BROTHER SCIENCE Lightning and the ATCH Ionosphere ELECTRONIC

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OCTOBER 1989 £1.95 .o

VANDELBROT Fractals, chaos and computers i BIG BROTHER SCIENCE Lightning and the ATCH ionosphere ELECTRONIC

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CIRCLE NO. 1 ON REP! 8 CARD CONTENTS

OCTOBER 1989 VOLUME 95 NUMBER 1644

Lightning strikes. Magnetoresistive sensors. ,at. rv 946 Thunderstorms are a voltage 1010 There are more ways to r stabilizer between the ionosphere and measure magnetic flux than Hall effect Earth's surface, says Anthony and inductive loops. Magnetoresistivity Hopwood. provides a useful alternative.

Fractals, chaos and Passive optical networks. The x 3!1r -.-1110r-,. =ºo 957 computing. A fashionable 1013 use of copper in public branch of mathematics may yield switched network wiring may he a answers to important questions, thing of the past. Optical telecomms , : - - _ - hut is it art? may provide a high tech alternative. CER.N's super collider - all 27km of it - is already producing a new view of Stepping on the GaAs. SPECIAL FEATURE fundamental matter. Even bigger 984 Microwave integrated circuit machines are being planned, page 944. technology is pushing the limits of high frequency performance. Fred Myers of Plessey's Caswell research facility next issue defines the limits.

Review - ECA-2 and PSpice. 989 Simulating a circuit on a PC can replace weeks of costly building and testing. We present a review of two leading software packages. ó I spy. Lee Tracey acts as a quartermaster and adviser to Sensors & Systems papers. Western security services. He has also 1006 This year's conference on worked as a field officer in our own transducer and systems technology Government agencies. He gives a offers < particularly rich choice of personal zccount of the technology subject matter. We present highlights used in professional electronic from the presentations. surveillance.

REGULARS

939 Comment. Green light for 1015 Pioneers. Léon Charles Thévenin electronics, a sensible alternative gave. the world a theorem. His to defence spending. paper "Extension of Ohm's Law to was 941 Research Notes. Micron -sized complex electrical circuits" conductors, the fading star of introduced as "a new theorem of superconductivity, water from oil. dynamic electricity". optical delay and smashing 1019 Analogue Action. The design electrons. forum for analogue circuit 9.9 Update. News from around the engineers. industry. 1021 Circuit ideas. Z80 compatible In next month's issue. Audio amplifier 967 New Products Classified. The FSK transmitter. composite' design is one of the few areas of monthly round -up of new products feedback amplifiers, random electronics where science appears to at -a -glance. security light and transistor tester mix uneasily with art. The issue pits with integral hr,. measurement. those who believe in the evils of 995 Letters. Anti -gravity (yet again) feedback, the sound quality of oxygen - 1023 RF Connections. Minimum power gyros, cold fusion, pseudo -science, free copper wire and the necessity of radio telemetry, low -noise doubt and faith and more. using go'd-plated connectors against oscillators and radio physics. 1001 Applications. Switch mode power those who advocate calculated supply without the switching. electronics. Doyen of audio designers switched capacitor notch filter, John Linsley Hood presents the first of Wheatstone light bridge and a series of articles on the evolution of serial/parallel D to A. the audio power amplifier.

Readers in the USA facing difficulties in obtaining this magazine are invited to call Worldwide Media Services Inc. toll free on (800) 345-6478.

October 1989 ELECTRONICS WORLD + WIRELESS WORLD 937 TAYLOR RF/VIDEO MEASUREMENT INSTRUMENTS _MEASUREMENTS MADE EASY

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CIRCLE NO. 14 ON REPLY CARD COMMENT

CONSULTING EDITOR Green light for electronics Philip Darrington EDITOR Frank Ogden EDITOR- INDUSTRY INSIGHT While the spirit of glasnost has profoundly affected thé lives of ordinary people in Geoffrey Shorter, B. Sc. the Soviet Union and some of its satellites. it has yet to he reflected in any real way 01-66/ 8639 by the West's military establishment. The removal of cruise missiles from DEPUTY EDITOR European bases has only been undertaken in the light of other military Martin Eccles dev such as 01-66/ 8638 elopments stealth bombers and air -launched cruise missiles which can COMMUNICATIONS EDITOR effectively replace them- not much of a trade in the minds of those who feel Richard Lanlhley strongly about disarmament . 01-66/ 3039 Advocates of new weapons technology would say that while Mikhail Gorbachev ILLUSTRATION may be a "man that we can do business with" we shouldn't trust the political Roger Goodman in the we 01-66/ 86911 hard-liners Kremlin even though coukl possibly trust him. But they would DESIGN & PRODUCTION say that, wouldn't they? The Warsaw Pact threat, real or imaginary. has provided Alan Kerr the will for 'defence' development over the last 40 years and they don't want to see 01-661 8676 it end. We say that the time is now right to reassess the position. ADVERTISEMENT MANAGER A tangible enemy provides the spur to technology. but you don't have to look Paul Kitchen 01-6613130 necessarily to the plains of Russia. There are many enemies which threaten us and CLASSIFIED SALES EXECUTIVE some of them are becoming fashionable. Christopher Tern One has to admit that there isn't much money or kudos to be had in feeding 01-6618640 hungry people. And in any case, the World's poor don't yet threaten our lifestyle ADVERTISING PRODUCTION directly and can thus be discounted. Atmospheric pollution? This looks more Una Russ 01-6618649 promising. Air pollution derives from fossil fuel burning. Technological warfare in PUBLISHER the cause of energy conservation is acceptable. achievable. moves with the green Susan DUN'nev political groundswell and will make money for successful combatants. 01-66/ 8452 - A fraction of the UK's current defence budget could provide heat pumps-a sort FACSIMILE of refrigerator working in reverse- for every house in the land. These provide three 0/-66/ 8939 units of heat as output for every unit of heat put into the system..Any Western industry or Government which caused massive energy savings through new technology could gain for itself the respect- if that is the right word- normally associatec with membership of a nuclear weapons club. Development of clean energy sources would open a second front against the rape of our environment, but this must he tinged with realism. Most people would not willingly endorse a decline in their standard of living: the development of a power -generation strategy based on pig manure simply isn't on. We need a switch of development resources from nuclear weapons into nuclear technology. We should start by reinstating the fast-breeder programme with a level of funding on par with the Trident programme. We must endorse high-energy physics research. We should examine district heating programmes beyond simple economics. We need to look at realistic wind and wave power schemes. A substantial wind power REED research programme initiated in Scotland would make scientific / BUSINESS and political sense. ,- PUBLISHING The place of electronics and computing in all this is fundamental. To embark on these projects with determination would produce the technology spin-offs normally associated with defence. And the end result would he far more useful to everyone. Elrrtronv4 World + IYor/sae 11 arid is published monthly USP56%7540. By post. current issue £2.25. back issues Id availahk)E-'.511 Order and payments to 311 E/rrrrmun and Wireln.r Wodrl. Ouudtant I louse. 1 he Quadrant. Sutton. Surrey SM2 SAS. Cheques should he parable to Wireless Reed Business Publishing Ltd. FAltorial A Adserlüme offre:: EWB' Electronics World + World Quadrant I loos,,. The Quadr.mt. Sutton. Stores SM2 SAS. Telephones: Editon:d (11-661 3614. Advertising 111-616I 31}0 01.661 +464 +921rú4 REED BP G (FEN Facsimile: 111-661 8939 (Groups II di III) Brehm:111.MI +578 or 01+161 84eó 3110 baud. 7 data bits. even paros. This month sees a slight change in our title to reflect the wider changes in one stop -hi. Send oil -O. then EW W to shin: NNNN to sin df Meoslrade - Ouadrant Puhlshing Services No (11-661 32411. Solp- electronics. Electronics World reflects our coverage aimed at electronics linn rates: I )cur (normal talc) EMI UK and (3S outside UK. Subscription: Quadrant Subsenpbun Sennrs. Oaklrld Ilouse. Porpp- professionals, for instance in the field of computing tools. Wireless World moum Road. Ilaywards Ileath. Susses RI116 SDII. Telephone 114-I 441212. Please notdy a change srl address. USA: S116.110 airmail Reed underlines our commitment to retain coverage of those things for which we are Business Publishing (USA). Subscriptmns Office. 2115 E 42nd Street. NY 11(117 Oserseas adserns.ng agents: Fran: and Belgium: Pierre Mussard. 18.211 Place do la Madeleine. Pans 74515 l'nitrd Slates of famous: prophetic science, audio technology, radiocomms. Cynical? Next month's America: Jay Felnman. Reed Business Publishing Ltd. b15 East 42nd Sired. Neu York. N'o' 111117 Telephone (212) 1(67-3»,) Telex 231(27 issue will carry the first part of a definitive series on amplifier design by John USA maillne agents: Mercury Airfreight International Lid. Inc . 10(6) Englehard Ave. Avenel N.J. 1171111 2nd class postage paid at Rahway Linsley Hood. I enjoyed reading it. I hope you will. NJ Piatmastcr-send address to the above. ©Reed Business Publishing Lid 1989 ISSN 0216.3244 Frank Ogden

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CIRCLE NO. 38 ON REPLY CARD i USE PC COMPILERS FOR AN SBC

For really fast development of stand alone systems, use a Lancer or h Iunter target hoard with Hexatron's PrornDOS. This emulates DOS and BIOS calls, gives you silicon discs and even allows you to run non-ROMable compiled code in a ROM environment. Too good to be true? Call us now for a free demonstration. STOP PRESS: We now have a four port multi -standard serial expansion card for the Lancer and Hunter - ring us for details. THE SDS LANCER P^ An 8088N20 target board on a double Eurocard I r .- w . 4 a with two serial ports, four parallel ports, six e« counter -timers, four 32 pin memory sockets, ,.,_

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CIRCLE NO. 33 ON REPLY CARD

940 ELECTRONICS WORLD + WIRELESS WORLD October 1989 RESEARCH NOTES

Progress towards molecular wire Superconductivity: Micron -sized conductors may one day be considered large if research at the a fading University of New Mexico in Albuquer- star que comes to fruition. Thomas Bein and Patricia Enzel, who presented their findings at a recent meeting of the One essential difference between high- American Chemical Society in Dallas, temperature superconductivity and cold have been growing chains of conducting fusion is that the former definitely ex- molecules no wider than about a ists! Beyond that. one might well he nanometre in diameter. forgiven for thinking that they have one C pJ The basis of their research has been very obvious feature in common: in- synthetic versions of natural minerals genuity that never quite became practic- called zeolites. These are rocks contain- al. Certainly hopes have faded rapidly ing microscopic channels into which for the prospects of instant easy com- other molecules can migrate. Crystals of mercialization of superconductivity. 1` zeolite - Greek for "boiling stone" - are though giants like AT&T and IBM arc so called because they are formed in still working hard on it. 1-101011 volcanoes under high pressure and As I pointed out in Research Notes often exude bubbles of water from their (May. page 440) a serious obstacle in internal network of molecular channels. the way of many practical applications is What Bein and Enzel have done is to the loss of superconductivity in the take crystals of artificial zeolite and heat presence of high currents or high them to 400°C in a vacuum to expel any magnetic fields. So while zero resistance water vapour from the internal spaces. at liquid nitrogen temperatures may he Aniline and an oxidant were then intro- achievable. it isn't always possible then duced into the spaces, reacting to form to transmit commercially useful cur- long molecular chains of electrically - rents of l0' A/cm2 or more. conducting polyaniline. Other conduct- Technically, the insurmountable ing polymers such as polypyrrole and obstacle is the breakdown of the magne- polythiophene have also been intro- tic flux lattice. This is an entity created Dr David Bishop, whose images of flux duced into the molecular channels of by the quantization of any external lattice motion appear below (pictures by zeolites, though no experiments have magnetic field that penetrates the su- AT&T Bell Labs). yet been done to pass electricity along is passed perconductor. When current usually above the critical temperature at them. through a the resulting superconductor. which the material superconducts. So Obviously the extent to which this the force pushes against magnetic lat- while materials like niobium -tin need to principle can be used to make practical it tice, making -creep- or "melt-. The he cooled in liquid helium. they can electrical interconnects depends on the energy expended then appears to any, usually carry very large currents. With internal structure of the particular external source of EMF as resistance. In the so-called high -temperature super- zeolite. Some zeolites naturally have other words the superconductor has conductors, however, it's the other way parallel channels, while others have a ceased to superconduct round. Materials like the barium - variety of different networks. Bein and In the case of low -temperature (con- yttrium -copper oxide superconductors Enzel have noted about 200 different the ventional) superconductors. may well become superconducting at structures into which they believe ít at which this is is temperature happens temperatures as high as 93K. but their should be possible to introduce not just flux lattices melt at only 75K. This "wires" but also active components for These electron micrographs show makes them unsuitable for commercial switching purposes. All this, they think, yttrium -based (left)and bismuth -based uses at liquid nitrogen temperatures. should be possible using the appropriate (right)superconductors in a 20 gauss What's particularly depressing su- chemistry. for magnetic field. Dots are magnetic perconductivity researchers is the fact Clearly the prospects for ultra -dense particles attracted toi the ends of flux that although materials are being disco- circuit fabrication are exciting, especial- lines- which, in the bismuth -based vered with higher critical temperatures. ly in view of the possibilities of three- material, move about, revealing that the the same higher temperatures are vir- dimensional arrays. What remains to be lattice has melted. tually always associated with weaker done now is to develop the fabrication ,), and more fluid lattices. So although techniques and to ascertain the electric- materials are being persuaded to super - al properties of conductors and active conduct at ever -higher temperatures, devices at sub-nanometre dimensions. there's an inverse factor that seems Current -carrying limitations and quan- progressively to reduce the amount of tum effects are likely to be among the current they can carry. For that reason more obvious limitations. Nevertheless some researchers now believe that the this recent success is exciting because of holy grail of room -temperature super- the potential it holds for stimulating a conductivity may he unachievable at whole new approach to circuit technolo- - least for any practical purpose. gy. A ngstrotech nology?

