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CIRCLE NO. 140 ON REPLY CARD CONTENTS FEATURES SPEECH GENERATION 297 Technology isn't a problem. Consumer resistance to talking applicances may he harder to deal with.
1 HE PC INSTRUMENT BUS 309 The IEEE 488 bus means as much to small companies as large ones and is used by both the scientific community and industry.
CACHE MEMORY FOR VME 314 Cache can provide a cost-effective alternative to large Y r' blocks of high speed system memory. HIGH LEVEL PIRACY 318 The broadband linear characteristics of broadcast satel- INTERFACING WITH C 280 lite transponders has opened the door to a new breed of Fed up with whimsical microprocessor code hut need high technology radio pirate. riding piggyback with nar- assembly speed? The C language may provide the rowban.1. low power transmissions. answer. This is the first part in a series of articles about the use of C written specifically for electronics REVIEW: PRO7 EL SCHENIA1 IC 321 engineers. It demonstrates the role of the language A 2-1) circuit draughting package with a simple to use. in connecting microcomputers to the real world. intuitive user interface.
REVIEW: PRO1 EL AUTOTRAX 323 SPEECH RECOGNITION 292 The PCB design package which complements the Sche- Computers are still pretty stupid: the prospect of matic software. holding an interesting conversation with your tumble dryer remains a nightmare. MOSFET AUDIO POWER 343 Ivor Brown proposes a high feedback mosfet audio COMPETITION 295 amplifier design. We are giving away 10 speech development kits based on the TMS 3477 chip featured in our Novem- LOW COST BO XRD TEST 354 ber issue. Low volume hoard testing without programming or expensive test fixtures.
REGULARS COMMENT 267 PIONEERS 340 A touch of comic relief in the defence industry. Emilie Baudot. a simple man of -tumble origin devised a machine w hich enabled five operators to send messages RESEARCH NOT ES 268 down a single line simultaneously. But they all had to More efficient solar power. optical chips for super- keep strictly to time "which put a certain nervous strain computers. solar tlu. covered in boils. on the operator."
UPDATE 274, 291 BOOK REVIEWS 349 Microprocessor bloodbath for Motorola? The AT&T light computer and other news from around the industry.
CIRCUIT IDEAS 302 In next month's issue. Compact Disc electronics may APPLICATIONS 326 not be the wonder of. science which the manufacturers Single chip signal conditioning system for cellular purport it to be. Ben Duncan investigates the shortcom- radio and wideband GaAs amplification. ings and looks for solutions. Roger Dewell describes recent advances in medical LETTERS 330 electronics. In particular, he examines the role of signal processing in NM R and computer tomography. Plus the second part of our series "Interfacing with C", a guide NEW PRODUCT CLASSIFIED 336 to the language for electronics engineers. Three pages of new product information.
April 199(1 ELECTRONICS WORLD+WIRELESS WORLD 265
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CIRCLE NO. 118 ON REPLY CARD COMMENT
Comic relief CONSI LTING EDITOR "What on earth do you mean 'Who is it £2011 million by a bunch of spivs from Philip Darri igton going to fight?' Just because it's called Silicon Valley. I really don't know. 01.661 8632 'European Fighter Aircraft', it doesn't "Then, just to compound it. you come actually mean that it has to fight along. dip into the GEC cash mountain, EDITOR anybody No. we're not going to use buy up the Frans. Ogden ... Ferranti radar business and 01-661 3128 it to attack the Germans now they've scoop a £2hn euro -fighter radar contract. opened up the Berlin Wall ... Really, It's going to take a lot of explaining." ILLUSTRATION Ingham, you should save that sort of off- Ingham rolls over onto his back, spits Roger Goodman the-record comment for the rat pack." out the paper. and resumes the attack on Ingham, looking dejected., skulks off the telex ision. DESIGN & PRODUCTION to a corner of the room Alan herr occupied by the "Arnold, What do you mean Tm television set. There is a knock on the doing you a favour'? Just because you EDITORIAL ADMINISTRATION door. Ingham growls menacingly. save 6001) people in Scotland from losing Lindsey Gardner Ingham is a Rottweiler. their jobs doesn't mean that you acted in 01-661 3614 "Get that please, Dennis." Dennis the National Interest. Most of them shuffles off into the pastel decorated don't even vote ADVERTISEMENT MANAGER Conservative." hall. He Paul Kitchen returns with a captain of "Now come along you two." 01-661 3/30 industry. Lord Weinstock and Mrs Thatcher "Lord Weinstock. Margaret." turn to Dennis, previously un -noticed. DISPLAY SALES MANAGER "Evening. Arnold. I'm delighted that somewhere at the back of the room. Mrs Shona Finnic you could spare me the time to sort this Thatcher glares. 01-661 8640 out. I am rather concerned that we "I've been thinking ... Remember ADVERTISEMENT ADMINISTRATION should be seen to practice as well as that Nimrod thingy you were involved Karen D'Cru.s preach the spirit of free enterprise. with. Lord Weinstock? I low about 01-661 8469 "The House seems to he getting a hit taking those GEC radar sets out of restless about your series of mergers and mothballs and fitting them in the ADVERTISING PRODUCTIOV buy-outs. It thinks that you could stitch European Fighter Aircraft? I don't Una Russ up the MoD through lack of 01-661 8649 competition suppose that they will work any better ... No. I'm sorry, Arnold. We've than tfev did in the Nimrods but at least PUBLISHER absolutely no intention of privatizing you will be able to blame the Italians Susan DOW/ley Parliament. Well ... Not until we've 01 -bbl 8452 floated Electricity." "Dennis, do be quiet." Ingham, w'no had previously dear." FACSIMILE "Yes, 0/-66/ 8939 contented himself with gnawing a leg of Lord Weinstock bids them goodnight the television. starts tearing up a copy of and leaves. The Independent. "Ingham. I've got it! We simply tell "Look. Arnold. It was had enough our people that. with the advent of 1992, /' REED BUSINESS when yKmit PUBLISHING you got together with Siemens and we no longer have to worry about GROUP divided up Plessey. Nice George national monopolies because of Younger. That business upset h:m competition from Europe. terribly at Defence. It meant a reshuffle. "For instance, we can defend the I had to put someone in at the MoD for GEC monopoly in airborne intercept by no rnnnn II.r1J ItSrrlr.. It or1A 1. pmhh.hed monihl, I SPSO...74n Bs pe.s1. current issue t3 2`. hack 1,11C a.olnhls 11.-' "1 Order .end whom life was infinitely worse .. pointing to the open competition from i111 pnsm0nts lm F1n 4nmo s o.n1 Ier.,/ess World. Vu.tdr.ml I Iouse. I he That's Tom . Quadrant. Suuo, Surtes 5512 5,55 (ñeque, should he pas able In Reed right. King, from the continental defence contractors .. Rumness Puhh.hmgLtd t:ditnrinl8 Ad/ erti.ing offices: Fu'II'Ou.idr.mt Northern Ireland office. "What do you mean. Like who'? llone. I he Quadrant. Sutton. Surfs, 553 rAS Telephmnrs: Eddnm..1 111-N,I 3514 Adscru.ingnl -rw,l 1130lll-Inl rh,n Ides: 592115-1 RI I Il "This Ferranti nonsense really is the Siemens. of course." BP G IEEP) Facsimile: OIa,h1 .t55'11G1o0p. II A III) NOa.u.1d0 last straw. How those buffoons could let Ingham looks Quadrant Puhll.hing Sets ices S'o 111-11131 33411 Suhssripl ion ralry:ls . puzzled. closes both Inolmal rnlc) £511 l (: and tti oulsxle (1. Suh.criplh,o.: Quash ant themselves be taken to the cleaners for eyes and goes to sleep. Suh.crlptlnn S0rs11:0., ()Afield Iloue. Pcrr,mounl Root. I Los .mds Heath. Sussex 5111h 51)11 Icicphone II.U1 111212 Please nnn . Frank Ogden change el a,ldre.. I S5: SI1I.IMI atrrn.ol Reed Business Publishing II'SA) Suhwalptlon. (Ittl.e. 211: E 12nd S1res1. N1' 11111' (hrr,rs ..dseriL'ng agents: F caner and Belgium: Plcrre SI u..nnl. Is -31119.e de la 5ladelrme. Pate. -vuls I nhed S1ate, nF inlrrloa: Jas I ornan. Reed Bu. .. Puhlnhmg Ltd. 21)9 Last 42nd .StreOt. NOs. 1 ink. Nl 11111-
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April 1990 ELECTRONI('S \VORLD+ WIRELESS WORLD 267 RESEARCH NOTES
Bright future for solar power Whether it's because of the had press increasingly suffered by the nuclear and Light rays coal -burning utilities or just pure coinci- Lensed cover slip dence, there's been a lot of recent development in the world of pho- \\ ; 1 r\ tovoltaics. No longer are solar cells just Conductors the province of pocket calculators. itti!\ti\Ifst remote settlements and spacecraft. Se' - GaG As eral recent achievements suggest that in future we will he directly tapping just a Ga Sb little hit more of the prodigious output of our friendly cosmic fireball. To list just a few of the latest develop- The idea of using two layers was orig- All this might seem a long way ments. it "s worth noting the present effi- inally pioneered by Sandia Laboratories removed from everyday applications of ciency record for unassisted silicon tv overcome the spectral limitations of a solar cells, especially in view of the photovoltaic cells set by M. Green et al single material. Gallium arsenide. with expense. It's therefore worth reminding at the University of New South Wales in its large handgap of 1.42eV is more effi- ourselves about the parallel progress Australia. Given a standard level of cient than silicon (I.2eV) at converting towards cheap mass-produced pho- illumination of I kW/m' (about the most photons into electricity. though -this tovoltaics. Companies like BP Solar you're likely to get, even in Oz) Green very property means that low energy have, for example. exceeded 16% effi- and his colleagues [Applied Physics Let- (infra red) photons are inevitably ciency with commercial modules. Costs ters Vol. 55 No 1363) have achieved a wasted. Sandia therefore constructed a have likewise tumbled by almost an 23% efficiency for power in versus cell with a gallium antimonide layer order of magnitude over the last electricity out. It's important to empha- underneath the GaAs. Gallium anti- decade. leading to a considerable size the standard irradiation condition monide has a bandgap of only 0.72eV growth in the market photovoltaics. because higher efficiencies can be and can therefore utilise the IR wave- Given the increasing environmental achieved using sunlight concentrated by lengths that would otherwise represent unacceptability of many other forms of mirrors or lenses. This is not because of a loss in overall efficiency. power generation. this trend is more the concentration per se but because This basic structure. when further than likely to continue. not just for photovoltaic efficiency improves as the developed by the Boeing High Technol- pocket calculators, but for multi -mega- light level rises. Figures near 30% can ogy Center in Seattle. results in the watt industrial installations. As Robert be achieved at 100k\\ m2 input. A composite design shown in Fig I. Its Hill of Newcastle Polytechnic observes second significant development that 37% efficiency figure derives from a (Physics World Vol3 No I) "Es en in the takes the absolute efficiency record to combination of the double layer. the UK it is now cheaper light a garden shed 37% uses a novel two -layer design in cover slide and the fact that it operates or telephone box with solar energy than combination with a special optical cover at flux levels considerably higher than to run a mains cable more than 20m or slide to concentrate the light. normal sunlight. so". Optical chips for supercomputers AT&T Bell Laboratories have bias from 6V to 15V increases the con- well structure. This, when subject to an developed a photonic IC which can pro- trast ratio (signal power) of the output. external electric field, can modulate the cess 2Khit of optical data in parallel. but at the expense of optical switching light absorption by red -shifting the peak Structurally the photon ic IC consists energy required at the input. In more of the optical passhand. When such a of an array of 32 by 64 cells. where each detail, each S -SEED cell comprises a diode is reverse biased, it forms an is cell is what Leo Chirovsky of the Light - pair of 11 -i -n diodes in which the middle optical histahle device that switchable wave Devices Laboratory calls a reflec- layer consists of a multiple quantum by optical signals alone. The AT&T tive mode, symmetric Self Electro -optic device as described IOTA Proceedings AT&T Bell Laboratories new S -SEED Effect Device (S -SEED). The S -SEED on Photonic Su itching 3,3 (1989) Chiro- (symmetric self-electro -optic effect has a differential optical input that takes vsky et all can switch in sub -nanosecond device) array. Devices are fabricated as 5µm diameter light beams (at 20p.m times and can hold its state indefinitely 32X64 -element arrays, as s town here. spacing) and a differential output that if supplied with 200nW of optical input yields modulated beams with contrast per half -cell. ratio of 5:1. But why go to all these lengths to do Invented originally in 1984 by AT&T. with light what can easily he done the S -SEED has been perfected to the electrically? The answer, as hinted point where 2048 of the 20µmx4µm earlier, lies in the massive parallelism cells can he reliably fabricated on a made possible by what Chirovsky single gallium arsenide chip. The only describes as "free -space" optics. electrical connections are bias voltage Because light can reach the input of a and ground terminals. Increasing the device with the minimum of ohstruc-
Continued on page 270
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April l9yp ELECTRONICS N ORLO+WIRELESS WGRLD 269 RESEARCH NOTES Cl C' 1 = Leo Chirovsky, of AT&T Bell ,'"-E111-11 Laboratories, uses a microscope and prober to test the photonic array. The 411- monitor, top centre, displays what he sees.
Lion, it means that in theory any cell in a '1r machine can communicate directly with systems any other cell. No longer should .,C. designers he restricted to chips with 40
pins or to serial data buses. This of 1 . course opens up the possibility of new system architecture of a sort that simply
hasn't been possible using electronics. 1 't In practice the new AT&T S -SEED o t- chip is ideally suited to large experimen- tal systems since, being a reflective ).. device. the inputs and outputs are co -sited. This in turn allows for easy i heat -sinking from the rear of the - package. AT&T Bell admit that such whole photonic systems are a long way off, but given the availability of experimental devices. they are confident that development will now press ahead. I certainly look forward to the intriguing a of prospect of computer consisting ' r nothing hut an empty space hounded by walls papered with ICs flashing at each .7:b other.
What flu in on the (solar) wind Over the last few decades there have an idea it would probably pass been attempts to correlate the sunspot unnoticed in the scientific literature. As cycle with a wide variety of seemingly it is. influenza experts around the world disparate phenomena. These include have expressed considerable scepti- the population of polar hears, the length cism. claiming that 'flu can spread quite of women's skirts, the quality of vintage well without any help from the Sun. On and even the number of Republicans in the other hand. no theory apart from the US Senate. The latest addition. that of Hoyle and Wickramasinge seems though with much more scientific cred- to explain the fact that a 'flu epidemic ibility, is influenza. can spread around the globe in a matter Professor Sir Fred I loyle and his col- of weeks or months at the most. Sir Fred league Professor Chandra Wick- believes that 'flu viruses hang about in ramasinge of the University of Wales, the upper atmosphere, rather like vol- famous for their earlier claims that vir- canic dust. This is because they are uses may emanate from space. have extremely light particles. When the Sun tides drive the viruses downwards on to now found new evidence (Nature Vol. is on the boil the electrical fields pro- the heads of us unfortunate mortals. 343 No 6256) that 'flu pandemics coin- duced by the streams of charged par- When asked (in an interview on the cide with the peak of solar activity. BBC World Service programme Science This idea isn't entirely new, having in Action) why we don't all succumb to / the 'flu. Sir Fred explained that other originally been proposed 12 years ago (I lope -Simpson. RE. Nature Vol. 275. factors also come into play. Not only in 86). What I loyle and Wickramasinge does the virus come down to earth have done is to extend the study hack little patches. but its descent may he into the 19th century to cover a total of modulated by meteorological factors 17 sunspot cycles. They note, more- such as heavy rain or fog. Sir Fred a over. that since I lope-Simpson's origi- believes that combination of foggy nal work there have been two further weather and a sunspot maximum is the sunspot cycles, the 1979 one coinciding worst possible 'flu risk. Next time. fairly well with the infamous worldwide therefore, you see the aurora draped outbreak of "Red flu". with a veil of mist, get indoors quick! On the face of it the evidence is And (as with Met. Office gale warnings) impressive. Indeed, if it weren't so zany don't say you haven't been warned.
270 ELECTRONICS WORLD+\VIRELESS WORLD April 1990 Leader Signal Sources -..,- . . 15- - - 140.000 ,:. . - C d " - ma? ^ el la -7- t_ó Zs, r' e 0oer ¡run fr eitt tri:_iz eti ' Mu 1±Dczycl F±1
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April 19911 ELECTRON I( .5 WORLD + WIRELESS WORLD 271 RESEARCH NOTES Sun on the boil As you read this, the Sun will have charged particles. Billions of tons of maturely. Friction from the expanding reached what is generally expected to be plasma shoot Out into space at speeds in atmosphere was also why NASA had to the peak of solar cycle number 22. So far excess of three million km/hr. I-lere on get its skates on to recover LIEF-the it's been the most active cycle ever Earth the effects can he dramatic. A Long Duration Exposure Facility. What recorded and there's clearly much more year ago on March 10th a powerful flare has disturbed the space industry in a to come. despatched a blast of `C -rays which. somewhat less spectacular way has been Traditionally the sun has been eight minutes later. ionised the D -layer the high incidence of data errors caused regarded as a somewhat placid, run- of the ionosphere. causing massive dis- to orbiting electronics. A single out- of-the-mill G -type star. with a fixed ruption to 1 I communications. Over pouring of solar protons last October energy output described as the solar the following few days this was followed led to hundreds of soft and hard faults. constant (1.35k W/m'- at the Earth's sur- by a bombardment of protons and Radiation exposure to astronauts is face). Recent observations by the ill- electrons which led to spectacular another question that is hound to he fated Solar Max satellite suggest how- auroral displays. But solar particle bom- raised as solar cycle number 22 coughs ever that the solar constant is not con- bardment and the million -ampere cur- and splutters its way ahead. stant but steadily varying by as much as rents induced in the ionosphere have Now may he the theoretical maxi- 0.1%. Other studies indicate that the other effects much less benign, scarcely mum but there's good reason to expect whole of the Sun may be ringing like a surprising when you consider that a big problems for a good few years to come. gigantic bell with seismic waves that dis- solar flare emits enough energy BBC research has, for example, shown tort the magnetic field and which may to supply a big city for an estimated 200 mat geomagnetic ui: turhances. with
give rise to the I I -year solar cycle. million years. hs,tr consehuent effectton ionospheric Be that as it may. the cycle is charac- Already in this solar cycle. pc raj propagation. tend :o occur most terized by a periodicity in the number of transient magnetic fields rrequepliy a few year, after the sunspot
sunspots visible on the surface. These showers have been blame r 1 ng maoitrium. blemishes. often as big as a hundred out Montreal, `h ' undung adiation I' epare for the worst ,Then. hut earths, are areas of intense magnetic alarms in «o >c rr''e "wee shut; re.member that even the'n>Igst violent activity that interfere with the way tle and for crvusitils QeraMé dame disturbances reflect only tl'_ merest rip- charged particles conduct heat from the to solar cells iowcrmgthe Venus -bound ple on the surface of our a'tiu ling uni- Sun's interior. That's why sunspdt,are Magellan seare'eyátyWo till, th versal power supply. The Odd hiccup on cooler than the surrounding arco_ tar, anexpec,,c'dh, large obyppurin rut tsíla the Sun is perhaps scarcely surprising from being inactive parts of I Sun cleated up me Earth't arr..o- when you consider that it gobbles up 600 however, these spots drive i pry.)-,-, spl- causing it to expand. This, iron- million tons of hydrogen every second cesses that lead to solar r are r..; ically. is why Solar Max, the satellite put and runs at a core temperature esti- immense outbursts of ene up to study the Sun, re-entered pre- mated at 15 million degrees Celsius!
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Motorola in processor bloodbath
US chip maker Motorola has unveiled floating point co -processor. separate includes a dedicated hardware its latest 32 -hit general purpose data and instruction caches and multiplier (64x8). The floating point microprocessor. the 68040. memory management all on the same unit is object -code compatible with Motorola's 1.2 million transistor piece of silicon. both the 68881 and the 68882. monster weighs in with around 20 The arithmetic processor is although it executes the code five to million instructions per second of raw optimized to deliver between ten times faster than the 68882. processing power. is clocked at 25MI Iz 19-21 mips. Rise design features and The floating point unit can deliver and uses 0.8 -micron c-mos chip - parallel processing have been used to 3.5 million floating point operations making technology. bring the execution time down from per second (MFLOPS) in sustained I lowever. these statistics are no around the 3.4 clock cycles per performance in double precision guarantee of success nor even survival. instruction required in the 68030 to Linpack. The unit chews maths at The 32 -hit market is fast turning into a around 1.3 cycles per instruction in the 8MFLOPS when pushed to peak bloodbath with Motorola Lacing stiff 6804(1. performance. according to Motorola. competition from arch -rival Intel as This major redesign of the processor The 68040 includes two 4Kbyte well as from a clutch of companies core manifests itself in the integer unit cache memories: one for data and one with fast risc chips. which is object -code compatible with for instructions. They help the chip to The risc merchants are eating into other members of the 68000 family run fast by feeding information to the Motorola's traditional workstation rather than hi nary -code compatible. execution units as fast as the\ can use business while Intel has the personal But the chip can still run all the 32 -bit it. They work simultaneously to shift computer market sewn -up. So software written for its earlier cousins. information at a rate of 200 bytes per Motorola is positioning the 68(1.40 as The floating point unit is basically a second. an up-market workhorse for multi-user redesign of the company's 68881 and The organization of the caches is minicomputers. Which pitches it head - 68882 maths co -processor chips which four-way set -associative and allows to -head with Intel's 80486. have been placed onto the same piece four long words per cache line. This Motorola engineers have used the of silicon as the main processor. means write operations can he enormous transistor count to cram Frequently -used instructions have buffered or copied hack and allows circuitry into the 68040. The device been implemented in chip hardware cache reads and writes to he bursted includes an arithmetic processor, a and the rest executed in software. It efficiently. The claimed instruction hit rate is 93 per cent. the data read hit v ! _, rate 92 per cent and the data write hit rate 93 per cent. «.~ 1 ` fc The data cache also supports bus ow .1--^+ r. , ;: is a fancy ,,,. . lee snooping. which way of 1. saying that it makes sure the data cache is consistent with the ,g_...,.._.-_-__. .4. external ii I _ memory without software r iI I : -` intervention. The caches also alleviate r I. ¡I4z ' ¡oil- the load on external d -ram memory : ''t'fi .. /i11. :ú !4;ST,11- . 1FC chips and so helps to cut system costs. ,- f' ' ' r.141:-;,;; j'i«O-`; The 68040 also has two separate { I,,, ti0_- paged memory management units operating concurrently with the caches T1.1. .. ,,r;u .l,_ r- ,r to provide simultaneous instruction ar" t'91 1 .,. . and operand address translation. lio i `6C ' IEa- U+rr+wl-1 ;,., The 25N' Hz version of the 68040 is t U : currently being sampled at around i 9. , ; r > $795 each and will he available in I 1 volume in the summer. Motorola is j promising faster versions clocking at 33MHz and 50M1Iz in the future. i !u It is also working on the next generation chip: the 68050. .f 1 Motorola sources say its device will probably ;10::j '111,'111111111I ; J incorporate 0.5 -micron or even 0.25 - ' micron triple -level metal c-mos. ier M 111" support 15 million transistors and be clocked at more than 300MHz. It should be here by the mid-I990s: which gives us a few years to figure out what we could do with it. W8888 ES: 65Dti BStY'iFi'fi Leon Clifford
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CIRCLE NO. 123 ON REPLY CARD
April 1990 ELECTRONICS WORLD + WIRELESS WORLD 275 UPDATE Computing by light
The first ever digital optical processor 'on' or 'off'. According to AT&Ts quantum physics dominates over has been developed by scientists Anthony Lentine. the S -SEED is conventional electrical theory. It acts working for the Bell Laboratories of versatile and can function as either a as an optically bistable device when it US communications giant AT&T. dynamic or a static memory. It can is electrically biased through a load. The device, comprising four also act as a Nor logic gate or a basic When a small bias voltage is applied separate optical chips. is clocked at optical switch. between the p and the n contacts, the around 1MHz and breaks no speed AT&T reckons that an S -SEED can structure can regulate the intensity of records but it does hold out the switch on or off in less than a billionth a light beam passing through it. This prospect of extremely fast optical chips of a second when it is illuminated by a bias voltage is the only electrical input in the future. Such chips could low power beam of light. And very needed for Bell Labs' processor chip, revolutionize computing and little optical energy is needed to keep which in all other aspects is totally electronics because they could process information stored in an array of optical. faster than conventional circuitry. S-SEEDs. The difference between an S -SEED Not only does light travel faster At the end of the last year, Bell and a SEED (a predecessor of 1984 than electrons. but it can be split up Labs unveiled a single gallium vintage) is that an S -SEED uses two into many beams which can each do a arsenide chip sporting some 2048 modulators per element biased in different job. So optical chips have S -SEED elements. The device could series, each acting as the other's load applications in fast parallel processing process 2Kbits of optical information (and hence the 'S' for symmetrical), computers, high -capacity links in parallel, twice that of any other whereas a SEED uses one modulator between electronic components and optical device on the market. AT&T is per element. In simple terms, signal processing in optical -fibre selling samples of the device to S-SEEDs are better suited for packing communications systems. interested parties. into large arrays. The Bell Labs' digital optical Essentially, S-SEEDs are reverse There are four arrays of 32 microprocessor uses four monolithic biased p -n junction diodes with some S-SEEDs in the Bell Labs' gallium arsenide chips. Each fancy solid state physics between the microprocessor. Each array measures incorporates 128 basic opto -electronic p -contact and the n -contact. The fancy some 1.3mm on a side and also elements called symmetric self electro - hit consists of alternating layers of includes two 10mW semiconductor optic effect devices (S-SEEDs); these gallium arsenide (GaAs) and gallium laser diodes which generate the many are the fundamental building blocks of aluminium arsenide (GaAlAs). Each beams of light needed to make the optical chips, just as transistors are the layer is only a few atoms thick and is chip work. fundamental building blocks of laid down by molecular beam epitaxy. The output from one array serves as conventional electronic devices. This GaAs/GaAlAs sandwich forms the input for the next; so the logic Like logic gates, S-SEEDs are what is called a multi -quantum well state of the S-SEEDs in an array is binary in their nature; they are either structure and is a region where determined by the state of the S-SEEDs in the input array. The Making an adjustment to the world's first optical processor: optical processor carries out Michael Prise of AT&T. calculations by changing the on -off
t - status of the switches of S-SEEDs on .. successive arrays. ,r 12 - The four arrays of S-SEEDs are separated by lenses and masks that are - ._ analogous to yy / interconnection between / Cr ., ' e. ' I logic gates in electronic devices. The ' ' i r I, masks are essentially glass panes with e. ._ . regular patterns of transparent and ~ , ,t opaque spots that can either block light or allow it to pass. The pattern determines the connectivity - the logic J(/* .._ - of the machine. vQ_.. ', S-SEEDs measuring some 40 -microns by 20 -microns are bigger than transistors but they are getting smaller all the time, according to Bell Labs' optical chip researcher Dr Mike Prise. S-SEEDs can be switched much faster than 1MHz, according to Prise. "These S-SEEDs have worked at a 1GHz and similar devices have worked at 20-30GHz," he said. "What we've got is a really simple system operating at MHz
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CIRCLE NO. 125 ON REPLY CARD
277 April 1990 ELECTRONICS WORLD+WIRELESS WORLD UPDATE
Input Array Laser Diode SEED Output Input
JID - Mask Input Output' Y Output Inpu Input Output Optical Optical Light doesn't have capacitance: the system looks clumsy compared to silicon Logic H but Logic chip it could work much faster. Gate Gate
frequencies," said Prise. "In four or optical devices on the same silicon technology would allow this signal five years we may have something real substrate as conventional circuitry. processing to he done optically. to show people. Right now we can "It removes the pin -out bottleneck "IOGhits is about the maximum that design things on paper that look like that limits the speed of integrated we can deal with at the moment," said plans for useful systems that we can circuits," said. Midwinter. "At the Midwinter. "Optical technology will think about building." moment we design our circuitry allow us to take that data rate up to Prise points out that S-SEEDs are a around this bottleneck, but once it is terabits." low energy technology. "And you can gone we will be able to design our This is the one area where AT&T make small ones with about the same circuitry to run faster." will he focusing a lot of research energy density as c-mos chips." he The other important applications effort; after all it is a added. area is in telecommunications where telecommunications company. Bell Labs' breakthrough is high -capacity optical -fibres mean that So although enormously powerful undeniably impressive; hut don't let gigabit data rates must be processed in supercomputers may sound sexy, it's stories about 1000 -Cray equivalent real-time; and these data rates are the terribly dull and mundane go computers to your head. There's a growing. practicalities of coping with optical - lot of steam left in conventional Conventional systems translate the fibre data rates and getting chips to electronics, and at much lower prices. optical signals into electronic ones, talk to each other that will really "Compared to what has gone process them and then retranslate benefit from Bell Labs' breakthrough. before, this is a big step forward." said them back into light. Bell Labs' Leon Clifford optics expert Professor John Midwinter of University College London. "But its not unreasonable to say that in the region of computing. this won't have a big impact." High speed action defeats He agrees that optical chips hold out the prospect of very fast highly rogue disks parallel computers. "But in the cold light day its of hard to see what you Between 8 and 12 December 1989. the print were such phrases as "There can do with optical computers that you somewhere in excess of 15.000 is a mandatory leasing fee for the use can't do with silicon." said Midwinter. floppy disks were mailed to computer of these programs; they are not However, there are two very special users across the UK, Europe, provided to you free of charge" and areas where the Bell Labs technology Scandinavia. Southern Africa and "If you install these programs on a may have applications: electronic Australia. microcomputer- ... you thereby agree interconnection and communications The disks, from a company called to pay PC Cyborg Corporation in full systems. PC Cyborg Corporation, contained a for the cost of leasing these programs." One of the problems with getting program written to evaluate a user's The reader was further informed chips to talk to each other is that as risk of contracting the HIV virus that in the event of a breach of the clock speeds creep higher. capacitance according to answers given to a series licence agreement. PC Cyborg gets to be a bigger headache for of questions about the user's life-style. Corporation reserved the right to use electronic engineers. "We could The disks were very cheap 5.25in what it called "program mechanisms'' these integrate optical devices with floppy disks with professionally - to ensure "termination of your use of silicon and use them for silicon gate printed labels and were mailed in the programs". There followed a interconnection," explained Prise. white envelopes to names taken from warning that these program Ile points out that optical pin -outs various mailing lists. Each envelope mechanisms would adversely affect don't charge -up. The trick will be to contained the disk and a small sheet of other program applications on embed optical circuitry on the same paper which gave details of how to run microcomputers. Whether or not this chip as electronic circuitry. the program. licence "agreement" or any of its Professor Midwinter reckons there On the reverse of this sheet, in conditions are legal is still being are two ways to do this: either take almost impossibly tiny print, were debated. particularly since this disk the silicon and grow the GaAs optic details of "Limited Warranty" and a comes under the heading of on top, which is very difficult: or grow "Licence Agreement". Buried within unsolicited material.
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CIRCLE NO. 127 ON REPLY CARO
279 April 1990 ELECTRONICS WORLD + WIRELESS WORLD PROGRAMMING
is a medium -level program- ming language developed by Dennis Ritchie of Bell Lab- oratories and implemented there on a PDP-I1 in 1972. Historically. C was preceded by B. a language written by Ken Thompson in 1970 for the first UNIX system run on the PDP-7. B. in turn evolved from the Basic Cambridge Programming Lan- guage BCPL. Developed by Martin Richards at Cambridge in 1967 as a sys- 1 tems programming language. The C Programming Language: Pren- tice Hall 1978. by Brian Kernighan and Dennis Ritchie is the definitive text. Although it is not adopted as an interna- tional standard, it is generally accepted as standard C. This original and enigma- tic text is not an introductory program- ming manual: it assumes familiarity with basic programming concepts such as variables. assignment statements, loops and functions - and is probably best read once you have mastered C. The increasing popularity of the lan- guage has encouraged numerous less esoteric works, many attempting to sim- 4 4 plify the original Kernighan and Ritchie text. Each of these introductions has its relative merits: no doubt you will make your own choice and find what suits you hest. I have included a short biblio- graphy of texts which I found par- ticularly useful.
Properties and background The versatility of C allows it to be run on personal 8 -bit computers or the Cray -1. one of the worlds fastest computers. Designed to make programs fast and INTERFACING compact, this portable assembly lan- guage was used to program the remarkable computer -animated sequences in Return of the Jedi and Startrek II. In many cases programs WITH C written in assembly language for "effi- ciency" have been outperformed by Fed up with whimsical microprocessor code but need its comparable programs written in C. Despite being a medium -level language speed? The C language may provide an answer. This it still embodies advanced structural series of articles, directed towards electronics programming features normally associ- engineers, demonstrates the role of the language in ated with high-level languages such as Pascal. C is a concise language and small connecting microcomputers to the real world. By can be beautiful when programming. It Howard Hutchings. has a particularly rich set of operators, ideal for configuring programmable input-output devices and flag testing. The purpose of these articles ís to teach those aspects of the C language
280 ELECTRONICS WORLD+\V IIZELESS WORLD April 1990 PROGRAMMING
8255 Block diagram
Power +5V you will require to interface effectively. Group A supplies GNU Group A I/O Port A Our strategy is to teach C program con- Control Y PA? PAo (B) structions as we go along, presenting the information in "byte" sized packets ill an attempt to make it more attractive and digestible. We have tried to orga- nize the programs in a progression of Group A Port C I/O complexity. so that each program pre- PC7PC4 Bidirectional upper (4) f46 sents a new feature of C or an alter- data bus Data native program construction. Where D7Do< bus possible the construction is illustrated buffer 8 Bit internal data bus Group B with a flowchart and the program liber- I/0 PortC ( PC3PCo ally littered with comments to aid lower (4) comprehension. All the program examples presented have been tried and tested on an IBM ROTC a Read/ PC clone using Microsoft C compiler WR--C Group B write Group B version 5.1. The emphasis is on effective Port B I/O control Control C IP87PBo interfacing rather than elegant pro- Ao logic (8) H gramming. Where possible I have Reset included alternative program con- structions in an attempt to demonstrate the flexibility of this remarkable lan- Cs guage. The text encourages you to run the programs and experiment with C. of the programs Inevitably some Fig. 1.1. Intel 8255 programmable port lengthy, which tends to dis- Pin configuration become used as a programming model in the courage even experienced program- early stages of this series. PA3 CT-"\ --T-47) mers! To maintain interest the PA2 C 2 39 3 PA5 fundamental construction is presented PA1 C 3 38 JPA6 PAO C 4 37 3 PA7 separately. Most programs exist to be reduced to that of reading ones and RDC 5 36 J WR zeros from a peripheral connected to an rewritten: and if after working through ESCGND 6 35 :Reset data and the examples you cannot do better. I'll input port-processing the C 7 34 JDo be disappointed. finally writing the re -ordered data to the Al C 8 33 JDI AO 9 32 302 Rather than design and build our own outside world through an output port. C Here's the catch: how do you find the PC7C 10 31 303 interface circuits we chose to use the PC6 C 11 8255 30 304 I1O Blue Chip Technology data acquisition available space: format the control PC5 C 12 29 705 and control cards. These plug in cards word: control the I/O card: process the PC4 C 13 28 JD6 PCOC 14 27 307 are port mapped and may be driven by data'? Unfortunately , unless you are an PC 1 C 15 26JVcc language pro- any language. simplifying the task of experienced assembly PC2 C 16 25 JPB7 interfacing - allowing us to concentrate grammer these objectives represent for- PC3C 17 24 J PB6 more effort and attention on the pro- midable assignments. Instead of aiming PBO C 18 23 J PB5 for "the best possible design", we will be PB1 C 19 22 31:134 gramming aspect of the problem. PB2C 20 21 JPB3 content with the "best design possible" Fundamental interfacing and use C to get very close to the target The primitive concept of sending hit machine. Pin names
patterns to the outside world can pro- 07-Do 1 Data bus (Bi dvectional)
i -
duce remarkably sophisticated Reset , Reset input electronic projects with the minimum of Programmable input-output CS `}~Chip select hardware. principally because much of devices RD I Read input the problem is soled using creative Communication between the real world input software. Imagine an Exocet missile and a personal computer is through the WR Write skimming low over the waves as it ports of the peripheral interface adapter AO,A1 Port address homes in on its target. On board, the (PIA) or versatile interface adapter PA7 PAO Port A(bit) computer receives data from the mis- (VIA). These relatively complex and PB7PBO' Port B(bit) sile's transducers through the input specialized chips can he programmed to PC7PCO Port C(bit) port. The data is processed in real-time behave as input-output devices and Vcc +5 Volts and the result used to control the trajec- effectively buffer the data bus from the GND J 0 Volts tory in anticipation of a successful controlled peripheral, thereby protect- strike. Despite the complexity of the ing the system. Employing memory task the fundamental problem can be mapped input-output ensures that the
April 1991) ELECTRONICS WORLD +WIRELESS WORLD 28 I PROGRAMMING
CPU "sees" the ports simply as a collec- port depending on the mode selected. The operation of the I/O ports is con- tion of addresses, indistinguishable In mode 0 ports A and B operate as trolled by the format of the 8 -bit word from any address in memory. Provided two 8 -bit ports, whilst port C is operated written to the control register, located the input-output device is configured as two 4 -bit ports. This mode supports at address (Base + 3). The control word carefully, bi-directional communication simple data transfers without format is shown in Fig. 1.3. Simple can be made almost routine. In effect handshaking. input-output operations, without hand-
the operation of these devices are ana- In mode 1 ports A and B may be shaking, require the control word to be logous to constructing electronic cir- configured as either input or output. configured in mode 0. Table 1.1 repre- cuits without ever using a soldering They cannot be defined individually on sents the mode 0-port definition chart; iron, simply because the necessary con- a line by line basis as with the ports of which should he an effective source of nections are made by placing the certain other programmable I/O reference when consulting the example required bit patterns in the appropriate devices. Six bits of port C are set aside programs. control registers. for handshaking and interrupt control. The Blue Chip data acquisition sys- Unfortunately each microprocessor Mode 2 uses the eight lines of port A tem, used as a teaching example in this manufacturer appears to have adopted for bi-directional data transfer. Hand- series of articles. provides 48 I/O lines a particular programmable input-out- shaking is provided by the five most sig- by port mapping two 8255s on the same put device to suit their own system. As nificant bits of port C. plug-in card. The ports are terminated with microprocessor instruction sets, in a single 50 way connector at the rear familiarity with a particular device tends Programming of the IBM PC. Bus contention is to make the user patriotic and reluctant the 8255 avoided by making the base address to change. Despite the unique features The programming model of the 8255 selectable in the range 300H to 3FFH. of many of these devices. certain consists of four 8 -hit registers, ports A. the prototyping region. characteristics remain common, making B and C and a control register. Depend- the transition from the comparatively ing upon where you locate the device in primitive programmable peripheral the available I/O space. the register IBM PC bus interface PPI. such as the Intel 8522 to model appears as four contiguous As shown in Fig. 1.4 the PC -XT bus is the complex and complicated MOS addresses as shown in Fig. 1.2. an 8 -bit data bus implemented in a Technologies 6522 VIA relatively 62 -pin edge connector. Many of the bus painless. signals are used for direct memory To explain the adopted interfacing Address Function access and interrupt handling and may protocols with any clarity it was neces- be ignored at first reading. sary to be chip specific. Unfortunately Base Port A The address bus lines AO-A19 can
this dates the text. although the funda- address up to 1 Mbyte of address space. Base +1 Port B mental concepts will remain current for Although the 8088 processor can use all 16 some time to come. Base + 2 Port C lines AO -A l5 to access 64Kbyte of 1/0 space. only 10 lines AO - A9 are Base +3 Control register actually decoded restricting the number 8255 programmable of available ports to 1024. Many of the peripheral interface Fig. 1.2. 8255 programming model. available 1/0 locations have been The Intel 8255 programmable peripheral interface PPI in Figure 1.1 is a fairly simple port chip. This parallel Table 1.1. Mode 0 port definition chart. rather venerable design was one of the In this mode, simple input and output operations for each of the three ports are provided. No "handshaking" earliest interface adapters on the mar- is required; data is simply written to or read from a specified port. ket, originally intended for use in the No. Control Word 8008 and 8080A systems. hut now Bits Group A Group B Port C Port C enjoying a resurgence of popularity on D; D6 DS D, D3 D2 D, Do Port A Port B (Upper) (Lower) account of the ease with which it inter- 0 1 0 0 0 0 0 0 faces to the IBM PC bus. which is effec 0 OUTPUT OUTPUT OUTPUT OUTPUT 1 1 0 tively the bus for the 8088 processor 0 0 0 0 0 1 OUTPUT OUTPUT OUTPUT INPUT
2 1 operated in the "maximum mode". 0 0 0 0 0 1 0 OUTPUT OUTPUT INPUT OUTPUT
Large scale integration ensures that par- 3 1 0 0 0 0 0 1 1 OUTPUT OUTPUT INPUT INPUT
input-output be 1 allel operation can con- 4 0 0 0 1 0 0 0 OUTPUT INPUT OUTPUT OUTPUT centrated into a single 40 -pin package. 5 1 0 0 0 1 0 0 1 OUTPUT INPUT OUTPUT INPUT Making the chip software configurable 6 1 0 0 0 1 0 1 0 OUTPUT INPUT INPUT offers the flexibility of deferred design - OUTPUT 7 1 1 the values placed in the control register 0 0 0 0 1 1 OUTPUT INPUT INPUT INPUT determine which groups of lines are 8 1 0 0 1 0 0 0 0 INPUT OUTPUT OUTPUT OUTPUT
9 1 1 inputs and outputs. 0 0 0 0 0 1 INPUT OUTPUT OUTPUT INPUT
Communication between the micro- 10 1 0 0 1 0 0 1 0 INPUT OUTPUT INPUT OUTPUT
and the real is 11 1 computer world through 0 0 1 0 0 1 1 INPUT OUTPUT INPUT INPUT the 24 input-output lines. These are div- 12 1 0 0 1 1 0 3 0 INPUT INPUT OUTPUT OUTPUT ided into two groups of eight lines. data 13 1 0 0 1 1 0 0 1 INPUT INPUT ports A and B, together with two groups OUTPUT INPUT 14 1 1 1 1 of four lines - forming port C. Port C 0 0 0 0 INPUT INPUT INPUT OUTPUT 15 1 1 can either be a data port or a control 0 0 1 0 1 1 INPUT INPUT INPUT INPUT
282 ELECTRONICS WORLD + WIRELESS WORLD April 1990 PROGRAMMING
Control word
I 1 07 D6 D5 04D302D, 1D Signal name Rear panel Sinai name
GND 81 Al 1/0 CH CK LJ +Reset DRV B2 A2 +07 / Group B +5V B3 A3 +06 +IR02 B4 A4 +D5 Port C (lower) -5v DC B5 AS +D4 1 =Input 86 A6 +D3 0=Output +OR02 -12V 87 A7 +02 A8 +D1 Port B Card SLCTD B8 +12V- B9 A9 +DO 1 =Input BIO A10 - +1 /O CH RDY 0 =Output GND- -MrEMW- 811 A11 - +AEN Mode selection -MIEMR- 812 Al2 -+A19 O= Mode O -10w- B13 413 -+A18 1 = Mode 1 -10R- B14 414 +A17 -RACK 3- B15 A15 I-- +A16 +DR03 B16 416 +A15 Group A - - 417 -OACK1 817 -+A14 +DR01 1318 A18 +A13 Port C (upper) - 419 -DACKO-- 819 -+Al2 1 = Input Clock- 820 A20 +411 0 = Output - +IR07- 821 A21 -+A10 Port A iIR06 B22 A22 -+A9 - A23 +A8 1 = Input +IR05- 823 +IR04 824 A24 - +A7 Or Output - B25 - Mode selection +IRQ3- A25 +A6 -DACK2 B26 A26 - +A5 00= Mode 0 - B27 A27 ------+A4 1 - 01 =Mode +T/C- 1X =Mode 2 +ALE- 828 428 +A3 +5V- B29 A29 -+A2 +OSC- B30 430 +Al Mode set f lag GND- 831 A31 -+A0
1 = Active
Fig. 1.3. Control word bit function for 8255. Fig. 1.4. /BM PC bus structure.
adopted by IBM for their own purposes, of pointers-which are tricky until you Table /.2. Address space for IBM I/O these assigned locations being shown in get used to them. However, pointers devices. Table 1.2. Despite the crowded nature cannot be used to access I/O devices in IBM PC He address Use of the I/O space there are several ports computer systems such as the range in the which a address space for available, particularly prototype have separate 000-OOF DMA chip 8237A-5 region 3001-1-31FH. However, certain I/O devices. IBM has allocated 020-021 Interrupt 8259A peripheral board manufacturers have addresses in the range 768 to 799 (den- 040-043 Timer 8253-5 060-063 PPI 8255A-5 monopolized some of these addresses ary) specifically for I/O prototyping. 080-083 DMA page registers for their own products, which means See Table 1.2. OAX NMI mask register must look elsewhere for 110 space. C compilers for machines with this OCX Reserved you OEX Reserved Clearly one simple solution is to use type of I/O system usually include 200-20F Game control unoccupied assigned I/O locations. library functions, which allow direct 210-217 Expansion unit 220-24F Reserved access to the port -mapped I/O space. 271i -27F Reserved Accessing specific memory For example. the Microsoft C compiler 2F0-2F7 Reserved Asynchronous communications inp( ) 2F8-2FF locations with Basic and C version 5.1 provides the functions (secondary) Before you can interface successfully and outp( ) defined in the header file 300-31F Prototype card with C. it is first necessary to access data conio.h. By incorporating the addi- 320-32F Fixed disk 378-37F Printer from specific memory addresses. tional compiler directive 380-38C' SDLC communications Rather than ruthlessly present the #include
April 1990 ELECTRONICS WORLD + WIRELESS WORLD 283 PROGRAMMING
Believing that one picture is worth a thousand words we intentionally Extract from GW-Basic and Microsoft C programmers manuals. include the lighthearted Fig. 1.5 as a reminder of how to access port -mapped POKE OUT data using GW-Basic and Microsoft C. Statement Statement These illustrative programs do not Syntax Syntax POKE address. byte OUT 00f0 data include any initialization protocols. Action Action Writes a byte Into a memory location Sends a byte to a machine output port Remarks Remarks The arguments address and byte are integer The pod is the port number. It must be an integer expressions. expression in the range 0 to 65535. The expression address represents the address of the memory location and byte is the data byte. The byte The dala argument is the data to be transmitted. It must must be in the range 0 to 255. be an Integer expression in the range 0 to 255. Example The address must be In the range - 32768 tO 65535. 100 OUT 12345, 255 The address is the offset from the current segment, which was set last by the DEF SEG statement. For In 8086 assembly language, this is equivalent to: interpretation of negative values of address see 'VARPTR Function." MOV DX 12345 MOV AL. 255 The complementary function to POKE is PEEK. OUT DX, AL
Warning Use POKE carefully If it is used incorrectly, it can cause the system to crash. Fig. 1.5. Peeking and poking.
