last in this into operation, possibly in the ary purposes, and the Euro-liquid and two solid propellantseries, F-15, is due to go up in 1990s. This will be a very large peans, who were firmly opposed boosters. The third stage of thisJanuary 1989 (the F-14 having artificialsatellite, orbiting the tothis.Inrecent statements rocket was first injected into abeen launched out of sequence). Earth at a low altitude of 450km NASA describes the project as a transfer orbit with an apogee of and an inclination of 28°. "civil" space station while ESA 36 359km, a perigee of 221km As a proposal it has been dis- goes further and adds the words and an inclination of 10°. Subse-Satellite Systems is written by cussed and argued over for sever- "for peaceful purposes". quently the three satellites prop- Tom lvall.

904 ELECTRONICS & WIRELESS WORLD Piezoelectric coaxial cable Novel packaging should make piezo-rubber more usable Pl:'l'l;R Jot INsoN

Most applications which require a Rf piezoelectric transducer, for exam- 400 - ple underwater hydrophones or pressure sensors, use a ceramic material 300- called PZT. (lead zirconium titanate). When E subjected to a mechanical strain, this pro- 2C0- Output duces a voltage of the order of 311V/Pa - a Piezoelectric usefully high value that requires nothing transducer 100- more sophisticated than a charge amplifier -Vcc to buffer the extremely high source impe- 0 - Signal earth I dance of this capacitive transducer to an 0 1 2 analogue signal -conditioning circuit. Fig. 1 . Fig.1. Lead-zirconium-titanate is easy to TIME (us) PZT has many advantages: it is chemically use as a pressure transducer.It has a ( al inert, it has a reasonably high sensitivity and relatively high voltage output and needs it can he used over a very wide range of only a charge amplifier like this one to pressures without serious non -linearity. produce a signal suitable fo- feeding to There are no problems in making this analogue signal -conditioning circuits. Re- 1Ic- sitor Rf would typically be around 20M!! ceramic in almost any shape or thickness at 800- relatively low cost. given an LM308. The biggest drawback of the material is its E00- mechanical fragility: like all ceramics. PZT is Nemo E rubber I'VD1, l'ZT- 400 brittle and must not be subjected to impact tonne or excessive flexure.In underwater hyd- Density 1.8 1.78 7.5 700- Speed of Si 0.9-1.8 lonisec rophone design. where maximum sensitivity Dielectric o- is obtained by using a very long transducer constant :to 8-11.5 1175 at Ikllo 1 1 assembly, mechanical flexibility is essential. Sensitivity ig;,1 150 $:t-2822.$ niV.in/N 0 1 2 TIME (us) so a large number of PZT elements are linked electrically within a long PVC tube. This (b) have similar sensitivities: however, since the tube may be filled with an insulating oil to Fig2. Piezo-rubber (a) and PZT (b) tran- voltage generated by a piezoelectric trans- obtain the required overall specific gravity sient responses. Amplitudes are not direct- ducer is given by: and minimize the support needed for the ly comparable due to different thicknesses hydrophone in the water. v=gtP of transducer. Such a hydrophone incorporates a great many lengths of wire and soldered joints where P is the pressure applied, g is sensitiv- ity and t is thickness of the transducer in the which willbe subjected to considerable PVC sheath Braided Piezoelectric direction of the pressure, electrical output of whiplash if used at sea -a labour-intensive (con be square screen rubber composite a piezo-rubber device can be made greater in cross section) ( PR -302 and potentially unreliable technique. than that of a PVDF transducer by increasing The technical ceramics division of NTK. I j the thickness: PVDF is not easy to manufac- one of the world's largest spark plug manu- facturers. supplies PZT transducers to ture except in thin sheets. Underwater hydrophones are typically Centre conductor oceanographic hydrophone constructors. In used in sonar systems to monitor the return a paper presented to the 7th Symposium on Fig.3. Piezoelectric coaxial cable is similar Ultrasonic Electronics in Kyoto (piezoelec- pulse of acoustic energy reflected from thein appearance to ordinary 50i! coaxial seabed or other submerged object. This is a tric transducers are widely used at ultra- caole. sharp -edged pulse when transmitted. but sound frequencies), four NTK researchers will normally show "clutter" after reflection presented a paper describing a new compo- site material consisting of fine particles of which gives the experienced sonar operator some indication of the type of surface from piezoelectric ceramic material embedded in ()versed Protective Piezoelectric which it was reflected. ex trus on coax a synthetic rubber. Chlorobren. With a PZT transducer, which has a very By attaching flexible electrodes made this characteristic +10.zoO,e0P6 from carbon -loaded Chlorobren, the resear- low damping factor. p,itmo oo'160'e,. shapeis masked by the ringing of the .attPE.....?',-;°, chers were able to show that this composite transducer elementitself.Fig 2(h). The has excellent piezoelectric properties, but is

rubber matrix material of the new composite (10Af:oa.6:0Ny.--A completely flexible.Further, the rubber ;a0,?°°40.7qoo4'.2t.9 imparts a much larger damping factor to the :°`e 0 0.O% used has good acoustic coupling properties hydrophone. greatly reducing ringing. Fig. for signals in sea water, because the speed of Sealant 2(a). PVDF. a ferroelectric material. also Fig.4. Piezoelectric coaxial cable used as a sound in both media is similar. exhibits ringing oscillations when used to This table gives some of the relevant vehicle sensor requires a protective extru- detect a single ultrasonic pulse. properties of piezoelectric rubber compared sion, but it has a longer life than electrical contact strips. Compared withelectro- with PZT and PVDF (polyvinylidine dif- PIEZOELECTRIC CABLE luoride. a synthetic rubber with inherent magnetic sensors, a piezoelectric cable piezoelectric properties). Flexible materials are not easy to makesensor detects smaller vehicles and is Note that both the new composite and PVDF contact with, especially unsolderable sub- easier to install.

ELECTRONICS & WIRELESS WORLD 905 stances like piezo-rubber. In existing ap- plications of this still new material, the active element is sandwiched between layers of conductive rubber of similar elasticity: contactis then made to the conductive rubber by means of beryllium -copper leaf springs. Clearly, this is an inconvenient method of connection, so NTK investigated more ver- satile techniques which did not require the mechanical precision of earlier methods such as the one described. The result of this effort was a coaxial cable, similar in appear- ance to normal 5011 coaxial cable, but with the insulating layer between the screen and centre conductor made of a piezoelectric rubber composite designated PR -302. Fig.3. This cable can be made in continuous WIRF1 %ORLI) & WIREI IRS NORLD & WIRELESS WCIRLD WIRELESS VIORL lengths of up to 20m and is compatible with soldering or with standard coaxial plugs, making it much easier to use. Electrical properties of this cable are as detailed in the table above.

APPLICATIONS OF PIEZOELECTRIC COAXIAL CABLE This form of the material has only been in production for a short time, so there are, for instance, no hydrophone applications so far. However, the cable has been used in Japan as a non -contact self -screening pickup for an electric guitar, and research is being carried out into its incorporation into a blood- pressure/pulse-rate monitor. As a vehicle sensor for traffic lights, the cable was found to perform well because of itsresilience and high sensitivity. Such sensors receive severe battering so the cable was protected by embedding itin tough synthetic rubber extrusion, shown in Fig.4. Compared with vehicle sensors relying on electrical contact strips, this method has a longer life and is insensitive to the ingress of rainwater. Electromagnetic sensing systems - the most popular alternative - are reliable but have problems detecting cyclists and moped riders, and require a large area of the road surface to be removed for installation. The piezoelectric cable sensor needs only a nar- row transverse trench to be excavated by pneumatic tool. Piezoelectric coaxial cable is still, to some extent, an interesting solution looking for a three year subsc lectronics & Wireless World costs only £53. problem. It is here, in an easily -used form. delivered free to the address of your choice; that's a massive saving of and available off -the -shelf to the develop- almost 25% - ti - equivalent of eight issues free! ment engineer. It remains to be seen what the ingenuity of R&D engineers will make of it. Further reading NM mi EN im Ns NENM MI Hisao Banno. Kohji Ogura. Hideo Sobue & Kanji Ohya: Piezoelectric and Acoustic Properties of Piezoelectric Flexible Composites. Japan Journal SUBSCRIPTION ORDER FORM El Please send me Electronics & Wireless World for threeyears at the special price of £53.00' ofApplied Physics. Vol.26 11986). 'Includes posrage and Pa,,'"17 RY Ting. Ferroelectrics Vol.67 p.1-13. 1986. I enclose a cheque/PO to the value of made payable to Reed Business Publishing Limited

H. Ohigashi. K. Koga. M. Suzuki et al. Ferroelec- Please debit my credit account tricsVol.60 p.263.1984. Access Barclaycard/Visa American Express Diners Club Expiry date

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906 ELECTRONICS & WIRELESS WORLD INTERNATIONAL BROADCASTING CONVENTION BRIGHTON UNITED KINGDOM 23-27 SEPTEMBERjai 1988

INTERNATIONAL BROADCASTING CONVENTION

The 1988 IBC Technical programme will cover all aspects of broadcast engineering with particular emphasis on emerging technology including satellite and cable distribution, enhanced and high definition television systems, as well as multi -channel sound systems and associated information systems.

The IBC EXHIBITION complementing the technical sessions will have the latest professional broadcasting equipment on display and demonstration by leading world manufacturers.

The SOCIAL PROGRAMME during the Convention will include a Reception and a special Ladies Programme FURTHER INFORMATION can be obtained by of talks and demonstrations and visits to places of returning the reply coupon below. interest.

The IBC Secretariat, Tte Institution of Electrical Engineers, Savoy Place, London, United Kingdom WC2R OBL. Telex: 261176 Telephone: 01-240 1871

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Towards ISDN- 2 Skyphone takes Adrian Morant continues his introduction to the air to integrated services digital networks. Europe'sfirstpublicsatellite ISDN basic access consists of two 64kbitis B supplementary service facilities as well as sig- telephone call from an aircraft channels for user information together with a nalling procedures for the basic call handling, has been carried out by Racal and 16khit/sI)channel. While the former are e.g. call establishment and release for B channel British Telecom International. circuit -switched. thelatterisa packet - connections. The test link -up took place he- orientated channel whose main purpose is to 1Vere the D channel used only for signalling it tween Racal's company Jet - exchange signalling between terminal equip- would frequently be idle. Consequently it can stream aircraft and BTI's satellite ments and the local exchange. also he used for the transmission of packets of Earth stationatGoonhilly in Under normal circumstances. when used for data. The transmission of data by packet switch- Cornwall. voice, once the call has been set up the D ing makes for far more efficient use of re- The in-flight tests are paving channel is free until the call is to he terminated. sources. Instead of a circuit being allocated and the way for a trial commercial For this reason. while the basic access consists held exclusively during a message transfer it can service for passengers travelling of 2B+ D. at the next level in the hierarchy be time-shared between many. on British Airways Boeing 747 (primary rate access or PRA) there is only one D Access to a packet network is via a packet transatlantic aircraftlater this channel with either 30 or 23 B channels. This assembler/disassembler (PAD): this is reached year. This will he followed by a depends. respectively. on whether the system is at present via the public switched telephone regular manually -connected operating to the CCITT or the American "Bell" network. but in due course it will he via the telephone service and subse- standard: the former uses a 2Mbit/s transmis- ISDN. Initially it will use a B channel - being quently by aioilcommercial sion channel while the other uses 1.544Mbit/s. analogous to a PSTN voice channel - but direct -dial Skyphone service From this it can be seen readily that a D eventually the]) channel will be employed. This available to all airlines by mid - channelis shared between a number of B will mean a more efficient use of resources. I989. channels. This is a "common channel," and the After all, the D channel is transparent to the [sing the Inmarsat satellite signalling it carries is therefore common chan- packets being sent and is not concerned with network. Skyphone willoffer nel signalling. It forms an essential part of the their content. It will transfer them as required passengers adirect -dialtele- network and provides control and supervisory irrespective of whether they are signalling phone service to 185 countries information regarding the routing and setting - information or actual user data. worldwide. as well as facilities for up of a callas well as status information. In packet switching the message is transmit- the transmission of aircraft oper- Consequently, when attempting to initiate an ted as a series of discrete blocks or packets. In ational telephone and data ISDN call. the calling terminal will use the addition to the data itself, each packet must traffic. signalling channel to make its request and will contain address information to indicateits The equipment is designed to use the CCITT Common Channel Signalling source and destination. It must also include a operate to Inmarsat specifica- System No.7 - often just referred to as C7. Not sequence number to enable the received mes- tions in the 1.5-1.6Gliz I. hand. only must this request cite the number of the sage to be re -assembled correctly. Thisis The low noise amplifier is housed party being called, it must include a variety of analogous to a series of postcards which each in a small package to permit other information. For example. if the proposed contain part of an entire message. By marking mounting on the inside of the call is just voice from one digital telephone to them with a serial (or sequence) number it is aircraft skin close to the receiv- another. only one 64khit/s B channel would be possible to ensure that they are in order and so ing antenna.Ithas sufficient needed. If. on the other hand, the required call determine whether any have been lost in the gain to allow inexpensive and was between two combined voice and data post. Should this occur, the recipient would king cable runs tothe radio terminals. two B channels would be required request the sender to repeat the lost informa- frequency/intermediate frequen- spanning the entire end -to -end path. Different tion. cy unit mounted in the aircraft devices require different network resources: the Whereas in circuit switching a path through equipment racks. without im- calling party must therefore initiate negotia- the network is "transparent" to the user once a pairing receiver noisefigure. tions to ensure that it will obtain the necessary call has been set up. in packet switching the I..n.a.noisefigure.including channel capacity. network must supervise the whole operation. losses from pre-l.n.a. filters.is To send a message from a character - lower than 2.5d13 even a1 aircraft orientated terminal. such as a teletype or a OSI Protocols skin I emperatures C. dumb v.d.u.. it is necessary to dial in to a PAD The D channel signalling protocol consists of and then log -on with one's Network User Layers 1 to 3 in the ISO Open Systems Intercon- Identification (NUD and password. The PAD nection (OSI) Reference Model. In Layer 1. the maintains control and integrity of individual Research into electrical and physical characterstics of the S messages and integrates them with others interface are defined. In addition. a multiple which are also within the system. Having personal access mechanism is specified which allows the obtained access to the network. the user speci- communication D channel to he used by a number of terminals. fies a destination address for the message and Layer 2 of the I) channel protocol (LAP I)) can then inputs the message. The PAD takes the The Government has announced he considered to he an adaption of the LAP B message and breaks itinto a series of data the eighth 'Link' programme. procedure defined in CCITT recommendation packets. To each of these packets it adds framing which aims to stimulate the pre - X.25 to the specific needs of ISDN basic access. information and then the whole packetis competitive research towards a Owing to the bus structure of the S interface. launched into the network. Both header and new, higher capacity, third gen LAP I) has to support multiple simultaneous data portion of the packet have a checkword erationpersonalcommunica- Layer 2 connections. Additionally. LAP D en- attached, to enable the integrity of each packet tions system. Its contribution to ables the higher layers to broadcast a message to land thus of the entire message) to he verified the three-year Personal Com- all terminals connected to the S bus. on receipt. Should an error he detected the munications Programme is Layer 3 defines procedures for controlling the receiving end will request re -transmission. £6.35 million£3.35l from the DTI and £3M from SERC.

908 ELECTRONICS & WIRELESS WORLD -411LECOMMSTOPICS

Companies which have indi- cated that they would like to he involved in this programme in- clude AerialFacilities. Auto- phon, British Aerospace. BT Re- search Laboratories. GEC. Mar- coni, Philips. Plessey Research, Racal. STC and Thorn EMI. In- terested academic institutions include the following universi- ties: Aston. Bangor. Bradford. Bristol. City. I leriot-Watt. Leeds. Liverpool. Southampton, Sur- rey, Swansea and York. Lord Young. Trade and Indus- try Secretary, speaking in the House of Lords, said: "The need for the programme is prompted by the convergence of telecom- munications and radio technolo- gies. which is generating a new industry of personal com- munications. The number of gent payphones throughout the subscribers isincreasing. with Fibre Network, for which SIC preliminary documentation for Grand Canyon NationalPark. greater demand for accessibility was the prime contractor, and rural telecommunications pro- both indoors and outdoors - SIC is also supplying equipment These payphones connect to ajects in several developing coun- variety of transmission lines and whether stationary or mobile - for part of British Telecom's Lon- tries and of telecommunication carriers. development master plansin and internationally. don Docklands project. GPT payphones generate coin "There is therefore a need to STC claims to have been the others. including some regional extend the range of services first company to appreciate the accounting reports and they dia- projects. This groundwork will gnose malfunctions and attempt available and to integrate private strategic possibilities of distri- enable the countries to submit mobile. cellular and satellitebuting intelligence in the net- to clear them. 1Vith the heap of a telecommunication projects for mobile systems. Much basic work. dot-matrix display and voice financing. Some of the countries chip, the telephones also com- work needs to he done to achieve Flexible Access Systems will concerned are Burma, Gambia. this. It will he a key technological extend to local communications municate intwo languages. Tanzania. Somalia. Egypt. Nep- development for the 1990s." the benefits of the major mod-which willhelp some of the al. Malta. the Yemen Arab Re- ernization programme that Brit-thousands of international tour- public, and People's Democratic ish Telecom has been undertak- ists who visit the park each year. Republic of Yemen. ing in the trunk network. SIC "We are currently investigat- The Centre relies entirely on Flexible Access and its partner Northern Tele- ing ways to extend even morevoluntary contributions from com have established a 200 -services to communication both the private and public sec- Systems strong team to work on the points such as the Grand Can- tors in the developing and in the developments and products re- yon", said Peter Brown, manag- industrialized parts of the world SIC has been appointed one of quired. This team is deployed in ing director of GPT Telecomswhich stand to benefit from the the suppliers for the nationwide Products. "We can foresee theCentre's activities. To date, extension of British Telecom's the UK and North America. SIC and NT are also jointly time when we will be providing pledges amounting to about Sw. Flexible Access Systems (FAS). direct international dialling." Fr. 5 million (very little in view of for completion by the middle of working on the extension of optical fibres to small businesses the huge task) are 60% in cash 1991. SIC expectstoreceive and residential customers to pro- and 40% in kind for the current orders in excess of .ti I1)0 million. Third World year 1988. broadly distributed as FAS is based on the use of vide high quality telephony ser- vices, and the future possibility follows: 45% from industry. 45% optical fibres rather than copper Telecoms from administrations and the cable connections to business of television -based services. Another joint programme on rest from development finance customers. This will allow large By the first anniversary of the synchronous multiplexers and start of itsfield activities, the agencies. Several development numbers of private circuits to he finance institutions. as well as provided. and the evolution to switches will allow circuits of any Centre for Telecommunkations bandwidth to he carried efficient- developing countries them- wide bandwidth services such as Development ICTD). established ly ar, pond the whi,le network. selves. have so far responded video conferencing in the future. in 1985 by the ITU Administra- favourably. .\t the customer's end, a multi- tive Council in Geneva. had re- Twelve missions have been plexer connects the various cir- ceived some 40 requestsfor Payphones up assistance from developingcarried out so far and six more cuits on to the fibre. These mul- Ito Bolivia. Chile. China. Iran. tiplexers are controlled by net- the Canyon countries. work management software As the Centre employ:. only a Mozambique. Nigeria) are sche- duled during 1988. It is expected which enables the mixture of Visitors to the Grand Canyon can small core staff at its headquar- that these missions will lead to connections to he varied to ser- now dialhonie from remote ters. the major part of its work in additional requests for projects vice customers' changing needs areas of the park following an the field has so far been carried and specific assistance. and to provide connection to any agreement between US West Inc. out by experts and consultants other location required. in Arizona and the British com- whose services were obtained by The first Flexible Access Sys- pany GPI Telecoms Products. a combination of cash contribu- tems have been successfully de- Under the agreement. GPT has tions and support in kind. Teleconuns Topics is compiled ployed inthe City of London installed the first phase of intelli- CTD's work isin preparing hy.ldrian Morant.

ELECTRONICS & WIRELESS WORLD 909 Keyboard design Finer details of keyboard and keypad design are often overlooked by design engineers.

JEFF WRIGHT

There are hundreds of keyboard applica- effect is thus produced. This matrix is said to tions, not only in computers, but also have two -key roll over because if any three intypewriters, telephones, remote keys in the corners of the an imaginary controllers, washing machines, microwave square or rectangle are pressed then the key ovens etc. In many of these applications a in the fourth corner will appear closed as single -chip microcomputer, or controller, well la ghost key) and it is impossible to tell reads the keys and acts on the data entered so which three keys are actually pressed. There- a good understanding of keyboard -to -micro- fore the maximum number of keys that can computer software and hardware interface be pressed without confusion is two. techniques is essential for anyone involved Although this matrix is defined as having with keyboard design. two -key roll-over it would be more accurate MCU input port There are two main types of microcom- to say that it had a minimum of two -key Fig.1. Using one controller input for each puter -based keyboards. In the first type,roll-over as often many more keys can be key results in fast key -press reading and found for example in telephone and washing pressed before a ghost key is produced. For very simple software, but this does not machine controllers, keyboard reading is example, all keys on one row can be pressed make efficient use of controller lines. only a part of the microcomputer's function. at the same time and still be successfully Alternatively more complex systems, such as detected. It can therefore be advantageous computers and typewriters, often have a when designing a keyboard of this type to dedicated microcomputer controlling only make the matrix as rectangular as possible Syr/// the keyboard. These applications might with the maximum number of output scan 4 4/ /// seem quite distinct but the software and lines and also to arrange the layout so that ,, //// hardware techniques for any size of keyboard the keys which are most commonly pressed /4 / / are similar. together are on the same row. 1-',/1 A drawback of making the matrix rec- KEYBOARD TYPES //// tangular is that more i/o lines are required i /// There are several different keyboard con- for the same number of keys, but for many figurations. each with its advantages and applications the gains obtained make the ///y/I disadvantages. The simplest type of extra lines worthwhile. Tie 2 // 3 Another enhancement which can be made controller -based keyboard has one key Colmns f I I 1 which is assigned to each line of an input to the basic matrix is to give important keys. on/o port port. Fig.1. Keys can be read very quickly such as 'shift' on a computer keyboard, their using this method, and the software needed own input line. This then gives the two -key z-3 V V V is trivial, but it can only be used where there roll-over minimum and additional special Rows on input port are many spare inputlines.Direct key keys. readingisthereforerestrictedto small Software for this matrix is actually the Fig.2. Arranging keys in a matrix make keypad applications. most complex since to ensure correct opera- more efficient use of controller ports - Much more common isthe matrix tion, ghost keys have to be detected. Also, i/o only 8 lines are needed to read 16 keys. keyboard where the keys are arranged in switching is needed to scan the matrix to This produces two -key roll-over since rows and columns. This method makes avoid contention caused by a scan pulse of pressing more than two keys at once can much more efficient use of the microcompu- one logic level being connected via pressed result in an erroneous reading e.g. press ter's input/output lines, but it requires more keys to another pin outputting the opposite 1,2,3 and 4 appears as a ghost key. complex software for scanning the matrix. logic level. This latter point also means that Scanning is normally accomplished by pro- pull-up resistors are required on both sides ducing an output pulse on one column at a of the matrix as shown to avoid floating time and reading in all the rows to determine inputs (these pull-up resistors also act as 4 whether a key in that column has been current limiters). / pressed. For a given number of i/o lines. the When a ghost key is detected the keyboard I number of keys in the matrix is maximized is locked to prevent the false key from being /// by arranged it as a square: for example an processed, but the designer then has an 8 x 8 matrix reads 64 keys whereas a 4 x 12 option as to when to allow processing to / matrix reads only 48. begin again. One option is to start proces- /// Roll-over of a keyboard is defined as the sing keys once the ghost key has been number of keys which can be pressed at any released but this can lead to key strokes / / one time and still he individually recognized: being missed -a problem for the fast typist y)e" who may frequently have several keys press- ifallkeys can be pressed at once and Columns recognized the keyboard is said to have n -key ed together momentarily. The safest option on output port roll-over. This is the most desirable solution is to delay processing until all keys are but is more expensive than simpler matrices released - a warning of the delay could be for reasons explained later. given to the user if desired. V V V Figure 2 shows a basic 4x4 resistive This basic matrix is used extensively in Rows on input port matrix. In the case of a resistive matrix each low-cost computer keyboards, terminals and Fig.3. Adding diodes to the matrix stops key has a contact resistance of the order of many keypad type data -entry systems where keys interfering with each other, produc- 500 when pressed and a potential divider multiple -key presses are uncommon. Try ing n -key roll-over.