October 1989 ELECTRONICS WORLD + WIRELESS WORLD 941 ELECTRONIC TUBESNALVES R.F. AND MICROWAVE -COMPONENTS Low PRODUCT RANGE Cost CRT's R.F. CAPACITORS CAMERA TUBES R.F. TRANSISTORS " RS & 232 COAXIAL ISOLATORS RECEIVING TUBES - CIRCULATORS RECTIFIERS DIODES SILICON CONTROLLED IGNITRONS RECTIFIERS Analysis IMAGE INTENSIFIERS SPARK GAP TUBES INTEGRATED CCTS TR/PRE TR TUBES KLYSTRONS TETRODES - 'MAGNETRONS THYRATRONS TRANSMITTING MICROWAVE TUBES TUBES TRIODES NOISE GENERATORS TUBE ACCESSORIES OSCILLATORS WAVE GUIDE PHOTOMULTIPLIER TUBES CIRCULATORS 1---F e PLANAR TRIODES VIÉY MAIN MANUFACTURERS t ACRIAN MULLARD AMPEREX NATIONAL EEV PHILIPS EIMAC RCA Osulln.ux Thurlby ,00dtd. DA100 Plotlxo1 Analyse( GENERAL ELECTRIC SIEMENS 9Mnp RS -423 1 MACHLETT SYLVANIA RS -232

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CIRCLE NO. 43 ON REPLY CARD Serial Data Protocol EPROM PROGRAMMER Analyser 100 (E)EPROM and MICRO -CONTROLLER types...

1 2506101ns 24 27512 47 87256 70 GR27256 93 80051' 2 2508'50'ns 25 2751210P 48 87C257 71 GR27512 94 8052' plus vat 3 2516610ms 26 27513 49 8755 72 GR27513 95 8044' £79 4 2516/501ns 27 275130P 50 8755A 73 8748 96 NMC27C16B 5 2532/10ms 28 27011'OP 51 6355' 74,8749 97 NMC27C328 6 2532'50ms 29 127010 OP 52 63701V 75 8750 98 NMC27C64 7 2564'10m5 30 HN27C101G 53 637010 76 8748H 99 NMC27CPI28 8 2564150ms 31 NMC27C1023 54 63705V 77 87498 100 NMC27CP256(B) The Thurlby DA100 is a very low cost protocol analyser 9 2758 32 uPD27C1001D 55 637052 78 8750H 101 NMC27C512 10 2716 33 TC5710000 56 637010 79 8741 for problem solving on asynchronous serial data 11 2732 34 T1.1527C010 57 75P54 80 8742 New 12 2732a1Ores 35 HN27C301P 58 75P64 81 8041' systems, particularly RS -232. 13 2732A'50rns 36 M5M27C100K 59 2816A 82 8042' Devices t4 2764750ms 37 uPD27CI000D 60 2817A 83 8048' 15 2764 38 TC57I00ID 61 2864A 84 8049' continually 16 2764A 39 HN27C1024G 62 EMULATOR 2716 85 8050' 17 2764A/OP 40 NMC27C1024 63 EMULATOR 2732 86 8751 being It provides baud rate analysis, data word format 18 27128 41 PD27C1024D 64 EMULATOR 2764 87 8752 19 27128A 42 127210 65 EMULATOR 27128 88 87C51 introduced 20 27128A1OP 43 TMx27210 66 EMULATOR 27256 89 87C51FA analysis, data monitoring (ASCII or Hex), triggered data 21 27256 44 M5M27C102K 67 EMULATOR 27512 90 8752 22 2725610P 45 TC571024D 68 GR2764 91 8744 'read only capturing, and test data generation. 23 27256 46 87C64 69 GR27128 92 8051' OP OueM Pulse ... what more could you ask! The DA 100 uses an oscilloscope as its display device. THE MODEL 18 PROM PROGRAMMER It connects to any standard 'scope via a single cable and All 1 Mbit EPROMS, Greenwich Instruments Emulators, 27C parts and EEPROMs now programmable! Still only displays 32 characters of text. Alternatively an optional Upgradable for future types. £189.95 Designed, manufactured and supported by MOP in England. LCD display unit can be fitted. An optional RS -232 Comprehensive User Manual. VAT 32 and 40 pin devices require low cost socket adapter. breakout -box is also available. Supports our new EPROM Emulator as 2716 to 27512 EPROM Mains powered unit external to your computer, without speed penalty. Fast interactive algorithms automatically selected as appropriate. Two independent communications protocols built in. Use with: Contact us now for full technical details. - any host computer with RS232 port and terminal emulator. - our PROMDRIVER Advanced Features User Interface Package available for all MS-DOS and PC -DOS computers. NEW FAST COMMs - 1 Mbit PROMs programmed In about 21 mins. Quick Pulse programming now available for suitable EPROMS - e.g. 2764s in 10 secs! Limited version also available for CP/M computers. Hundreds of satisfied customers. As supplied to: BT Mercury, UKAEA, British Aerospace, Thurlby Thorn EMI, Mitel, Cosworth Engineering, British Gas, Kodak, Lucas, Ferranti, Smiths Industries, Telecom Technology and major Universities and Colleges of Further Education. Please enquire about our other products: EPROM EMULATOR CROSS ASSEMBLERS EPROM ERASER BIPOLAR PROM PROGRAMMER Burrel Road, St. Ives, Huntingdon, Cambs PE17 4LE PAL PROGRAMMER GANG EPROM PROGRAMMER EPLD PROGRAMMER EPROM 8 PAL DESIGN 8 PROGRAMMING SERVICE Fax: 0480 64832 Tel: 0480 63570 Telephone ACCESS orders welcome. Phone for free information pack and price list - 0666 825146 l ELECTRONICS, UNIT 2, PARK ROAD CENTRE, MALMESBURY, II CJ WILTSHIRE, ENGLAND SN16 OBX.

CIRCLE NO. 20 ON REPLY CARD CIRCLE NO. 18 ON REPLY CARD

942 ELEC.! RON ICS \VORLD + WIRELESS WORLD October 1989 RESEARCH NOTES Oil from troubled waters

A growing problem facing the oil indus- ' r e try is the need for what's called liquid phase separation: or. more simply. getting rid of the salt water that inevitably accompanies crude oil pumped up from the sea bed. In theory. all that's necessary is to put the fluid mixture into a separating tank and wait for the water to sink. In -J practice - as with good salad dressing - it can take a very long time, especially if r the oil is viscous. One method of speeding up the process. developed many years ago. is to apply a high -voltage AC field between pairs of electrodes in the mixture. The effect is to help water droplets coalesce and hence grow to a point where gravity does the rest. The physics of the process is only vaguely understood and may include a variety of effects such as .t, electrophoresis. dipole coalescence and the formation of intermolecular bonds. Removing water from oilmistures. With no electric field applied (left), droplets in Whatever the theory, practical sys- the jet are slow to coalesce; but with a pulsed high -voltage field (right). the process is tems have been developed using con- much faster. Gravity can now complete the separation. Pictures by Dr Philip Bailes. ventional electrodes and AC at a variety of frequencies. They all work to a useful mark:space ratio is around I:I at fre- considerably lighter than its AC prede- extent but suffer from the need for quencies between 8 and 10Hz. Also. cessors, a significant benefit aboard oil bulky equipment and from reduced effi- because of the pulsed nature of the platforms where real estate tends to he ciency due to short-circuiting within the voltage. Bailes has been able to insulate expensixe. Laboratory prototypes (J. fluid mixture. his electrodes with plastic. thus avoid- Electrostatics Vol 17, 321-328) have Dr Philip Bailes and his colleagues in ing short circuits through the fluid. used a conventional 15kV EHT gener- the department of chemical engineering Under pulsed conditions, charge dis- ator. the output of which is shorted by a at Bradford University have now disco- tribution in the fluid is still high. even PD5O0 triode wired in shunt fashion. vered that the separation process be- with insulated electrodes, because the Waveforms applied to the grid of the comes much more efficient if square determining factor is no longer DC PD5(I0chop up the EI-IT as required. pulses of direct current are used instead conductivity hut the relative permittiv- Dr Bailes and his colleagues are now of AC. By optimizing the shape and ity of the insulation and the oil/water extending their work to investigate the frequency of these pulses. the separa- mixture. This remains relatively con- uses of electrostatic fluid coalescence in tion of oil and water can he improved stant. even x hen the water content a variety of other industrial situations very considerably. rises. where liquid phase separation is in- Depending to some extent on the Of particular interest to engineers is volved and where mechanical methods design of the electrodes. the optimum the fact that the pulsed DC generator is would he cumbersome.

Optical delay for high-speed photography

How do you photograph events before FLAT MIRROR ARRAY they happen? Or; to be more precise. CONCAVE SPHERICAL how do you trigger a camera to catch the IMAGE MIRROR rt 3, li CONVERTER very beginnings of a sequence that may 1 CAMERA last a was ft) only few nanoseconds? That ENTRANCE . EXIT BEAM the problem faced by Edward F. Kelley, BEAM formerly of the US National Institute of HV Standards and Technology (the Nation- PULSE FLAT al Bureau of Standards, as was). He MIRRORS wanted to film the essentially random - BREAKDOWN IN timed electrical breakdown between a LIQUID CELL pair of electrodes immersed in fluid Fir. I. Image -preserving optical delay devised by such as hexane or transformer oil. The CURRENT PULSE syYtenr, Edward Kelley at TRANSFORMER NIST in the US; it functions as a trouble is that even if it were possible to XENON mirror trigger a camera in zero time (which it FLASHTUBE of long focal length and small aperture.

Co11 ued overleaf

October 1989 ELECTRONICS WORLD + WIRELESS WORLD 943 RESEARCH NOTES

obviously isn't), there are initial phenomena that precede any detectable insulation breakdown. What's needed is some means of delaying the image from reaching the camera for at least a few hundred nanoseconds. This, under y f ideal circumstances, can allow the camera to record the phenomena that precede the triggering event. What Kelley has successfully developed is a device called an IPOD (image -preserving optical delay) which he's currently attempting to patent. It 4 . consists of an arrangement of mirrors that ingeniously lengthens the optical path by over 100 metres (Fig. I). Since the system exploits the entire surface of t the concave mirror in a symmetrical , . . fashion, all astigmatism is effectively cancelled out, leaving a high quality image, dependent mainly on the quality high -voltage pulse, a "streamer" Fig. 2. Result of the image -preserving of the mirror. appears from the tip of the needle delay. The camera was triggered a few Using the set-up as shown, Kelley has electrode and grows across to the spher- nanoseconds after breakdown occurred, recorded the evolution of an electrical ical electrode. When it makes contact, at which point the phenomena in the gap discharge in oil from its very first mo- breakdown occurs, resulting in a hot were as in frame 5. The camera began ments. (The xenon tube provides illu- plasma channel across which the voltage taking pictures about 150ns later mination to permit shadowgraph photo- drops to zero within a few nanoseconds. (corresponding to frame 8). Interval graphy.) What happens is that at some The sequence (Fig. 2) shows just how between frames is 5Ons. Most of the random time after application of the complex the whole process is. frames were stored in the air.

Smashing electrons reveal all

CERN's massive new atom -smasher. they break up. It's like trying to study together electromagnetism, the nuclear the Large Electron Positron collider the innards of a chip using a hammer. forces and gravity. (Britain, incidental- (LEP) started work in mid -June under What CERN scientists hope will ly. is heavily involved in Aleph. Delphi the Jura mountains on the French -Swiss emerge from their electron -positron and Opal: together with other aspects of border. Five years in the building, it collisions are some interesting entities CERN's work. they receive £45 million comprises a 27km-long circular tunnel called W and Z particles. These are per annum from the Government.) (pictured here) large enough to drive a believed to he the means by which the As well as W and Z particles, CERN train through. British Rail would be so-called Weak Force is mediated. Or. researchers will also he looking for envious of its performance. because thought of in another way, the W and Z I liggs particles, hypothetical mass car- inside the tunnel is a circular evacuated particles are to radioactive decay what riers which appear only at very high tube in which electrons and positrons photons are to electromagnetic radia- energies - and of course the element travel at almost the speed of light. tion. quarks, particles from which all other They're injected by means of special subatomic particles are thought to be accelerators and controlled in their composed. Hight by powerful magnets located all Meanwhile over in the USA. physi- the way around the 27km tunnel. cists at the Stanford Linear Accelerator The object of the LEI' is to accelerate Center have already created particles electrons and positrons (their using a much smaller 3km-long positively -charged equivalents) in machine. In the first four events re- opposite directions around the ring. corded, the Stanford machine revealed The particles then collide in the most LEI'S first experiment involves an a pair of narrow hack -to -back jets of violent way possible. releasing what initial look at the electrically -neutral Z hadron, thought to be the characteristic physicists hope will he a shower of particle, first discovered at CERN in fingerprint of a pair of quarks. fascinating subatomic debris. I983. Even at reduced beam power. The battle is now clearly on to make Up till now, atom smashers have LEP's four experiments, code -named fundamental discoveries that may lead mostly used larger micro -missiles such Aleph, Delphi. Opal and L3. are ex- for the first time to a true and details as protons and ions because in some pected to intercept a few thousand Z understanding of the very finest struc- ways they're easier to generate and particles per day. This, it's hoped, will ture of matter. manipulate. The trouble is that, being give physicists the chance to specify the more complex, such particles are cor- parameters of the Z and so help towards Research Notes are by John Wilson of respondingly harder to analyse when a Grand Unified Theory that ties the BBC World Services science unit.