See Also Example 1 DEF SEG. PEEK. VARPTR 10 Example REM PEEKING I/O 10 POKE 8115Á00, BMFf 20 P = INP(768):REM READ PORT A 30 PRINT P PEEK INP Example 2 Function Function 10 REM POKING I/O Syntax Syntax 20 OUT 769,50:REM WRITE PORT B PEEK(nf INP (porn Action Action Example 3 Returns the from byte the Indicated memory location n Returns the byte read from port. The port Remarks must be an integer in the range 0 to 65535 The returned value is an Integer in the range 0 to 255. Remarks The PEEKING I/O WITH C integer n must be in the range - 32768 to 65535. INP is the complementary function to the OUT Then argument is the offset from the current segment, statement. which was defined by the last DEF SEG statement. For See Also #include
Continued over page
284 ELECTRONICS WORLD+ WIRELESS WORLD April 1990 I . ou
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statements, i.e. the source code, are not and should always he included to euar- made up of the principal function main() executed directly as with interpreted antee successful compilation. C heck the together with any nested functions. The languages. Instead they are written to a C compiler manual for the precise syn- example in listing 1.2 is probably the file called the source program. using a tax for your particular system. Some most primitive C program imaginable, text editor or word processor. The compilers require #include"stdio.h" or where the code located inside the braces source program is then processed by the #include
main( ) { Yes port = 1; Errors byte_val = 3; outp (port, byte_val); No printf ("The value Yod has been output to port %d", byte_val, port); C Done } This program uses outp to write the value 3 to output port 1. Fig. 1.6. C program development. inp, inpw Summary It is rewarding to examine the general structure of all C programs before # include
The inp and inpw functions read a byte and a word, respectively, from the specified input port. GENERAL STRUCTURE OF ' The input value can be any unsigned integer in the range 0-65,535. ALL C PROGRAMS Example #include
} { Input a from The anatomy the program is made /' byte the port: 'I of result = inp (port); up as follows: #include
286 ELECTRONICS WORLD + WIRELESS WORLD April 1990 PROGRAMMING
the monitor is straightforward, as ble's data type in advance. Certain data read from eight logic switches con- shown in listing 1.3. types, for example int and char are pro- nected to port A. the other ports cessed more quickly as the program remaining unconnected. The logic sta- Listing 1.3 executes and it is good practice to main- tus will be displayed in denary on the tain only sufficient precision as is neces- monitor. One possible construction is DISPLAYING A MESSAGE sary. when declaring variables. shown in listing 1.4. USING C Computers do not store floating-point #include
April 1990 ELECTRONICS WORLD + WIRELESS HORLD 287 PROGRAMMING
Table 1.4. Displaying other data types.
d decimal notation Proprammabie peripheral inter face (PPII Visual indication of data To 1 of 8255 PPI o unsigned octal notation port M513 +44V ' L5B x unsigned hexadecimal notation u unsigned decimal notation Z`= .2 _ e. c single character 8 at 270n ./ i!i s string rfll[fll / SB MSB 3mm Red leas IFtype'tOmA e double or floating number in decimal and Mu exponential notation ULN2803A N_5 Octal f double or floating number in decimal notation darhngton driver g the shorter in length of characters, of °ae or %f representation 9 L5B L5B ,r ot c When interfacing, the more primitive Power on/off tont. data types are often useful: x meaning +44V rant. 100nF IN4001 ÍÍ11111r +44V \!. {f +5V unsigned hexadecimal is of particular Swt 680 interest. The way to learn a language is "J1JJ1JJ to use it. rather than simply read about 5mm Led IFtype.4mA it. If you have time, try modifying the 'LIii11[[i.M58 57 ----SO Digital ONO of 8255 PPI a S format of printfO to display the decimal Toggle switches GNO of power supply and hexadecimal contents of the input Single pole -centre off (SPC0) OPDT port. A crude but effective approach would be: Fig. 1.7. 1/0 port demonstration circuit. printf("Decimal No. = °od\r ",contents); printf("Hex No. = %x n",contents); which will print the contents of the input Writing from keyboard to Entering data using scanf() port (for example 128) output port The function scanf() is used to collect Decimal No. = 128 Using the keyboard to enter data. listing data from the keyboard. the data type to Hex No. = 80 1.5 is a useful extension the previous be processed being determined by the Alternatively. the construction: of program. Conceptually the only new conversion character in the control string. In this example the format %d printf("Decimal No. = %din Hex No. = function to learn is scanf(). which com- scanf() %x\n",contents,contents): plements printf() examined earlier. causes to interpret the input Although the characteristics are similar. characters as a denary integer. and store the value Will produce an identical result and scant() is presented in some detail as an at the address of x. symbolised by &x (pronounced illustrates the format: vl meaning new - aid to comprehension. ampersand x). line. To display the decimal and hex- Changing the conversion character of adecimal values horizontally on the Listing 1.5 the control string modifies the input monitor. simply replace newline: 'n with stream as shown in Table 1.5. WRITING TO PORT A ' the tab character: \t as shown. O/P USING THE KEYBOARD ' Table 1.5. Input data types. printf("Decimal No. = %d\t Hex No. = #include
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II
SPECTRUM ANALYSERS RALFE = ELECTRONICS HEWLETT PACKARD 36 EASTCOTE LANE S HARROW, MIDDI ESEX HA2 8DB TEL 01-4223593 FAX (r - 0 -1 T 3.'.: 1 I y" [2211Zi :=: - :=_ a EST. HP182T 855880 I.1500MHZ £2950 35 116026 transistor fixture £395 HP141T 8552B85536 110MHz £2950 YEARS _J 8733A pm modulator £250 HP85666 325GHZ GPIB £251( 529A Logic comparator £275 HP85688 1500MHZ GPIB £158 10529A/10526T Logic troubleshooter £295 MARCONI 2370 110MHz £3500 TEST & MEASUREMENT EQUIPMENT 382A(P) P-band attenuator 0-50db £250 MARCON123B0WB2 400MHZ GPIB £11000 415E swr meter £295 TAKEOA RIKEN TR9305 FFT audio GPIB £3950 ADRET 71006 uP-control ed signal gen' 0 3.650MHz £1950 65í6A power supplies 0-3KV 6mA £250 AMBER multi -purpose audio test set £500 T AKE DA RIKE N TR41 10 10kHz-1700MHZ £2950 70468(07) 2 -pen XV plotter high-speed £1.000 ANRITSU MS31113/1, MI1323E1/1, MH347811 video signal gen £000 IWATSU SM2100 dual charm audio £2000 80186(01) serial data generator £1,000 ANRITSU MS349E video signal analyser £000 5011T logic troubleshooting kit complete £500 AVO CB154/5 electrolytic & rant 'cap bridge £375 400FL mV -meter £325 MARCONI INSTRUMENTS AVO RM160/3 megohmmeter £175 8165A function 1 MHz-50MHz £1.950 2356 2357 level oscillator/level meter £1000 AVO (BPL) RM215 aadc breakdown tester to 12kV £295 3581A AF wave analyser £1.250 AVO (BPL) RM2151-1 addc breakdown tester to 12kV £395 6460 6422 microwave power meter/head £500 855313 110MHz spectrum analyser plug -In £950 BRANDENBURG Alpha II 0-56V £300. 807R 0.30kV £500 6551 FM signal generator 1400.1700MHz £375 7563A log voltmeter/amplifier £250 BRUEL 8 KJAER 4416 response test unit £550 67006 sweeper 1-2G & 12 4-18G plug-Ins £3000 5423A structural dynamics analyser BRUELA KJAER 1405 noise generator £450 £3.000 OA2805A PCM regenerator lest set £750 8405A vector voltmeter £1.000 BRUEL 8 KJAER 2307 level recorder, 25 & 50db pots £2250 TF 124581246 0 -Meter and oscillator £450 BRUEL 8 KJAER 2425 votmeter £350 86408/001 phase -locked signal generator £2.250 TM4520 inductor set f250 IWATSU SM2100B duel -channel spectrum analyser 100kHz £2000 11710 down convener (10kHz) for 86406 £750 TF2013 FM signal generator 800-960MHz £350 NATIONAL VP -9690A noise meter £195 1411.8552/85536 110MHz spectrum analyser £2950 TF2300 modulation meter f200 4204A NATIONAL VP -7702C auto distortion meter (0 01%) £450 decade oscillator C125 TF2300A modulation meter £300 PHILIPS PM3543 logic scope £450 4275A digital LCR meter £3250 TF23008 modulation meter £500 PHILIPS PM539OS 1GHz synthesized signal £1950 86148 signal generator 0 9-4GHz £1250 TF2304 modulation meter, generator automatic £400 PHILIPS PM5534 standard pattern generator NTSC £2500 8640B/002 signal generator £2850 TF2305 modulation meter, digital £3750 PHILIPS PM5539 TV colour analyser £1250 8568B 1 5GHz :.pectrum analyser £15000 2435 2GHz counter, Xtal oven option £500 PHILIPS PM5545 colour encoder PAL £1000 53828 225MHz frequency counter £150 TF2501 power meter 0.3W Isd DC-1GHz £150 PHILIPS PM5597 VHF modulators £250, PM5598 UHF £500 53526 40GHz frequency counter option 010 £5000 TF2600 millivolimeter AF ImV-300V Isd £75 PHILIPS PM5190 synthesized function generator £750 TF2600B video voltmeter 1mV-300V fsd £175 PHILIPS PM5560 TV demodulator PM5548 level meter
TF2604 electronic multi -meter £150 I PHILIPS PM5580 F. moculator £1000 ADDI-IONAL EX -STOCK T & M KIT TF2807A PCM multiplex tester £400 PHILIPS PM6668 1 GHz HI -res' counter TCXO opt £295 £1.500 282882829 digital simulator/analyser PHILIPS PM8043 XYT plover A4 size £150 ROHDE & SCHWARZ SWOFIII videoskop £4000 2833 digital in -line monitor £275 RACAL 9081 signal generator 5.520MHz £950 ROHDE & SCFWARZ PUC Instrument computer £850 TF2908 blanking & sync mixer £250 RACAL 9083 2 -Tone signal generator £250 ROHDE & SCHWARZ SKTU noise generator £250 6460 6420 power meter/microwave head £495 RACAL 9084 synthesized signal generator to 104MHz £750 ROHDE 8 SCHNARZ SMS 1GHz signal generator £2000 TF893A audio power meter 1mW-10W fsd £75 RACAL 9300 RMS voltmeter -80db to 50 £195 SHIBASOKU 915D/2 PAL colour video noise meter £650 2092C noise receiver. many filters available £500 SOUND TECHNOLOGY 17006 distortion system £850 WANTED 2091 2092A noise gen/receiver 8 filters £750 Top quality high -end test equipment for stock or SOUND TECHNOLOGY 1000A FM stereo sig gen Band II £500 66008 6646 sweeper 8.12 4GHz £750 will sell on commission Please call, post of Fax lot. any TAKEOA RIKEftI TR9305 audio spectrum analyser FFT 0.0025Hz- 2018 synthesized signal generator 80kHz-520MHz £2.250 quantity Signal generaors. spectrum analysers etc urgently 100kHz. GPIB =ion £3950 required for wading customers. 60566 signal source 2-4GHZ £850 TAKEDA RIKE 4 TR4110/4113AL RF spectrum analyser 10kHz- TF2011 FM signal generator 130-180MHz £195 1 7GHz £2950 TF2012 FM signal generator 400.520MHz £195 ALL OUR EOUIPMENT IS SOLD IN EXCELLENT, FULLY TEKTRONIX 703/7B53A/7A26 100MHz storage scope £1250 TEKTRONIX 35MHz portable scope £600 2438 1 3033, 520MHz universal counter -timer £500 FUNCTIONAL CONDITIOiI AND GUARANTEED FOR 90 DAYS. 35 (Sony/Tek) TEKTRONIX 575 transistor curve tracer £2950 TF2303 modulation meter £325 MAIL AND EXFORT ENQUIRIES WELCOMED. 'LEASE ORDERS TEKTRONIX 5:3502 oscillator, DC508 1GHz counter. DM502 2019 synthesized signal generator 0.08.1040MHz £2.500 TELEPHONE FOR CARRIAGE OUOTE. ALL INSTRUMENTS ARE TF2700 RCL component bridge £250 DMM, SC504 & MHz ó scope, Idled in TM505 main frame f 1500 AVAILABLE EX-STOCK AS AT COPY DATE. GOOD QUALITY TEST NICS milli -volt TF2163S UHF attenuator 0-142db £325 TIME ELECTRC 404S source £100 EQUIPMENT ALWAYS WANTED FOR STOCK. PRICES DUOTED Isd TF2370 spectrum analyser 110MHz £3.500 TOA PM -30R R' VOLT -METER 1/BMV-10V £250 ARE SUBJECT TO ADDITI )NAL VAT. WILTRON 6100 sweep generator 4-18 5GHz £3500
II CIRCLE NO. 132 ON REPLY CARD
April 1990 ELECTRONICS WORLD+ WIRELESS WORLD 289 Instrument Control Solutions For k/. Your Computer
k
w National Instruments, the IEEE -488 leader, has the widest selection of hardware interfaces and software technologies.
NAT ONAL The Software is the Instrument NSTRUMENTS
National Instruments UK Corporation, 21 Kingfisher Court, Hambridge Road, Newbury, Berks RG14 5St Telephone: 0635 523545 Fax: 0635 523154. CIRCIFNO. 1330NREP!VC420 I1 UPDATE Continued from page 278 It should be mentioned that the remove the hidden files and directories Utah program could not be run on machines set up by the installation routine. born Dr Joseph Lewis without a hard disk and its first Removal of these installation files was Popp, 39, a medical computer operation was to print out an invoice a relatively simple process for specialist working in AIS for payment (for the software lease) to knowledgeable individuals with the research, is currently under be made to a PO Box in Panama. A requisite software utilities. arrest in the US following choice of leasing terms was provided However, it was felt that non- information provided by the at a cost of either US$189 or US$378. technical users would be at risk unless UK police. Within a matter of hours, many a special clean-up program was freely users had discovered that the available. Such a program was written, installation routine necessary to run tested and distributed free of charge associated with the INSTALL program the AIDS program had created a and worldwide on various computer had been encrypted to prevent such series of hidden files and directories networks by lunchtime on Wednesday visual inspection. on their hard disks. These were 13 December. The solving of this encryption undoubtedly the "program The next priority was to identify the algorithm became of paramount mechanisms" referred to in the encryption algorithms used during the importance. It was eventually broken documentation. disk "locking up" process so that a early on the morning of Nonday 18 At this stage no harm had come to program could he produced which December. other data and programs already on reversed the effects of this and was The urgency has now receded, but the hard disk. One of the computer able to recover the use of the disk on a there is no doubt that mane users will magazines, who had sold a copy of its machine where the program had have been worried by this episode. mailing list in good faith, began to 'triggered-. Many will re-examine their receive calls from subscribers about After further testing of the original departmental security arrangements. the disk. It immediately started an program, a decryption program was The lessons to be learned are still investigation into the source and eventually written which completely the olio ones - make regular backups operation of the disk and its contents. reversed the encryption and restored of valuable data and view unsolicited Within hours, it was found that the machine to its state before the software with suspicion. installation of the AIDS program put AIDS program was installed. As One large company who received users' machines at risk by operating a before. this program was immediately several of these disks has a system particularly vicious form of software made freely available on a worldwide whereby all in -coming computer protection. This "protection" allowed basis so that anyone who had a software is checked and verified the machine to be switched on a machine where this had triggered before being allowed into the specific number of times (usually 90) could recover its use with the company. before an encryption scheme was minimum disruption. One or two individuals and invoked which altered information on This second program incorporated companies with commercial interests the disk in such a way that the the functions of the first and was in marketing anti -virus software went machine's hard disk (drive C:) was capable of recognising what state the way over the top in promoting locked up and could not be used. machine was in and then taking rumours of viruses and other dire Once locked in this way. the appropriate action. effects of this package. These rumour machine would only respond to Meanwhile, genuine researchers mongers succeeded once again in commands by displaying a warning were finding that disassembly was muddying the water for the genuine that "The lease for a key software hampered by a feature within the researchers. package has expired". It went on to INSTALL program. Probably the most positive result of insist that users should pay the leasing One of the characteristics of the the whole incident was the way in fee for the AIDS software to receive a high level language used which the computer magazines renewal disk to regain the use of their (QuickBASIC 3.0) is that all the reacted. Unconditional support was machine. printed output of a program is usually immeciately offered to the original The investigation into the actual visible within the program file. This magazine regardless of professional software was immediately intensified printed output is often an excellent rivalry. The speed with which the in an attempt to discover how deeply guide to just what the program clean-up programs and information into the operating system this functions may be. Such output was reports were circulated worldwide "protection" scheme was penetrating. certainly visible within the AIDS must surely qualify for an entry in the The programs had been written in a program itself, but the output Guinness Book of Records as the high-level language which meant that fastest and most widespread the files were quite large (172K and publication of any piece of computer 146K respectively) and, although this software. did increase the amount of work Within 24 hours of receipt of the involved in disassembling them. it software, the original clean-up actually simplified the task of program had been written, tested, identifying particular areas where packaged and made available to users malignant code might be found. globally. Preliminary investigations indicated Jim Bates that the program did nothing more than has already been described. First reported in the February issue of Arrangements were made to produce our sister publication, Practical a clean-up program which would Computing.
ELECTRONICS WORLD+ WIRELESS WORLD April 1990 291 SILICON SPEECH His master's voice
We've been around a couple of million years. Computers are still pretty stupid in evolutionary terms. The prospect of holding an interesting conversation with your tumble dryer remains a nightmare but, as a pilot of a military aircraft, you can tell your war-horse to kill. By Rob Causey
hen a drunk staggers believe its importance in speech recog- up to you in the street ``` nition try playing Chinese Whispers. and says "Yavapricer- A typical human vocabulary will con- cuppateeguv?", how ` sist of about five thousand words, some he ' of which are certain to arrive merged do you know what _ co wants? I low many times have you stood `~am together. Called -articulation or con- ''- on a railway station listening to an catenation. this is what the drunk does announcement when a train pulls in half when he asks for the price of a cup of way through and drowns it out? Do you tea. really know what the accountant means Storing a full set of five thousand when he says "The payment to dividend word combinations on a computer differential has migrated over the fiscal would he prohibitive in every sense. In period from the projection in such a way practice it is easier to tell the human as to minimize the return"? which words the processor will under- If you think that you've got problems. stand and restrict the machine's how can you expect a computer to vocabulary. understand what you're saying. We all As a processing problem. speech merge our words together. The shapes recognition is complicated enough. But of our mouths vary, producing a dispar- for a machine to hold a conversation. ate range of sounds. We use different everything thus far must be dealt with in words to mean the same thing and the real time. Users will also expect the same words to mean different things. computer to realise when it has misun- For a computer to hold a conversa- derstood and issue the digital equivalent tion, it has not only to solve these prob- mouth will determine the pitch and dis- of "Pardon me". lems but be able to take sentences in tribution of energy across the range of It also needs to be aware of the speech context. We know what we expect frequencies of the words. The same per- context. "Watch that tree' could be a people to say in certain circumstances. son will also talk at a different pitch life-saver to a driver in peril or an invita- having been listening to speech for depending on stress and emotion level. tion to a very boring afternoon's years. The most intelligent of systems The duration of the sound patterns viewing. will never have the chance to build up varies from person to person. An If the context is limited the user does the same experience of speech as its English gent's speech will he "clipped". not necessarily have to utter a complete users. a Texan will "drawl-. Although the phrase to make the computer under- Programmers develop recognition English language is richer for the vari- stand. Not everyone who needs to talk systems using rules of speech which we ety, it prevents the machine using tech- to a system wants to start a long never think about as we speak. Through niques which assume that phonemes are conversation. all the variations. accents and tones, the same length for everyone. On its way to the computer. the there are only forty distinct sounds. Listening called phonemes. w hich form the basis speech will be contaminated by noise. algorithm of words in the English language. Pick- Given the substantial differences Noise can mostly he dealt with through ing out these phonemes and deciding between individuals. the system has to pre-processing and microphone tech- what they mean is the essence of speech try to decide how much energy at a par- nology before the speech analysis recognition. ticular frequency is speech and how begins. The system then passes these The computer's problems have multi- much is noise without information. This signals through digital filters to split the plied even before the words have left problem will he familiar to engineers speech up into short bursts called tokens the speaker's mouth. The shape of the working with digital signals; if you don't or packages.
292 ELECTRONICS WORLD + WIRELESS WORLD April 1990 SILICON SPEECH
The tokens are compared to a set of el - rules representing the behaviour of ideal speech. When the tokens corres- pond to conditions in part of the rule set, or algorithm. the computer knows that it has identified a phoneme. Com- paring a string of phonemes to word patterns produces sense from the spo- ken statement. Different makes use different algorithms. One of the most common. the Hidden Markov Modelling (H M M). involves comparison of energy in a par- ticular token to a series of models. typi- ,nnnunnn cally five. When the token matches one model. the machine tries to pass it to others in the line. The order of success- ful transactions between models identi- Self-training for the deal: recognition equipment provides a visual indication of fies the speech element to the computer. speech patterns. The picture shows the IB.L1 Speech t iewer system in action. Another common algorithm is spec- tral peak picking (SPP). This represents the package as two values correspond- an IBM PC when the inspection is com- features generated during training. The ing to the highest peaks in a particular plete. The unit has a vocabulary of system runs on an IBM PC with add -in frequency range. The system passes the about 25(1 words. Although it can store hoards filled with custom chips. discerned string of peaks through a filter models from more than one user, Talk - Away from the factory floor. Mar- bank and makes a note of which ones man needs its operators to place every coni's Macrospeak can transfer data at get through. A probability function word in store before use. rates up to 125kbit/s between the host then decides what the speech means. Logos. designed for similar environ- computer and the system. This should Having identified the spoken words, ments, also requires training by each allow the equipment to be used in hank the system must then decide the mean- new user. Various configurations. with dealing rooms where the pace of work ing and what. it anything, it ought to do different levels of complexity, provide cannot wait for the computer to catch about it. between 20 and 24(1 active words from a up. It car, also be used for industrial Applications for speech recognition total vocabulary of up to 1000. The inspection if necessary. lowest cost version performs its fall into two broad groups: systems process- Macrospeak has a vocabulary of 640 which prompt. listen and log and those ing on an Intel 80286 -based board. hav- words and can store up to 205 seconds of which prompt, listen and act. ing first passed the speech through a recorded speech. Dual RS232C ports Various circuit with a tricks are available to the sys- filter TMS3202(1 at its connected the system to a host com- tem designer which reduce the complex- heart. Logos includes a speech buffer puter. Up to 800 macros, commands set allowing between five ity of speech recognition equipment. A and 20 seconds of in action by a single word, with 8(100 common device is to train the system to message to be stored before processing. characters can he stored. hear a particular voice. The operator IBM has produced a voice typewriter. speaks a number of predefined words Tangora, which can recognise up to into the microphone to allow the com- 20000 words although the user has to The front line puter to build up a model of the opera- pause between each one. Again, it Most applications for prompt, listen and tor speech patterns. The computer then requires training to recognise individual act systems have been in military equip- adapts its voice models to match the voice patterns. II3M's equipment pro- ment. For instance. Marconi is develop- user's. This greatly increases the duces a set of spectral patterns every ing a system intended for the European chances of correctly identifying a word 10ms which are compared to 20 spectral Fighter Aircraft (EFA). The company without producing a corresponding increase in the cost of the equipment. Its drawbacks are obvious. Esprit's speech understanding and dialogue (SUNDIAL) programme is Dialogue designed to progress the state-of-the-art Alanagemenl A primitive world across the field of recognition. Signal Equipment based on the prompt, listen processing is based on transputer array and log principle has found use in indus- passing data for decoding with hidden \lessage Language trial inspection and data logging. Log- Markov modelling. Language processing Generation Processing ica's Logos and the Marconi Talkman includes a vocabulary of 10000 words are designed to free the user's hands with decisions taking the context into Acoustic during a Q&A session. Both require accout. A series of frames control Phonetic user training. dialogue management, identifying Decoding Talkman, shown in the photograph. relevant information for comparison is a pelt -worn portable data collection with data stored in the computer. The terminal. A headset carries the micro- result should he a system which can phone. Data is passed from the terminal interrogate its users to speed up over an optical communications link to telephone enquiry processing.
April 1990 ELECTRONICS WORLD + WIRELESS WORLD 293 SILICON SPEECH
IS-CANCELLED IS CANCELLED 4.15 4.30 4.45 IS CANCELLED THANK YOU FOR FAULTY DUE'TOSNOKTAGEOFSTAFF! - ROLLINGSTOCK! LEAVES ON THE LINE! 'RAVELLING B.R. !I tl
BR.
has already produced a speech -based has developed an adaptor card for its PC ment should be able to pick out relevant control system for aircraft which has range to help speech therapists and information which arrives as the answer been tested at the Royal Aircraft Estab- teachers dealing with deaf people. to a different question. So if it asks the lishment and by the US Navy. Speech Viewer converts elements of user for the final destination and the Marconi's Airborne Speech Recog- speech acoustics into graphics displays. caller says "I need to arrive no later than niser ARSI000 provides 1000 word which can he synchronized with audio 9.30", VODIS will store the destination vocabularies for two users. The device playback. The system has been time and come back to the station's has to be trained to recognise its opera- designed to motivate patients. It also name later. This should avoid the need tors but contains other features such as analyses elements of speech without to listen to long lists of trains currently automatic gain control. This copes with relying on language context. The soft- given out from telephone services. the tendency of people to speak louder ware takes up the full dos 6-10K1-yte of which will increase the number of when background noise level increases. memory. callers who can use the system in a given ARSI000 enables the user to interact A talking timetable for public inter- day. verbally with the head up display, rogation has been developed by a group Based on its VODIS work, Logica reducing the number of hand controls comprising Logica. British Telecom and was asked to take part in an Esprit pro- operated by the pilot. Cambridge University. The group set ject on speech recognition. The speech Armada is another project for EFA: a itself the task of producing a telephone understanding and dialogue (SUN- system developed at the Royal Signals railway timetable which asks the user DIAL) programme involves partners in and Radar Establishment. Running on about the train they require. It has a France. Germany and Italy as well as an array of six transputers. Armada uses series of frames to fill before coming up the UK and will run for live years. It is I IN M and advanced statistical tech- with the final answer, but these may he intended to extend the scope of projects niques to develop context -sensitive filled in any order. It doesn't matter such as VODIS into telephone banking models of the pilot's speech. It is still in whether the caller gives the departure and hotel and travel booking. The dia- the development stages. but early tests time, destination or stops first. as long gram shows the project's base architec- showed an 82% success rate using a 500 as all the information is provided at ture. word vocabulary without grammar some point. The answer is probably Sundials processing will he based on rules. Recognition was 99% successful "cancelled" in any case. II HM methods, eventually using when rules of grammar were used. Called voice -operated database - vocabularies of up to 10000 words. Away from the military field. IBM inquiry system (VODIS). the equip - Obviously the system cannot be trained for a particular voice, which further Personal stocktaking: this belt worn data logger from Marconi provides both prompt complicates the analysis. The final aim questions the spoken answer. and analysis of is to demonstrate equipment speaking .7 in all four languages. Other work in the field includes the , examination of better methods of deal- ra7. : ing with the results of algorithm ai= processing. Papers from Southampton i i University have suggested advantages i in using a number of different matching i models. If each analyses different i characteristics of the speech and the i c results can be combined, there is a ,r greater chance of correctly identifying ;, the word. ' 4' ° i i mt ..._. .. Although the current generation of --1."-- L500 i . :. systems cannot hold conversations with c-3 t5b0' i so. ' _,:011: their users, it seems likely that machines Li00'_" 1 i f,' 1 , will he soon talking freely. Beyond that, --- io.. ono ' '-nm , ,om lí `i personality prototypes are the last ob- 5j::%..-_-__11.500";:r.,_ cz:eIJ( stacles to Sci-Fi speaking computers. I! C`fi , Rob Causey is a journalist with ;; Electronics Weekly.
, ; 1._E,'>.! 10 TMS 3477 speech development boards to ,be won COMPETITION ti
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"WIN A TMS 3477 SPEECH DEVELOPMENT SYSTEM"
Using no more than 50 words simply Entries will) be judged t representatives describe -wo ap3lications for silicon from Electron es World and Texas speech synthesis. One should involve Instruments. The competition is open to mass market, nigh volume usage; the everyone except employees of these other-should indicate a specialised, low organisa_ions. Closing date for the
volume aoolication. . competition is Monday April 30 1990.
The mass market, high volume Entries, whicl- must include your name,- - application ms: take system cost into address, company and job tile should account. Tne specialised app ication be addressec to: should-démorstrate the usefi.lress of Lindsey Gardner, Speech speech synthes s; system cost s a Competition, Electronics World, secondary factor. Room L301, Quadrant House, The One appl caticn must involve the TMS Quadrant, Sutton, Surrey SM2 SAS. 3477. The other may be implemented in Entries may also be faxed to us on any Texas Instruments digital speech 01-661 8939. No correspercence or technology. Entries will be judged on communkaticn can be entered into originality takinc into account technical concerning the competition. Winners will and commercial viability. be notified in writing. continued over pace >>>>
April 1990 _ELECTRONICS WOItLD+\1IKELESS WO It - 29; SPEECH COMPETITION: ABOUT THE TMS 3477._ Recording methods based on In playback, the encoded bit short recorded message and a miniature tape recorders are stream from the d -ram bank feeds longer recording of incoming calls. being supplanted by all electronic the 10 -bit D -to -A converter, the A cyclical recording mode can systems where the speech is output of which is delivered to the be set to make sure that latest converted to digital signals, stored SPKR pin on the TMS 3477. speech data is recordedin in solid-state memory, and There are some useful external d -ram. There is also a replayed using a D -to -A variations on this basic operating speech quality monitoring facility converter. procedure. First it is possible to which plays back the encoded All the main functions of a store two different recordings -in data in real time while recording. digital recording system have external, memory with fixed or been incorporated on a single - variable lengths to allow, for A full description of the TMS 3477 chip, the TMS.3477. Any sound or example, for an answering appeared in Electronics World, voice can be recorded = there is machine to be provided with a November 1989. no need for advanced speech synthesis algorithms. This enables rapid system - development with the minimum of - loudspeaker resources. Although the TMS 3477 has full microprocessor compatibility, it can provide a simple recording system with just a couple of 1 Mbit d -rams: an on -board refresh takes counter TMS3 477 care of d -ram housekeeping. Two megabits of ram provides up to - DRAMS DRAMS 30s of recording at the highest sampling rate. The device uses a continuously variable slope delta modulation NP NP eg eg (CVSD) codec with a choice of i Serial 70082 70082 sampling rate between 16kHz and TM S3477 link 64kHz. In the record mode, analogue signals are fed into the chip via the MIC pin. At each - sampling period, the input is compared with the output from a + 10 -bit D -to -A working on data Microphone Loudspeaker from the previous sample. System System Difference data is then sent to external d -rams.
100n Analogue signals for filtering á100n etc Vdd2 Mic. MIC Programming switches Spkr TMS 3477 Processor via hardwiring SPKR 47k or NP i/o -- S1
Vss 2 I AN 18-27 AP9
1 APO All 10k RST I APO OSCIN
OSCOUT
REC/CPO
/C Pi RESET PAUSE PAUSE _L STOP 17 0--- STOP/BUSY RAS CASI DATA 13 CASO Vss1 WE 100 141 _- 100n 100n 2 2 16 10-15 161 3 1O-15 9 9' VTR/EN CS AO -9 RPS A0-9
PH2 TMS4C 1024 e-W5 TMS4C1024 I Drams J1 18 18 PH1 0 Q D a °Phrnse select 4 4 17j 1 t 17
April 19901 GI.C(-I'lü)NI('S WOItI.I)+ WIIZI?LI Sti 1' Olt l.l) SILICON SPEECH
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Technology isn't a problem. Semiconductor companies have long since mastered the art of giving voice to silicon chips. Consumer resistance to talking appliances may be harder to deal with. By Steve Rogerson.
peech synthesis has come a long way since 1978 when the Speak 'ti' Spell toys were launched. Rut the general pub- SILICON lic still perceives it as little more than a gimmick. partly because of an unjustified perception of the poor quality. and secondly because of inap- CONVERSATION propriate applications, such as the Maestro talking car. In fairness, the Maestro was a mar- this direction, more of which later. The keting mistake rather than a technologi- second is to find applications which cal one. The public's attitude had been PIECE offer real benefits. The bottom line is whetted by the popular TV series that most drivers setting off for work in Knight Rider where a garrulous car the morning would prefer a red light on was a positive oracle of useful informa- after it has had one. The latter hap- the dashboard to warn them of prob- tion and had regular intelligent conver- pened because many of the garages that lems than a nagging voice, however sations with its driver. The serviced the car did not know how to good the quality. With the exception of advertisements for the Leyland Lemon reset the computer. toys, the same principle can he applied played on this. Products such as talking coffee to every speech synthesis application so It should therefore have been of little machines did little to improve the per- far de%eloped. Even with telephone surprise that the owners of talking ception. The Hitchhiker's Guide to the operators there is a preference for a Maestros quickly turned off the voice Ga/axv with its futuristic image of talk- warm human voice telling you the box, only to initiate it when they wanted ing machines with in-built, inflexible phone number rather than a to show how had it was to their friends. personalities didn't help. Speech syn- dehumanised, synthesised alternative. There is a big difference between thesis has a lot of ground to make up. Sadly, if a recent brochure from spoken intelligence and a car that tells Two tasks had to be tackled to do this. Toshiba is anything to go by. the appli- you to fasten your seat belt or warns you The first was to improve the quality: cation problem has not really been tack- that the car is ready' for a service the day leaps and bounds have been made in led. Its list of possible uses for speech
April 199(1 ELECTRONICS WORLD + WIRELESS WORLD 297 SILICON SPEECH
synthesis include mostly home and busi- without mixed excitation because its use is so ness machines for which led readouts Nasal cavity small." and red warning lights are adequate and In the synthesis model, voiced sounds arguably better. can he produced with a periodic wave- In fairness, it is unquestionably useful Oral cavity Tongue form generator and unvoiced sounds for the handicapped. either as a reading Lips with a random signal generator. These machine for people with poor or no Vocal cords are connected by a switch which is con- sight, or as a voice box for those with trolled by the pitch. When the pitch is speech problems. The Toshiba Lungs zero it switches to the random genera- brochure does not mention this at all tor; when it is greater than zero. to the and a similar brochure from NEC lists it periodic generator. The vocal tract is as the last of seven applications. modelled with a digital filter. Meanwhile, as mentioned, the prob- The procedure call he reversed - real lems of quality seem all but solved. Human speech organs inversed synthesis - to analyse Modeling speech for silicon encoding. This pro- duces the raw data to drive the speech Sound source Vocal tract characteristics larynx synthesiser. Silicon Acoustic tubes of The filtering stage (mouth) is model- The routes to speech synthesis can be differing cross sectional areas led by low and high-pass filters to define grouped into three types - synthesis by Vocal cords the formants. For five formants. ten fil- vibration rules, synthesis by analysis. and wave- ters are needed. In practice. though, the by rules gives form synthesis. Synthesis i41)1 fifth formant is rarely present so, in real- the poorest quality for the highest cost Turbulence Refletion generated ity, only eight filters are needed. How- and is basically the technique used in the K1 Kz ever, another two filters are needed for Speak 'n' Spell toys. Reflection coefficients the macro of the whole 20ms period. In generate an This procedure can a real system five band-pass filters are unlimited number of spoken words and Modelling the speech tract. needed rather than five low and five a small strings of words using relatively high pass filters. basic memory. The technique stores When the vocal cords are made to The predictive part of LPC is a such as phonemes. phonetic elements vibrate, the vocal tract acts as a more method where you predict the number and diphones. Intonation, allophones complex filter to produce voiced sounds of samples of a waveform based on a can also be added. stress and rhythm such as 't". Amplitude peaks are also weighted linear combination of past pho- Phonetic synthesisers add bits of produced called formants, of which samples. In creating this vocal tract nemes together. It makes for poor there can be five or six in any 20ms model you need to be more accurate at sounds robotic. Speak 'n' quality and period. One fiftieth of a second is the lower frequencies than at high ones. In Spell used three chips to achieve this: fastest step change in spectral frequency other words less bits are needed to the TMS 1000 for control: the TMS5I(X) content which the mouth can produce. describe the higher frequencies. the rom. for synthesis: and TMS6100 for It is also possible to speak without The ten filters mentioned earlier are TI quickly moved on to synthesis by using the vocal cords at all, as happens given K numbers. K I , K2 and so on. For analysis: linear predictive coding or when you whisper. the lower frequencies K1 and K2. six LPC. The NTT and Toshiba partial cor- Raj Gunawardana, European speech bits are needed to control the centre relation or Parcor method. though boss at TI in Bedford, explained: "A frequency of each. K3 and K4 require uses the same developed separately, good percentage of speech is voiced. five bits each, K5 and K6 take four hits basic principle. Your vocal cords are in play most of the and K6 to K10, three bits. This totals 42 These methods use the way people time, but it does depend on the lan- hits for the filter section. The pitch uses voice is speak as a model. The gener- guage. There are some sounds that are a between five and seven hits, though at being forced out of the lungs ated by air combination of voiced and unvoiced five hits the sound is a little robotic. The and past the vocal cords. This produces called mixed excitation. But in model- gain stage uses four hits. This gives a a base hand frequency spectrum ranging ling the human voice you can get away total of slightly more than 50 bits. As from 70 to 150Hz for men and roughly this is based on a 20ms period, this data double for women. The frequency is Functional block diagram of ADPCM is applied at 50 times a second, giving a altered by a cartilage which flexes and decoder with first order predictor. data rate of 2.5khit/s. untlexes the vocal cords. This frequency spectrum is further modified by harmonic excitation ADPCM Dequantizer PCM through variable filter characteristics in Dn L nXA the vocal tract such as the tongue. lips and nasal cavity. Complex sounds are made by changing the characteristics of these filters from one split second to the next. The lungs expelling air can generate Z-1 two basic types of sound. One is a Predictor weighted white noise (or pink noise) An -1 J spectrum generated when the vocal Quantization step adoption Z-1 Delay cords are relaxed. These are the so- called unvoiced sounds such as " sh".
298 ELECTRONICS WORLD+ WIRELESS WORLD April 1990 SILICON SPEECH
This rate can be reduced because Method Examples Bit rate Ease of data compilation Quality some sounds are held than for longer Synthesis by rules 20 to 300bit/s Extremely difficult Poor 20ms. By assigning a single bit to indi- Synthesis by analysis LPC, Parcor 0.5 to 8kbit/s Difficult Good cate whether a filter is to be repeated or Waveform synthesis ADM, ADPCM 8 to 32kbit/s Easy (real time Very good not the data rate can be brought down to processing possible) 800 bit/s. Comparison of different speech synthesis methods. Ironically, the bandwidth of com- munications from the ear to the brain is restricted. There is also some pre- and adaptive delta modulation (ADM) only one frame is stored plus a repeat processing that happens in the ear's favoured by Toshiba. factor. cochlea. The ear acts as a spectrum ana- With ADPCM. a PCM recording is The repeat function can also be used lyser and the rate of information that is made of the waveform. This is a step to produce tones and melodies by stor- passed to the brain is believed to be only digitization describing the waveform of ing musical content with count functions about 70 hit/s. a sound. The software predicts what the for the number of repeats. There are two commonly used meth- next step will he in a sequence of sam- Because ADPCM can work in real ods of generating the basehand wave- ples, the hardware reading in the real time, it finds applications outside the form which models the function of the value and storing the difference normal speech synthesis field. For vocal cords. One is to play the wave- between the real and predicted value. example the CT2 cordless telephone form out at a variable rate depending on The difference value is further weighted system (Telepoint) uses ADPCM the pitch. This is called pitch excited to make the predicted wave more accur- 32kB/s code. TI and NEC will supply LPC and depersonalizes the voice ate. ADM works similarly but without this market. Toshiba is using the ADM somewhat. The preferred method is the extra weighting. system for record and playback use such code excited LPC where a number of Repeated phoneme provides an as in telephone answering machines. different waveforms are stored on rom. enhancement of the process. This is There is no need for tape with such a which acts as a look -up code hook. This similar to the repeat function in LPC system. produces much more natural speech. and can be used to reduce the bit rate. The disadvantage with waveform syn- The individual frames or phonemes of thesis is that it is memory intensive. The the coded waveform are compared with amount of memory needed to store the each other. and against a programmable waveform is so high that the practical Silicon recording similarity threshold. If several con- duration is limited to about 16s. NEC's The third method of producing speech secutive frames fall below this threshold Stuart said: "You use more memory but uses waveform synthesis. The two main memory techniques have improved. types are adaptive differential pulse And as most applications are for a lim- code modulation (ADPCM) used by Block diagram of CT -2 handset showing ited vocabulary, you don't therefore NEC. and by TI for some applications. the role of ADPCM. need lots of memory."