910 ELECTRONICS & WIRELESS WORLD your PC keyboard for quality: some don't even have ghost detection so that by pressing \se. // / a certain three keys you get four characters / Inputto i - // comparator on the screen! I / // //-LI N -KEY ROLL OVER - /// -I I - In higher quality computer keyboards and in T1-1 Columns / // / applications where alarge number of output ;; / /// Campertor outputli- multiple -key entries are required, an n -key roll-over matrix is used. There are two / // se ey pressed popular methods of achieving an n -key // .(>, ;Key released matrix hut both are more expensive to / -r manufacture than the hasic matrix type. The first and most common method is to add diodes to the hasic matrix. Fig.3. These ...... _1 diodes prevent any one key from interfering with another. thus producing n -key rollover. Voltage drop across the diodes is an impor- -L. tant hardware constraint when designing a matrix of this type since it can cause viola- tion of the controller port input thresholds. Excessive voltage drop can normally he avoided by choosing the correct value of Rows on inputport pull-up (current -limiting) resistor hut in the use of diodes. low voltage applications it can be more of a Fig.4. Capacitive keys and comparators prcduce n -key roll-over without problem. The second main type of n -key roll-over matrix has capacitive keys Fig.4. This con- Up figuration gives n -key roll-over without the cost of the diodes but with the additional Key state cost of comparators. Each key forms the Down plates of a capacitor and when the key is Debounce time pressed the plates move closer, increasing 11 the capacitance and allowing a short low - Second scan voltage pulse to reach the comparator input. Keyboard scanned here -key press detected -key press confirmed Impedance of the other scan lines and the lot Validkey press number of keys pressed also affects the level of this pulse. Pressing a ghost key produces High A three capacitors in series, which reduces the Port pin effective capacitance. thus degrading the pulse which would appear as the fourth key Low 1.6 signal. Debounco time Mien a key is pressed the comparator restores the incoming differentiated signal First scan here Second scan to a true logic level, so producing an output - such o noise pulse could be - false key press interpreted as a key press. rejected pulse which is detected by the controller. Since this pulse is normally shorter than the lb)Noise rejection scan pulse, care has to be taken in the in software not to miss any keys by reading too Fig.5. Contact bounce problems are commonly solved by reading a key's state twice late. Also, the comparator reference must be quick succession and comparing the readings. set up carefully so that the low -amplitude signal can he detected reliably, and the biasing circuit's impedance should be large EATURES IMPORTANT TO KEYBOARD DESIGNERS so that the time constant for the key press is long enough to produce an acceptable pulse length for detection. With both these n -key matrices the soft- Bid.rectional i .o lines are suitable for both two -key and n -key roll-over type keyboardsand ware is simpler than in the previous two -key available in numbers sufficient for any application from 4 - 4 matrix to a 120 key or larger roll-over case, since the scan lines can designs. Selectable pull-up down resistors on some devices are an added bonus. Timers can be used to determine a fixed polling rate or, in the case of a computer keyboard. remain as outputs all the time and ghost -key used to provide timing for the auto -repeat featire. Timers can also be used for the data detection is not required. They also avoid the transmission. requirement for pull-up resistors on the High current ports are a prime requirements for many control applications. On computer output scan lines -a minor cost saving. keyboards they can be used to directly drive leds which are often required to indicate the state of certain keys such as the lock for capital letters. Two bits can also be usedfor serial KEY BOUNCE line driving. Low power consumpticn modes and wake up features are important for portable In all keyboard types there is another vitally applications such as remote control. telephones and portable computers. important criteria - key bounce. Keyboards Serial Interfaces can be used for the serial Link between keyboard and computer or to can often he installed in very noisy environ- incorporate a magnetic card reader or mouse. Large ram holds matrix images for debouncing and forms buffers to hold characters to be ments and the scanning of a large keyboard - with long p.c.h. tracks can produce its own sent when required. On board eerom could be used to provide userprogrammable function keys on a computer noise and cross -talk problems. For these keyboard independent o' the actual computer. Only an additional program key on the reasons p.c.h. layout and software dehounc- keyboard would be required. ing must be handled carefully. One common method of dehouncing is to

till ELECTRONICS & WIRELESS WORLD read a column, store it. and then read the

column again. after the anticipated bounce Keyboard Old keyNew key Action time. Fig.5. When the column is read for the type state state taken second time itis compared with the first Simple X On Send key code result and if there are any differences then auto repeat those keys are considered to be inthe X Off Do nothing unpresssed state. A genuine key press will he Off Off Do nothing detected on subsequent scans. Non Off On Send key code The problem with this method when auto repeat applied to large keyboardsisthat the On X Do nothing accumulated debounce times from each Off Off Do nothing column check can produce an unacceptably Off On slow scan rate. A simple way around this Complex Send key code auto repeat problem is to scan the entire matrix in one On On Auto repeat go. storing it in ram. After the debounce time the matrix is scanned again with each On Off Send break code column being compared to its stored image as before. This can use a lot of ram depend- Fig.6. Software in controller -based keyboards can produce three different types of ing on the size of the matrix and so a operation. compromise between scan rate and ram usage can be obtained by debouncing the matrix in sections. Up to now it has been assumed that the keyboard will process any key that is found to be pressed, hut on some keyboards a key is only processed when it has changed state so that no repetition takes place. Alternatively some computer keyboard protocols send a key break code when the key is released. Both of these situations complicate the debounce and key -handling software since an image of the entire matrix has to be maintained in ram so that the present state of the keys can be compared with that obtained on the previous scan. Figure 6 keyboard shows the actions taken by a computer matrix keyboard depending on the type of operation and the states of the keys. With complex keyboards a good method of debouncing is to keep a new and an old image of the keyboard in memory (called. say. NEWBUF and oiniii,r). Then in the scan routine the entire keyboard is read into NEWItIT and after a desired debouncing time the matrix is scanned for a second time. On Fig.7. A dedicated controller as opposed to a microprocessor simplifies keyboard design the second scan, as each column it is read since it has i and compared with the first scan result. It o lines that can be connected directly to the keys. Some controllers also have internal pull-up or pull -down resistors and internal logic that produces an interrupt any of the keys have changed state they are when a change of i o line state is detected. considered to have bounced and the old value of that key is extracted from ouniiT and inserted into NIAtlit'F. In this way only key mode when a key is pressed. thus eliminat- Mass produced computer keyboards need states which are valid for the two scans are ing the need for continuous polling. to be made as cheaply as possible. It could be accepted. Later in the program NFA1111T and Quite often there are not enough i/o lines argued that a computer keyboard with its ounitiF are compared. the valid key changes on the controller chosen to handle all the own intelligence is not justifiable, but de- are processed, and °miff is updated ready for control functions plus a keyboard. but there signing a keyboard with its own processor the next scan (details later). are ways round this problem by sharing or brings several advantages. expanding input/output pins. In Fig.8(a). for In systems with a separate keyboard a CHOOSING A CONTROLLER example the MC6805 forming a tv controller serial link between the processors improves In most control -type applications the choice does not have enough i/o lines to drive both reliability and saves on cable cost and bulk. A of microcontroller will depend largely on the the display and keyboard. and cost preventsseparate processor also allows data to be other functions that the device has to per- the use of an external display driver. The input independent of the main processor -a form, with the keyboard being a secondary solution to this problem is to multiplex the buffer in the internal ram -of the keyboard consideration. Despite this there are a num- two functions on the one i/o port. Three port controller can store key inputs to be trans- ber of features available on some devices linesA1, disable the display while the mitted to the main processor when it is free. which can be a great help to the designer. keyboard is scanned and the high -value On power -up an independent keyboard pro- Shown inFig.7isthe MC68HC04.13. resistors are to prevent shorts between cessor can perform checks on the keyboard which has two features which make it parti- segments caused by pressed keys. to detect stuck keys. etc.. while the main cularly suited to control applications incor- Figure 8(h) shows a situation where a processor checks out the rest of the system. porating small keyboards. The first of these low-cost controller is being used to scan a In the past it was common to find micro- is the option of internal pull -down devices full computer keyboard. Again, this part computers with external memory in compu- on all or some of the port pins, and the does not have sufficient i/o lines to scan the ter keyboards but today the single -chip second is a wired -Or interrupt option. This keyboard and so an analogue multiplexer is microcomputer is almost universal in new software controlled feature allows the device used to compensate. Note the dual use of the designs due to its inherent cost advantages to be brought out of its low -power WAIT and multiplexer address lines as inputs for spe- in control applications. A list of features sroi, modes or to be interrupted from run cial keys that need n -key operation. found on various controllers which are of

912 ELECTRONICS & WIRELESS WORLD Fig.9. Most of the design work for a PC - /2' Main matrix compatible keyboard using a controller is done by the software writer. use to the keyboard designer is shown in the pedal key panel: some of them apply only to computer type keyboards. others to any type.

DESIGN EXAMPLE I I I I I I I I I I Porto 0 Po-tA 0 7 Port This example forms the basis of a PC - MC 6805U3 with internalpull-ups compatible keyboard and has been chosen because it demonstrates most of the princi- INT Porte 0 Vss Vcc R EXTAL XTAL NUM TIM ples described previously. Figure 9 shows I I I the keyboard implemented using a low-cost Clock DataSpore MC6805U3 with mask -selectable pull-up re- Status sistors on all ports. It has 100 keys arranged Serial l nk indicators' as an 8x 12 two -key roll-over matrix plus Ceramic resonator four special keys, it also incorporates status leds and a serial link to send characters to the main computer. Software shown in List 1 is 6805 assembly language for scanning an 5V 8 x 8 section of the matrix: this allows the ' principles to be shown clearly while keeping SHFTp t5V 16 3 the software toa minimum. Note that Vd d 9 PC0 wherever possible the number of row inputs SHF IL TIM 10 15 MC to the controller should he kept to a multiple 12 Reset A LTp 1 4 0 S 1 of four as this simplifies the scan software 11 1 Doto 5 considerably. Pal ALT} 2 The ram required for these routines con- PC3 4 sists of two buffers used to hold images of the INT

matrix. Each has the same number of bytes MC 613HCO4P3 as there are columns in the matrix plus one with internal pull -downs PA status register and two temporary storage CA 11 1,1 bytes. At the start of the program would be an NUM PE3 initialization routine that sets up the ports PB2 Clock Bx12 2 -key PBO 4! -1\AA rollover matrix

EXTAL PA0 PB7 XTAL TIT MDS OV P84 V55 Fg.8. In the tv controller of (a) below, reading key presses is only part of the niicrocontroller's job whereas in the com- B puter keyboard of (b), the controller's only job is to read keys and turn the decoded J data into serial form.

Contrast 1PC,PC - V- a Vd 8.220 Brightness ST B. 1:12 PAC B- MC 144111 .------Colour r-FT 1E7-C. 0 -tc-o a3 %A, Vss Volume tiw S N Din CL 04 8x2k2 NAN V'tv 4x 47k BO e7 A4 A0 Ay Al VDR CL A2 Ac. atom Dotoout A/V B1 NEG Vcc MC 6805 T 2 0 UAA 2001 Uhf Reset B2 Loop filter and III NUM bond driver B3 Vss OUT5ND INT EXTAL XTAL A Co C1 C2FIN P OS 1 L Vc 2 Vcct 84 12V SCL SDA Vd d Mute' I M C M2814 prop store Ili CSOVC [Si M Vss pre amp selection for remo Tuner contra! Standard T 1111 LI ri 30V 12V Standby

ELECTRONICS & WIRELESS WORLD 913 and buffers, etc. This section is not shown here as the software is trivial and controller List 1. Example software in 6805 assembly language for scanning 88 rows of the dependent. The main loop of the program PC -compatible keyboard. consists of a scanning subroutine, sc %mut!), a ghost detect subroutine, cmcfiosT, anda routine, SENDKEY, that decodes the key changes and sends the data to the computer. updating the 01.1)111,F in the process. This last routine is only shown in skeleton form as it is unimportant for this example. ORG RAMBSE SCANA LDA TEMPI Switch selected column to NEWBUF RMB Routine scANKB1) scans the matrix twice COLS New and Old matrix image STA DDRA output so producing a low buffers scan pulse. using i/o switching and also detects and ENDBUF EQU 1 byte in each for each BSR READCOL Now read in that column column LSL TEMPI Move scan pulse to next corrects bounce. It begins by setting a flag to OLDBUF RMB COLS column FLAG identify which scan pass is being executed. RMB 1 Status register BCC SCANA If not all done yet then TEMP RMB I 2 temporary storage CLRA continue else return all Port A data register is cleared as isTEMPI registers lines to input. whichisused as an image for Port A TEMPI RMB 1 STA DORA BRCLR LOOPFLG. FLAG 112 scans complete then data -direction register bum (this is necessary ORG ROMBSE OKRTN return since certain commands cannot be executed RESET EQU ' BCLR LOOPFLG. FLAG Clear loop flag. JSR INIT Set up ports initialise BSR DEBNCE Wad for desired debounce on the port data -direction registers). buffer and status reg etc BRA SCAN time then scan keyboard a BRO of TEMPI is set and the byte is written MAINLOOP EQU ' second time JSR SCANKBD Go scan keyboard twice OKRTN RTS to ma forcing port A bit° to output a low: store in ram JSR CHKGHOST column 0 of the keyboard matrix is then read Check image in ram for READCOL EQU Ghost keys LDA PORTD Read selected column in vai Port D in the subroutine RE NI Oil.. Value BRSET GHOST. FLAG if detected then wait for BRCLR LOOPFLG FLAG If second scan then go TEMPI is then shifted left and if it has not MAINLOOP keys to be released VERIFY check for bounce other JSR SENDKEY Go and process any valid STA NEWBUF. X wise store column overflowed then itis written to Ifllk\ thus key changes COLINC INCX Increment the buffer BRA MAINLOOP shifting the scan pulse to the next bit of Port pointer NXTCMP LOX TEMP RTS A. this continues until TEMPI overflows. After INX Check if we have CPX ENDBUF compared every column VERIFY FOR NEWBUF.X Compare with first scan the scan the loop flag is tested to see if it is BLO STOREX to every otherif not, BEQ COLINC valueif no differences thefirst or second scan that has been update pointer and do (bounce) then return. loop again STA TEMP completed. If it is the second then the scan LDA TEMPI COMA otherwise manipulate routine is exited: otherwise the loop flag is INCA If all keys are released AND NEWBUF.X scan results with old value BNE GHOSTEX then TEMPI should STA NEWBUF.X so that only key changes toggled, the required debounce delay ex- contain FF LDA OLDBUF.X that were valid for both ecuted and the keyboard scanned for a ALLOFF BCLR GHOST.FLAG So clear ghost flag. scans are included the GHOSTEX RTS others are returned to second time. their old value AND During the first scan the subroutine READ SENDKEY EQU TEMP TSTCNG JSR TSTCHNG Look for differences ORA NEWBUF.X Equation for NEWBUF is Col, simply reads the column in via Port D. BNE SENDKY between NEWBUF STA NEWBUF.X stores it in NEWIIIIF and increments the buffer OLDBUF. if none found BRA COLINC (SCANI EOR SCAN2) return with Z 1 OLDBUF ISCANIEOR pointer. In the second scan however RE.wcoi RTS No key changes to SCAN2) SCAN I is a little more complex as it checks for key process so return CHKGHOST EQU Look for Ghost keys in SENDKY JSR TSTKEY Process each key change LDX NEWBUF matrix image stored in bounce. As each column is read an exclusive- in this column and update NEWBUF OLDBUF with its new state. LDA . SFF Initialise pointer and Or operation is performed with it and the BRA TSTCNG Look for next column with temporary register result from the first scan to seeif any a change in it STA TEMPI changes indicating possible bounce have STORE% STX TEMP Store latest pointer value Modified scan routine for an N -Key rollover matrix LDA X Get associated byte from occured. If there are changes then the result SCANKBD EQU NEWBUF CMP SFF of the exclusive -Or operation is used as a BSET LOOPFLG. FLAG If no keys pressed in that LDA SFF BEQ NXTCMP column then try the next mask to replace the "bouncing" keys with STA PORTA Set portA all output high. STA TEMPI one else store it their previous state (held in oumur). SCAN CLX INCRX INX BCLR0.PORTA Pull first scan line low CPX , ENDBUF If end of table reached If a valid key state is wrongly interpreted SCANA BSR READCOL As before with 2keyroll BEQ NXTCMP then go compare next as bounce it will he picked up next time over version column with all those LSL PORTA Move scan pulse to next above it round the main loop. Note that if an n -key column LDA X Get a column from buffer roll-over matrix were used instead of the one BCS SCANS If not all done yet then CMP TEMPI and compare it with the continue BNE INCRX stored oneif not equal shown then SOWS!) could be simplified, as BRCLR LOOPFLG. FLAG Rest same as for 2 key try next column OKRTN rollover version SEC Bytes are equal -possible shown at the end of the software listing. BCLR LOOPFLG.FLAG ghost set carry for test since no i/o switching would be required. BSR DEBNCE ROTA RORA BRA SCAN BCS ROTA Also of interestis the ghost checking OKRTN RTS CMP SFF Have got the 1st 0 in carry routine cIIKGiIosT (not required for n -key SCANKBD EQU so dace now not FF roll-over matrices). The detection technique BSET LOOPLG.FLAG Initialise loop flag. BEQ INCRX then there must have been SCAN CLRX BSET GHOST.FLAG more than 1 key in the used relies on the fact that when a ghost key STX PORTA Clear data register and RTS same position in 2 is produced there will always be two columns STX TEMPI Data Direction image columns and so a Ghost register situationset flag and which show two or more keys pressed in the BSET 0 TEMPI return same row positions. Thus if two columns are equal and contain more than one key press then a ghost -key exists. Each column in the matrix image NB% I is only compared with those residing above it in memory to avoid time -wasting duplicate comparisons. Temporary register TEMPI stores the contents of the column that is being compared to the others and TEMP holds the pointer value for the same column. As discussed earlier, once the ghost flag has been set it is only cleared when all keys are released (not just the one causing the ghost).

Jeff Wright is with Motorola in East Kilhride

914 ELECTRONICS& WIRELESS WORLD Analogue circuits for automotiveuses These i.cs, designed to survive the harsh operating conditions found in motor vehicles, can provide substantial cost savings.

ROCCO SHAH

With the increasing use of micro- TABLE 1. - TYPICAL TRANSIENTS ENCOUNTERED IN THE AUTOMOTIVE ENVIRONMENT processors for engine control, trans- Length of Cause Voltage Energy Occurrence mission control, anti -lock braking transient capability and multiplex load control the need has Steady state Failed voltage regulator 18V Infrequent arisen for interface and power switching circuits for interfacing from logic level or 5 minutes Booster starts with 24V battery 24V Infrequent analogue signals to high current, high vol- 4.5-100ms Disconnection of battery during 125v 10J Infrequent tage loads. high charging rates Development of these circuits has been 0.32s Inductive load switching 300V to 80V 1J Often mainly driven by the search for improve- 100V to40V LI Each turn-off ment of total system performance. protec- 0.20s Alternator field decay tion against the harsh automotive environ- 90ms Ignition pulse - disconnected battery 75V 0.5J 500Hz. several times ment. minimum component count and in vehicle life hence lower module costs. 1.0ms Mutual coupling in wiring harness 20C V 1J Often Several environmental factors must be 3V 0 001J 500Hz continuous considered in the selection of automotive 151, s Normal ignition pulse devices. Accessory noise 1.5,/ 50Hz to 10kHz Transceiver feedback 20mV R.f. TEMPERATURE Passenger compartment electronics have a more limited range requirement of -40°C to +85°C, whilst under -bonnet electronics causes as many problems as any other noise level of the vehicle's battery supply. must withstand -40°C to +125°C or even aspect, and reliable data can be difficult to The reset generator provides a reset signal higher. Remember that the junction come by. The load dump transient often to the microprocessor if the regulator out- temperature will be above ambient. hence quoted is actually a worst case. It occurs put falls to 7% below normal level. In the the trend to the lower power dissipation when a battery so flat as to be effectively a event of broken spark plugs or leads. the technologies such as high-speed c-mos. short circuit is disconnected whilst being over -voltage protection circuit provides pro- where the junction -to -ambient temperature charged by an alternator driven by an engine tection to the Darlington. The coil driver differential is generally lower. at maximum engine speed. It can be more output stage has outputs for two coils with cost-effectivefor a car manufacturer to steering logic and constant current logic. SUPPLY VOLTAGES choose lower load dump criteria based on his Finally. the sensor input circuit has been For passenger cars the normal battery vol- experience. He could then save money on all designed for either variable reluctance or tage is + 12V. although +24V systems may units, but would trade this off against the Hall -effect sensors, both of which are popu- be introduced in the future. Unfortunately increased claims that resulted. lar for speed/position sensing. this 12V is not constant: essential systems The car manufacturer may well decide In the system shown, the interface regula- have to operate at 6V. the low point reached that central transient suppression at the tor provides aregulated output with a during cranking. Once the engine is started. alternatoris more cost-effective than a battery voltage down to 6V. The diode the charging voltage at the battery may higher degree of protection at each and every provides protection against reverse battery. reach +16V. With the battery disconnected, unit - particularly as these proliferate. and. in association with a capacitor. en- the alternator will probably produce a con- sures an uninterrupted supply during nega- tinuous +18V: and during a two -battery IGNITION INTERFACE CIRCUITS tive transients. jump start +24V is applied. Not only must Basic building blocks for the interface cir- PRESSURE SENSOR AMPLIFER integrated circuits protect themselves, they cuits are power supply regulator. reset are now expected to protect their loads from generator with over -voltage protection. coil Load sensing is normally effected by measur- damage also. driver outputs and sensor input circuit. ing absolute pressure. Most measuring de- Figure I shows a simplified diagram of an vices suitable for automotive use produce an TRANSIENT VOLTAGES ignitioninjection system based on the analogue voltage output. Transients can appear on any line, with MC68HC05-B6 or MC68HC11, interface cir- Figure 2 shows a manifold pressure various voltages and durations: the probabil- cuit UAA1550. the microprocessor input measuring system with a semiconductor ity of each varies (Table 1). This hazard is protection circuit TCF6000 (Fig.3) and the piezoelectric device MPX100 and a dedicated much more difficult to assess but neverthe- high voltage Darlington BU323. low power dual operational amplifier. The less has to be taken into account if anything The power supply regulator provides an operational amplifier has been designed for other than a worst possible case design output of 5.1V +3% and current capability an output voltage swing from OV to V. a low (which is not necessarily the most econo- of 400mA, adequate for the microprocessor offset voltage (2mV). a large current drive mical) is required. plus other peripheral circuits.Its design capability and an operating temperature Designing for transient survival probably enables it to cope with the voltage range and range of -40 to +125°C.