944 ELECTRONICS WORLD + WIRELESS WORLD October 1989 Put our test set to the test. Can you find anything it can't test?

~) i:: ,-- -=1 / t1

Cordless Pager DTMF System Cellular Cone P.M.R. Base station telephone mobile

Stabilock 4031: Portable Communication Test Set In the time it takes to read this, the Stabilock 4031 could test any of the devices pictured above - with one minor exception. Quite a performance given the dramatic evolution in radiocommunications techniques and standards. _ To meet the challenge, we packed more than 25 years of experience into a single, _ . _ . -, ' t highly versatile unit. You won't need an operating manual to use it: time -saving features include automatic measurement functions and brilliant graphics, with both 10. r 1 numeric display and simulated analogue meters. - - ry - u -e The 4031 comes with all test devices integrated, while its modular design i.1J-1 L17J...1 r-r-Yg Stabilock - -o . m21 o and flexible software system can adapt to all testing demands, both present and 1.4.41 e 7 _ 0 0-- 0_- 0 future. The exceptions are hardly worm mentioning. Born to set tomorrow's standards in measurement reliability. Schlumberger Instruments Schlumberger Instruments Division Schlumberger Instruments Schlumberger Technologies GmbH Schlumberger Instruments Victoria Road Instruments Division 50, avenue Jean-Jaurés Instruments Schlumberger Farnborough. Hampshire Ingolstádter StraBe 67a BP 620-06 20 North Avenue GÚ14 7PW, England D-8000 Munich 46. Germany 92542 Montrouge. France Burlington, MA 01803, U.S A -el.: (0252) 544433 Tel.: (089) 318 89-0 Tel : (1) 47 46 67 00 Tel (617) 229-2548 Fax (0252) 543854 Fax (089) 318 89 160 Fax: (1) 47 46 67 27 Fax: (617) 229-4885 CIRCLE NO. 37 ON REPLY CARD HYPOTHESIS - IONOSPHERE

Storm cells act as a t any one time, there are thunderstorm. several thousand thun- That breakdown is lightning and, giant voltage derstorms roaming the although the thunderstorm generator is planet to sustain the con- powered by charge separation in the stabilizer between the tinuous electrical dis- turbulent maelstrom of ice crystals, rain ionosphere and Earth charge between the earth and the upper and cloud at the core of every cumulo- atmosphere. nimbus, each lightning stroke to ground says electrometry The driving force behind this activity also drains charge from the ionosphere. is the sun, raining charged particles on It is very difficult to tell how much researcher Tony the ionosphere and charging it to hun- charge is drawn from the ionosphere Hopwood dreds of thousands of volts with respect outside the storm cell by lightning to earth across a leaky atmospheric strokes, because it is impossible to draw dielectric. On a normal summer day, an accurate energy balance for the com- the atmospheric voltage gradient aver- plex reactions taking place in several ages ~Vim positive above earth, ris- cubic kilometres, let alone accurately ing to kilovolts per millimetre when the measure the energy content of every atmospheric dielectric breaks down in a discharge. This paper suggests ways of

946 ELECTRONICS WORLD + WIRELESS WORLD October 1989 HYPOTHESIS - IONOSPHERE

pinpointing the ionospheric contribu- polarity with altitude. growing cumulus rotneteors) gradually prevails. and a tion. shower clouds become negatively elec- cold core of positively charged pre- A single thunderstorm cell is quite trified underneath as invisible water cipitation forces its way towards the compact. only influencing a few hun- vapour puffs into visible cloud. Ns the ground. presenting a highly positively dred square kilometres during its short cloud grows. cloud -building condensa- charged wedge surrounded by or along- life: the only effects that extend more tion releases heat at higher levels. sus- side a negatively charged zone of rising than 2(1km from it are electrical. of two taining the updraught until the raw cold warm air. main types. Most easily observed is the of the upper atmosphere freezes the top radio -wave signature broadcast by each of the cloud into a crew cut in a zone Detection lightning stroke: this is detectable A ground -based electrometer will see thousands of miles away and individual such a passing cloud cell as a negative storm fronts can he tracked for days on At any one time, charge. followed by a region of positive end using radiogonionteters. charge. then negative charge (Fig. I ): there are several the ratio and duration of the charges will Field variations depend on the track and maturity of the The other electrical signature is the thousand cell. Individual young cells with little or local distortion of the ambient electric thunderstorms no precipitation usually present mainly field by a storm. A single cell can affect negative charge and an electrometer the field up to 50km away and a band of roaming the planet reading the edge of a passing mature storms over I00km. Occasionally. giant cell will also record predominantly electrical storms alter the ambient field negative charge. From the electric field up to 3(I(Ikm away. Electric field varia- where the natural atmospheric poten- profile. it is possible to judge the matur- tion is logged by a I)C electrometer tial may be over a million volts positive ity of any passing cell by rioting the connected to a well insulated antenna, to earth. It is this extra ingredient of relative duration of the positive and and recorded. positively charged ice crystals and hail nega t is e phases. Electric field variations provide some that turns the shower cumulus cell into a The most striking feature of shower clues to what happens as rising warm air sparkling anvil cloud. clouds (apart from from lightning) is the condenses into cumulus shower clouds As they start to fall from a height of abrupt transition from negative to posi- or develops into a full-blown cumulo- several miles, the positively charged ice tive charge. or vice versa. associated nimbus with its characteristic anvil crystals and hailstones meet the warm with the onset of precipitation (Fig. 2). shape. spiced with lightning and hail. updraught head on. Over a period of The induced ground charge reading can Although normal atmospheric be- minutes, the increasing burden of melt- swing from negative to positive kilovolts haviour dictates increasing positive ing hail and coalescing drops (hyd- it seconds. demonstrating the abrupt

,V BOV Torrential ran

Wet Insulators M ..- 025V025V

-v 2956E 1130 3 6 Max 409 snorer 4 15 16 17 18 19 20 21 22 23 24

Weak !opining cell ends

21.568 1630 10V aperae 56 1 8 9 O 112 13 14 15 16 11 16 17 20 21 22 23 24 26 26

Fig. I. Passing cloud cell seen by ground electrometer. Fig.2. Rapid negative -to -positive transition as rain starts. Fig.3. Storm group receding from a nearest approach of20km. Stabilizing effect of lightning storm on ambient field can be seen. Fig.4. Onset of local instability after lightning. Fig.S. Charging and 2 3 4 5 6 discharging effect oread? stroke is seen here.

October 1989 ELECTRONICS WORLD + WIRELESS WORLD 947 HYPOTHESIS - IONOSPHERE

demarcation between charge zones as cleanly from the background level. As was little rain, so the signature at closest they pass overhead and showing clearly they get further away. they begin to approach was negative from strokes 2 the enormous potential differences influence the background level with a onwards. The charging and discharging available to trigger lightning strokes delayed recovery (12) of increasing effects of each stroke were well shown, between different parts of the cloud, or bipolarity (16). Stroke I shows a superimposed on an ambient field positive and negative strokes to earth. marked distance effect, which progres- which rose to 800V across a An insulated antenna under a thun- sively reduces up to the last stroke from IOOtlmegohm electrostatic voltmeter der cloud may reach very high voltages that cell (15). The nearest stroke from switched into circuit as the electrometer as charge centres pass overhead: and cell 3 occurs around 20, and strokes limited at -350V. The discharging effect close to a storm accurate readings he - from a much more distant storm can be of positive strokes 14 and 15 is well come very difficult, so lightning tran- seen superimposed on some of the field shown, and linked strokes 16-17 show sient observations are more instructive recovery curves (Fig. 3b). how strokes can recharge adjacent cells and certainly safer when taken from It is not possible to determine abso- and trigger additional strokes by en- outside the storm. where the fine detail lute distance scales from lightning tran- hancing local potential differences. of the electric field is not obscured by sient traces, because the energy levels A fresh storm group then approached the electrical turmoil. Even at 15km. and local attenuation cause huge varia- (Fig.2), the outer positive charge field lightning strokes produce transients of tions in the received signals. The arriving at stroke 14 (1720). As the over IOOV on an antenna. but changes nearest strokes were about 20km away. charge built to +300V, a stroke to in the profile of the recorded transient, timed from the thunder. Stroke I would ground was observed sonic 4k ni away to as well as its amplitude, provide an have been nearly 40km, and the others the north-west which did not appear on approximate measure of distance. in the range 25-35km. The tiny strokes the trace. This confirms the highly between 18 and 26 are over 5Okm dis- screening effect of a strong local field Observations tant. These distances alter with atmos- shown by the highly attenuated strokes pheric impedance, which largely de- 16-19. The electrometer trace of a storm group The positive field collapsed and starting at 1530 on June 4. 1988 receding pends on humidity. The antenna back- swung to - 2(I(IV in less than 5s as a ground level of 4V suggests a from a nearest approach of 20knt. relative cloudburst started at 1726. During the shows many typical features (Fig. 3). humidity of 65-70%. first three minutes of the downpour, the reason the The first feature of note is the stabilizing The for delayed recovery aerial insulators became wet and the effect of the onset of lightning on the of the ambient field is worthy of spe- voltage readings decayed as the input ambient electric field. Judging from this impedance fell, so recordings continued and other recordings. it seems that a on the higher -gain 10V FSD range. At lightning storm can influence the stabil- Each stroke is this stage the storm centre wa directly overhead, and corona can he seen on ity of the ambient electric field over a detectable large area. Figure 4 shows the onset of the trace as the charge swung positive. local instability when lightning ceases in thousands of miles Despite the loss of signal during the an isolated storm cell some 50km away. rain, the preponderance of positive In May 1958. it was suggest by Von- away and storm charge suggests a mature cell. with the negut and Moore' in their paper 'Giant cold rain cutting off the warm up - Electrical Storms' that the surprising fronts can be draught and bringing the thermodyna- stability of the intense electric field tracked for days on mic thunder engine in that cell to a halt associated with tornadoes observed by as new cells take over and leapfrog the Gunn2 was due to the continuous dis- end using storm across the countryside. charge surrounding the vortex acting like a giant voltage stabilizer tube. It goniometers Equipment may well be that ordinary thunderstorm The equipment used to record the elec- cells have a similar stabilizing effect by culation. The overshoot may represent tric field has been specially adapted and drawing excess charge from a much that part of the stroke energy drawn comprises a purpose-built valve electro- larger area as part of the global charge from the ionosphere beyond the im- meter capable of processing DC input equalization between the ionosphere mediate storm zone. Although the re- signals to +350V at an input impedance and earth. covery time approaches half a minute of 2gigohms. It is self calibrating, and The trace shows that there are prob- for strokes 1,2,5-8. the stroke pair 5,6 contains variable attenuation, com- ably three storms cells, comprising has a similar recovery time, suggesting pression and damping circuits. The sig- strokes 3.4,12,16 and 1,2,5-11, 13-15. that the energy reservoir available to nal is fed to a modified 6in-scale, single - The remainder. 17-28. are from a new restore the level is substantial. and may channel DC servo pen recorder, type cell, all three cells showing a typical he the ionosphere above and round the EPRIOA, with full-scale recordings of acti\e life of 15 - 20 minutes (Fig. 3). storm. Close study of the effect may electric field signals in the range The trace was recorded on the ±10OV help show the part played by charges ±25mV to 350V from a well insulated range to A. then on the ±50V range, drawn from outside the storm cell in the wire antenna 20m long some 10m above and nearly all the strokes were full-scale thunderstorm energy equation. ground. from an average atmospheric baseline Two storms recorded on July 5, 1988 References falling from about +50V to +4V. provide further insight into the com- t. Vonnegut and Moore. Recent advances Fortunately, amplitude is not the only plexity of storm fields (Figs 2.5). in atmospheric electricity. Proceedings of way of judging distance. The nearest The first storm group passed within Second Conference on Atmospheric Elec- was I cell that producing negative -going km to the south of the recording sta- tricity. Ed. L.G. Smith. Pergamon. 1958. strokes 3.4.12,16. Nearby strokes re- tion. and gave a sequence of some 90 2. Gunn. R.. Giant electrical storms. Jour- corded from outside the storm field rise strokes in the period 1520-17OO. There nal of Meteorology. 13.

948 ELECTRONICS WORLD + WIRELESS WORLD October 1989 UPDATE

lite weather image relayed as a data file BBC Telesoftware goes off the air from the Meteorological Office. This enabled computer users to receive and BBC television has announced the clo- £100-£200, can still be used to access display high -resolution images of the sure of its Ceefax telesoftware service, teletext pages in the ordinary way. But UK's weather patterns and even to with effect from the end of August. This the closure comes at a time when other assemble them into animated sequ- service, which provided a weekly ration countries appearkto be extending their ences. Another major use of telesoft- of computer programs and data files for teletext systems - Italy. for example. ware was to distribute notes on educa- users of the BBC Micro and IBM PC - began a telesoftware service on August tional radio and television programmes compatibles, was started in 1983 as part 1. to receivers in schools. of the BBC's computer education initia- "It's quite a blow to us", said Ram By ending the service, the BBC ex- tive. Banerjee, managing director of GIS, pects to save about £60 000 each year, Its withdrawal. at little more than a the company which makes the teletext and to gain transmission capacity which month's warning, must be the most adapters approved and supported by it will use to provide, among other abrupt abandonment ever of a UK the BBC. `'Telesoftware is one of the things, additional financial and sports broadcast service. No hint of the closure main reasons why people acquire the news and regional teletext services. is given in the BBC's annual report, card. We only heard about the chopping *BBC Annual Report & Accounts 1988-89. which appeared in the week of the of the service one day before it was BBC, 116 pages A4 format . announcement; and indeed a telesoft- announced." GIS is already receiving ware transmission schedule extending angry letters from disappointed cus- into September had already appeared in tomers the monthly computer press. One feature of the BBC Ceefax ser- Technology - Telesoftware receivers, which cost vice to disappear will be the daily satel- which direction? West Japan, the thrust _ In Germany and a e of technology is towards the development of products themselves; in the UK, we are still working on how to make them. This view is the outcome of a study conducted by the PA Consulting e _ Group in Europe and Japan. I }L. ' According to John Puttick of PA. "The UK is struggling to catch up in a global marketplace where product availability and quality are 'givens' and the better product will gain market share". UK products, says the report, .05 are not highly rated, either by ourselves or our competitors; manufacturing technology in Germany and Japan consistently delivers high quality, short lead times and low costs, process technology no longer being an R&D priority. The report isolates a number of issues of "concern and optimism" for the UK and Europe as a whole. Among those r offering cause for concern, an unwillingness to invest and a reluctance to adapt to new technologies emerged as the main reasons for the UK's poor performance in the development of products. It also seems that the Japanese are readier to engage in collaboration before the competitive stage than Euro- pean companies, although there is worldwide agreement on the benefits of such co-operation. On the other hand, the UK and West Germany believe that leadership in As part of British Telecom's remit to diversify, the research people at R&D is the appropriate strategy, while have up with a possible solution to the capital's parking Martleshanr come France and Japan choose to follow close use the system to test cellphone problems. And if that doesn't work, they'll behind the development and thereby aerials. attain a competitive position.