Transmit Transmit Transmit W 64 KB/S serial Keyboard, ADPCM Industry standard ADPCM display, voice 1 Analog standard PCM coder/decoder 4 -bit modulator, codec system macro samples 13 -bit samples demodulator and RF section w Receive Receive Receive
TXMUTE S C PCMIN Y 0 Dec omponder S D 8 Bit A -law 13.Bit 4 -Bit ADPCMOUT ADP2M T samples to samples E samF le AUDIOM linear E C CODEC ADPCM macro Custom ALAW LINB M shift inter- coder/decoder register face SIDE TONE N FSX Compander T 8 -Bit linear 13 Bit /4 -Bit ADPCMIN N samples to samples ADPCM T E PCMOUT A -law \samples R E F R F A FSX/SYNC A C C E E RXMUTE
April 1990 ELECTRONICS WORLD + WIRELESS WORLD 299 SILICON SPEECH
Voiced Pitch /code (periodic (ROM) waveform generator)
Switch controlled Digital D to A Amp 1.11 Output by pitch filter converter
Unvoiced (random signal generator)
As LPC methods have a lower hit LPC method speech synthesiser inferior sound quality implies use of an rate, 80(1 hit/s compared with 8kbit/s schematic. LPC or Parcor type system. Both are and above for ADPCM. the amount of miles better than Speak 'n' Spell. memory needed is smaller. ADPCM, human voice. although TI has managed Scientists have found ways to create though, produces a more natural sound to produce the sound of a harking dog. high -quality talking machines. All they and as said can be used in real time. The ADPCM is unlimited in the range of have to do now is convince people that clarity of LPC is good but the sound is sounds and tones it can produce. they want them. still slightly synthetic. An applications It comes down to a matter of horses engineer at Toshiba said: "It depends for courses. Short duration and high on who the initial speaker is. Some quality lends itself to waveform syn- speakers come out better than others." thesis. Real time has to he waveform Standard LPC is restricted to the synthesis. Longer duration with slightly
HITACHI "Cornpact" series laboratory oscilloscopes This best-selling Hitachi lab. 'scope is exceptionally compact _ áo- " and lightweight but is packed with features: 1' l 32 or 48 channels Multi -level triggering 100MHz asynch. capture Non-volatile data storage 5ns glitch capture Disassemblers for popular µPs as The new LAs incorporatea vast array of features standard ' Id Id U Id u u LI u e and options are available to connect to a very wide range of 1.001C worm ,.u.. IffiA. target systems. Contact us now for full technical details: arukT-(4 Thurlby Thurlby-Thandar Ltd., Glebe Road, Huntingdon, Cambs. Tel: (0480) 412451 CIRCLE NO. 105 ON REPLY CARD 300 ELECTRONICS WORLD + WIRELESS WORLD April 1990 I The most powerful microprocessor in the world using concurrent processing. The system is supplied with everything you need including: Interface card - takes o 'short slot' in the PC and provides link in/out and control lines. Cable - links the interface cord to the Transputer Module. 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Introduction to OCCAM -o complete self -teach course in In short, the Transputer Training System gives you OCCAM. a unique low-cost method of obtaining practical OCCAM Programming Manual - the definitive guide to experience - fast! OCCAM. T414 Engineering Data - full specifications for the Transputer. Saves your time Unpack, plug in and start learning. Everything you C012 Engineering Data - full specifications for the Link need including self teach manuals in one package. Adapter. The Transputer Module houses a 15 MHz 1414 with 256K Saves your money 1 RAM and is external to the PC, so that the hardware is fully accessable. The module includes a wealth of test points, 14 The costs complete system just £995.00 status LEDs, 16 I/O lines, EVENT input, independant + VAT and uses any IBM Compatible PC with power supply, prototyping area and four 15 way D 640K RAM and hard disk as the host connectors, which allow access to the 10 M bits/sec computer. links and control signals. Full hardware and software support is provided for multi-transputer applications. Simply plug Now with 1/2 price course option additional Transputer Modules into the spare link Attend our special 3 day course for just £200 connectors using the cables supplied. In this way networks extra if order with the system. Normal price of course of any configuration using any number of transputers may is £400. be realised! Each module con run one or more concurrent processes and has access to its own local 1/4 Mb RAM and The unique Transputer Training System has been I/O system. designed specifically for education and is therefore ideal The I/O connector links directly to our Applications Board, for use in colleges and universities. The excellent self -teach which enables the Transputer tc control DC motor speed, manuals, included with the package, mean that it can also temperature, analog input/output, and much more! be used by engineers to rapidly evaluate the transputer and its power in real time applications. CIRCLE NO. 106 ON REPLY' CARD *0 utilise amazing Y. LTD. Call 0703 227721 today FLIGHT ELECTRONICS for a free full colour Flight House, Ascupart St, Southampton, SO1 1 LU. catalogue. Telex: 477389 FLIGHT G Fax: 0703 330039 April 1990 ELECTRONICS WORLD+WIRELESS WORLD 3111 CIRCUIT IDEAS oscillator will only he high for this 100s Accurate programmable one shot and it is from the reset that the circuit Two Nor gates configured as an RS tlip- With all programming pins taken output is taken. flop and a programmable crystal oscilla- high, the frequency will he 0.005Hz and tor comprise a programmable flip -clop after 100s the output will go high, reset- T. G. Barnett which gives TTL-compatible pulses of ting the flip-flop and taking the output Whitechapel up to 100s period. Its accuracy could not of Nor gate I low. The reset of the London be achieved with a monostahle multi - vibrator and it is simpler than other tim- Set ing circuits. SL L Output On receiving a trigger pulse at the set input of Nor gate 2, the output of Nor Set I Nor 2 in gate I will go high and the oscillator will he turned on. The output of the oscilla- Nor1 out tor immediately after the reset goes high is low for half the period of oscillation. This frequency is set by the program- Nor2 out ming pins PI to P6 which can be driven from a TTL signal or hard wired using a o IPXO out mechanical switch. Frequency multiplier The circuit shown gives an output fre- Each output from this counter gener- 4µs x 414= 1664µs. the period of quency 600 times the input frequency ates one frequency output pulse, which 600Hz. for low -frequency inputs, the factor feeds back to reset the 4029s for a count- The input frequency can be multi- being set by three divide -by -n counters. down of the next period. plied by any available integer from 8 to A free -running oscillator lC,c feeds For example, at an input frequency of 100(1, the division factor between A and this counter chain with a signal of about I I Iz, the 4018s divide 250k1 Iz by 600 to B. Connections to each 4018 can be 250k z. Meanwhile, the 4(140 binary produce 416.667Hz. and the 4040 altered to give a division between 2 and counter is reset once per cycle of the counts to 416 before it resets. IC,A and 10. Odd integers need an extra inverter input frequency. measuring input IC1B each generate a positive pulse for and Nand gate. period in terms of output counts from B. each cycle of the input frequency to The input frequency cannot be below The input period. a l2hit binary word, is strobe the 40174 storage registers and about 0.06Hz for multiplication by 1(100 latched by two 40174 buffers and fed to then reset the 4040 counter. The 4029s because of the 4(140's capacity of 4096. the three 4029s, which constitute a syn- countdown with a modulus of 416, Frantisek Michele chronous modulo -n down -counter. clocked at 250k z. giving Czechoslovakia B 11 1 4040 00 C2 1n 15 14 12 13 4 2 3 5 6 7 9 47k 4018 IC1B 15 +Vcid 4093 C1 14 fin 14 13 11 6 4 3 13 11 6 4 3 13n 1nIC1A R.47k 10 9 40174 40174 15 4018 15 12 10 7 5 2 151 12 10 7 5 2 14 13, 10 3 13 12 4 3 13 121 41 3 13 12 4 40 15 8 402 402 9 4029 14 15 10 9 15 1 101 9 15 IC1C -9- R4 15k C4 R3 tout 47k p 1220p C1d 302 ELECTRONICS WORLD+ WIRELESS WORLD April 1990 CIRCUIT IDEAS .5V Four -state 50k 50k logic tester LM324 \M Using a single IC, the circuit shown can 560 indicate four logic states. When the Input 25k input is at high impedance or open - --1/V circuit, the led will emit a yellow flicker- 10k ing light. When the input voltage is 25k high, the led will produce a red light and 560 when low, the led will be green. An Red Green voltage 25k alternating applied to the input will produce a yellow light and, if the vV\ frequency of the voltage is lowered, the 50k led will switch red and green 25k alternately. The thresholds can be set for various logic types by adjusting the 1N4148 potentiometers. 150k 20k '50k 109 Hong Yu Qing TongLing China Pseudo -random bit - sequence generator _ The standard way to produce a pseudo- random bit sequence is to use a shift register with feedback. By suitable Nand gates 7400 gates 7486 choice of the feedback function, maxi- Exclusive or Quartz crystals HC6U mum sequence and hence cc lengths ran- fundamental mode 2 to 12MHz domness can he obtained. But the All resistors 1k11 output spectrum of such a circuit com- prises a fundamental component at the sequence period and its harmonics. r A better way is to make a circuit com- prising a number of quartz crystal D- oscillators whose outputs are mixed together using exclusive -Or gates to produce the pseudo -random output. The larger the number of oscillators. the whiter the resulting output spectrum; even a four -stage circuit will produce a spectrum surprisingly rich in inter - modulation products. The crystals should he chosen so that their frequencies are unrelated. It is not recommended that LC oscillators be used, because they may phase lock due to stray coupling. Repeat circuit for as many stages as required Terry W. Spencer T -L output Shank lin Isle of Wight Pseudo random sequence April 1990 ELECTRONICS WORLD + WIRELESS WORLD 303 CIRCUIT IDEAS Oscillator for m2 f =53428"/oHz .----f driving motors R R 3 ik R This circuit is an oscillator that can be «- used for driving two-phase synchronous 32k4 LM324 32k4 motors; frequency can be varied over a R-P fairly wide range with a single 'vV\, potentiometer. 27k4 The 4)1 and 4)1 outputs are 180° out of LM324 phase and the 4)2 output lags the 01 output by 90°. This means it can be used in two ways. 100n R In some applications, one winding is connected from 4)2 to ground and the 32k4 other from ground to either 4)1 or 4)1 to fm;n=1/(2nRC) and the maximum Because of the availability of small reverse. It is also possible to connect fm,x=fm;nR/(R-P). Adjust the capacitor angle motors, this fact can sometimes be one winding from 4)1 to 02 and the other connected by a dotted line for reason- used to avoid a gear train in high -tor- from 4)1 to 412. This allows operation ably fast starting without excessive clip- que, low -speed applications. from a single supply voltage if the non - ping; it is typically about 0.2C. inverting amplifier terminals are con- Stepper motors can be used with two- McKenny W. Egerton Jnr nected to E/2. phase sine -wave drive and run almost as Owings Mills The minimum frequency is given by smoothly as synchronous motors. Maryland, USA Keyboard tester output and the strobe are passed switch would be open and the data This circuit allows the output of an through exclusive-Or gates, configured switch closed. Therefore, the exclu- ASCII -encoded keyboard to he as conditional inverters. With the sive -Or gates with the switches allow decoded into a hexadecimal representa- switches open, the input is inverted and any normal combination of latch and tion of the key that has been pressed. with the switches closed it passes data logic levels to he accommodated. For example, pressing "a" would pro- unchanged. John D. Ritchie duce 61 on the display. The latch input is active low and, for a Doncaster Data hits 0 to 6 of the keyboard's positive -logic keyboard. the latch South Yorkshire 10 Erb FN0500 FND500 Eth c dp I 5 6 + r 0 a 9368 9368 I pB 1/pC LE RBO RBI A Eth 1 e 1k 7486 11 BS 86 84 7 ' 91 92 B3 So 1 51k x8 I St obe 2 nput 1 1 í 304 ELECTRONICS WORLD +WIRELESS WORLD April 1990 CIRCUIT IDEAS PPL lock indicator Locked Unlocked fin 1 fin 1 be CO input) 0 A D -type flip-flop and an op-amp can CD input) o .1- used to detect the lock condition of a PLL, such as the XR-215 shown in the tout 1 tout 1 Clock) 0 diagram. This PLL consists of a bal- I Clock) anced phase comparator, a highly stable VCO and a high-speed op -amp. It can n n o -- o operate with supplies from 5 to 26V and PLL locks at P1L unlocks at rising edge frequencies from 0.5Hz to 35MHz. 1 rising edge Phase lock range Analogue signals can be accommodated from 3000/ to 3V and it can interface with DTL, ECL and TTL circuits. in 5V I is Tracking range adjustable from ±1 to 10on ±50% and the SNR is 65dB. 1 Consider quadrature detection. In óó this condition, lock can be obtained within 900 phase difference between the y 4 k7 4 I input and output. A D -type flip-flop acts 14 16 Vtt Comp Comp the 2 5 as a phase comparator by clocking O Q 5 ins 7474 state of the input frequency at the rising K XR-215 CP edge of the output waveform. Comp i/p A steady state of 1 at the flip-flop 20K Set indicates a lock condition, which will 1 Comp i/p C and R,) to 100n cause the integrator (R, R 9 rise towards r-15 VCO o/pSwee Vee make the op -amp output .----- 2 ICapr h Capr. pp Gain 5V supply voltage, illuminating the led. 6k8 14 13 12 tt If there is more than a quadrature phase difference between the input and F- h/VV Co Ro output frequencies, the output of the flip-flop will be a train of pulses of dif- fernt widths, indicating out -of -lock con- 3 dition. Here, the output of the op -amp 150 LM 324 switches low and the led is off. 2 y.k3 D 41Lock Iindicator V. Lakshminarayanan 7K Bangalore India Analogue switch needs no supply 5V An analogue switch IC, such as 4016 or Input s:gnal(bipolar) 4066, can draw its power requirements from the signal applied at its input with- loading the source of out significantly +5 V Don't waste ideas 1 14 the input signal. The diagram shows the In Vdd We prefer circuit ideas contributions scheme deriving +5V for Vpp and 13 Control - for Out C with neat drawings and widely -5V for Vss supplies needed for the signal spaced typescripts but we would analogue switch to handle bipolar input 4016/4066 rather have scribbles on the back of signals without signal clipping. an envelope than let good ideas be 7 These quad packages of analogue Vss wasted. switches need only 1.50 under condi- We pay for all published circuit tions of V1. = Vss or Vpp. The scheme 5v ideas. You can expect a minimum of works well for switching frequencies £15, increasing to £40 for the best down to 100Hz. Since the on resistance 01 ones. of the switch is typically 200Q, loading 1`J914 22k of the source does not occur. .470n rit 5V V. Lakshminarayanan and V. Gopalakrishnan, 02 Bangalore 15914 22k 470n , 5V T April 1990 ELECTRONICS WORLD + WIRELESS WORLD 305 / FREE POCKET CIRCUIT TESTER WITH EVERY ORDER :. _Test for AC line, On : continuity and special IAA n polarity in a single instrument - offer: A - DM 6133 . Hz, qA A nY 1) µF and °C 9'."1".'Csvn 3'/2 digit display Go;dMIcsr ow.efs 0.3% accuracy £46 All digital multimeters offer V, A and Q. Instruments from ELECTRONICS WORLD+WIRELESS WORLD can also give you Hz, )iF and °C on Goldst . f. selected models with up to 41/2 digits of precision. At prices you wouldn't believe. r an . Our special reader offer, negotiated with South /u A Korea's technology driver, GoldStar, brings you a 4; choice of four top quality multimeters. Each digital DM 7333 instrument has specific facilities to match your capacitance to 20µF needs. Simply choose the model which suits you »., frequency to 200kHz and fill in the coupon below. Alternatively, use your m7.T., . (10Hz resolution) credit card to order the model of your choice by _ ca f t transistor hFE test `" rU O extra large 3'/2 digit phone. . COY , nag display £67.87 The GoldStar DMMs are handheld, battery powered precision instruments with large, clear liquid -crystal displays. All measure DC voltage to 1000V, AC voltage to 750V, AC and DC current to 10A and resistance to 20MQ. Instruments are supplied ready for use with battery, test leads and, where applicable, calibrated thermocouple probes. GoldStar multimeters carry a one year guarantee. DM 8433 Please note that quoted prices are fully inclusive of VAT, temperature postage and packing. measurement -20 to +150°C capacitance to 20µF ril transistor hFE test MA . .7 W. vO extra large 31/2 digit GOLDSTAR MULTIMETER ORDER FORM s . display Please send me model number .... Price £ ... . £72.45 I enclose a cheque/PO to the value of £ made payable to Reed Business Publishing Ltd O Please debit my credit card Expiry date Access O BarclaycardNisa O American Express O Diners Club Name. Mr, Mrs, Miss (Initials must be supplied) Address DM 8243 41/2 digit display 0.05% accuracy Phone number Signature m capacitance to 20µF Please return to Electronics World+Wireless World, Room L301, Reed Business (0.1pF resolution) Publishing Group, Quadrant House, The Quadrant, Sutton, Surrey SM2 SAS. Phone frequency to 200kHz orders to Lindsey Gardner on 01.661 3614 (mornings only) 'r. . yr ooY w np (1 Hz resolution) Otter applies to UK only. transistor hFE test £88.55 Road', rii IIEflRY'5 Edgwán;W2re Londo: Those lr eers _Id 45th ANNIVERSARY Electronic CAD, METEX'AND TEST LAB INSTRUMENTS control systems circuit YOU.PAY TRADE PRICES simulation software .rr Product Functionality Mrc O,S Recommendation Price I. '7(90 ECA-2 Analogue circuit simulator. Allows pC DOs Believed to be the £675 (special . NEW VERSION effects of different components to XT AT 20 most powerful PC- terms for MULTIPLE be investigated -rnrreeffectrvely 386 or based analogue simu- education - ask SCREEN than by bench testng Very hgh 256k later lator available. Reg forECA.2S) PLOTS specification prop am includes RAM ularly upgraded. Ile f-t'Ó Monte Carlo & Worst Case foier- Mac grates fully with VUT L.1.1 ancing Fourier analysis of tram RAx for schematic en- sients. Nonlinear Components try of circuito. characterised by breakpoints or 31/2 AND 41/2 DIGIT Dmms polynomial functions ALL MODELS WITH CONTINUITY TEST )* With Capacitance + Hie test 0 with 200KHZ Frequency counter) METEX PROFESSIONAL` LCA-1 Logic Circuit Analyser, a new sis- As As This digital program £450 (special 3;q and 4¡7 digit Dmm 5 with hard carry case ter program to ECA-2 Produces ECA ECA simulates minmax terms for edu- Large LCO Displays with leads battery and instructions 204 AC OC logic analyser -style output tines propagation delay and cation) BARGRAPH SERIES. M4600 30 Range 4 ?Digit 0 05 with (up to 68 signal traces) and in integrates fully with Data Hold ii £52.13 corporates delay and nestuble VUTRAX schematic M36109 3 Digit 30 Range 03 i I £46.04 M436030Rangr47 Digit 005' with macros entry. M365003', Digit 30 Range 03 r. 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TEST INSTRUMENTS FOURIER form covenng 388 or Module 1 £70 NAMING 1 -Frequency response 512k later Additional modules £70 31700 LCR AC Bridge £103.20 TE220 1 MHZ Audio Generator £81.75 RAM program M3002A AC Millivolt Meter'1MHZ £85.80 3300 Autorange Digital Cap Meter £64.00 WINDOW 2- DC quiescent analysis Full £245 mouse Multi user pro version Rease ask us 2020 500 KHZ Function Generator £96.50 6100 Signal Tracerrin)ector £52.30 3-Transientanaysrs des'ble 4162AD 150 MHZ Fr Gen Plus 6 Digit 5250 150 MHZ 7 Digit Frequency 4- Fourierarlalysis a remarkable program Counter £172.86 Counter £64.50 260380 1 MHZ At Gen plus 6 Digit OST5M 5 MHZ Bench Scope £168.00 PCS Process control simulator for 3 -nn AS AS Digitising cursor, on- Counter £166.16 243 0 24V 0'3A Variable PSU £56.00 £100 control Quantization effects ant CODAS CODAS line help, noise (special terms) TE200 150 MHZ RI Gen 2450 24V 0/5A Variable PSU £69.55 plant saturation modelled (450 MHZ Harmonic) £80.00 154 4 /15V Or4A Variable PSU £40.00 all available. for education) I I CODAS II Single -input control system simu- BBC DFS Ideal for control en- £475 (special "POCKET" TEST -INSTRUMENTS lator represents non-hnearties Arch, emul gineers, 4 domains, terms for edu- and transport delays Transient re- PC DOS time. frequency. root cation) TF20 Dual Scale Sound Level Meter 3900TO (CD Dmm With Dwell And sponse, root locus, Nvguist. 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ELECTRONICS LIMITED , . . .-T. \_:.. Protel Autotrax is a precision tool that improves productivity for ;L] . occassional and expert : ... user alike. It streamlines many of the repetitive PCB layout processes while providing --J powerful interactive design automation. - -. --r With a comprehensive library of Through hole and Surface Mount Devices the designer - --; - has the option of modifying stock components or creating new using the programs standard : drawing tools. New .___. components can he saved to user libraries or merged into the main r,-=_ library. : _ ------.--- J,7. Working from a netlist Autotrax automatically places components and routes tracks in . conformance with user definable design rules. Board lay out can also be manually edited. . Blocks of components can be defined then moved rotated flipped or copied while connectivity is maintained. Tracks rubberband on the screen in real time. Interactive routing allows §1k. the designer to manually route critical tracks before autorouting. ,.._....; _.: Placements .!,., of text strings components pads and tracks are duplicated by a repeat function. RF designers can define a partial ground plane or area fill around tracks, pads and SEE US AT THE components. Prices are from £299.00 to £999.00 plus VAT. 27.29 MARCH 1990 - NEC BIRMfNGHAM sER:,L BI.UD CLOCK J.A.V. Electronics Limited, Unit 12a Heaton Street, Denton, Manchester, M1134 3 R Tel: 061 320 7210 Fax 061 335 0119 Also Available in the Protel Range: Schematic, Easytrax, Traxstar, Traxview. CIRCLE NO. 109 ON REPLY CARD IN VIEW OF THE EXTREMELY RAPID CHANGE PC " rli TAKING PLACE CARDS itl IN THE PC cards can be the solution. ELECTRONICS Whatever your application - IEEE or analogue INDUSTRY, LARGE QUANTITIES interface, industrial control, data acquisition or digital I/O Flight has a product from the leading }f OF COMPONENTS BECOME edge of technology. REDUNDANT. WE ARE CASH Flight Electronics' extensive PC card range provides across the board expansion. PURCHASERS OF SUCH Low cost 8 to 16 bit data acquisition MATERIALS AND WOULD 1 to 12 channels APPRECIATE A TELEPHONE Immediate delivery from stock Many cards designed and CALL OR A LIST IF AVAILABLE. manufactured by Flight WE PAY TOP PRICES AND Interested? Telephone Flight's sales office COLLECT. for friendly, qualified advice. 4/ R. Henson Ltd. 1. 21 Lodge Lane, N. Finchley, t= ='Ili London, N12 8JG. I- Flight Electronics Limited, Flight House, Ascupart Street, 5 mins. from Tally Ho Corner Southampton SO1 1LU. Telephone: (0703) 227721 Telex: 477389 FLIGHT G Telephone: Fax: (0703) 330039 01-445 2713/0749 CIRCLE NO. 110 ON REPLY CARD CIRCLE NO. 111 ON REPLY CARD 308 April 1990 ELECTRONICS WORLD + WIRELESS WORLD IEEE 488 An idea developed back in 1965 is starting to bring the benefits of automatic test L_At systems to small and medium sized companies. The idea was a forerunner of the IEEE488 bus. The catalyst which smashed open the market is the IBM PC and its plethora of clones. Hewlett-Packard initially developed what it called the HP interface bus (HP - INST UMENT 1B) to connect a range of programmable instruments to its computers. Because of what was, at the time, a high data transfer rate (up to I Mbyte/s) the bus gained popularity in other uses such as communication between computers and peripheral control. Such an increase in use led to its adoption as IEEE standard 488 in 1975 and the nickname "general purpose interface bus" (GPIB). There The IEE488 bus crosses every application were some minor differences between It means as much to small IEEE488 and the HP-IB standard boundary. which have now been resolved. companies as large ones and is used by both As the bus gained popularity com- panies such as National Instruments the scientific community and industry. The pioneered its use on other computers. computers makes it National is still the market leader today advent of cheap personal but its position looks far more assailable first choice for small to medium sized data than it did in the early days. One of the first personal computers to be used in acquisition and automatic test systems. this field was the Commodore Pet but it was not until the advent of the IBM PC When used with, say. an IOtech that life started to change. and for a GP488 IEEE board, HTBasic makes number of reasons including cost. ver- the PC closely emulate the HP work- satility, availability and an ever growing station. It operates under DOS and has range of software. nearly all the instructions presently sup- Nick Challacombe. director of ported by HP Basic. Full screen editing Keithley Instruments, highlights the dif- and debugging are included and the edi- ference in cost: "In 1978 computer tor has been enhanced to include find. substitute, move and copy capabilities. based systems used minicomputers GPIB connector showing how each Many existing programs written for HP which left little change from £10000() line is assigned. whatever you did. It was cheaper to hire computers can be executed with more engineers at annual salaries of HTBasic without alteration. £3500 each. A few years later as com- Geoff Dyson. a sales and marketing puter prices fell and salaries rose it manager at Keithley. also noted the reached parity. Today a PC is a fifth the PC's versatility: "The PC has made a cost of an engineer and lets one engin- tremendous difference because of the eer do many different jobs". added software available from word In the early 1980s Hewlett-Packard processing to engineering packages. still controlled the market, but since PCs have become more popular for then, the market has grown and busi- multi -use. You can switch off your test ness has shifted from HP to the PC. HP 0107 DIOS system and start using the PC for word 0102 0106 processing. This has made automation acknowledged this change by bringing D103 DI07 out its own PC look -alike called Vectra. DIC4 D108 accessible to a lot more people and EOI REN test HP computers still control a large chunk DAY GND (TW PAIR W(DAV) reduced the cost of automatic because many NRFD GND (TW PAIR w/NRFD) equipment. These days, in most cases. of the market, mainly NDAC GND (TW PAIR WMOAC) engineers grew up using the HP user- IFC GND (TW PAIR MFG) manufacturers of test equipment incor- PAIR WISR)) SRO GND (TW as standard". friendly software and want to remain ATN GND (TW PAIR W/ATN) porate IEEE488 with it. In response to this there are SHIELD SIGNAL GFOUNO Farnell Instruments, though, only software products available such as offers the bus as an option on its AP and HTBasic which effectively converts an MP series power supplies, but it is IBM PC/AT/386 into an HP9000 available as standard on some of its series 200/300 workstation look -alike. other products. 309 April 1990 ELECTRONICS WORLD + WIRELa S WORLD IEEE 488 Standardization command structure. 488.2, is already could be tied to a single IEEE488 The link between IEEE488 and the PC available on some instruments. The address under computer control. is important because more people are industry hopes that the new language Siemens, too. has a range of instru- looking for an automated rather than will standardize functions from manu- ments that can be operated from a PC manual solution to their problems. facturer to manufacturer. across the bus. These include multime- Before the advent of the IEEE488 bus One of the disadvantages of the bus is ters, scanners, counters, function and 1 pulse the answer was a binary coded decimal its speed. At just over Mbyte/s it generators, digital 1/O, transient system. This led to a rat's nest of wires. sounds fast but the system involves a lot recorders and voltage and current The 1EEE488 bus allows the use of of handshaking which slows it down. calibrators. equipment from any vendor with a There are two developments which aim reasonable chance that the system will to overcome this. work. The instruments simply plug in The first is a new bus system called the back of a PC and communicate with VXI which many predict will eventually More complexity each other. Challacombe added a note replace IEEE488. It is very strong in the Typical of the more complex instru- of warning: "But there is a but: and that military ami aerospace sectors and Nick ments now emerging is the Clarke -Hess but is not the protocol, which is care- Challacombe described it as "the bus 6000 digital phase meter available from fully controlled, but the command lan- structure of the future". Lyons Instruments. This unit has an guage which is not." Even so IEEE488 will be around for a optically isolated IEEE488 interface Ile pointed out that the "F" character long time. VXI is more expensive and it and can he used for the precise measure- is used to change the functions on will he at least five years before its price ment of phase angle at frequencies from Keithley instruments (Fl. F2 and so becomes competitive. In the meantime 511z to 500kliz. It costs around £3000. on), but the IEEE standard does not the second solution of making the Keithley's latest, the source measure- specify F. So if you have a Keithley instruments more intelligent will prob- ment unit (SN U). will simultaneously ably have DMM and replace it with an I IP DMM overcome the speed source current and voltage and measure you may have to rewrite some of the problems. current and voltage. So, for example. software. Software cost is such that For example, two -channel DM NI can you can source a voltage to a device people occasionally buy old instruments make one million readings a second on under test and measure the current. It is rather than update the software for use each channel. Theoretically. at this effectively four instruments in one - with new ones. speed. it could not he used on the bus. current source, voltage source, current Keithley has tried to overcome this But the instrument has a micro- meter and voltage meter. Three or four problem by a firmware routine built into processor and a chunk of memory in SMUs may be stacked together for mul- its instruments called Translate. With which the data can be dumped until tiple source and measurement. This is Translate you can emulate an old instru- there is free time on the computer. particularly applicable to the semicon- ment on the PC. For example. one can Coombs said: "VXI attempts to ductor industry. quickly change the function key from an resolve the paradox about fast new com- Keithley has also started to make a F to an A or vice versa, although this puter systems and an old 8 -bit bus. Why switching matrix which can program 576 may soon he irrelevant. can't we take the computer architecture individual relays in a full cross -point In the various IEEE488 committees and use it in instruments. What the VXI matrix. There are up to six cards in the there is a move for a compatible com- consortium did was develop an architec- mainframe, each card possessing 8 by 12 mand structure which, on the face of it. ture that takes the VME bus and adds to cross -points. This gives 8 by 72 ways on will make emulations redundant. A new it. We are developing a card that plugs the cross point. Combining these with into a VXI chassis and lets a GP113 the SMUs creates a test system which Asystant-GPIB software to let a PC instrument run an VXI". can do very complex tasks. This is about control instruments on the He said that VXI is growing faster as much as anybody will want to do on IEEE488 bus than any other bus ever did and believes the bus. that in ten years time it will have over- Most of Keithley's instruments can be taken the IEEE488 bus. connected together and built up to an The first programmable DMMs advanced test system. Its most recent appeared about ten years ago. Current. success is an automated Hall profiling voltage and switching equipment fol- system which allows the carrier concen- lowed. This was a major step because it tration and mobility profiles of semicon- a moved the bus into test systems. ductor layers to he obtained at room - Under control from the IEEE bus and liquid -nitrogen temperatures. Once ,``1:mmum¡¿M! m; voltage and current could he sourced to set up. the g,,"- - programming for a full series - -- ,. 5,--- the device under test. switched of cycles is as easy as using a ~, j around modern \------the s f Z:12 device and results sent to the mea- washing machine. The cursor moving surement unit. The bus had become the across the screen pointing to the oper- HIV l' VI' base of a simple instrument -based ATE ation in progress hears a resemblance to / system run from PC. the 11' ., a cheap wash, dry. spin routines at the laun- ttt , A recurring problem of the early derette. The gurgling and burbling of equipment was that it came either big the chemicals completes the illusion. 0-111q1 and expensive or cheap and simple. To change a PC into an IEEE488 `. Philips challenged this with the system instrument controller, an interface card J+' 2/ which comprised 15 stackable. intel- has to he plugged into the PC. There are 7(, ligent modules that let the user start a la ge number of cards available from small and build up as needs dictated. All many manufacturers. 310 ELECTRONICS WORLD +WIRELESS WORLD April 1990 IEEE 488 Keithley's Stephen Blight inspects the automated Hall profiling system. lOtech has a range of products that relate to the IEEE bus. National Instru- ments is the market leader, however. National created the market and every- body else has followed with compati- bles. National, for example, has the AT-GPIB for the PC and AT and the MC-GPIB for the PS/2. Both will run under OS/2. The AT-GPIB works with computers equipped with 16 -bit plug-in slots. It is a direct memory access (DMA) interface which can control IEEE488-compatible instruments via the PC or AT. An NEC microprocessor provides the basic talker, listener and controller functions. The MC-GPIB is for PS/2s equipped with Micro Channel plug-in slots. It uses the same NEC processor. Nearly all IEEE488 hoards for the PC use either this NEC µPD7210 chip or the alternative Texas Instruments TMS9914A. Newer designs often use the NEC unit because it can detect the receipt of a specific character auto- matically. This allows the system to set up a high-speed DMA transfer and get on with other tasks until it detects the terminating character. It will then inter - rupt to indicate the transfer's comple- Listening, talking or just sitting tion. To do this with the TI chip needs extra circuitry which is not always The IEEE488 bus is the most widely used lines. The data lines carry data and com- available. messages and use the 7 -bit ASCII method of connecting a number of instru- mand lOtech by comparison offers the Per- to the I/O port of a computer. Abil- or ISO code set. The eighth bit can be ments sonal 488 series with versions for the ity to make use of the bus is a built-in used for parity. feature on many instruments. Handshake lines asynchronously con- PC, AT. 286, 386, MC -PS/2 and com- Communication between devices on trol the transfer of message bytes patibles. These again use the NEC chip. the bus is done by passing one of two between devices. The three lines are While Philips recognises the need to types of message through the system. NRFD (not ready for data), NDAC (not be in the market with its PM2202, valid). Device -dependent messages have infor- data accepted), and DAV (data identical to National's MC-GPIB, it mation such as programming instruc- NDAC shows when a device has or has also produces a card that will turn its tions, measurement results, machine not accepted a message. an 1EEE488 status, and data files. Interface messages The five interface management lines Ph13655 logic analyser into are command type messages for, say, manage the flow of information across the development system and instrument addressing and unaddressing devices. interface. They are: ATN (attention) controller. This card fits into one of the Devices on the bus can be listeners, issued by the controller to differentiate a PC -compatible expansion slots of the address and talkers and/or controllers. A DMM for byte between command, analyser's built-in IBM-compatible example is a talker but it can also be a data; IFC (interface clear) issued by the A talker basically sends mes- controller to initialise instruments to their computer. listener. inter- sages to one or more listeners with the known state; REN (remote enable) issued ICS Electronics also makes two controller managing the flow of informa- by the controller when it wants remote face cards which are available from tion by sending commands to all the control over all the instruments on the Amplicon Liveline and again use the devices. It is possible to have a talk -only bus; SRO (service request) issued by any NEC chip. These are for the PC, XT. device needing service from the control- device connected to a listen -only device. AT and PS/2 model 30. a controller. ler; and EOI (end or identify) sent by the Such a system does not need An interesting variation found in Using a plug-in interface card and asso- talker with the last byte of a data stream to is Mostek ciated software, an IBM PC or compatible show the end of the message or issued by National's AT-GPIB the can be converted to a controller in charge the controller to tell devices to identify Turbo488. This asic c-mos IC increases of a wide range of test equipment. their response in a parallel poll. both the performance of programmed The interface system itself consists of Negative logic is used with standard I/O data transfer software and the data TTL logic levels. When DAV is true'for 16 signal lines and eight ground retum or transfer rates obtainable with the high- it has a TTL low level less than or shield drain lines. The signal lines com- example speed DMA controller on the PC lines, three handshake equal to 0.8V. When DAV is false it is a prise eight data motherboa,d. It works by using fifo lines and five interface management high level of more than 2V. memory to buffer data, allowing instru- April 1990 ELECTRONICS WORLD+ WIRELESS WORLD 311 IEEE 488 "Writing and debugging IEEE488 application programs for GPIB instru- mentation systems has traditionally been a tedious task for the specialist .. . PC -based programming tools have changed all this, and there is now a range of software packages which help the first time and the experienced user alike". Challacombe said it was his intention "to deskill the software side because the industry is full of engineers who are not software engineers. The idea is to make their job easier. There are a lot of pack- t, -.- - ages available that do this". ' 1 1111_II( "You need software that lets you use . y 1 !".. 1--;: - the hardware without being a PhD in \ :1\1-~1, software engineering." % \t 1 1> +..- Ó ; Philips' Test Team and National's LahWindows let application programs he compiled with an off-the -shelf com- piler so the computer does not have to store the complete development pro- gram suite. The PM3635 logic analyser can be used as an -188 IEEE controller by adding an Keithley puts its faith in the Asyst interface card to its internal PC. software package. This is a program- ming language with a long learning uses ments to operate at top speed without a serial communication link to the curve. Asystant-GPIB, a menu -driven having to wait for the PC to handshake distant extender. Since serial communi- interface written in Asyst, gets around every transferred byte. cation is more prone to transmission this; with little programming know- Andrew Penney. an application errors, a 4 -bit cyclical redundancy check ledge, an engineer can perform FFT engineer at National, said: "The Turbo is also included. analysis and various statistical chip lets us run at the full recommended Converters permit non-IEEE488 functions. speed of the bus. It lets us get the most devices to be used on the bus. Products It works in two modes - interactive out of the bus. Computers have 16 and include RS232. RS422. Centronics and and program. In interactive mode, com- 32 -bit buses but the GPIB has an 8 -hit SCSI interfaces. They enable a com- mands can he sent to the instrument and bus. The Turbo lets us take a I6 -bit puter fitted with all IEEE488 port to information received back. In program word off the bus. It can be important control non-GPIB devices or, conver- mode it enables user programmed mac- when moving large amounts of data sely, let GPI B devices he controlled by a ros to reduce the number of key strokes. such as when transferring a waveform." computer with a different port. Shane Naish of Keithley said: "An In theory, there is a number of restric- engineer will easily be able to use it in a tions when using the bus. The distance couple of hours". between any two devices can be no Times of trouble His colleague Stephen Blight added: more than 4m with an average separa- The greater use of the bus has created a "You can create new command words tion of only 2m across the entire bus. need for troubleshooting. In response. to improve user friendliness. This The total cable length cannot exceed Keithley has developed a bus analyser. means you can also easily translate it to 20m. And there is a limit of 15 devices Keithley's Nick Challacombe com- German, for example. Or you can con- that can be connected to the bus. This mented: "Over the years we have come figure the language to match exactly remains theory because there are prod- across all types of problem where the what you are doing". ucts which break these limits. customer says the bus does not work. If Coombs is critical of menu -driven Bus expanders are a typical example. you have a lot of instruments from a lot software, understandably since Lab- These can double the number of instru- of companies and something goes Nindows uses icons: "There are always ments that may be connected to the bus wrong you don't always know who to limitations with a menu -driven program to 28 devices, and double the 20m cable shout at. What the analyser does is to because if it isn't in the menu, then you limit. isolate the faulty bit of kit.' can't do it. LahWindows lets you con- Extenders burst through the 20m Setting up application programs for trol the GPIB instrument, acquire data. limit allowing instrument remote con- the bus call he a tricky task for a soft- format data and then do analysis. It has trol up to 2km away. Smaller units are ware specialist, never mind an engineer. more than 100 analysis routines on the available for 300111 extensions. They But there are a number of PC based library". work by switching the signal from software packages available that make He added: "We want to do for the IEEE488 to RS232 or RS422 and then programming and debugging easier by engineer what spreadsheet programs switching it back at the other end. For providing high-level programming com- dill for the accountant." example. National's GPIBIOOA turns mands. on-line help, instrument and The next step with LahWindows will the 16 IEEE488 signals into 24 parallel function libraries, and powerful editing be to develop software which makes use RS422 signals for transfer over 300m. and debugging facilities. of the higher power available to newer Its larger GPIBIIO for 2km operation Jean-Louis Steevensz of Philips said: machines. 312 ELECTRONICS WORLD+ WIRELESS WORLD April 1990 VAV INTEGRATED MEASUREMENT SYSTEMS COMPLETE RANGE OF PC CARDS & ACC . I ' [ES FOR ENGINEERING & SCIENTIFI .' ' LICATIONS 1-210 Paradise 350 EGA Graphics Card & 1-211 Hitachi Mono/CGA/EGA/VGA Card +I+ DATA ACQUISITION CONTROL 1-213 Paradise Autoswitch 480 1-214 Plus PCL-711 8 Chn 12Bit A/D (25KHz), 1 Chn 12Bit D/A, 16 D/IP, Paradise VGA 16 D/OP, 1 Chn Counter PCL-812 16Chn 12Bit A/D (25KHz), DMA, 2 Chn 12Bit INTERFACE -CARDS D/A, 16 D/IP, 16 D/OP, 1 Chn Counter PCL-718 16 Chn 12Bit A/D (50/100KHz), DMA, 2 Chn 1-102 XT Dual Serial Card 1-103 XT/AT Parallel Card 12Bit D/A, 16 D/IP, 16 D/OP, 1 Chn Counter PCL-720 32 Chn D/IP, 32 Chn D/OP, 3 Chn Counter 1-104 XT/AT 4 Port Serial Card PCL-726 6 Chn 12Bit D/A, 16 D/IP. 16 D/OP 1-201 AT Dual Serial + 1 Parallel PCL-725 8 Chn Relay Actuator, 8 Chn opto -isolated I/P ,, PCL-738 SSteeppeer Motor controller (3 Motors), 8 D/IP, AV WINCHESTER DISK DRIVES PCL-743 Dual port RS422/485 Interface H-001 Seagate ST -225 20Mb 68ms PCL-750 PC Prototype development card H-002 Seagate ST -125 20Mb 40ms PCL-755 4 Slot extension board H-003 Seagate ST -251 40Mb 40ms PCL-760 PC Voice recording/play-back card H-005 Seagate ST -4096 80Mb 28ms XT/AT Drive PCLD-789 16 Chn amplifier & multiplexer board H-l0l Miniscribe 20Mb Card PCL-790 360K RAM/ROM Disk card Wide selection of daughter boards & wiring -- FLOPP.Y, DISK DRIVES boards/accessories F-001 360Kb 5 25" Floppy 947 F-002 1.2Mb 5 25' Floppy APPLICATION SOFTWARE F-003 720Kb 3.5" Floppy F-004 1.44Mb 3.5' Floppy PCLS-700 LabDAS Data Acquisition & control package for PCL cards PCLS-701 Labtech Notebook AV DISK COiN'TROLLERS PCLS-702 Labtech Acquire D-001 XT Hard Disk controller 1.2,3) PCLS-703 Asyst (Modules D-003 XT 360Kb Floppy controller Plus PCLS-704 Asystant D-005 XT 1.2/1.44Mb Floppy controller PCLS-704G Asystant GPIB D-101 AT Hard Disk controller Analysis PCLS-705 Unkelscope Waveform D-103 AT Hard + Floppy controller PCLS-706 Labtech CHROM Plus PCLS-707 Labtech Control CASES &-POWER SUPPLIES PCLS-708 DaDisp Vr C-001 XT Flip top case INDUSTRIAL PC SUBSYSTEMS C-105 Mini AT Flip top case C-108 Mini AT Slim case 19' Industrial PC Chassis IPC-600 Rack mountable P-001 XT 150W Power Supply IPC-6010 PC -BUS Card Cage P-105 Mini AT 200W Power Supply PCA-6121 80286 AT CPU Board for IPC-600 , r. PCA-6130 80386 CPU Board for IPC-600 D ISPLAY MON'I,TORS Fully configured XT/AT/386 Industrial PCs also available - VA, please call. M-001 Samsung 12" Monochrome M-011 Samsung 14' Monochrome IEEE-488 (GPIB) INSTRUMENT CONTROL, M-101 Samsung 14' CGA M-201 Samsung 14' EGA Complete range of National Instruments cards and software. M-202 NM 14" Super EGA PCII PC/XT/AT IEEE -488 Interface M-203 Samsung 14' VGA AT-GPIB High Performance PC AT IEEE -488 Interface M-208 NEC Multisync GPIB-1014 VME Bus IEEE -488 Interface NB-GPIB Apple Mac IEEE -488 Interface VA K EYBOARDS & .MIC,'E LABWINDOWS Applications development environment software package K-084 84 Key Keyboard K-101 101 Key Keyboard #41+ G-001 GM6 Genius Mouse PC :M.,OTHERB,OARDS G-002 GM6+ Genius Mouse B-301 80386 Mboard 20/24MHz -,r> B-302 80386 Baby Mboard 16/24MHz N E T W O IR K _I" N G B-304 80386SX Mboard 16MHz B-214 80286 Baby AT Mboard 12/20MHz Full selection of Ethernet/ARCNet boards, file servers, cabling, B-001 8088 XT Mboard 4.77/10MHz Novell Netware Software, for your complete PC networking needs. VAV VIDEO DISPLAY CARDS VAY B ARCODE iRE-ADERS 1-001 Colour/Mono Graphics + Parallel Card 1-002 Colour Graphics + Parallel Card 8W410 PC Keyboard Emulator Barcode reader 1-003 Mono Graphics + Parallel Card 8W420 RS232/422 Barcode reader 1-005 Super EGA Graphics Card 8W430 Hand held barcode scanner & decoder 1-006 VGA Graphics Card 8W607 PC Barcode printing software INTEGRATED MEASUREMENT SYSTEMS LTD. 306 Solent Business Centre, Millbrook Road West, Southampton, Hampshire SOl OHW TEL: (0703) 771143 FAX: (0703) 704301 CIRCLE NO. 112 ON REPLY CARD 313 April 1990 ELECTRONICS WORLD+ WIRELESS WORLD BUSES Cache memory for faster VMEbus systems ache memory techniques increased. If this high-speed memory are well known in the mini- cache is designed to be loaded continu- computer and mainframe ously as the processor executes pro- worlds. but not yet in the Cache memory can grams. the cache becomes a buffer 32 -bit microcomputer com- be a cost-effective between slower system resources and munity. Yet the system performance of the higher -speed processor. today's bus -based 32 -hit computer alternative to In early systems such PDP-I Is and boards can he improved by applying IBM 360s, speeds were orders of magni- cache memory techniques. originally large blocks of tude slower than present micro- developed for minis and mainframes. high-speed processor -based systems. but the which can increase a microprocessor system problems were similar. For example, unit's working speed and throughput. memory. Frantisek CPU speed and throughput were lim- despite a performance degradation in ited by the need continually to access other system elements. Michele describes slower system elements such as core The microprocessor unit in most sys- memory. The principles that made tems operates at a higher speed than the the use of cache memory techniques attractive to to which it is system elements con- cache with the DEC and IBM can be applied to bus - nected. By closely coupling a small based architectures. While VMEbus- block of high-speed memory to the pro- VMEbus based systems are used as examples in cessor. the memory is accessed without this article. the concepts apply to most delays and system throughput is bus -based designs. VMEbus hosts a diversity of applications, many of which push the bus data bandwidth to the limit. This DSP development system, a PC -AT on u- . a VME card communicating with a Motorola DSP56001 in an adjacent slot, uses a high speed local sub -bus which allows the large quantities of data involved in a typical DSP system to be transferred without congesting the system bus. The sub -bus carries a data burst rate of 18Mblt/s. The addition of a cacheing system to the u main bus may offer considerable advantage with this data -intensive SVSTEM56 type of application. 