ELECTRONICS & WIRELESS WORLD 915 Vcc 5 1V Coil A *VBAT Lombdo sensor 5V regulator o R,O Diagnostic Knock sensor Reset PowerVoltage -on monitor reset TCF 6000 Microprocessor Driver select Output A VCL A Output driver A Spor plug AirEngine tempflow temp 00 1\/\/\"v"\/\, MC 68HC05-B6 MC68HC1I fornily Dwell UAA1550Control logic VCL B IA To coil B I ---eVtV BAT Stall Output B IE3 B positionThrottle DESAT 4 Current limit IL L BU 323 ZC Sensor input Magnetic -V BAT (Hall effect) sensor Drivers Injection valves Control SpeedometerIdle speedp. light Fig.lignition and injection module with dual -coil output, based an eight -bit microprocessor (simplified). v MICROCOMPUTER INPUT PROTECTION NETWORK Normally mos and bipolar circuits are sensi- tive to negative and positive voltage spikes. and so care has to be taken to ensure that voltage transients do not reach the micro- computer's i/o pins. Conventional protection units consist of TCF 7000 Output diode resistor networks which do not in general meet the specification over the whole temperature range. Figure 3 shows one of the six input protection circuits developed as an inte- grated circuit. TCF6000. and capable of sinking 10mA at +5.75V and -0.3V. This peripheral clamping array has been opti- mized for microprocessor -based automotive Fig.2. Manifold pressure -measuring system based on a special-purpose dual systems requiring minimal component op -amp. count and low hoard space. Figure 4 shows a typical ignition system protected in this way.

Vdd DATA CONVERSION CIRCUIT In several automotive systems, independent Vref generotor a -to -d converters are used for converting analogue signals from the sensors (such as lambda 'oxygen'. knock, load and tempera- ture) to provide digital inputs to the micro- processor. A low cost c-mos eight -bit a -to -d conver- Eac cell ter MC145040. with serial interface parts to provide communication with micropro- cessors. operates from a single power supply and gives a maximum non -linearity of ±1/s Digital inputs) -1VV\., I.s.b. -V \A, The device provides a successive approx- Microcomputer imation conversion time of 10 micro- seconds. has 11 analogue input channels with internal sample and hold, and has Analogue inputs separate reference voltage and analogue ground pins for noise immunity. Rin

HIGH SIDE DRIVER SWITCH T T In engine and multiplex control modules. Fig.3. Both mos and bipolar inputs in motor vehicle systems need to be guarded high -side driver switches are increasingly against transients: the TCF6000 is made up of six protection networks.I used to drive loads from the positive side of the power supply. The main advantages of high -side switch- -411-Vcc es are corrosion resistance and protection against accidental short-circuits during module inspection or repair. TCF 6000 Figure 5 shows a high -side driver switch, MC:3399T, fabricatedin a power BiMOS process which combines the hest features of VW' bipolar and mos technologies. The device V c Coil INT1 has been designed to drive low current loads BOdrive directly and for intelligent control of low - power relays or solenoid valves. Its output is Engine tempera ure Coil D6 controlled by t.t.l-compatible enable pin. In feed- back the on state, the device exhibits very low MC6805 S2 Pressure saturation voltage (400mV typical) for load DO currents in excess of 750mA. sensor The device also protects the load from Battery volts positive- or negative -going high voltage 2 transients I± 100V1. With its current limit- 111 V s ing and thermal shutdown, it can drive all 111. kinds of loads including inductive ones over 3° Cin a wide temperature range 1-40 to +125°C). Serial diagnostics DASHBOARD DISPLAY Ccr Ignition module Independent display drivers are still used in low cost microprocessor -based dashboard Fig.4. Using the TCF6000 to protect a microcontroller's i/o pins.

ELECTRONICS & WIRELESS WORLD 917 Vs2 5 to 26V

± 125V

Thermol Voltage Current Saturation ASSERT de ect Vio= 0 5v limit limit I (lb lmit) @lout=1A competition All the entries for our 1988 writing competition are now in and are being read by the judges. This is no light task loutto 1 A and will take some time to get through. " but we will he as quick about it as Input t t lthreshold Bi mos ri©0-mos possible. Results will he announced in a control circuit couple of months. The first impression is that the quali- Idrain.25mA ty of entries is good. so that a number Ground Icut. IA will eventually be seen in print after the competition is over. Fig.5. Driver switch based on hybrid bipolar-mos technology.

BPout BPin Out33 Out 2Out)

-- 16 SCITECH 89 33 goted buffers The British Science and Technology Trust Oscillator has accepted an offer from SCS Exhibitions Ltd to stage SCITECH 89 at Alexandra Palace and Park from 17 to 21 May. 1989. The Osc in 33 latches organizers intend that the exhibition shall he housed in the new location each May. Invitations to exhibit are to be restricted to science -based, British companies or those foreign companies which carry out a major Data part of their research and development in Bit 35 Bit34 Bit33 Bit2 Bits Bit 0 Load Britain. 36 -bit shift regis er Clock Control logic The organizers will allocate free space to a Reset limited number of schools, universities and hospitals to allow them to show their scien- tific and technical development. Enquiries should be made to SCS Exhibi- Fig.6. Low -power driver for liquid -crystal displays on the tions Limited, 212 London Road. North End, dashboard. Data input is in serial form. Portsmouth. Hampshire P02 91E. systems because they allow flexibility and free the microprocessor for other tasks. Liquid crystal displays, as used for clocks. Radio -nay pioneer trip meters. information, climate control systems etc.. need low -power display drivers. Harvey Schwarz, joint developer with capable of handling several I.c.d. segments W.O'Brien of the Decca Navigator sys- per package. tem, has died. Figure 6 shows a low -cost c-mos display He came from the American mid - driver for automotive Dashboard applica- West and worked at GEC on the de- tions. It consists of a 36 -stage shift register velopment of radio reception, arriving with 33 latches and output buffers, which in England in 1932 where he went to may drive up to 33 non -multiplexed I.c.d. Decca. As chief engineer, he was re- segments per package. Devices may be paral- sponsible for the development of the leled to increase the number of segments per radio navigation system, spending package with minimal interfacing between some of his time in California working the display and data source. with O'Brien and much of the rest persuading the Admiralty that his sys- Further reading tem was worthy of their attention. Microprocessor -controlled engine management. Fortunately, he was sufficiently persua- by Pat Jordan. Electronics & Wireless World. sive and it was adopted in time to be September 1987. p.876. used in the invasion of France in 1944. Advanced engine management systems. by Pat Jordan. Electronics & Wireless World. December After the war he turned his attentioin 1987. p.1225. to Decca's new long-playing records. He leaves a widow, who was also in- volved in the development of the Decca Rocco Shah is in product marketing at Navigator. Motorola Semiconductors S.A.. Toulouse. Professor Paul Cook of BSTT talking to France. science students

918 ELECTRONICS & WIRELESS WORLD Pan -European cellular demonstration

Research teams at Plessey and Racal give themselves until 1991 to shrink this equipment into a telephone handset. Inside the 19 -inch rack in the photograph is the digital part of a mobile telephone for CSM, Europe's second - generation cellular telephone system. GSM (standing for Groupe Speciale Mobile, a standards -making committee of the Euro- pean PTTs) is a 900MHz system which will use digital speech encoding to achieve about three times the spectrum efficiency possible with the present-day analogue networks. The core of the first GSM network has now been ordered by Racal-Vodafone. Equipment to be supplied by Orbitel, the manufacturer owned jointly by Racal and Plessey, will serve 60 000 subscribers in London and the south- east of England. Work on installing itis expected to begin in 1990, to provide an initial service in June 1991. Vodafone has ordered a second system, from Ericsson Radio Systems, to serve the Midlands and North. Eventually GSM will become the largest single -standard mobile telephone system in the world, with 17 networks all over Europe. Some 9M subscribers are ex- pected to be on it by 1999. The prototype seen here, built by Plessey staff at Roke Manor and demonstrated in London in July, contains most of the fea- tures of a GSM mobile unit. Missing were the frequency -hopping capability, which will enable the system to live with interference, and the long-term predictor section of the digital voice coder. At the distant end of the radio link was a roving light van, fitted with broadly similar 9.6kbitis of data with ab.e.r.of 10'.This equipment has proved that Europe's equipment though cast paradoxically in the Propagation delay through the system cannew cellular telephone system is workable: role of a base station. A call put through by be up to 90ms. now the taskistominiaturizeit.The Orbitel's technical director, Dr David Bal- A crucial feature of CSM radiotelephones complex digital speech coding will result in ston, to Bernard Mallinder of GSM's Perma- will be the equalizer (bottom shelf of thea s3ectral efficiency three times better nent Nucleus in Paris, was clear and free cabinet). By means of advanced digital signal than that of Britain's present cellular net- from interference - though troubled at first processing techniques,thisextracts theworks. Some 17 countries are already by delayed echoes returned through a public wanted signal from the mass of multi -path involved in the project. By 1999, the sys- address system at the Paris end. This call was reflections which are inevitable at u.h.f. in a tenrr is expected to cover a population of coupled at the van to the Vodafone cellular city. With the aid of the equalizer, the digital 300M and to have 9M subscribers. network and was thence routed over ordin- telephone gives acceptable reception with a ary international lines. carrier -to -noiseratio of 12dB: analoguechannel codec and equalizer, each likely to In an operational system, each CSM radio cellular needs 30-35dB. Improvements in be the equivalent of about 600 000 transis- channel would be time-shared by up to eight equalizer design could enhance perform- tors. One potential hitch is that GSM is still conversations, giving a total data rate of ance still further, and would of course enablestruggling to agree on the details of a 270kbit/s. The speech rate leaving the voice the networks to pack more paying customers common radio interface standard; but if no coder (top shelf of the demonstration unit is on to the same frequencies. agreement can be reached. Orbitel and its about 13kbit/s per channel, but to this On the centre shelf of the unit is theassociated companies are prepared to go channel codec adds error -protection and channel codec. which handles the complex ahead with their own joint standard. control data. Because of bandwidth com- signalling procedure between base station Base station hardware for both Vodafone pression. the speech quality sounded dis- and mobile. The 900MHz r.f. unit, runningGSM systems will include Matra designs tinctly gritty: but according to Orbitel the about 5W. is in a separate cabinet on the top. already in use in the French Radiocom 2000 long-term predictor will improve it to theFrequencies used for the demonstration mobile telephone network. Switching will be point where it hardly differs from the aver- were in the band reserved for CSM - 955MHz based on the Ericsson AXE -10 exchange. age analogue cellular quality. The coder is mobile -to -base and 910MHz coming back. Further details from Orbitel Mobile Com- designed to accept a bit error rate of 1 in 100 Work is now in hand to design the all- munications Ltd, Keytech Centre, Ashwood on speech, but the system could manage important v.I.s.i. chips for the voice codec, Way, Basingstoke RG23 8BG.

ELECTRONICS & WIRELESS WORLD 919 NEWPRODUCTS

Fault finding in i.cs connected to each i.c.. the i.c. Programmable Fast repair at component level in number keyed in. and after pressing display module production or field service is possible the test key the results are displayed using the diagnostic information on the monitor. The normal library A programmable vacuum fluorescent obtained from the DIT-24XP digital covers t.t.l. c-mos memory and display has been introduced by i.c. test system. interface devices. Standard Pulseview. Thurlby Electronics' device can interfaces are provided for RS232. The PVFM 35-05-20 can be pre- detect manufacturing defects such as Centronics type printer and an programmed with up to 32 fixed dry joints and faulty i.cs. identify external keyboard. Thurlby messages or 24 fixed and 4 moving unknown i.cs: and test i.cs in -circuit Electronics Ltd. New Road. St. Ives. messages: either by the using a self-contained library. Huntingdon. Cambs PE17 4BG. Tel: manufacturer or by the user with a Operation is simple: a test clip is 0480 63570. standard eeprom programmer. The device provides a single row of twenty characters each comprising a 5 x 7 dot matrix, and each 5mm in height. Multi -pin The module measures connection with no 128 x 34.5mm. Pulseview Ltd. Unit 1 & 2, Suffolk Way. Drayton Road, soldering Abingdon, Oxon 0X14 SJY. Highland Electronics' Swisstac range of front -panel components including switches, pushbuttons and Inductive proximity lamps can be easily installed and sensors replaced using a new multi -pin plug assembly. Contact -free detection of metal All the wires are pre -assembled objects in industrial automation into a three -element contact block applications is offered by Kuhnke's which includes up to 14 flat new inductive proximity sensors. connectors. The connector assembly With 8 switching distances between 1 is plugged onto the rear contacts of and 15mm, the series has bounce the switch unit with no need for free switching with a typical soldering. Each flat connector repeatability of 2%. The switches are measures 2.8 x 0.5mm including capable of operating from either 10- catch and is tin -coated. Highland 30V d.c. or 80-250V a.c. H. Kuhnke Electronics Ltd. Albert Drive. Ltd. Lane End Industrial Estate. Burgess Hill. West Sussex RH15 Lane End, High Wycombe, Bucks 9TN. Tel: 04446 45021. I IP14 3JC. Tel: 0494 882829. Cursor measurement of waveform Complete p.c.b. A cursor measurement system on the parameters. There are four channels design system Hitachi V1100A, 100MHz readout with varying sensitivities on the unit, The entire design process of p.c.bs oscilloscope allows easy which is available from Thurlby from schematic generation through measurement of voltage. time. Electronics. A signal delay line to board artwork can be automated frequency, phase difference and permits viewing of the leading edge with Project p.c.b. ratio. of the displayed waveform on an This software system is designed to The results are numerically 8 x 10cm display with autofocus. be easy to learn and to use. A mouse displayed on the screen to eliminate Thurlby Electronics Ltd. New Road. is used to select menu options, draw the errors associated with visual St. Ives. Huntingdon, Cambs. PE17 lines, define symbols and enter parts interpretation of waveform 4BG. Tel: 0480 63570. Colour graphics locations. Screen windowing helps to Single -hoard layout, smooth speed progress through the package hardware scroll, flash facility. 2MHz without long delays or indirect input operation and a Centronics printer sequencies. Clwyd Technology has port are among the advantages offered to refund the purchase price claimed for the CU -Graph II colour to any customer not satisfied with graphics controller. the package within 28 days. Clwyd Compatible with its predecessor, it Technology Ltd. 99 Leman Street. is designed by Control Universal for London El 8YE. Tel: 01-480 5447. use with EuroBEEB, the BBC Basic - based single -board computer. Three versions of the controller are Small surge arrester available: colour and monochrome each with a Centronics printer port; stops big surges and a low-cost monochrome without An inert gas -filled cylindrical surge the printer port. Control Universal arrester measuring only 5x 5mm is Ltd. 137 Ditton Walk, Cambridge capable of diverting a surge current CB5 8QF. Tel: 0223 244448. of up to 2.5kA and an alternating current of up to 2.5A. Typical applications for the unit designed by Siemens are the highly concentrated main distribution frames for telephone lines. Siemens Ltd. Siemens House. Windmill Road. Sunbury -on -Thames, Middlesex TW16 7HS.

920 ELECTRONICS & WIRELESS WORLD ANEWPRODUCTS

Digital storage Fast digitizing oscilloscope oscilloscope Philips has announced its fastest four memories in which the oscilloscope, the PM3340, with full waveforms can be subjected to Sampling rates of 100M samples/sec 2GHz bandwidth and triggering, processing and automatic can be achieved simultaneously on post -capture waveform processing, measurements. Operation is simple the two channels of Hitachi Denshi's sensitivity down to lmV/div and a through on -screen menus and soft digital storage oscilloscope. dynamic range of 125 to 1. keys plus auto set. Up to eight signals The unit has a memory capacity of The PM3340 uses the principle of can be stored and comparative 4000 words/channel and two 4000 sequential sampling which allows measurements performed easily with word save memories relative to faster signal build-up than is possible on -screen annotation. Philips Test channel 1 which has energy back-up with random sampling at u.h.f. and Measurement, Colonial Way. to hold data for 72 hours. It can frequencies. The oscilloscope has Watford, Herts WD2 4TT. Tel: 0923 handle four samples/period that 240511. enable storage of single shot phenomena at 13.5MHz or 25MHz on one or two channels. Three different modes - envelope, averaging and roll - allow detailed analysis of waveform. The VC6265 has as standard: plotter output; CPIB (binary or BSC II) for computer data input/output; and analogue output Colour display for a chart recorder. Hitachi Denshi (UK) Ltd 13-14 Garrick Industrial modules Centre, Garrick Road. Hendon. Colour display modules offering a London NW9 9AI'. Tel: 01-202 1311. choice of user -selectable line rates from 15 to 35kHz. combined with high performance video inputs are Low -consumption available from Nevin Developments.. power supply i.c. The units measure 183 x 142 x 120mm and the complete A c-mos chip that can supply scan electronics, including the line telephony equipment with 40V to the transformers are mounted on a four -wire network termination in single p.c.b. for ease of installation. accordance with CCITT (S interface) Increased data capture on logic analyser User controls include: height; width; recommendations consumes less horizontal phase and frequency; than 10mW. Data -capture capabilities have been memory than any other logic vertical shift and frequency; This chip has been designed by increased with the introduction of a analyser on the market. linearity; brightness; and contrast. Siemens to replace discrete power logic -analyser system which makes It is supplied complete in a 48in Nevin Developments Ltd. Charlton supply circuits and is suitable for use of a high-speed dram module. rolling cabinet. which contains the Road, Andover. Hants SPIO 3.1L. Tel: voice terminals which are line -fed The K450M system provides up to logic analyser with dual disc drives 0264 332122. and require an internal regulated 10Mbit of data capture on each of its for storage, the memory module, and voltage of 5V. It is also suitable for 64 logic -analyser channels at speeds the PC/AT compatible chassis with terminals that operate in emergency of up to 50MHz and is front panel 80Mbyte hard disc. The PC colour power conditions, for example, after configurable up to 40Mbit per screen and keyboard may he placed Microwave an a.c. power failure. Siemens Ltd. channel of data capture across 16 on top of a convenient work surface. Siemens House, Windmill Road, channels at 200MHz. Gould Gould Electronics Ltd. Instrument modulation analysis Sunbury -on -Thames, Middlesex Electronics claims that the Systems, Roebuck Road, Hainault, More accurate analysis of complex TW16 7HS. Tel: 0932 752323. instrument has up to 4000 times Ilford, Essex IG6 3UE. Tel: 01-500 microwave modulation is possible more full -speed data capture 1000. with Hewlett-Packard's HP 8981A vector modulation analyser. It adds a broadband, coherent I/Q demodulator, covering the 50 to 200MHz intermediate frequencies and carrier range, to the HP 8980A vector analyser introduced in 1987. which provides time, vector and constellation analysis modes. The additional front-end vector demodulator processes a 35MHz I/Q bandwidth (for up to 70MHz channel measurement). External filter ports are available for use with 200MHz channel measurements. After digitally processing the signal the analyser displays constellation parameters, quadrature error, l/Q imbalance and d.c. offsets in visual as well as digitally annotated form. Hewlett- Packard Ltd. Eskdale Road. Winnersh Triangle, Wokingham. Berks RGII 5DZ. Tel: 0734 696622.

ELECTRONICS & WIRELESS WORLD 921 NEWPRODUCTS

Real-time control Power transistor for BBC modules Separate driver stages in a.c. and d.c. microcomputer motor controllers, power supplies. A real-time control interface for the converters and other industrial BBC microcomputer has been equipment are not needed with the designed with schools, laboratories new range of power transistor and home users in mind. modules from Mitsubishi The Termite interface from Paul Semiconductors. Fray provides eight terminals, These high -gain versions of the independently programmable to any QM series consist of six pack combination of i/o. and it connects configurations for three-phase directly to the user port of any model bridges as well as dual driver stages. BBC computer. It is powered either Voltage ratings are 600 or 1000V. and directly from the BBC or an external current ratings range from 10 to power supply and can be used to drive 200A. Mitsubishi Semiconductors. motors, relays, detect sensors or Mitsubishi Electric UK Ltd, simply light up bulbs. Paul Fray Ltd, Electronics Division. Travellers Willowcroft. Histon Road. Verbal communication Lane, I latfield. I lertsAL10 8XB. Tel: Cambridge CB4 31D. Tel: 0223 07072 76100. 66529. between man and machine Verbal command and response the host computer. The speech between user and personal, micro, recognition technology allows a mini or mainframe computers is continuous flow of verbal input at achieved by the Verbex 5000 voice i/o natural human speeds, regardless of system. language or dialect. Voice cartridges The system from Decade can be easily changed by front Computers uses a two-way serial loading. Decade Computers Ltd. connection at up to 19 000baud Ringway House, Kelvin Road, through a standard RS232 -C port on Newbury, Berks RG13 2BD.

Diode arrays reduce assembly time Where large numbers of diodes need incorporating on densely packed p.c.hs. assembly time can be reduced Signal analyser using Iskra's sil or dil diode arrays. allows custom - The dual in -line arrays are housed in standard 16 -pin plastic packages measurement sealed in flame-retardant epoxy Many test and automation features resin. Each pack contains eight that traditionally have required the independent 1N4148 epitaxial signal use of an external computer are diodes or the BZY 88 range of included in the Hewlett-Packard diffused junction zeners. two -channel dynamic signal Single in -line networks consist of analyser. either common -anode or common - The HP 35660A fast Fourier cathode 1N4000 series diode chips transform -based analyser has which are bonded on to a ceramic applications in electronics. substrate. The lead -outs are on a mechanical testing, acoustics and Prototype p.c.b. is also production board standard 0.1in pitch for other low -frequency areas in both compatibility. Iskra Ltd, Redlands. production/process and r. and d. Transition from a prototype p.c.b. to layers. Insulated wires allow signals Coulsdon, Surrey CR3 2HT. Tel. 01- environments. It provides spectrum a final production board has been to cross and provide the shortest 668 7141. analysis from zero to 102.4kHz and made easy by the introduction of paths. Each layer is soldered to the network analysis from zero to Augat's Unilayer II board modules. plated holes and then bonded to the 51.2kHz. These have a high -density, plated - board with adhesive. A finished board Using HP Instrument Basic which through hole pattern on a grid of may have six or more layers. Boards runs inside the analyser without the standard pitch. Supply and ground used with the system are available in need for an external computer, test buses are already etched on either all the popular formats for use in sequences are simplified. Advanced side of the board and, for P.Cs, VMEbus and other systems. users can create custom algorithms prototyping, it is fitted with wire - Augat manufactures the modules and result formats to provide wrap pins. from the prototypes and says that its answers not directly available from For production, the same pattern service is much faster than the standard analyser. Hewlett of module is used by the wire conventional multi -layer boards. Packard Ltd. Eskdale Road. wrapping is replaced by soldered Augat Ltd, Sunrise Parkway, Linford Winnersh Triangle. Wokingham. wires produced by the Unilayer II Wood East, Milton Keynes MK14 Berks RG11 5DZ. Tel: 0734 696622. wiring system to give high -density 6LF. Tel: 0908 676655.