October 1989 ELECTRONICS WORLD + WI RELESS WORLD 949 UPDATE Limited life for telepoint?

Replying to a suggestion in The Inde- between that and telepoint from around pendent that the proposed Personal 5:1 to perhaps 2:1. Since Mercury is Communication Networks pose a threat involved with both, Gosling sees no to telepoint, in that they will be able to problem there. either. As he points out, do anything that telepoint and cellular Lord Young's announcement of the radio can do. a spokesman from Ferran- proposed PCNs made it clear that PCNs ti Creditphone said "The company is are intended to compete with cellular delighted with the announcement (of radio, as evidenced by the prohibition PCNs) and intends to respond to the call of cellular licensees from holding PCN for licence applications. The company licences. does not see PCN in any way as a threat Mercury Callpoint also sees the esti- to telepoint". mated seven-year period to the intro- VHF op -amp According to Richard Gosling. duction of PCNs as a time in which to General Manager of Mercury mobile establish telepoint as a facility which Not one of the usual sort which boast services, cellular radio equipment users will continue with in the presence gain/bandwidth products in the high prices will decrease over the next few of new. but far more expensive, MHz range but a device which years and reduce the price differential methods of personal communicat ions. actually 'operates at 150MHz with just a 3dB droop. Sold through Anglia Microwaves, Making a career in electronics the CLC505 is said to have a slew rate Young people contemplating a career in guidance. Also included is an informa- of 1700V/1s with a settling time of electronics should find plenty to interest tive survey of optoelectronics, a version just 12ns. It provides this perform- them in this year's National Electronics of the IEE's 1988 Mountbatten Lecture ance at a supply current of 90mA and Review. This 88 -page illustrated pub- given by Sir William Barlow; and re- a price of £5.75. lication from the National Electronics views of developments in electronics in Council contains a wide-ranging collec- 1988 and of the NEC's activities. tion of articles on many aspects of Among the objectives of the Review electronics. Its theme this year. electro- are to encourage young people to take Fast bipolar nics in the home, is tackled by authors up careers in electronics or information from manufacturing, research, educa- technology, and to emphasize the im- A self -aligned bipolar process claims delays less than with power tion, trade unions and management. portance of these subjects to opinion - gate of 80ps They deal with topics such as the auto- formers. Copies have accordingly gone consumption of 2mW/gate. Developed mated home, information technology, out not only to schools but to MPs and by AT&T, the process uses polysilicon personal computing, flat -screen dis- the Good and the Great. However, emitters with three levels of metal inter- plays, satellite TV, and electronic guid- single copies are still available, and connect. Other trades between speed ance for cars. Of particular interest to without charge: to receive one, contact and power can be made by varying the school-leavers will be the article by the editor, Jim Slater, at the Indepen- process geometry. Power levels are Tony Watts. of the National Institute dent Broadcasting Authority, Crawley programmable from cell to cell. for Careers Education and Counselling. Court, Winchester, Hampshire S021 The company plans to offer a 2(10 -cell on the use of computers in careers 2QA. library with a migration from gate array to semi -custom design. It has successfully produced a 5Gbit/s multiplexer Late extra and a 4.6GHz frequency divider using All those in industry who were unable achieve our qualification". In the six the process. to study for a degree on leaving school years of the Council's existence, it has need not despair: there exists The been conscious of the need to make its Engineering Council's examination, examination better known, but was Up and away which is of degree standard. also aware of more pressing matters, a minor hiccup in the To remind employers and em- since it was starting more or less from Suffering only ployees of the opportunity for further scratch. launch sequence, the Olympus I satellite has been successfully placed in orbit study, The Engineering Council is An average person with a Higher by an Ariane 3 rocket out of Kourou. running a campaign, with the aim of National Diploma or Certificate will, French Guyana. encouraging degree -less, but nonethe- it is estimated by Ron Kirby, Director The platform. the first in a series of less able people to qualify as chartered of Public Affairs, take around three engineers while in employment. years to attain degree level, assuming several high powered communications satellites due for launch of the next few As Professor Levy, the Council's a clear run at it. years, carries for separate payloads: Director - Engineering Profession, The examination is held in May DBS transponders for both and the points out, "Because of our education each year at 40 centres in the UK and RAI system, (these people) often think of throughout the world. For informa- BBC, specialised business telecoms operated by several European PTTs themselves as failures. Most of them tion, write to The Examination Offic- and an experimental high frequency are far from failures and have a lot to er, The Engineering Council, Savoy microwave link which to give their companies and the country. Hill House, Savoy Hill, London aims open up new hands for use towards the end of We want to help them study to try to W C2 R OB U ; telephone 01-379 7459. the century.

950 ELECTRONICS WORLD + WIRELESS WORLD October 1989 Maximum IEEE -488 Performance for Your High -Speed AT Computer

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CIRCLE NO. 13 ON REPLY CARD UPDATE

Royal Television Society in 1985, as the BBC was about to celebrate the 50th l anniversary of its television service. However, the proposals were costly and the television industry did not commit sufficient funds. The position has remained uncertain ever since. It now seems that Haringey Council may offer the studio area to Mountview Theatre School for scenery storage. 1. .. Another plan, for a Birth of Broad- .,.ir casting Centre, run by a full-time staff and costing around £3M to set up, has ,.t:, been put forward by the Alexandra Palace Television Trust. The Trust comprises members from the broadcasting and equipment industries, and those who were there at the birth of television Adele Dixon opens the world's first public television service from Studio A at the in 1936. Alexandra Palace on November 2, 1936. AP's heritage is now under threat. Their work should not he lost. But the (Photo: BBC) future for the museum seems uncertain unless a scheme can be found which could complement the present day uses Ally Pally threat of Alexandra Palace, and meet the need for economic viability. This might mean The cradle of television broadcasting, the public interest to restore the build- a more modest start to the project, with the Alexandra Palace in north London, ing at a cost of £45M, work which is an expenditure counted in thousands may not after all have its old BBC studio nearly completed. instead of millions, staffed on an occa- space converted to a television museum The south east wing, home of the sional basis, say when other events are because of the high cost of the plan. world's first regular television service, staged at the new Alexandra Palace. 'Ally Pally' as it is affectionately known, was not datilaged by the fire, and its use The Ally Pally Trust can be contacted was badly damaged by fire in 1980 but as an exhibition of television history and at I Coleridge Gardens, London NW6 its owner, I laringey Council, decided in development was proposed by the 3011. - Roger Driscoll Slipped disks and laptop scrap Hard disk drives are the type of essen- The wrangle about PC bus stan- that is bound to be the subject of a tial sub -system in a PC that most users dards - whether MCA or EISA is best legal scrap. take for granted. It is there, and it for the future - took some interesting This is the Dynabook, the com- works, doesn't it? After all, it's bound turns during the month. Intel pany's smallest lap -top so far. Only to be faster than a floppy disk at announced it had an EISA chip -set available in Japan for the moment, it reading and writing in data. available. This will make it possible weighs just six pounds and is priced at Sometimes these things can go for PC manufacturers to produce sys- the equivalent of £900. The name, wrong,. however; and if it happens in a tems capable of taking 32 -bit expan- Dynabook, is the legal problem, big way, the manufacturer can have a sion boards designed for the "stan- however. It has been adopted by a US problem. This time the man with the dard". company, which has also introduced a problem is Alan Sugar, boss of Am- At the same time, Compaq and product of the same name. What is strad. The company has been obliged IBM, respectively chief protagonists more, Dynabook's Dynabook (if you to recall more than 7000 of its 2286 and for EISA and MCA, have signed a see what I mean) looks to have a much 2386 PCs because of disk controller patent exchange agreement. Though better specification, featuring a 286 problems - essentially the current Compaq vehemently denies it will be processor against an 8086 in the Tosh controllers are not very good at the making one, this gives it the right to system. It also features an LCD job. make an MCA machine. It also raises measuring 11 inches across the di- Amstrad is operating the highest the intriguing prospect of IBM doing agonal. profile solution - swapping existing an EISA machine - licensing an adap- Not to be left out, Herman Hauser, machines for new ones with better tion of its own PC/AT "industry stan- designer of the dear old Acorn Beeb controllers in them. That will please dard" bus. machine, has been back at the drawing the current users. It may also please Portables are all the rage at the board, threatening a bookalike lap- some future ones, for there are sugges- moment, with Sharp deciding it is top that will have no keyboard. In- tions - totally unfair and specious of going to take over the UK market stead, users will have an electronic course - that the recalled machines through its new distributor, Kode. stylus to scratch away at the display. will themselves be refurbished and put Currently, of course, the market is Watch out for The Active Book Com- back on the market at what is called an dominated by Toshiba, and that company - you have been warned. "aggressive" price. pany has just announced a product - Martin Banks

952 October 1989 ELECTRONICS WORLD + WIRELESS WORLD UPDATE

HF radio goes S H F International broadcasting reduces its Double standards dependence on the fickle ionosphere a little this month with the introduction According to the Department of Trade public procurement forthwith'. of a new satellite radio service in the and Industry (DTI), buying computer Explaining why, the director of the US: C -Span, the Cable and Satellite hardware that conforms' to Open Sys- CCTA (the department most involved Public Affairs Network, which pro- tems Interconnection (OSI) standards with directing the use of computer tech- vides nationwide television coverage takes the risk out of major investments nology within government), told the of legislative sessions and hearings in in technology. Launching an initiative MPs who produced the report that Washington DC, offers two new audio to encourage adoption of OSI by all adoption of OSI would be "counter subcarriers on its satellite feed. On sectors of the UK economy, Lord productive" and "it might detract from one is a selection of programmes from Young, Secretary of State at the DTI, the perception of value for money". several European international broad- stressed that the standards offer cost This 'message' was reinforced by Lord casters, while the other carries the advantages (as hardware can be bought Young who told the same MPs that OSI BBC World Service 24 hours a day. from many competing suppliers within was not mandatory because "you can- Through the new outlets, European the European Community), and are not have mandatory standards for every programmes will be available to a also more dependable (as hardware is single contingency". potential audience df 44 million on US interchangeable). Not being tied to one This reluctance on behalf of Govern- cable systems. Would-be listeners who supplier also reduces the possibility of ment to abide by OSI standards creates lack a cable connection can receive the being lumbered with obsolete equip- a problem for the DTI's initiative. How satellite direct on domestic equipment ment. can the Department make a case for the - the signal is not scrambled. For Given the apparent advantages, it is private sector to adopt OSI, if Govern- improved audio quality, the BBC surprising that the Government could ment does not adhere to the advice to switch to a digital audio feed stan- hopes not accept the recommendation, found itself' Perhaps a case of double direct to Washington. Pounder in a recent report from MPs into the dards? -Chris In Europe, satellite reception of state of policy towards information 1. House of Commons Trade and Industry BBC World Service is already avail- technology, that "we recommend that Committee, First Report, 'Information Tech- able via a subcarrier on Eutelsat. OSI should he made mandatory for nology',f5.90, ISBN 0102714894. Bugs in the -

woodwork? -444-41

1 ; 1k1 Early in June, shortly after the Russian bugging accusations appeared in the Sunday newspapers, we offered the "\¡ Soviet Embassy an opportunity to clear up speculation that the bugs said to have been found there were placed not by ( ,. but by Russian agents in British agents, 1` order to create propaganda. We told its spokesman Mr Daneliski that we were prepared to hire an independent expert to examine the bugs, d making it clear that we were quite happy to let a Soviet representative witness the examination. He said that he would speak to the relevant bodies about it and get in touch with us. Since early June, we have not been t able to contact Mr Daneliski and he has not contacted us, despite our many A test engineer from Hughes Aircraft inspects wiring inside the aft section of a kill requests. In early July, we were told vehicle, part of the Star Wars programme. that Mr Daneliski was out of the country so we went straight to the Ministry of Foreign Affairs in Moscow; again no Space invader joy. We were told, rather discouragingly, Looking considerably out of place in the Hughes Missile Systems, under contract that we could try writing to the Embassy new politics of glasnost, the .ground - to McDonnell Douglas, is providing three test in London. But perhaps the Soviet launched KITE kill vehicle has been target avionics for two of the authorities' apparent unwillingness to designed to intercept incoming missiles interceptors. The first should have clear up the matter speaks for itself. as they enter the earth's atmosphere. flown in an August launch.

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CIRCLE NO. 50 ON REPLY CARD UPDATE -SPECIAL REPORT When Piper Alpha lost touch

The ill-fated Piper Alpha oil production platform was the hub of a system of radio links which failed with the initial explosion. In the subsequent confusion, gas was pumped to the centre of the disaster for a further hour. Jeff Crook has been following the Government's attempts to discover what lessons can be learned.

ship called the MV Lowland partment of Energy's investigation. after the Mayday. The inquiry learned Cavalier gave the first warn- contained in its interim report. was that that it was only then that operators at ing of an incident. She put rupture of the gas pipeline from Tartan Claymore learned of the scale of the out a "Mayday" call from released a huge quantity of fuel to the disaster. Production was immediately her position in the North Sea fire on Piper Alpha. shut down and arrangements were close to Piper Alpha at just after 2158, A field communication system linked mode to start de -pressurizing the pipe- onJuly6, 1988. the platforms and the coast with a lines. Many ships, rescue boats and helicop- number of separate telephone channels. Texaco's Tartan platform shut down ters were involved in the rescue which It also transmitted process data for a gas export about 10 minutes after the followed; radio traffic became very computerized system which provided initial explosion because its operators heavy, making communication difficult. each platform with an overall view of detected an increase in pipeline press- A year later, Lord Cullen's inquiry pipeline operations. ure caused by a valve closing on Piper continues to probe the terrible disaster. Piper Alpha was the focal point of the Alpha. Witnesses have given evidence about communication system. with line -of - According to the interim report, pro- communication problems experienced sight microwave links radiating to Tar- cess shut -down on Tartan started at on the night. Improvements are being tan, Claymore and MCP01. 22.45 and preparations to reduce press- made to another Occidental Petroleum Signals from Tartan and Claymore ure in the pipelines started at 23.20. platform as a result of their experiences passed to Piper Alpha where they were When the work began, they found no and these have been outlined to the retransmitted to the shore either by a pressure - gas had already escaped to inquiry. tropo-scatter radio on Piper Alpha or by feed the fire on Piper Alpha. The inquiry heard that after the coast- retransmission to MCPOI. where there A witness said that they had a back- guard: picked up the Mayday they were was another tropo -scatter link to the up VHF on Tartan but "a lot of people frustrated by the lack of information. shore. The inquiry heard that after the were using it so there was very heavy Doctors who were sent to deal with the initial explosion on Piper Alpha. Clay- traffic". Texaco was in the process of incident had no idea of the number of more and Tartan could not he con- icstalling satellite communications on casualties. Furthermore, operators on tacted. the platform at the time. platforms connected with Piper Alpha Senior operators on Occidental's Alistair McDonald. Occidental's were unaware of the scale of the disas- Claymore platform told the inquiry that head of communications. said that in his ter. This delayed the shutting down of after hearing the Mayday and losing opinion it should be a statutory require- production and efforts to vent pipelines. their main communication link they ment to have hack -up satellite com- A network of pipelines joined Piper made desperate attempts to contact munications. Alpha with three other offshore plat- Occidental's headquarters in Aberdeen He outlined four major improve- forms. called Tartan. Claymore and by a hack -up satellite system; yet mean- ments for Claymore. including battery MCPOI: Piper was also linked with the while they continued production. hack -up for radios, the provision of Flotta oil terminal in the Orkney Witnesses differ as to the exact time radios at muster points, longer -range Islands. that contact was made, but it was some- lifeboat radios and a secondary control One important conclusion of the De - where between 30 minutes and an hour centre.