11 nrnr - PC 31' The board runs a 12MHz 286, v 3n:bh".kk 49'. incorporates 1Mbyte of ram, VGA 1-1,917," graphics and controls both the 31/2in !.. i; ' floppy and a 40Mbyte SCSI hard drive. , The system comes from Data Beta. 7b1.¡; i7."' 7r '.1, -'.,--'' ` '{o_ r ... . .11- - _ ...... . .r _ 1, a s,,: _ (\ __,_.:. r" _ \ Y 1;G`_ .. K \ \ v4\ , ` : 314 ELECTRONICS WORLD + WIRELESS WORLD April 1990 BUSES Principles of cache memory Cache effectiveness is based on the idea of locality of memory, which has three characteristics. First, over short periods storage most accesses Data of time, MPU memory System are made to adjacent small groups of M PU memory VME memory locations (as in program Tag storage I bus loops). Therefore, a cache memory coupled to the MPU storing carefully - Cache memory selected data - will generally have the J data the MPU needs. Second. data stored in the cache and recently used by Fig. I. Tagged information in cache memory is directly associated with information the MPU will probably be re -used in memory and can be accessed at high speed by a microprocessor. quickly. And third, data adjacent to system data that has been recently used by the MPU will probably be used next. In other words, since most of the MPU's accesses to memory are performed sequentially, a well designed cache MPU/Memory bus VME bus master scheme couples the MPU memory closely i interface processor to the data most likely needed. This design allows the pro- VME bus slave VME bus cessor to function at its maximum per- interface formance level (Fig. 1). When the MPU is initialised. it must load program code from system memory - often a combination of dram On -board memory and bulk media. such as floppy or hard disk. As the MPU takes individual blocks of information into its registers from system memory. it also tags the Fig. 2. For additional global system memory, the designer can provide dual-ported information in a unique manner and memory access to boils CPU and VMEbus. MPU memory accesses are made over the deposits it into the cache. Since the VMEbus or a dedicated memory bus (VMX). Cache memory reduces the overhead tagged information in the cache has a for both buses. direct association with information in main memory, the tagged data can be designed cache architecture will have ment in both the speed and density of checked and retrieved from cache at hit rates of 80-95%. d -rams. many VMEhus applications use very high speed. There are many maximizing strat- processors with large blocks of memory Before each fetch from main egies for keeping relevant data in cache resident on the VMEhus processor memory. cache logic checks to deter- memory. When the MPU begins to board. mine whether the specific information execute a new program, the information Because the memory is physically and being requested by the processor probably will not be relevant any longer electrically close to the MPU. no wait- resides in the cache. If so. the MPU can and a series of misses will occur while ing is required to access it. If a second access it quickly. If it is not in the cache, relevant information is retrieved from port_ or an extension of the CPU - an access to main memory is required. main memory. memory bus to the VMEbus. is When the N PU writes information Any method by which new informa- provided, the memory also serves as into memory, it also writes the same tion is deposited into the cache, displac- global system memory. The con- information into cache. As the MPU ing older information, involves several figuration shown in Fig. 2 is desirable executes a block of program code, the trade-offs. For example, various from a performance and cost standpoint cache fills and becomes a window con- algorithms have been developed selec- if the memory on the V,NIEbus pro- taining a mirror image of the same infor- tively to replace the oldest or least -used cessor module is sufficient for the sys- mation contained in main memory for data in the cache as new data is brought tem application. When system this program block. Given the princi- from main memory. applications require large blocks of ples of locality and the looping nature of Each of these algorithms involves a memory - for example. in large many programs. the probability of find- certain level of complexity in its hard- databases and imaging applications - ing information in the cache is very ware implementation. Random there is insufficient hoard space on a high. replacement of old cache data with new VMEhus processor module to keep the When information required by the data is a very effective compromise memory closely coupled to the MPU. MPU is found in cache. the event is between maximized performance and Under these circumstances, MPU called a cache hit, which allows the such hardware complexity. accesses to memory must be made over MPU to run with little or no delay in the VMEhus or over a dedicated executing the program step. If the infor- Cache memory and VMEbus memory bus, such as VMX. Accessing mation is not found in the cache. the One of the most important issues affect- memory over the VMEhus involves bus event is called a miss and the MPU is ing performance is the speed with which overhead delays as well as bus arbitra- forced to wait until the information can the processor can access system tion between other system elements be retrieved from main memory. A well memory. With the dramatic improve- that need to use this common resource. April 1990 ELECTRON ICS WORLD + WIRELESS WORLD 315 BUSES to -physical address translations can be implemented at high speed. In this 16 -bit MPU application, the cache limits the lengthy translation time associated with VLSI Logical address 32 -bit memory management units, while VME bus providing the security and flexibility of interface VME bus the MM unit. Memory Lookaround management cache unit 16 -bit processor unit. Cache memory's effectiveness lies in its ability to provide Physical address 32-bit VMX bus l a mirror image of selected system interface VMX memory that can be accessed by the bus MPU at high speeds. In other words. to Cache ensure system integrity, the system soft- memory ware must always be assured that cache memory data is a copy of the data in system memory. This is not a problem in single -master VMEbus systems, but in The use of the local VMX memory Fig. 3. With 16 -bit microprocessor and systems with multiple masters, such as a bus to couple the MPU and large blocks 32 -bit data transfers, cache memory processor and a disk with independent of system memory, moves the system accommodates long words on a cacl:e DMA capability, there must he a way to architecture a step closer to the ideal of miss. /n addition, a lookaround cache keep track of memory changes not per- having memory physically and implements virtual -to -physical address formed by the MPU. electrically adjacent to the MPU. How- translations and optimizes the use of A memory change can occur, for ever, bus overhead still enters into any VLSI memory -management units. example when a specific program is memory access over the VMX bus. It is loaded via the DMA disk controller. in these bus architectures that cache Ally cache data that references system memory can improve performance. memory locations overwritten by the The cost/speed penalty of the Application DMA device must be purged from the memory devices is an added considera- Cache memory architecture can he cache. This is accomplished by imple- tion - one that becomes increasingly applied in many ways to improve system menting the cache with memory ele- important as the system memory is performance. For example, disk -drive ments like high-speed resettable static expanded. With relatively small blocks controllers and memory hoards have ram. of memory (for example the 512Kbyte been designed with on -hoard cache To help reduce the need to purge that might he found on a VMEbus pro- memories. The operation and the value questionable data. the cache memory cessor). high speed d -ram can be used to of cache memory on these system com- can be closely coupled to the memory provide no -wait -state performance. ponents is similar to designs in which management scheme. This design However, large blocks of very high cache is used to optimize MPU allows for specific addresses of system speed memory become uneconomical throughput. memory to be deemed non-cacheable, as system memory requirements grow. Variations of the cache principle can so that data from these areas must Cache memory becomes an attractive he applied to reduce the translation always he fetched from system memory. buffer between the high-speed MPU overhead of VLSI -based memory -man- Thus; fresh data is always available to and large blocks of slower memory agement units. For example. by provid- the MPU for memory location that may accessed over the VME or VMX buses. ing a look -around cache, virtual - be changed by other system masters. There are other cache options that assist in tuning the system to maximize Ripe for cacheing in the chips? Intelligent 1/O controller from Diamond Point. cache hits. These include operating the Configuration includes a 68K processor and 68880 series floating point unit and cache for instructions only (instead of system controller in a 20 -slot chassis. data) or dividing the cache space to seg- ment data and instruction activity. The cache can be configured to use the 32 -hit VMEhus bandwidth while using 16 -bit processors. Since programs generally access sequential memory locations, if word X is fetched from the system memory on an MPU access. it is highly probable that the sequential word Y will he needed in the next step of the program. System performance can be optimised further by configuring the cache logic to fetch more than one word ,-.4":4?41 of data from memory when a cache miss occurs. This pipelining is referred to as the cache blocking factor. Using a 16 -bit MPU. coupled with the ability of the ELECTRONICS WORLD+ WIRELESS WORLD April 1990 i Y ,p4 I o BUSES 16K ,'64K RAM 80286 16 -bit 64K microprocessor PROM Buffer 8466 128K/512K Short burst VME bus Disk Disk disk data DRAM FIFO gate interface high speed interface drive controller array VME cache memory bus VMEbus to support 32 -hit data trans- Fig. 4. Multiple data paths on this memory pages can be allocated to per- fers, cache memory can be configured to intelligent cacheing disk controller form functions independent of the bal- retrieve a VMEbus long word on a provide the disk interface, system ance of the memory pool. The optimal cache miss (Fig. 3). interface and on -hoard 80286 size of a cache memory depends on sys- microprocessor with access to the high- tem variables, such as operating system Disk -drive controller. An intelligent speed cache memory. application, number of disk drives, and cacheing disk -controller is a device system load. based on a high-performance MPU and A cache size equal to the disk drive's uses a sector buffering technique to allows the controller to perform parallel capacity would result in a cache hit on improve a system's disk I/O perform- cache operations transparent to the sys- every operation. hut the cost and space ance by reducing the access times asso- tem. Unlike traditional controllers. an required for such a cache eliminates this ciated with rotational delays and seeks. intelligent cacheing controller will not as a viable choice. The optimum cache The cache controller is able to reduce terminate a disk read operation as soon size is the point at which additional access times by responding to system as the requested data is on -board. cache yields little gain in hit rate. This data requests directly from its cache Instead. it will transfer the requested value will vary from system to system memory. sectors to the system while disk data is and may range from several dozen The MPU manages the contents of 'read -ahead' into the cache. It is pos- Kbyte to more than 0.5Mbyte. the cache and the physical disk oper- sible that this background cache -fill The intelligent cacheing architecture ations. The cache's random-access operation will continue past the time uses a FIFO device to interface to the capability allows data at various disk when the command complete interrupt system, the main function of which is to locations to he transferred into. out of. was issued for the original request. allow high-speed burst transfers across and retained in the controller under A cache on a disk controller could the system bus. It does not have to act as MPU control without restriction. support write cacheing, another parallel the speed matching device - the cache The sequence of events for the most activity. The controller reads data to be memory performs that function. As a common cache function, a read oper- written on the disk into its cache result, the FIFO only needs to be equal ation, begins when the controller memory, posting completion status to to the largest required data burst. Since receives the read request from the oper- the system before the disk write occurs. this controller is closely tied to the sys- ating system. Instead of immediately Conceptually, write cacheing is just the tem bus, additional functions can be initiating a disk seek, the controller reverse of read cacheing. but has the incorporated into a cacheing control- searches its cache memory for the distinction of having a cache hit rate of ler's FIFO. For example. the short burst desired sector or sectors. If the search nearly 100%, because the disk latency FIFO gate array performs byte and results in a cache hit, the data is trans- time always occurs as a parallel or back- word swapping for compatibility across ferred directly from the cache to system ground activity. MPU types. memory. If the desired sector is not The functionality of a cacheing disk located in the cache, the controller per- controller requires a hardware design The availability of 16- and 20 -MHz forms a normal disk read operation. capable of supporting advanced oper- 32 -bit microprocessors with 4-Gbyte Once the data has been transferred ations such as parallel data transfers. address ranges opens new VMEbus- into the cache memory from the disk, it real-time activity. queue management based system architectures. While there will he transferred to system memory. and data -structure management includ- will continue to be improvements in In either case, when the system has ing searching and sorting. memory density and speeds, along with received the data, the controller will The hardware architecture (Fig. 4) a lower cost bit of stored data. there will issue the command complete interrupt has many significant characteristics. A still he a need to match the high speed to inform the system that the operation primary characteristic is the insertion of processor's capability with slower is complete. the cache memory on the local data bus. memory and subsystem components. Dual -porting of the cache memory The memory is not monolithic - Cache techniques can do the job. April 1990 ELECTRON ICS WORLD + WIRELESS WORLD 317 SPACE provides 20W of RF which, together with a dish gain of 46dBi, results in an El RP of 800kW. Although at first glance this may seem a somewhat exces- HIGH-LEVEL sive power margin, the following factors must be allowed for: service beyond the primary region of the footprint; opera- tion at the hand edge of the trans- ponder: atmospheric attenuation; and, PIRACY not forgetting the host, gain loss result- ing from transponder saturation, together with interfering sideband Piggy -back users threaten the future of noise. Parasitic technology has come a long satellite broadcasting. The underground way since those early days when industry is now well established and it may attempts were made. mainly in the US, to shake it off by the simple expedient of already be too late to eradicate it totally. applying a low -frequency quasi -random frequency modulation to the satellite conversion oscillator. Such vain The recent introduction to tively low field strength compared to the attempts were soon countered by two- Europe of high -power televi- main, or host, signal. way frequency -control systems which sion direct -broadcast satel- The principle of operation is well rendered aloof virtually immune to such lites has resulted in an established. A TV transponder has a measures. Later attempts deliberately alarming increase in a pre- bandwidth in excess of 30MIIz and, to position interfering energy at the viously little-known phenomenon. This below saturation. provides an output hand edges were quickly abandoned is observed as the accumulation of addi- power proportional to the input power because of their adverse effect on pic- tional, or parasitic, energy at the hand received from the ground. A ground ture quality. The odd aloof may go edges of orbital transponders. station commonly radiates an El RP unnoticed by the viewer. but deliberate These Additional Low -output (equivalent isotropic radiated power) of great chunks of energy do not! Obscure Flux, or ALOOF, signals around IOU M W. a combination of some Modern parasitic units are very easily appear on the output of satellite trans- hundreds of watts RF and a very high - installed and require little adjustment ponders as the result of narrow -band gain dish antenna. Sufficient signal is once the dish has been aligned and the uplinks from equipment being supplied received by a viewer's dish to give good operating channels set. A thriving under the counter to businesses and quieting of the FM carrier in a band- underground industry produces and ins- other parties requiring periods of com- width of 26M1 Iz. However, to achieve a tals the devices. and at around £20k municationover long distances who are comparable carrier -to-noise ratio in a sterling for a pair of transceivers. many not willing to run up huge hills on the receiver of 26k I Iz bandwidth, an El RP businesses have seen this as an excellent international telephone networks. of only 100kW would he needed. investment for a link which can be Once established, these links can carry Most parasitic tranceivers use nar- available 2-f hours a day. The dishes are voice. data or fax and usually go com- rowband FM with receiver bandwidths indistinguishable from those already pletely unnoticed because of their rela- of 12k Hz. A typical transmitter familiar on the skyline. Since it is usual for official ground stations to monitor return signals them- selves, a spectrum analyser forming part of their operational armoury, aloof has adopted some low -profiling measures. One thing an engineer expects to observe when examining an FM -TV sig- nal is a reasonably symmetrical display. Aloof therefore places the full -duplex 'go' and 'return' carriers symmetrically about the host with a total separation of about 28 NI I Iz. In order to diffuse these carriers when displayed, aloof gives them their own energy dispersal. similar to that of the host. In the loss 14", event of of _ carrier or modulation of the host. aloof r~ will hop to an adjacent transponder. ...Me. GI making it impossible for parasitic trans- missions to he located in a quiet hand. The TV industry is \ery worried indeed. Such is the unease among Euro- pean satellite operators that interna- tional talks have already been held to ow. discuss means by which this problem of> might be eliminated. `" TIM 68000 16-Bit Microprocessor ....., ", ye. Training System Used with any IBM PC or compatible, the TIM 68000 provides the ideal introduction to 16 -bit microprocessor tl technology. Based on the Motorola 68000 microprocessor the TIM is a microprocessor target board specifically designed for both ; training and development applications - just take a look at the specifications! rz,- . 68000 16 -bit cpu .... .j . kV 68230 Pin provides 2 x 8 bit user UO ports - : , .1IN1 Up to 64K Bytes RAM ?KZ_ ... eee ,; Up to 64K Bytes EPROM Space Dual RS232 Interface TIM 68000 Special Offer. Accepts standard Motorola 'S' record files from hast computer Until May 31st 1990 we are offering the Switched faults TIM 68000+ Cross Assembler/Text Editor Powerful on -board software VAT. IBM PC based cross assembler/text editor For Only £350.00 + Optional applications card Complete with user manual, technical manual, Motorola 68000 programming guide and Li Technical Systems Ltd. comprehensive cross assembler user manual Francis Way, Bowthorpe Industrial Estate, Norwich. NR5 9JA Telephone: (0603) 748001 Fax: (0603) 746340 CIRCLE NO. 113 ON REPLY CARD Electronic Design Software DIAMOND Eb S' t TtlM-t-I..,al fcsb 1peg POINT sPaidde I If you are using PC/AT/XT/PS-2's for Industrial Applications as: FACTORY AUTOMATION DATA ACQUISITION Electronic COMMUNICATION Design and are in need of a Specialist in PC ADD-ONS and Support as well as a Complete Systems Software Capability and the experience to match, then: You need to contact Ian Gardiner immediately on O ,yebi 061 122390 PCB layout 4) ll We have a wide range of Schematic Capture Communication Boards to 131tc!w Digital Simulation support all Serial Protocols DIAI OND POINT and both Analog I/O and INTERNATIONAL Ccm p UterS ` >;t o Analog Simulation (SPICE) Digital I/O Boards. o4tz:` pokr,gMetnyava2d Limited PCB to Gerber Translator For Software and North Point Business Estate, Enterpiise Close, Rochester, Kent ME2 4LY Tel: (0634) 722390 Fax: (0634) 722398 Support contact:- Keith Harris Gerber to PCB Translator on 0202 - 876300 Standard and Custom Libraries CIRCLE NO. 114 ON REPLY CARD CIRCLE NO. 115 ON REPLY CARD April 1990 ELECTRONICS WORLD + WIRELESS WORLD 319 ! Toumazou & Lidgey on Introduction to Analog Désign Franca & O'Leary on 28 March - 4 April 1990 Mixed -Mode System -Level Design 25 - 27 April 1990 Spence & Soin on Tolerance Désign Phillip Allen 9, 10 July 1990 on CMOS Analog Integrated Circuit Design & CAD Techniques Barry Gilbert on 16 - 20 July 1990 Advanced Bipolar Analog Design 24 - 28 September 1990 Courses to satisfy the demand for vital but scarce skills in ANALOG CIRCUIT DESIGN Continuing Education Courses at Imperial College, London, England Further details from: Peter Combey, Continuing Education Centre, Imperial College, London SW7 2AZ, U.K. Call (44)-1-589-5111 Ext 3033/4 or FAX (44)-1-584-7596 SOFTWARE REVIEW prote! Schematic is a 2-D draft- ing package optimized for quick and efficient rendition of electronic circuit diagrams. PROTEL It is written by Protel Tech- nology. a Tasmanian company. WHAT YOU GET The complete product is supplied in one SCHEMATIC IBM -style hook -box and comprises a well produced manual, five floppy disks and the dongle. It is worth saying that. in the business software arena. dongles and other copy protection devices are AND no longer the norm and we are now seeing the copy protection schemes being removed from other schematic - capture products. AUTOTRAX INSTALLATION This I like. Instead of a special executa- ble or hatch file which creates its own directories and fiddles around with the REVIE PC system files (coNFrc.sys and Atrro- ExEc.BAT). Protel provides simple instructions for generating the required Action is initiated through the left code and data directories: all tiles are B. Anderson reviews :nouse button or the return key. and exit then simply copied into the code direc- from action initiated through the right tory. Installing the display and hard - two packages from mouse button or the escape key. copy device is a simple matter of run- Actions are thus effected by pressing ning the hatch file which copies the Protel Technology:: the left mouse button, which pulls down appropriate device driver to the file a circuit -drawing the main menu at the left of the screen, accessed by the program. selecting an item from that menu which The programs. drivers and library aid and a PCB may in turr effect another pull -down take about I.5Mlbyte of hard disk. but menu with further selections. the data files appear to he reasonably 'layout system. Circuit connections using the Schematic compressed, so that your hard disk will package are made using either signal not be overloaded with storage -inten- lines or netlabets. sive bit -image files. Once in the program. there is a set-up facility which allows the user to con- figure for any desired colour scheme. data tile path and other operational ,:. attributes. Jl 49R .. `.'L..J RUNNING THE SOFTWARE The first time I tried to run the software ,`' I got the message "Copy protection 112,41. device not in place which was found to ~1499 .-¡- -.44 O9 be due to a had connection at the i9 - . ,ae.. dongle. When this was screwed home, Pr4.!Y4 the software started without problem. My1+4. As might be expected for a cad pack- age. the whole interface is in a graphics environment and much of the user inter- face is remarkably intuitive. allowing SERIAL I01 one to use the product. in a simplistic way. immediately without reading the manual. I April 199(t ELECTRONICS \WORLD+ WIRELESS WORLD 321 SOFTWARE REVIEW list by type. rather than a parts list. The advantage of this is quick generation of amz_nAlh 1 3 . . .. quantity order lists. BY\. : : ' Dadra' B u D. ta. A'dNqeels' Ed11 A weakness of ha\ ing a separate post f11 IN1inl^oh' .....U3.:...... ® ...... is . . . . processor that, the design rule 'In.; ...... oU1 U1 if _...6261 6261 2764 LW,r report shows that a node remains n> Dl . . O{ Mid unconnected, then the program must be A i lii .. D7OLi ALái óáL' - A . . Od I[ re -run to carry out the changes. It would DG t -_ ._ AA 06 31 06 [= have been helpful if this facility could A7 D7 [. . . a Ji . . . - YZI A9 have been run from within the editing '33 t7 B¡ A environment and. for example. position - +-- AL aLD -o...... S_. the cursor at the offending node. ; r. '¡- '::: VP, A very nice aspect of the report is the Ji[niTEE:J7d;f {41:... - .o..o...... list of which nodes are left unconnected. together with warnings of unconnected TO1C: All to. ith.n i'dúrt inputs. nsdo 11 acfrerd.nco rll0.'Et62i: gel t conelirit' ' A j.}y! . 16K' RAM " 16K' RON SPEED .... . - Panning across the screen is by com- irc.=='1.; :;h,:....:'' .:...... plete re -draw. rather than copy and part -update. This places great emphasis Line -type buses are drawn by attaching the same net name to lines at opposite on the speed of the re -draw algorithms ends of the bus. and makes movement across a complex drawing particularly tedious. I lower er. Most of the options bring about a it is necessary to search through the this aspect of the package is well written mode of operation. An example of this library visually, looking through hun- and even on a PC AT. the re -draw speed is the component placement mode dreds of items to locate the one is reasonably fast. which allows the user to select items required. On the whole, the speed of any oper- from a library and bring them into the A separate library manager may be is loading of schematic. However. once in compo- used to modify the supplied libraries or ation acceptable, although some libraries took a few seconds. nent placement mode. it is not possible indeed build your own. to do anything else but place compo- which can he irritating it you wish nents. IN USE PLOTTING to alternate between component import may he selected from the Plotting of the circuit diagram is and line drawing. A double escape key- Components accomplished with a separate program. mode. library, at which point they appear on stroke returns to menu which allows good control over the final with the vari- the screen highlighted. They may be Once you are familiar output. including rotation and scaling. then instead of the moved around to any point on the ous commands. Although the speed of output was point -and -shoot mouse environment. screen and rotated through multiples of may then rather slow. the quality of the final the rather faster first -letter -select tech- 90 degrees. The component by pressing return. result was excellent. nique is probably better. For example. be placed Line -type bus is available to allow The overall result was tidy and pro- to PLACE A LINE, then type only "PL" diagrams. fessional, though some component sizes and the line placement mode is selected. you to achieve tidy processor as in the diagram shown. The were rather large, which in conjunction The alternative is to pull down the main circuit is to run normal with the rather coarse placement grid menu. use the mouse to select the PLACE technique employed the bus then attach a resulted in poorly packed diagrams. item. press the action button. and from lines into line, and line. the new menu then displayed to select net name to that That particular line can then be picked up at a remote the LINE option. CONCLUSIONS point by placing a line from the bus to a 1 particularly like the library facilities, to it the same new node and attaching which are comprehensive and simple to LIBRARIES net name. COMPONENT use. The intuitive user interface. similar facilities are These are good: they are comprehen- All the usual editing to many business and scientific software available. including block move. copy. sive and well designed, albeit with one packages. is a simple to use. My only as well as an undelete or two quirks. Firstly. a maximum of save and delete, grumbles are the dongle and the rather deleted items. only three libraries can be assigned as facility to reinstate limited zoom range. Although the facili- on line at any given time. Although this ties are very limited compared with did not cause problems in the layout 2D drafting aids, those AUXILIARY FILES standard undertaken. it might be very irritating provided are attuned to the circuit sche- has been drawn and having to ditch and reload libraries. The Once the circuit matic problem and, within that context, the post processor may be second. more annoying. aspect is that saved, provide an excellent solution. The latest invoked. This is an excellent piece of the items in the library are not neces- version (3.3) of this software is now sup- which generates net list, con- sarily arranged in any logical (or alpha- software. plied without the dongle. and within the list, bill materials and a betical order). Hence if you cannot nection of context of the UK market should he the net list appears to remember the exact component nomen- design rule report: considered to be reasonable value for the type format. The clature even if the component you want he of Schema of money at £525. is in the currently accessed library, then bill of materials is a completely resolved 322 ELECTRONICS WORLD- WIRELESS WORLD April 1990 I IMTR SOFTWARE REVIEW 53 84 ERROR c BUSY A271 LADY A2 PCLK 61C HOLDY 023 - CLK HLDA Circuit diagram of a single -board 55 LOCK RUE D 12 66C RESET C 0 DTRTr M/TII computer produced by Protel Schematic. SO SRDYEM 4 SI PEREO 61 SRDY PEACE }-- ARDYEM - 31 ARDY WET COP 52 are options available to generate your CS own library components. or T 47" indeed modify those provided. This is all U9:A achieved within the program by gener- U8 74(88 82288 ating what you wish on the PCB. high- SB M lighting this as a MUTL 2 block and then saving D12- 7/a n /T77 IORC D the to IOUC }IL- block the library. The "compo- 15 C E rlüTÁ -/-1- CECIL 1MTA >13 nent" may then be loaded to the PCB in CnDLY ne OT/Tr 17 the same way as any other. I READY DEN Tó MCE U6 2 CLK ALE 74LS138 S A 1 7 V U9:D B VI PLACEMENT 3 74F88 C V2 12 Y3 Before routeing is carried out. the com- YI E1 VS ponents must be placed -manually, or ®. CI Y6 E3 Y? automatically based on minimizing the rats -nest route lengths. However. this is only a first attempt and the manual sug- gests that you should pre -place as many of the critical components as possible. Further, when components are placed on the basis of the shortest rats -nest length. that does not mean that it will he AUTOTRAX the most efficient once the card is rou- ted. Consequently. it is advisable to Protel Autotrax is the PCB layout com- effected with either the mouse or cursor move components with the rats nest panion to Protel Schematic. It is keys, zoom level being controlled with showing and make a (human) judge- immediately clear that the two come PAGE UP/PAGE DOWN keys. One nice fea- ment on how. in general. the card from the same source. since the user ture is that the software is always look- should be routed. interface of replacable pull -down ing for user input. so if you press PAGE UP menus and action keys is the same for twice. then having accepted the first both. zoom up request (and started the ROUTEING The package supplied is the same as re -draw). Autotrax then spots the next Import of the net list allows display of that for Protel Schematic, with a well zoo UP command. stops the previous the rats nest of connectivity data, a sim- laid out manual, files totalling 12Mb)te re -draw and draws at the next zoom ple point-to-point net. These nets can and another dongle. At one stage. when level. Hence the program is very then be routed either manually or running this software, my machine had responsive and little time is wasted. automatically. three different dongles daisy -chained A facility which provides for a very The automatic router seemed to be very out of the parallel port of my machine. fast operation of common key -stroke comprehensive with strategies based on one for each of the Protel products and a sequences is the key hoard macro. These simple point-to-point. one via L routes. third for another cad package! macros may he nested and are based on two \ is Z and C routes and others. Installation again followed the same the simple one -letter command However, although the package was course with the user in total control of sequences (the first letter of the com- able to accomplish a reasonable job on the name of subdirectory and the copy- mand) which allow keyboard access the demonstration PCB files supplied, ing process itself. Selection of particular through the menus. Macros may he when presented with a simple 80286 screen and output device drivers was recorded to disk and automatically SBC circuit, the routeing was unin- accomplished by running appropriately reloaded each time the software is run. telligent (missing obviously more direct named batch files. e.g. EGA.B\T to install Ground planes are well handled by routes) and generally slow. This prob- an EGA screen. Autotrax. Simply define a polygon on lem was traced to the poor placement of the layer of interest and it is then filled devices, which limited the facility for in intelligently. missing other tracks. routeing. After moving the FACILITIES components vías and pads. to achieve a more logical flow. the auto - The software can he used for PCBs up to When the program is run and the last router completed the job to 87% after 32 by 32in with position resolution of edited PCB is selected then not only is about 49 minutes on an 8M iz PC AT. Imil (0.00Iin). It supports up to six sig- the PCB loaded but so is much of the For those requiring more comprehen- nal lavers with two overlays and two state of the the system at the time the sive autorouteing. there is an add-on resist masks. As evidence of its good editing was last halted. including high- product called Traxstar which provides support for surface -mount devices, it lighted nets and the set-up values. rip up and retry routeing strategies for a also supports two paste masks. The further £850. number of nets per file is limited to 10011 A point to note here is that the system and. although this may seem generous. LIBRARY gave an error when the net was being if you have a 32 by 32in square PCB. you The component -outline library loaded from the schematic capture. and could easily exceed this limit. provides data on pad size and placement the report file generated indicated that Moving around the PCB can be for a wide variety of components. There the 80286 had not been loaded. The April 1990 ELECTRONICS WORLD+ WIRELESS WORLD 323 SOFTWARE REVIEW Operating environment and stroke widths. Since the PCB is System requirements are a PC or PC AT -compatible computer running MS-DOS, viewed from the top with all layers with a hard disk or two floppy disk drives; transparent. the strings placed on the CGA, EGA or VGA graphics or Hercules; a solder side and the lower screen should colour monitor; and a parallel printer port. It appear mirrored; but did not. It is recommended that a Microsoft-compat- requires a separate operation (TEXT ible mouse and a draft printer be used and access is needed to a pen -and -ink plotter, a MovE)) to correctly orientate the solder Gerber -compatible photoplotter and an side strings. Excellon-format NC drill. SURFACE MOUNT the package to get the report, the data Surface mount components (SMD) can contained therein is a mix of the useful be handled perfectly well, even when and the never to be used. The report pin lead devices and SMDs are mixed on lists the wide range of routeing and pol- both sides of the board. All necessary A rat's -nest of unroofed connections, ishing strategies available and the rela- reverses of the SMD pattern are which "rubber -hand" when components tively quick time for each pass. The effected. are moved. really useful data is the list of unrouted connections, which may he used to route the board manually. HARD COPY The smoothing passes were interest- Plot facilities are provided through a ing. offering an opportunity to clean up separate program, Traxplot; this sup- the routeing automatically. Facilities ports a wide range of peripherals. include the diagonal remover, which including popular devices such as Ger- removes short diagonals which the auto - ber photoplot. HPGL. Epson and router has duplicated. the loop Laserjet. remover, the double back remover, the remover and the two -via dual stub FILES remover. AUXILIARY A post processor may be used to gener- I encountered what could potentially from the PCB be a serious problem. in that there ate a bill of materials appeared to be no direct way of high- data. Although reasonably effective, it lighting unrouted nets for manual inter- of course cannot provide the same level vention. This had to be done one by of information as the bill of materials Zoomed display of a PCB on the Auto tediously checking whether they generated from the schematic capture. trax screen one, had already been routed from the report Conversion utilities are provided for file. This called for a chance to test the earlier versions of the software. cause of this was traced to incorrect lead on-line support offered by JAV, which outline nomenclature in the net list. fed turned out to be helpful and well through from the schematic capture THE MANUAL informed. The answer to targeting the library. So beware- the libraries are not The manual is reasonably well produced unrouted nets was simply to command necessarily correct. Note that the soft- and includes tutorial and reference sec- all nets to be high -lighted which, after ware only registered the fact that one tions. although the package is very routeing, highlights only the remaining component had not been loaded, hut straightforward to pick up and use and unrouted nets. did not explain why. This is an indica- the manual is only of importance when tion of a general failing. in that there you get stuck. The information is all were limited messages when things went DESIGN RULE CHECK there, though some items were difficult wrong and no on-line help to supple- After manual routeing, the program to find because of a rather limited index. ment them. will check that the PCB is routed to the To aid manual routeing. particular set of design rules. for example track nets may be high -lighted, making it a spacing and via -to -track clearance. CONCLUSIONS simple matter manually to route each Protel Autotrax is simple to learn and net. use, especially if used with Protel Sche- The results of the routeing are availa- NETCHECKING matic to generate the circuit diagram. ble in two forms: firstly the displayed An option is available to generate a The facilities are there, but some need traces: and secondly a report file. netlist from the PCB. This file can. in to be used with care, particularly auto Although it is annoying to have to leave principle, be checked against the netlist placement and autorouteing. Once the generated from the schematic. The pro- ground rules have been set for these is well, although Supplier gram to do this called facilities, they perform Protel Schematic and Autotrax are "NETCHECK", but no data on its the autorouteing is rather slow. The obtainable from: was available in the manual. program has no on-line help and has JAV Electronics Ltd operation Unit 12A Heaton Street annoying quirks, such as the need to exit Denton to DOS in order to view the routeing Manchester M34 3RG Telephone 061 320 7210 STRINGS report log. Priced at just under £1000, Prices of the packages from JAV are: The program allows the placement of the package is quite good value for Schematic £525+VAT text strings on any layer, the strings market. Autotrax £999+VAT money in the UK being set to be of one of a variety of sizes 324 ELECTRONICS WORLD- WIRELESS WORLD April 1990 MAKING ELECTRONICS C.A.D. AFFORDABLE TINY -PC PCB CAD, FOR THE PC/XT/AT Ensr-Pct - Are you still using tapes and a light box? - Have you been putting off buying PCB CAD software? BRITISH - Have you access to an IBM PC/XT/AT or clone? - Would you like to be able to produce PCB layouts up to 17" square? - With up to 8 track layers and 2 silk screen layers? DESIGN - Plus drill template and solder resist? - With up to eight different track widths anywhere in the range .002 AWARD o to .531"? 1989 o - With up to 16 different pad sizes from the same range? o - With pad shapes including round, oval, square, with or without hole and edge connector fingers? - With up to 1500 IC's per board, from up to 100 different outlines? 0 o - With auto repeat on tracks or other features - ideal for memory planes? - That can be used for surface mount components? - With the ability to locate components and pads on grid or to .002" o1:(sld oaoo resolution? - With an optional auto via facility for multilayer boards? - With the ability to create and save your own symbols? hRONI 000 0 0 0 0 \\` A - That can be used with either cursor keys or mouse? ` - That is as good at circuit diagrams as it is at PCB's? - Which outputs to dot matrix printer, pen -plotter or photo -plotter (via bureaux)? - Where you can learn how to use it in around an hour? 49 SMITH CHART PROGRAM CIRCUIT ANALYSIS BY - Z MATCH COMPUTER ANALYSER II For IBM, PC/XT/AT and clones inc. Amstrad 1512 For IBM PC/XT/AT and clones inc. Amstrad 1512, and 1640 and BBC B, B+ and Master. 1640, R.M. NIMBUS, and BBC B, B+, and Master. Rif .CO[1.