922 ELECTRONICS & WIRELESS WORLD rNEWPRODUCTS

Multicore cable use -Girl Electronic key for analyser security The latest industry requirements for An electronic key has been designed testing cables up to 1000V d.c. are by Dallas Semiconductor as part of a met in the upgraded multicore cable range of miniature security systems analyser available from Cable Check for software and other data. Systems. Constructed to be carried around The analyser can be used for a in the pocket, the device stores 64 complete serviceability test on MAIN MINU bits of user -definable identification [leer screen multicore cables on or off site. Vierporl code and a 64 bit security match code Results are displayed digitally, along Archive Disbrazt which protects 128 bits of read/write with core numbers for easy Analyze non-volatile memory. The P200m t Fen identification. A hard copy of fault Con identification and security match Filler locations and test acceptance levels Were codes are programmed into the key Image edit can be obtained using the integral Program after which it follows a special printer. Cable Check Systems. 18 Mternel Prole procedure with a serial format to lo Quay Lane, Gosport. Hampshire retrieve or update data. Dialogue P012 4L1. Tel: 0705 528396. minify iwanel.lo Distribution Ltd. Wicat House. 403 Real-time video digitization Digital wattmeter Stacking dot matrix The Il3M PCINturned into an trudge in the PC and features an eight bit A high resolution digital wattmeter processing workstation using a a -to -d for 256 grey levels/pixel; manufactured by Infratek is suited to display hardware and software package advanced phase -lock for stable the measurement and analysis of called PCVisionplus Frame Grabber. synchronization with v.c.rs: A two colour 101mm dot matrix distorted waveforms. display element designed for easy The package from Amplicon programmable gain and offset and a The single phase 103A available Electronics is composed of four 1024 x 512 x 8 bit frame memory p.c.h. mounting is stackable both from Lyons Instruments features a vertically and horizontally to form major sections: video source stores multiple images. Amplicon wide frequency range from d.c. to interface; frame memory: display Electronics Ltd, Richmond Road, large alphanumeric displays. 100kHz. voltage ranges to 1000V and logic and host computer interface. It Brighton, East Sussex BN2 3RL. Tel: The LTP-4357AA 5 x 7 dot single - current to 50A without external occupies only a single expansion slot 0273 608331. plane device is intended for accessories. Power ranges are from applications such as computer - 9mW to 50kW and the unit has a controlled message hoards. It six -digit display with a basic accuracy Probe identifies metals of 0.3%. Lyons Instruments Ltd. Hoddesdon. I lerts. Tel: 0992 467161. Identification of the carbon content investigation and the metallurgical in ferromagnetic steels, the characteristics are identified by chromium content in stainless sensing the electrical effects steels, the alloying elements in produced in the probe. Changes of carbide tool alloys and the amount of inductance and the inductance -to - retained austenite in austempered resistance ratio of the sensing coil ductile iron can be carried out simplyare all measured. Kontron using the Metal Analyser available Electronics Ltd. Blackmoor Lane. form Kontron Electronics. Croxley Centre. Watford. Hots WD1 The analyser's probe is placed 8XQ. Tel: 0923 45991. against the material under

incorporates green gallium Four -channel oscilloscope phosphide and orange gallium The simultaneous observation of switch selects the appropriate time arsenide phosphate elements on a multiple signals is possible using the base for the signal to be measured. A transparent substrate. The elements Grundig MO 100 four -channel seven segment led digitally displays have individual pins for each colour. Power supply units 100MHz oscilloscope available from the time range. The conventional producing 28 pins on the rear face of the package. The light output The first of a series of compact, Instrumex. stepping switch for setting the time The trigger level position on the sweep is replaced by a potentiometer. ensures that either colour is visible o.e.m. power supply units capable of in normal artificial lighting delivering up to 1500W d.c. output screen is shown by a cursor and can Instrumex Ltd, Dorcan House, Meadfield Road, Langley, Berkshire conditions. Selectronic Ltd. The Old has been introduced by Weir be selected to trigger from a specific point. An automatic time -range SL3 8AL. Tel: 0753 44878. Stables. 46 Market Square. Whitney. Electronics. Oxon OX8 6AL. Tel: 0993 73888. The series, based on an advanced switched -mode regulator, is to include single output and multiple output configurations to meet Flat electrolytic industry requirements. All models capacitors are housed in a metal enclosure measuring 279 x203 x 127mm with Half-size versions of the Petchacon an integral cooling fan. range of thin electrolytic capacitors Now available is the SMM 1500 00 have been introduced by ECC 00 which has five output rails. The Electronics. The 7mm thick devices combined load rating is 500W but if are suited to applications where higher power levels are required the height is restricted. They are units can he connected in parallel to available with capacitances ranging provide outputs as high as 3kW. Weir from 180 to 15 000µF ECC Electronics Ltd. Durban Road. Electronics (UK) Ltd, 9 Blenheim Bognor Regis. Sussex P022 9RW. Road, High Wycombe. Bucks HP12 Tel: 0243 865991. 3RT. Tel: 0494 450716.

ELECTRONICS & WIRELESS WORLD 923 rN-EwPRODUCTS

Fixtureless test Input switches for system p.c.b. mounting An in -circuit test system called the A range of input switches designed Takaya APT -2200N uses three for mounting on to p.c.bs is available moving probes and functions as an from Highland Electronics. impedance signature analyser to The polyester switches can be perform tests on a loaded hoard. illuminated with a choice of coloured Contax supplies the fine -tipped leds, 3mm in diameter. Key caps are probes for contact spacings down to available in ten colours and have 11.1mm. so the latest surface mount either a pulse or latching function: and hybrid devices can be tested on a they are pushed on to the switch as a non -fixed test bed. Also the probes module. There is a single break. have a height clearance of 15mm self-cleaning, snap -action switching allowing either side of a loaded hoard element and the contacts are gold to he probed. plated to give a mechanical life of Board sizes up to 400 x 350mm 5 x 10' operations. Highland can he handled and each test takes Improved reception for shortwave listeners Electronics Ltd. Albert Drive. about 0.5s. making the system Listeners will appreciate the eight preset frequencies. which are Burgess Hill. West Sussex RH15 suitable for low volume production. improved quality of the reception of chosen according to the user's 9TN. Tel: 04446 45021. Using bar coding techniques, test the BBC World Service using the location. programs are called off disc or from Liniplex F2 receiver. A linear phase -locked fully another computer station as each This receiver system, available automatic synchronous hoard arrives at the test station. from Phase Track. is based on demodulator reduces the effects of Contax. 362 Spring Road. Sholing. receivers supplied for off air fading and interference. Total Southampton SO2 7PB. Tel: 0703 broadcast relays to BFBS in the frequency range available is from 434141. Falklands. Belize. Gibraltar. Cyprus. 0.15 to 26.1Mliz. Phase Track Ltd. 16 Hong Kong and Nepal. Now a Britten Road, The Robert Cort synthesizer covering 2-22MHz is Industrial Estate. (Elgar Road). offered in addition to the standard Reading RG2 OAU. Tel: 0734 752666.

Television and video testing Trouble -shooting and testing of Available from Instrumex. both offer television, monitors and video a choice of over 70 colour patterns equipment are easily carried out and combinations which are selected using the Philips PM5514 and using push -buttons on the display PM5514V colour pattern generators. panel. Sound modulation is also The MP5514 is intended for provided, with a choice of internal monochrome and colour television and external modulation modes and testing and the PM5514V with CVBS a switchable carrier signal. and RGB outputs meets the Instrumex (UK). Dorcan I louse. requirement of the video equipment Meadfield Road, Langley. Berks SL3 and computer monitor markets. Ml.. Tel: 0753 44878. One GAL replaces 21 Modular logic analyser has 112 channels pals A multi -level conditional trigger - general purpose computer with a Twenty-one different 20 -pin pal trace sequencer controls the 112 CP/M Plus operating system. devices can he replaced by one of channels of timing and state analysis 1.4Mbyte of storage on dual floppy Thomson Microelectronics 16V8 on the Thandar TA3000 modular disc drives, qwerty keyboard and full series of Generic Array Logic devices logic analyser. IEEE -488. RS232 and Centronics supplied by ITT Multicomponents. Complex acquisitions can be set up communications capability as The series uses a floating gate rapidly using the soft -key guided standard. Instrument Rentals (UK) concept which means the user can Two -wire pressure menus and displays. Instrumex Ltd. Dorcan House. Meadfield Road. electrically erase and reprogram the transmitter supply the analyser which has a Langley. Berks SI,3 devices several times. Other features of the 16V8 include an active supply Excitation voltage and current current of 90mA (compared with output are transmitted over the same 180mA for pals): an i/o propagation pair of wires in the model BL flush delay time of 15-20ns and a 5V diaphragm pressure transmitter. operating voltage. Control Transducers offers the The GALs have logic copying and unit in various pressure ranges from hulk erase facilities and a 64 hit 0.35 to 1400 bar. Overload is two register which can he programmed times rated pressure without damage to contain user defined data. They and five times without bursting. use ABEL and CUM. compilers both Excluding the connector. the unit of which run on the IBM PC and measures 24 x 98mm and is suitable compatibles. The series is available in for applications where ease of dual in -line plastic packages. ITT cleaning and sterilization are MULTIcomponents Ltd.:146 important, such as film processing Edinburgh Avenue. Slough. Berks and the food and drink industry. SI.1 4TU. Tel: 0753 824131. Control Transducers. North Lodge. 25 Kimbolton Road. Bedford MK40 2NY. Tel: 0234 217704.

924 ELECTRONICS & WIRELESS WORLD COMMUNIQUE UK LTD, COMMUNICATIONS HOUSE, ftk'COMMUNIQ PARLEY AVENUE, LONDON NW2 1SB. TEL: 01-450 9755TELEX: 298765

HX307 2 Channel HX307V 4 watt 160-174MHz HX307U 3 watt 450-470MHz

H X417 25 Channel art HX4107V 5 watt 160-174MHz HX4)7U 5 watt 450-470MHz UKV62/2 25/40 w t 66-88MHz 425/40 1:)0-175M 25/35 wa 420-470M) iz UKV62/4 Mini 10 watt 1-170MHz SEE US AT COMEX '88 STAND No. Al

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51 k ..ia, VALVES QUALITY Please phone tor firm cluotatoon V A 1ircluded Atut.s 1.40 LI bu 0.65 PCL84 0.85 Z803U 21.15 6CH6 7.50 11E2 19.50 A2293 7.00 E F83 3.90 PCL86 0.80 Z900T 4.30 6CL6 2.75 12A6 1.00 A2900 12.75 EFFIS 0.90 PCL805 85 0.95 1A3 3.80 6CW4 7.00 12416 195 Forole:. 0061 t2061 AR8 1.15 EF86 1.45 PD500 510 4.30 1L4 0.65 6CX8 4.60 12417 1.25 ARP3 1.15 E F89 1.60 PF L200 1.10 1115 1.00 8oys 1.15 12AU7 0.95 2.50 12A07 1.10 co, 651 ARP35 1.15 E.F.31 1.60 PI -L200' 2.80 1S4 1.00 6D6 12BA6 1.80 ATP4 0.90 EF92 2.15 PL36 1.60 1S5 0.75 61-60 1.95 B12H 1 T4 1213E6 110 6.90 EF.95 1.90 PL81 1.30 0.75 61-6GB 1.10 1U4 2.80 129H7 145 CY3I 2.40 EF96 0.60 PL82 0.70 0.80 6F7 DAF 70 1.75 PL83 0.90 2X2A 3/0 6F8G 0.85 11 19.95 P EF183 0.75 12J5GT 0.55 DAF 96 0.90 PL84 3A4 1.30 61-12 1.60 EF 184 0.75 0.90 12K7GT 1.15 DET22 PLSO4 1.25 3A T 2 3.40 61-14 32.80 1-,2 1210301 1.25 EF812 0.75 2.00 31328 17.50 DF92 0.65 .. PL508 6F15 3-`9 1207GT 1.15 OF% 1.15 ,`,..--`,.,,'-'9 ...f PL509 5.65 31328' 19.50 6F17 3.10 0.85 125C7 0.80 01176 1.15 r-'"' PL519 5.85 306 0.60 61-23 0.75 125117 1.25 E L32 0.85 DL92 1.45 PLE10251 3.45 3E29 21.85 6F24 1.15 12S.17 1.40 0986'87 0.65 EL34 3.25P980 0.70 354 1.45 6F33 10.50 12SK7 1.45 D9802 0.70 EL34' 5.95 P981 800 0.85 4E132 40.25 6FH8 18.80 12507G /2.20 SEND FOR DETAILS ABOUT E92CC 2.80 EL82 0.70 P982 0.75 511409 3.35 6GA8 0.65 1294 0.70 E 180CC 11.50 E L84 1.35 P988 0.60 SU4G 1.85 6GH8A 0.90 1303 2.80 E1148 0.75 EL86 1.45 P9500A 2.10 5V4G 1.90 6H6 1.60 1306 0.90 EA76 110 E L90 1,75 00V03 10 5.95 SY3G I 1.90 6J4 1.95 19A05 1.85 A BRILLIANT NEW EB34 1.15 E1,9 1 6.50 00V03 10' 7.50 513 4.85 6J4WA 3.10 19G3 11.50 EB91 0.60 E L95 1.80 00V03 20A 27.50 5740 1.25 6.15 2.30 19G6 10.35 EBC33 2.20 E L504 2.70 0006 40A 28.50 51401 2.20 6.15G I 1.50 19H5 38.00 2.202001 0.80 EBC90 0.90 E L519 7.70 00001,409' 54.10 6 30L2 0.80 636 PRODUCT WHICH EBC9I 0.90 0V03 12 5.75 6AB7 0.70 6J6W 2.80 28E1 1 30 E L821 8.05 0.60 EBF80 015 E L822 995 SP61 2.50 6AC7 1.15 6JE6C 8.45 2V I EBF89 0.80 1121 4510 6AG5 0.60 6JS6C 8.45 25L6G I 1.60 ELL8OSE 4.50 2324G 0.75 EC52 0.65 em80 1.35 1122 45.00 6A65 1.90 6JU6 6.35 85A2 1.40 GREATLY INCREASES THE EC9I 0.75 6AK6 2.85 61( 7 1.45 4.00 EM87 UABC80 2.55 100 6ALS 8iA2' EC92 1.85 190 UBF 80 0.70 0.60 6KD6 8.10 572B 6110 ECC8I 1.25 UBF 89 0.70 6ALSW 1.50 6L6 7.10807 E Y81 3.45 ECC82 015 1-2 UCC84 0.85 6AM5 6.50 6L6GC 8.10 897. 4.30 UTILITY & FUNCTIONS OF ECC83 1.10 [988 87 0-'. UCC135 0.70 6AM6 1.60 6L6G I C 2.90 E 988 0.65 8.1 IA 13.50 ECC84 160 UGH42 2.50 6AN8A 3.80 61,18 0.70 812A E180 32.00 ECC85 0.75 0.80 RCH81 0.75 6A05 1.75 6LD20 0.70 813 28.50 ECC88 1.10 EZ81 0.80 UCL82 1.60 6A05W 2.30 6L06 8.45 913' 44.00 THESE RECEIVERS ECC189 1.20 GM4 8.90 UF41 1.85 6AS6 1.15 607G 1.30 829B 16.00 UF 80 ECC804 0.65 GN4 6.30 160,,L 6AS7G 4.95 6SA7. 1.80 82913' 24.00 UF 85 , ' ECM 1.25 G9501 1.50 11-, 6AU6 0.90 6SG7 1.80 866E 14.95 ECF82 1.15 GZ32 1.90 UL84 1.50.,,.. 6AX4GT 1.30 6S -i7 1.80 5314 13.95 ECF002 1.80 G133 4.20 UM80 6AX5GT 1.30 6SK7 1.85 UM80' 1°. o31A' 19.80 ECH42 1.65 2.45 2-38 6BA6 1.40 6SL 7G T 3.50 1.10 0134 UM84 0.95 964 ECH81 1.25 GZ34' 4.40 6B86' 1.85 6SN7G I ISO 555 1.10 UY82 0.70 6507 0.95 ECH84 0.90 GZ37 395 6BE6 1.40 956 1.20 AIRCASTLE PRODUCTS U985 0.85 65117 4.60 ECL80 0.65 6177" 14.00 1.85 5.75 VR105 30 2.45 66E6' 6V6G 1.50 L,.,5783 ECL82 6T88" 6BG6G 1.60,. 0.75 25.03 911150 30 2.45 6V6GT 1.40 '''''"Ln' 1.95 ECL85 0.75 ML4 3.20 061M 1.70 61336 1.'" 604 1.50 6080 7.30 ECL86 1.10 ML6 120 X66 4.95 6B07A 0.85 605G I 0.756136 2.80 P.O. BOX 78 EF9 3.50 M012001 29.50 1749 0.75 68137 4.80 696G 2.80 614613 11.90 E F22 3.90 N78 9.90 .37'.0 19.90 6BW6 6.10 6Z4 1.75 9001 1A0 E 1-378 2.15 t 332 1.80 3.45 6BW7 1.50 714 1.90 9002 6.50 IIt 30 1.10 3., . 8. 0 95 3.75 6C4 1.20 906 2.15 9003 8.50 VALVES AND TRANSISTORS NEW HEADSETS ..,,,,J. ill microphones BOURNEMOUTH CAROL HP.339M at E10.00 1,101,1,1 .19 103.1 1,111,1, I," Headphone imp 4-16 ohms Microphone imp 31600 olys, FIELD TELEPHONE. CABLE TYPE DIO E-80 at 215.00 FIELD TELEPHONES TYPE .£. Tropical In metal cases Headphone Imp 4.16 ohms Microphone imp at tun BH1 4SP 10 -line MAGNETO SWITCHBOARD Can work with ohms Surplus VIDICON P8211 and othets at f 18 00

POSTAGE AND PACKING CHARGES I't 1.'355p £3 I:5 65o CS C10 85p £10 1,15£1 OS 3.1 5 1 201'1 60 OVel

, .. £2011.' 1,lI . , ..5 at Cot.3 (0202) 666233 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. PLEASE STATE WHICH RX YOU HAVE ENTER47 ONREPLY CARD ENTER 23ON REPLY CARD

ELECTRONICS & WIRELESS WORLD 925 COUNTERS & OSCILLATORS LEVELL OSCILLOSCOPES COUNTERS MET100/600/1000,1500 CROTECH SINGLE TRACE 20MHz 3031/36 8 digit 0.5" LED. 5Hz up to 100/600/1000/1500MHz. for INSTRUMENTS 2mV10V/div. 4Ons-0.2s,div. Cal 0.2V Component test. Resolves 0.1Hz. Sensitivity 5mV up to 10MHz. Low pass 3031: CRT 1 5kV 5x7cm 3036: CRT 1 BkV 8x10cm filter. Mains/rechargeable battery powered. HAMEG DUAL TRACE 20MHz 102mVI HM203-6 LEVELL RC OSCILLATORS TG152D/D61 * REDUCED PRICES * 2mV 20V cm Ch2-± ChlXY. Cal 0 2V 2V 1kHz sq 3Hz-300kHz. 5 ranges, acc 2% + 0.1Hz up to 100kHz, 20ns-0 2srcm. Auto. normal or TV tng. Component test 3% at 300kHz. Sine or square <20014V to 2.5Vrms. Distn. HAMEG DIGITAL STORAGE 20MHz HM205-2 <0.2% 50Hz-50kHz. TG152DM has an output meter. DIGITAL MULTIMETERS 2mV 20V cm Chl Ch2 Single shot and X -Y modes HC5040T 2Ons-0.2s cm. Auto, normal or TV trigComponent test. LEVELL RC OSCILLATORS TG2000/DMP £32 Cal 0 2V 2V 1kHz.5Mfiz sampling Two 1K memones 1Hz-1MHz. 12 ranges. acc 1.5% +0.01Hz to 100kHz. 2% HC4510 £52 Dot Joining feature Y outCRT 2kV 8x10cm. at 1MHz.Sineorsquare outputs <20014V-7Vrms. Distortion <0.05% 50Hz-15kHz. Sync output >1V. TG2000MP has output meter and fine frequency control. FUNCTION GENERATORS TG302 £112 TG303 £185 FREE UK DELIVERY VAT EXTRA

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HC DIGITAL MULTIMETERS HC5040/5040T 3'zr digit12 7mm LCDUp tolkVdc, 75OVac, 104 20MS2 Resolution100µV.100nA. 10m0 HITACHI DUAL 20MHz V2121222/223 lmV-12Vicm. 20MHz at SmV. Ch1±Ch2. X Y 15040T:100mR) BuzzerdcV 0 25% Batterylife Chl LEVELL FUNCTION GENERATORS TG302/3 2000hrs 5040T: has a TR test output.100ns-0.5s/cm. Auto,normal or TV trigger. 0.02Hz-2MHz in 7 ranges. Sine, square, Mangle, pulse and Cal 0 5V 1kHz square. Z input. CRT 2kV 8x10cm. ramp 2OrnV to 20Vpp from 500. DC offset 0/±10V. TTL HC DIGITAL MULTIMETER HC4510 V222: Plus DC offset and alternate magnify function. output. TG303 also has a CMOS output and 6 digit 10MHz 4 digit 11mm LCD Up to 1kVdc, 75OVac, 10A, 20M0 V223: As V222 plus sweep delay 14-100ms. counter with INT/EXT switch. Resoln. 100V. 100nA, 10m0 Buzzer dcV 005% LEVELL DIGITAL CAPACITANCE METER 7705 LEVELL DECADE BOXES TEST METERS 0 1pF 2000oF acc 0 5% 3'i digit 12 7mm LCD. C8410/610 4 6 decs. 10pF steps. acc 1% :t2pF. LEVELL INSULATION TESTER TM14 R401/4104 decs 10 or 1011 steps, acc 1%, 2.5W WELL AC MICROVOLTMETER TM3B Log scale covers 6 decades 10M010112 at 250V, 500V, 16 ranges 15yVfs,500Vfs. accuracy 1%+ 1%fs R601/610 : 6 decs. 112 0(100 steps, acc 1%, 2.5W 1uV 750V,110/,IM17S2 at 25V -100V:100k 100GS2 at R601S : 6 decades. 111 steps, acc 0.3%. 2 5W - 20dB/ + 6dB scale ±3dB 1Hz 3MHz 150rnVfs output. 2 5V 10V. 10k 10G1-2 at 1V Current 100pA 100srA 8701 : 7 decades. 10 steps, acc 1%, 2.5W

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SMALL SELECTION ONLY LISTED IN VIEW OF THE EXTREMELY RING US FOR YOUR REQUIREMENTS WHICH MAY BE IN STOCK RAPID CHANGE TAKING PLACE Latest bulk Government release - Cossor Oscilloscope CDU150(CT531/3) £150only.Solidstategeneralpurpose IN THE ELECTRONICS bandwidth DC to 35MHZ at 5MV/Cm - Dual Channel - High brightness display (8-10cm) full delayed time base with gated INDUSTRY, LARGE QUANTITIES mode - risetime1 ONS illuminated graticule - Beam finder - Calibrator 1KHZ squarewave power 100 - 120V 200V - 250 volts OF COMPONENTS BECOME AC - size W 26CM - 14CM deep - WT 12.5 KG - carrying handle, colour blue, protection cover front containing polarized viewer and REDUNDANT. WE ARE CASH camera adaptor plate - probe (1) - mains lead. Tested infair condition with operating instructions -£150.00. PURCHASERS OF SUCH Racal RA17L Communications Receivers. 500KC/S to 30MC/S in 30 bands 1MC/S wide from £175. All receivers are air tested and MATERIALS AND WOULD calibrated in our workshop supplied with dust cover operation instructions circuit in fair used condition - Racal Ancillary Units APPRECIATE A TELEPHONE for all receivers mostly always in stock - Don 10 Telephone Cable CALL OR A LIST IF AVAILABLE. 1.2 mile canvas containers or wooden drum new from £20 - Army Whip Aerials screw type F sections and bases large qty available WE PAY TOP PRICES AND now P.O.R. - Test Equipment we hold a large stock of modern and old equipment. RF and AF Signal Generators - Spectrum COLLECT. Analysers - Counters - Power Supplies - Oscilloscopes - Chart Recorders all speeds single to multipen - XY Plotters A4 A3 - Racal Modern Encryption Equipment - Racal Modern Morse Readers and Senders - Clark Air Operated Heavy Duty Masts P.O.R. All items are bought direct from H M Government R. Henson Ltd being surplus equipment price is ex -works. S.A.E. for enquiries Phone for appointment for demonstration of any items, also 21 Lodge Lane, N. Finchley, availability or price change V.A.T. and carriage extra. London N12 8JG. EXPORT TRADE AND QUANTITY DISCOUNTS JOHNS RADIO, WHITEHALL WORKS, 5 mins. from Tally Ho Corner 84 WHITEHALL ROAD EAST, BIRKENSHAW, BRADFORD, BD11 2ER TEL NO. (0274) 684007. Telephone: WANTED: REDUNDANT TEST EQUIPMENT VALVES PLUGS SOCKETS, 01-445 2713/0749 SYNCHROS ETC. RECEIVING AND TRANSMITTING EQUIPMENT ENTER ON RE:1'1,11 CARD I \ II (I\ ) I \1;l1