MCP 01

Gos to St Fergus Gas from MCP 01 Fngg

s ELM' TA IA PLOT / R1810th gas / 133 miles) RIPER Land line and 30 inch oil adío link Tirades) PIPER A

¿TARTAN 30inch oil \ (7 miles) ropo Alternative link tropo link MORMONO MlLL

ABERDEEN¿ OTérmina l flinch gas 111.5 milºsI Line of sight microwave link o Platform TARTAN

Communications links at the tinte of the Piper Alpha disaster. The pipeline system between the rigs.

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956 ELECTRON ICS WORLD + WI RELESS WORLD October 1989 WATHEMATICS AND ART Chaos, fractals and computers

Keith Wood explores a spectacular branch of mathematics which is exciting widespread interest.

For well over two millenia. tradi- snag is that we do not have a corres- at a population of 1. Eliminating R gives tional mathematics has served ponding armoury of mathematical tools z+, =(r+ 1)zn-rzn 2 us remarkably well for describ- for this data. ing and predicting natural phe- Electrical devices may pose similar A small deviation sn in z gives rise to a nomena. We have a long tradi- problems. as when a sample -and -hold small deviation in zn+, of tion of straight lines and smooth curves amplifier is an element in a feedback sn+I=(I-r)sn in our geometry, architecture, astrono- loop. How many people would seek out whence it follows that deviations will mical observations and much more. It is a faster switching amplifier so that the subside provided that 0

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958 ELECTRONICS WORLD + WI RELESS WORLD October 1989 MATHEMATICS AND ART

How the imaRes were made

The equations and descriptions are to be found in the text Here are the ranges of real and imaginary parameters. The total range will have to be divided by the screen resolution in each direction to create the grid of points for iteration. Fig. 3: Re-2to+2:lm-1.5to+1.5. Fig. 4: Re -1.33 to +1.33;Im-1.Oto+1.0. Fig. 6: Re -0.75250 to -0.71550: Im 0.19849 to 0.22624. Fig. 7: Re -1.773519041725 to -1.773519039401 Im 0.006836859946 to 0.006836861689. Fig. 8: Re -0.6754 to -0.3986; Im -0.1038 to 0.1038. The program used to create the figures is available from the author at 33 Glan Aber Park, Liverpool L12 4YP, England. Price is f15 inclusive. UK and Europe, f16 elsewhere, on 51 inch disk for PC. f1.50 extra for 31 inch disk. The program includes an editor with syntax checker for writing programs. a calculating section which uses a coprocessor if present and a display editor. The data file and picture file are both compressed to save disk space, and the program will run on most PCs with DOS 2.0 or higher and with 256K memory. It supports EGA and VGA displays. The data file can be expressed many ways without further calculation. Figures in this article were photographed from a VGA 640 x 480 x 16 colour display.

Fig.l. The Verhulst Equation. The ordinate is the dynamics of the normalized population and the abscissa Venhu1st Equation. the value of r. These plots were produced by taking a value of r and iterating for 500( years to allow the system to Fig.2 appears on rid itself of starting transients. The next page 963. 30(1 years' population figures are plot-

ted. Below r=2 the population is 1 for a . ,' f ., Ae 0 . , c . stable system. For 2

Another surprise concerns the ranges of r for which a certain mode of behaviour holds. If the range of r values over which doubling occurs is divided by the range of values over which quadru- pling occurs. the result is found to he 4.669201600910 .. Also, the range of period 4 divided by the range of period 8 has the same ratio. Furthermore. the same ratio is found in f the Mandelbrot set and in many other systems. This number is known as the Feigenbaum number, after the man who established its wide occurence.

The precision of the process is a 4 property of a mathematical expression; there would he a much more complex situation in a real world. Nevertheless similar behaviour is found in a variety of systems, including electrical circuits. If the above equation is implemented in hardware (using a sample -and -hold amplifier and analogue multiplier), the circuit behaves as described. Fig.I illustrates the dynamics of the

October 1989 ELE('TRONIC'S WORLD + WIRE LESS WORLD 959 MATHEMATICS AND ART

regions which develop as r is increased have windows which correspond as well. This repetition of a recognizable feature is a characteristic which will appear again and again. It is especially signifi- r 7 cant that the word "recognizable" applies here. Random data can be arranged to create a lasting impression on the mind, which is a pre -requisite for any analysis or hypothesis. Would the appearance of a contour within the chaotic region, on one side of which the probability of a result was higher than on the other, ever have been discovered from reams of printed data? fed Notice also that the structure of chaos becomes apparent only when very large quantities of data are presented. A few points calculated by hand look far more

. v a= random. Computers are essential because of the vast amount of arithmetic involved, and it follows that the method of display naturally centres on the monitor. Both these, coming together, are Fig.6. A bud from the Mandelbrot Set. a subset of period 15. (Fig.Sison p.965). responsible for opening up a whole new values. It also has windows. A window be derived and therefore it can't carry field of endeavour. at 2.828 has only three values, and as r any mathematical significance. The en- It will be obvious that to produce increases further each of these three velope of a band of chaos at smaller chaotic behaviour a non-linear function traces doubles to a total of six, then 12, values of r continues within the larger is essential. A linear one would move 24... area of chaos which develops at larger r smoothly and continuously in one direc- There are numerous other windows, values. tion towards zero or infinity. some so narrow that they look like The three traces in the window at The Verhulst example is a one- printer misalignment. Close inspection r=2.828 each have the same form as the dimensional case, the second dimension reveals a small number of values within whole of Fig. I. The window is ex- being used to plot the results deriving the window. The two bands of chaos panded horizontally by a factor of 8.5 in from the value of r. Two-dimensional which appear as r is increased meet at a the lower section of the figure. You will systems provide further revelations. population value of 1, the stable value. see that not only is the regular period This is pure observation; I doubt if it can data mimicked, but the small chaotic Julia and Fatou A feature of stepwise processes which are determined by iteration is that one initial value can generate a result after a given number of iterations, while another arbitrarily close initial value can generate an entirely different result. These two results may each be stable conditions, which is not chaotic; however, chaos will generally be found in some area covered by the process. A stable condition is one which is arrived at by iteration and from which the i sr process does not depart by further iteration. It may he a single value or a cycle of values which repeat. These condi- 7, tions are known as attractors. Another form of attractor is a closed contour which is finite, but within which a point does not repeat as iteration proceeds. Where two or more attractors exist for a process it follows that there must be a dividing line between the regions of influence of each of the attractors. Once again the idea was first examined long Fig. 7. A 500 000 000 times enlargement from the Mandelbrot Set. Location before computers were available. It was suggested by Dr DietmarSaupe. clear that in using Newton's method to

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October 1989 ELECTRONICS WORLD + WIRELESS WORLD 961 MATHEMATICS AND ART

Newton's method states that a better approximation to a root of the equation f(z) = 0 can be calculated from an inferior value with the expression f f(z) Zn+1=Zn-f'Zn) 9 n = 0,1,2,3... is . The method repeated until the result has as much accuracy as is required. Clearly, starting with a close guess reduces the amount of computation and . the wider problem considered here was . of an academic nature. Lord Cayley (1879) addressed the problem and found that the two roots of z2 -a = 0 had an easily defined dividing line which is the perpendicular bisector t case when complex roots are involved. The standard (or Gaussian) plot is to 0 put the real component on the x-axis t . and the imaginary component on the y-axis, though for artistic purposes any 11, other manipulation is equally acceptable. Fig.8. A typical cubic analysed by find the roots of an equation, the start- Lord Cayley failed completely to find Newton's method. Location ing value influenced which root was a solution with cubic or higher order suggested by Peitgen and Richter. ultimately found. The problem was to functions. They appeared to be imposs- Fig. 9. Newton's method applied to a determine the spread of values leading ibly complex. This makes the work of real function. to a particular root. Julia and Fatou (1918-20) seem particu- _. , , . . r) o º4:0 rn>á ;. +*, :: 149.L ' x' . y Y % . "' :. ti ' ^f ~ !:.

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962 ELECTRONICS WORLD + WIRELESS WORLD October 1989 MATHEMATICS AND ART

Fig.2. A selection of.Iulia Sets.

larly inspired, since they had no compu- where both z and c are complex. This being itself a member of the set. will be ter facilities to display and check their expression is quite general as all quadra- attracted to one or other of the available results. tic functions can he reduced to this form attractors. Points in the Julia set are Julia and Fatou looked at the general by substitution. One can generate a therefore all repellent. A cycle of values case of the regions of attraction in the wide variety of displays with it. the can only belong to the Julia set if any complex plane and determined the simplest being the special case of c=0. other point not being part of it is never properties of the division between them The Julia set is then a unit circle. attracted to it. Such cycles have a period

in terms of the set of points forming the To create a display, a grid of points is of I . The value z=1 on the unit circle is dividing line. This set is known as the allocated in turn to z and the equation is an example. and is known as a fixed Julia set. iterated. The outcome is displayed with point. One surprising result was that the set the points as pixel coordinates or printer Iterating a point within the Julia set of points forming the boundary of a dots. Since a point belongs to the Julia will lead to other members of the set; region of attraction was the same set set or it doesn't, monochrome displays since all are repellent this movement regardless of which attractor was in are quite suitable. must he random and therefore in consideration. While this is self evident Fig.2a shows the way the unit circle general chaotic. in the case of two attractors, it applies to distorts when the value of c moves away Figs.2c and 2d are of Julia sets of any other number of attractors. This from zero. It is still a closed curve with a equation 2. in which c=- I and might seem impossible, but the case of single attractor in the centre at z=0. For c= -5052+(1.5576i respectively. The three or more regions of attraction this set c has the value of 0.3I+0.04i. former has two loops which connect at sharing a common boundary will he Fig.2h is the Julia set obtained when each junction point, while the latter has illustrated later. c=i. This is a set having only one five. The loops do meet in this case; the The simplest non-linear function, and attractor. at infinity. The line represents error arises from the interaction be- therefore the most amenable to calcula- values that are not attracted to infinity, tween the method of calculation and tion and analysis, is the quadratic func- but it has no thickness and points on printer resolution. These sets have tion. Although general theories were both sides of the line are repelled. The attractive cycles with a period of two being developed, they were tried out thickness in the figure is an artefact of and five respectively: one cycle point with the equation the method of computation. lies in each loop round a common The concept of repulsion is a natural junction point. the one in the centre one if one accepts the contrary notion of loop being the value z=0 which is al- z + =z'+c (2) attraction. A starting point arbitrarily ways enclosed in these Julia sets. The n = 0,1,2.3,... close to a point in the Julia set. but not attractive cycle is not symmetrical.

October 19149 ELECTRONICS WORLD + WIRELESS WORLD 963 MATHEMATICS AND ART

A great attractor - but is it art?

Mathematical practice has been largely spawned emerge. vision and endeavour. l hey have a formula them- by Euclidean premises. Lines and curves are The study of iteration theory and fractals has selves. The colouring of displays requires consider- smooth, not a bit like nature. Nevertheless a lot of made inroads into situations which were thought able time and application if the result is to be important and relevant work has resulted from this impossible to characterise, and both theory and comprehensible, have impact, and transmit the ethos. experiment are making progress with the help of essentials of the message. That the message may While they seem to move in such a way, the the computer, which is the only way to process be scientific rather than cultural shouldn't matter. planets themselves are impossible to describe In enough data to show results. Computer output in There is certainly a great deal of aesthetic Euclidean terms. Why, for example does erosion the shape of dot printers and monitors has been appeal; there are far more hobbyists developing not make everything smooth? We say because of the other essential element in enabling human displays than there are scientists and mathemati- local crustal variations and tectonic movements. comprehension of enormously large quantities of cians doing research. All that weight of application

Why do these occur? We say because of thermal data, by organising it in ways which turn out to look is bound to throw up an occasional discovery. I instabilities. Why are there instabilities? We say surprisingly appealing and memorable. have myself made a fascinating display with what

because of crustal variations. Or, perhaps there Beside population dynamics, the Verhuist equa- turned out to be a programme bug. I know the hasn't been enough time for initial disturbances to tion has been found to apply to some aspects of cause and will be programming it properly to see lie down. Will they ever? Do we have a chaotic turbulence and chemical dynamics. Much is known what can be done with it. This was sheer luck, most situation which is constantly on the move yet which about complex functions and Julia sets, but as yet bugs create much worse chaos than the subject! manages to stay within limits over the long term? there is much less known about real functions, and Another use of fractals is commercial art. For Mathematically we now find that such a scenario is rules may not be generally applicable. One thing mountain ranges, seas and skies the motion possible, even though the simple demonstrations does emerge in nearly all cases, that chaos occurs picture artist is turning to the use of transforma- are far from application to the real world. Perhaps in the region where two conflicting processes tions. There is considerable scope for human one day we will be able to apply new and distinctly meet. intervention with this method. One can liken it to different theories to familiar situations. The displays which have done more than any conducting an orchestra, a few directives and a The climate is a clear example of a chaotic other single development to excite interest in the guiding hand as the work proceeds produce a situation, yet we know general patterns and limits subject have crossed the borderline between result which owes a lot to the concept of the artist. which place a broad restriction on unseasonable science and art. Elitists maintain that anything Over the last couple of centuries a wide gap has weather. Now that it is clear that chaos is not produced from an equation by a computer cannot developed betwen science and the arts. Perhaps necessarily total, new methods of prediction may be called art. Art must be a manifestation of human the fractal can reverse the trend.