=R.731 - - [ WHILE/16M IIIWIRDS : RN611:119.57 0E6 l 'yf-1,~ GENIRRIOR=N.R113 SNN=6.11 I0RD4.1577 TV IF AMPLIFIER R=1.6 X () KEYS : i R/6 CIRCLE ext. N1/4, v . ` ` PC FONT 7 // 1=1.11F -R , Henries NORMRLISEDI Zo=51 OHM 0.167K113.265 FRED=10 MHz /INPEDRNCE-Ohas: "ANALYSER II" Analyses for DIELEC.CONSTRNT=1 8.343+113.244 - complex circuits GAIN, PHASE, INPUT IMPEDANCE, OUTPUT IMPEDANCE ~ I and GROUP DELAY overa very wide frequency range. Z -MATCH - Takes the drudgery out of R.F. matching problems. Includes many more features than the standard Ideal for the analysis of ACTIVE and PASSIVE FILTER Smith Chart. CIRCUITS, AUDIO AMPLIFIERS, LOUDSPEAKER Provides solutions to problems such as TRANSMISSION CROSS -OVER NETWORKS, WIDE BAND AMPLIFIERS, LINE MATCHING for AERIALS and RF AMPLIFIERS TUNED R.F. AMPLIFIERS, AERIAL MATCHING with TRANSMISSION LINE, TRANSFORMER and STUB NETWORKS, TV I.F. and CHROMA FILTER CIRCUITS, MATCHING methods using COAXIAL LINES LINEAR INTEGRATED CIRCUITS etc. MICROSTRIP, STRIPLINE and WAVEGUIDES. The program takes account of TRANSMISSION LINE LOSS, DIELECTRIC CONSTANT, VELOCITY FACTOR STABILITY CRITERIA AND OSCILLATOR CIRCUITS and FREQUENCY. can be evaluated by "breaking the loop". Can save days breadboarding Z -MATCH is supplied with a COMPREHENSIVE USER and thousands of pounds worth MANUAL which contains a range of WORKED of equipment. EXAMPLES £130 ex VAT for PC/XT/AT etc. £195 ex VAT for PC/XT/AT etc. £65.00 ex VAT for BBC B, B+ and Master £130 ex VAT for BBC, B, B+ and Master All major credit cards accepted Harding Way, St Ives, Huntingdon Cambs, PE174WR Tel: St Ives (0480) 61778 WRITE OR PHONE FOR FULL DETAILS:- REF WW (5 lines) We provide full after-sales support with free telephone 'hotline help' service. Number One Systems Ltd Software updates are free within 6 months of purchase date. CIRCLE NO. ¡¡7 ON REP!) CARD April 1990 ELECTRONICS WORLD+ WIRELESS WORLD 325 APPLICATIONS Single -chip signal conditioner The FX506 single -chip audio processor In Rx mode the chip takes recovered In Tx mode, Mic I (or Mic 2) is will replace all the components associated audio and the RSSI signal from the IF selected, and audio brought out at the with Rx/Tx audio and squelch signal circuit. Internally, the audio signal is microphone output pin. The micro- processing in a cellular radio. It counts separately applied to speech and carrier phone signal may he pre-processed total elimination of manual adjustments squelch circuitry. Audio is passed to the prior to amplification. But, as the as its principal design feature. loudspeaker power amplifier and a logic microphone signal is low level, low - FX506 is in three sections. The pre- signal, indicating noise squelch or RSSI noise external filters should he used. process path will set incoming Rx or Tx validity, to the microprocessor. Signal- The Tx voice signal is amplified by the audio to levels and frequencies for ling and voice scrambling (analogue or on -chip amplifier. giving up to 20dB of amalgamation with auxiliary systems digital). may he added externally. The gain. Microphone audio is selected via such as scramblers and sub or in -band remaining inputs are a serial data bus the input select switch which applies the signalling schemes. The post -process interface to the radio's host micro- signal to a 16 -step digitally controlled path further adjusts the signal's level processor and usual power supply and trimmer. giving a further I5dB of gain in and frequency characteristic for input to clock interfaces. ldB steps. the voice sig- a loudspeaker amplifier or transmitter After amplification, Tx modulation inputs. The squelch-signal Programmable trimming nal is applied to the voice -operated gain processing path filters and monitors The absence of gain setting, volume or adjusting device (vogad) which acts as a noise or RSSI signals against a predeter- squelch adjusting components relies on low -distortion limiter. Attack and mined threshold. digitally programmable on -chip trim- decay times are adjusted by choosing a In Tx mode, the chip accounts for two mers. These are typically adjusted by suitable value for the external compres- microphone inputs and modulates the the host microprocessor through the sion capacitor. The vogad is a true AGC VCO and reference oscillator (two - serial bus. Squelch and volume controls device rather than the 2:1 dynamic coin - point modulation). operate in the same way. pander often found in cellular systems. LEGEND PRE-PROCESS PATH Mic 1 I# =Controlling logic bit number/5 select(switch) Compression capacitor n 'Adjustable element, n=Number of steps *3,4,5,6 #7 #8 *9 # 10,11,12,13 Mic. 2 Input select Bias r 16 WC Output 166 Pre-process audio output Rx Audio input MUX Amp output 300H z 3001Hz Pre-process gain Input gain amp Compressor (VOGAD) Amp input Input i H P.F Input LP.F (-2.75dB to +1.0dB) (0 to 15dB) 6.0dB gain Gain Gain(26dB) Test Test Bias Op amp 11,2 Rx(noise) Test signal path # 36 (- +20d8) Internal signal path Audio output ADO Internal signal path (Rx) # 28,29,30,31 POST-PROCESS PATH Output drive *32,33,34,35 #16 select 16 i 16 I r Bios (Nor/wide) #18,19 VCO drive #15orB #17or B #AorB r Test r (Tx) Post r dB Process process gain i 1 select 20dBi 2550Hz 4 dec 7 cec #27 2dB I MU #14 - -w VCO 3000Hz ref output De (Te) P e -emphasis Limiter Post deviation -emphasis External audio limiter filter process input El 16 1 Internal I Bias Process by-pass it 23,24,25,26 process # 20,21,22 VBias logic Output drive Rx (noise) SQUELCH SYSTEM Squelch system Serial data Function control input Bns(#) # 41,42,43,44-16 Serial input hip select # 40 r port \ # #45,46 *Enable noise (Nar/wide) Bios Threshold Squelch Serial lock drive input I , V36 (--\r +II Enable noise Squelch level comparator Xtal /clock 40MHz Clock Squelch detect oscillator *37,38,39 Squelch select and Xtal (-3 0dB to +4.0dB ) logic Noise output Noise input R.S S.1 326 ELECTRONICS WORLD + WIRELESS WORLD April 1990 APPLICATIONS Bandpass (300-3000Hz) filters to CEPT four digitally controlled trimmers. The to an on -chip programmable filter, the follow the vogad stage with pre-process overall range of adjustments per drive output of which is rectified to produce a gain set by a digitally controlled trim- output is 28dB in 0.25dB steps. signal on the noise output pin. Having mer, giving 4dB range in 0.25dB steps. Received audio from the demodula- filtered and rectified noise. the signal is The signal may take one of two paths: tor would be applied directly to the externally integrated and applied to a an internal route to the rest of the Tx input select mux and the noise squelch comparator via the squelch select mux. processing cells via the process select bandpass filter. The received audio, Chip functions. excluding the squelch switch; and an output to external audio having been selected through the input system. may be powered down during processor options. The signal, having select mux, is applied to the input gain standby to reduce current consumption. been externally processed or internally amp. The digitally adjustable trimmer, routed, is applied to the process select with other circuit elements. is re -used in switch and amplified by the post -pro- Rx and Tx to reduce the size and com- Automated testing cess gain cell. plexity of the chip. Automatic test equipment and the A hard deviation limiter is followed Received audio is externally or inter- radio's host microprocessor can com- by an anti -splatter filter/limiter with a nally routed to the process select switch municate on a data bus. iteratively mea- cut-off frequency adjustable for and gain adjusted. Rx signals then pass suring and adjusting levels without 12.5kHz or 25/30khiz channel spacing. through the limiter. which doubles as an manual intervention. Once the radio is Next in the Tx line-up is the output ignition noise suppressor. The low-pass fully aligned, the information on the set- drive selector, which selects one of four filter smoothes any harmonics which tings of the digitally controlled trimmers possible inputs. The test input derives result from the ignition noise -suppres- would he blown into the radio's prom. from the Tx audio path prior to the sion process and also reduces high -fre- Synthesized radios suffer from a non- vogad circuitry. which lets the test quency radio noise. linear conversion gain characteristic. engineer apply tones directly to the After pre -emphasis. the audio signal depending on which channel is selected. modulator input, making test and set-up is passed. via the output drive select By characterizing this effect, software of deviation easier. mux, to both sets of digitally controlled would be written adaptively to adjust The final Tx process path stage con- trimmers. The top set of trimmers acts the deviation level depending on the sists of two drive outputs which couple as the volume control in Rx mode and channel number selected. the modulating signal to the VCO and would be adjusted by the user via the reference oscillator of a synthesized host microprocessor. The squelch cir- Consumer Microcircuits Ltd radio (two -point modulation). 1 Wheaton Road Fine and cuit can he operated by channel noise or Witham coarse adjustment. with balancing of an RSSI level. from the local IF chip. Essex CM8 3TD the two drive levels. is achieved using all Noise from the Rx audio input is applied Phone: 0376-513833 Wideband GaAs amplifier Receivers for radar beacons, missile input can vary the open loop gain of the ance but it should he by-passed exter- guidance, fuse activation and comer - amplifier for automatic gain control and nally with a 10µF aluminium electrolytic measures are among the wide range of mixer applications. capacitor to prevent low -frequency sta- applications for National Semiconduc- The amplifier is internally by-passed bility or oscillation problems. tor's LH4200 general-purpose GaAs fet to improve high -frequency perform- There are three inputs. two high amplifier. It operates from 500k11z to IGI Iz. Fig. 1. The basic test circuit and results (see table, left) It has a GaAs input stage to give the high -frequency performance and 10V bipolar second and third stages for low output impedance. Feedback can be 33I1 included for gain stabilization and input impedance improvement. A control Description f(MHz) Typical (dB), Power gain2 with 10 50 V1n1=0V and 100 37 0.01µF Viii2=+1.5V 500 18 1000 3 I 0.01 µ F Power output 10 15 at 1dB 100 14 I compression 500 6 "tC2 1000 1 AGC range 100 60 with VG2=-2V L1 Noise R5=50 10,500 3 Noise Rs=800 10,500 2 1. For power output, this column reads in dBm. 2. Power gain measurements are taken with the Í" LH4200 open loop. April 1990 ELECTRONICS WORLD+WIRELESS WORLD 327 APPLICATIONS RF In impedance gates for signal input and a low -impedance source for series mode feedback. Normally the first input is RF Output the o used as the signal input, while Matching second controls the gain of the amplifier network for AGC applications. + 10V Gain control ranges of more than DI HP 5082-2824 o 60dB are possible to 100M11z. The second input is biased at + 1.5V for maximum gain and -2V for minimum 3311 33"'SI gain. The second input and the feed - " µF hack input (pin 3) are normally 0.1 µ F by-passed with 0.OIpF capacitors for l"IF 0.11 maximum gain. LH4200 0.1 u.F The second input can he used for iso- 10k lated small -signal operation. The open LH4200 loop gain at this point is about 60dB less 10k. than for the first input. 3k When used as a feedback amplifier, vW the third input is connected to the out- 0.1 µF put with a suitable resistor to set the T8-70pF 0.1 overall power gain. In this way, voltage 3k series feedback establishes the power i. Ws! gain and increases input impedance. Fig. 2. This type of amplifier configuration can provide 60dB gain at up to The unit's performance degrades 100MHz bandwidth. from the ideal above 250MHz. Input impedance decreases and is capacitive while the output impedance increases providing feedback from source to gate ning design are 5pF for C,. 3OpF for C,. and is inductive. For maximum per- of the input GaAs let. The resonator 6OpF for C3 and 150n11 for L,. For 150 to formance from 250 to 900M 11z, some network L, to C, is coupled to the active 300MHz these go up to 3, 6 and 10pF performance improvement can he device through C,. Typically at 75 to I011111 respectively and, for 300 to obtained through suitable matching and 150MHz. approximate values for begin - lz. 1.5. 3 and 6pF and 50n11. networks. 500Mí Video diode receivers are another The LH4200 can be used as a Colpitts possible application (see Fig. 2). These oscillator above 500N Hz. It is stable. Fig. 3. The fet input structure allows are much less sensitive than their super- has load isolation, and will provide circuit cor{fguratiorrs with AGC heterodyne counterparts, but they are + 15dBm to a 500Q load. This is shown provided by the envelope detector, U,, simpler. Typical applications include in Fig. I with capacitors C, and C3 and amplified by the L.11358 radar beacon receivers, missile guid- + 10V ance systems as well as signal monitor- ing and power levelling detectors. This 100k circuit has two LI14200s cascaded to give a gain of 60d13 with a bandwidth 3351 greater than 100MHz. Series -mode feedback provides high =10 input impedance over the operating fre- quency range and low noise figures from 0.01 high source impedances. Measured Input noise figure is 7dB from a 50Q source II I and less than 4dB from a 1k52 source. Figure 3 shows an AGC application. 0.01 This circuit provides a constant RF out- put signal level over a broad range of HP 5882-2800 input signal levels. Diode D, provides a DC signal proportional to the RF out- 1N914 D1 put level. This signal is compared to a reference voltage at the input to the LM358, which in turn controls the volt- 27k loon age at the amplifier's second input. 100k controlling its gain. LM 358 National Semiconductor Ltd The Maple 1Mn To.01 Kembrey Park Level + Swindon adjust Wilts SN2 6UT -5V Phone: 0793 614141 328 ELECTRONICS WORLD+ WIRELESS WORLD April 1990 KESTREL V. SECOND USER ELECTRONIC 1 - EQUIPMENT SALES COMPONENTS LTD. Logic Analysers o * All items guaranteed to manufacturers spec. HP 1630G 65 channels Logic Analyser £2250 HP 16310 Scope/Logic Analyser £3000 * Many other items available. Tek 1230 Logic Analyser - 16 channels £1225 3 `Exclusive of V.A.T. and post and package' HP 165A 80 channels Analyser POA Protocol Analysers 1+ 100+ 1+ 100+ HP 4951B/001 £1600 HP 4951C/001 £2400 4 Z8530 2.00 1.00 2732A 2.20 1.85 HP 4953A (High Speed .Analyser) POA 2764A-25 2.20 1.65 Z8536A 2.00 1.00 HP 4955A (High Speed Analyser) £4500 Z8OB CPU 1.20 0.65 27C64-25 2.20 1.50 Miscellaneous Z8OB CTC 1.20 0.65 27128A-25 2.40 1.75 4 HP 8112A 50 MHz 32V pulse generator £2800 Z8OB (CMOS) CPU 1.40 1.00 27256-25 2.60 1.70 HP 7550A Multi Media Plotter £1800 Z8OB (CMOS) CTC 1.40 1.00 27C256-25 2.60 1.75 HP 7570A Al Plotter RS232 I/F £2100 74LS00 0.13 0.07 27C512-25 4.80 3.30 IBM PC ATX 30Mb Mono System 512KB £1100 74LS125 0.14 0.11 6116LP-150 1.20 1.00 IBM PC ATE 20Mb Mono System 512KB £900 Model Mono POA 6264LP-150 2.60 1.95 Compaq Deskpro 286 20 System 74LS138 0.14 0.09 Yokogawa 3081-21 30 channel Recorder £2750 74LS175 0.14 0.11 8251A 1.30 0.95 Tek 2465A 350MHz Oscilloscope £2250 8 74LS240 0.28 0.22 8156D-2 1.60 1.00 Stag PP39 Prom Programmer (Module Extra) £450 74HCO2 0.12 0.08 8255-5 1.30 1.05 Stag ZL30 PAI Programmer £1200 Fluke 1722A 74HC147 0.20 0.10 82C55 1.30 1.00 Instrumentation Controller £1950 Dranetz 646-3 Mains Analyser £3850 8085A 1.00 0.70 6 74HC373 0.22 0.18 Dranetz 626 Mainframe+Plug-Ins POA 74HCTOO 0.12 0.07 8259AC-2 1.00 0.60 Intel ICE 186/286 etc. POA 74HCT 153 0.27 0.22 6845P 1.70 1.25 Microtek MICE 11+80186 Stand Alone Emulator £3750 74HCT373 0.22 0.15 6850P 1.00 0.60 Tek 4111 Graphic Terminal+IMb RAM £4500 1 Epson FX105 Printer £250 74HCT574 0.22 0.20 8250AN 4.60 3.00 Roland DXY 990 Electrostatic A3 Plotter £600 1.8432MHz Crystal 0.82 0.68 Z80A CPU 0.80 0.65 Sun 3/60C-4 Colour Workstation £5500 4 meg crystal 0.60 0.27 Z80A CTC 0.80 0.45 HP 7586B 8 Pen Size AO Rollfeed Plotter £4500 3 6 meg crystal 0.60 0.27 Z80A P10 0.80 0.50 All memory prices are fluctuating daily, please phone to confirm prices. DESIGN EQUIPMENT SALES 6 178 Brighton Road, Tel: 0344 861364 Purley, Surrey CR2 4HA Fax: 0344 411329 4 Tel: 01-668 7522. Fax: 01-668 4190 CIRCLE NO. 134 ON REPLY CARD CIRCLE NO. 135 ON REPLY CARD WE CAN COMMERCIAL QUALITY A SUPPLY: VHF/UHF RECEIVER CABLES, CONNECTORS AND ACCESSORIES _ -- 1i::::::=::;ti_;uGo', GENERAL COMPONENTS A R.F. COMPONENTS r tl:. R.F. ACCESSORIES r-` - -rr--.'`-- íi ¿la ti KU Attenuators, filters, couplers, etc. Inkr. __._ i.a.l ! _. s_. ow . +w. 1.01.17-1. V ; DESIGN AND o. I MANUFACTURE: The IC -R7000, advanced technology, continuous coverage communications receiver CABLE ASSEMBLIES AND TEST has 99 programmable memories covering aircraft, marine, FM broadcast, E For LEADS Amateur radio, television and weather satellite bands. simplified operation and quick tuning the IC -R7000 features direct keyboard entry. Precise frequencies R.F. ACCESSORIES can be selected by pushing the digit keys in sequence of the frequency or by tuning Switched attenuators, SWR bridges etc. the main tuning knob FM wide/FMnarrow/AM upper and lower SSB modes with SIMPLE ACTIVE CIRCUITS 6 tuning speeds: 0.1, 1.0, 5, 10, 12.5 and 25kHz. A sophisticated scanning system B provides instant access to the most used frequencies. By depressing the Auto -M including PCB production switch the IC -R7000 automatically memorises frequencies in use whilst it is in the R.F. AMPLIFIERS scan mode, this allows you to recall frequencies that were in use. Readout is TEST GEAR Oclearly shown on c dual -colour fluorescent display. Options include the SIMPLE RC -12 infra -red remote controller, voice synthesizer and HP -2 headphones. A Icom (UK) Ltd. Tel: 0227 363859. Telex: 965179 ICOM G N.B. For Wales and the West contact: WAVEBAND is M.R.S. Communications Ltd. Cardiff. Tel: 0222 220167. ELECTRONICS Please send information on Icom products 8 my nearest Icom dealer. N Name/address/postcode: RING: 074 571 2777 Job Title:...... Tel: ...... Howell, Denbigh, Clwyd LL16 4AN D 3 Lon Post to Icon, (UK) Ltd Dept.WW, FREEPOST, Herne Boy, Kent CT6 8BR CIRCLE NO. 136 ON REPLY CARD CIRCLE NC). 137 ON REPLY CARD April 1990 ELECTRONICS WORLD + WIRELESS WORLD 329 LETTERS In a spin Before Harrison assumes the As a longtime, 40 years, reader Asic angst of your magazine, I am inertial mass of a mechanical pleasantly surprised to find that object remains constant while It was with great interest that I As most equipment has a you are giving space to undergoing rotation, he should read "In depth - asic" in the limited production life - due to gyroscopic phenomena: make a measurement and May 1989 issue, articles which advances in technology and the "Harrison Gyroscopes", confirm or disprove his dealt with the designers' and need for change to boost sales - December 1989 EW+WW. findings. industry aspects of using asics. new products are developed, I have beens studying this for The fact that the inertial mass Two other groups of users are requiring new asics. 20 years. The quaint armchair of a rotating gyroscope is worth remembering: the As an electronic maintenance observations of Leonhard Euler variable and anisotropic customer and the maintenance engineer, I have two questions which have been codified as invalidates general relativity as engineer. for the asic - related Euler's Equations of well as opening the door to By definition, the asic is an manufacturing industry. Firstly, Gyroscopic Motion are of exploring outer space using "application -specific integrated is the manufacturer willing to historical interest but for a antigravity machines and space circuit"; it is, in effect, a very stock expensive chips for mankind which sets its eyes on drives based on the principle of limited -application chip. The maintenance purposes, knowing the stars, totally obsolete. variable inertia. production batch size will that he can't liquidate them There are many mistakes in What is tragic about Harrison therefore be very small in through component retailers? Euler's observations but so not and his dynamicist friends is comparison w ith consumer ICs And secondly, will the customer to be prolix I suggest there is an they forget physics is an and there will be no second - not be compelled to huy new assumption in his work which is experimental science where sourcing. equipment, once the old breaks unjustified and incorrect. progress is made in the The size of production runs down, due to unavailability of Encoded in Einstein's general laboratory not in the armchair. will most certainly be reflected spare asics (say after five or ten theory of relativity is the The basic assumption is that in the cost per chip; the asic years). assumption that inertial mass is rotation does not affect the might be the most expensive In effect: will manufacturing an invariant except at light properties of mechanical part in the equipment being industry he holding the speed velocities. This is wrong. objects. Unless this assumption manufactured. This will be consumer to ransom? Harrison should experiment is tested there is no reason to offset by the use of fewer Marc Cornelius to determine whether the accept the "standard components and a smaller PCB Jette inertial mass of a gyroscope interpretation" of gyroscopic size. Belgium remains constant under phenomena. precession. The standard I suggest some additional observation is rotation does not experiments which may be affect the properties of objects. performed in a short This is incorrect. If an demonstration at The City Mac is tosl+i test eproms programmed. apparatus is constructed which University, London: I agree with Mr Spyker's A programmer wrote the consists of two identical Measure the period of a comments on the Apple eprom-based digital signal gyroscopes rotating in opposite swinging pendulum with a Macintosh in his letter in processing software to let it be directions, co -planar and with rotating bob; December's EW+ WW. used as a spectrum analyser/ axles parallel, experiments can Measure the momentum Designed around the excellent digital storage oscilloscope. As be performed on rotating transfer in the elastic collision 68000 CPU, with its 32bit he had no resources, an Apple objects without the interference of a rotating object with a internal architecture and Macintosh with a set of of gyroscopic forces. Thus he nonrotating object; symmetrical instruction set, the programmer's development can determine that the inertial Measure the momentum Mac should have been streets software tools was loaned to mass of the precessing transfer in the elastic collision ahead of the PC, handicapped him. gyroscope increases. of a precessing gyroscope with a by the peculiar architecture and Eventually the suite of The substantial increase in non -rotating control; and strange instruction set of its software was completed - all the inertial mass of a precessing Drop the rotating gyroscope 8086 processor. But no - 51 Kbyte of source code - and it gyroscope, 18-21% in completely enclosed in a case lumbered with that horrible was ready to be assembled and measurements made at and see if it falls at the same mouse/icon user interface and tested on the recently precessional angular velocities acceleration it would if the an overweight operating system completed prototype of the new consistent with the precessional internal gyro were not that gobbles up memory and computer. The disk was put angular velocity of the same rotating. CPU time - it crawls along at a into the Mac. Its disk drive gyroscopes under the influence All of these experiements pace that makes even a bottom - ground and grated away for 56 of gravity, renders invalid the show deviations from the of-the -range PC seem like a minutes before the assembler Newtonian interpretation of the classical results obtained with supercomputer. completed its task. The balance of forces necessary to non -rotating masses. Three years ago I designed a software did not work the first maintain the gyroscope There is more, but the basic 68000 -based single -board time and, each time the poor precessing on the end of a point is the unstated assumption system. I needed to write programmer made some string. that the mechanical properties software to test the system and, alterations, we had to wait an This confusion is because of rotating and non -rotating not having a 68000 -based hour as the Mac assembled it. experiments are constructed in mechanical objects are computer, I obtained a 68000 To make matters worse, the which the forces of gyroscopic identical. This assumption is cross -assembler and used my output files produced were precession are not cancelled incorrect. home-made Z80 -based S-100 intended to be run on a and interfere with and confuse Bruce DePalma bus CP/M system. The resulting Macintosh and not exported to the interpretations of the President binary files were downloaded to an eprom programmer; experiments. DEC an eprom programmer and the additional programs had to he 330 ELECTRONICS WORLD + WIRELESS WORLD April 1990 PHONE TELEX 0474 560521 P. M. COMPONENTS LTD SELECTRON HOUSE, SPRINGHEAD ENTERPRISE PARK 966371 . FAX SPRINGHEAD RD, GRAVESEND, KENT DA11 TOS PM 0474 333762 8HD - Á selection from our M8079 6.00 00203 1C 42.50 ON"? 2.50 40X'0000 6C180 2.95 7Y4 2.50 30'4MR 1.00 5636 5.50 8082 7.50 00206 40 45.00 xP' '600A 25.00 425.00 6CM7 2.95 888 2.50 30P'2 1.00 5642 9.50 stock of valves M8083 3.25 0575 20 1.50 99' 32000 79.50 4C815000 636 0.75 80'0 2.50 309'8 0.60 5643 9.50 branded M809' 730 0595'0 4.85 XR1 64000 475.00 6CS7 0.95 8805 1.95 30P'9 1.00 565' 2.50 M8096 3.00 05'08,45 4.00 149.50 40X50006 6Cw4 8.00 8CW5 1.50 30P' 2.50 5654 1.95 011'4 24.50 E8109 25.00 0E8065 25.00 M8098 5.50 05150'5 6.95 965 6.95 1000.00 6CX8 3.95 81088 1.50 3091'3 0.60 5670 325 A1834 7.50 1.00 11148 E9812 0.65 K48099 5.00 05'50,30 1.15 801100 75.00 402' 4 '25A 6CD6 2.35 8901 1.95 30'1'4 1.75 5672 4.50 02087 11.50 EA50 1.00 EF1200 1.50 608100 530 05150m0 7.00 71'060 265.00 85.00 6D18 1.50 lOD2 1.25 3'126C 7.50 5675 28.00 A2134 14.95 0052 75.00 E9P60 3.50 M8' 36 7.00 05'205 3.95 71'020 42.50 4032 125.00 6DJ8 100E7 2.50 33A '581A 19.50 5678 7.50 A2272 15.00 1076 1.95 EH90 0.72 608137 7.95 05'2'3 5.00 Bl'060 195.00 4E27A 125.00 SPECIAI 3.50 00X8 2.50 35A3 3.95 5687 4.50 02293 6.50 1679 1.95 EK90 1.50 608161 6.50 01137 9.50 11'070 195.00 4G57 225 6006 1.50 'OE88 1.95 3565 4.50 5696 4.50 A2426 29.50 1.95 EABC80 E132 0.95 M8'62 5.50 0V03'2 6.50 81107' 195.00 4Gv7 2.25 6005GE 11.95 'OEW7 2.95 35C5 4.50 5701 3.50 A2599 37.50 EAC91 2.50 0134 M8'63 5.50 OVOS 25 3.50 9L'290 65.00 4J6A 2.95 60068 230 '09i 1.95 351.691 2.00 5704 3.50 27.50 A2792 EAF42 1.20 ',AWARD POA 60b' 90 4.50 0906 20 29.50 Z77 120 4016 1.50 6D16A 1.50 '0GK6 1.95 3523 1.95 57'8 3.50 11.50 A2900 0834 1.50 EL3.95_ M8'95 6.50 OV08 '008 Z300T 6.00 4185° 150.00 6Dw48 3.50 01'4 2.50 35250' 3.50 5725 2.50 A3283 24.00 EB41 3.95 STE ME NS -TA- M8'96 5.50 145.00 Z302C 12.00 41150A 35.00 6E5 3.95 "E3 55.00 38HE7 10.95 5'26 2.50 A3343 35.95 889' 0.85 11.36 2.50 608204 5.50 083'25 85.00 Z359 9.00 40'50D 55.00 6EA7GE 4.50 "R3 5.50 40106 8.50 572' 2.50 ACSP3A 4.95 EBC33 2.50 EL3 648223 4.50 0Y4.250 105.00 27001, 9.50 4X5000 350.00 6EA8 2.50 '206 3.95 41 6.00 5'49 2.50 AC,S2°EN 8.50 EBC4' 3.50 608224 2.00 084 400 110.00 Z759 15.00 SA 101D 9.50 6E88 3.50 '2006 2.50 5005 1.50 575u 1.85 AC122 59.75 1.50 EBCB' 0142 2.00 M8225 3.95 R'0 4.00 303,. 18.95 SA' 52m 9.00 6EJ7 0.85 '2AE6 5.50 5085 1.95 575' 2.95 AH221 39.00 1.95 4.50 EBC9O 017' ME '400 3.50 P'8 2.50 ZM'020 8.50 56163K 10.00 6EM5 2.50 '2AH7GT 4.95 5005 0.95 5763 6.50 AH238 39.00 EBC9' 1.95 018' 6.95 ME40' 19.50 00' 2400 14.50 ZM'02' 8.00 59.70K 6.25 6EM7 250 '2015 1.00 50006G 1.95 58'40 325 AL60 6.00 10E80 0.95 1183 7.50 60E'402 29.50 1903 2500 6.50 '6'023 7.95 SA '8060 9.00 6E68 1.75 '2AT6 1,75 50E H5 130 5823 9.50 AN' 14.00 00983 0.95 -E184 -- 1.50 MHLD6 4.00 903 '250a 35.00 ZM'082 9.00 5A 2060 10.00 6E07 2.95 12617 1.95 50116 2.95 5829W4 6.50 ARP'2 2.50 013189 0.95 MP25 195.00 R03-250 15.00 ZM1084 10.00 5B-' 1060 10.00 6E0.6 1.50 12AT7WA 3.50 53KU 4.50 5840 3.50 AR'34 1.25 0.95 MULLARD 4.50 MS4B E8993 5.50 RRE '250 35.00 Z601'62 9.00 513 25460 11.50 60W7 4.50 '2AU6 1.50 158' 3.50 5842 11.00 ARP35 2.00 E13121 4.50 0184 Ml, 4 3.50 5"E'2 38.00 ZM"75 6.50 5B 25560 14.50 6Fi 2.00 i2AU7 0.95 75C' 4.50 5547 10.95 4.50 AZII EC52 0.75 SIEMENS 2.501 N37 12.50 S'04 20 10.00 ZMI'77 9.00 58.256m 15.00 695 5.50 '265/6 1.95 80 4.50 5863 95.00 87'6 35.00 EC53 1.50 0185 430 N78 9.85 SC' ' 300 6.00 103 4.50 50 25760. 15.00 697 5.50 '2007 2.50 83 8.50 5879 9.50 BBB 55.00 EC70 1.75 h86 1.75 002 1.50 5'61 3.50 '0E4 3.50 58258M 1430 6G13 3.00 I2AX4G1B 2-50 836 7.50 5886 13.95 BT17 25.00 EC81 7.95 1190 1.75 OA2WA 2.50 STV280 40 11.95 0X2 3.50 5022 125.00 69'4 1.00 '2A97 1.50 850' 6.50 5894 39.50 811'3 35.00 EC86 1.95 019' 4.50 063 2.50 TB2 5 300 95.00 1822 10.00 5(180 230 69'7 2.75 '2AX7WA 2.50 85A2 2.95 5899 4.50 C1K 27.50 EC88 1.95 01.95 1.75 OB2 150 1B2 300 195.00 'B27 55.00 51'80E 1250.00 6'23 0.60 '20975 7.95 QOAV 17.50 S963 1.75 17.95 EC90 1.95 C3M E1'52 15.00 OB2wA 2.50 18.3 750 115.00 ' B3GT 1.95 5118 2.95 6924 1.25 '2AY7 3.95 90C' 3.50 5965 2.15 C ;149/1 120.00 ERC9' 5.50 EL360 6.75 OC3 2.50 103 2003 450.00 10350 45.00 5R4G1 4.95 6F25 1.25 '2046 4.50 90CG 17.50 6057 3.75 C1150 1 135.00 EC93 1.50 01500 1.95 OD3 2.50 T812 30C 395.00 '03 230 5124W01 5.95 6928 1.25 '2066 2.50 90CV 17.50 6058 2.50 C1'66 125.00 EC95 7.00 01504 1.95 0604 2.50 TB12 500 495.00 '14 2.50 514 5.95 6F32 1.25 '2BE6 1.95 Q'AG 9.00 6060 2.25 C1534 32.00 EC97 1.10 E1509 5.95 06058 3.00 TD03'nDE9 'NSGT 2.50 5180 1.95 6933 7.50 '28H70GE 92AG 25.00 6072 6.95 CCA 3.50 EC80'0 12.00 01509 0601 1.75 35.00 ' P28 25.00 51140 2.95 69H5 8.50 6.50 920v 25.00 6080 8.50 CD24 6.50 ECC32 3.50 M5l1ARD 730 01043 2.50 TT'S 45.00 '95 150 5Ú4G8 4.50 6918 15.00 '2816 1.75 950' 6.50 6080WA 930 CKI006 3.50 ECC33 3.50 EIS' 9 6.95 OR'S0 3.95 TT2' 45.00 '55 1.50 594G 2.50 6911 4.50 '2883 1.95 'OOE' 50.00 6'32 10.50 05676 6.50 ECC35 3.50 01802 3.65 2.50 TT22 45.00 '14 1.50 5W4 4.95 6°07 3.50 ' 28870 G E '08C' 2.50 6' 36 2.50 Nos P4' Cv PRICES ECCB' 1.95 182' 6.95 2.50 T1'00 69.00 '544 1.75 594 4.9S 60E5 3.95 6.95 '5082 6.50 6'46B 9.50 8104,15' ON ECC81 SPECIAL 0,822 12.95 'ABC80 0.95 1Y2 1750 105.00 'U5 1.50 513G1 3.50 6GH86 230 '2C8 2.50 '50C'K 9.00 61468GE 15.00 CX"40 495.00 QUALITY 2.95 01160 22.50 PC86 0.75 TY8 6000 1825 2.50 5Z3 4.50 6017 0.85 '2CAS 1.95 '5002 2.50 6'46w 12.50 3250.00 CX1528 ECC82 0.95 EM34 12.50 'C88 0.75 365.00 203 12.15 5Z4G ^ 2.50 6GK6 3.95 '2C46 1.95 '50C4 2.50 6'55 72.00 030 2730 ECC82 EMA' 3.50 PC97 1.10 U' 9 8.50 2AS15A 11.50 6130 2 0.70 60606 2.65 '200613 3.50 '8581 1.50 0 56 125.00 PHILIPS D63 1.20 1.95 EM83 1.65 PC900 1.25 L26 0.90 287 4.50 60'203x. 9.00 6GS7 213 2DW4A 3.50 6'57 2.50 22.50 1.50 D64' ECC83 EM84 1.65 'CC84..- 0.40 135 3.50 2822 69.50 607 4.95 6G98 0.95 '2D26 3.95 2300 boo o' 58 3.20 1750 DA42 ECC83 EM85 3.95 PCC85 0.55 037 9.00 2C36 70.00 6A8 2.50 6GwB 2.50 '2E' 19.50 23'D 1500 o' 66 650.00 4.50 DA90 BRIMAR 2.15 EM87 2.50 PCC88 0.95 1,4' 6.95 2C396 25.00 6007 4.50 6015 4.95 ;20'4 38.00 250TH 150.00 6'89 4.50 0099' 0.95 ECC83 EN32 15.00 'CC89 0.70 150 3.00 3C39A 32.50 6AC7WA 2.00 6G16 250 '1905 1.95 307 5.00 620' 6,45 PHILPS DA996 0.95 1.95 EN9' 2.25 PCC189 0.70 U82 3.00 2C398A 39.50 6005 2.50 68' 9.50 '1GN7GE 6.95 3280 15.00 6350 3.50 DC70 1.75 ECC83 EN92 4.S0 °CC805 0.70 U'9' 0.70 2C4" 37.00 60G7 2.50 6H6G1 2.50 1215GT 3.95 5'2B 49.00 6360 4.50 DC90 3.50 SIEMENS 2.50 E75 0.80 'CC806 0.80 1'92 1.00 2C42 29.50 6AH6 3.50 6H87 1.95 '217GT 3.50 7056 12.50 6386 14.50 PCE82 DCX 4 5000 ECC83 0970 7.50 0.80 '93 1.00 2C43 60.00 6924 3.50 61-195 12.50 '2428 2.95 7'3A 25.00 6442 75.00 25.00 SUPER 3.50 1581 2.95 PC980 - 0.65 u25' 2.50 2C5' 2.50 6017 2.00 6HP8 3.50 '2001 1.50 7'3A B 75.00 6463 7.50 DET'6 28.50 ECCBS 1.50 E982 1.15 PC982 0.60 U80 3.50 2CYS 1.50 6AKS 1.95 6HMS 2.50 '2K8Y 1.95 7246 275.00 6550A 9.95 DE1'8 28.50 ECC86 2.75 0983 1.50 PC F84 0.65 u0BC80 1.00 202' 2.25 6AK6 2.50 6H05 330 '2027 1.95 725A 275.00 6550A G E 13.95 DE120 2.50 ECC88 1.50 E884 5.95 PC986 1.20 1,0942 1.95 1D2'w 3.15 6615 0.85 68156 4.95 '257GT 1.50 726A 75.00 6870 11.50 DE722 29.50 ECC89 1.50 E986 87 0.65 PC981 1.25 UBC4' 3.95 2E11 49.00 6AM4 3.25 68158 2.95 '250701 1.95 80' A 15.00 68838 3 E 14.95 0E023 35.00 ECC91 2.00 E188 1.50 °C9200 1.80 LBCB 1.50 2E26 7.95 60605 4.50 6H26 3.50 '2SG7 4.75 803 14.95 6973 10.50 0E124 27.50 ECC'89 2.50 0191 5.50 'C920' 1.80 UB980 0.95 2155 295.00 60M6 1.95 614 2.15 '2507 1.95 805 16.95 '025 2.50 DET25 22.00 ECC8O'S 6.95 E95006 2.95 PC980' 1.35 ,B989 1.00 2K25 59.00 6ANS 4.50 61501 2.50 '25,7 1.50 807 5.50 70255 6.95 DE129 32.00 ECC8035 6.95 14802 0.70 PC9802 0.85 4.50 .- 001.1' 2.95 2026 95.00 6AN8A 6J6 2.00 '25N7GT 1.85 8' A 6.95 70276 G E 12.50 D961 3.50 ECC804 0.60 EZ35 1.00 PC-B:; 1.25 5C92 230 2059 250.00 6005 1.75 6170 4.15 '2SW7 3.50 8120 12.50 '092 125.00 D99' 1.50 ECC2000 7.95 EZ40 3.50 RCF80k 1.00 UCC84 0.70 2K48 140.00 6008 1.50 6J136A G E 930 '2587 4.50 8'3 7 "9 9.00 130 1.15 13,92 ECF80 EZ4' 3.50 'C9831 1.25 UCC85 1.00 2056 250.00 6A55 130 6JE6C G E 12.50 '294 1.95 PHILIPS 35.00 7'89 5.50 0996 + 1.25 0C982 130 EZ80 - 0.75 PCH200 1.50 UC980 1.00 2024 5.00 60S6 2.50 61M6 10.95 '3D7 3.20 8'3 19.50 7'99 10.50 D991 1.25 1C986 1.70 028' 1.50 PCL82 -- 0.95 UCH2' 2.50 30 '078 12.00 6AS7G 4.50 (JUBA 2.50 '30E7 2.50 8290 22.50 724' 8.50 DG10A 8.50 ECF200 1.85 EZ90 1.50 PCL83 2.50 UCH41 2.50 30,1050 9.00 6016 1.95 6JS6C G 0 10.95 '3DR7 2.95 8330 65.00 475 5.00 DH63 3.50 EC9202 1.85 9W4 800 4.50 8084 _. 0.75 .,CH42 3.95 3A '098 11.00 6A18 1.75 628 5.95 '3E' 145.00 345 23.00 7486 155.00 09477 1.50 EC801 0.85 Ex 2535 195.00 PC185 0.95 LCHe' 1.95 309"0B 12.00 6AL-1C' 2.95 6K7G 2.00 '31"7 3.50 8660 8.50 752' 125.00 DK9' 1.20 EC9B04 6.50 G55 'K 9.00 0.95 1,0.01 1.75 3A '4'K 11.50 6AUSGT 4.50 6K8G 3.00 '486 4.50 872A 20.00 755' 8.50 DK92 150 ECF805 2.50 G1910 2m 6.95 9,.805 UCLB3 2.50 3A '461 7.50 6010 1.50 6006 G E 11.95 1497 3.50 873 60.00 758' A 11.95 D135 2.50 EC9806 10.25 G240 2D 9.00 U94' °D5CC 5.95 2.25 3Ax147J 7.50 6Av6 1.95 60G60 6.95 ' SE 5.50 954 1 00 '586 15.00 DL63 130 ECHO 4.50 GC'OB 17.50 PEN25 2.00 L942 2.25 30 '67M 10.00 6AW8A 330 61' 2.50 '6A03 1.95 955 1.00 1587 19.50 0170 2.50 ECHO 4.50 GC10D 17.50 °EN401) 3.00 1980 1.75 3030 3.95 60X401 1.95 61.6 3.50 '6G85 2.95 '802 1950.00 759'4 10.50 0173 2.50 ECH35 3.50 WO 15.00 PEN45 3.00 U985 1.20 3A4 1.50 60138 1.95 6H 0.40 '849 315.00 78'5 59.50 D191 3.95 E0142 1.50 GS'OH 12.00 PEN45D1) 3.00 u989 2.0C 3A5 4.50 6028 1.50 6L6G1 3.50 I '61 0.40 '927 25.00 7868 8.50 0192 1.50 ECH81 1.75 GS'2D 12.00 °EN46 2.00 0144 3.5C 3AT2 3.35 6849 10.50 617 3.50 '708 3.50 2040 25.00 7895 17.50 0193 1.50 ECH83 1.50 G1'C 9.50 0.95 "1200 - 14184 1.95 3822 25.00 61380 2.50 6L'S 3.15 7AX4GTA 1.95 2050A G E 9.95 8'56 9.95 D15'0 13.50 ECH84 1.50 GU20 35.00 P136 - 1.75 1185 0 85 3826 24.00 68'0 1.95 bt'9 3.95 '78E3 2.50 42'2H 250.00 84'7 10.95 D15'6 10.00 001200 1.50 GU50 17.50 1.50 UU5 3.50 3828 15.00 61306 1.50 6LJ8 2.50 '7DW4A 2.95 447' 35.00 8950 10.50 DM70 5.25 EC180 1.00 GIL' 13.50 P12_ - 1.50 UU6 6.00 38Z6 1.50 6807 4.50 61020 2.50 "Ew8 1.50 468'A 9.50 8042 10.50 6.50 0M'60 C1B2 1.50 001.13 24.00 0182 0.60 11,7 8.00 3C45 39.50 6008A 3.50 6196 G 1 12.50 ' 7JZ8 8.50 5544 79.50 9002 6.50 DOD -006 79.50 ECL83 2.50 GXUSOSS 14.50 PL83 0.85 U58 9.00 3CX3030A7 6BC8 1.50 6L06 GE 12.50 '803 6.00 5559 55.00 9003 8.50 095' 1.50 ECL84 1.00 GY50' 1.50 9184 - 0,85 1Y4' 3.54 650.00 6883 2.95 6L18 9.25 '8G85 3.50 0986'87 r 0.85 0C185 0.95 G1802 1.50 '1500 1.50 (1985 0.70 3CYS 1.50 6BE6 1.50 6'28 2.00 '9005 3.50 D9802 0.85 EC186 -r 1,1 GZ32 4.50 P.504 1.50 V235A ' K 302'A 2950 6BG6G 3.00 607G' 2.50 '9A1,4G7 2.50 0551 4930 lCt805 0.95 GZ33 4.50 P1508 1.50 250.00 3E22 49.50 68816 1.95 6R7 3.15 '98Go 3.50 E80CC 25.00 19370 2.50 GZ34 4.50 P1509 4.85 v7380 ' K 3E29 39.50 60818 1.50 6540 1.95 '903 19.50 Valve Test Room Service E8OC9 12.50 0139 1.50 G13" 4.50 Pi 52 499 295.52 3E17 1.95 6016 1.50 6SA7 1.95 '9Go 9.00 8 matching of power valves - add E80F 12.50 0940 4.50 HBC90 1.95 91802 6.00 V246A 'K 3H 0.40 6004 6.50 65C7 1.95 '9H4 35.00 C1 per valve. 0801 29.50 1942 3.50 Hl4' 3.50 118021 3.50 250.00 31 '700 1450.00 6016 85.00 65947 1.95 '9115 33.50 8 selection or low microphony - E8'CC 5.50 E950 2.50 H190 3.50 P1820 2.95 924,' 70 31 0.40 6818 1.15 6S1701 1.95 9.50 20CV add El per valve 0811 12.00 EE54 4.50 K18C 7.00 19832 .- 0.60 315.00 304 2.50 68606 115.00 1.95 200' 1.50 E82CC 4.50 E955 4.95 K133C 9.33 3.50 - 0.50 V24'C'K 304 3.50 68N6 1.65 65170' 2.50 201=6 76665557770C:73.15 E83CC 4.50 E970 1.20 036 2.91 PY8' 0.8S 195.03 4-65A 85.00 68N8 3.95 204' 0.955 E83F 5.50 E972 3.50 K144 5.95 PY82 - 0.85 0453 12.00 4-250A 105.00 6005 1.50 650701 4.50 14;.,___4.410.55 0973 PY83 0841 6.50 3.50 K145 5.9S 0.85 61563' 10.95 4 400C 95.00 60076 1.50 655' 1.95 4 086C 9.50 E980 0.55 KT61 7.95 188 `' 0.99 W48 9.50 4 1000A 495.00 6087 4.95 6T8 1.50 20'5 1.15 E88C 7.95 EF83 3.95 K163 2.95 PY5604- 1.95 vP4 4.95 4832 35.00 6057 5.50 6,601 3.50 2'126 10.50 EBBCC 4.50 0'85 0.85 0166 1SA 11.95 PY800 0.95 vR'0' 2.50 48070 1.75 6BW6 3.95 611G 330 2'<06 4.95 CALLERS WELCOME E88CC-0' 6.95 1966 3.50 KT66'EC NP PY80' 0.95 OR' 05 30 2.50 4BZ6 1.95 6EW7 1.50 6580 1.50 2'LL8 3.75 OPEN MON-THUR 9AM-5 30 PM 088CC 5.95 E986 04085 "- 5.00 083 330 72.00 68'50 30 250 4C28 25.00 6BZ6 2.50 6560 r 1.95 248' 39.50 MULLARD 5.95 750 KT67 9.00 003 '54 139.00 v39 2.50 4C35 95.00 68Z7 2.95 6060' 2.50 2489 39.50 FRI 9AM-5 OOPM 7.95 1.95 KT77 E90CC EF89 GEC 14.95 085 350 595.00 w2' 4.50 4C525OR 115.00 6C4 1.95 6w4G1 1.95 25806 1.75 24 -HOUR ANSWERPHONE SERVICE E909 7.95 E99' 1.50 018' 7.00 00E "v: 5 19.50 W6' 4.50 4C935.000 605 2.50 686G 3.95 250068 2.95 ACCESS 8 BARCLAYCARD 091H 4.50 E992 2.15 0188 USA 12.95 00103-' 2 7.95 w'7 5.00 1650.00 606 3.50 602N 1.00 2516GT 1.75 092CC 3.95 E993 ISO KT88 00E03.20 35.00 W8'M 4.50 4Cv' 00 000 6C6G 2.50 604 1.50 29C' 19.50 PHONE ORDERS WELCOME 6.59 1.50 E99F E994 SELECIRON 00E06-40 45.00 W739 1.50 2950.00 609 4.95 605G' 1.00 29006 6.50 UK ORDERS P&P E' 01301 18.50 E995 1.95 15.00 00V02-6 19.50 4.24 430 4XC'25C 6(04 4.95 6080 2.25 30C'5 OSO PLEASE ADD '5% VAT E180CC 1030 E997 0.90 KiW'61 2.50 0043-10 5.50 X4' 450 EIMAC 150.00 6002 3.50 6160 4.50 3OC17 0.40 0180 0.50 1998 0.90 KTW62 2.53 00003 '0 X66 Xo5 3.50 4CX250B 45.00 6085 3.95 706' 1.50 30C'8 1.48 EXPORT ORDERS WELCOME E182CC 9.00 E9'83 0.75 KTW63 2.03 MUIIARD 15.00 XB' 6.90 400508m 6036 2.50 786 3.50 30012 1.35 CARRIAGE A' COST E'869 8.50 E9184 0.85 KTZ63 2.53 00003 20 25.00 0C24 150 65.00 6CDoG0 4.50 787 2.50 3C91'2 0.95 PLEASE SEND YOUR E'88CC 7.50 E973' 4.50 187 20 95.00 00006 400 xC25 0.50 4CO250K 6C96 1.95 708 4.50 309L'3 1.10 12.50 4.50 C9 ' FOR 12351 E9732 1598 6.95 27.50 4' 1.50 EIMAC 115.00 6(0' 3.50 117 5.56 3091' 4 1.25 ENQUIRIES SPECIAL 19.50 11.00 60529 E2809 01800 66.00 00606.100 'W5= 1.220 4CX250R 6CG7GE 5.25 707 7.50 3u1' 0.45 OUOTA'IONS OR LARGE 0283CC 12.00 E98=45 19.50 M5 43 155.00 ..RD 39.50 x='..5_ 15:30 AMPEPEx 125.00 60,5 6.95 1.50 3015 0.60 REOU REMENTS E288CC 17.00 098055 25.00 M5"99 295.00 0'3 ' 50 55.00 x1628-1 7.50 4C 3534 100.00 OCIO 3.25 70' 4.50 3.L" 0.60 CIRCLE NO. 138 ON REPLY CARD LETTERS run after each assembly to convert the files to a standard format compatible with an Gyroscopes and We have, therefore, a When considering this matter it eprom programmer. contradictions situation in which classical should be remembered that the Using my system at home, mechanics, as is presently analogue between the In your December 1989 issue which had been dismissed by interpreted, contradicts itself, conservation of angular and Dr I larrison restates the fallacy the first statement claiming to the programmer as "ancient, a linear momenta is mere which constitutes one side of explain the experiment which assumption and totally obsolete pile of junk", I does not the Newtonian contradiction. assembled the program to falsified the second as a general constitute a formal logical step. The fact that there is a case. produce a file that could be fed Perhaps this particular contradiction was revealed by directly to the eprom It is now for Dr Harrison to assumption lies at the roots of my initial experimental tell us when programmer - in just 6 minutes. how, using a our failure to unify the forces of observation some 20 years ago. The very next day, the Mac faultless chain of logic, a set of nature. On the one hand we have the was relegated to the three mutually consistent Alex Jones statement all observed receptionist and its place was axioms may be used to derive Swanage gyroscopic phenomena are taken by an elderly S-100 bus contradictory conclusions. Dorset quite adequately explained by CP/M system complete with 8in Newtonian mechanics." disk drives and a separate On the other hand we are terminal. To this day, this told, with equal certainty. that system is still in use for ho experiment to demonstrate that motion Can be "The centre of mass of a closed used without the need for a reaction in an developing 68000 software. equal system of components cannot end Opposite direction. I work for the microcomputer alter its condition of rest or A flywheel wee auepei ded with its axle of rotation et right angles to e side of a university computing shaft by means of a universal ball ,joint. The abaft wee carried within a frame uniform right line motion unless supported upon a near surface comprising two level pistes service. Unfortunately, orders frictionless alas, a force be impressed upon the separated initially by steel rollers and subsequently by three steel bell bearing,. from above are that we must na.l. The flywheel comprised en electrically driven ,yroocope weighing 7 pound. system. It is impossible for the including its 0015. The weight of the support frame nod shaft wee about 3 pounds. only encourage and actively internal motions of the When the flywheel vas epii.ntng it was rareed eo tint its abaft bed an support the use of those components to affect the en aligyment 0-1 within plane i -I and then releeeed to allow it to orbit about microcomputers from the two D in the direction of arrow 8. motional condition of their main families of currently ó' common centre of mass." It is popular machines that are to be noted that anv alteration "officially approved and of motion will be in the recommended" by the college's direction of the right line along computer centre; there are no y which the force is impressed. prizes for guessing which The second statement is a currently fashionable model direct consequence of the three ..serios range this includes. P1a1. laws of motion and their Andy Thomas attendant notes. It wee observed that when on rollers:- The flywheel moved in direction b, restrained centre D. Hornsey 1 The initial experiment (circa b) There vow MOvement of the frame upon the roller, to direction A London 1970), details of which are 'irst conclusion. Considering tee Mnit oe eh.Ole, there vas e nett muse movement in direction C appended. clearly falsifies the without a reaction in direction D. Music for pleasure second statement above. I read with interest and amusement the letter from M. The reason for the lack of Secondly the apparent very properties of insulating Peacock in EW+WW audio articles in EW+WW is low quality of readership of materials in capacitors and December 1989 issue. Like him, first that there have been very EW+WW as depicted by the cables, the chemical purity and I can remember the time when few articles of real interest in letters published on audio crystalline structure of Wireless World was one of the recent years. Writers want their topics hardly inspires the conductors all directly relate to most sought after magazines by articles to be read by people confidence to advertise high sound quality, as much as, and constructors in building high who appreciate their efforts and quality components which perhaps more than, power quality amplifiers or just those who design amplifiers improve the sound quality supply ripple rejection, slew reading about how to do it. know that people with an through engineering factors rate limiting, output damping I note his phrase "The use of interest in audio engineering related to their quality of factor and other aspects of electronics to further the quality read Audio Amateur (an manufacture. Out of more than circuit design. of sound reproduction is all American magazine), Audio £10 000 spent on advertising I want to reach people with about getting sheer enjoyment Conversions (available by audio amplifier kits and the scientific integrity to test all from life." I trust that he subscription only), ET/, Hifi components in electronics and theories which claim to improve includes the enjoyment gained News and Hifi Answers because hi-fi magazines by my firm in sound quality and to use their from listening to music in the those magazines publish the last three years, none has judgement to apply those which home, as well as the pleasure material which relates directly been spent in EW+WW. work. Those who hang on to from construction. One of the to factors (engineering and When I advertise, I want the past ideas when knowledge has greatest pleasures is to gain a other) which affect quality of message to get across to people moved forward, and who seem greater appreciation and insight sound. Readers who used to who have the intelligence and to he well represented in these into a piece of music through read EW+WW are discouraged education to understand that letters pages, offer me little. improving a hi-fi system by the lack of any real audio temperature coefficient of The "subjectivists v oneself. engineering articles. resistors, the dielectric objectivists" debate is one 332 ELECTRONICS WORLD +WIRELESS WORLD April 199(1 LETTERS which digresses from the E=mc2; with or without an above 30MHz can be Population studies are not importance of applying all index o under E and/or m. established from animal easily interpreted, but from the known engineering knowledge There are four possibilities and experiments, considerations of data of Savitz7, the relative risks to the furtherance of enjoyment E0=mc2 seems to be the right human metabolism and the of childhood cancer appear to of music through hi-fi answer. "The purpose of this rather primitive dosimetry of increase at a rate of between equipment. article is to promote the electromagnetic fields. At 0.2% and 1% per nanotesla, 1 do not think that this is the rational terminology" (L.B.O.). frequencies below 30MHz, a depending upon which of place to explain some of the But not at all to call into firm biological basis rests on the several sets of data are used5. engineering factors which I question the theory of special responses of people to electric However, the confidence limits have observed to improve the relativity. currents at different on these estimates embrace sound quality of hifi equipment. J. J. Bleeker frequencies. An anchor point is negative increases with I would simply recommend that CERN the allowable leakage currents exposure, i.e. a beneficial all interested readers see that Geneva from electrical appliances at effect. The tolerable levels of excellent film "Dead poets 50-60Hz. It would be exposure implied by these society" and decide for Killing fields inconsistent to restrict allowable highly unreliable estimates lie in themselves whether the quality The recent articles in the induced currents from the range 10 to 50 nanotesla for of poetry can be measured by February issue of E V+ WW electromagnetic fields to levels members of the public and the area under the square in the question the reason for below or above these values. prolonged exposure. These graph! differences between the The 1989 NRPB guidelines, as levels of exposure will be Graham Nalty proposed guidelines for stated in the document, are exceeded in most British Borrowash restricting exposure to designed solely to protect homes. Over the past fifty years Derby electromagnetic fields in the against overheating, electric the use of electric power has / trust this letter on an audio 1986 NRPB consultative shock and radiofrequency increased twenty -fold, while the topic reinforces your view on the document' and those in the burns. incidence of childhood cancer quality of the readership - Ed. final document2 issued in 1989. There is a growing literature does not seem to have increased Germane to this question is the indicating that there may be and childhood cancer mortality Riddle of a riddle issue as to whether the long-term health risks from has decreased. It seems unlikely guidelines should have been exposure to electromagnetic therefore that these risk Could Peter Graneau, author of based on risks other than those fields and that in particular estimates are realistic. the article The Riddle of Inertia If the of electric shock, there may be risks of inducing risk is real, we are still lacking published in the January 1990 radiofrequency burns and cancer or promoting cancers the basic understanding of the issue, please explain why it is overheating of the body. induced by other agents. Those biological mechanisms, so that necessary to introduce the The scheme put forward in who believe the risk is real tend it would be impossible to concept of the force of inertia at the 1986 consultative document to favour the latter possibility; deduce equivalent risk all? was based on the concept of which requires the presence of estimates for electric fields. Classical mechanics can be "dose" represented by the some cancer inducing agent for formulated without referring to One particular source of integral over exposure time of the manifestation of the risk. uncertainty is the implication of the concept, as for example in the intensity of the The sources of the data which some of the scientific literature the standard treatments by When, as has raised these possibilities are Goldstein' and Lindsay2, which electromagnetic field. that risks might be higher at required by its statute, NRPB studies of electrical and specific do not mention force of inertia. frequencies and in consulted with the Medical electronics workers and studies windows of intensity, so that if then the concept is Research Council on the of populations exposed to merely reducing redundant, wherein lies the exposures magnetic fields in the home riddle? biological basis for its below a certain level may not proposals, it was advised that environment. necessarily David Salt reduce the risk. there was no such basis the The occupational studies Given the uncertainty Saffron Walden for about the concept of "dose". yield a weighted average the risk and Essex Other reality of the replies to the consultation relative risk to electrical and considerable uncertainties in its document strongly questioned electronic workers from all would References quantification, it be whether there was a biological forms of leukaemia of 1.2 (95% premature to specify limits 1. H. Goldstein, Classical basis for any form restriction. confidence limits 1.1-1.3)3.4 and based Mechanics, Addison-Wesley. of on the possibilities for In addition, it emerged that the from brain tumours of 1.3 (95% long-term 1959. effects on health. scheme was often not confidence limits 1.2-1.5)5. Nevertheless, there is obviously 2. R.B. Lindsay, Physical understood and when it was Because of the way these risks a case for Mechanics, Van Nostrand, avoiding unnecessary understood it was regarded as are derived they are likely to be exposures and reducing 1957. impossible to administer. overestimates due to the exposure levels where this can E=mcz Our conclusion from the confounding factor of be done easily; and a strong replies to the consultation occupational class. Taken at case for research to determine J. Ferguson (EW+WW, therefore was that the urgent their face value they imply an whether the indicated risks are December 1989, p. 1208) gives need was for a simple scheme additional average annual risk real and their underlying a mistaken interpretation of the with a firm recognisable to workers in the age range scientific cause. article by L. B. Okun in Physics biological basis, which would be 15-64 of I x10-5 from NRPB is currently carrying Today (June 1989, p. 31f). The acceptable to industry and the leukaemia and 2x 10-5 of from out and supporting research on problem under discussion is Health and Safety Executive. brain tumours. The total risk of aspects of fundamental how to write, correctly, the A reasonably firm basis for 3x 10-5 is within the range mechanisms. on the possibilities famous Einstein relation restricting the level of heating regarded as tolerable for of inducing birth defects by between mass and energy, of the body at frequencies occupational risks. exposure to magnetic fields, on ELECTRONICS WORLD+ WIRELESS WORLD April 1991) 333 LETTERS theoretical dosimetric aspects for in available study a flats near to the rising cable VDU's and X-rays and on methods for reducing pollution -free environment. rose by 82%. In fact, the exposures in industry. Support Thus, in any epidemiological proportion rose to 82% of the In the February edition, J. A. for epidemiological studies investigation, one may he total number of cases of Corbyn's letter claims to equate related to cot deaths and birth comparing the state of of the depressive illness admitted to the X-ray dosage and risk outcome is planned and for had with that of the worse. hospital from such blocks, received from six months some time NRPB, together with Your February issue which was highly significant. occupational use of a VDU. to the Department of Health, has contained a trilogy of articles on (P=0.013). that received from a typical been supporting the this subject in which reference In a third paper3, which was chest X-ray. construction of a data bank on was made to paperst-2 to which not cited, was described the However, the exposure rate the geographical distribution of I contributed and also to the investigation of all the he uses for his typical VDU is childhood cancers in England supply of electricity by pole - admissions to hospital in 1985 too large, and he ignores and Wales which will provide a mounted cables to domestic of patients suffering from fundamental differences in the basis for further studies. This premises in rural areas. In 1979 myocardial infarct (600) and physical characteristics of the scientific programme is in measurements were made of from depressive illness (359) two X-ray sources. addition to that of the CEGB the 50Hz magnetic field at 590 from addresses in the whole Taking the maximum and has been in progress for suicide addresses and 594 Metropolitan Borough of exposure rate allowed by some years. control addresses in part of the Wolverhampton. Measurements BS6204 '`Safety of data J. A. Dennis West Midlands of England. A at the addresses of these processing equipment" of 0.5 Assistant Director (Physical significant correlation was patients and their mR/hr at 5cm, the exposure Sciences) found between the suicide corresponding controls showed rate at a typical VDU to National Radiological addresses and higher magnetic no correlation between 50Hz abdomen distance of 60cm will Protection Board field. In one Shropshire village, magnetic field intensity and he approximately 0.01 mR/hr. Didcot which had a population of 2488, myocardial infarct, but a This will give a total skin dose Oxfordshire eight suicides had occurred significant correlation was after 25 weeks of 40 hrs per between January 1969 and found between the higher field week of 10 millirem, not the 30 References October 1976. This incidence of measurements and the millirem he calculated. 