ELECTRONICS & WIRELESS WORLD NEWPRODUCTS

Desk -top flatbed Fast i.c. design plotter Engineers can specify i.c. designs in an easy -to -use high-level language, high level of accuracy in photo - plotting is brought to PC CAD users simplifying the design process and by the compact Flashscan flatbed reducing the chance for error with plotter. VLSI Technology's enhanced state- machine compiler. Measuring only 16 by 20in, it is made in Switzerland by Patek This version offers the user fast Philippe and marketed in the UK by compilation, automatic state ..... assignment, readable output Kontron Electronics. It uses a IL firmware -controlled variable - information, and an improved aim aperture system which projects q.). system of control over fan -out that )owt)oveeocivile#40 prevents signals from being images onto a film. These images V4:4:4:066) ittiiihr#E# create pads from 0.12 to 2.54mm 0,42,44.eilfectid) overloaded. The company claims that with 135 steps in between. The pads eeee&tteOte in less than a day a designer can enter are used to create lines of any width a complex design by simply writing a as well as user -defined graphic few dozen lines of instructions at an symbols. Kontron Electronics Ltd. engineering workstation. Using Blackmoor Lane, Croxley Centre, Compact instrumentation recorder traditional design methods, the same Watford, Herts WD I 8XQ. Tel: 0923 Up to 24 channels are available in the including vibration. noise and design would have taken weeks of 45991. V -Store portable video cassette performance monitoring. The development. VLSI Technology Ltd, instrumentation recorder. Racal recorder is simple to operate, uses 486/488 Midsummer Boulevard, Saxon Gate West, Central Milton Recorders claims this instrument is easily available VHS tapes and has a Compact mosfet the most compact recorder of its type.high -contrast electroluminescent Keynes MK9 2EQ. Tel: 0908 667595. Recording signals from all types ofdisplay screen with associated soft modules sensors with electrical output from keys. Racal Recorders Ltd, Hardley Plug-in terminal International Rectifier's new CPX200 d.c. to 100kHz, the unit is ideal for Industrial Estate, Hythe, series 250 and 500V H -bridge use in medical, military, automotive Southampton, Hants SO4 6ZH. Tel: blocks Modular terminal blocks that can be modules replace four TO -220 devices and general industrial research 0703 843265. with a single in -line nine -pin built up to any number of moulded package. terminations have been introduced by IMO Electronics. Designed for high -density p.c.b. applications including medium/high The 20.900 Series has two- and power supplies, u.p.s. systems, high three-way modules in horizontal and voltage motor drive systems, and vertical plug-in units for attachment servo amplifiers the fully isolated to on -board soldered pin connectors. package measures only 0.2in thick by To prevent incorrect connection 0.75in high. It can be mounted without losing a pole a tiny key is directly on to the chassis or heatsink. inserted into the block. This avoids International Rectifier, Hurst Green, the need for blank terminals or end cheeks to achieve polarization. IMO Oxted, Surrey RH8 9BB. Tel: 0883 713215. Electronics Ltd, 1000 North Circular Road, Staples Corner, London NW2 7.IP. Tel: 01 452 6444. Memory gets battery back-up High -voltage The memory in Instrumatic's ICD mosfets emulators can be protected by a There are three new high -voltage battery back-up to overcome n -channel mosfets specifically problems associated with memory 68030 computer tailored with on -resistance ratings volatility. previous 68020 -based products. Existing systems can be updated with Clock speed ranges from 16 to that support the requirements of test The incoming memory Vcc is equipment and telecommunications. the Plessey Microsystems PME 68- 33MHz. The system has a 4Mbyte monitored and if an out -of -tolerance 32, a single -board computer which is Siliconix claims the VN50300, condition occurs a lithium power dram which is dual ported, giving optimized for disc -based, single and fast access from the processor and which is an ideal voltage -spike source is automatically switched on multimaster system architectures protector, is the first 500V device and write protection is VMEbus. The memory is able to that run on Unix 5.3. available in the SOT -23 surface - unconditionally enabled to prevent support the cache burst fill of the It is suited to real-time mount package. The other two corruption of data. The battery back- 68030 processor, giving up to a 15% applications with multi -processor devices are 400 and 350V models up memory option supports standard improvement over cards not having support. The board is based on the providing high -voltage, low on - ZAX memory of 128K or extended it. Hi-Tek Electronics, Ditton Walk, 68030 processor and gives about two resistance operation in systems memory board of 512K. lnstrumatic Cambridge CB5 8QD. Tel: 0223 to three times the performance of 213333. using low-level power supplies or UK Ltd, First Avenue, Globe Park, c-mos logic. Siliconix Ltd, 3 London Marlow, Bucks SL7 1YA. Tel: 06284 Road, Newbury, Berks RG13 1.1L. Tel: 76741. Sustained performance at 20mips 0635 30905. 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928 ELECTRONICS & WIRELESS WORLD RESEARCHNOTES

effects or even introduce false wear out. It also appears that a Dr Bill Hardcastle, Reader in Space-age colour to help those with specific ferroelectric memory is Linguistic Science at Reading forms of colour blindness. radiation -hard, which will give it University, told the symposium vision aid The whole project, lasting five instant applications in space as that advances in the EPG system Researchers at NASA and at the years and costing II 1million well as the nuclear industry and mean that it is now a viable and Johns Hopkins Wilmer Eye Insti- should. say its developers, lead to military projects. proven technique for both ther- tute are to adapt a vision systema practical device that is afford- apy and speech research. EPC designed originally for spaceable by elderly people on fixed records have shown that indi- robots to restore sight to the incomes.In more concrete Electronic vidual speech sounds such as 't', almost -blind.It'sessentially a terms they talk in terms of the 'k' and 's' have specific tongue portable closed-circuit television cost of two colour television sets. speech therapy contact patterns and that these system that will produce bright patterns can change in predict- pictures directly in front of the Significant advances in the use of able ways depending on a num- eyes via what looks like wrap- Memories that a computer -based technique to ber of factors like how fast the round sunglasses.Instead of aid speech therapy were de- person is speaking, and which lenses, the sections covering the last for ever? scribed at the first National Sym- sounds precede or follow, and so posium on the Clinical Applica- on. By comparing these patterns eyes will actually he small flat tvNew memory chips being de- tions of Electropalatography in with those produced by a speaker screens that the person will look veloped by various US companies Reading. with a speech disorder, the clini- at rather than look through. could largely supersede eproms. The symposium reviewed the cianisable to pin -point the What's even more ingenious That's the view of some experts work of 28 speech therapists and nature of the errors more pre- than the display system is thewatching the emergence of ex- experimental phoneticians who cisely than by using traditional camera system to pick up imagesperimental memories based on use a technique called electropa- procedures. The extra precision of the outside world. Obviouslythe ferroelectric effect. This is a no normal person would want to latography (EPC), whereby an in diagnosis means that the clini- property whereby certain crys- artifical palate with 62 electrodes walk around with a standard tvtalline materials such as lead cian can now not only plan more camera mounted on a hat. and so is placed in the mouth and the efficient therapy but can also zirconate titanate become pola- contact of the tongue with the a method had to he devised ofrized when subject to an often gain valuable pointers as to matrix of electrodes is recorded the underlying cause of the dis- disguising this inevitably bulkyexternally -appliedfield.This item. The answer researchers on a personal computer and dis- order. polarization is non-volatile, but played on the screen. The EPG have come up with is to use tiny can be reversed by the applica- lenses and bundles of optical system gives access to detailed tion of a field of opposite polarity. and previously unobtainable in- fibres embedded in each In practice, ferroelectric mate- Computer the spectacle frame where the formation about tongue position rials behave rather like bistable on the roof of the mouth. front and ear pieces join. Light is biology? capacitors with zero leakage. The In speech therapy. a patient's then conveyed along the fibres to only problems in developing a abnormal pattern of tongue con- Further evidence that today's se- a c.c.d. camera in a pack worn on practical application for such tact can be displayed alongside a quential von Neumann compu- the hip or shoulder. seemingly ideal materials has ter architecture may be on the NASA's existing black -and - model pattern which the therap- been the slow 'write' speed and way out comes from the relative- white version designed for re- ist has produced using a separate the rather indefinite polarization EPG palate. This visual feedback lyrecent re-emergence of in- mote handling applications inthreshold. space will form the basis of the therapy technique has been terestinneural networks - Research into new and as -yet found to be particularly effective attempts to model electronically new vision aid. But before it can secret materials is now coming for children with developmental the behaviour of neurons, or he of practical use for handicap- up with some highly promising speech disorders, for those with nerve cells in the brain. Part of ped people on Earth the system prototype rams offering high cleft palate, and for stroke pa- the aim is to try and gain insight will have to be converted to full read/write speeds and non - tients who have been left with into how the human 'computer'. colour and also made capable of a volatility. Raintron Corporation, speech problems. based on an incredibly slow logic degree of video processing. one of the companies concerned, An improved version of the The team emphasizes that the element. can outperform predicts that data stored in some EPC has resulted from progress machines at so many complex portable vision aidisnotin- of its chips will remain uncor- made recently by a team com- tasks. In fact. the more complex tended to restore totally lost vi- rupted for 100 years or more. prising researchers from the IBM sion nor to correct the many the task. the greater the brain's As well as developing new UK scientific centre in Winches- advantage. Try getting a optical defects that are more -or - materials, one of the important ter and from the department of machine to recognize someone it less adequately dealt with bygoals of research into ferroelec- linguistic science at Reading hasn't seen for 20 years! spectacles. The main function istric rams has involved finding University. One of the fascinating aspects to provide an increase in sensi-ways of integrating such mate- tivity for those who are almostrials into the memory circuits ofWrong (left) and right: visual feedback from tongue and palate. blind.It's therefore a sort ofexisting technology. Here differ- picture amplifier. ent researchers adopt different Dr Robert Masoff. a researcher approaches, some favouring at the Johns Hopkins Wilmer Eye direct substitution of conven- Institute says the new device tional capacitor elements, others should he able to help an esti- use the ferroelectric material as a mated 2.5 million people in the 'power -down' memory backup. MIL USA alone.It won't however. Either way, it looks as if it's

only help those who have lowjust a matter of time before chips

visual sensitivity. Because of the appear on the market that are video processing capability.it much faster than today's eproms will be possible to enhance con-and which can tolerate many trast or to accentuate edgemore write cycles before they OOOOO

ELECTRONICS & WIRELESS WORLD RESEARCHNOTES

of neural networks is their un- should point out that for accu-hope to develop mathematical predictability. Based as they Enter the rate results the probe needs to be models to predict in detail the usually are on thousands of in- electronic provided with a coaxial blast of processes of melting and vapor- terlinked processors, they aren't dry air - a bit like a miniature ization that take place. Prior to always susceptible to being dentist MIG welder. Without that essen- the construction of their 140 ton analysed by conventional Bool- tial item the results are likely to Van de Graaff machine. which ean algebra. In fact neural net-An unexpected and unwelcome send you rushing off premature- has an energy level of 8MeV, the works - liketheir biologicalvisitto the dentist recently ly to the nearest false teeth sup- basic data was simply not avail- counterparts - are self -prompted me to take a closer pliers! able. programmed to the extent that look at what seemed at first sight Although there is obviously a they can sometimes learn new to be an excellent d.i.y. method military interest in how to 'har- and unsuspected tricks. All oneof spotting rotten teeth. Smashing spaceden' spacecraft against the has to do, it seems, is teach the Studies at three U.K. dental effects of natural micro - machine by its own mistakes. colleges (Br. Dent. J. vol 164 No particles meteorites, this latest work is A recent example of this 8) have shown that simple resist- Physicists atthe Los Alamosdefinitely not the beginning of a approach was an attempt by re-ance measurements can spot National Laboratory have used anew type of beam weapon. Parti- searchers at MIT and the Uni- early caries in 85% of cases. Van de Graaff generator tocles travelling at 10'm/s can sur- versity of California to build a Research over 30 years ago accelerate particles of iron vive only in the vacuum of space. neural network capable of im- showed that, when dried with a 10-hm in diameter up to veloci- And as far as the prospect of itating the brain's ability to lo-blast of air. a sound tooth ex- ties of 105m/s, a hundred timesputting a particle accelerator in cate objects in space. The net- hibits a tip -to -gum resistance of faster than a high -velocity bullet. orbit, the Los Alamos team ques- work consisted of three layers ofgreater than 600kf 1. Under simi- The ideaisto simulate whattion the desirability of launching processors, one to accept inputlar conditions. a tooth with pits happens when a spacecraft is hit a 140 ton gun that fires nothing data. an uncommitted middleor fissures is likely to read less by showers of micrometeorites. hilt d putt layer and an output layer to than 2501(11. But because lots of When we think of collision assemble the answers. Input data well -established methods ofdamage, most of us think more consisted of electronic analogues spotting dental caries already ex- naturally of cars, aeroplanes or Bog standard of eye position and visual field ist,the plug-in approach has perhaps missiles. But outin and. initially, the network was never really caught on. space these macro -scale collis- In this enlightened age of sexual 'told' what it was looking at. i.e. Thereis.moreover. areal sions aren't always the best mod- equality there are some things what 'answer' to expect. Afterproblem with it: electronic tes- els, nor are they necessarily athat obstinately refuse to be about 1000 trial runs, the net- ters have often given low read- good basis from which to ex- equalized. A statisticalsurvey work had 'learned' to recognize ings on teeth that appear perfect- trapolate. Free from atmospher- undertaken by the Engineering and locate some remarkablyly sound. In fact three out of ic drag, space dust can reach Department at Cornell Universi- complex shapes. every four teethfallinto this truly enormous velocities.ty has revealed an important Another intriguing aspect ofcategory. A dentistcan't just accelerated by the gravitational discrepancy between the relative these neural networks is theirstart drilling and filling every and electrical fields of the solar time men and women spend in theoretical basis. tooth that appears normal but system. their respective 'rest rooms'. Re- As I mentioned earlier. they measures less than 250ki1. Any 0 -level physics student searcher Anh Tran. who lurked don't readily yield to convention- What this latest study did was knows that, in terms of damage for hours with a stopwatch out- al mathematical analysis. Their to apply the technique prospec- caused, the size and velocity of a side motorway loos in Washing- properties do, however, showtively to patients due to have projectile are in no way equiva-ton State, says that men, on striking similarities to those ofapparently sound teeth extracted lent. If you double the size of a average, take 45 seconds (stan- the materials that comprise for cosmetic reasons. Fifty teeth colliding particle then it has dou- dard deviation 3.73) to use the biological brains. And just aswere measured in vivo and also ble the inertia and causes rough- facilities while women take 79s bulk properties of matter such as inspected in the normal way. ly double the damage. On the (s.d. 4.47). A university spokes- temperature or pressure can be After extraction the same teeth other hand if you double theman described this as 'signifi- deduced from molecular be-were sliced up and subject to velocity of a given object it has cant'. haviour. the behaviour of neural detailed microscopic examina- the potential to inflict four times Tran has developed a simple networks can sometimes be de- tion. the damage. So even a particlecomputer program to make it duced from the way the indi- Result? Six were bad accord- the size of fine smoke can be easier for architects and desig- vidual constituent processors in- ing to the dentists, 28 according lethalifit'stravellingfast ners to calculate the most teract. to the electronics and 37 in enough. appropriate ratio of male and If allthis seems a flight ofactual fact. The electronic tech- But in devising their latest female excretory facilities in any journalistic neuronal fancy, con- nique therefore appears much experiments to accelerate given area. The program runs on sider one of the more advancedmore likely to spot early decay smoke -sized particles of iron, the an Apple Macintosh and needs to developments inthe USA. a than standard dental techniques. Los Alamos team were well aware be supplied with only the bare 'biological' computer at It also generates relatively few that you can't just use 0 -level minimum of data. Carnegie-Mellon University. Not false positives. But as the authors equations to extrapolate to the One immediate conclusion is only does it outperform sequen-point out.this doesn't mean conditions found in space. A one - the need, in most situations, to tial processors at a variety of dentists are doing a bad job. Not micron -sized particle travelling alter the generally -accepted tasks, its behaviour can to some many of the electronically identi- at lIrm/s will, for example, vapo-50:50 ratio to something nearer extent be predicted by the princi- fied cases of decay would yet be rize a target up to 1000 times its60:40 in favour of the ladies. Roll ples of thermodynamics! Tomor- ready for filling. Nevertheless the own weight. So it's scarcely just on the paperless office. row's programmers,itseems. now -validated technique offers an extension of what happens will have to forget all they ever great potential for catching early every day on the M25! Research Notes is written by learned of high-level languagesdecay and treatingitin other By observing exactly what John Wilson of the BBC External and take a few lessons in biophy- ways. But before you start trying does happen under these ex-Services science unit at Bush sics. to eat a set of Avo probes,I treme conditions, the physicists House. London.

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ELECTRONICS & WIRELESS WORLD 931 -TELEVISIONBROADCAST

flew deregulated, competingcommissioned in September Their coder consists of a two - A licence to lose advertisement and sponsor 1987. cracks were found in two hand quadrature mirror filter money? funded channels flew in the face bracing rods. After furtherhank incorporating backward of American experience - and cracks were detected, the deci- adaptive prediction and quan- Among all the media hype sur- was a sure way to lower the sion was taken to replace all 113(1 tization in each sub -hand. The rounding d.h.s. from Astra and quality of British television. rods. It was during this work that audio signals are sampled at the BSB satellite.itis easy to More choice does not necessarily a sudden slippage of the chain 32kIlz and each 16 -hit sample is forget the extent to which, only a mean worse "free" programmes winch used to provide temporary filteredinto two frequency few years ago. we were all being - but I would not bet on that! bracing caused the mast to twist bands, coded to four bits for similarly persuaded of the won- The efforts over the past de- and begin to collapse. Two of the transmission. Work isalso in ders and imminent coming of cade of Australian andriggers were crushed beneath progress to implement this the wired city with its widehandAustralian -born media moguls the top 464m section of mast as it music coder in real time. It has interactive electronic grid. There to move into UK commercial fellto the ground. becoming already been shown that a full were endless articles and pro- broadcasting have been paral- embedded to a depth of up to 5m. duplex implementation is possi- grammes about Warner's QUBE leled by their efforts to provide The third man jumped to his ble on a single 1(10 nanosecond system. Far fewer marked its services in the Pacific islands. death from the work -basket. fixed-point d.s.p. demise after a few years when The Niugini Television Network A detailed report in New Civil The authors claim that their Warner found they could not in Papua. New Guinea, set up by Engineer (June 9)by Simon results clearly demonstrate the provide enough popular prog- the Parry Corporation at a cost ofMontagu notes that "thefre- very high coding efficiency of ramming. while subscribers $A 9M closed down after four quent collapse of US masts dur- sub -hand a.d.p.c.m. when com- found the control pad too com- months as a non -viable opera- ing maintenance or because ofpared with digitally companded plex and did not take kindly to tion. The Packer Group, taken icing has in the past failed toand a.d.m. schemes applied to the pay -per -view concept rather over by Alan Bond. won the right raise the self-governing associa- high-fidelity music. They write: than the monthly subscription to set up a service in Fiji in the tion EIA to action". He forecasts "We believe these findings are basis of most American cable face of stiff competition. This was that lessons from the collapse ofvery significant and represent a networks. Furthermore the due to start late last year but was the KTVO mast seem unlikely to major advance in digital audio scrambling-descrambling sys- cancelled following the military be passed on to the US engineer- technology, having immediate tem degraded the picture quality coup on the island. Now TV New ing fraternity. implications for ISDN. broad- to a noticeable degree. Zealand is anxious to establish a casting and d.h.s. digital audio Similarly, the INDAX system Pacific regional service centred distribution...In addition run by Cox Cable in San Diego. on Fiji. but finds that the Bond a.d.p.c.m. is known to offer bit offering banking. shopping and Group retains exclusive rights Four -bit digital error immunity down to 1 in 10' pay -per -view facilities, was un- for twelve years. audio without any form of protection able to convince many viewers or concealment. four orfive that its programmes justified the With linear p.c.m. coding.14 orders of magnitude better than expensive converter boxes. US mast hits with 32kHz sampling of a most p.c.m.-based systems ... we Nevertheless. less ambitious 15kI1z audio channel results in a seriously question the con- forms of interactive cable are tragedy hit -rate of 448khit/s. Withtinuing viability of p.c.m. as a again expandinginthe USA. d.p.c.m. coding this reduces to reliable and economic means of most of the "return" paths usingFailures of very high television 256kbit/s. Delta modulation withstoring or transmitting high - the normal telephone network ormasts are fortunatelyrarein adaptive pre -emphasis brings the quality digital audio". working on a store -and -forwardEurope and when they have rate down to 203khit/s. In prac- The Electronics Letters report basis rather than instantaneousoccurred have usually not re- tice the CD stereo data rate isincludes details of subjective service. Some 16 million homessulted in casualties. The Amer- about 1.4Mb/s. Nicam compand- listening tests which appear to were connected to such systemsican experience seems less ing to 10 hits provides a stereo show that music recovered from at the beginning of the year. hut happy. hit -rate of 728kbit/s. As noted in the four -bit coding is essentially the full potential of the electro- Early in June a tragic accident the February "Radio Broadcast" indistinguishable from the ori- nic grid seems as far away as brought down the new 610 metre column. the Thomson Group has ginal material.It would be in- ever. Even the efforts of Amer-triangular lattice mast of KTVO. developed in Germany a form of terestingto see independent ican cable companies to provideKirksville. north-east Missouri. adaptive transform coding pro- tests carried out,preferably data links for urban businessresulting in the death of three viding astereo datarateof based on the EBU test record (see users have so far failed to pro-erectors who were fitting new 256kbit/s. "Radio Broadcast". page 9361 on duce the predicted revenues. bracing rods at a height of 146m. S.M.F. Smyth and J.V. McCan- both the Thomson 256kbit/s The success of any television The o£1.1M mast. one of a ny of Queen's University, Belfast stereo system and this latest con- channel or video system dependsnumber of American television are making strong claims (Elec- tender. While the lower bit rates in the long term on providingmasts reaching the maximum tronics Letters, 14 April, 493-5) would be attractivefor audio programmes capable of attract-height permitted by the FCC. for four -bit a.d.p.c.m. coding tocontribution and distribution ing and satisfying large numberswas comparatively lightly give a bit rate of 128kbit/s for a networks, one wonders what the of viewers as well as being re-loaded. It carried two circularly - 15kHz channel directly applic- reaction would he to any sugges- latively cheap and easy to use.polarized antennas for the able to the European ISDN tele- tion at this late stage of changing Provided that it is easy to oper-100kW transmitters, some mic- communications hierarchy. existing standards for d.h.s. or ate, technology appears to playrowave dishes and an f.m. radio They claim the results they have terrestrial broadcasting! Already only a minor role. The Govern-antenna.Itserved viewers in achieved are of major import- the Nicam 728 system is under ment's suggestion (since with-parts of Missouri. Illinois andance not only for ISDN and threat from Rupert Murdoch's drawn) of changing BBC2 and Iowa. Services were restored on broadcasting, but also for other PAL plans for his Astra channels. Channel Four Television intothe earlier, lower mast which digital audio technology includ- satellite subscription services, had not yet been dismantled. ing CD records and digital audio Television Broadcast is written while filling terrestrial channels Soon after the new mast was tape. by Pat Hawker.