As c is increased further in equation value for q (4 in this case) yields plenty hours. The result is usually a striped 2, the resulting Julia set in not con- of interesting results. display such as that in Fig. 3. nected. When c =-1.25+0.136i, (Fig. Attractive points or cycles have their 2e), the Julia set is of the type which has regions of attraction, and it is instructive been called Fatou dust. Those c values Level sets to colour these differently so as to for which the Julia set is connected The complementary set to the Julia set illustrate the extent of each region. constitute the Mandelhrot set. The unin the complex plane is called the Fatou Fig.4 shows the Julia set of Newton's connected set has only one attractor; set. It is normally very large compared method applied to there is no interior to the set. to the Julia set and in order to examine it Figure 2e looks as though it ought to we must split it up into manageable f(z) = z3 - 1 have an interior. This is because the portions. One way to do this is to take a dust points are of no size, and the small arbitrary radius centred on an roots -1, 0.5 ± V3 chance that any of them fall on the grid 2 of points used for calculation is remote. and there will be three regions of attrac- The easiest method of display is to select There are tion. As mentioned earlier, one of the a level set closely surrounding the Julia properties of the Julia set is that it is the set and to display that. One can create a numerous boundary of each of the three regions of map of several such level sets by colour- attraction. How this appears in practice ing them. Figure 3 illustrates the same windows, some so can he seen in Fig. 4, where each region Julia set as Fig. 2e in that way. While a small that they has a different colour. Each point in the level set is strictly the set having a Julia set is a three -colour point, a chain unique number of iterations, a map of look like printer of islands bounds each region, and each many level sets can be confusing. island is itself bounded by a chain of Finally, Fig. 2f depicts a Julia set of an misalignment" islands, and so on. entirely different equation. The mathe- Complex functions seem to be re- matical models of magnetic domains attractor and count the number of itera- markably well-behaved when it comes developed by Yang and Lee can be tions required to move from the starting to creating a display. The stripes in Fig. examined this way. It is of interest to value to within the circle represented by 3 seem to suggest a smooth progression plot them in the complex plane to see this radius. All starting values requiring towards the attractor in a manner sug- whether the known properties of such a given number of iterations constitute a gestive of walking down a flight of steps. sets cast any further light on them. It level set of that order. When the attrac- Actually, the movement of a point with turns out that they exhibit the same tor is infinity, it is convenient to count successive iterations jumps around the convoluted structure. The Julia set of the iterations required to exceed the map, happening to land in just such a Fig.21 is of reciprocal of the radius. way that the regular steps are created. To display the collection of level sets In spite of this, the progression is not 12 in a mapping of the function, the most chaotic because the attractor ultimately xn+ = {xn2+9- 2x+9-2 instructive and appealing method is to collects the ongoing iteration in a de- colour them. One can colour each set fined situation. where x and q are complex, but a real with a contrasting colour to its neigh - Other methods of calculating Julia

964 ELECTRONICS WORLD + WIRELESS WORLD October 1989 MATHEMATICS AND ART

Fig.S. The Mandelbrot Set n outline. sets, such as iterating backwards, yield can he reduced to a form with one definition includes sets like Fig. 2b multiple results at every step, all of constant. It was B.B. Mandelbrot who which are a special case. which have to he followed up. Inverse thought of extending the studies to the The Mandelbrot set is shown in Fig. iteration does not fill the whole set, complex plane, and who had computer 5. To the left of the main cardioid is the some parts being preferred. Further facilities available to him. The rest, as biggest bud and to the left of that is complication arises in the attempt to they say, is history. another bud, and so on beyond the overcome this. Julia sets are calculated The Mandelbrot set is derived from resolution of this printout. The ratio of this way, but larger, faster computers equation 2 with the difference that diameters of the biggest bud to the next are required. Even so, the method whereas the Julia sets for a quadratic is the Feigenbaum number again, and depends on the convenient behaviour of polynomial were calculated for a fixed similarly for the successive buds. Not the function being iterated. Some func- value of e, in this case the value of c is only that, but the tiny Mandelbrot tions may not exhibit gradual progres- varied. Those Julia sets illustrated the shape on the antenna to the left corres- sion away from the Julia set in terms of outcome of iteration of a grid of starting ponds in position to the main window in level sets and they may not be open to us values for z (z plane). We now look at the Verhulst plot (Fig. 1). Perhaps this yet, though the theoretical results which the result of iterating the same value of z is not as surprising as might at first have been proved for complex sets will (zero) with a grid of c values (c plane). appear, since they are both quadratic hold. There are two attractors, one of which is functions. infinity. The other attractor varies The appearance of the set suggests The Mandelbrot Set according to the value of c. The Man- immediately that it might be broken The quadratic function has been exten- delbrot set is defined as those values of c down into a number of subsets, such as sively studied since it is the simplest and whose Julia sets are connected. This the main cardioid and the attaching

October 1989 ELECTRONICS WORLD + WI RELESS WORLD 965 MATHEMATICS AND ART

buds. The corresponding Julia sets have ceed to infinity. but which does not dimension. If the mapping to he co- attractive cycles with a periodicity of I, include z=(1 as a fixed point. These sets vered is in more than two dimensions, it 2, Where the cycle has a period 3.... of are connected, but have no interior. call he thought of as being enclosed to I it is a fixed point at It he z=0. can They are a limiting case between the set any number of dimensions. More than shown that the values of c such yielding with an interior and the unconnected three is not easy to visualize because we a cycle are given by set. Starting from z=0, iteration pro- are used to linear methods of presenta- ceeds until the nth iteration equals the tion; mathematically they are just vari- 2( 2) (n-k)th. The first time this happens ables. defines values for n and k which can he Mf(z)) used to characterize the situation. u = For example, with c=2. successive and this defines the main cardioid hear- iterations produce the series ing the number 1 in Fig. 5. 0,-2.2,2 ... so that n=3 and k= I The test of the Julia set starts at z=0 This value of c lies at the tip of the main in each case, so that the process is antenna of the set. Referring to equa- OBITUARY represented by tion 3, this case is represented by O-->c->c3+c-+c'+2c3+c2+c-> ... (3) c4+2c3+c2+c=c2+c Since z=(l is a part of the cycle. these whose roots are 0 and -2. quantities lie on the attractive cycle for Professor William Where n=4 and k= I the roots are 0. the Julia set, it and follows that the cycle one along the main antenna and -0.228 Shockley having a period of two requires that ±1.1I5i which are the tips of the two 0=c2+c traces which reach the farthest from the Professor William Shockley, one of the team that

which has I . invented the has two roots, 0 and The zero real axis. Values n=4 and k=2 produce transistor, died in San Francisco aged 79. He and root has already been dealt with. and c values for the tips the next his two colleagues, John Bardeen of two most and Walter the other root is the centre of the largest Brattain, demonstrated the first point - prominent side traces at c=±i. The contact transistor at Bell in December, 1947. bud, which has a radius of 0.25, and process continues indefinitely and the Profassor Shockley's intention was to develop an encloses those c values giving rise to points are known as Misiurewicz points. amplifying semiconductor device based on the field attractive cycles of period 2. Such a effect, ran Julia The largest side buds have a but into difficulties. During the process of set was shown overcoming this in Fig. 2c. branching antenna attached. Two arms problem, the bipolar type was Similarly. invented and was closely followed by a working 0=c4+2c3+c2+c has lour reach out and a third the connects junction transistor, using layers of germanium branch point to the bud making a three instead of the metal contacts, early in 1948. It was point star. This is the size of the attrac- only about five years later that the team discovered "Put another way, tive cycle of the associated Julia set. how to reach its original goal - the field-effect Proceeding round the main cardioid transistor. the whole set In 1954, Shockley founded the Shockley if towards the cusp, the next largest is of Semi- conductor Laboratories in California and effectively order four, then six and so on. Going covered the began the complex of industry now known as Silicon the other way, towards the principal valley. British isles, this period 2 bud, are the odd -numbered Professionally, Shockley's reputation is secure, buds. Fig.6 is an enlargement of the but his unorthodox views on race and genetics, and shape would still period 15 bud. his disconcerting habit of recording almost every conversation he had with anyone and later produc- be much less Fractals ing the transcript either in evidence or to save himself the trouble of repeating it, did not endear than a single Fractals can be defined in two ways. him to those who tried to work with him. One way is the visual aspect uncovered The latter part of his life was spent at Stanford dot from a laser by B.B. Mandelbrot. which highlights University, where he became Emeritus Professor. the self -similar aspect of the displays. A He leaves his second wife and two daughters. See also Pioneers: Shockley, Brattain and printer" nearby structure has a similar appear- Bardeen, Electronics & Wireless World March ance, a magnified image likewise, so 1988, p. 273. roots, 0,-1.755.-0.123 ±0.745i. The that it is not possible to tell by just centre of the tiny Mandelbrot shape on looking what magnification a feature the main antenna is -1.755, and the two has. By way of example. Fig.7 is of a largest side burls are centred on -0.123 small part of the Mandelbrot set. The ±0.745i having a period of three. This familiar shape at the centre is roughly 5 process can he continued indefinitely. x l0t t times smaller than the main The point at which the principal bud figure. Put another way, if the whole set attaches to the main cardioid has the covered the British Isles, this shape internal angle 1/2; the points at which the would still he much less than a single dot largest side buds are attached have the from a laser printer. angle ±'2: and period 4 buds attach at The formal definition is that a fractal ±t/a (the remaining period 4 buds are is any figure whose Hausdorff dimen- not on the main cardioid). The denomi- sion is not an integer. If a map is covered nator in the fraction is the same as the by small discs the number of discs period of the attracting cycle. required will vary with the size of the Another concept is that of an itera- disc. The slope of the relation linking tion which starts at z=(1 and proceeds to the number and size is. in the limit as an attractive cycle which does not pro- disc size is reduced, the Hausdorff