1. NRPB. Proposals for the health suicide was five times the Furthermore, the X-rays protection of workers and members of addresses of patients admitted emitted from a VDU have the public against the dangers of extra annual rate for Shropshire and with depressive illness. very low frequency, radiofrequency and eight times the annual rate for (P=0.033). little penetrating power and at microwave radiations: A consultative the whole area studied. Two of Certainly, the electrical least 90% will be absorbed document. Chilton, NRPB (1982). the suicides had lived at the industry is unlikely to promote within the first few centimetres 2. NRPB. Guidance as to restrictions same address where of tissue, unlike those used in a on exposures to time varying the front any truly independent chest X-ray. electromagnetic fields and the 1988 door of the house gave directly investigation. Indeed, they recommendations of the International onto the pavement bordering deserve some sympathy because It is worth noting that during Non -Ionizing Radiation Committee. the main road through the the implication of the British the same six months, the VDU NRPB Guidance on Standards GS11 village. Here the maximum findings and those operator will have received (1989). of American 50Hz magnetic field reading and about 100 millirem from natural 3. Savitz, D A, Calle, E E. 1987. Swedish scientists must be was radiation. Thus, the Leukaemia and occupational exposure 800nT and this was thought that variations in the intensity dose to electromagnetic fields: Review of to be due to a 33kV of power -frequency magnetic received from a VDU operating epidemiologic surveys. Journ. Occ. underground cable close to the fields of small magnitude may at the maximum allowed levels Med. 47-51. 29, front of the house. The be affecting the health of the is a very small fraction (less 4. M, V, 1988. Coleman, Beral A remaining six suicides had all whole than 1%) of the dose received review of epidemiological studies of population. Even if they in from other sources. the health effects of living near or lived one council estate were to concede that this was working with electricity generation and where the first 40 houses were the case, the best remedy that Cleveland Medical Physics Unit transmission equipment. Inf. Journ. supplied through overhead electrical engineers could hope Middlesbrough Epid. 17, 1-3. feeders mounted on poles and to achieve would he some Cleveland 5. NRPB to be published. the remainder by underground balancing of the risks and 6. Royal Society, 1983. Risk - that services. All but one the assessment. A study group report. The of six at great cost. Royal Society, London. suicide addresses had magnetic - F. Stephen Perry 7. Savitz, D A. Wachtal, H, Barnes, F field readings exceeding the Wolverhampton A, John, E M. Tvrdik. J G. 1988. median value for the 1184 Case -control study of childhood cancer addresses in the whole study and exposure to 60 Hz magnetic fields. area. Moreover the Amer. Journ. Epid. 128, 21-38. References measurements were found to 1. Perry F.S., Reichmanis M.. Marino decrease steadily in intensity A.A., & Becker R.O. (1981). Correction One fundamental factor makes along the line of supply. Environmental Power Frequency Quintin Davis, who wrote the Magnetic Fields it particularly difficult to In your article `Killing Fields' and Suicide. Health letter on laser Physics. 41, 267-277. vibration establish whether non -ionizing it is stated that, in a study of 2. Perry F.S. & Pearl L. (1988). Power measurement in our January radiation causes illness. the distribution of illness in Frequency Magnetic Field and Illness issue, points out a misprint at Artificial electromagnetic fields multi-storey blocks in in Multi-storey Blocks. Public Health. the end of the second are pervasive throughout the Wolverhampton2, it had been 102, 11-18. paragraph. The Decca 3. Perry F.S., Pearl L.. & developed world and if, as found that in blocks where Binns R. instrument was able to measure (1989). Power many believe, these fields do there was underfloor or storage Frequency Magnetic Field: Depressive Illness and movement down to 10-10cm, a hazard electric heating the constitute to health, proportion Myocardial Infarction. Public Health. not 10-20cm. Apologies to Mr there is no control population of cases of depression living in 103. 177-180. Davis. 334 ELECTRONICS WORLD+\WIRELESS WORLD April 1990 THE ORIGINAL SURPLUS WONDERLAND! THIS MONTH'S SPECIAL! FLOPPY DISK DRIVES ANALOG to 'DIGITAL and DIGITAL to There has never been a deal like this onel BARGAINS GALORE ! Brand spanking new & boxed monitors ANALOG CONVERTERS from NEC, normally selling al about £1401 NEW 51/4 Inch from £29.951 Brand new and boxed Amdek These are over -engineered for ultra Massive purchases of standard 5í/a' drives enables us to ADA-200 analog to digital and reliability. 9' green screen composite present prime product at Industry beating low prices' All units digital to analog converter pack- input with etched non -glare screen plus (unless stated) are removed from often brand new equipment ed full of features: Interfaces to a.:j«..i and fully switchable higMow Impedance Input and are tested,allgned and shipped to you with a 90 day most popular PC's; 2 channel -..... guarantee and & output for daisy -chaining. 3 front controls and 6 al rear. Standard operate from +5 +12vdc, are of standard size input & output by software selec- and accept the standard 34 way connector. BNC sockets. Beautiful high contrast screen and attractive case tion; Integral input/output Otters and address decoder input SHUGART SA405. BRAND NEW £29.95(B with carrying ledge. Perfect as a main or backup monitor and for pre -amp; over -level detecter, trigger signal detector dreuit; TAN DON Thf100-2A IBM compatible DS £39Á5(B quantity users' (o) expansion availability and mom. Input level £39.95 each or 5 for £185(0) TANDON TM101-4 80 Track DS £49.95(8 25mv to 50v p-p. Max. sampling frequency Is 44khz CALL FOR DISCOUNTS ON HIGHER QUANTITIES! CANON,TEC etc.DS hall height.State 40 or 801 £75.00(B and Input gain variable to TEAC FD -55-F.40-80 DS hall height. BRAND NEW £99.00(B 200 times. Designed for use with almost any personal com- puter, allowing conversion of analog signals to digital data for 31/2 INCH BRAND NEW AT £199511 COMPUTER SYSTEMS processing by the computer plus Never before seen price for a 314' drive. Standard size believed conversion back to analog the signals. TATUNG PC2000. Big brother of famous Einstein. The to be by Canon. Brand new and packaged - mint condition' 40 The 26 page manual supplied Includes data on the TPC2000 Professional 3 piece system comprises: Duality high track SS, run from +5 & +12vdc with standard power connec- correct connection to various CPU's Including the 8080, Z-80, resolution Green 12' monitor. Sculptured 92 key keyboard and tor Only £19.95 or 2 for í 4.50(8) 6800, 6502 and 6809 families plus data and schematics for user plinth unit containing Z80A CPU and all control circuits. PLUS 2 8 modification of I/O filter cut -oft frequencies. Complete with 50 Integral TEAC 5.25 80 track double sided disk drives. Generous CHOOSE YOUR INCH! Shugart 800/801 refurbished way ribboncable and edge connector to go to the computer and other features Include dual 8' IBM formal disk drive support. SS & tested £125.00E Shugart 851 double refurbished power cable. All for a fraction of the regular price' £49.95 (C) Serial and parallel outputs, full expansion port. 64E ram and sided 8 tested £195.00(E) Mitsubishi kí2894ó3 sided ready to run software. Supplied complete with CP/M, Wordstar double switchable hard or soft sectors- - and Basic. Brand new and covered by our famous 90 day BRAND NEW £250.00(E) POWER SUPPLIES guarantee and backup. Normal price of this unit is over £14001 SPECIAL OFFERS!! A I PSUs 220.240vac Input and are BRAND NEW unless stated. Many types ranging from 3v to 1Okv always In stock Our price .... only ...... £299 (E) Dual 8' drives with 2 megabyte capacity housed In a smart case with built In power supply' Only £499.00 (F) Fine OP-8619 20 watts switch mode. +5v @ 2a. +12v @ la, SPECIAL PURCHASE Ideal as exterior drives' -12v @ 0.1a. 5' x 3' o 1-1/2'. £15.95(B) End of line purchase scoop! Brand new NEC D2246 8' 85 Astec AC -8151 40 watts. Switch mode. +5v @ 2.5a. +12v @ V22 1200 baud modems megabyte of hard disk storagel Full CPU control and Industry 2a. -12v @ 0.1a. 6-1/4' x 4' x 1-3/4'. £19.95(B) standard SMD interlace. Ultra hi speed transfer and access time Greendale 19ABOE 60 watts switch mode.+5v @ We got a tremendous buy on further stocks of this popular 6a,l12v @ leaves the good old ST506 Interlace standing. In mint condition 1a -415v @ RFE and Master Systems 2/12 microprocessor controlled V22 full duplex la. fullytesied.11 x 20 x5.5cros. £24.95(C) and comes complete with manual. Only £399(E) Convey AC130. 130 watt h -grade 1200 baud modem - we can now bring them to you at hail leaf VDE spec.Svatch mode.+5v advertised price! Fully BT approved unit, provides standard MAINS SUPPRESSORS & FILTERS @ 15a, -5v @ la,i12v @ 6a.27 x 12.5 x 6.5cros £49.95(C) V22 high speed data Comm, which at 120 cps, can save your Boahert 13090. Switch mode.ldeal for drives & system. +sv@ The 'Milan' from Crotan is a British made high current mains phone till and connect time by a staggering 75%1 Ultra slim 45 6a, +12v @ 2.5a, -12v @ 0.5a, -5v @ 0.5a. í29.95(B) spike suppressor and RF filter In capable mm high. Full featured with LED status indicators and remote one, of handling up Fsmell 06/40A Switch mode. 5v @ 40a.Encased £95.00(C) to 10 ampsl The attractive case has 13 error diagnostics. Sync or Async use; speech or data switching; an Integral amp socket Farrell G24/5S. As above but 24v @ 5a. £65.00(C) built In 240v mains supply and 2 wire connection to BT. Units for your equipment plug and a flying lead terminates In a quality are In used but good condition. Fully tested prior despatch. with plug (to BS 1363A standard) to go to the mains socket. There IBM KEYBOARD DEAL Is an Internal fuse plus one in the plug. Two LED Indicators, data and a full 90 day guarantee. What more can you ask for - one A replacement or bac..up keyboaró, sedchable for if t PC, and at this pricell ONLY £69 ID) for power on and the other lights If the internal fuse falls. Dims:6' PC -XT or PC -AT. LED's for Caps,Scroll & Num Locks. Standard x 3' o 2'. Brand new. Distributor's price - £65.001 Continental 85 keyboard layout. Made by NCR for the English 8 US markets. MONITORS plug version Fllt-C. Either only £15.95 each or 2 for £79.95 (B) Absolutely standard. Brand new 8 boxed with manual and key COLOUR MONITORS Belling -Lee type L2127 mains RFI filters rated at 250 volts 3 template for user slogans on the function keys. Attractive Deco 16- 80 series budge) range colour monitors. Features amps maximum. Comes complete with a built In mains cable belge,grey and cream finish, with the usual retractable legs underneath. A generous length Include PIL tube, housed In a beautiful teak style case and (English coring), and a three pin miniature non -reversible sock- of curly cord, terminating in the S pin guaranteed 80 column resolution, features which are only nor- et and a mating plug, to go to the equipment. Ideal for those standard DIN plug. A beautiful clean piece of manufac- turers surplus. What a deal' mally seen on colour monitors costing 3 times our price' It is who are bugged by RF Interference. Very compact. Dims 3-1/8' BRAND NEW AND BOXED ONLY £49 ( B ) absolutely ready to connect to a host of computer or video x 2.5"x 1.5' £3.95 each or 3 for £10 (A) outputs. Manufacturers fully tested surplus, sold In little or hardly THE AMAZING TELEBOX! used condition with 90 day full RTB guarantee. Deccs 80 COOLING FANS COMPO 75 ohm composite video Input with Integral audio amp Please specify 110 or 240 volts for AC fans. Converts your colour monitor Into a 8 speaker. Ideal for use with video recorder or our Teiebox ST, DUALITY COLOUR TVII 3 Inch AC. 112' thick E 8.50(8) or any other audio visual use. Only £99.00 (E) 314 Inch AC ETRI sllmline.Only 1' thick. E 9.95(B) TV SOUND HI-DEFINITION COLOUR MONITORS 4 Inch AC 110/240v 112' thick. £10.95(B d VIDEO Brand new Centronic 14' monitor for IBM PC and compatibles 4 Inch AC 114" thick £ 9.95(B 10 Inch Round.314 thick. Rotron 110v TUNER! at a lower than ever price' Completely CGA equivalent. Hi -res £10.95(B) 62 mm DC V thick.No.812 for new high quality, 7 Mitsubushi 0.42 dot pitch giving 669 x 507 pixels. Big 28 Mhz 6/12v.814 24v. £15.95(A) Brand fully cased. channel UHF PAL TV tune bandwidth. A super monitor in attractive style moulded case.Full 92 mm DC 12v. 18 mm thick. £14.95(A) system. Unit simply connects lo your TV aerial socket and colour 4 Inch DC 12v. 12w 114' thick £1250(B) video monitor turning same into a fabulous colour worry 90 day guarantee. Only £149 (E) TV. Dont 4 Inch DC 24v 8w. 1- thick. £14.50(B) If your monitor does nt have sound, the TELEBOX even has an 20",22" and 26" AV SPECIALS Integral audio amp for driving a speaker plus an auxiliary output Superbly made UK manufacture. Pit all solid stale colour RECHARGEABLE BATTERIES for Headphones or Hi Fl system etc. Many other features: LED monitors, complete with composite video 8 sound inputs. Attrac- LEAD ACID Status indicator, Smart moulded case, Mains powered. Built to live teak style case. Perfect for Schools,Shops,Disco, Clubs. Maintenance free sealed long life. Type A300. BS safety specs. Many other uses for TV sound or video etc. In EXCELLENT little used condition with full 90 day guarantee. Supplied BRAND NEW with full 1 year guarantee. 12 volts 12 volts 3 amp/hours £13.95)A 20"....£155 22"....£170 26"....£185 (F) 6 volts 6 volts3 amp ours £ 9.95(A Teiebox ST for composite video input monitors £29.9503) 12 vote Centre lapped 1.8 amp hours £ 5.95(A) Telebox 5n. as ST but with Integral speaker ...... £34.95(8 MONOCHROME MONITORS Telebox RGB for analogue RGB monitors £65.95(9) Very high resolution, fully cased 14- green or amber screen 12 vote 12 volts 24 amp hours. A200. RFE. £29.00(B) monitor with non glare screen and swivel/tilt base. The very SPECIAL OFFER! NOT suitable for IBM or Clone type colour monitors. latest technology al the very lowest price' Fully compatible and 100 ampihours at 6 volt! Brand new Chloride Powersate PAL overseas version please call. SECAM not available. plug compatible with all IBM PCs and clones fined with a high 3VB11. Leakproof with additional snap -on security lid. Perfect errs Hercules or equivalent cardl Enables superb graphics and for uninterruplable power supplies, portable power source, BRAND NEW PRINTERS resolution, all at a give away price. Has many extra features caravans etc. Normally costs £801 £39 (E) Epson MX -80 F/T One of the most popular printers around) including aux +5 & 12v DC outputs to power at least 2 disk drives, NICKEL CADMIUM Bi-directional printing with lull logic seeking. 9 x 9 dot matrix for if your PC power supply is getting hotl Supplied BRAND NEW Quality 12v 4ah cell pack. Originally made for the Technicololor eniarged,bold,cordensed etc. Standard parallel interlace. Brand and boxed. State whether amber or green screen required. video company. Contains 10 GE lop quality D nicad cells in a label removed from front. Handles tractor,fanfold and individual Amber S79 Green .£69 (E) smart robust case with a DC output connector. Ideal for portable paper. OK with IBM PC and most others. A tremendous buy' Wang green screen 12' chassis monitor with composite Video equipment. Brand new. £19.95(B) FOR AUMTED11MEONLY £129.00 (E) Input. Adjustable for tilt. Requires 12 vdc. Brand new and boxed Ex -equipment NICAD cells by GE. Removed from equipment DED DP621 miniature ball point pen printer plotter mecharnism in perfect condition. Only £39 each or 2 for £75 (F) and in good, used condition: D size bah 4 for £5(B) with hill 40 characters per line. Complete with data sheet which Motorola M1000-100 5' black 8 white compact chassis measur- F size 7ah 6 for £8(B includes dreuit diagrams for simple driver electronics £49(B) ing only 11.6H x 12W x 22D. Ideal for CCTV or computer SPECIAL INTEREST Centronics 150 serles Always known for their rellabilty In applications. Accepts standard composite or Individual H & V continuous use - real workhorses in any environment. Fast 150 syncs. Needs 12vdc at only 0.8a. Some units may have minor Racal-Rrdac real time colour drafting PCB layout system. In- cps with 4 fonts and choice of Interlaces. screen blemishes. Fully tested with 30 day guarantee and full cludes furniture and huge monitor.Complete ready to gol £3950 150-SN up to 9.5' paper £155.00(E) data. £29.00(C) DEC VAX11/750 Inc. 2 Meg Ram DZ and full documentation, In 150 -SW up to 14.5' paper £199.00E) Fully cased as above In attractive moulded desk standing brand new condition' £3900 Specify whether serial or parallel required. swivel. Dim 12 x 14.5 x 26cm. £39.00(C) Caleomp 1036 large drum 3 pen plotter £ 650 CALL FOR THE MANY OTHERS IN STOCK loge JVC 751 ultra compact chassis monitor for 12vdc 0.7a. Dim 11 Thurlbyr LA 160A analyser £ 275 INCLUDING DAISY WHEELS. x 14 x 18cm. Simple DIY data Induded to convert to composite 1.5kw 115v 60hz power source £ 950 real time freq.res.analyser. £3000 video input .Full data. BRAND NEW £65.00(B) Wayne Kerr RA200 audio VISIT our brlop - TeCnniCal neip always on nana VG Electronics 1033 Teletext Bridge £3750 20- Black & white monitors by Aztek, Cotton & National. All plusrcnany un -advertised spedals. You can buy a solid state, fully cased monitors Ideal for all types of AV or CCTV Tektronics R140 NTSC TV test signal standard. £ 875 applications. Standard composite video inputs with integral Sony KTX 1000 Videotex system - brand new £ 790 colour television for as little as £29! Come and audio amp and speaker. Sold in good used condition - fully tested DEC LS11/02 CPU board £ 150 Join the gang at 215 Whitehorse Lanel with 90 day guarantee. £85.00(F) ADDS 2020 VDU terminals - brand new £ 225 LARGE QUANTITIES OF OSCILLOSCOPES AND TEST GEAR ALWAYS AVAILABLE - CALL NOWT MAIL ORDER L OFFICES LONDON SHOP 1 TEL 0 The OrIglIE ALL ENQUIRIES « Pres dial -up database! Open Mon -Fri 9.00-5.30 100's of bargains! =aaPLAY Mon-Sat9-5.30 1000's of llems+Info On Line Dept WW, 32 Blggln Way. Open 01-679-4414 215 Whitehorse Lane, 300 bd 01-679-1888, '..._ Upper Norwood. Fax- 01-679-1927 London SE19 3XF. South Norwood, 1200/75 bd 01.679-6183, London, SE25 6R8. 1200/1200 bd 01-679.876° Telex- 894502 Ax prices for UK Mainland UK customers add 15% VAT to TOTAL order amoral Minimum order CIO PO orders tram Governnert,Universiiss,Schoals 8 Local Authoreres -Electronics- weicomsminimum account order £25. Cantoge charges (A) -C2 00 (B)-44.50 (q -íB.50. (0).00 00 (E) -CT 200 (F)d17 00 (Gj.Cali Ax goods supplied sumlrrd to ma standard Condbons of Salo and arias otherwise d.tedguararseed tor 90 days All guarantees on a Mum to base basis.We reserve the right to change pricesa specrfcabons wuerut prior rota. Orders accepted .thjed to stock Quotations wimngry Owen for higher guar/ Mies than those stated Bulk surplus always requred for cash. CIRCLE NO. 139 ON REPLY CARD April 1991) ELEC'T'RONICS WORLD+ WIRELESS WORLD 335 NEW PRODUCTS CLASSIFIED 64K -bit s -rams. Byte -wide s -ram, transform (DFT) applications. It can a front panel led display drive and FCB61C65, is an 8K device which perform convolutiDn and correlation, keyboard scanning. Celdis 0734 features power consumption of 11tA, as well as many filtering functions 585171. ACTIVE both on the 5V standby and in the The input data word length is 16 -bit battery back-up mode Normal and low and coefficients can be selected as 4, Maths processor. MicroCall Solutions power versions are also available and 8. 12 or 16 -bit wide. Two's has available the Cynx fully 80387 A -to -D and D -to -A speeds range from 55ns to 7Ons. It complement numerical formats are compatible numerics processor. operates from a single 5V supply: used for data and coefficients. It can Called the Fastmath, the device offers converters inputs and outputs are TTL and c-mos throughput data up to 15MHz Hawke up to ten times the performance of compatible. Two chip -enable pins are Components Distribution, 01-979 standard processors. very low power 8 A/D -bit converters. Two high- provided. Philips Components Ltd, 7799 dissipation, and 100% software -compatible and speed microprocessor 01-580 6633 pin compatibility with the standard 8 -bit analogue to -digital converters LD/MF dialler. The AMS S2570 is an 80387 PC maths coprocessor. operate with a +5V a single supply, integrated c-mos device for push- MicroCall Solutions, 0844 261500. +1.23V external voltage reference. Microprocessors button telephones, which converts and accept input voltages ranging and data from the keyboard in either from OV to 2V ref. Both c-mos devices controllers correctly timed line disconnects ILD) Optical devices use successive -approximation or generates tone pairs for multi - technique to achieve 15mW Risc microprocessors. Samples of frequency signalling in (MF) Optocouplers. The 20 000 3A series dissipation and operate down to Sus to the 33MHz Am29000 (29K), AMD's accordance CCITT of optocoupler, compact rail -mounting conversion time. The AD7575 and 32 -bit risc recommendations Mode microprocessor are switching units, 100mm x 12.7mm wide, have AD7576 offer a data access time of form to available. The 33MHz 29K brings 22 LD MF and back is the Entrelec universal mounting foot 100ns and easily interface to all 8 -bit mips performance to applications implemented via the keyboard. Austria microprocessors to fit DIN 1, DIN 3 and Cenelec rails. Kudos Theme Ltd. such as networking control and high - Mikro let Systeme Ltd, 0793 537852. Input voltages may be 24V. 48V, 110V 0734 351010. end graphics, which require high AC/DC and 220V AC, whilst output data TV controller. Designated the speed throughput capability. The voltages may be either 3-60NDC or 33MHz 29K is pin compatible with Z86C27. the Zilog device provides the 24-280V AC. Entrelec (UK) Ltd, 0273 Linear integrated circuits AMD's current 29K family which usual picture audio controls and also 570730. includes 16, 20 and 25MHz versions offers a greater choice of screen Isolation amp. Burr -Brown's of the risc microprocessor Advanced display information formats than Optocouplers. A 11 kV (peak) IS0212P is a two -port isolation Micro Devices 0483 740440. similar devices. Using a Z8 breakdown isolation is provided by the with 12 amplifier -bit accuracy and an microcontroller, the DTC is more Isocom IS1000 range. The coupler internal isolated DC -DC converter, all Transverse Hawke powerful and to than filter. easier program comprises a coupled IR pair with a powered a from single +15V supply Components now offers the Inmos similar 4 -bit products and offers a 4mm internal gap to give the high Its plastic SIL package has a 2.2 x IMSA100, a high-speed 2 for 32 -stage -colour on -screen bar graph visual isolation figure. Housed in a 4 -pin 0.3in footprint and is 0.43in high, digital transverse filter with a flexible displays of other inputs leg volume plastic package. it has an Io of 100nA permitting -to card -card spacings of architecture that lets it be used as a and contrast). Displays can be faded max and BVtro of 30V min. Milgray 0.5in without interference. mechanical building block in many discrete Fourier out or in. Other on -chip capabilities are Distribution Ltd. 0788 543550. Rated isolation voltage is 750VRMS. The external power capability is +5mA (at 8V), and power dissipation is 75mW The internal op -amp can provide gains from 1 to 100 using a few external components. Burr -Brown PASSIVE International Ltd. 44 0923 33837. Microwave terminations. A series of moisture resistance eliminates the Ceramic trimmer. The Tusonix VARI- KDI topless and coverless high -power need for special mDisture protection. Thin Audio op -amp. The Linear series 513 ultra -miniature film terminations and resistors is The devices handle up to 20W trimmer has a 100V Technology Lt1115 op -amp features capacitors DC impervious to moisture penetration. average and 2kW peak power. working voltage range and is 0.196 in 0.9nV ,Hz noise at 1 kHz and less than The open construction is suitable for Operating frequency range is from DC x 0.080in to be the 120nV/, Hz noise over the 20 to 20kHz claimed smallest use in microwave stripline and to 3GHz Anglia Microwaves Ltd. 0277 of its type available. The audio spectrum. Referred to the currently 513 microstrip circuits, where the 630000. is available in capacitance ranges from professional audio standard. wideband 1 5pF up to 7 40pF STC Mercator. noise exhibited by the LT1115 is One of the accelerometers from Entran's EGCS-2400 range. - - 0493 844911. -136dB. Driving a typical 600ohm load, the total harmonic distortion is less - Miniature electrolytic than 0.002% at 10kHz; typical CCIF capacitors. Two series of Rubicon miniature intermodulation distortion is less than r` aluminium electrolytic capacitors 0.0002%. Micro Call Ltd. 0844 ,' ,y exhibit high levels 261939. r of stability and reliability at elevated temperature up to 105°C. The PS2 series is intended Monolithic amp. Raytheon has for smoothing circuit applications in announced the RC4277, a monolithic switching regulated power supplies bipolar dual op which -amp comprises and other high -frequency equipment. two amplifiers in an lead eight It has enhanced temperature. package. It is claimed to have the frequency and high -temperature load lowest input offset voltage available in (2000 hours at 105`C) characteristics a dual op -amp, maximum only 30µV and reduced high -frequency with offset drift of 0.51.i.V/C impedance. Offered in seven voltage maximum. Open -loop gain is 2 000 ratings of 6.23V to 63V, the PS2 000 minimum into a 2k0 load, while series covers a capacitance range of input bias current is +3nA maximum 22 to 22001F. The MHA series is in and power a consumption low seven voltage ratings from 10 to 100V 100mW maximum (both channels). and covers a capacitance range of CMRR and PSRR is 120dB minimum. 0.47 to 6800µF. HB Electronics, 0204 Raytheon, 0494 450327. 386361. Bidirectional transient suppressor. Memory chips Silicon transient suppressor 60KS200C is a bidirectional device for Programmable fifo. The Am4601 use in shipboard equipment and other c-mos first -in first -out buffer memory power servicing equipment where circuit features programmable status large voltage transients endanger flags and is compatible with the voltage sensitive equipment. Features Am72OX-series filo family. The of the 60KS200C include peak pulse Am4601 is 512 words deep. Each power dissipation of 90000W, a 200V word is nine bits wide. The circuit has bidirectional capability and the ability two fixed flags-full and empty-and to exceed MIL -STD -1399 two programmable flags. Both 25ns % requirements. Steady state power access -time versions of the part are f dissipation is 10W. Weighing available. approximately 50g, the new device 336 ELECTRONICS WORLD+WIRELESS WORLD April 1990 TEST EQUIPMENT AND PC CARDS When you need PRIVATE LIQUIDATION SALE TEST EQUIPMENT: Hewlett-Packard 16500A Logic Analyser System, COMPONENTS including 16531A acquisition card, 16530A oscilloscope timing card and 16510A 80 -channel (C.W.O. Post Free U.K.) state timing card. Includes full documentation. Stag PP39 MOS Programmer, with 39M100 Eprom & EEprom Module. Tektronix Oscilloscope, 350 MHz, type 2465A, with manual. PC ACCESSORIES: Accent ASYNC-4 RS232C Stabilised Interface Cards, 4 port. Addonics M10-232/242 Multi Seria Card (PC -AT) with 4 RS232C serial interface ports. Chiptech Cheater Cards, (to simulate 80286 PC -AT). 3COM Ethernet Network File Server Boards, also compatible with Sun PC-NFS and Olivetti Multi - Ian, with PC-NFS s/w and documentation. Excalibur DAS-429PC PC/ARINC 429 Interface Card. Excalibur Rambo Ram Disc Cards, (256k CMOS RAM). PC SOFTWARE PACKAGES: You need Microsoft "C" Compiler and Assembler for PCs, with manuals. LL Oracle Developers kit, PC s/w package, with tLECrROA manuals. tor FREE CATALOGUE write phone or call For further information, pricing ELECTROVALUE LTD., FREEPOST. 28. St Judos Road. EngleflHd Green, Egaam, Sunay TWPO 85A (Mt stamp rapv'red) Phone: 0764 433603 F.,: 0784 435216 T.le,: 264475 and availability: Shopmocr,. 4p 5-A7,Sat rOpm! NORTHERN BRANCH 680 Burn.9. Lan., M.nch.st.r M19 1NA Telephone: Hindhead (042873) 7202 Phone: 061-432 4945 F.,: 061.432 4127 CIRCLE NO. 140 ON REPLY CARD CIRCLE NO. 141 ON REPLY CARD SPECIAL Prices are correct al time of press bu may fluctuate VALVES DUALITY Please phone for form quotation V A T nc uded A1065 2.40 EF80 1.-- 0.65 PCI 06 Is 0.80 190(11 9.50 6CL6 2.75 1206' 3.50 A2293 7.00 EF83 3.90 PCL8058:, 0.95" tA3 1.90 6CW4 7.40 12416 1.95 Toroidal A2500 12.75 EF85 0.90 P0500,510 5.60 IL. 0.95 6CX8 4.60 12A17 1.25 4118 1.40 1.45 PF1200 1.10 1615 1.20 6CY5 1.15 12AU7 0.95 EF86 1.10 411003 145 1.60 PFL200' 2.80 1S4 1.20 606 2.50 '2A07 EF89 '2866 3.50 ARP35 I 50 EF91 1.60 PL36 160 1S5 0.85 6F6G 2.90 12E3E6 2.40 AIP4 090 EF92 2.15 P1-81 1.30 114 0.75 6F6GB 2.90 Transformers 2.80 12B117A 4.80 6.90 PL82 0.70 1U4 1.25 6F7 81211 EF95 1.40 12E1 19.95 PL83 0. 3.80 6F8G 1.75 0131 240 EF96 0.65 2X20 t212./501 0.55 range P 4 0.9070 304 1.30 6F 12 1.60 As manufacturers we are able to offer a EF 183^ 0.7504 12K7GT 1.15 D4F96UAF70 7.351.75 125 3472 3.40 6F14 1,15 - EF 184 0.75 120701K8GT 1.25 of quality toroidal and laminated transformers 122 32.80 ^ PL508 2.00 3B28 17.50 6F 15 JAp DE EF812 0.75 12SC7 1.15 DF92 0.95 PL509 5.65 3828- 19.50 6F17 3,10 at highly competitive prices. 1.85 12SH7 1.25 DF96 1.15 EFL200 -- 505. 306 1.15 6F23 0.75 0.85 P1516 125117 1.25 01176 1.15 E1490 0L802 6.60 3E29 21.85 6F24 1.15 126J7 1.40 DL92 1.70 EL32 0.85 pyBO 0.90 3S4 1.70 6F33 10.50 12SK7 1.45 Toroidal Price List 0186187 0.65 EL34 325 P181 0.75 4832 35.00 67018 18.80 12S0701 2.20 01802 0.70Sli P181 800 ^ 0.85 5P4GY 4.85 6G48 0.65 1214 0.70 1.95 61-82 0.70 15182 0.75 51140 1.85 601384 0.90 1303 2.80 Exclude VAT 8. carriage E92CC y Quantity prices EI8OCC 9.80 E184 ( 4.95 P188 0.60 5V4G 1.90 6116 1.60 1306 0.90 EL86 1.4> PY5OCA 2.10 2.20 6.14 1.95 19405 1.85 VA Mall Order 1.5 6 16 . 25 50 100 E1148 0.75 - 51307 1.75 4.85 1903 11.50 15 9.72 8.75 6.42 6.08 5.49 5.10 0.86 EA76 1.60 EL90 0000310 5.95 5Z3 614WA 3.10 6834 1.15 EL91 6.511 00V0310 7.50 5Z4G 2.20 6.15 2.30 1906 10.35 20 10.3 9.27 6.80 6.44 5.82 5.41 5.15 19H5 EB91 0.60 EL95 1,80 00V0320A 2750 5Z401 2.20 61507 1.80 38.00 50 10.96 9.86 7.23 6.85 6.19 5.75 5.48 0.80 EBC33 2.20 0080C40.4 28.50 6/30L2 0.80 6J6 2.20 2001 7.44 7.05 6.37 5.92 5.64 EL504 2.30 1.30 60 11.28 10.15 EBC90 1.20 Ú0V0640' 46.00 6487 1.85 616W 2.80 20E1 6.24 5.94 EL519 7.70 80 11.88 10.69 7.64 7.42 6.71 EBC91 1.15 EL821 750 0V03'12 7.40 6AC7 1.80 6JE6C 9.15 100 12.88 11.59 8.50 8.05 7.28 6.76 6.44 3.20 6405 0.60 6JS6C 9.15 L6GT EBF80 0.75 EL822 11.50 SP61 85420 1.40 120 13.28 11.95 8.76 8.30 7.50 6.97 6.64 47.50 6A65 1.90 61116 6.35 EBF89 0.801121ELL8OSE 4.50 858502 1.40 7.81 7.44 2.20 150 1488 13.39 9.82 9.30 8.41 EC52 0.65 EM80 1.50 1122 45.00 64K6 2.85 6K7 8522' 2.55 7.73 0.75 601-5 0.60 6606 12.90 160 15.46 13.91 10.20 9.66 8.73 8.12 EC91 5.20 EM87 285 Ú08030 8728 61.90 EC92 9.55 UBFeu 0.95 6AL5W 1.50 6L6 7.10 225 18.22 16.40 12.03 11.39 10.29 9.57 9.11 E151 0.93 7 `_ 3.45 1.25 UBFB+ 0.95 6AM5 6.50 61-600 9.60 300 20.18 18.16 13.32 12.61 11.40 10.59 10.09 ECC81 1.10 .E 4.30 E181 0.85 1.60 400 26.52 23.87 17.50 16.57 14.98 13.92 13.26 ECC82 0.95 - O.T UCC84 64M6 6L6G7.y90 811A 13.50 ECC83 1.10 E08687 Ú00f15 0.70 64N82 3.80 WM 0:70 8130 32.00 500 26.88 24.19 17.74 16.80 15.19 14.11 13.44 E188 0.65 ECC84 060 uCCCHel 4.60 6405 1.75 61-020 0.70 813 28.50 19.84 18.79 16.98 15.78 15.03 625 30.06 27.05 ECC85 0.75 E7,p0 0.75. 6405W 2.90 6L06 9.15 813' 44.00 1921 750 38.42 34.58 25.36 24.01 21.71 20.17 ECC88 1.25 0.80 UCLA 6406 1.15 607G 1.50 8298 16.00 800 43.96 39.56 29.01 27.48 24.84 23.08 21.98 ECC189 1.20 4 +- ÚF41 1.85 60570 4.95 6507 1.80 8290' 24.00 1000 53.54 48.19 35.34 33.46 30.25 28.11 26.77 ECC804 0.65 GN4 6.30 UF80 1.60 6406 0.90 6SG7 1.80 866E 14.95 UF85 1.45 1200 59.08 53.17 38.99 36.92 33.38 31.02 2954 ECF80 1.25 G1501 1.50 6AX4GT 1.30 6SJ7 2.50 931A 18.95 UL84 1.50 1.85 45.42 43.01 38.88 36.13 34.41 ECF82 1.25 GZ32 2.60 6.4%SGT 1.10 6SK7 931A' 26.80 1500 68.82 61.94 1'60 651-707 4.35 44.16 42.06 ECFeo2 1.80 0233 4.20 U, ...MSC., 6806 1.75 154 1.10 2000 84.12 75.71 55.52 52.58 4753 UM8O' 2.30 6SN7GT 4.35 54.98 E011Á2 1.65 GZ34 2.60 6BÁ6' 2.20 955 1.10 2500 109.96 98.96 72.57 68.72 62.13 57.73 ÚM84 1.10 6S07 0.95 ECH81 1.25 G234' 6.00 U182 1.10 68E6 1.75 956 1.20 3.95 6BE6' 2.20 65617 4.60 These are with two equal secondarle with 8 colour coded fly leads. ECH84 0.90 0Z37 Ub8E 0.85 5.75 prices for single primary 606 1.50 '606"'"-o'7 ECL80 0.75 6177 16. 10 VR1Qy30 2.75 6806G 2.65 f 1.95 ML4 1.75 4 ECL82 0.95 3.20 VR15D/30 2.75 68J6 b 6080 7.30 Available from stock in the following voltages: 6-0-6, 9-0-9, 12-0-12, 15-0-15, 0.95 ML6 3.20 X66 61307A 3.95 6X5GT 0.75 earls 4.95 6136 2.80 25-0-25, 30-0-30, 35-0-35, 40-0-40, 45-0-45, 50-0-50, 110, 220, 240. Efja& -.120, M012901 29.50 0.75 66617 4.80 6160 2.80 18-0.18, 22-0-22, 2749 61468 12.70 Primary 240 volt. EF9 2.80 N78 9.90 2759 19.90 6BW6 6.10 6Z4 1.75 EF22 3.90 OB2 1.70 28005J 3.45 6BW7 1.50 724 1.90 9001 1.40 EF37A 2.45 PCL82 - 0.95 2801J 3.75 6C4 1.20 906 2.15 9002 6.50 EF39 1.40 PCL84 _ 0.85 280311 21.15 6C116 7.50 11E2 19.50 9003 8.50 AIR VALVES AND TRANSISTORS NEW HEADSETS with built IOmicrophone5 CAROL HP -339M at £10.00 FIELD TELEPHONE, CABLE TYPE 010 Headphone one 4.16 ohms Microphone imp al 600 ohms LINK FIELD TELEPHONES TYPE J. Tropical mmetal cases E480 at 015.00 10 -line MAGNETO SWITCH -BOARD. Can work with Headphone Imp 4-16 ohms Microphone Imp at 200 every type of magneto telephones ohms Transformers Surplus vIDICON P8211 and others al £18 00. Air Link POSTAGe AND PACKING CHARGES, C1-03 75p. 03-05 95p, C5 -f10 C1 15, C10-15 C1 40.015-20 C2 00. over C20 but below 2kg C2 65 over 2ng at Cost Unit 6, The Maltings, Station Road, Sawbridgeworth, Herts. Tel: 0279 724425 Fax: 0279 724379 COLOMOR (ELECTRONICS LTD.) 170 Goldhawk Rd, London W12 Tel: 01-743 0899 Fax: 01-745 3934. Open Monday to Friday 9 a.m. - 5.30 p.m. CIRCLE NO. 142 ON REPLY CARD CIRCLE NO. 143 ON REPLY CARD 337 April 1990 ELECTRONICS WORLD + WIRELESS WORLD NEW PRODUCTS CLASSIFIED operates in the range of -65 to contains a wide range of data +150°C. Hunter Electronic acquisition, instrumentation and Components. 0628 75911. power supply products. Over 100 new products include a range of boxed Bridge rectifier. A of series miniature products; analogue signal conditioning 1A single-phase rectifier bridges with modules; a PC diagnostic system; ratings from 100 to is known 800V as 1Frorbm,mEált901con and digital panel meters. Amplicon the 1B series and uses 6 -pin dil Liveline, 0273 570220. packages with pins on 0.2 x 0.3in centres to fit with the pitch 0.1in PCB Linear application note. An design matrix. The devices are end P, application note on using switching stackable in standard IC sockets. regulators in power supply and other Surge capacity is 30A and _ kinds of circuit design is available free temperature range - -40°C to +150°C. 91B from Linear Technology Rectifier IUK) Ltd. The International Co. 0883 applications note contains 713215. schematics for more than 80 designs of battery - eeó based switching power supplies. The Toroidal transformers. The first r eer application note is entitled "AN30: products from the Swedish company le Switching Regulator Circuit Lintron's new UK factory are toroidal e Collection". Linear Technology 0932 transformers ranging in size from 5VA 765688. to 10000VA. The design ensures low magnetic field disturbance, combined with low weight and profile. Lintron Power supplies Electronics Ltd, 0670 717595. CS 1041 portable diagnostic instrument for process control, from Status Instruments. EHT Metal foil resistor networks. DC -to -DC converter. Direct - Hermetically -sealed, metal plated shells and units are autoranging; trigger lock; CRT current output ranging from 20V to ceramic DIP 10kV versions of the Alpha high -precision available for use with both flat and readout; frequency counter; auto is provided by the Model 2590 DC -to -DC converter module. metal -film resistor networks in 8, 14 round cable. Junction shells with trigger level and selectable signal Load current rating is 1mA and 18 -pin types are now available. cable entry at 50° and 180° are also output The V-1085 provides four and, at this level, the module with a wide choice available. The range covers the full independent 100MHz channels, each draws around 700mA of configuration, from the input including resistor arrays, range of commonly used D-type possessing position control, +3% supply of between 19V independently connector sizes, including 9. 15, 25 accuracy; selectable input coupling and 30V; quiescent current is about connected elements. 120mA. voltage dividers and ladder networks. and 37 -way Jermyn Distribution, (AC and DC); and sensitivity (0 1V div Increasing output current from zero to maximum The TCR tracking of or 0732 450144. and 0 5V div). All the oscilloscopes causes output ±1.±2 voltage vary ±3ppm °C. Best tolerance is possess trigger lock for the to by 0.3% and for a 22V ±0.02% to absolute and ±0.01% matching. observation of pulse trains, enabling 30V input swing, output voltage varies by 0.1%. Flashover and Resistance value range is from 511 to Hardware the sum of the holdoff and sweep overload protection is provided. 60k1). Rhopoint components, 0883 time to be held constant, a push 717988 Wire strippers. Hand wire and tubing button automatically selects the Brandenburg, 0483 756066. cutter, Model AB10, is a hand -crank optimum sweep time (with approx 1.6 DC/DC unit which will cut equipment wire of to 4 cycles of signal displayed) Hitachi converters. BP50000 is a up to 14AWG into lengths between Denshi (UK) Ltd. 01-202 4311. series of DC -DC converters which Connectors and cabling fixed 2.54mm and 216mm, and sleeving deliver a output voltage from a Clip -on Hall wide range of input voltages (8-30V). D A range and tubing of up to 6.35mm diameter -effect meter. The HEME connectors. of D -type Housed and epoxy encapsulated in combines into lengths between 2.54mm and 600 AC DC clip -meter, offering a 1% connectors the shielding compact 7 or 9 pin single -in -line properties of metallised connectors 51 mm. The unit is being offered with accuracy, employing the Hall -effect to enable fast measurement packages, the series is suitable for with the low cost and light weight of a free bench -top free -running of volts, de Rush Wire amps and resistance without the need supplementary on -board voltage ABS housings. The range is based on -reeler. Strippers, 0264 51347. for direct contact into a circuit. The regulators. telecom equipment and PC Zentro Elektrik meter will handle conductor sizes up expansion boards. Rohm Electronics electronic load (UK) Ltd. 0908 271311. from Gresham Powerdyne. This to 30mm. STC Instrument Services. one sinks 500W. Instrumentation 0279 641641. Programmers Generators. There are 21 models, Circuit analyser. The National covering the 10MHz to 18GHz Microsystems Model 2600 continuity PC -based eprom programmers. A frequency range analyser is a high-speed low-cost in the NC7000 series range of PC -based eprom of programmable, system which combines a high testing broadband noise programmers offers the PC user generating instruments. capability with ease of use. Up to Each versatile. easy to use at 1024 test points can be products low instrument contains a broadband cost. Pals and 24 -pin), noise accommodated in one chassis and the (20 all 27 series generating unit and RF amplifier. eproms including c-mos and 87XX Noise output, which be up to system may be expanded to provide can series CPUs are catered for by a +30dBm, is more than 65 000 test points. Whilst Gaussian in amplitude variety of models. In all cases, distribution is the system features the ability to and varied by an complete software is provided and the program and test without the aid attenuator of up to 127dB in 1dB of programmers are by another computer, test programs driven easy to steps. The instruments are fully micro- can use menu -style software. Flight be created off-line an IBM processor controlled and information using Electronics Ltd. 0703 L 17v PC/AT or compatible 227721. LA{rSPANNUNG on operation is given on a led display. computer. Smith IEEE -488 bus is standard Atlantic & Jones. 0491 410700. Microwave Ltd. 0376 550220. Switches and relays Data logger. CS 1041, a portable Electronic loads. The Zentro Elektrik diagnostic tool for process control Miniature latching relays. Since no ELA200 and ELA500 electronic loads. systems. is based or MEDACS coil power is consumed when the process control technology and is which sink 200W and 500W. are now relays are in a steady state, operating on the UK market. For use as test compatible with systems running temperatures are low. During loads for PSUs and batteries, they can Lotus 1 2 3 , IBM PS2, AT 0S2 or switching, the single coil version be used in either constant -I or MS-DOS. It will accept either needs 150mW for 6ms and the constant -R modes. Two ELA200 analogue or digital input from the host double-coil version twice that power, system, logging versions cover 1-40V at 0-40A and and time -stamping also for 6ms. Coil voltage can be from events at 100ms resolution. Data 1-75V at 0-20A, while the 500W type 3 to 48V, and contacts, in a two -pole handles 1-75V at 0-99A. The constant acquisition is controlled by pre-set changeover format, are rated at resistance is adjustable at the front parameters. Status Instruments Ltd, 30V/1A and 125V/0.5A ECC LOST 0684 panel from 0.111 to 30k11 and 0 040 to 296818. Electronics (UK) Ltd. 0628 810807. 10k0 respectively. Gresham S Powerdyne, 0722 413080. Flowswitches. Watermill Literature flowswitches are primarily developed 100MHz oscilloscope. A compact for the automatic operation of water four -channel, 100MHz oscilloscope, Data, power instruments catalogue. pressure boost pumps, but are the V-1085' features: sweep -time Amplicon Liveline's catalogue suitable for a wide range of other 338 ELECTRONICS WORLD + WIRELESS WORLD April 1990 NEW PRODUCTS CLASSIFIED applications. They are designed for software is available for PC, OS/9 and provides 16 single -ended or eight 32kHz real time clock. The EM Microelectronic M3001 is a direct in -line connection and include a Sun platforms and includes a 980 differential analogue input channels, -Mann built-in solid-state power -control function library that makes the board jumper -programmable gain monolithic low -power c-mos device for a real time circuit. Switching sensitivity of 3 or 4in easy to use. Future Digital Systems instrumentation amplifier, a high intended use as 32kHz for processor head of water, or a flow rate of 0.2 to Ltd. 0256 882760. speed 12 -bit A-to -D converter. two clock system 110 applicat ons. Time information is 0.6 litres per minute, is a factory pre- 12 -bit D -to -A outputs, 16 digital in a 16 x ram an 8 -bit set to customers requirements. The I/O board. MetraByte's MacAdios II channels and 3 counter/timer stored 8 -bit and in the ram stores the user switches are rated up for flow rates JR provides high-speed high- channels. The 12 bit A -D converter is status word of up to 1200 litres/hour, and can be performance data acquisition and accurate to within 0.02% with a programmed mode operation. 12 Automatic leap year is used with a wide range of fluids with control for the Macintosh II. Th s unit conversion time of 12.5ns. With -bit correction temperatures up to 110°C dependent consists of a multifunction. NuBus resolution, the least -significant -bit provided MCP, 0734 772345 upon chemical composition and compatible analogue and digital I/O value is 4.88mV in the +10V ange. pressure. Watermill Products Ltd, board with support software. It Keithley Instruments Ltd. 0734 0883 715425. 