932 ELECTRONICS & WIRELESS WORLD KESTREL R.F. COMPONENTS AND ELECTRONIC ELECTRONIC VALVES/TUBES COMPONENTS LTD. PRODUCT RANGE CRT's R.F. RESISTORS All items guaranteed to manufacturers spec. CAMERA TUBES R.F. SCREENED Many other items available. CHOKES CONNECTORS 'Exclusive of V.A.T. and post and package' CARBON RESISTORS R.F. RESISTORS (MRF. SD, 2N, 2C etc) s 50+ 1+ 50t DIODES HEATSINKS R.F. INDUCTION/ 74LS125 0 15 0.12 8 Meg 0 45 0.35 DIELECTRIC SPARES 0.45 0.35 IGNITRONS 74LS244 0.30 0.21 16 Meg RECEIVING TUBES 74LS245 0.30 0.21 IL0-74 1.50 1.35 IMAGE INTENSIFIERS RECTIFIERS 74LS373 0.30 0.21 1488 0 25 0.16 INTEGRATED CCTS SPARK GAPS 6809 2.50 2.20 1489 0.25 0.16 (Linear. Audio) LM2901 0.80 0.60 TETRODES 6821 1.25 0.95 KLYSTRONS 6845 2.50 2.20 LM2917-8 1 50 0.75 THYRATRONS 6850 1.60 1.40 2732-A 2.50 2.30 MAGNETRONS TRANSISTORS 6502 2.80 2.40 2764A-25 2.20 2.00 MICROWAVE TUBES TRANSMITTING TUBES 6522P 2.80 1.85 27C64-20 3.00 2.60 PHOTOMULTIPLIER TUBESTRAVELLING WAVE TUBES 8031 2.80 1.70 27128-25 3 70 3.40 PLANAR TRIODES TRIODES 8085 1 60 0.95 27C128A-25 3.40 3.10 27128A 2.98 2.72 R.F. CAPACITORS TUBE SOCKETS 8255-5 1.90 1.30 VACUMM CAPACITORS LM319N 0.50 0 40 27256-25 3.30 3.12 R.F. CONNECTORS 32.768Khz Crystal 0.25 0.16 27C256-25 3.50 3.22 Mail order service available. Please specify which products 1.8432 MHz 0.95 0.70 43256C 12L 10.00 9.00 you are interested in when replying. 2.4576 MHz 0.75 0.65 ICL8211CPA 0.80 0.60 Export enquiries welcome. 3.5795 MHz 0.50 0.35 TL084CN 0 50 0.45 4 Meg 0.45 0.35 Z8OACPU 1 00 0.80 4 194304 0.45 0.35 Z8OACTC 1 00 0 80 RAEDEK 6 Meg 0.45 0 35 Z80AP10 1.00 0 80 All memory prices are fluctuating daily. please phone to ELECTRONICS CO. confirm prices. BANNERLEY ROAD. GARRETTS GREEN. 178 Brighton Road. BIRM NGHAM B33 OSL Purley. Surrey CR2 4HA Tel 021-784 8655. Telex: 333500 CROSAL G. Tel: 01-668 7522. Fax: 01-668 4190 Fax: 021-789 7128

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although RTL is not responsible sinking of the Belgrano in 1982 Coping with for investigating the possible Superconduct- showed, radio communication health hazards that could arise with submarines isstilloften e.m.c.? from defective door seals in old ing dipoles only intermittently successful. ovens. A.J. Meaden notes that com- An open day at the DTI's Kenley Theoretically, an electrically Immunity testing of televisionvery short dipole antenna ele- munication depends on either a Radio Technology Laboratories receivers and other appliances is ment could be as efficient as a buoyant antenna tower towed near Whyteleafe, Surrey, re-carried out with a large t.e.m. resonant half -wave element. In behind a deeply -submerged ves- vealed measurement facilities cell; although with no v.h.f. tele- practice, this cannot be achieved sel. with problems of manoeuv- capable of providing accuratevision in the UK, it seems odd since there are always high r.f. rability and recovery, or with a type -approval checks and meet- that this is suitable for a source mast -mounted antenna raised ing allcurrent and proposedonly up to 150MHz. A large ohmic losses in the element and matching network relative to the from the bridge -fin when the e.m.c. radiation and immunity environmental test chamber is radiation resistance, which falls vessel is at periscope depth. test needs. The facilities, now used for bulky equipment such well below 10 for an electrically Plessey has developed a new being offered on a commercial as marine m.f./h.f. transmitters. integrated communications basis to industry for the pre- very short element. Clearly, a Case radiation from transceiversshort element and associatedmast. MoD designation MU, testing of equipment, are seen as can be measured down to a nano - matching lines without measur-whichisfree -flooded and of an essential requirement when watt to 4GHz by substitution able r.f. ohmic resistance would glass -reinforced -plastics con- the European Community EMC methods using a large corner struction. Unlike earlier designs. Directiveisfinally approved. greatly improve the efficiency. reflector to minimize the effects A team at the University of it does not penetrate the hull and (The draft is still being revised of wall reflections etc. Receiver has a faired profile that overcom- and it now looks unlikely that the Birmingham supported by ICI oscillator radiation from mobile technologists has reportedes lateral vibration due to shed- Council's common position can and c.b.transceivers can be achieving a gain at 550MHz ofding of Karmon vortices. It can be reached until at least Septem- checked over the range 100kHz 10.56dB (as against a compara- carry m.f., h.f.. v.h.f.. u.h.f. and ber.) UK legislation will also be to 2Gliz to determine that this ble copper wire dipole) by using satellite navigation and satellite necessary if certain British Stan- does not exceed 2nW below communication antennas. Two - dards are to become enforceable. one of the new "rare earth" 1GHz (20nW above I GHz). superconducting ceramics: band radar -absorbent material While Kenley is ready, the DTI Kenley is also the base for the tuned to anticipated "enemy" has been one of the principal (Electronics Letters.14 April, new Radio Investigation Service 1988, 460-1). frequencies has resulted from objectors to some clauses of the mobile laboratory, covering collaboration with Plessey Mic- draft Directive. arguing inter alia At room temperature the 9kHz to 40GHz and fitted with radiation resistance of the test rowave Materials, Towcester. that it cannot be enforced on alltwo pneumatic masts. one of The u.h.f./D.-band antenna com- apparatus inthe absence of antenna was 0.2611 and the loss which can extend up to 28m. resistance 3.512. When the cop- prises a conical log spiral design national standards. Thereisa quiet -running on- at the top of the mast with a Yet as one of the Kenley de- per element was reduced to the board 3.5kW generator. Used to temperature of liquid nitrogen.broadband dipole forline -of - monstrations showed clearly, back-up the RIS field teams, par- sight. low -angle radiation along home computers currently on without of course superconduct- ticularly for the investigation of ing, a gain of 6dB was achieved. the axis of the cone. An h.f. whip the UK market are failing by a industrial and radar interfer- antenna extends above the mast wide margin to meet the stillence, it surely represents good \ \lien rk.viirctl unenforceable BS6527:1984 cov- value at the standard RIS rate of ering radiation from information141 per engineer per hour. Rising above technology equipment. A popu- Essentially, Kenley remains a the waves RSGB's 75th lar computer was shown produc- precision measurement labora- ing 40dB(µV) radiation at tory rather than an e.m.c. design Although e.l.f. waves can pene- anniversary 128MHz. 10dB above the BS6527 advice centre. But what may be trate to a considerable depth limit, measured under the speci- needed most by small electrical under the surface of the sea, they By the time these notes appear. fied conditions. and electronic appliance makers, provide only a one-way radio linkthe 75th anniversary of the RTL's facilities, covering 9kHz when finally the EMC Directivewith submarines and then onlyfounding by four pre -first world to 22GHz, lean heavily on Hew- and new UK legislation come at an extremely low data rate. For war experimental amateurs of lett Packard and Rohde & into force. will be expert advice at two-way communications, sub-the Wireless Society of London Schwarz spectrum analysers and an early design stage. The open marines still depend on raising(it became the Radio Society of measuring receivers. Chase day left one wondering whether an antenna above the waves. Yet. Great Britain in November 1922) Electronics assisted with a de- Kenley is yet set up to meet this today, as A.J. Meaden points out will have been duly celebrated by monstration of V -network and requirement, which callsfor in PESL New Technology a series of events starting with a clamp techniques for measure-e.m.c. design specialists rather (Spring 1988): "The strategic im-three-day convention at NEC in ment of cable -conducted emis- than precision instruments. portance now assumed byBirmingham, opened by the sions, showing clearly the wide DTI has recently introduced nuclear -powered submarines.society's patron, Prince Philip, spectrum of emissions from a new type -approval testing proce- particularly of the ballisticDuke of Edinburgh. This year. switch -mode power supply. Ples- dures for land -mobile radio missile -armed type, has placed even the society's annual general sey Assessment Services collabo- equipment. Type approval test- them in a role where an indi-meeting, until now always held rated in a demonstration of elec- ing of MPT1300 series specifica- vidual vessel can have interna- in London. may depart the capit- trostatic discharge testingin tions can also be carried out by tional impact undreamt of at theal - perhaps a sign that the accordance with BS5967 Pt 5. ERA Technology at Leatherhead; end of the second world war. Itamateur radio movement, with Fundamental and harmonic Plessey Technology Services at follows that the ability to com- its need to regain the interest of radiation from microwave ovens Fareham: and RFI Ltd at Basing- municate with these submarines the younger generations, is find- (potentially a source of interfer- stoke. DTIisintroducingat virtually any moment during ingitincreasingly difficult to ence to 12GHz d.b.s. reception) charges for all type approval test- the day or night is completely decide where its future lies. is measured in a reverberation ing at Kenley at rates subject to essential to their operation." Radio Communications is writ- chamber with rotating vane, contract. As the events surrounding the ten by Pat Hawker.

934 ELECTRONICS& WIRELESS WORLD oveES PRINTERS %0E0 & MONITORS 1000'S OF RELAYS akt. RACKS SURPLUS ELEC1RENt9 COMPUTER SDPID0WER OfSIHI DISK BOUGHT VDU'S IT EMS psrEms mOIORSt iN PL/Es DRR ouiPtEnr-TIS CA8INEIS & DO0LE-cf.c'S BS VER & ECOP*AE KE YeIV SES & SOLD & PLOTTERS STOCK STEPPERS TORS & F ANS OSS IN &DAfa THE 'ALADDINS' CAVE OF ELECTRONIC &COMPUTER EQUIPMENT COLOUR MONITORS PRINTERS POWER SUPPLIES i.dda. un51,, Inxc or pi mien 1.11111411,4Th( All dowerpower supplies operate from 220-240 v AC Many other types from 16' Decca. 80 series budget range colour monitors features in 1,..ipenr: .111he r.crn diI MI South I ...don Shop dude PIL tube attractive teak style caseuaranteed 80 column 3v 10Kv in stock Contact sales office for more details resolution only seen on monitors costing times our once readyHAZELTINE ESPRINT Small desktop 100 cps print speed with bothPLESSEY PL12'2 Fully enclosed 12v DC 2 amp PSU Regulated and to connect to a host of computer or video outputs ManufacturersRS232 and CENTRONICS interfaces Full pin addressable graphicsprotected Dim cm 13 5 x 11 x 11 New £16.95 (B) fully tested surplus sold in little or hardly used condition with 90 dayand 6 user selecable type fonts Up to 9 5 single sheet and tractorAC -DC Linear PSU outputs of 5v 5 5a, 5v 0 6a 24v 5a Fully regu- full RIB guarantee 1000's Sold to date. paper Band lated anc short proof Dim cm 28 x 12 5 x 7 New £49.50(C) rTIFIONIR 150series A reel workhorse for cworCiltriYuou"s99uslv!iliPOWER ONE PHC 24v DC 2 amps Linear PSU fully regulated DECCA 80 RGB TTL SYNC input for BBC type interface etc DECCA 80 COMP 75 It composite video input with integral audiotractor feed paper, either in the office. home or factory desk standing, New £19.95 (B) amp & speaker ideal for use with video recorder or TEL ST or150 cps 4 type fonts and choice of interfaces Suppled BRAND NEWBOSHERT 13088 switch mode supply ideal disk drives or complete any other audio visual use Order as system 5v 6a 12 2 5a-12 0 5a. -5v 0 5a Dim cm 5 6 x 21 x 108 Only £99.00 (E) 150-SN up to 9 5 per handling £185.00 New £29.95 (B) 150 -SW up to 14 5 paper handling £225.00E BOSHERT 13090 same as above spec but outputs of 5v 6a. 24v HIGH DEFINITION COLOUR 150-GR up to 14 5 paper plus full graphics £245.00 E 15a 12v 05a 12v05a New E39.95 (B) When ordering please specify RS232 or CENTRCNICS interface GREENOALE 19ABOE 60 Watt switch mode outputs 5v 6 a 12v

RFE Tested E24.95 (B) BRAND NEW CENTRONIC 14' monitors in anractNe style moulded la12v ia 15v taD 11 x 20 x 55 case featuring hi res Mrtsubushi 0 42 dot pitch tube with 669 x 507 Ultra Fast 240 cps NEWBURY DATA CONVE9 AC130-3001 High grade VDE spec compact 130 watt pixels 28Mhz bandwidth Full 90 dly_guarantee switch mode PSU Outputs give 5v 15a, -5v la 8.12v 6a Dim 6 5 Order as1004-N2 for TTL sync RUB for BBC etc £150.00 (E NDR 8840 igh Speed Printers x 27 x 12 5 Current list price £190 Our price New £59.95.00 (C) 1003-N1 for IBM PC etc fully CGA equiv £189.00 E FARNELL G6 40A Compact 5v 40 amp switch mode fully enclosed Only £449 New 140.00(C)C 1005-N2 RGB interlace for OL 85 columns £169.00 E11 A special purchase from a now defunct Goverment Dept enables usFARNELL G24 5S Compact 24v 5 amp switch mode fully enclosed 20 " & 22" AV Specials to offer you this amazing British Made, quality punter at clearance New £95.00 (C) Superbly made, UK manufacture. PIL tobe. all solid state colourprices, SAVING YOU OVER E1500 II the NDR8840 features high Special Offer ONLY monitors complete with composite video and sound inputs. attrac-speed 240 cps print speed with integral, fully adjustable paper trac- tive teak style case. Ideal for a host of applications including Schools.tor giving exceptional fast paper handling for multi Dart forms etc The EXPERIMENTORS PSU £16.95 (c) Shops Disco's. Clubs etc Supplied in EXCELLENT little used con-unit -features 10 selectable type fonts giving up to 226 printable dition with 90 day guarantee characters on a single Nne. Many other features include internal Made to the highest spec for FIT this unit gives several fully 22 Monitor £185.00 (F) electronic vertical and horizontal tabs Self test. 9 needle head. Up to 20' Monitor £165.00 (F) 15 5 paper 15 milion character ribbon cartridge lie and standard protected DC outputs most suited to the Electronics Hobbyist. RS232 serial Interface Sold in SUPERB tested condition with 90 du 5v 2a. 8,12v la.- 24v la and 5v fullyfloating at 50ma MONOCHROME guarantee Ideal for school labs etc Quantity discount avalable Fully tested with data RFE Removed From Equipment MOTOROLA M1000-100 5' CRT black & white compact chassis model 512 40 column 3 5 wide roll?en.Z.Eh14.7.sPier monitor measuring only cm 11 6h .12w. 22d. ideal for CCTV or com-matrix (3 lines per second) printer mechanism for incorporation in puter applications Accepts standard Composite video or individualpoint of sale terminals. ticket printers, data loggers etcUnit features bi The AMAZING TELEBOX H & V syncs Operates from 12v DC at apprx 0 8a Some units maydirectional printhead and integral roll paper feed mech with tear bar Convert intp a have minor screen marks but stillin very usable conditionFull Requires DC volts and simple parallel external drive logic Complete QUALITYCOLOURnitorTELEVISION tested with 30 day guarantee & full data Only £29.00 (C)with data RFE and tested Only £49.95 (C) Fully cased as above with attractive moulded. desk standing swivelEPSON model 542 Same spec as above model. itit designed to beBrand new high quality fully cased. 7 channel UHF PAL TV tuner sys- and it case Dim cm 12h.14 5w.26d £39.00 (C)used as a slip or flatbed printer Ideal as label. card or ticket printertem Unit simply connects to your TV aerial socket and video morelor JVC type 751-7 5" ultra compact black & white chassis monitor forSupplied full y cased in attractive, small. desk top metal housing Com-turning same into a fabulous colour TV Dont worry if your monitor 12v 0 7a DC operation Dim cm 11h.14w.18d Simple DIY circuit dataplete with data RFE and tested Only £55.0) (0)doesn t have sound. the TELEBOX even has an integral audio amp for included to convert data and separate sync input to composite videoPHILJPS P2000 Heavy duty_25 COI bi directional daisy wheel printerdriving a speaker plus an auxillaryoutput for Headphones or Hi Fi sys- InputIdeal portable equipment etc. Supplied with full dataFully DIABLO, OUME, WORDSTAR compatible Many features In-tem etc Many other features LED Status indicator. Smart modeled Brand New £65.00 (B)clude full width platen - up to 15 paper. host of avalLable daisy wheels.case. Mains powered Boit to BS safety specs Many other uses for TV single sheet paper handling superb quality print Supplied complete KGM 324 9' Green Screen. Little used fully cased. mains powered sound or video etc Supplied BRAND NEW with fill 1 year guarantee high res monitors with standard composite video input Futy testedwith user manual & 93 day guarantee plus FREE dust cover & dais_yCarriage code (B) and in excellent condition £49.00 (E)wheel BRAND NEW Only £225.00 (E) 20' Black & White monitors by AZTEK, COTRON & NATIONAL All solid state. fully cased monitors. ideal for at types of AV of CCTV Most of the items in this Advert. plus a whole range of other TV SOUND applications.Units have standard composite video inputs with in- electronic components and goodies can be seen or purchased & VIDE°, tegral audio amp and speaker Sold in good. used condition- fully Only £85.00 (1) at our TUNER tested with 90 day guarantee ONLY FLOPPY DRIVE SCOOP ** South London Shop ** £29.95 Drives from Only £39.95 Located at 215 Whitehorse Lane, London SE25. The shop is TELEBOX ST for monitors with composite video input £29.95 on the main 68 bus route and only a few miles from the main TELEBOX STL as ST- but fitted with integral speaker £34.95 A MASSIVE purchase of standard 525 disk drives enables us to A23 and South Circular roads Open Monday to Saturday from TELEBOX RGB for use with analogue RGB monitors £59.95 offe you prime product at all time super low prices All units unless 9 to 5.30parking is unlimited and browsers are most wel- stated are removed from often BRAND NEW equipment. fully come. Shop callers also save the cost of carnage (RI ffr i11,1,00 lo.11151.I 11151 tested and shipped to you with a full 120 day guarantee. AJI units moniti.I) \ I\ rcrikr,1 \I I 1011,1 .\ 1 1

offered operate from 5 and 12 volts DC. are of standard size and accept the common standard 34 way interface connector TANDON TM100-2A IBM compatible 40 track FH double sided MODEMS RECHARGEABLE COOLING FANS Iscep hot 1,1..111111 .tna RI II \ 141 Istar, Only £39.95 (B) \ TANDON TM101-4 FH 80 track double sided Only £49.95 (B)Moderns to suit all applications and budgets BATTERIES r of 1112.5511 *s. I JAPANESE Half Height double sided drives by Canon, Tec. Please contact our technical sales staffif you AC FANSn Specfv 240 or 110 v Toshiba etc. Specify 40 or 80 track Only £75.00 (B)require more information or assistance Maintenance free sealed longite LEAD ACID3 Fandim 80x 80x39 £8.50 TEAC FD55-F 40-80 track double sided Hail Height A300 12v 3 Ah f 13.95 3.5 ETRI slimline 92 x 92 x 25 £9.95 B Brand New £115.00 (B) SPECIAL PURCHASE A300 6v 3 Ah 4' Fan Dim 120x 120 x38 £9.95 B V22 1200 baud MODEMS A300 6-0-6 v 1 8 Ah RFE £5.99£9.95 AA As above - TESTED RFE Only £4.95 DISK DRIVE ACCESSORIES ONLY £149 Ii NICKEL CADMIUM 10' round x Rotron 10v £10.95 B 34 Way interface cable and connector skigle E5.50, Dual £8.50 (A) Quality 12 v 4 Ah cellpecA Originally madeDC FANS 5 25 DC power cable £1.75. Fully cased PSU for 2 x 5 25 Drives MASTER SYSTEMS type 212 mlcroproces-for the TECHNICOLOUR video companyPapst Miniature DC tans 62.62x25 mm £19.50 (A) Chassis PSU for 2 x a drives £39.95 (B) sor controlled V22 lull duplex 1200 baud. Thisthis unit contains 10 high quality GE raced, DOrder 812 6-12v or 814 24v £15.95 A fuNy BT approved modem employs all the latesttype cells, configured ina smart robust4" 12v DC 12w120x 120x38 £12.50 B 811 DISK DRIVES features for error free data comms at the stag-moulded case with DC output connector Dim4" 24v DC flw 120x 120 x25 £14.50 B SUGART 800.801 single sided refurbished £175.00 E) genng speed of 120 characters per secord,cm 19 5 x 4 5 x 12 5 Ideal portable equipment°UHLER 12v DC 62 mm £12.95 A SUGART 851 double sided refurbished £2e0.00 E) saving you 75% of your BT phone bills andetc BRAND NEW £24.95 (B) MITSUBISHI M2894-63 Double sided switchade Hard or Sort sec data connect time II Add these facts to our12v 17 Ah Ultra rugged all weather. virtually tor BRAND NEW £275.00 (E) give away price and you have a superb buy "indestructable refillable IIICAD stack by SPECIAL OFFER Dual 8 drives with 2mb capacity in smart case Ultra slim unit measures only 45 mm high withALCAD. Unit features 10 x individual type'SPECIAL INTEREST' with integral PSU ONLY £499.00 (F) many integral features such as Auto answer.XL 1.5 cells in wooden crate Supplied to the Full LED status indication. RS232 interfaceMOD and made to deliver exceptionally high Please call for availability or further into Remote error diagnostics. SYNC or ASYNCoutput currents & withstand long periods ofRACAL-REDAC real time. colour drafting COMPUTER SYSTEMS use. SPEECH or DATA switching., integralstorage in discharged state Dim cm 61 x 14 xPCB layout system £3950 TATUNG PC2000. Big brother of the famous EINSTEIN themains PSU. 2 wire connection to HT line etc22 Cost over E250 Supplied unused & testedDEC VAX11750 inc 2 Mb Ram DZ and full TPC2000 professional 3 piece system comprises Quality high resSupplied fuly tested. EXCELLENT slightly usedcomplete with instructions £95.00 (E1doc etc Brand New £8500 GREEN 12 monitor Sculptured 92 key keyboard and plinth unit con-condition with data and full 120 day guaranteeEX EQUIPMENT NICAD cells by GEHP7580A 8 pen digital Al drum plotter with tairerg the Z8OA CPU and all control electronics PLUS 2 integral Removed from equOmerft and believedin LIMITED IEEE interface As New £4750 TEAC 5.25 80 track double sided disk drives. Many other features (D) good but used condition. 'F' size 7th 6 forCHEETAH Telex machine £995 include Dual 8. IBM format disk drive support.Serial and parallel QUANTITY Only £149 £8 (B) Also D' size 4Ah 4 for £5 (B) 1.5 kw 115v 60 Hz i)ower source £950 outputs full expansion port 64k ram and ready to run software Su 500 watt INVERTER 24v DC to 240v AC sine M. WORDSTAR, BASIC and accounts pack -CONCORD V22 1200 baud as new £330.00(E) compRAleteNDwith CONCORD V22 1 200 2400 BIS £399.00 (E) wave 50 Hz output £275 age Bied NEW SOLDER SYSTEMS tin lead roller tinning Full 90 day guarantee RIXON Ex BT Modem 27 V22 1200 £225.00 (E) Dil3sFIAVieNsEfft451a.. machine for PCB manufacture DATEL 4800 RACAL MPS 4803 EX BT 310 Original price OVER £1400 Only £299(E) End of line purchase enables this brand newCALLAN DATA SYSTEMS multi user INTEL modem for 4800 baud sync use £295.00 (E) based UNIX system complete with software EQUINOX (IMS) 5100 system capable of running either TURBO or unit to be offered at an all tfrne super low price DATEL 2412 2780/3780 4 wee modem unit and 40 Mb winchester disk drive £2750 standard CPM Unit features heavy duty box containing a powerful £199.00 (E)The NEC D2246 6' 80 Mb disk drive features PSU. 12 slot S100 backplane. & dual 8 double sided disk drivesEX BT fuNy tested full CPU control and industry standard SMDWAYNE KERR RA200 Audio. real time fie- MODEM 20-1 75.1200 BAUD for use with interface, Ultra high speed data transfer andguency response analyzer £3000 Two individual Z80 cpu boards with 192k of RAM allow the use of £49.00 (E) multi user software with upto 4 RS232 serial interfaces Many otherPRESTEL etc EX BT fully tested access times leave the good old ST506 inter-TEKTRONIX 1411.'R PAL TV test signal features indude battery backed real time dock. al IC's socketed etcTRANSDATA 307A 300 baud acoustic face standing Supplied BRAND NEW withstandard E6900 Units in good condition and tested prior despatch. no documentationwith RS232 1'0 Brand New £49. (Elfull manual Only £399.00 (ElTEKTRONIX R140 NTSC TV testsignal RS232 DATA CABLES 16 ft long 25w D dug toDual drive. plug in 135 Mb sub system for IBMstandard £875 at present hence price of only £245.00(F) HP 3271A Correlate system S100 PCB's IMS A465 64K dynamic RAM £55.00 (BUMS A930 FDC25 way D socket Brand New Only f9.95 AI AT unit In case with PSU etc £1499.00 (F) £350 controller £85.00 (B). IMS A862 CPU & Uo £66.00 (B) As above but 2 metres long f 4 99 A)Interface cards for upto 4 dives on IBM ATPLESSEY portable Microwave speech / data f2.95 A)etc available Braid new at £395.00link12v DC 70 mle rangeThe pee £275.00 SAE for lull list of other S100 boards and accessories BT plug & cable for new type socket 17' Rack cabinets 100's in stock trom £15.00