966 ELECTRONICS WORLD + WIRELESS WORLD October 1989 ACTIVE r

Asic modular controllers to be supervised and programmed by a standard PC, a dumb Function -specific PLDs. Designed for high- a modem. speed (25MHz and faster) pipelined micro- terminal or remotely from Rhopoint, 0883 722222. computer systems, the 85C508 programmable address decoder with an STD-CMOS system. The XTP-DOS is a on -board latch is said to be the industry's wide-/temperature/low-power:STD-c-mos first c-mos 7.5ns PLD. Intel Corporation (UK). system which 793 696204. is capable of withstanding temperatures ranging from -40:0 + 85°C. It can be used in battery -based ap Jlications C-mos gate array family. A semicustom IC and consists of an STD -DOS equpped service for a family of low-cost metal -gate ZT88CTO8 single -board control er with the c-mos gate arrays in complexities ranging optional ZT88CT25 expanded rr emory from 15 to 660 gates is available. system and the ZT88CT4I quac serial Manufactured by EM -Microelectronics interface. Wordsworth Technolc y 0732 Marin. the CROSSMOS semicustom devices 866988. are suitable for low voltage (0.9 to 10V) and high voltage (3 to 18V) applications. MCP Electronics. 0734 772345. Linear integrated circuits o Over/under voltage detector. The Maxim (' Programmable gate array. A bipolar ICL 7665 dual over/under voltage detector is programmable 1800 -gate array, the a c-mos single-chip device that operates PLHS502A, has 20 dedicated inputs, 16 from any voltage between 1.6 to 16V. draws dedicated outputs and eight bidirectionals. a current of 3 microamps and offers a independent clocks, 64 fall -back terms and threshold accuracy of 2%. The 7565 has a 16 buried flip-flops. The output of each gate propagation delay of 75 microseconds. The and flip-flop folds back on itself and all other trip points and hysteresis of the:wo voltage VMEbus digital signal -processor from Data Beta gates and flip-flops to achieve total detectors can be individually programmed interconnectivity of all logic functions. Philips with external resistors to any voltage greater Components. 01-580 6633. Ram cache modules. A fame y of high available in frequencies ranging from 4 to then 1.3V up to several hundrec volts. 2001 speed c-mos static ram cache modules 24 M Hz. MCP Electronics, 0734 772345. Electronic Components. 0483 742001. A -to -D and D -to -A converters supports IDT MIPS risc-architecture products. Directly compatible with the IDT Oscillators for TVROs. UHF carrier -wave 31/2 -digit converters. Two 31/2 digit A -to -D 16 -bit sampling A -to-D converter. 79R3000 CPU . each of these cache modules synthesis is the function of the RF converters offer on -board LCD (MAX 138) Incorporating a sample -and -hold amplifier includes a complete data and instructicn Monolithics range of saw hybrid oscillators. and led (MAX 139) display drivers, together and high -resolution converter in a single cache. They are available in 12, 16, 20 and They are claimed to be particularly suitable with a built-in bandgap reference. In addition. package, the AD 1380 analogue-to -digital versions, with ¿K. for the devices a 25MHz cache depths of satellite television receive -only contain charge -pump voltage converter guarantees a maximum 6 - which 8K or 12K. Microlog.04862 29551. applications. A voltage -tuned version is inverter allows measurement of both microsecond acquisition time and 14 - capable of precise narrowband tuning over a positive and negative input voltages while microsecond conversion time, providing a Optical devices 150 p.p.m. range. The standard range operating from a single power supply voltage throughput rate of 50 kHz. Maximum Fast A high-speed operates at specified frequencies up to (+2.5V to +9V). Dialogue Distribution, 0276 specifications include ±0.1 % gain error, optocoupler. 1 5GHz with a tolerance of better than 100 682001. ±0.05% bipolar zero error, ±0.003% opt ocoupler family, the H1 I G 1,2/3, p.p.m. Quantelec. 0993 776488. linearity error and z 003% differential features a collector -to -emitter breakdown Low -power converter. The Teledyne voltage of up to 100V minimun at I mA linearity error Analog Devices 0932 253320 Power semiconductors Semiconductor TSC820 and TSC82 1 are Having a pf-otodarlington ouput. the HI IG low -power c-mos measurement system ICs Monitor chip for vehicle lighting. When series has a high current trans`er ratio of up Current sampling powerMOS. which include analogue -to -digital converters monitoring light bulbs, the technique is to to 1000% and a low dark current of 100nA SensorFETS BUK793-60A and BUK795-60A and a frequency counter function. Two logic measure the voltage drop across a resistor ir maximum at V°, = 80V. Switching times are are PowerMOS devices which provide a inputs drive LCD annunciators for high and series with the lamp circuit. The TLE 4951 is t, and ( of5and 100 microseconds cost-effective means of current sampling by low logic input levels. A peak hold input a monitor chip which requires a lower respectively (R1 = 100ohms). Isocom dividing the load current into a power permits the highest readings to be held and voltage drop across the series resistor, Components. 0429 863609. component and a much smaller proportional displayed. Trident Microsystems. 0737 producing no perceptible decrease in light sense component which can be monitored Optocoupler. The HP HCPL-2231 is 765900. intensity of the bulbs. Siemens, 0932 75 across a signal -level resistor (the sense optically coupled, dual -logic gate capabe of 2323. current is about 1/1500 of the power Interfaces providing logic compatible waveforms current). Philips Components. 01-580 6633. directly - eliminating the need for additional STEbus interface. An Arcnet interface DC motor control. A series of monolithic wave -shaping. With a typical data rate o' board for STEbus systems, SARCO I. integrated motor bridges controls DC Function -specific PLDs. Designed for high- SMbaud, it is intended for high-speed logic pipelined provides a mechanism for STEbus-to-STEbus motors. These short-circuit proof chips work speed (25MHz and faster) micro- system isolation applications. Common system communications and opens the path at voltages up to 42V and currents up to 4A computer systems, the 85C508 mode transient immunity is 5000V/µs. at a for STEbus industrial control systems to be and are protected against over -temperature programmable address decoder with an common mode voltage of 300V. and -board latch interfaced to a wide variety of computer The 4A device. type TLE4203. employs an on is said to be the industry's propagatior delay is less than 300ns. Jermyn architectures. Arcom Control Systems. 0223 output stage without cross current, so that first c-mos 7.5ns PLD. Intel Corporation (UK), Distribution. 0732 450144. 411200. the speed of motors can be controlled by 0793 696204. PWM techniques. Siemens. 0932 752323. Optical -fibre multiplexer. The FC2200 3X/ Task -oriented VMEbus DSP board. The DBV56. a single- AS400 optical -fibre multiplexer is designed Eurocard, digital signal -processing VM Ebus 10V references. A family of 10V references for point-to-point. multiplexed. and star microprocessors board positions the i/o function on a the REFO1 series, providesa precise IOV operations with IBM 3X/AS400 or plug - Advanced CRT controller. Manufactured output while from a single 13V to separate daughter board, allowing the user operating compatible equipment. It can support uo to by Hitachi. the H063484.98 is for use at to optimise the i/o for each application. The 33V supply, and is a drop -in replacement for eight multip'exed and two individual point-to- 9.8MHz. Although the ACRTC was designed the Precision Monolithics REF01. It DBV56 directly couples to the i/o function uses the point data links, which may be housed ir the as a member of the 68000 series of board and avoids routeing the input data silicon -bandgap- principle to provide a same unit. Solution Data, 0706 82736. microprocessor peripheral devices, it can be around the VMEbus. By providing access stable output voltage with temperature used in many 8 -bit or 16 -bit computer - directly on to its Motorola DSP5600I variation. A voltage adjustment pin permits Oscillators and crystals designs. The ACRTC performs the key processor bus, the DBV56 allows fast data trimming the output voltage to exactly functions logical Dil oscillator. A universal clock oscillator in of drawing algorithms and transfer and avoids system bus congestion. 10 00V. Teledyne Semiconductor, 01-571 a standard 14 -pin dil package features a physical drawing. Impulse Electronics, 0883 Data Beta. 0734 303631. 9596. 46433. frequency range of 250kHz to 70 MHz and is available with frequency tolerances of Analogue control. A powerful modular ± 100, -150 or ±25p.p.m. The device Real-time Basic controller. RTC52 uses an computer -to -analogue control system. the Memory chips features an extended operating temperature 80052 processor and is intended for on- DGH 3000/4000. generates accurate 64K ECL ram. HM 100494.10/12 and range of -40 to +85 °C. Rise and fall times board program development with a terminal continuous outputs for motion control in HM 10494.10/ 12 ECL static rams that are 6ns maximum. Euroquartz.0460 76477. and software compatibility with the BCC52 robotic welding, proportional valve control, combine very high speed operation (I Ons product series. RTC52 has provision for etc. The system is fully compatible with the and 1 2ns maximum access time) with a Surface/mount crystals. The SX2050P 64Kbyte of memory using ram/eprom, 12 DGH 1000/2000 modular data acquisition power consumption of 650mW are crystals by M -iron combine AT -cut bits of TTL parallel i/o and one serial port. system and can be combined on the same organized as 16K x 4 and are available with technology with a high -temperature epoxy The serial port supports both RS232 and serial (RS232 or RS485) link. The simple ECL 100k or ECL 10k i/o levels. Hitachi package designed for use with high-speed RS485. J.B. Designs & Technology, 0285 serial communications protocol allows the Europe, 0923 246488. pick -and -place machines. The crystals we 68122.

October 1989 ELECTRONICS WORLD + WIRELESS WORLD 967 performance and ease -of -use problems power levels in excess of 110W, the NFS 110 associated with backplanes. page (GB). 0296 power supply from Computer Products 393200. Power Conversion offers output PASSIVE EQUIPMENT combinations of 5, ± 12 and -5 and 5, ± 15 Controls and sensors. A new 124 page and -5V at 110V. XP, 0734 572611. short -form catalogue covers eighteen ranges Connectors and cabling PCB keyboards. Keyboards incorporating of components: control relays, power PCB -based membrane keyboards with rear switches, motor starters and proximity Optical -fibre connectors. A 'super' version Radio communications mounted component assembly are custom - sensors. MTE. 0702 421124. of the Dri-Polish FL 3703 multi -mode optical - products designed and built by IGT, which specialises fibre connector offers greatly enhanced in complete packages from around 25mm x Production equipment Shielded enclosures. Euroshield performance standards. It is compatible with enclosures offer radio-frequency shielding 25mm to 8636mm x 5588mm. Designs can heaters. The Research Inc. Hotspot latest -II connectors and provides Spot the ST which consists of 1110mm wide, hot - be delivered in around six to ten weeks. range of short-wave infrared soot heaters mean insertion losses of 0.1 dB, compared to galvanized rigid -steel structural panels. No Industrial Graphic Technology, 0703 701881. can heat a small object or spot up to 2000°F the typical 1.0dB loss of other multi -mode wooden parts are used, and retightening of in seconds. Uses include small-scale connectors. Leetec, 01.852 2203. the panel fasteners is not necessary. Instrumentation soldering and unsoldering, for instance on a Modular panel enclosures can be tailor- Programmable 50MHz pulse generator. PCB. Thermal efficiency of the Hotspot Displays made to fn any existing containments. The Global Model 8500 is a 50MHz depends on the use of a reflector, which may Dot-matrix LCD driver. This 12C -bus c-mos Drelec, 0793 783137. instrument which is programmable either be shaped or cut to give the exact effect chip set is designed to drive medium - manually or via an IEEE -488 bus interface. required. Astro Technology. 04895 77233. multiplex -rate dot-matrix LCDs and The parameters that can be digitally set Consumes only around typically 20µA per include period, amplitude, pulse width, delay, Wire stripper. The Model RT 2 wire stripper and relays Chip. The set, types PCF8578 and PCF8579, Switches rise/fall times, duty cycle and burst. IR can be used for removing oxidation and will drive full graphics or character displays "Byte -wide" switch. HDMP-8 is an eight - Group, 0753 580000. other contaminants from component leads using between 1:8 and 1:32 multiplex and pole, double-throw. compression -indexed. between 0.001 in and 0.013in in diameter. can be configured to drive from 256 up to a snap-action switch with gold-plated, stressed Optical time -domain reflectometer. The Two conical fibreglass compounded wheels maximum of 40960 dots. Philips elliptical contacts. The contact mechanism Fiberlog OTDR is an aid for testing 850nm rotate at high speed to clean and polish leads Components, 01.580 6633. has fewer parts than conventional double - fibre links and systems used in short and with no risk of deforming or nicking the lead throw switches, allowing the HDMP-8 to be medium distance links, such as local area being cleaned. Eraser International, 0264 Miniature leds. A range of miniature leds built into high density package with 0.050in networks. It can be used for fibre or link loss 51347/8. provides an effecive surface -mount solution pin spacing. The 5 milliohm resistance is measurements, making accurate for indicating or illumination applications. transparent to circuit operation. Annulus measurements of fibre length, real-time SMD speed placer. Siemens has increased The Telefunken SOT -23 -packaged TLM 2200 Technical (Canada), 010 1 416 648 8100. splice loss evaluation, and for connector or the scope of the HS -180 surface -mount components are available in red, green and splice loss measurements. Lambda device placement machine by developing yellow, with a mean luminescence of Miniature mains rocker switches. A series Photometncs. 05827 64334. the type SP -120 speed -placer module, which 10mA. The TLMR has a dominant of sub -miniature rocker switches, the 20 0.63mcdat shares the layout, conveyors, feeders and wavelength of 625nm, the TLMY 594nm and series, has a panel cut-out size of only 15.9 x 1.3GHz counters. The PM6660 series of system control of the HS -180 machine and TLMG2200, 575nm. Synchro Services. 0782 13.0mm. It incorporates a sliding action counters has a new input option which allows hasa twelve -nozzle rotary turret capable of 633633. which wipes the moving contacts across the operation at up to 1.3GHz. There is also digit handling 20 -pin devices from sizes 0504 up fixed contact until the circuit break occurs at blanking on the PM6665: a feature that was to 501C. Siemens, 0932 752323. Filters the edge of both contacts, so that arcing formerly provided only on the PM6669. A affects only the non -critical surfaces. IMO Programmable filter. Sierra wide of other options includes the Power supplies choice 6444. has introduced the Electronics. 01.452 Semiconductor GPIB (IEEE -488) interface module PM9604, DC -DC converters. A new DC -DC converter SC22324, which is claimed to be the the battery pack PM9605 and the high - with independent 15V DC outputs. two dual Miniature relay. A miniature double-pole industry's first cmos universal stability MTCXO crystal oscillator time base from a Model 12Q15.050. operates source relay, the TRK22, is fully sealed filter IC to include eeprom monostable programmable PM9607. Philips Test & Measurement. 0223 of 12V DC and provides two isolated outputs to IP 67 and IEC 529 and tested to the memory. It consists of four, second -order 358866. The x is at ± 50mA each. 2in 2in module only of IEC 68-2-17. Bifurcated biquad, switched -capacitor filters, allowing specifications 0.375in high and is designed for low -noise switch power from filter eighth to be changeover contacts any even -order up the Thermocouple/calibrator. The 1089 instrument applications. Calex Electronics, 20W to 1.25A per contact at 150V DC. At an designed. Devices can, however, be offers simulation and measurement of seven 0525 373178. ambient temperature of 20"C, the relay cascaded for higher orders. Sierra types of thermocouple, including type N, mV, requires a nominal coil power of 0.55W and is Semiconductors, 0793 618492. mA and PRT to accuracies within 0.5-C. The A range of dual DC-DC converters. single, available in five coil voltages from 4.5V to microprocessor based instrument also and DC -DC converters with 2:1 triple -output 48V DC. Iskra. 01-668 7141. features keyboard entry and alphanumeric input voltage range, the UM 1100 series is Tv IF filters. Tv IF saw filters are saw LCD display. increment/decrement keys, based upon a half -bridge, high -frequency available for the tv standards M, N. B, G, I, D. non-volatile memory and timed memory- switching converter using mosfets at E H. The filters operate at picture and L, and scanning. Time Electronics. 0732 355993. 100kHz. Up to 30W of output power is Transducers sensors frequencies ranging from 32.7MHz for carrier derived from an encapsulatec, shielded Automotive sensing elements. A range of in France to 58.75MHz the SECAM 'L' system package measuring 4.56 x2.56 x 0.83in. potentiometric sensing elements designed NTSC'M' system. The for the Japanese Literature Load regulation is ± I% for sirgle and duals specifically for automotive applications. devices use a lithium tantalate substrate for Fuses. A leaflet shows the range of Pudenz and ± 5% for triples. Gresham Powerdyne, include throttle potentiometers, light wide -band applications. Toshiba Electronics fuses and complementary fuseholders. 0722413080. dimmers, position sensing and other control (UK), 0276 694600. Panel, printed circuit, and base -mounting functions. They are based on either polymer/ flame-retardant fuseholders are described, Power supply. Regulating down to zero load cermet or conductive -polymer ink elements. Hardware together with the BS approved ranges of from a single -input range of 85-264V AC at Bourns Electronics, 0276 692392. Keytops. Keytops from Digitran consists of a cartridge fuses from 32mA to 25A. Camden transparent cap which fits over the keytop Electronics, 0727 64437. itself. A label can be introduced between the two and easily interchanged as required. Backplanes. A technical application note Digitran, 0763 61600. discusses a number of common COMPUTER Global 8500 50MHz pulse generator Data communications Mass storage devices products Helical -scan tape rive. The MegaTape GT- 'I helical -scan tape drive with Ethernet adapter. The Longshine DG 1000 88 is a 2.3Gbyte The GT-88 8mm cartridge PLUS adapter is an Ethernet -based IEEE/ BI bus subsystem. provides of cache 802.3 local -area networking interface card backup system 256Kbyte In addition, cartridges written on the which supports IBM PC LAN. MS-Net and buffer. with ANSI Novell NetWare network operating systems. GT-88 are compatible the standard X3.27 for read/write tape format. It is plug -compatible with Novell's NE -1000 SM.us tot ea -al 0635 38008. Ethernet card at the hardware level. Decade Computers, 817788. Dataguild Distribution. 0256 Computer peripherals Repeater ICs. Complete PCM repeater ICs VGA colour monitor. The XC-1449C 14in an mg NEIti PMI RPT-86/87, for long-distance PS/2 -compatible high -quality colour monitor telecommunications systems. automatically from Mitsubishi has a 0.28mm dot pitch and optimize the signal level. deter mine if valid displays upto 256 colours on screen from a data is present and retransmit the signal. All possible palette of 262 144 colours. Other - the circuits required to implement a features include an XF-type gun for the complete repeater are contained within the focussing requirements of high-density single chip. Jermyn Distribution, 0732 displays and a diamond-coated (non -glare) 450144. screen. RR Electronics, 0234 270272.