575666. Transducers and sensors Pressure sensors/transmitters. A COMPUTER range of piezoresistive pressure sensors and transmitters been Data communications peripherals uses the IBM PC/XT/AT as its host designed for severe environmental Computer Pronto Electronic Systems, 01 554 -welded products applications. Featuring an all Digitiser tablets. Wacom digitiser 6222. stainless -steel construction, the Secure networking system. VSLAN cordless tablets come with either a SenSym PS.GA/GC series are sensors secure system will link both puck or a stylus, are totally passive, the BT/PT2000G1A series and mainframe operating requiring no battery and are light in transmitters. Gauge pressure ranges and workstations Software at different security levels. VSLAN weight. The buttons on the puck have are available from +15P to 300PSI or, operates at the physical and data link a positive action. The stylus comes in Ansi standard C compiler. These C as an option, from 1 to 25Bar. Output protocol layers of the OSI two types: the standard '"press to compilers are fully transportable from signals are in the 100mV FSD range. 1802.3) reference model. The VSLAN select"' mode or a pressure sensitive one processor to another with no Celdis, 0734 585171. consists of a single Network Security Centre mode designed for graphics packages more than a single re -compilation (NSC) and to 64 network such as the Artisan software required Programs written for Accelerometers. The EGCS-240D up security being devices connected by a LAN facility. dependent on pressure The full range previous systems can be used as a series of miniature accelerometers The NSC a spans A5 up to AO and comes with base for new development Four has fluid damping and mechanical provides centralised management facility to control the Summagraphics and Microsoft mouse modes of compilation are selectable, overange stops making it robust and operation of the VSLAN and also to emulation software. Source Two Ltd, tiny, small, standard and large. Large able to withstand shocks up to ±10 and audit Marconi 089582 4944 provides a complete C 000g. Various measuring ranges are collect export data Security Systems, 0245 267111. implementation, including long from 15 to the available ±5000g; integers floating-point numbers. units are fully temperature and while Tiny squeezes code into the compensated and, being piezo- Programming hardware Development and smallest possible space Tiny is most resistive. operate in either static will useful for single -chip microcomputers or dynamic modes. Entran Ltd. evaluation Memory and logic programmer. (DC) the such as 68HC11, 8051 and 1802 0344 778848. Pronto Electronic Systems offers VIC/VXI prototyping board. SMS Sprint Expert, a combined where data space is limited The Supporting the VXlbus is a "C" size memory and logic programmer It compilers can separate the data and (6U x 340mm) 8 -layer fully Icaded supports pals and memories up to code areas of the program to produce Vision systems high -density wire -wrap prototyping 5000 -gate EPLDs, PGAs and 4Mb true rom-able code American board, fitted with socketed pins to aid eproms in eight to 84-pin packages It Automation UK Oxford. 0993 778991 Image analysis. OFA-Master is a device insertion and complete with an PC -based product designed primarily on -board full VMEbus interface based for the integration of image analysis on the VTC-068 chip. The board allows PC -based eprom programmer - one of the Flight Electronics range. with external systems such as the use of 7.62mm, 10.16mm, motorised stages, positioning 12.70mm and 15.24mm pitch devices equipment, alarm circuitry etc. in the wire wrap area and PGA Software applications modules are devices up to 17 x 17 pins; +5V. -2V. available for automated image archive. or+! _ -5.2V and ground are taken from the sol. particle sizing, low light level imaging, appropriate pins on the P1 and P2 object tracking. DNA sequencing. connectors and distributed evenly 1. .110 instrument read-out, and laser beam across the board via dedicated layers. :Z analysis. Hardware includes either an BICC-Vero Electronics Ltd. 0703 J' ts. erasable or write -once optical disc 266300. drive, full colour or 3 -channel monochrome video input, real-time Emulator. The Multi -Prom eprom video rate averaging and emulator supports 32 -pin 1Mbyte differencing,and hardware-based eprom devices, enabling software histogram, convolution, thinning and developers to download information connectivity operations. Oxford from PCs to target systems within Framestone Applications. 02357 seconds. The emulator is loaded via 66078. the Centronics printer port at the back of the PC. CMS Software Ltd, 0865 748875. Computer board level Modem design package. The PC -AT products compatible modem design package/ EB-V29 modem, includes a plug-in DSP board. VASP-16, the VMEbus modem board and communication board from FDS is now available with software. The board provides data - enhanced speed processors giving pump and source code level control benchmarks 30% faster. 30MHz software for the V25 16-bit Zoran Vector processors make the microprocessor and the ItPD77P230 VASP-16 the fastest integer DSP digital signal processor operating in board on the world market, claims 24 -bit fixed-point format. The software FDS. It combines a TMS320C25 scalar is modular in structure. allowing processor running at 40MHz with four modifications and additional features 30MHz Zoran Vector co -processors, to be incorporated and the hardware along with fast VMEbus and multiple includes analogue front end, line MAXbus 8 and 16 -bit I/O ports. All I/O telephone interface and two DTE runs concurrently with processing for interfaces for either PC data or V.24 maximum throughput. The MAXbus (RS.232C) communication. NEC interface standard is used. C source Electronics (UK) Ltd, 0908 691133. ELECTRONICS WORLD+ WIRELESS WORLD April 199(1 339 PIONEERS orne days a stressed employee might feel he could shoot the boss. One day. one did. On the 4th January 1888. J. M. Raynaud, the Chief Engin- eer of the French Administration of Posts and Telegraphs and Director of the Telegraph College, left his office in the Rue de Grenelle in Paris at I I.45am to walk home. As he walked, a man approached him and fired six shots from a Bull 9mm revolver. Raynaud col- lapsed. After receiving first aid he was carried home on a stretcher. The assailant was one Louis -Victor Mimault. a telegraph engineer who also worked for the French telegraph service and who claimed to be the true inventor of the multiple printing telegraph named after Emile Baudot. Holding Raynaud responsible for crediting Baudot with the invention. Mimault took the law into his own hands. For Raynaud. deciding between rival tech- nical systems proved to be a matter of life or death ... he died in agony eight hours after the attack. Whatever Mimault may have dreamed, it was Baudot's name that went into the history books. Baudot's invention that established time -division multiplexing in practice, and Baudot we remember in the name of the unit for the speed of signalling: the baud. The baud was proposed as the unit of tele- graph signalling speed at the Interna- tional Telegraph Conference in Berlin in 1927. Emile Baudot was born at Magneux. in Marne. France, on the 11th Septem- ber 1845. very early in the era of the electric telegraph. llis father was a farmer (though one reference has him a shoemaker; perhaps he was both) and his mother a dressmaker. His formal education was limited to that provided by the local primary school: there was Emite Baudol (IEE) not even a dream of a university place for him. His vocation was to follow in his father's footsteps and he trained as a farmer. He has been described as being devoted to agricultural work and it is said that throughout his life he jealously guarded the simplicity of his upbring- ing. One contemporary. Montoriol. PIONEERS recorded that Baudot loved to speak of the rural life of his youth and the con- 40, Jean Maurice Emile trast he met when he joined the tele- Baudot (1845-1903) graph service. He "did not blush at his The farmer who became famous 340 ELECTRONICS WORLD-WIRELESS \VORLD April 1990 PIONEERS ing messages. Its capacity had been increased by the Frenchman Bernard Meyer who had adapted it to allow four simultaneous signals to be sent along one wire. The other was, of course, the Hughes printing telegraph which sent only one message at a time. Baudot had already started to acquire a reputation as an inventor for improve- ments he had suggested to existing tiü ilPBodÚ1luÍt equipment. He was now encouraged by the Chief Inspector of the exchange. M. Héquet, to design a "multiple Hughes". In itself the encouragement was some- thing of a reward for his desire to search r a out improvements, but it did not extend him 'firm's time' in which to .4 -. - - to allowing work out his idea. He was still expected to fulfil his normal duties and so it was I, his own free time in the evenings which was spent designing his multiple print- ing telegraph. multiple printing telegraph, installed at the Administration des Telegraphes in Paris. Baudot's As work progressed, his own meagre modest origins", wrote Montoriol. and In September 1869. the year he resources became insufficient for him to enjoyed his ultimate fame and success joined the Telegraph Administration, construct his machine and so he turned without vanity. he was sent to Paris for a course on the to the Telegraph Administration, which At the age of 24 Baudot left agri- famous Hughes telegraph. which auto- cultural work and joined the telegraph matically printed its message at the Keyboard and coding system of the printing service where he was to become famous receiver in Roman type. This superb telegraph transmitter. as the inventor of a new telegraph sys- machine, invented by the American tem. The crux of his system was the David Edward Hughes and patented in combination of an output printed on 1855, deserved its long and outstanding paper in plain language and the use of success in America and on the Con- time -division multiplexing to send more tinent. It "was magnificent printing than one message at a time down a line. apparatus." wrote Baudot. "whose Printing telegraphs. as they were ingeniousness and perfection caused me known, were already in service and to abandon the idea of following in its others had experimented with embryo track." His own ideas evaporated in the time -division multiplexing. But it was face of the Rolls-Royce of printing tele- Baudot who combined them into a suc- graphs and he studied the Hughes cessful working system. equipment until the following Spring. At the time he joined the Telegraph After completing his course Baudot M. . Doc Md. Guae MA. Gnón c he was. in his own joined the Central Paris telegraph sta- V IV III Administration 61Iv I II III I II words, "completely ignorant about the tion in July 1870 before moving to Bor- I . A 15P71. existence of printing telegraph equip- deaux at the end of August as an , g 8 was limited to a employee 5th class. By then the Franco- 0 ment". His knowledge C9 fR - superficial understanding of the Morse Prussian War had broken out and by the !]D0 S; and the dial telegraphs. To anyone end of the year he had been commis E 2 with the rank of Lieutenant and . meeting him, an agricultural worker sioned E 8 B would was serving with the military telegraph with only a basic education, he : V ' the Second Army. After the F have seemed an unlikely candidate for service of W 1 fame which would last over a century. war ended, Lieutenant Baudot once .' Nevertheless. his aptitude for inventing again became a civilian and returned to f ° Y 3 soon came to the fore. Before long he duty in Paris in February 1872. [ : 2.in [-3 Z : a>r was developing his own ideas for a new It was about this time that he began to I dial telegraph which, however, was speculate on how the two quite different L = (RK i ;I: ;: never built. As a paper invention. it was telegraph systems then in use in Paris h fM ) BLA,Cde CHIfiREJ could be combined. One was the Morse . no better than many implemented years N BLANCdtLETIRES, before by dozens of inventors of whose system which needed a specialist opera- WEE( work he was totally ignorant. tor to decode and write down the incom- lI B_5, '- .. m o a.: April 1990 ELECTRONICS WORLD+ WIRELESS WORLD 341 PIONEERS at that time did not have a research lab- oratory. To persuade them to back the project with cash and materials he needed drawings produced to a profes- sional standard. Others with the neces- sary skills were enlisted to help. they too giving up some of their evenings. At last, on the 17th June 1874. Baudot obtained his first patent for his "Sys - teme de télégraphie rapide". It came. incidentally, six months after Mimault received his patent for his own inven- tion. Three weeks later Baudot offered his patent to the Telegraph Administra- tion in exchange for the funds to build it. Transmitter (left) and receiver. Sixth contact at top of receiver distributor synchronized the two On the 25th July Baudot sent a letter arms, which were driven by clockwork. to the authorities describing his pro- posed equipment. A five -man commis- vidual telegraph equipments to the line teenth of a second. About 140 letters sion (including M. Raynaud) was set up in series. Each telegraph contact was could be sent in a minute. per operator. to examine the proposals. They recom- further subdivided into five segments though a typical speed was around 20 mended a budget of 2000 francs for the representing the five units of the Baudot words per minute.2 Later, machines construction of a prototype. In Decem- code. The arms were synchronized by were designed to handle 60 words per ber the following year (1875) tests driving the one at the receiver slightly minute. began which led to a quintuple tele- faster than that at the transmitter and Mimault, meanwhile, had progressed graph being made for regular service) using a sixth contact to apply a brake along his own path of invention. Also In his telegraph Baudot took advan- once every revolution. Both the trans- based in Paris, he had met and become tage of the fact that the pulses compris- mitter's and receiver's arms were driven friendly with Baudot when both were ing the signal were present on the line by clockwork. young men and their acquaintance had for only brief moments. leaving the line For time -division multiplexing (a continued. His inventions did not, how- idle for much of the time. Several term not then used) Baudot needed ever. find the favour of the Administra- machines could use the line if their sig- each character to occupy the same tion in the way that Baudot's did and, as nal pulses could he so arranged. as it length of time. Each, therefore. used we have seen. he took his revenge. At were, to fit in between each other. To do five pulses which could he positive or his trial he was found guilty of fluffier. this he made a segmented distributor for negative. In modern parlance. it was a but not of premeditation. and was sen- each end of the line and this assigned the five -hit code of ones and zeros. At the tenced to 10 years forced labour and 20 line to one message at a time. Six opera- printer this code gave a geometric pro- years imprisonment. tors could share the line in this way. The gression such that the first pulse could Baudot died in 1903 at the early age of distributor arrangement had been used move a type wheel one position. the 58. Montoriol described him as pre- earlier in France by Bernard Meyer, next moved it two positions. the next maturely worn out by a life of labour also of the Telegraph Administration. four positions. then eight and then 16. without rest hut. unlike many inventive The revolving arms of the distributors giving 32 positions in all. In this way the geniuses. he was privileged to have seen were connected to the line. As they required letter could be brought into his genius "radiate around the world". swept round they connected the six indi- position at the right time and the mes- llis telegraph met with rapid success sage printed in plain language. It when it was introduced in France and appears that. initially. Baudot used a was soon in use throughout Europe. One terminad of a multiple telegraph. sixth pulse to extend the progression to India and South America. An early 32. In his description of the Baudot tele- British use was on the Anglo-French graph published in 1921, Fleming cable and it was used extensively by the described it as "certainly one of the British Telegraph Service. Fleming most ingenious telegraphic instruments ranked it with the Wheatstone Auto- ever invented".2 matic and the Hughes Printing Tele- Writing 46 years after the initial graph as one of only three systems to invention Fleming could point to only have had extensive general use one defect. the "nervous strain it puts throughout the world. on the sending operator-. The transmit- 2t, - ter f.`,' y' operator had to synchronize his References pressing of the transmitter's five piano I. P. Lajarrige. "ChroniquesTéléphoniques keys to the arrival of the distributor arm et Télégraphiques Collection I-listoriyue at his set of segmented contacts. being des Telecommunications. Ministéres des P et T. 1982. neither too early nor too late. It was like 2..I.A.Fleming. "Fifty Years of playing to the strictest of tempos. The Electricity." Wireless Press. London. 1921. :orrect time was signalled to him by a t 'cadence tapper'' which made a sound ,I, . -, It i o tell him to press his keys. An The author gratefully acknowledees the lectromagnet then held them down the information provided by France Telecom on =quired length of time. about one four- which much of this article is based. 342 ELECTRONICS WORLD+ WIRELESS WORLD April 1990 DESIGN In a previous article published in the February 1989 issue of Electronics & Wireless World I described an approach to audio power amplifier design that goes AUDIO against most current thinking, in that it incorporates a considerable amount of negative feedback. Its use of fets is the key to the design. as they introduce less -over distortion than bipolars and, ER, cross F S when driven sensibly. are capable of a better high -frequency performance. This paper describes an amplifier fol- lowing that approach. AND The common -mode problem In the first article I stated, without offer- ing proof. that negative feedback did nothing to improve errors in the dif- FEEDBACK ferencing process that occurs at the input of an amplifier between the applied and feed -back signals. Figure 1 shows a simple feedback sys- over the signal cycle, since it contains tem built around a differential ampli- Ivor Brown builds the non-linearities of both A and A,,. It is normally assumed that the fier. on his approach, The non-linear terms in k will extend to amplifier only responds to the dif- higher orders than those present either its input voltages, that ference between described in an in A,,. or A,,. is First. suppose there is no feedback. V=A,jV(' -V(- earlier article, to the so that V(+)= V,. and V(-)=O. The amplifier's gain is given by where A, is the voltage gain of the careful application amplifier. In this case normal feedback theory applies and the overall gain of of negative A,=`'=A,,,(I+k) the system (A,,) with a feedback frac- feedback in fet audio Now with feedback. V(+)=V, and tion of 13 is V(-)= (3V. and V A, power amplifiers A,f= _ V \,, (I + k) V, (I +A,13) A` V, II+A,,13(I-k)I and if A,B> I If A,,> I and k is small. A,-. 1 (l+k) A 13(1-k) Since B is determined by passive com- ponents. the gain of the feedback Using the binomial expansion on the the k system can be accurately defined and denominator and neglecting squared term, we finally have made very linear. V t Now suppose that the amplifier also Differential (1 +2k) responds to the sum of the input volt- amplifier ages so that The effect of feedback is to make this Vo=AfV(+)-V(-)) Vs source of distortion approximately Feedback i va twice as had as it is in the basic amplifier. +AIv(+)+V(-)I nttenuator Feedback does not improve matters, it where A,, and A are the gains for dif- makes them worse! ferential and common -mode signals respectively. A can he considered as the error in the differencing process. not Fig. I. Simple feedback amplifier The prototype circuit the usual definition of common -mode using a differential amplifier. The Figure 2 shows the complete circuit dia- gain. Let A,,.= kA,, expecting k to he input signa! is the difference and also gram. On the right there is the four-fet small. It will not. however. he constant the sum of the input voltages. output stage: all the devices are oper- April 1990 ELECTRONICS WORLD+ WIRELESS WORLD 343 DESIGN ated in the common -source mode and in class A13. The output power fets are Hitachi types 2SK346 N -channel and 2SJ102 P -channel. The driver pair are ZVNOI06A and ZVP0I06A. N- and P -channel respectively. Input The basic two -stage output amplifier 15k has a voltage gain of about 40 when 15 On loaded by an 8 -ohm resistor, reduced to just below nine by the 220Q and 22Q feedback resistors. Some degree of quiescent current stabilization is obtained by the use of two separate feedback attenuators and the two 0.47Q wire -wound resistors. For safety under test conditions. the 220Q resistors (not wire -wound) need to be rated at 2W. The bandwidth of the complete output circuit is 3MHz. TOn 47k The fuse has a resistor across it to preserve overall feedback when the All OVolt connections are taken to the common terminal of the power supply short is removed. The lOQ and 100nF The common terminal is connected to the chassis Zobel network prevents the effective The speaker return is connected to the common terminal load ever becoming too inductive. The 111I I inductor to maintain stability with Fig. 2. Complete circuit diagram the a capacitive load is made from 20 turns of power amplifier using four fets in the output. of 22SWG wire, close -wound on a 6mm diameter former. fets is larger than that required in large spikes to appear in the earlier Quiescent t current through lie output bipolar designs but is not critical: stages. The inclusion of the hack - around 80mA is usually chosen. How- to -back zeners on the emitter -follower ever. the output circuit is temperature outputs zeners limits the spikes applied °de sensitive and some compensation is nec- to the output circuit and removes the essary. The four diodes and the driver problem. fets are all mounted in a small isolated The rest of the amplifier consists of la) 1kHz, output 15 watts heat sink. Adjustment of the 5kQ two emitter -coupled stages with current potentiometer that sets the quiescent sources in their emitter circuits to give nRdn current is critical and a multi -turn com- good common -mode rejection. The dif- ponent should he used. A slightly nega- ference between the input signal and the tive temperature coefficient to the fed -back signal is only about one two - quiescent current results when the hundredth of either signal and, as power devices are bolted to a substan- shown later. one 96db emitter -coupled stage 5 kNe I kllr tial heat -sinking chassis. The arrange- does not give adequate common -mode ment has proved satisfactory over many rejection. To minimize the output offset hours of use and testing. voltage, the input emitter -coupled pair ° 1B The Pets used are not fitted with pro- should have their DC current gains 1kHz, 15 tection zener on their gates. lb) output watts diodes but matched at a collector current of I 0011 none should be necessary. since the gate and then fixed together with epoxy voltage rating cannot be exceeded. adhesive. The choice of transistors was !however. as one early amplifier was made simply because they were avail- approaching overload. both its power able: I see no reason wit; other types devices went into conduction. putting should not he used with equal success. 1.Ao.kV9fi.,l}.,;r4JN.4 ti an effective short circuit across the Frequency response of the stages is 11 ,1' power rails. As overload is neared. the tailored by the RC networks between overall feedback tries to keep the out- the collectors to provide stability. If the put a faithful copy of the input. causing types of fet in the output stages are changed. then it is likely that these sal- Fig. 3..4t (a) is the output at IkHz, Ic) 1kHz, output 15 wntts ues will have to he changed as well. The second and third harmonics being barely values were calculated using a computer risible; higher -order harmonics are not model of the open -loop amplifier to give present. The spectrum at (b) was adequate stability margins when con- obtained by reducing the fundamental to nected to a load of 8Q and 2.2µF in show harmonics, which are at a low parallel. Under normal loading the mar- level. The spectrum of the small -signal ..,.....t gins are about I4d13 and 45° and the 96ilR amplifier is at (c) and shows the 2, OH: IOkQ and 2.2pF phase -advance net- harmonics that cancel those in the work in the main feedback attenuator output stage. was the only modification necessary: 344 ELECTRONICS \\'ORLD+ WIRELESS WORLD April 1990 DESIGN quency, so demonstrating the good crossover performance obtainable with fets. Comparing this spectrum with the previous one, and considering the 46dB or so of loop gain, it appears likely that, at the final output, all the harmonics above the fourth are below - 100dB. At 5k this low level of distortion one cannot expect much correlation between the in Figs 3h and 3c 4x relative amplitudes 1H4o since there must he some distortion gen- erated in the small -signal stages. Figure 4 is the 10kHz output spec- 20n 12k 4k7 trum. in which higher -order compo- nents are not evident, the second and 10r increased 1p00k third harmonics being slightly is 2p2 from the IkHz spectrum. This to be e_-_T expected as the compensating networks do introduce some phase shift in the open -loop response at this frequency. High -frequency intermodulation was assessed using the 11 and 12kHz signals from the Hi -Fi News and Record Review test CD. Again, no intermodulation components appeared above the noise level. Figure 5c shows the output for a this comes into operation over 700kHz. changes. At low frequencies. the mag- 10kHz square -wave input. The upper Overall gain is set by the 10OkQ2 and netic leakage field from the mains trans- trace was obtained with an 8S2 resistive IkQ2 feedback attenuator from the out- formers in test equipment can cause load: the lower with a load of 812 and put to the base of the right hand transis- spurious signals. 2.2!íF in parallel. The reactive load tor of the input pair: DC gain is reduced Figure 3a shows the IkHz output causes some ringing. but is well to unity by the I(IOpF tantalum capaci- spectrum, in which second and third damped. illustrating the satisfactory tor. Tests have not detected any altera- harmonics can just he seen above the stability margins obtained. tion in performance when other types of noise. The size of these components capacitor are used. depends largely on the degree of non - The bandwidth of the basic amplifier linearity present in the fets and on the circuit extends from around I Hz to matching of upper and lower halves of 10kHz output '5.c"s nearly IMllz, the passive input filter the output circuit. There is some vari- limiting the system bandwidth to ation between samples of the amplifier roughly 101 Iz-30k1 Iz. The amount of on this point and some do not quite feedback present varies little for all meet the figure I gave in the February audio frequencies. paper. The absence of any fourth of higher -order components above the noise level is typical of all samples. C rM: Measured performance The spectrum in Fig. 3h is for the To limit the number of diagrams in this same output passed through a simple Fig. 4. At MHz., the spectrum shows harmonics due paper. I am only including spectra for an hand -reject filter that reduces the fun- slightly increased low output level of half the nominal maxi- damental by 20dB and the second har- to phase shift, hut nothing at higher mum. 15W, which corresponds to about monic by less than IdB. Higher -order. orders. 30V peak -to -peak into a 812 load. At all cross -over, components are present but lower levels there is less distortion evi- at very low levels, all above the seventh dent in the output spectra. A band-pass being below - 100dB. It is likely that filter was connected between the signal the harmonic levels have been modified generator and the amplifier to reduce by distortion generated in the filter cir- _ ! harmonics present in the input cuit. but the result suggests that minimal 10k -'z squc^e wrie waveform. crossover distortion is present in the t)utp'Jt .:nvet0^Ts Problems of making distortion mea- output waveform. . f surements more than 80dB below the A spectrum of the small -signal ampli- fundamental must be borne in mind fier output is shown in Fig. 3c. which I when considering the results that fol- illustrates the harmonic components fed 10V /Or. is,on low. Variations of over 10dB in the indi- to the fet output stages virtually to Fig. S. it 10kHz square ware with an cated harmonic levels can he obtained cancel the distortion that is generated t42 resistive load (a) and an 81) plus merely by slightly altering the arrange- therein; total harmonic distortion in the 2.2 ph' load at (I)). r? ments of the 0V line or the earth leads output stage is about 1 . The ampli- and poor contacts can also cause similar tudes fall rapidly with increasing fre- 345 April I)911 ELECTRONICS WORLD+WIRELESS WORLD DESIGN Input circuits The fet power amplifier has a nominal Radio input maximum sinusoidal output power of e - 15V (from 12k 30W into 8Q, with a voltage associated gain of 101 CD i/p power defined by 100n amplifier) the feedback loop. However. -1W\M / at its input there are passixe filters which 27k TL O"' reduce the overall gain to 88. so ---- *vv\ -Recording output for 30W 2tiY 2k2 output an input of about I75mV is From gram needed. The input impedance is 1151:Q. 15V ( from equaliser Volume When the filters are driven from a low 10k associated power impedance. the -3d13 frequencies are log 12k amplifier) 55k Hz and 91 Iz. A source impedance of 181( 10k 470k IOk52 mainly affects the 100n upper fre- 0v quency and lowers it to 31kHz. Controls To power amplifier The only essentials are an input selector and a volume control: the inclusion of a Fig. 6. Simple pre -amplifier balance control is a matter of personal arrangement without preference. Today. few recordings are balance control. made with a channel balance that requires correction. hut an imbalance Fig. 7. Layout of balance control circuit caused by poorly positioned loud- to maintain constant total power output. speakers is not unusual. The inclusion of a balance control need not require Fig. 8. Practical balance control to extra active devices in the system. Tone provide 7dB difference between channels controls and steep -slope titters are now - enough to move mono sound between omitted from many designs since. for speakers for a central listener. many designers. the additional active devices needed rule against their inclu- sion. In this paper they will not he con- sidered further. Radio input 4k7 CD ilp Inputs To recording buffer as figure 1 Taking the inputs in a descending order of level. we have first the CD player. Balance 25k The nominal maximum output is 2V From gram lin hut. with the abrupt overload charac- equaliser To power amplifier teristic of digital sources. this figure is unlikely to he found in practice. I sug- gest that I V is a reasonable figure to take as the input needed for maximum 0V amplifier output. The output levels of radio tuners. tape decks and similar sources are not Balance selector switch, a simple non -inverting defined and so reasonable estimates of Figure 6 illustrates a simple arrange- amplifier is incorporated to restore it to the requirements are all that can he ment without a balance control, only its original level. This amplifier also made. From experience. a sensitivity of three inputs being shown for simplicity: serves to isolate the amplifier signal around 400n1V for maximum output the radio input can he duplicated for the from any low -impedance load that may seems suitable. tape recorder and auxiliary inputs. For be connected to the socket. A moving-magnet pickup cartridge this input the 12k4 resistor gives an A simple balance control that main- requires amplification and equalization. input sensitivity of 385mV, the maxi- tains the total output power output The output of cartridges is specified in mum output resistance presented to the terms of mV/cm/s of stylus velocity at power amplifier being 5.5k52. The essence of the design is that the use of fets, with their good high lkI Iz and is usually between 0.5 and 1. For CD the 12ká2 resistor is replaced -frequency performance, in the output stage of a Maximum recorded velocity at this fre- with a 2.5: I attenuator that has - an our power amplifier allows a higher -frequency quency should he 22cm/s. so a sen- put impedance of around I2kQ. The roll -off in the earlier stages and larger sitivity of about IOmV at IkHz is input impedance for this input is about amounts of negative feedback than is cur- reasonable. Moving -coil pick-ups need 33ká2. rently considered normal, while still main- a low -noise preamplifier or transformer The equalizer amplifier for the pickup taining stability. The beneficial effects of feedback, when before the equalizing circuit. These spe- input is described later. carefully used, are then cialized seen throughout the audio range of components are beyond the Since the input from a tape recorder frequencies scope of this article. has been attenuated before reaching the 346 ELECTRONICS WORLD + WIRELESS WORLD April 1990 DESIGN nearly constant for all positions of the 13 =75ps control is shown in Fig. 7. If R,. the Avo f 3 volume -control potentiometer. has a ? T4- See text much greater value than the balance f4= ? Rh. then making R = O.7Rh satis- control T1 = 31B0Ns fies the above condition. For lower val- f1=50Hz ues of R,. the parallel combination of R -Av =1 and R,. must equal this figure. A linear T2 = 31Bus f2 = 500Hz wire -wound potentiometer should be used for Rh as the wiper provides a good the wire element to ground; a R1 R2 R4 short on V composition potentiometer's wiper may -+-C C4 not make contact all the way across the t Ci R3 track and give rise to some crosstalk. j-1 Complete isolation can be obtained by using a ganged pair of potentiometers the terminals of a network _ Rt with their wipers grounded, but with The resistance between R,=lOkQ2 and R,=25kQ2 the loss inthe Ti 171 -T3 T1 T3171+1'3 -12 is too great for the fet Ci- C3 - network (T1 -T2 1(T2 -T3 ) Rt(T1-T2 1 Rt amplifier. T31T1-T3 ) T1*T3-T2 Subjective tests suggest that a dif- C4= C2 = ference of about 7dB will place the Rt(T2-T3 ) Rt mono sound image close to the louder Rt(T1-T2 ) Rt lT1-T2)1T2-T3 1 R1 = R3 - speaker for a central listener. Figure 8 (T1 -T3) Di* T3 -T21í shows a circuit that provides this degree of balance control. R2 = Rt-R1 )t,= Rt 9. Bode of RIAA response, showing the three time constants Pickup eq;..alizer Fig. Straight-line plot T T2 and T3; T, is due to the amplifier running out of gain at high frequencies. The Figure 9 shows the Bode straight-line two networks are similar in performance. approximation to the standard RIAA response defined by the three time con- stants Ti. T, and T3. The diagram shows resistance required by the cartridge will impedance of the network. two networks whose impedance follows have to be obtained by adding a series The voltage -series circuit in Fig. IOb this response. and their design equa- resistor, which may degrade the noise does not suffer the noise problem and tions. The resistance of the network (R,) performance unacceptably. The advan- does provide a high input impedance. has to be considered with the three time tage of this approach is that, provided The 5(IkQ2 can be obtained by means of a constants to define the four component the amplifier has sufficient gain, the fre- shunt resistor that does not compromise values. The performances of the two are quency response accurately follows the the noise performance. The complica- obviously identical. but it may he that tion with this system is that the gain is the components for one or the other are not simply proportional to the imped- closer to preferred values. ance of the network. The algebra given The RIAA network may be con- in the appendix. which assumes a very nected as part of an attenuator in high -gain amplifier, shows that the cascade with a flat -response amplifier. denominator of the gain expression con- to make a system with passive equaliza- tains the correct two time constants, T, tion. Noise considerations necessitate and T. However, the numerator also the amplifier preceding the network and contains two, one more than is wanted. so it must he able to handle relatively One of these we require to be at T,. and large high -frequency signals, which are the other, T4. is due to stage gain tend- severely attenuated by the network. Ia1 ing to unity at high frequencies instead More usually the network is used to of continuing to fall as required by the define the voltage gain of a feedback RIAA response. This problem can he stage. solved by adding a simple cancelling In the prototype system, a feedback fesistor-capacitor filter after the feed- equalizer built round a single IC is used. back stage. TLO7I amplifiers have been used in the The second problem is that the lower Brunel University laboratories for rising break in the amplifier's response does not occur at T,. The network will audio signals at about the 1 V level with distortion products not greater than have to be designed for another time in 100d13 below the fundamental. constant. T,,, so that when included A feedback equalizer can use either (b) the feedback amplifier, the overall voltage -shunt or voltage -series feed- response does exhibit the correct T,. back. In the former case. Fig. 10a. the Fig. 10. Two methods of connecting The appendix shows expressions for T,, -fre- stage will have a very low input imped- feedback equaliser: (a) in voltage shunt and T,, both depending on the low ance, so that the standard 5OkQ2 input and (h) in voltage series. quency gain of the stage (A,,,). April 1990 ELECTRONICS WORLD + WIRELESS WORLD 347 DESIGN t 15V Circuit Al. A2. B 3 C3 = 3n6 3n3//220p 3n3 Gram input I I 7 100n C4 = 10n 10n tOn 11071 I tiF-'\"",---p,----- Output to 2 R3 = 22k 4 202 selector 24k//560k 24k R4 = 300k 300k 300k Rx = 1k5 680 R4 CY 2n2 2n2 o 390p C3 C4 C RY = 2k 2k 4k7 --I I I R R3 1180k /68k `-WV-' 1470YliT 1 Fig. 11. Circuit of pickup equaliser. RC ov network at right avoids the problem of T4. Low -frequency gain in the RIAA 246 response is some 20dB above the gain at 180° IkHz, so a low -frequency input sen- 4.55 Circuit, RIAA TL071 sitivity of about ImV is needed. The A1 gain of the equalizer depends on 90° whether a balance control is included. _ Suitable low -frequency gains for the LU 1.735° amplifier are about 200 for use without a -0 =a balance control, and about -(50 for use -0.1764 with the control; the two circuits will he as referred to A and B respectively. _90° Their overall gains are lower than these figures due to the loading of the passive 2425 filters after the amplifier stages. 10 1585 24.2 -180° I I 1 1 1 1 1 1111 I I IIIIIII IIIIiII 1 I IIIIII 101 FREQUENCY (Hz) 105 2457 Circuit'RIAA 2455 T1071 A2 1736° Fig. /2. Ideal model of moving -magnet -0.1034 cartridge. Looking at component catalogues. it appears that close tolerance capacitors can readily he obtained only up to lOnF. 24.42 10 To avoid capacitors in the network 2441 1943 exceeding this value, R, must not he less than 300k12. The low -frequency stage gains and theoretical numerator time 319 constants. in microseconds. for the two Circuit RIAA TL071 versions shown in Fig. 6 are: B circuit A: A,,,=201 or 46.Id13: T,, = 307.1:1-4= 3.731 circuit B: A,.,,=442 or 52.9dB: 31.78 =313.0:T4= 1.70 1683° 4682E -2° Complete equalizer circuits were ana- lysed with a simple computer package. - The circuit in Fig. 12 models an ideal pick-up cartridge with an output of 5mV at 1kI Iz (V,) and also a frequency -inde- pendent output of 5mV (V2). Frequency 31.610 responses obtained by feeding the equalizer from V, and comparing it to Fig. /3. Results obtained from the equaliser circuit using the three sets of values V, shows the voltage gain at lk I lz and shown in Fig. /1. 3 -IS ELECTRONICS WORLD + WIRELESS WORLD April 199(1 BOOKS ing to a TL071 model with a DC gain of Mobile Radio Servicing Handbook, by 388 318N5 lee 200000. and unity -gain frequency of R. Belcher. M. Fitch. D. Ogley and 3MHz increased the dB errors by about G. Varnell. As its title indicates, this is 25BJ 88 ten times. an essentially practical book on the Figure 11 includes three sets of practi- choice, installation and maintenance of 288 6B cal component values. Set A, is the best systems and equipment. T2x Tw s that can be done for the lower -gain It is not intended as a specific guide to 158 - 1P equalizer with single components from particular equipment. but rather covers the 5% range of values. Set A2 is an the subject in a wider sense, thereby lee - 2e improved version with two sets of paral- allowing the engineer to gain sufficient lel components and set B gives the knowledge of the subject to develop his 5B e higher -gain system and has a response own methods and to apply it to any 28 25 38 35 48 45 58 55 6B within 0.1dB over the range 10Hz to hardware he might encounter. LOW FREQUENCY VOLTAGE GAIN dB 20k1 lz with no components in parallel. The first few chapters discuss the The results of analysing these circuits principles of the subject and are fol- lowed by four on principles and practice Fig. N. Variation of T2, and T, with are in Fig. 13: the phase responses do Equaliser network must be designed to not deviate far from zero degrees. of communications and RF measure- use T,, to take account of amplifier's Using 1% tolerance components to , ments. There is a section on EMC and a frequency response not corresponding to build these circuits, the responses are comprehensive chapter on aerial selec- unlikely to deviate from the computed tion.. installation and maintenance. curves by more than 0.2dB. All the cir- Finally, three chapters are included on cuits that have been constructed fall cellular systems, digital techniques and well within this figure. data communications. Heinemann Pro- the accuracy of the circuit. Initial ana- The 100nF input capacitor provides fessional Publishing. hardback. 281 lysis included a very high -gain. wide - the additional bass -cut at about 20Hz as pages, £25. band amplifier model, with the theoreti- required by IEC specifications. while cal values accurate to four figures, for the 180kQ2 and 68kQ2 resistors provide Telecommunications Primer, by the passive components. Responses the required 50kQ2 input resistance. the G. Langley. With the implications of were both correct to within ±0.01dB former also serving to keep the input at the buzz words -information techno- over the range 101-Iz to 100kHz. Chang - DC ground potential if left open circuit. logy" well in mind, the author presents in this third edition a large number of sections on theory and practice. It is not written for the communica- tions engineer. but is intended for rela- to unity as Z falls to zero at high fre- Appendix managers who need quencies. The equation will not, in gen- tively non -technical guide to what is hap- eral, give the wanted value for 12, so an understandable Let the impedance of the RIAA net- in the field and need to be able to replace T3 by T24; a value for T2, will be pening work be Z. the subject: and found to give the correct overall talk intelligently on In Fig. 9, who are not pri- response. also for those students with telecomms and R,(1+sT2) We require the numerator to be of marily concerned Z- IT but who nevertheless must be famil- (1 + sT,)(1 + sT3) the form (1+sT2)(1+sT4), so the `s' iar its fundamentals. squared term must be (T,..1.4), and the with The book is written simply and con- Assuming a very high gain amplifier the 's' term (T,+ T4). Comparing these cisely and is well suited to its professed gain (Au) of the voltage -series circuit is terms with those in the last equation for task of informing the uninitiated. Pit- A,. with T2 replaced by T2 we have R,+Z man Publishing. card covers. 182 pages, A. - R, from the squared term £9.99. Newnes Microprocessor Pocket Book, At very low frequencies TIT3 T, = by Steve Money. This is one of a series AvoT2 R, of extremely useful little books which A,=A,ro=A, R, from the linear term function as aides-n2é,noires for the prac- tising engineer and avoid the need to Substituting and rearranging terms we A,,T2+T,T3-T2(T,+1-3) sort through a collection of sources. T2, _ Microprocessor operation is find (A,.a - 1)T, described and a general discussion of = The variation of T2, and 14 with A,,, is typical instruction sets is provided. lead- plotted in Fig. 14. As expected, when ing to a number of sections which des- 1 +s[{T,+T3+(A,o- 1)T.}/A,ro] the gain is large, T2x approaches T2. The cribe in detail the common 8bit. '^/12bit + s2[T,T,/A,,,] 0 graph shows how much alteration to the and risc processors. (1 + sT,)(1 +sT3) basic network is necessary for low -gain Sections on displays and develop- equalizers. In designs where only two or ment systems complete the book, The denominator is as required, but the three discrete transistors stages form except for lists of abbreviations and numerator contains two time constants. the amplifier, a low -gain equalizer is some useful manufacturers' addresses. There will be a high -frequency break unavoidable if the limited amplifier gain Heinemann Profession Publishing, hard (T,) because the gain of the stage tends is not to affect the overall response. E back. 252 pages. £9.95. April 1990 ELECTRONIC'S WORLD +w IRELESS WORLD 349 BRAND NEW & BOXED AVO Model 8 MK5 TEK 475 SCOPES Multimeters 200Mhz. Dual Beam Delay Timebase. With AVO Ever -Ready Case, TESTED & CALIBRATION VERIFIED.. . Probes, Leads & Spare Batteries... SPECIAL ... £85.00 SPECIAL ... £ 125.00 o< Q\ OO°'4 ANCHOR SURPLUS LTD. k°x The Cattle Market `0,00,510,2-,15.e<%_, NOTTINGHAM ENGLAND 04 Q-1 AVO Model 8 NG2 3GY BRAND NEW & BOXED (Mil' Test Set 1 version) MULTIMETER with AVO Ever -Ready FLUKE 8021 LCD ALL PRICES EXCLUDE VAT & CARRIAGE Multimeters, with Case & Leads. case, Leads, Probes... VGC.. TESTED ... £50.00 SPECIAL ... £85.00 ALL GOODS FULLY TESTED & GUARANTEED VISA ACCESS IF YOU ARE NOT 100% SATISFIED...YOU GET A 100% REFUND ON THE PURCHASE PRICE!! ALSO IN STOCK NOW: TF2002A, 20026,2006,2008 Signal Generators...PHONE For Latest TEK/TELEQ(IIPMENT D755 TEK 468 100MHz Digital Storage HP 1600A LOGIC ANALYSERS Oscilloscopes. ..50Mhz...Dual Trace.. . Oscilloscopes C/W PROBES & LEADS Delay Timebase. C/W Service Manual Excellent Condition and Probes...TESTED & TESTED CALIBRATION VERIFIED! TESTED & CAL VERIFIED,,/ J\ £275.00!! S £1200.00!! ALSO HP 16C7Á £300.00!! ,/ AVAILABLE: PHONE!! (0602) 864041 or 864902 FAX: (0602) 864667 CIRCLE NO. 144 ON REPLY CARD R.S.T. LANGREX R.S.T. Genuine spare parts SUPPLIES LTD for CLARK MASTS One of the largest stockists and eR PARTS CENTRE distributors of electronic valves, tubes and semiconductors in this country. For all your genuine spare part requirements contact: Over 5 million items in stock covering more than SIMON BENNETT 6,000 different types, including CRT's, camera TELEPHONE: (0983) 67090 tubes, diodes, ignitrons, image intensifiers, IC's, TELEX: 86224 Spares G klystrons, magnetrons, microwave devices, opto FAX: (0983) 811157 electronics, photomultipliers, receiving tubes, rectifiers, tetrodes, thryatons, transistors, transmitting tubes, triodes, vidicons. All from major UK & USA manufacturers. Where still available. Obsolete items a speciality. Quotations by t return. Telephone/telex or fax despatch within 24 hours on stock items. Accounts to approved customers. Mail order service available. LANGREX SUPPLIES LTD 1 Mayo Road, Croydon, Surrey CRO 2QP. Tel: 01-684 1166 Telex: 946708 CLARK MASTS TECHNICAL SERVICES ) LTD Fax: 01-684 3056 20 RINGWOOD ROAD. BINSTEAD. ISLE OF WIGHT P033 3NX ENGLAND CIRCLE NO. 145 ON REPLY CARD CIRCLE NO. 146 ON REPLY CARD 350 April 1990 ELECTRONICS WORLD+ WIRELESS WORLD liNI D V P Et E A Pe~1111D SERIES Engineering I/O Cards for IBM PCIXT/AT & Compatibles EDUCATIONAL SYSTEM SERIAL & PARALLEL CARDS 8088 16 Bit System a LCD Display PC Serial/Pa-allel/Card £35 PC -win Seral/ Parallel Card £45 ROM/RAM DISK CARD PC Serial R5-232 Card (COM1 or COM2) £29 PC 3ual RS -232 £35 - 360K/1.2Mb PC EPROM/SRAM Memory Cartridge PC 4 Port Multi -Serial RS -232 Card £75 PC 3 Port M dtl-Serial RS -232 Card £169 INDUSTRIAL CONTROL CARDS 16 Channel Opto InpuVRelay Output . RS -422 CARDS Amplifier and Multiplexer PC Serial RS -422 Card £55 Card : mV mA Signal Conditioner PC Dual Seal RS -422 Card £65 8 Channel SSR Drive Card AC (280V/3A) DC 1' .. « 'ryc" PC Dual Port RS-422/RS-485 Card £129 (60V/3A) , ,_°,...1W5.1510-.inñ PC 4 Port Serial RS-422 Card £279 ; ''t\ - PC RS £499 8 Port Serial -422 Card DATA INTERFACE TEST SETS Parallel Tester IEEE -48E CARD Tester £49 - RS -232 (Single/Dual States/Mini) PC IEEE -488 £139 RS 48 programmable I/O lines -232 Break Out Turbo Pascal, C 8 Quick Basic Support Package £45 RS -232 Jumper Box Tri-States Tester 3 independent 16 bit counter Loopback Tester DIGITAL I/O CARD Interface Problem Check Test Set 16 LED I/O display 192 Line 8255 Digital I/O Card £159 ' COMMUNICATIONS Port selectable address ANALOGUE/DIGITAL CONVERSION 3270 BI -Sync Emulation Card PC Modem Net (4 x1400 BPS) CARDS Complete range of 1 PC Fax Card (Telecom Approved) 8 Bit AD/DA Digital I/O Card £149 - 12 Bit AD/DA Card £85 - INDUSTRIAL COMPUTERS SUB SYSTEMS PC-LabCard s 14 Bit AD/DA Card £165 ' Industrial PC AT (80286 8/12MHz) Motherboard i.e / engineering Add-on's foe PUxr/A1 INTERFACE CONVERTERS Industrial Computer Chassis (19" Rack Mountable) PC -BUS Card Cage 8 Accessories Serial to Parallel Interface £45 Parallel to Serial Interface £45 EPROM/PAL/SINGLE CHIP RS -232 RS-422 Bi-Directional Interface C59 PROGRAMMERS & TESTERS FOR PC RS-232/RS-485 BI -Directional Interface f99 RS-232/20mA Current Loop Bi-Directional £79 XT/AT PC RS -237 Repeater £39 1/4/4/16 Gang E(E)PROM Programmers (16K -1024K) L PAL Programmer 8748/8751 Series Programmer T PROTCTYPE CARDS Memory Tester osco 8 Digital £59 Universal Device Programmer D PC Universal Card - ELECTRONICS PC Extension Card 3 Slot Board £59 - PC Design Tool £259 MISCELLANEOUS 289 Birchfield Road System - PC Talk (8K Bit/Sec 8 Bit Linear Sampling Rate) Perry Barr Birmingham Tel: 021-344 3228 PC TV Video -Picture Framestore B20 30D Fax: 021-356 3828 CIRCLE NO. 147 ON REPLY CARD NEW: HANNING WINDOW RESULTS LOGFILES SP 1 C E AGE ent ysis ,wa. .. transient response árising from a Non -Linear Analogue Circuit wide range oftation can be examined. 