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hama. who for some years has A.m. stereo: meaningfully. The EBU recordelectromagnetic elements (IEEE been endeavouring to set up ancontains sequences selected toTrans. on Consumer Electro- what went internationalh.f.service withreveal a variety of defects. Thenics. May 1988. 298-301). He a.m.-stereo. has now proposed to recording was made directly in dismisses the solution of electro- wrong? the FCC that clear -channel fre- digital form using a Sonynic memory because of the diffi- quencies in the extended m.f. PCM1630 coder and V05080 U- Robert Streeter. who developed culties of congestion of the hand he allotted to his company miak.. recorder. memory. its connections to the the Magnavox medium -wave for the establishment of a "super- stereo system, has commented reading device and the prohibi- power. a.m.-stereo. national tive costs of manufacture. His in IEEE Spectrum (June 1988) direct broadcast service" cover- proposed solution adopts the on the reports that a.m. stereo in ing continental USA. Alaska and the USA is in the doldrums, with CD life span? principle of analogue modula- Hawaii. Traditionally, the FCC tion, after conversion to digital little interest being shown by the has always limited transmitter Ithas been the claim of the vast majority of listeners ("Radio form, photographically recorded ownership so thatthe mainrecording industry that CD re-as a matrix on a square or rec- broadcast". July 1988). The Mag- domestic radio networks arecords not only provide near- tangular film or transparency. navox AM -OM system was initial- built around chains of "affiliate"immaculate sound quality hut. He recognizes that the prac- ly selected by the FCC in 1980 as stations. Power has been limited. having no physical contact with the American standard: hut. fol- tical implementation of such a even for the so-called "clearthe laser. will last indefinitelysystem for more than a few lowing strong opposition from channels", toa maximum ofwithout degradation. However. seconds of audio signals depends the other contenders, the ruling 50kW. The ambitious Global there have been rumours that aon reducing the size of the pic- was withdrawn and in 1982 it was plan calls for chains of synchro- few optical discs have appearedture element (pixel) from the announced that the choice nized transmitters at powers up to degrade rapidly, due to whatfraction of a millimetre possible would heleftto the market- to one megawatt. Programmes has been called "laser rot"- atoday to only a few microns. He place. would he to a news and informa- misleading term, since the prob-comments: "This would seem Streeter writes:"Ifallin- tion format, funded by advertis- lem seems to arise from exposureutopian today. hut tomorrow...?" terested parties had settled down ing.Itremains to be seen of the aluminium layer to the air to producing an a.m. stereo sys- whether FCC will respondas a result of defective applica- tem in 1980. then a.m. broad- favourably to Global's proposals tion of the protective lacquer. Solar radio casting would have had a much fora first "national" channel. A more serious allegation was better chance to he equal to f.m. sprung on the publicin The set -back stereo in the ears of the listening Guardian (June 29) suggesting public beforeitsfallto near EBU CD test that a significant proportion ofLack of help from specialized oblivion." existing discs can be expected toplastics firms, which are often He contends that none of the record fail in eight to ten years time as aassociated with battery manufac- a.m. stereo systems authorized result of contamination of the turers, is blamed by UNESCO for by the FCC in 1982 is flawless but For many years both SMPTE and lacquer by the ink used to print the problems experienced in de- that the same could he said of EBU have produced sets of col- the "labels", leading to pin holesveloping a low-cost radio receiv- NTSC colour television or f.m. our slides carefully selected to and consequent oxidation of theer powered from the sun and pilot -tone stereo - "Yet these provide very critical tests of tele- aluminium surface. Sony andsuitable for manufacture and other systems have served the vision systems. Such slides play- Philips. who receive royalties onsale in Third World countries. consumer well and have made a ed an important role in the com- all CD records, insist that noThe UK withdrew from UNESCO great deal of money for manufac- parison of colour encoding tech- problems are likely to arise within 1985. turers ... There are ways to hide niques and later in devising the records made correctly to the UNESCO has spent about the flaws in each of the a.m. digital standards. agreed specification. While there$25 000 in developing the pro- stereo systems sufficientlyto The EBU's ad hoc Group V3/ is clearly the noise of commer-totype of a simple receiver in- prevent the consumer from SQAM has now produced a Com- cial axes being ground within the tended to he retailed at less than being annoyed." pact Disc record containing 60 industry, with Nimbus claiming$20. AEG of West Germany. with The National AM Stereopho- minutes of material for the sub- that accelerated life -tests havea factory in China, has developed nic Radio Committee was set up jective assessment of both ana-indicated that there could be aa suitable polycrystalline silicon in 1975 charged with assessing logue and digital audio systems. problem, those who have builtsolar array. Porsche agreed to possible systems. Ever since then The 70 segments intended forup a library of CD records mustdesign a special plastics cabinet the technology has been sur- use in accordance with the proc- be counting the years with somefor $5000 but UNESCO has been rounded by controversy. with edures detailed in CCIR Recom- anxiety. unable to find a specialist manu- some proponents strongly criti- mendation 562 comprise: align- Digital audio tape (DAT) mayfacturer willing to produce a cising rival systems, often with ment signals, artificial signals:not he an answer since Rafailproduction mould for the legal action threatened or initi- 36 segments of single instru- Sandu. chief engineer of thecabinet within its budget. The ated. Of the four systems autho- ments: vocal segments with and OIRT Technical Centre in Pra-organization claims that Sie- rized by the FCC in 1982- without orchestral accompani- gue. recently wrote of digitalmens was "not interested". Magnavox AM -OM. Motorola C- ment: solo instruments with audio: "Certain aspects requireAlcatel. the French multination- QUAM. Harris V-CPM and Kahn/ orchestra: orchestral and pop further study...Itisstillnotal company which now owns ITT. Hazeltine i.s.b. - only C-QUAM music segments. known what causes partial signalTelefunken and Schaub Lorenz. and i.s.b. remain in contention The EBU committee believes dropouts in magnetic tapes useddid not respond. Thomson in an atmosphere of fading in- that subjective listening tests are after a storage time of severalwanted $1 million. terest. often essential when assessing months". In recent years UNESCO has As the time approaches for the high -quality audio systems and The French consultant en-pioneered solar -powered 10 watt extension of the North American that the choice of test sequences gineer Marc Chauvierre. who hasv.h.f./f.m. transmitters for broadcast band from 1605 to profoundly affects the result. It worked in television since 1930.Kenya. Burundi. Sri Lanka. Togo 1700kHz, H. Dickson Norman, contends that only if the same has discussed the futuristic pos-and Ghana. chairman of Global Radio Cor- test sequences are used can diffe- sibility of a sound and imageRadio Broadcast is written hr Pat poration (NDXE) of Opelika. Ala- rent listening tests he compared recording system entirely free ofHawker.

936 ELECTRONICS & WIRELESS WORLD Broadband instrumentation amplifier

This design avoids the compromise between c.m.r.r. and bandwidth that characterizes conventional instrumentation amplifiers made from op -amps.

NANNO HERDER

Instrumentation amplifiers made from o(Vi -V21Vi op -amps generally consist of an input - buffer pair followed by a differential amplifier stage. Fig.l. It is rather difficult to realize a differential amplifier with a high rejection factor for common -mode signals combined with a Vo -V21 wide frequency range, mainly due to the op -amp's non -symmetrical structure. Therefore, it is desirable to make use of an input -buffer pair which already has a high common -mode rejection ratio. However, a common -mode component always remains equal to that at the input I (V; +V.0/2. Fig.l I. So a high c.m.r.r. calls for a high differential gain of the buffer (a11. but with the Fig.1. Conventional instrumentation amplifiers made from op -amps usually consist of an input buffer pair followed by a differential stage. drawback of a reduced bandwidth. This common -mode component is greatly reduced in the new circuit of Fig.2. Op -amp IC:; provides a large amount of feedback for common -mode signals in the buffer stage. In this way a high rejection factor can he obtained with low gain. maintaining a high bandwidth. Output of each of the two buffers consists primarily of the difference of the 820 inputs; as a result the following differential amplifier is less critical. 820 Amplifier IC3. whose non -inverting input 0 .1 -20 (V1. V2 V0rK2IVI-V2) can be considered as a virtual earth, forces p the sum of the buffer -outputs to zero. It can 820 be shown that with unequal R, resistors the Cc= 22p common -mode component at the output of Allop amps 5534 the buffers remains low. even in the extreme case that one R3 is removed. However. the V2 820 non -symmetrical structure of the circuit then leads to a reduced c.m.r.r. at higher frequencies. Despite having more components. the circuit needs no extra adjustments for a good needed a stability capacitor (with a= 1). With FIg.2. Adding an op -amp to the convention - balance. and the two additional resistors. R:;. carefulcircuit -hoardlay -out and power - a, instrumentation amplifier configuration do not need very careful matching. Addition supply decoupling, a c.m.r.r. of 100dB at provides a high common -mode rejection of IC; does not degrade noise performance 100Hz and 80dB at 50kHz and a bandwidth ratio over a wide frequency range. Output nor does it increase offset errors. Care must of 1MHz is obtainable. of IC3 is proportional to the common -mode be taken to guarantee the stability of the I recommend the use of low -valued resis- component at the input and can be used circuit. tors (1 kit) to reduce balance errors due to for an overrange indication. Circuits have been built using NE5534 stray capacitances and to maintain a low op -amps which have high output drive capa- noise level. The new buffer circuit can also bility. low noise and high open -loop band- be used as a precision balanced driver. e.g. width. The latter feature is desirable for a for audio purposes. With one grounded good high -frequency common -mode rejec- input, two 180° out of phase signals can be tion figure.In the practical circuit.IC.; obtained from the outputs of the buffers.

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ELECTRONICS & WIRELESS WORLD 51271 715273 os 4076 / I SIIII S ON COMPUTER COMPONENTS 74213 IN 74. 52 n On 407/ LINEAR ICs 700 I% 145210 7474/ 3 II 190 4071 400011 11N 174710 044 T6011 n 129 7401 OM CPUs 1, PROW. 75,56 KEYBOARD 74790 IN 740213 090 4040 4747310007310 0171/ 90 114103 Ow 0 30 0510 711 7401 7415210 0 ,I6110 Ow 1102C2 IN 1695040 14% DECODERS 14293 ON 4042 40103 00 01123 0 % 15103 S% 7403 a10 741571; 1. 02 '11420 01, 2004 1.90 /421. 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NO 24/ 14221 In (ONO 254 76.52S6 O N 1452.1 2N 00 /Go., 110 1114, 210 lop.no 20A057 290" 607 74231 503524 JN 74.524574 670 74520 070 409,/ 110,, 22w 0.61 40,/ ,1106 74290 71460 SOO 7420 76,535114 O 1 "SRA 490229 071 2n 74(5151 745373 4N 0077 nal 7420 In 70540 Se 45374 4% 4073 TURNED PIN 111, 00. 1110. 1001.4600 Ian 154 74274 7445200 075 so 71'95 71p0 Ikon 240e73 560 74170 74.5266 060 211 .075 LOW PROFILE SATS no 006 ON PLEASE ADD 50p p&p & 15 % VAT TECHNOMATIC LTD (Export: no N .NT. p&p at Cost) MAIL ORDERS TO: 17 BURNLEY ROAD, LONDON NW IO IED Orders from (iovernment 1)epts & Colleges etc. welcome. SHOPS AT: 17 BURNLEY ROAD, LONDON NWIO (Tel: (11-2(18 1177). Telex : 922800 Tel: 01-723 0233 Detailed Price List on request. 305 EDGWARE ROAD, LONDON W2 Stock items arc normally by return of post. ENTER45 ONREPLY CARD

ELECTRONICS & WIRELESS WORLD 939 APPOINTMENTS

DISPLAYED APPOINTMENTS Advertisements VACANT: £27 per single col. centimetre(min. 3cm). accepted up to LINE advertisements (run on):£5.50 per line, minimum £48 (prepayable). BOX NUMBERS: £15 extra. 12 noon 25th August (Replies should be addressedto the Box Number in the advertisement, c/o Quadrant House, TheQuadrant, Sutton, Surrey SM2 5AS). for October issue. PHONE: PETER HAMILTON,01-6613033 (DIRECT LINE) Cheques and Postal Orders payable I to REED BUSINESS PUBLISHINGand crossed.

s///1slay on the WorldCirC°1/4 PAGING YOUR FUTURE! Increasingly multinational, high technologycompanies are Our Client, one of the leaders in National Digital considering their Australian subsidiaries an integralpart of their global strategy So it is with our clienta world leader Paging Systems, is seeking additional Engineersas in telecommunications The career positions briefly detailed part of its expansion plan. below are all based in Sydney and offeran intellectually stimulating work environment. and of coursea life style second to none, Competitive salaries, relocationassistance Field Service Engineers and a real opportunity to broaden yourcareer and personal horizons make this an opportunity you should notmiss. London, S. East & Manchester With 2-3 years RF equipment servicing experience RF DESIGN ENGINEER you will service and support transmitter stations An experienced RF or Analogue Design Engineerto join the development team for new Radio Communications Network throughout designated areas of the UK. Some Product, is urrit,r1t6i snunht computer/peripheral knowledge would be helpful. Good customer skills are essentialas is the ability to SYSTEMS ENGINEER (PABX) work on your own initiative. Excellentcareer A senior n ' attract an engineer , Henced w,11 ' vital development prospects will also be available. hardware cosign and real-time assiimblerprogramming Excellent management career prospects Peripheral Test Technicians TECHNICIANS Based at the Assisting the above design engineers with prototyping,lab London, you will and field testing, and pre/post productionactivities is undertake component level repairson a range of challenging and career building Experiencein one or more peripheral devices associated with digital paging of the following fields is essential RF /Digital Hardware/ Software Maintenance/PABX networks. Some RF experience would be useful, but not essential. For further details telephone Phillip Campbell B.E.(Comms) on 010 61 2 95 95 111 between 8 30 a m and 5 30 p.m local For time. or write to Execute Consulting Services P/L,Level further information contact Ray McKenneyon 19 Northpoint. 100 Miller St. Nth Sydney NSW 2060.Australia (0908) 670066 or sendyourCV to Southern (Fax 010-61-2-9594312) Recruitment(Milton Keynes) Ltd, 516 Elder Gate, All applications are treated in the strictest confidence. ElderHouse,Central Milton Keynes. X F. Cl 'FIVE /southern C(1\ StI T I NG a recruitment

New South Wales Licenced Private Employment AgentNo. 779.

Hardware/ As a leading recruitment consultancywe have a wide selection of opportunities for Software/ high calibre Design. Development. Systems DEPUTY CHIEFENGINEER and supporting staff throughout the U.K. Telemotive UK Ltd is a growingcompany within the Davy Corporation and Systems If you have experience In any of the leads the market for industrial remotecontrol. We are extending our following then you should be talkingto us for your next career move. product range and markets with an excitingnew range of electronic control £9,000 - £25,000 ARTIFICIAL INTELLIGENCE IMAGE equipment for the 1990s and we requirean engineer, preferably chartered, toleadthis PROCESSING ANALOGUE DESIGN important development and toliaisewithmarketing, MICRO HARDWARE & SOFTWARE GUIDED commercial and production activities. WEAPONS C PASCAL ADA RF & Experience in radio frequency and infra -red transmission. MICROWAVE ELECTRO-OPTICS SIMULATION microprocessor application and software development willbe ideal, as will C 3 I REAL TIME PROGRAMMING SYSTEMS be proven capabilities in project management. ENGINEERING ACOUSTICS SONAR RADAR Familiarity with industrial motor control and drives is very desirable. The ability SATELLITES AVIONICS CONTROL ANTENNA to evaluate and solve VLSI DESIGN our customers' application problems is essential,as is an appreciation of Opportunities exist with National, International other engineering disciplines such as mechanicaland drawing office work. This new positions and consultancy companies offering excellent willcarry an attractive remuneration package salaries and career advancement. including car, pension scheme and relocationexpenses where appropriate To be considered for these and other If you can meet the challenge we offer, pleasewrite enclosing CV to: requirements contact John Spencer or Stephen Tim Rowley. Managing Director (Ref: ELW1). Recruitment Morley or forward a detailed CV in complete Telemotive UK Ltd, Riverdene Industrial Estate. confidence quoting Ref. WW/ 101. Molesey Road. Hersham. Walton -on -Thames. Davy STSRecruitment,Telephone:(0962) 69478 (24hrs), Surrey KT12 4RY. 85 657 HighStreet,Winchester, Hampshire 5023 9AP.

940 ELECTRONICS & WIRELESS WORLD Wanted urgently Practical people for the CAPITAL Third World. tihu I,fir IIl arr. 71 \\ Lint., 1,1111(11111 \17 (1SF Many people want to help the Third World. 30511 But relatively few can offer the kind of help 'I'llE I. It's No. I 11,1,,CTR(1NICS.%(;EN(lY wanted most: the handing on of skills and professions which lead to self-reliance. ELECTRO \ ENGINEERS it gnu are looking for You could make this priceless contribution jol) ill DESIGN. FIELD SER\ WE. TECHNIC \l, SALES by working with VSO. lir SOFIA\ RE ENGINEERING. Current requests include: Telephone \M\ for one of our FREE Jobs lists or Electronics Ultra -sound send a full (\ to the address below Instructors CJ Technician acancies throughout the I h lo I li.11OO p.a. Studio Refrigeration/ Electronic Radio/ E Engineer TV Engineers El Capital \ppointinents Lid.. EREEPOST London \ 17 ORR. Hospital Electrical Engineers Electronics for instruction/ Engineers installation Please send 1111' list for Higin('iTs Lecturers in Maintenance \ante \\NI Power and and repair CommunicationElTechnician \ddress For more details, please complete and return this advertisement to: Enquiries Unit, VSO, 9 Belgrave Square, London SW1X 8PW. !Nisi Code Conditions of work: Pay based on local rates Posts are for a minimum of 2 years You should be without dependants Many employers will grant 01-808 3050-24 HOt RS leave of absence. I'm interested. I have the following training/ L experience: CLIVEDEN UNIVERSITY OF LANCASTER Name ELECTRONICS Address Technic& -- Recruitment EWW9 88 TECHNICIAN TEST ENGINEER Essex Required in the Department of Repair and fault find radar modules and Psychology. Duties will include the subsystems to C1'.000 development, construction. modification and maintenance of a INDUSTRIAL ENGINEER Essex Experience of electronics production aid wide variety of standard and processes. Knowledge of computerised specialised electronic equipment, stock control systems. Vetting of included micro -computers. A subcontractors. C13,000 mechanical aptitude and the ability and willingness to tackle a variety of INSTALLATION ENGINEER Berks tasks are requirements of the post. Wiring and assembly of computer cabling Experience in electronics (analogue IRS232/%422) for a wide variety of and digital) and appropriate Helping theThird World help itself. commercial companies. Travel througnout qualifications are required. Thames Valley. cC9,0004 car 30p S.A.E.appreciated Charity N0,313757 Salary on the scale: TEST ENGINEER Barks C8.088-0,549 pa. Fault find and repair computer add-ons. Analogue,digital background. C10,000 - Informal enquiries to Mr C. S. Barker (0524) 65201, extn 4052. Application R.F. ENGINEERS throughout forms, returnable by 9 September. are Southern England available from the Several opportunities exist within Establishment Office, commerc al and military companies far University House. Bailrigg LA1 4YW.653 Highbury engineers with any experience of the following: Cellular radio, speech synthesis. VHF/UHF comms telephones.to 0/7.000 College ARTICLES FOR SALE FIELD SERVICE ENGINEER Surrey Repair and service of IBM compatible pcs. COMMUNICATION & MEDIA STUDIES Some software skills useful. 018,000 FIGOLLEDGE1---- Hundreds of other Electronic vacancies ELECTRONIC_Sj Roger Howard, C.Eng, M.I.E.E., M.I.E R.E. RADIO STUDIO CLIVEDEN TECHNICAL RECRUITMENT 92 The Broadway. Bracknell, Berks RG/2 1AR QUARTZ CRYSTALS OSCILLA- Tel: 0344 489489 (24 hour) TORS AND FILTERSof all types. TECHNICIAN Large stocks of standard items. Spe- Technician required to service the Radio Journalism course at the cials supplied to order. Personal and College. Duties will include maintenance and repair of studo ARTICLES FOR SALE export orders welcomed - SAE for lists equipment, demonstration and instruction in the use of equipment. please. OEM supportthru:design Applicants should have relevant experience and be willing to BANKRUPT STOCK OF HITACHIadvice, prototype quantities, produc- undertake training. LM236640x200 dot matrix LCD dis-tion schedules. Golledge Electronics, plays. Modules include 20 IC drive andMerriott, Somerset TA 16 5NS. Tel: Salary £6,376-£6,957 pa (pay award pending) interface logic board. Current distribu-0460 73718. 124721 Hampshire County Council pursues a policyofequalityof tor price £312 each. Our pricefor opportunity and welcomes applications from people with disabilities. sealed cartons of 15 display BRIDGES waveformnitransistor £435+ VAT. Samplesavailableforanalysers. Calibrators, Standards. Full details and application form from Personnel Office (ext 225). £35+ VAT. Carriage £11.50. Any order. Millivoltmeters. Dynamometers. KW Closing date: 8th September 1988. Send S.A.E. for data. Tel: 0600 3715.meters, Oscilloscopes. Recorders. Specialistsemiconductors.Founders Signal generators - sweep, low Cosham, Portsmouth P06 2SA House. Redbrook, Monmouth, Gwent. distortion, true RMS, audio, RM, Telephone: (0705) 383131 656 640 deviation. Tel: 040 376236. (2616)

ELECTRONICS & WIRELESS WORLD 941 Service Manual for M.E.L. Marconi phase -locked frequency synthesiser. ARTICLES FOR SALE TF21708/2002. accuracy Ippm. £175 APT Automatic Antenna Tuner stablised PSU. variable 0-50 V. 2A. £39. 0-50 type BA 1020/01 (part of V 12A, £30Philips DMM. £35Advan, Audio/Ultrasonic Generator 15c/s-50KcJs. sire HAVING DIFFICULTY OBTAINING AN OBSELETE Clansman Radio Set) square £19 Radiation Counter. MP!. wanted. High reward. readout, light pulse indicator. audio pulp . VALVE/TRANSISTOR/LC.? sensitivity better than 0.1p Sv/hr. safetyas We try harder to locale rare types! Delivery either ex stork 11-21 day. ar haw our averveav source. 15.8 doetU Please contact: wellas danger. don twait ' expected increase on sunspot activity. nuci- r. WE ALSO STOCK ALL POPULAR TYPES - USUALLY THE LOWEST PRICES ANYWHERE Helmut Singer, accidents etc. monitor home and workplac. (comport our prices listed below!) we'll nearly always beat any written quote. Feldchen hotspOts - imported materials. use forrr.i. Large discounts for wholesale quantities phone/fax/telex for on immediate quote. 16-24, D-5100 surveys. etcetc.. £135 Avo 7 meter mo,. Free advice re egulualent etc. (we've specialised Invalves and translator.since 1982). Aachen, W. Germany. ment (new) El 5Five decade DC calibrator New boed guaranteed valves. Good quality brands (IlluLBri.STC etc.) £98 Dual stabilised PSU 0-30V. 1A. £69 Avo . tk.p, r6 quote n11111. for Mar., KIEntron Tel:010-49-241155315. 7Testmeter £39Philips portable counter/ RM. add IS% VAT en and 4r IS pap guard*, Telephoneyour or dersuotina VISA. RARCIATCARDInot ACCESS - Telex: 832504 SITRO D. frequency meter£69 Stereo cassette ...AIL et send cheque 6, prompl despatch by let Claes Pon AllpanelsWastediai sat exogamy) ageismdamageM banal.. mechanism, dual drive £10 60W integrated 63641 220 ,84 95VVV0640A 24 00 IS.,.,.le.,,,6.6. lot MOvalve ratalog. of a.6.,., circuit amplifiers £6 50High intensity pre - 6066 1204I34 240110142 2 00 ,,,,,,,,,,.,, focus lamps. microscopy. optical AF transmis- E88CC 300,2731 Y. 340 10-41 110 E88CCMv 4501,166 "4,0 11141 700 PCB ASSEMBLY sion.signallingetc.£2Vanaciranstormer E8113) 2400RCA 9.00Un41 300 controlled AC variable PSU. 0-240V. 2A. 0-7V. ECC81 80h188 USA 10754CO2508 5A, £35 Electrostatic EHT meter 0-6KV £8 ECC82 80M8136 Ma 6.00Ernst 56.00 (Conventional) & TEST ECC83 93M8137 Hui 70058,254M 1400 BILLINGTON VALVES MIG welder. portable. single power supply. ECM Mu, 100M6162 Mug 50058'255M £95. dual power supply £110 Oscilloscopes. 1900 GOOD QUALITY LOW PRICE RARITIES EE86 210 140604688mm 6.90 A SPECIALITY ,iality work, attention to detail generators bridges etc. etc EF81 140 14068A6 100 59 Highland* Rand. Horsham. Sussex II/113 5LS EE92 185 806133 SiC and follow through are our forte. Not 900 (Callus writ on.* but In appointment only) 040-376236. 2016 EE95 80 12E1 1700 Piton* 0403 210729 I.. 0403 40214 Totes 87271 a single dissatisfied customer in ten (134 280 44557b1 575 314: 270 2300 years. Over 18.000 boards built and Chlikh 111 logantb 30 pen Magnetrons. KI,11.er aye tubes .loo altrektni lAnsisenihone tele* and la* !eh on o.ernighe .,d tested. Low overheads and efficiency SERVICES ensure very competitive prices. TO MANUFACTURERS, WHOLESALERS Evem EOM SEMIS 1.11 Gwel An Wheal, St Ives, Cornwall. PCB CAD DESIGN BULK BUYERS. ETC. Tel (07361794670 PCB designed on computer system fur 652 LARGE QUANTITIES OF RADIO. TV AND as little as 10 60 per pin. Input information can be schematic ELECTRONIC COMPONENTS FOR DISPOSAL WANTED nett list or existing and produced PCB. SEMICONDUCTORS. all types, INTEGRATED CIRCUITS, TRANSISTORS, For a speedy efficient service contact DIODES, RECTIFIERS, THYRISTORS, etc. RESISTORS, C/F, M/F, W/W, etc. Test equipment,receivers, us now on: CAPACITORS, SILVER MICA, POLYSTYRENE, C280, C296, DISC valves,transmitters,com- Tel: 0934 22044 or CERAMICS, PLATE CERAMICS, etc. ponents, cable and electro- Fax: 0934 416238 ELECTROLYTIC CONDENSERS, SPEAKERS, CONNECTING WIRE, CABLES, nic scrap and quantity. SCREENED WIRE. SCREWS. NUTS, CHOKES, TRANSFORMERS, etc. Prompt service and cash. ALL AT KNOCKOUT PRICES - Come and pay us a visit ALADDIN'S CAVE TELEPHONE: 445 0749/445 2713 M & B RADIO CALIBRATION R. HENSON LTD. 86 Bishopsgate Street Need not costa ! For a free quote on 21 Lodge Lane, North Finchley, London, N.12 Leeds LS1 4BB your DV M ,,....,..,scope or frequency 15 minutes horn Tally Ho Corner) 11613, counter Send type of instrument, make and 0532 435649 995), 6, ,,0! dErOils to 'LAT1NUM, GOLD, SILVER calibration Room WANTED SCRAP. Melted assayed and paid for 3' 7 DIGIT Bluehorrow Limited within 24 hours relay contacts, thermo D.M.M. Brookside Cottage STEWART OF READING couples, crucibles. Also printed circuit Main Rood TURN YOUR SURPLUS FROM £5.00 Brighstone 110 WYKEHAM ROAD, boards, plugs, connectors, palladium, ICs transistors etc into cash rhodium, tantalum and ruthenium. We (Calibrator to 55/)4.1) IOW P030 401 649 Immediate settlement. We also READING RG6 1 PL. have the technology to do the difficult welcome the opportunity to quote TEL: 0734 68041 refining jobs that others can't handle. Totally free sampling service. SendNORTH CORNWALL DESIGN LTD for complete factory clearance. TOP PRICES PAID FOR ALL - Software and Electronic design to Contact: samples or parcels (Regd post) or TYPES OF SURPLUS TEST contact Eric Henderson,0773 570141. your requirements. In-house CAD and COLES, HARDING & Co EQUIPMENT, COMPUTER Steinbeck Refineries(UK) Ltd,prototyping facilities available. Initial 103 South Brink, Wisbech, Cambs. EQUIPMENT, COMPONENTS Peasehill Industrial Estate, Ripley,consultation free. Ring: 0566 2958 and Tel' 0945 584188 Fax: 0945 588844 DerbyshireDE5 3JG. No quantity ask for Pete Hurford. F STABLISIIED OVEfi ISVE ARS 1,92 etc. ANY QUANTITY too large or small. 495 CLASSIFIED ADVERTISEMENTS Use this Form for yourSalesandWants PLEASE INSERT THE ADVERTISEMENT INDICATEDON FORMBELOW To "Electronics & Wireless World" Classified Advertisement Dept., QuadrantHouse, The Quadrant,Sutton, Surrey SM2 5AS

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'12 ELECTRONICS & WIRELESS WORLD What Do Next Year's Graduates Think Of Your Company's Image?

The fact is good graduates are spoilt for choice. To stay one step ahead in the race for good graduatesitis ESSENTIAL that YOUR company maintains the highest profile possible. Technology Graduate is the ONLY maga- zine for ALL graduates pursuing hi -tech careers. 32,000 full -colour copies of Tecnnology Graduate hit EVERY single campus in the UK at the three most crucial points throughout the academic year - that's every term. To help YOU maintain YOUR all-important corporate image, Technology Graduate has de- vised a superb financial discount package. Whether you need one or one hundred, if you're serious about graduate recruitment call us now: PAUL SISSONS 01-661 3406/3112 CLARE BUTLER 01-661 3402 Winter issue delivery date is 24th October 1988 (Copy Deadline - 17th October teehnolog/ GRADUAT-ft CAREER OPPORTUNITIES FOR ALL GRADUATES

ELECTRONICS & WIRELESS WORLD MATMOS LTD,1 Church Street, Cuckfield, West Sussex RH17 5JZ. Tel: (0444) 414484/454377. COMPUTER APPRECIATION,30/31 Northgate, Canterbury, Kent CT1 1BL Tel: (0227) 470512. TRIUMPH ADLER/ROYAL OFFICE MASTER 2000 DAISY WHEEL PRINTERS. FUJITSU Model M2230AS 51,4 WINCHESTER disc drive. 6.66mbyte capacity 20 cps. FULL IBM AND DIABLO 630 COMPATIBILITY, CENTRONICS unformatted. 16 32 sectors. 320 cylinders With ST506 interface. BRAND NEW INTERFACE. Featuresincludeunderscore.bold.subscripts.superscripts. £47.50 (carr. £3.00) underline etc. 132 column: micro proportional spacing. Complete with typewheel DRIVETEC Model 32C high capacity 5,/a" disc drives. 3.3mbyte capacity drive - and ribbon, manufactured to highest standards in West Germany by Europe'ssame manufacturer and same series as KODAK 6.6mbyte drive 160 track No largest typewriter manufacturer and offered elsewhere at over £350 00 further info at present. BRAND NEW £25.00 (carr. £3.00) £119.50 (carr. £6.50) - £99.50 each for quantities of 5+ ASTEC SWITCH MODE PSU. 5V 10 8A: r 12V it, 3A:12V or 0.3A - to a total VICTOR SPEEDPAK 286. 80286 based speed up card for IBM PC and most 65W Compact cased unit. Ex -equipment. tested £14.50 (carr. £3.00) HEWLETT PACKARD Model 59307A dual VHF switch. DC to 500MHz 50 Ohm compatibles. Features cache memory and runs 6 to 7 times faster switch for HP-IB £185.00 £99.50 (carr. £3.00)HEWLETT PACKARD Model 5045A digital IC tester with CONTREL Model PANASONIC Model JU-363 3'/2" floppy disc drives Double Sided DoubleH310 automatic handler. With IEEE interface and print out of test results either Density 80 track1 megabyte capacity unformatted. Latest low component '/3pass/fail orlull diagnostic including pin voltages at point of failure. With full height design. SHUGART compatible interface using 34 way IDC connector. Willcomplement of pin driver cards and complete with substantial library of magnetic interface to lust about anything. BRAND NEW (We can offer at least 20%card test programs for 74 series TTL and other ICs. CONTREL handler allows fully discount for quantities of 10 plus). Current model. We can supply boxes of 10automatic testing of ICs which are sorted into 2 bins. Price includes a second discs for £15.95 plus £1.50 carriage £59.50 (carr. £3.00)HP5045A (believed fully operational) for maintenance back-up f550.00 PLESSEY Model T24 V22/V22 bis 2400 Baud MODEM. Including free softwareHEWLETT PACKARD Model 28C pocket calculator with graphics £1 00.00 disc for IBM or MATMOS PC Compact. automatic modem featuring the latest CASIO Model FX8000 calculator with graphics and interface £50.00 technology and the highest possible data rate over the ordinary phone system.ICOM micro2E 2 metre transceiver with carrying case £150.00 Offers; both V22 and V22 bis compatibility. 1200/2400 Baud operation with auto bitTIME ELECTRONICS Model 9810 programmable power supply £160.00 rate recognition, operation on both ordinary phone (PSTN) and private circuit (PC). ITT PERFECTOR TELEX MACHINE. With 32k memory. screen with slow scrolling auto call and auto answer, duplex operation allowing simultaneous transmissionetc £350.00 and reception of data at 2400 Baud in both directions over a single phone line. HEWLETT PACKARD MODEL 5501ALASER TRANSDUCER.With compact size (9" x 9" x 2'12"). BT approved and suitable for new PRESTELpiezoelectric tuning for precise control of wavelength for measuring V22bis service. Software is included for IBM PC, MATMOS PC. and (including applications £350.00 high speed Prestel) for BBC MICRO. BRAND NEW. NEW LOW PRICE VICKERS INSTRUMENTS MODEL M17 METALLURGICAL MICROSCOPE with £119.50 (carr. £5.00) - £99.50 each for quantities of 5 binoculars micrographic head and all eyepieces With 4 Microplan objectives and DUPLEX Model 100 green screen 12high resolution monitor with compositeNomarski interference contrast £1,250.00 video input With tilt and swivel stand BRAND NEW £39.50 (carr. £5.00)KRATOS MS30 DOUBLE BEAM MASS SPECTROMETER. Approximately 8 ITT SCRIBE III WORKSTATION. Monitor sized unit with high quality high years old with negative ton capability and fast atom bombardment (FAB). With gas resolution 12" green screen monitor (separated video and sync), 5V and 12V and direct introduction sample probes and with gas chromatograph inlet system. Output spectra are available directly via a HEWLETT PACKARD storage display cased switchmode power supply, processor electronics incorporating TEXAS and a UV recorder. An on-line DATA GENERAL DS60 computer system, which 9995 and Z8OH processors with 128kbytes and associated support chips. all includes a graphics printer and two TEKTRONIX 4014 terminals. analyses BRAND NEW but with only monitor and power supply guaranteed working. output ... p.o.a. Original cost at least £2.500 £29.95 (carr. £5.00)LUMONICS SYSTEM 2000 RUBY LASER with 0 -switch and frequency doubler ITT SCRIBE III KEYBOARD. Low profile keyboard for above with numeric0.3 Joule per pulse. 6 ppm. Suitable for holography A low powerHe/Nelaser for keypad. serial interface BRAND NEW but untested ...... £8.95 (carr. £5.00) mirror alignment is included £3,500.00 TRANSDATA Model 307 ACOUSTIC MODEM. Low cost self-contained modemSPECTRA PHYSICS Model 164-08 Argon ion laser 4 watts output (all lines) unit allowing micro or terminal connection to BT lines via telephone handset V24 Complete with 3 phase transformer £3,500.00 interface. up to 300Baud. originate/answer modes. etc BRAND NEW withPlease note: *VAT & carriage (also - VAT) must be added to all prices. manual £14.95 (carr. £3.00) * VISA and ACCESS orders accepted ENTER 19 ON RENA' CARD INDEX TO ADVERTISERS Appointments Vacant Advertisements appear on pages 836-839

PAGE PAGE PAGE PAGE Aircastle Products 925 Field Electric 901 Level) Electronics 926 Sherwood Data Systems 899 Airlink Transformers 870 Livingston Hire 896 Slee Electro Products 899 Gould Electronics I FC Stewart of Reading 886 M & B Radio (Leeds) 901 Strumech Engineering 896 Cambridge Kits 902 Hameg 890 M A Instruments 902 Superkit Electronics Inc 895 Cavendish Automation 931 Harrison Electronics 870 M Q P Electronics 886 Surrey Electronics 928 Chemtronics UK 851 Hart Electronic Kits 931 Colomor Electronics 925 Henrys Audio Electronics 895 Number One Systems 902 Communique 925 Icom I UK) Limited 931 Taylor Bros. (Oldham) 842/IBC Computer Appreciation 944 Omega Dynamics 863 Technomatic 938/939 John's Radio 926 Tektite 901 Dataman Designs OBC Private Mobile Rentals 899 Thandar Electronics 851 Display Electronics 935 Kestrel Electronic Those Engineers 928 Components 873 R Henson 926 Thurlby Electronics 928 Ralfe Electronics 886 Engineering solutions 873 LI Electronics 870 Raycom Communications European Electronic Systems 890 La ngrex Supplies 895 Systems 896 Webster Electronics 851

OVERSEAS ADVERTISEMENT AGENTS France and Belgium: Pierre Mussard. 18-20 Place de la Madelaine. Paris 75008 United States of America: Jay Feinman. Reed Business Ltd.. 205 East 42nd Street. New York. NY 10017Telephone 12121867 2080 - Telex 23827

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944 ELECTRONICS & WIRELESS WORLD TAYLOR R.F. EQUIPMENT MANUFACTURERS PERFORMANCE & QUALITY 19" RACK MOUNT CRYSTAL CONTROLLED VESTIGIAL SIDEBAND TELEVISION MODULATOR PRICES FROM £203.93 (excluding VAT & carriage) Prices CCIR13 £203.93 CCIRI3-1 £260.64

19" RACK MOUNT VHFIUHF TELEVISION DEMODULATOR PRICE AT ONLY £189.00 (excluding VAT & carriage)

CCIR/3 SPECIFICATION Power recimement - 240V 8 Watt (available other voltages) Video Inpit - IV Pk -Pk 75 Ohm Audio Input - 8V 600 Ohm FM Sound Sub -Caner - 6MHz (available 5 5MHz) Modulation - Negative IF Vision - 38.9MHz IF Sound - 32.9MHz (available 33 4MHz) Sound Pre-Emphass - 50us Ripple on IF Saw Filter - .6dB Output (any chann.l 47-860MHz)- +6dBmV (2mV) 75 Ohm Vision to Sound Power Ratio - 10 to 1 Intermodulation - Equal or less than 60dB Spurious Harmonic Output - -40dB (80dB if fitted with TCFL1 filter or combined via TCFL4 Combiner/Leveller

CCIR/3-1 - Specification as above but output level 60dBmV 1000mV Intermodulation 54dB WALLMOUNT DOUBLE SIDEBAND Other Options Avalable - I F Loop/Stereo Sound/Higher Power Output TELEVISION MODULATOR Alternative Applications - CCTV Surveillance up to 100 TV channels PRICES FROM ONLY £104.53 (excluding VAT & carriage) down one coax, telemetry camera control signals. transmitted in the same coax in the reverse direction

802 DEMODULATOR SPECIFICATION Frequency Range - 45-290MHz. 470-860MHz A.F.C. Control - +/- 1.8 MHz Video Output - IV 75 Ohm Audio Output - 75V 600 Ohm unbalanced Audio Monitor Output - 4 Ohms Tunable by internal preset Available for PAL System I or BC

Options - Channel selection via remote switching Crystal Controlled Tuner Stereo Sound.

CCIR/5 MODULATOR SPECIFICATION Power Requirement - 240V Video Input - IV Pk -Pk 75 Ohms Audio Input - IV rms 30K Ohms Adjustable 4 to I . Vision to Sound °ower Ratio - 10 to 1 Output - 6dBmV (2mV) 470-860MHz Modulation - Negative Audio Sub -Carrier - 6MHz or 5 5MHz Frequency Stability - 25 Deg temperature change 150KHz Intermodulation - less than 60dB Sound Pre -Emphasis - 50us Double Sideband Modulator(unwanted sideband can be suppressed using TCFL4 Combiner/Level'er)

CHANNEL COMBINER/FILTER/LEVELLER to combine outputs of modulators

TCFL2 2 Channel Filter/Combiner/Leveller. Insertion loss 3.5dB TCFL4 4 Channel Filter/Combiner/Leveller. Insertion loss 3.5dB Prices TSKO Enables up to 4.TCFL4 or TCFL2 to be combined CCIR/5-11 Modulator £104.53 CCIR/5-22 Modulators£159.99 TAYLOR BROS (OLDHAM) LTD CCIR/5-33 Modulators£226.28 BISLEY STREET WORKS, LEE STREET, CCIR/5-44 Modulators£292.56 OLDHAM, ENGLAND. CCIR/5-55 Modulators£358.85 ENTER 2 ON REPLY CARD TEL: 061-652 3221 TELEX: 669911 FAX: 061-626 1736 "It's a pretty small battery -powered PROMprogrammer - sowhat?" Tools which are convenient get used a lot - that justifies I, "I'm bound to let the battery go flat." their existence. Thereisno way we could .0 Quite so. But in practice it doesn't matter. S3 switches explain all the usefulness of S3 here. lit off after a half-hour of non-use anyway, or when the Instead, if you're interested we're 7o battery gets low. You don't lose your data. Then a going to let you see it, use it and evaluate it in your own slow -charge overnight or boost -charge for three workshop. We went to a lot 2 hours will restore full capacity. You can keep using of trouble to design S3 just it when charging. So there really is no problem. the wayitis- no other PROMMER is all CMOS and "I already have a programmer." all SMT. So we must he con- Pityit doesn't have S3 features, eh? But vinced that S3 would be a for- here's a trick worth knowing. If you plug midable addition to your S3's EMULead into the master socket of a armoury. Now all we have to do ganger then you get an S3 with gang is to convince you. capacity.Isn'tproductionseparate from development anyway? "Such a little thing can't be powerful, like a big bench- "It looks nice. Will I be programmer - er - can it?" disappointed?" Yes, it can. It is more powerful. S3 leaves Dataman tools are designed to other prommers streets behind. S3 has be used by Engineers. Not continuous memory. which means that you justsoldto Management. can pick it up and carry -on where you left off Have you ever been misled last week. S3 has a huge library EPROMS and by some mouthwatering EEPROMS. S3 can blow a hundred or more ad for a new product. PROMS without recharging. S3 also works re- Great artwork and ex- motely, via RS232. There's a DB25 socket on the citing promises which hack. All commands are available from your computer feed your fancy? On (through a modem, even). Also S3 helps you develop impulse you buy and and debug microsystems by memory -emulation. when the thing arrives you feel let down. The pic- "What's this memory -emulation, then?" ture looked better. The claims It's a technique for Microprocessor Prototype Develop- are hardly justified;not exactly ment, more powerful than ROM emulation, especially misrepresentation,just useful for single -chip "piggy poor implementation. hack" micros. You plug the But you've boughtit. lead with the 24/28 pin header And you're stuck with it. in place of the ROM/RAM. It stays in the cupboard, You cliptheFlying -Write - most of the time. So how Lead tothe microprocessor about this: buy S3 and and you're in business. The use it for up to a month. code is entered using either Softy3 is here! If you're nut still thrilled the keyboard ortheserial then you can have your interface. Computer -assembled money hack. files are downloaded in standard format - ASCII, BINARY, INTELHEX, MOTOROLA,TEKIIEX. "Refund in the first month!How can you offer Your microprocessor can WRITE to S3 as well as READ. You that?" can edit your variables and stack as well as your program, if you keep them all in S3. We trust S3 to fire your enthusiasm.We trust you not to use us S3 can look like any PROM up to 64K bytes, 25 or 27 series. as a free hire -service. We bet youwon't send it hack. How Access is1(X)ns - that's really fast. Memory -emulation is would you manage without it? cheap, it's universal and the prototype works "like the real thing". "These things cost a fortune and take months to arrive." We wouldn't get you all excited and then let you down. It Costs S3 loads its working programs out of a £495plus VAT. That includes P & P, Charger, EMULead, PROM in its socket, like a computer Write Lead and a HELP program in ROM. S3 is in stock. Buy it today. Use it tomorrow. (That's a fair promise. But please loads from disk. Software expansion is reserve product by phone or telex to make it come true). unlimited. Upgrades will come in a TOOLS PROM. Programs can be exchanged Fr)1? between users. How's that for upgradability? . VIC/0 ,E.VG/NEERIA "Can I change the way it works?" Lombard House, You surely can. We keep no secrets. System Variables can be Cornwall Rd. "fiddled." New programming algorithms can be written from DORCHESTER the keyboard. Voltages are set in software by DACs. If you Dorset DT1 1RX. want to get in deeper, a Developers' Manual is in preparation Phone 0305 68066 Telex 418442 which will give source -code, BIOS calls, circuit -diagrams, etc. If you purchase while this ad is current, you have 28 days to We expect a lively trade in third -party software e.g. dis- examine the goods and return them for refund. Carriage will be assemblers, break -point -setters and single -steppers for various charged at cost. The right to charge the cost of refurbishment VISA micros. We will support a User Group. of damaged goods is reserved. ENTER 3 ON REPLY CARD