7 y types of of excitation are offered (impulse, Simulator £245 complete l sine wave, step, triangle, ramp, square, or £70 per Module ?, 1 and pulse train);the parameters of each are user -definable. Reactive components Those Engineers have a reputation for supplying the best value -for -money in microcom- , - may be pre -charged to steady-state con- puter-based circuit simulation software. Just look at what the new fully -integrated SPICE - _ dition. Up to 13 voltage generators and Advanced Graphics Environment (AGE) package offers in ease-of -use, performance, current generators may be connected. and facilities: _ _ _ . 1 i Sweep time is adjustable. Up 104 obe SPICE AGE performs four types of analysis simply, speedily, and accurately. nodes are allowed, and simultaneous Module 1- Frequency response Module 3 -Transient analysis ' - mpulse response of low pass fitter plots permit easy comparison of results. Module 4 -Fourier analysis Module 2 -DC quiescent analysis transient analysis) 1 Frequency response wrtia SPICEAGE provides a clever hidden 4 Fourier analyses Fourier trans- ' _ benefit. It first solves for circuit quiesc- SPICEAGE performs .., ..-- ence and only when the operating point is forms on transient analysis data. This established does it release the correct allows users to examine transient array- .. I most prevalent - I"' small -signal results. This essential con- six waveforms for the Ire- Y. components (amplitude is plotted - I - _ rapt is featured in all Those Engineers' quency against frequency). Functions as a simple _ software. Numerical and graphical (log & spectrum analyser for snapshot of Iran- -- - 5. lin) Impedance, gain and phase results \ - - i sients. Automatically interpolates from _ 's can be generated. A 'probe node' feature s '- - - allows the output nodes to be changed transient analysis data and handles up to , ' Output may be either dB or volts; the zero 512 data values. Allows examination of - .-IL(.uij i - winnows. dB reference can be defined in six differ- waveform through different Powerful analytical function is extremely Frequency response of a low pass filter ent ways. easy to use. Spectrum of rectangular pulse train Circuit (Fourier analysis) 2 DC Quiescent analysis .w,.. SPICEAGE analyses DC voltages in . -T.:r; ', I If your work involves designing, developing or verifying . I network and is useful, for example, for I ;g,-. ' ,. -: any analogue or digital circuits, you will wonder how you ever setting transistor bias. Non-linear compo- it 1: i it:: :u ! i:,21; - :Ñ - nents such as transistors and diodes are n iii t managed without Those Engineers circuit Simulation catered for. (The disk library of network I Software. models contains many commonly-used components - see below). This type of A good range of properly supported and proven programs is analysis is ideal for confirming bias condi- tions and establishing clipping margin available and our expert staff are at your service. prior to performing a transient analysis. s. ______Tabular results are given for each node; Telephone: Charles Clarke on 01-435 2771 the reference node is user-selectable. DC conditions within model of 741 for a demonstration disc. circuit L J o 106a Fortune Green Road West Hampstead O London IDS _ -r2(9(9U 2 LTD [2009 Tel: 01-43-435 2771 - Fax: 01-435 3757 CIRCLE NO. 149 ON REP! Y CARD April 1990 ELECTRONICS WORLD+WIRELESS WORLD 351 Business Integrated Test Systems Our very simple offer =e Unit 1, Holmside, Harrow Rd. East to craftsmen Dorking, Surrey, RB4 2AU SOFTWARE DEVELOPMENT TOOLS APRIL Eprom Emulator £ 170 inc P&P 8/16 bit emulation up to 32K as standard. 2764, 27128, 27256 devices. Power drawn from Device Under Test Low power consumption (30mA typ). Intelligent PC software to load Binary, Intel format files etc. Software includes a full function monitor with on board help. Dimensions: 200 x 112 x 30. Access time better than 150nS. All cables & documentation supplied. T If you would like more information or place an order please write to: y - Business Integrated Test Systems - 27513 CIRCLE NO. 151 ON REPLY CARD Standard products k,- and f, custom metalwork Better tools to work with Antex TCS 240 V 50 W and Tools specially designed for fine TCS 24 V 50 W. precision soldering. Temperature Controlled Solder- Ideal for all electronics crafts- ing Irons for electronic and elec- men and hobbyists. trical applications - especially field For full information on the maintenance and repair. comprehensive Antex range of Temperature range 200° to soldering irons, power supply 450° C. Analogue proportional units and accessories, please control ± 1%. Max. temperature clip the coupon. achieved within 60 seconds. PLUS Antex M -12W; CS -17W; and Standard products include a wide range of 19" XS -25W. Available in 240 or rack mount cases, rack mount strips and 24 volt. Electronics blanking and ventilation panels Bespoke work dealt with and I -Antex (Electronics) Limited. 2 Westbridge Industrial Estate. Tavistock, quickly efficiently Devon PL19 8DE. Tel: 0822 613565. Fax: 0822 617598. Telex: 9312110595 AE G. All products manufactured and fabricated Please send me full details of the full range of Antex soldering products. in-house Name Contact (0734) 311030 for further details Ian P Kinloch & Company Limited, Address IPK House, 3 Darwin Close, Postcode L_ (Eww 3i MPH Reading, Berks RG2 OTB CIRCLE NO. 150 ON REPLY CARD CIRCLE NO. 152 ON REPLY CARD 352 April 1990 ELECTRONICS WORLD + WIRELESS WORLD With 48 years' experiencerin the design and manufacture of several hundred thousand trarstormers we can supply TRANSFORMERS EX STOCK 12/24V or 12-0-12V 2a12V Secs 30/15V or 15-0-15V 60130V or 30-0-30V AUDIO FREQUENCY TRANSFORMERS IF 24V 12V £ PSP 2 x 15V Tapped Secs 2 0 30V Tapped Secs 0.15 0 03 3 44 1 87 To give: 3, 4, 5, 6, 8, 9, 10, 15, Volts available: 16, 18, 36, 40, I 0 25 0 5 364 t 87 18, 20, 27 309 or 15-0-15V 60V or 20-0-40V or 30-0-30V EVERY TYPE 05 1 436 198 30V 15V £ PSP 60V 30V £ PSP 1 2 608 209 C5 455 181 05 1 672 209 IT! WE MAKE IT! 2 A 4 701 220 1 .t 619 198 1 A 2 1025 220 YOU NAME 3 M 6 1206 236 2 A 1 1001 220 2 M 4 1317 253 4 P 8 1287 242 2 M 1160 242 3 P 6 1905 264 OUR RANGE INCLUDES: - 6 S 12 1562 264 < p I 1384 253 4 S 8 2172 275 Microphone transformers (all types). Microphone Splitter/Combiner transfor- 8 16 1659 3011 5 S 13 1662 274 5 10 '2746 319 I 10 20 2502 352 6 12 1941 291 6 12 31 3 41 mers. Input and Output transformers. Direct Injection transformers for GJitars. 15 30 31 10 363 8 15 25 74 3 02 8 16 44 0432 4 12 Multi -Secondary output transformers. Bridging transformers. Line transformers. I20 40 44 40 4 12 '0 20 29 94 3 24 10 20 51 28 440 Line transformers to B.T. Isolating Test Specification. Tapped impedance natch- 30 60 63 75 a 89 12 24 33 42 3 45 12 24 59 09 5 22 141 83 7341 632 -5 30 3743 401 ing transformers. Gramophone Pickup transformers. Audio Mixing Desk transfor- 20 40 51 10 6 54 96/488 or 36-0-368 (2: 361468 mers (all types). Miniature transformers. Microminiature transformers fo- PCB MAINS ISO LA FORS Secs) 36, 48, 60, 72, 84, 96V or 0 2 36-0-36V or 48-0-48V mounting. Experimental transformers. Ultra low frequency transformers Ultra Pr1120V or 220/240V or I 415/440V.Sec 4408 or 240V or 50/25V or 25-0-25V 2 x 25v 96V 38148V £ PSP linear and other transformers for Valve Amplifiers up to 500 watts. Inductive Loop 110V Centre Tapped Tapped Secs to give: 5, 7 6, 10, 0 5 1 7 16 1 76 transformers. Smoothing Chokes. Filter, nductors, Amplifiers to 100 volt line r VA £ P&P 13, 17, 20,25, 33, 40, 50V or 1 2 1280 2 31 20 8.33 250 20-0-20V or 25-0-25V 2 A 4 2105 291 (from a few watts up to 1,000 watts), 100 volt line transformers to transformers 60 1360 269 50V 251/ £ PSP 3 M 6 2549 302 speakers. Speaker matching transformers (all powers), Column Loud-speaker 100 1587 291 OS 1 591 209 4 P 8 3254 332 transformers up to 300 watts or more. I 200 22 a9 3 52 t A 2 7 19 220 5 S 10 46 21 4 18 250 27 20 363 f M 4 12 81 2 75 6 12 57 87 4 40 We can design for RECORDING QUALITY, STUDIO QUALITY, HI -Fl 500 41 91 4 23 3 P 5 14 82 2 92 8 16 63 12 5 28 QUALITY OR P.A. QUALITY. OUR PRICES ARE HIGHLY COMPETITIVE AND 1000 76 01 533 4 S 6 20 30 3 24 WE SUPPLY LARGE OR SMALL CUANTITIES AND EVEN .S NGLE 1500 96 04 6 54 6 12 25 81 3 45 TOOL TRANSFORMERS 2000 I17 _ 7 ______240-110V Centre tapped TRANSFORMERS. Many standard types are in stock and normal dispatch 3000 165 41 OlA 10 20 43 34 a 41 16Amp Socket Outlets 6000 353.43 OIA 12 24 times are short and sensible. 51 67 5 22 INVERTERS 12/24V DC to 240V AC OUR CLIENTS COVER A LARGE NUMBER OF BROADCASTING AUTOS Sine -wave or Square Wave AUTHORITIES, MIXING DESK MANUFACTURERS, RECORDING STUDIOS, 105, 115, 200. 220, 230, 240V CASED AUTOS For step-up or down 240V Cable Input, 3 -pin 115V CONSTANT VOLTAG HI -Fl ENTHUSIASTS, BAND GROUPS AND PUBLIC ADDRESS FIRMS. VA £ P&P USA Socket Outlet Transformers for Spike -free Export is a speciality and we have overseas clients in the COMMONWEALTH, 80 691 192 VA £ PSP e Mains EEC, USA, MIDDLE EAST, etc. 150 1003 2 09 20 9 95 2 03 250 1225 231 80 1338 Also Valve Mains 6 Output Send for our questionnaire which, w -len completed, enables us b post 350 1405 275 150 1734 Transformers quotations by return. 500 19 05 308 250 21 13 3 1000 34 93 368 500 34 66 390 TA SFORMER WIN011 1500 40 40 4 18 1000 55 65 4 90 SERVICE e Ato 2000 60 41 5 11 2000 88 70 6 16 18KVA 3000 102 72 6 32 3000 124 46 0 A 4000 133 35 CIA TOROIDALS SOWTER 5000 155.28 OlA AVO's 8 MEGGERS Batches Wound to Order I TRANSFORMERS I b 7500 239 70 CIA Full range 30VA to 4KVA 10kVA 283 23 O/A Please add 15's VAT to all items after P&P Send SAE for lists l PO Box 36, Ipswich IP1 2EL, England. PO BOX 70, ILFORD BARRIE ELECTRONICS LTD' Phone: 0473 252794 & 0473 219390 - ESSEX 1G5 OAP TELEPHONE: 01-551 8454 Telex: 987703G Fax: 0473 236188 CIRCLE NO. 154 ON REPLY CARD CIRCLE NO. 153 ON REPLY CARD WE HAVE THE WIDEST CHOICE OF USED OSCILLOSCOPES IN THE COUNTRY SMALL SELECTION ONLY LISTED - EXPORT TRADE AND [1.700 [575 DISCOUNTS C6s0 QUANTITY [oso [400 RING US FOR YOUR REQUIREMENTS WHICH MAY BE IN STOCK [400 [500 Sood state general purpose bandwidth DC to c5so Cossor Oscilloscopes COU150(CT531/3) £150 only [450 35MHZ at 5MV Cm Dual Channe delayed time base protection cover containing polan4ed viewer [300 in lair with [275 and camera adaptor plate probe (1l mains lead Tested condition operating instructions [140 FEW AVAILABLE NO PROTECTIVE COVER BUT MAINS LEAD 1 PROBE £125 [300 [175 Tektronix 475 200Mc s Oscilloscopes tested Iron £400 less attachments to £700 as new o a manual [210 [feo probes etc [150 Telequipment D755 50Mc 5 Oscilloscopes Tested c w 2 Probes £250 £130 casa Marconi TF2002AS AM FM Signal Generator 10Kc s to 72Mc s £85 Tested probe ingt Manual coso ( lob [aso iirra Casa Marconi TF2002B AM -FM Signal Generator 1 01 Mac TF2016A 51g/Gen 1OKht 1 20M s AM 'FM £150 [575 Mac TF2015 Sig/Gen 1OMn: 520Mc s AM FM £250 [300 Mac Ti 131 I Mndu akin Meter AM FM 10OMc s £300 c150 Mac Signal/Source Type 6058B -8 12 5GHz new or used from £450 to £600 [100 :44 Mac Signal/Source Type 6059A - 12 0 18Ghz new Or used horn £450 to C600 ,.. p,a.i ,. ... ' aso HP Power Meter Type 431C to 18Gn2 with C type Head & Waveq..Ide Head £150'o £200 f-111:111818283:01 8 B Plug Ins from 100Mc s to 18Gnt POR [So HP Sweep Oscillators Type 8690A el. HP 8656A Sig/Gen. 1 to 99, O 12500 [5 .. . ,. _ 5 to ,. HP 3325A Synthesiser/Function Generator Brand New C3000 .I [ts Tektronix Mainframes 't ' 3 7633 £300 £500 Various Plug Ins POR [222 Mac TF1245A Circuit Magnification Meter T246 & 1247 Oscillators £10010 £300 t295 1 ' [t09 HP Signal Generators Type , ' br4 618 620 676 628 Frequency from 450Mc s to 219-Its POR .0 'i- M- -, ' OM[r[25 (Pie [7) J --. 1 I, 11N a , .tr-, [135 FxMO for Range As New Ea , 1 . image intensifiers Tripod Fitting _ong Night Viewing £3000 : I C ri if.. ) . . [rre -J.'Y: , - ONLY [301PtP[7) L [110 intensifier Tubes £50 to £250 L<', d Depending on Grade First Gen XX1060 v09 From I lot, v0o Thermal imaging Equipment HIT letlnlhon £2500 [150 Clark Air Operated Heavy Duty Masts POR [ISO loo4 , [39.50 All items are bought direct from H M Government teing surplus equipment price is ex works S A E for [33 50 [750 ' , [3.00 ea enquiries Phone for appointment for demonstralio t of any items aso avaoaod4y or price :hange V A T [soó [1 1 and carriage extra JOHNS RADIO, WHITEHALL WORKS, g WHITEHALL ROAD EAST, BIRKENSHAW, This is a very small sample of mock. SAE or telephone for LIST of OVER 700 ITEMS. Please check availability BRADFORD B011 2ER. TEL NO. (0214) 684001. FAX: 651160 before ordering. CARRIAGE all eons E16. VAT to be added to toter of goods and carriage. WANTED: REDUNDANT TEST EQUIPMENT - VALVES - PLUGS - SOCKETS - SYNCHROS ETC. RECEIVING AND TRANSMITTING EQUIPMENT- GENERAL ELECTRONIC EQUIPMENT STEWART OF READING JOHNS RADIO REQUIRE A VERSATILE ENGINEER WHO CAN REPAIR THE ABOVE ITEMS IN 110 WYKEHAM ROAD, READING, BERKS RG6 1PL VISA OUR ADVERT ... PLEASE RING. (PROBABLY MORE SUITABLE TO A MATURE PERSON Tel: 0734 68041 Fax: 0734 351696 REQUIRING TO GET OUT OF THE RAT RACE.) Cellars wnl, only ran, to 5 30pm MON FRI iUNTIL 8pm THURSI CIRCLE NO. 755 ON REPLY CARD CIRCLE NO. 156 ON REPLY CARD April 1991) ELECTRONICS WORLD+WIRELESS WORLD 353 ---1 1 -71-., . 7-"9 'I 1 1 m- t 1 C - lillail S I. o¡ ' ,s.-.1 ,._ - 1111111.1 . ,a - cl "pep ` 11 ,,.,.__ does not even employ a bought -in machine for final test is even less likely to be able to justify an MDA for fault diagnosis. Apart from the significant initial cost, an MDA usually requires expensive custom bed -of -nails fixtures and considerable programming effort for each type of board tested. In a diagnostic role, an MDA will only receive hoards that fail the final test, so even if production volumes are high. the MDA may only be justified if quality is poor. As quality improves and more hoards pass final test first time, the MDA becomes less economic to run. Manual test If the automated approach is beyond their reach, many companies entrust the diagnosis of hoard faults to engineers with general-purpose instruments such as oscilloscopes, logic probes and Diagnosing multimeters. But this method also has its drawbacks: manual testing is time con- suming and requires qualified, experi- enced staff. Also. it is often difficult to exercise a board's logic whilst perform- board faults ing the tests; if a hoard is suspected to have a fault in its floppy -disk controller section. for example. the engineer Ian Fletcher describes an instrument for would somehow need to make the hoard perform continuous reads and testing boards in low -volume production, writes to disk. It is not feasible to exer- cise all the possible logic states. so faults which needs no programming or expensive can he missed. test fixtures Manufacturers having a relatively low number of boards to rework need some- thing between the fully automated The performance and The first option may appear attractive MDA and the manual troubleshooting capability needed by modern when the product is relatively simple approaches: a method that provides a automatic test equipment has and cheap to discard hut, even if yields well-defined test procedure with some a tendency to put it beyond are high. it is generally not to he recom- form of automation, that does not tie up the reach of smaller -volume mended. 13v disposing of faulty hoards. highly paid engineers and that offers equipment producers who do not have the manufacturer gains \ery little know- low initial and running costs. the throughput to justify the capital ledge of why they failed - information investment and running costs. which is vitally important if the produc- Many smaller companies use little or tion process is to he improved and In -circuit testing no bought -in ATE. Often. their hoards quality maintained. If the failure rate on A solution to these conflicting require- pass from the production line to a final high -value hoards suddenly increases ments has emerged with the in -circuit "hot bed" or functional system test. due to a recurring fault, discarding them digital IC tester. intended primarily for With a little effort and ingenuity. this becomes too expensive to contemplate service and repair departments. approach can offer effective quality and rework becomes necessary. whereby the operator simply attaches a control - without recourse to ATE. test clip to each device in turn. The func- tionality of each IC is automatically The automated approach checked by the equipment and any Repair or discard In recent years. manufacturing defects faults' devices reported. There still remains the problem of what analysers (N DAs) have become a pop- It may seem unlikely that this type of to do with hoards that fail the final test. ular way to track down hoard faults. machine would be appropriate for the Since it is usually impractical to build Although these machines are less testing of newly manufactured hoards, extensive diagnostics into the final test. expensive than full-blown in -circuit since the nature of faults found in them the smaller company is faced with a sim- testers. they must still he fed by con- differs from that of faults in hoards that ple choice -either throw the had hoards siderable numbers of boards to justify have spent time in the field, which usu- away or undertake a separate procedure their cost. ally stiffer from tailed ICs and other to locate the fault and repair it. The lower -volume producer who component faults. If goods -inward tests 354 ELECTRONICS \VORLD+WIRELESS WORLD April 1990 have been performed, less than 5% of a single clip can be used to test a whole REMOTE COMPUTER faults on new boards are due to defec- board. OR SERAL PRINTER tive components; most faults are manu- The clip is connected to tri-state digi PAPA< EXTERNAL facturing defects such as wrongly inser- tal output drivers within the tester, PROMER MONITOR ted components, solder bridges, dry which are capable of sinking and sourc- joints, broken tracks and holes which ing sufficient current momentarily to been through back the inputs to the device have not plated properly. -drive SERLA SERTAL PMAüEL INTEGRAL NTT GRAL IRS NTERFACE MTERFACE 2321 KEYPAD MONITOR Simply checking a board's ICs will not under test and effectively isolate it from INTERFACE detect these major sources of board the circuit. Minimum currents and times failure. Fortunately. however, it is pos- are used to do this, to prevent any pos- FLOMY CENTRAL YKIE0 sible to extend the in -circuit IC test sibility of damage to other devices CASK PROCESSOR INTERLACE approach. since the clip which fits through overheating. around each IC can be made to look Once the tester has determined the TIST outwards at the board as well as inwards position of the device in the test clip, it PRE DRIVERS/ !WETS at the device itself. checks that both the supply and ground REEENERS By examining the connections to each rails are present and within specifica- component in turn, the tester can build tion. If not, the test is aborted and an up a complete view of the board's inter- appropriate message displayed. connection and show discrepancies The tester continues to analyse the IC UNDER TEST EXTERNAL between the observed and expected IC's connection in the circuit, checking XElOMD connections, giving a good indication of whether any of the device inputs are not where manufacturing defects lie. being driven or any test -clip pins are Electronics produces the open -circuit. Pins shorted to the supply POwEP ABI DDS- TEST 40XP IC tester with this added rail or linked to another pin on the CLIP capability, which can locate faults on a device are detected. PCB UNDER TEST range of hoard types and is low enough in cost to bring it within reach of lower - System diagram of ABI's DDS -40 series, volume board makers. Automatic circuit which tests ICs or complete boards. Dividing the test into smaller tasks compensation means that only a small number of chan- Such connections pose problems for tra- nels is required, which makes the instru- ditional ATE. since they prohibit the Power -off testing ment relatively inexpensive. A test clip application of certain test patterns to To meet the special needs of manufac- that fastens onto standard dual -in -line the device. For example. a two -input turing defects testing on small to packages is often all that is needed to Nand gate connected as an inverter with medium volume assembly lines, the connect to the board - no costly fixtures both inputs tied together cannot have tester can make tests which identify are required. The DDS-40XP can func- different logic levels applied to its shorts, links and floating pins without tionally test the components on the inputs. Conventional testers need such the hoard being powered. thereby find- board, a capability beyond the conven- information programmed into them, ing faults without risking further tional MDA. This facility, which can be but the DDS-40XP automatically com- damage if the board has previously run whilst performing a manufacturing pensates for links and shorts. It does, shown signs of overheating. defects test with very little speed however, also have the intelligence to Testing with no power on the board penalty, will pick up the odd faulty com- recognise when the configuration does also checks on any type of dual in -line ponent that has found its way into pro- not make sense - an IC output con- device, not just ICs: op -amps. compara- duction and is also useful for locating nected to ground. for example - and will tors, linear ICs and even relays and faults such as the insertion of a wrong indicate the fact. This automatic com- opto -isolators can all he probed in the component which an MDA might miss. pensation removes the need for any saute way as digital components.. Tests for a comprehensive range of SSI. form of circuit configuration program- To keep the operator's tasks to a MS1. memory and peripheral devices ming. greatly reducing the skill and time minimum, the DDS-40XP has "save are held in a library within the tester and demanded of the operator to set up the and compare" facilities. which allow called up as required. test. details of a known good board to be Finally, devices are functionally stored on a floppy disk, using the test- tested. Combinational ICs such as er's disk drive. The system compares gates, buffers and decoders can simply the results with the stored data and Semi -automated test be checked against their truth tables. highlights any differences. When diagnosing faults with this tester, Sequential parts such as flip-flops, coun- To sum up, the instrument offers a the operator first connects the board ters and registers are subjected to tests cheaper alternative to the MDA. with under test to the machines 5V supply. which exercise them through all their the advantage that it is equally useful in He then attaches a test clip to each possible states, the tester issuing such a service department. device, in any sequence: the tester auto- pulses as clock, clear and preset as matically positions the clip, so that any appropriate. The instrument will handle The DDS-40XP is obtainable at £4950 size of clip can be placed over the IC in 40 -pin devices such as the 6800. Z80 and (exc. VAT) from any, position, provided all the pins are 8085 microprocessors. As well as being ABI Electronics Ltd, covered. This allows one clip size to be displayed on the screen. test results can Mason Way, used for ICs with various numbers of be sent via built-in RS232 or Centronics Platts Common Industrial Park, pins, wherever the operator happens to ports to a printer or to a computer for Barnsley, fasten it on. even if it is reversed. Often. storage and analysis. South Yorkshire S74 9TG April 1990 ELECTRONICS WORLD + WIRELESS WORLD 355 S SUBSCRIPTION ORDER FORM 9C Cut out and return to ELECTRONICS rf ELECTRONICS WORLD + WIRELESS WORLD, Subscription 0 Manager, Reed Business Publishing 4 Group, Stuart House, Perrymount Road, 4,14, WORLD Haywards Heath, Sussex RH16 3BR. + WIRELESS WORLD Subscribe Now! We are pleased to offer you 22% off the current UK Please send me ELECTRONICS WORLD + WIRELESS WORLD for 12 months. subscription price of £30. This means you only I would like to take advantage of your special three pay £23.40 for 12 issues. We also pay the postage year rate and subscribe for 36 months. 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Full page £2311 Y page £1271 1/a page £693 Full colour £400 2nd colour £275 Cheques and Postal Orders payable to REED BUSINESS PUBLISHING GROUP LTD and crossed. ~~~~ titi tri DEPARTMENT OF TRADE AND INDUSTRY OPPORTUNITIES IN TELECOMMUNICATIONS BALDOCK INTERNATIONAL MONITORING STATION BALDOCK, HERTS TELECOMMUNICATIONS TECHNICAL OFFICERS ASSISTANT TELECOMMUNICATIONS TECHNICAL OFFICERS Up to £14,905 Challenging and interesting opportunities have arisen at this modern well equipped radio station which is part of the Radiocommunications Division of the DTI. You will join a technical team working in the frequency range 9kHz to 18 GHz for fixed, mobile and satellite service, maintaining systems and using them for measuring and monitoring. One post will involve travel throughout the UK. You will need 2 years' radio/telecommunications experience and be qualified to BTEC standard or have an equivalent qualification. Salary up to £14,905 with further increments, depending on performance, up to £16,125. 20% extra where shift work is involved. RELOCATION ASSISTANCE UP TO £5000 MAY BE AVAILABLE. The Station is set in the North Hertfordshire countryside with easy access to Cambridge, Peterborough and London to give a wide range of housing and leisure choices. For further details and an application form (to be returned by 20 April 1990) write to Civil Service Commission, Alencon Link, Basingstoke, Hants RG21 1JB, or telephone Basingstoke (0256) 468551 (answering service operates outside office hours). Please quote ref: T/8305. The Civil Service is an equal opportunity employer the departdii mein for Enterprise April 1990 ELECTRONICS WORLD + WIRELESS WORLD 357 Papua New Guinea Department of Minerals & Energy Professional Audio Geological Survey Senior Technical Officer Grade 2 (Position GSG 37) Solid State Logic is the world leader in professional Duties: Control technical engineering activities at the Geophysical Obser- sound mixing consoles and studio automation vatory, including the design, installation and maintenance of electronic systems, with products installed in major recording, equipment, magnetic and seismic monitoring systems and computers. Training of subordinate National technical staff. radio, television and film studios world-wide. Qualifications: An approved Diploma or Degree and a minimum 5 years professional experience. We're looking for an Terms of Contract: Three year contract, average annual approximate cash value of the contract K20,000. Nominal housing rental, 6 weeks annual leave, mid -contract leave fare education subsidies 12 children), recruit- ment and repatriation fares KIPNG11 equals U.K. f0.60 (March 1990). Analogue Audio Design Engineer Applications close May 15, 1990. Apply with CV to: Chief Government Geologist, Geological Survey of PNG, P.O. Box 778, Port Moresby, Papua New to assist Guinea. Enquiries: Ph.: (675) with the continuing development of our 214500, FAX (675) 213976. extensive range of analogue mixing consoles. We'd like to hear from you if you can offer: a minimum of two year's experience in the Well Rounded Engineer design of professional audio equipment Working foreman type position Minimum of 5 years related experience an interest in music and audio Hands on experience required Opportunities for advancement and profit sharing A formal academic qualification would be an NORTHERN COMMUNICATION & NAVIGATION SYSTEMS LTD advantage. PO Box 2317 Yellowknife N.W.T. Canada X1A 2P7 Salary will be in the range £12-15K. Telephone: 010 1403 873 3953 i Fax: 010 1403 920 4282 If you'd like to know more, please contact Ron Pender or Stewart Taylor on 0865 842300, or send your CV to REPRINTS Solid State Logic Begbroke Oxford OX5 1 RU IF YOU ARE INTERESTED IN A @@@@@@@@@@@@@ PARTICULAR ARTICLE/SPECIAL RF & MICROWAVE! FEATURE OR ADVERTISEMENT IN 1990 Design & Test Engineers seeking OUR JOURNAL WHY NOT TAKE I top positions, from satcomms to CAREER CT2 should contact the specialists I ADVANTAGE OF OUR REPRINT DECISION GARIBALDI RECRUITMENT SERVICE. 0494 773918 1 YEAR 160 Bellingdon Road Chesham HP5 2HF REPRINTS CAN BE OBTAINED AT Irrespective of your career objectives - financial or geo- A REASONABLE COST, TO YOUR graphical - let Cadmus put direction into your search and OWN INDIVIDUAL eliminate the stress. If you are TO a qualified engineer, you may SPECIFICATIONS PROVIDING AN be eligible for inclusion in our ATTRACTIVE monthly register which will ADVERTISE AND VALUABLE give you discrete access to over 3,000 UK companies. ADDITION TO YOUR OWN Phone 0603 761220 (24 hrs) YOUR PROMOTIONAL MATERIAL. for a registration form or send your C.V. together with your career objectives to: VACANCIES FOR EXAMPLE, A TWO PAGE PLEASE CALL ARTICLE CAN BE REPRODUCED AS A FOUR CLASSIFIED PAGE FOLDER WITH ADDITIONAL WORDING ON THE DEPARTMENT FRONT PAGE AS AN INTRODUCTION. `ADMLIS ON PERSONNEL LIMITED Freepost. Sackvdle Place FOR FURTHER DETAILS CONTACT: 44-48 Magdalen Street Norwich NR3 I BR 01-661 8640 CLARE HAMPTON ON 01-661 8672 ffiffiffifflaaWEEffifflEE 358 April 1990 ELECTRONICS WORLD + WIRELESS WORLD CLASSIFIED 01-661 8640 CLASSIFIED DISPLAY: £29 per single column centimetre (min 3cm). LINE ADVERTISEMENTS (run on): £6.00 per line, minimum £48 (pre payable). (Please add on 15% V.A.T. for prepaid advertisements). BOX NUMBERS: £15.00 extra. (Replies should be addressed to the box number in the advertisement, Go Quadrant House, The Quadrant, Sutton, Surrey SM2 5AS). Cheques and Postal Orders payable to REED BUSINESS PUBLISHING GROUP LTD and crossed. ARTICLES FOR SALE TO MANUFACTURERS, WHOLESALERS, BULK BUYERS, ETC. Cooke International LARGE QUANTITIES OF RADIO, TV AND USED ELECTRONIC TEST INSTRUMENTS FOR DISPOSAL Racal 9081 Synthesized Signal Generator 5-520MHz f950.00 ELECTRONIC COMPONENTS M.P. 8614A Signal Generator 0.8-2.4GHz C1250.00 SEMICONDUCTORS, all 'ypes. INTEGRATED CIRCUITS. TRANSISTORS. DIODES. R & S SMC1 Signal Generator 4.8-12GHz (as new) £1500.00 RECTIFIERS. THYRISTORS. etc RESISTORS, C, F, M/F. W/W, etc CAPACITORS. Racal 9061/62 Synthesized Signal Generator 100kHz-160MHz f350.00 SILVER MICA. POLYSTYRENE. C280, C296, DISC CERAMICS. PLATE CERAMICS, etc M.P. 612A UHF Signal Generator 450MHz-1.2GHz C180.00 M.P. 608C or 608D VHF Signal Generator 10-420MHz C120.00 ELECTROLYTIC CONDENSERS. SPEAKERS. CONNECTING WIRE. CABLES. SCREENED M.P. 5354A Timer Counter with 5353A, 11 digits 500MHz, HPIB [2200.00 WIRE. SCREWS, NUTS. CHOKES. TRANSFORMERS. etc ALL AT KNOCKOUT PRICES Systron Donner 6152 Timer Counter 512MHz C275.00 Come and pay us a visit ALADDIN'S CAVE PLEASE APPLY FOR FURTHER DETAILS & STOCK LISTS SURPLUS STOCKS ALWAYS WANTED TO PURCHASE TELEPHONE: 445 0749/445 2713 R. HENSON LTD Contact: Cooke International, Unit Four, Fordingbridge Site, Main Road, Barnham, Bognor Regis, West Sussex P022 OEB 21 Lodge Lane, North Finchley, London N12. ,. rron Tel: 0243 545111, 2. Fax: 0243 542457 (5 r1,,, fry . 1 , 1', H. I alt SINGLE EIROCARD MICRO-CONTROLLER Field Electric Ltd. t. 01 953 6009 3Shem7y POad. Wire -wrap area for your interface. weal EASY -PC* QV k11 mw H.ns W061AA fax 01 2u-6375 0/116 640328 small -batch /prototype /one-off. RS232. 32 I 'O.4 A/D. 3 Timers. 6502 £28 +V Al Telephone or S.A.E. for new stock list for Monitors: Disk Drives: Compal. Low power D.C., Batt. ready run Inc. Hard Disk Drives: Keyboards: Computers: Printers: Test & Complete package lo DRILL -TAPE UTILITY Measurement Equipment: Diecast Ali Boxes: Fans: Power monitor. asssembler and full docu- mentation - for only f99. Supplies: Telephone Equipment: Audio Equipment: Transformers: Spantec Designs Ltd .IFS-DRII.I, Microwave Equipment. 43 Longshot Lane, Bracknell, Beaks. Tel: 0344 485854 .IFS SYSTEMS, Special offers BJARKESVE,I 13, Philips Pedestal (Swivel & Tilt) FOR8833 Monitor £8.50 inc c/p new and boxed DK-31)1)0 EI.SINORE, Philips BM7502 green screen monitors DENMARK High res: (920 pixel). Wide bandwidth (20MHz), 240VAC composite Tel: 010-45-10.4115 F..: 010-49-261639 video and audio £25.00 c/p 6-00 ',i prnrlurtof Number One .51,terrn lurl Frequency We would like the opportunity to tender for surplus equipment Intermodulation FIGOLLEDGEI OnKialone,. e, wet- ,rhI,p ., pa t 1,-h, .Pr'.N. ur', mr, nh i , ,, Pr - I. A ,es,e1..1 .,, e,. Aul , .,.T , , a ', Areess Ame, D,',.,t N.a ,'ep,nt We...pnlr,k'ri,n,v'.,nn some la i .pmen' n,e i al awl anna Software for Sale ELECTRONIC_Sj- erynp-oen' :n.,rn mon ,han rt .r,.wn m n.. ad nlr,asr'nnu Calculates intermodulation products 2 to between 1Hz and 999GHz, for 50 CRYSTALS OSCILLA- IBM PC QUARTZ radio transmitters. Runs on TORS AND FILTERS of all types. VALVES FOR AUDIO, INDUSTRY and or compatible with 360k drive Large Mocks of standard items. Spe- RECEIVING & TRANSMITTING 640 kRAM. cials supplied to order. Personal and RARE AND OBSOLETE TYPES A SPECIALITY! Price 430.00 dollars (Canadian). export orders welcomed - SAE for lists ONE MILLION VALVES IN STOCK Write for a free demonstration dis- please. OEM support thru: design SPECIAL PRICES FOR WHOLESALE QUANTITIES kette. B. Chomycz, 2023 Donald advice, prototype quantities. produc- ORDERS FROM GVT DEPTS, PLC's, OVERSEAS ETC. WELCOME Street, Thunder Bay, Ontario, tion schedules. Golledge Electronics. ALSO CRT, I.Cs, KLYSTRONS, MAGNETRONS, Canada, P7E 5W9. Merriott. Somerset TA16 5NS. Tel: TRANSISTORS, USA VALVES. 04110 73718. 121721 FAX/PHONE FOR IMMEDIATE QUOTE! BILLINGTON VALVES ARTICLES WANTED 39 Highlands Road. Horsham. Sussex RH13 5LS tUK) Callers by appointment only. Mon -Fri 9am-5 33p -n. Visa& Access accepted . Phone 0403 210729. Fax 0403 40214 Telex 87271. WANTED FOR SALE Receivers, Transmitters, Test Equipment, Components, TEST EQUIPMENT Cable and Electronic .Scrap. Boxes, PCB's, Plugs and 30 Days Guarantee. Please add VAT. Check availability & Carriage costs. ~con, 2600S millwoltmeter AF IMV 300V FSD C30 Scokets, Computers, Edge Connectors. Maroon, 144H es new from C45 Wayne Kerr AF Generator 10Hz - 120KHz C30 Bradley 471C Test Meter C40 TOP PRICES PAID FOR ALL TYPES OF ELECTRONICS EQUIPMENT Mercon, HP Test Set 2603 175 Tektronix 6474 Dual Trace Scope (Alt mods/ C250 Marconi Generator 2002AS 10KHa 88MHa AM FM 6140 A.R. Sinclair, Electronics, Stockholders, Marconi Generator 20015 10MHz 510MHz AM FM C375 Teleguipment Dual Trace 755 Scope 50MHz £250 2 Normans Lane, Rabley Heath, Welwyn, Herts Philips PM3217 Dual Trace 50MHz Scope C325 Cossor CDU150 Dual Trace 35MHz Scope £140 Telephone: 0438 812 193. D B Scope SM 1113DB/18MHz £120 AL6 9T0. Professional Colour Monitors from 185 VDUS with keyboard from 050 Mobile: 0860 214302. Fax: 0438 812 387 750 Printers from £45 Various systems from 64k twin floopy CPM discs working 180 upwards Various AVOS from C25 and Bridge Megge,s from C50. AVOB complete from C35 MKS 075 A. WOOD NORTH WEST 94 WORSLEY ROAD, FARNWORTH STEWART OF READING TEL: BOLTON (0204) 71795 110 WYKEHAM ROAD, TRANSIS- WANTED: VALVES READING RG6 1 PL. TORS I.Cs (especially types KT66. TEL: 0734 68041. KT88 PX4. PX25(. Also plugs, sockets FAX: 0734 351696 and complete factory clearance. if PLEASE MENTION ELECTRONICS possible, send lkritten list for offer by TOP PRICES PAID FOR ALL return. Billington Valves, phone: 0403 TYPES OF SURPLUS TEST WORLD + WIRELESS WORLD 210729. Fax: 0403 40214. See adjoining EQUIPMENT, COMPUTER advert. EQUIPMENT, COMPONENTS WHEN REPLYING TO ADVERTS etc. ANY QUANTITY. 103 720K 3.5 INCH DISK DRIVE LASER PRINTERS NEW LOW PRICE TO CLEAR WAREHOUSE 8 page nun ( anon I1'118 II £799 Brother Ill So £849 12 page nun Data Products I. DP12 (ex den, ) £850 (car 125) made, modern low Japanese FAST MATRIX PRINTER component cast chassis drive Surface mount design with industry standard I at r 4542 m,r,unwu of 'MU 1.I% Maile hi 'ugh ,land,ud for heavy duty use COmpaCt interlace Removed from almost new ,lunhro desktop model (only 23 inches viol') Ideal any serious commercial application systems, these are top quality drives in £349.00 (can £25) excellent condition Boxed and with a full 12 INCH FAMOUS NAME COLOUR MONITORS six month guarantee 80 track double (Duality analogue RGB input very high de'nldion (80 column 0 28 dot pitch). tilt swivel base sided 1 megabyte unformatted £34.50 suitable for Amiga BBC etc £119.50 (carr £6 50) (carr £3) £30 ten or more Cradle o fit drive in a 5 25" slot e g IBM PC £4.95 (carr f 1 00 tree with drive) Power and data connectors to suit £0 99p (carr 'ree) Box of 'en 3 5" discs HITACHI COLOUR MONITORS £9.95 (can ht adaptors saves cor rec'ors £3.49 'ree) £1) Easy changtng (carr CM1473ME 14 inch multi synch £279 CM1473A 14 inch VGA standard £239 CM1686A 16" NB Drives work with virtually all computers including Amstrads IBM XT and AT compatibles ultra high resolution in two CAD 'requencies 48 KHz £325 64 KHz £395 (carr £25) BBC's etc no! Ataras and Amigas Special CM2086A I E 20" ultra high resolution CAD 48 KHz £495 (carr £35) easy' : kit available 'or An s'rad 1512/1640 IBM XT and AT RACAL V22 MODEM MPS1222 theta.,' I adipro, I hard £8.49 Mcroprocessof based modem providing full duplex communication at 1200 600 and 300 5.25DISK DRIVES baud to the CCITT V22 standard I eatures include Can be used on standard phone line Standardand IBM 3ó0K half height chassis drive thou e of (PSTN) and private cticun (PC) Auto answer but needs 'elephone to dial 1200. 600 and black or cream bezel new £39.95 ex egwpmer £29.95 high qualify loop (carr £3 50) 300 baud Very construction BT Approved Sel' jests and tests (V54) / Comprehensive manual included Uncased card £19.95 seven cards ir rack £195 (carr or 1 2 Meg IBM AT style drive £49.95 (can £3 50) C3 50, seven f 15) HARD DISK DRIVES AND HARDCARDS . 3.5 inch hall -height hardcards and drives WESTINGHOUSE WPC5O0 MODEM CARD To fit IBM PC 20 MByte IK,ncera Lapine and 'Pan) hardcards £149 30 MByte equivalents £179, 53 inside style and communicate at 1200 Baud 1200 75 Baud or 300 Baud. BT MBy:e Rodin e R3065 £249 (carr £5 00) approved £24.95 5.25 inch halt -height hard drives POWER SUPPLIES Large range of drives (Seagate Rodime Mirisrribe Microscience. CDC and Priam) 'rom Farnell N1 KO ,sell 160 Watt PSU -5V 20A 12V at 2A -12V a: 2A r24V at 5A and 20 MByte through 'o 178 MByte 'tom £109 sae for list and prices (carr £5 00) -5V a: IA ver, high quality British um* £26.95 (carr £3) ASTEC AC9231 cased 50 Watt HDD i able se' 'or 'he above £5.00 PSU .5V a: 6A -k 12V at 2 5A 5V at 0 SA I' , a') and 12V a' 0 5A £12.95 (carr £3) HARD DISK DRIVE CONTROLLER CARDS THEATRE LIGHTING CONTROL ; V i ! r J .T br lb ir 'r £37.50 AT Controller cards 'rom £59.95 Rar k S' aid Compact I"3 -k well known semi portable memory system to control 120 IBM COMPATIBLE XT MOTHERBOARDS, CARDS, CASES, etc. char r el .r exceller ,o lilt, r with manual £699 Rank strand 17.45K dimmer racks in £450 or 10 MIIz 8088 'urn, t fi 8 e.pansion slo's legal trios 8087 socks £64.95 (carr £4) cabirels each £1275'uí 3 K for free) I for 640 RAM above £49.95 (Can Multi O h' and XT systen bud rg parallel SOUND EQUIPMENT all second-hand pon, serial port. real n ' _' ick floppy disc emir- ,er and game port £34.50 (can £2 50) Speakers. amps mikes etc regularly in stock please ring for current details Studio XT case complete with 150 wa:: power supply £64.95 (carr £6 50) 101 key IBM speakers expected in soon compatible keyboard AT or XT £29.95 (can C3 501 I iyundi mono graphics card £19.95 (carr £2) STOP PRESS - AT SYSTEMS EXPECTED SOON Quality VGA card 200x600. full 16 bit £127.50 (can f2 50) Selection o' other network 12 MHz. 1 MBy:e RAM 1 2 MBy:e floppy drive etc POA video cards SAE for list DAISYWHEEL PRINTER - NEW PRICE TO CLEAR N.B. Olivetti DY200 Modern o'hce quality, bidirectional daisywheel printer Complete with * VAT and carriage must be added to a// items. manual daisywheel. ribbon and srandard Cenronics interlace Prints at 25 cps variable * Everything new unless stated otherwise. pitch 132 charac'ers in 12 pitch propor'voral spacirg Full IBM and Diablo emulations £89.50 Iran f6 50) Carbor ribbors £2.79 eat h (carr 75p) £2.39 each for ten or more * Access and Visa telephone service. (car C2 50) Visa & Access Matmos Ltd., Unit 11, Tne Enterprise Park, Lewes Road, Line/held, VISA accepted 24 hour West Sussex RH16 2LX. 101 phone service raotmos Telephone: (04447) 2091 and (04447) 3830 Fax: (04447) 4258 CIRCLE NO. 158 ON REPLY CARD EX TO ADVERTISERS Appointments Vacant Advertisement appear on pages 357-358 PAGE PAGE PAGE ABI Electronics OBC G H Systems 277 P M Components 131 Airlink Transformers 337 I R Group 266 Polaron Controls 273 Anchor Surplus 350 ICOM (UK) 129 R I lesson 308 Audio Electronics 307 Imperial College 120 Rae(lek Electronics Co .... 285 Barde Electronics 353 Integrated Measurement Ralfe Electronics 289 Bite Computers 319 Systems 313 Reed Exhibition Blue Chip Technology 271 Integrex IFC Company IBC Cadsoft (UK) 277 J A V Electronics 308 Research Communications .275 Carston Electronics 279 Johns Radio 153 Sherwood Data Systems ...279 Clark Masts Kestrel Electronic Sowter Transformers 353 (Technical Services) 350 Components 129 Stewart of Reading 353 Colomor Electronics 137 L J Technical Systems 119 Test Equipment & Design Equipment Sales ... 329 Lab -Volt (UK) 289 P(' Cards 337 Diamond Point Langrex Supplies 150 Those Engineers 307 International 319 MOP Electronics 285 Thurlhy Thandar 271,300 Display Electronics 335 Mat mos 360 Tsien (UK) 285 Elect royal tie 137 National Instruments 290 Waveband Electronics 329 Flight Electronics .. 269.31)1,308 Number One Systems 325 OVERSEAS ADVERTISEMENT AGENTS France and Belgium: Pierre Mussard, 18-20 Place de la Madelame, Paris 75008 United States of America: Jay f cinman. Reed Business Lid . 205 East 42nd Street. New Yo& NY 10017 - Telephone (212) 867 2080 - Telex 23827 Printed in Great Britain by Carlisle Web Offset. Caxton Road. Newtown 1 rading lucrare. Carlisle. Cumbria CA2 7NR. and typeset hr PPC Limited. Leniherhead. Surrey KT22 71.A. for the proprietors. Reed Business Publishing l.id.Quadrant 1 louse. The Quadrant . Sutton. Surrey S\L 5AS. © Reed Business Puhtiching Ltd 15X1. Electronics and tl'irelen.. World can he obtained from the following: AUSTRAL'y and NEW ZETA 1 AND: Gordon n Gmch Ltd. INDIA: A.11. Wheeler ó Co. CANADA- l'he Wm Dawson Subscription Sea ice Ltd . Gordon k Gatch Ltd. SOUTt 1 AFRICA: Central New c Agency LW: William Dawson Is Sons (S.A 1 I td LINITLD SI A II:S: Worldwide Media Services Inc.. 115 Last 23rd Street. Nlu\V YORK. N.Y. 1101111. LISA. /:!,' rnnirf iC II9n/err World 55 95 (74513). 360 ELECTRONICS WORLD+ WIRELESS WORLD April 1990 EFFICIENCY ne w developments CHOICE update BUS1 For business benefits - the more you look, the more you'll find. At COMMUNICATIONS 90 you COMMUNICATIONS explanations and answers - from the can find practical solutions to best in the industry, all conveniently 111 1111111j1 virtually any. communications need. Ili located under one roof, and against For international coverage, the background of the liberalised broad product range and depth of Willi UK telecoms environment. choice in every sector, there's no With so much to discover, plan 1111111 - show to rival it in the 1. K. j111 your visit in advance. It should he evident, with over Send for the Visitor 400 exhibitors from far and wide, Infi-rmaticn Pack which includes a profile, travel and that COMMUNICATIONS 90 syill he a THE EXHIBITION full product matchless opportunity to assess and accommodation arrangements and compare the latest products and 24-27 APRIL 1990 details of the top level conference, services which can benefit the NATIONAL EXHIBITION CENTRE. BIRMINGHAM ENGLAND product trails and clinics - all of efficiency and profitability of any which make G).\1MCNIC.ATIt)NS so organisation. TENTH IN THE SERIES much more than an exhibition. There's nothing obscure about So dcn't ponder the problem. the success of CO.\1.\1!'N IC;VI'IONS. TELECOMMUNICATIONS. RADIO. Diary your visit to It provides hands-on experience, CABLE SATELLITE & INFORMATION TECHNOLOGY CO\1.\1!'N IC.VI'IONS 90 now. MAP CAI - IMR- BSC1- - PSTN - - ITU - - PTT - - !SON - - PCN - -IBCN-- DP/ASS --EDT--OBS--SONET-- IAN --ONP-- PAD --X25--MONS-- [VACS --SSSO--CT2-- PCB -- BERT --DEMS-- -- Please tick YES, please send me the COMMUNICATIONS90 Visitor Information Pack For the complete Visitor Informatics Pack including Please forward details of the conference when available. Registration Ticker omplete coupon and return hr the POSITION NAME organiser, CTAMureCAtiONS 90 ADDRESS ORGANISATION Promotional Department 1251 2-5 Alston Road, Pattinson North, Washington, Tyne & Wear NE38 80A POSTCOME COUNTRY England RBWt Telephone 091-416 4570 PHONE FAX CIRCLE NO. 1.1.3 ON REPLY CARL) l' la 9r y t -¡-. L, ` ,.a? - ,r L\ 71 1 j;. rIt`s Y T . Y: o'. \ 5 \ \ mr.ri i 11 ./..... ^mtr, 1 1° ueP .' :rrrr iCri 5rrr ..rir4º',°r1Í2rb .'áI,' /'11 r . f Í'Asa, g9;1. : , rrhr,. r. . ... Affordable, standalone, PCB fault -diagnosis equipment. 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