968 ELECTRONICS WORLD + WIRELESS WORLD October 1989 - f I I I TRAINING SYSTEMS

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October 1989 ELECTRONICS WORLD + WIRELESS WORLD 969 'spyand associate Peter Lee Tracey, quartermaster, engineer of Wright, unveils the quiet and secret world of electronic intelligence gathering. He tells of his experience as a real -life Q.

. r J t

Night i.ciun in action. See p 971

970 ELECTRON ICS WORLD+ WIRELESS ORLD October 1989 ELECTRONIC SURVEILLANCE

Recently, a glossy brochure dropper. When Mittelman invented the who are suddenly willing to commit dropped on to my desk which device, he used a mouth organ to acti- their financial and research resources to extolled the virtues of a new vate the amplifier; its Mafia name was deelopment. The result is that British secret "bugging- device cal- therefore inevitable - the Harmonica surveillance gear is now supreme. led an Infinity Transmitter, Bug. Later. I shall describe a modern The initiative for the development of costing just under £10(10; I was urged to version of this device which, in its a new piece of equipment is often snap up this bargain before the pressure original form, is now considered infan- accidental. For example. in 1968 I de- of demand forced the price up. I have tile. veloped the hug detector Scanlock, since received many telephone calls That was the start of electronic sur- which is now on the market. It started referring to another device mentioned veillance; I intend now to look at the life as an automatic modulation meter in Peter Wright's book 'Spycatcher' - evolution and modern embodiment of designed by Racal engineers: when they something to do with flooding, I could the art of earwigging by electronics. showed me the prototype. I instantly explain the device or even build one. Until a few years ago, elementary saw it in its alternative application. The "new" device, the infinity trans- equipment was in use both privately and Racal was not interested in carrying out mitter, was in fact invented over forty professionally; today, that is no longer the modifications needed to turn it into years ago by Manny Mittelman, chief the case. In this field of electronic a detector, but offered me all the help I hug artist to the N afia (the world of surveillance, the British are years ahead needed to do the work myself, with the covert surveillance, as you see, has its of the rest of the world. This has nothing tutther assistance of other engineers. own bizarre argot) and the item men- to do with technical skill in the technical Another 'accidental' development tioned in Spycatcher was Wright's support units or the research laborator- came about as a result of a visit to favourite bugging tool. Both these de- ies. It has to do with money. Decca. Brigadier Bartley -Dennis vices worked on the telephone system. Companies of the size. and possessing showed me a system he was developing but did not bug calls. Bugging tele- the resources of Racal. Plessey and to measure vibration at a distance, using phones is childishly simple. but eaves- a laser. Part of the set-up was a radio dropping on conversation in a room is chassis with the speaker cone exposed. most certainly not. Bugging a room is the volume turned down so low that Figure I shows the circuit of the infin- nothing could be heard. The laser was ity transmitter, which consists of a mic- not simply a matter aimed at the cone with the intention of rophone module, audio amplifier and measuring its extremely small move- tone -controlled on/off switch. Room of fixing a ments. but the problem was that the audio energizes the microphone which vestigal cone movement was a hindr- drives the amplifier, the amplified sig- microphone under an:e: connecting an amplifier and nal passing along the telephone cable to the coffee table and speaker to the laser's signal -processing the remote listening post. circuitry reproduced the original audio. So that this illegal use of the cable hopíng for the best So was horn the first laser system to does not clash with legal conversations. detect audio. I wrote the project up and a switching circuit is used. The older handed the paper to the infant technical telephone systems work on two voltage Marconi do not find it attractive to enter support unit at Tintagel House. It was levels: when the telephone is not in use, an expensive design. development and instantly classified, but has been re- the level is nominally 50V; when in use, manufacturing process for tie relatively invented many times since then. nominally 9V. The device works only small intelligence market without con- Neither of these two devices would when the voltage is low at the control siderable financial inducement, and this have been made as a result of direct end and high at the target end - if the finance is, or was, not available to the investment: the money was never avail- target -end handset is lifted, the hug security services. Neither are these able. In these instances, the real invest- automatically switches off. organizations able to carry out the de- ment was made by Racal and Decca and To use the hug, the eavesdropper velopment work themselves. There is it still needed someone to spot the must gain access to the room in question also, of course, a reluctance to buy possibilities and force development. to install the device in parallel with the secret equipment on the open market telephone pair. Then. from a control (there is a story that a Home Office Lethargy point anywhere in the world, he dials department ordered bugs from a com- Public. and sometimes even profession- the target's number. The target pany in London and was discovered to al apathy and lethargy are perhaps the answers; the eavesdropper asks for a have done so when the company was greatest advantages possessed by the non-existent person; the target denies financed and probably owned by the sw'ing community. Even though the all knowledge; apologies are offered Mafia). In this atmosphere of impasse. opposition are well aware of the exist- and the target is allowed to replace his the technology did not advance quickly ence of the devices available. they still handset. Since the eavesdropper has and the world of surveillance conse- go on with their normal and nefarious control of the line and since he does not quently became crowded with crooks, activities without allowing for the possi- replace his handset. the F relay in the charlatans, idiots and dangerous oppor- bility that they might be hugged in their exchange is still 'in' and an audio path tunists. turn. Countermeasures take time, trou- still exists, unknown to the target. But all that changed, and the reason ble and money and sometimes they are At this point, the eavesdropper sends was Northern Ireland. The fight against too much effort. a tone along the line which is amplified the IRA and terrorist organizations Some time ago, when terrorist attacks by the tuned amplifier on the right of supporting them opened the treasury on aircraft began. a businessman Fig. I and used to switch on the mic- and techr.ical budgets are now massive. offered security equipment to airlines - rophone amplifier, the output of which The services are able to talk from finan- such devices as metal -detector door- is fed back down the line to the eaves- cial strength to the large companies. ways. After some effort, he gained

October 1989 ELECTRONICS WORLD + WIRELESS WORLD 971 ELECTRONIC SURVEILLANCE

Signal

C10)J

TIn

Fig. l . Circuit diagram of the infinity transmitter, developed for the American Mafia forty years ago and regularly re -invented.

access to the head of a major airline, from this the amount recovered from allay public anxiety". explained what he had to offer and was the insurance companies. Divide the The other problem with. in particu- promptly given the heave-ho. lie was result by the number of take -offs from lar, airline security is shown by the told not to waste any more time: it was any airport. The answer was $3 per experience of a commercial concern acknowledged that the equipment was flight. which set out to market an anti-terrorist worthwhile, and that airline security If, I was told, you can supply a totally system based on hidden cameras. To people believed such devices to be secure and miraculous system for less obtain sales. they set up a publicity necessary. but no orders were forth- than $3 per flight. you have a deal. In campaign, which brought enquirers coming. reply to my comment that the airline who needed detailed demonstrations. The reasoning went something like already spent a great deal more than One of the enquirers was a member of a this. Take the losses incurred by the that on the somewhat rudimentary sys- terrorist organization who went away airline over the last five years due to tem it was using. the airline head said and trained his colleagues to deal with criminal or terrorist attack and deduct "We have to go through the motions to the system. In this article. I shall describe equipment from the earliest to that available BUGS AND THE MAFIA in 1989, although readers should be aware that one or two deliberate errors In a far off land known as the United States through the files one of the searchers and omissions will make it difficult to of America, and in a small community in a discovered an order from a British Home copy the devices. town called Braintree, Mass., lived a Mafia Office department for a number of minia- family. This "family" was under surveillance ture RF transmitters (bugs). This "searcher" The telephone line by a law enforcement agency who one day had friends in the MI6 service and so not For those not familiar with the tele- hopped out of their prams in anguish at the surprisingly a copy of the order fell into the phone network, the old system is a discovery that the Mafia family were also hands of certain MI6 operatives. In the mechanical arrangement of moving "bugging". Too many bugs both law - cause of good relations and gentle leg - arms, contacts and relays and, as enforcement legal and private illegal in the pulling between MI5 and MI6, the MI6 already explained. based on voltage same area was not to be tolerated. Worse, operatives offered the document to Fleet levels. Two wires carry the audio and USA law forbade the design, manufacture, Street with the suggested newspaper AC ringing current. It follows that if you ownership, use etc., of any and all bugging headline: MI5 BUYS BUGS FROM THE connect a simple amplifier to any sec- devices except by law enforcement agen- MAFIA. tion of the wires and block the AC cies. Retribution was due upon the heads Unfortunately for those of us with a ringing current. you will pick up any of those who had provided these bugs to warped sense of humour the project was audio present. It can even he made the Mafia family. quickly killed and the headline never automatic by using the voltage swing to To cut a long story short, detective work appeared. So from the HARMONICA BUG start and stop a tape recorder. Simple! finally identified the bugs as British made. for the Mafia by Manny Mittelman, the first The real challenge is to use the tele- They had come from a "bug" supply house to use the telephone line to the FLOODING phone pair, to listen not to telephone with offices in London not far from Picca- bug of Peter Wright, also for the telephone conversations, but to conversation in dilly Circus. A police raid on the offices of line, to the Braintree Mafia bugs and the the room. Peter Wright's flooding or this company (now defunct) showed that it proposed newspaper headline, the bug- swamping technique avoided the need was, in fact, financed by the Mafia and ging business almost always creates to break in to the premises, since it used probably owned by the Mafia. Looking strange bed -fellows. the microphone thoughtfully provided Continued on page 975

972 ELECTRONICS WORLD + WIRELESS WORLD October 1989 PINEAPPLE SOFTWARE IN VIEW OF THE EXTREMELY

New New New SERIAL DATA PROBLEMS? New New New RAPID CHANGE TAKING PLACE A brand new program for IBM's and compatibles allows complete monitoring of two way data flow down any RS232 serial data line, DATACAP will capture and store data from 110 to 9600 BAUD and IN THE ELECTRONICS display n on screen or print it in such a way that it's direction as well as it s position in the data stream, is indicated. Applications include diagnosis of both hardware and software faults, and investigation of any problems encountered with handshaking protocols. It is also ideal as a teaching aid to demonstrate the ways in INDUSTRY, LARGE QUANTITIES which computers communicate. DATACAP £25.00 p 8 p free OF COMPONENTS BECOME BBC PCB Software REDUNDANT. WE ARE PCB is a powerful Rom based printed circuit board design program suitable for all BBC computers. A CASH second eprom is optionally available to add a powerful auto track routing facility to the program. This utilises a'rats-nest' input routine and allows any component to be 'picked up' and moved around the board without having to respecify component interconnections The full autoroute facilities are available PURCHASERS OF SUCH even on a standard unexpanded model '6'. 'PCB auto -route is remarkable. No similar software comes near the price: ACORN USER Aug 88. PCB manual track routing £85.00 PCB auto -routing £185.00 MATERIALS AND WOULD PCB plotter driver £35.00 P & P tree APPRECIATE A TELEPHONE IBM PCB Software C EASY -PC EASY-PC is a powerful PCB design program combined with a schematic drawing package. Up to 8 board layers plus upper and lower silk screens. Board size up to 17 x 17' Powerful CALL OR A LIST IF AVAILABLE. zoom and pan features. Suitable for IBM PC/XT/AT 8 compatibles with 512k Ram -£98.00 P 8 P free WE PAY TOP PRICES AND MARCONI TRACKERBALLS We now have an adapter available to link the trackerball to the Archimedes, to enable it to directly replace the Archimedes mouse. COLLECT. Bare Trackerball (No software) £45.00 BBC Model with software £59.00 P 8 P on Adapters to drive BBC Mouse software £8.00 Trackerballs Archimedes Adapter £19.95 £1.75 IBM model (serial interlace) £99.60 Trackerballs also available for other computers, please 'phone for details. R. Henson Ltd. MITEYSPICE, SPICE.AGE and ECA-2 21 Lodge Lane, N. Finchley, Three very powerful circuit analysis packages, Miteyspice is available for the BBC range of computers. and Spice.Age and ECA-2 for the IBM and compatibles. Spice.Age is a new product for the IBM range which provides facilities for transient and Fourier analysis London, N12 8JG. as well as D.C. and freq response performance Miteyspice (For BBC and Archimedes) £119.00 SpiceAge (IBM PC XT/AT 512k Ram) from £70.00 P g P free 5 mins. from Tally Ho Corner ECA-2 (IBM PC/XT/AT 256k Ram) £675.00 LCA-1 (Logic Analyser for IBM's) £450.00 Telephone: Pineapple Software, Dept WW. 39, Add 15% VAT Brownlea Gardens. Seven Kings. Ilford. to all prices. Essex.103 9NL. Telephone 01.599 1476. n 01-445 2713/0749 CIRCLE NO. 23 ON REPLY CARD CIRCLE NO. 7 ON REPLY CARD CONQUERING NEW HEIGHTS

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October 19119 ELECTRONICS WORLD + WIRELESS WORLD 973 RF EQUIPMENT LOW NOISE GASFET PREAMPLIFERS PHASE LOCKED SIGNAL SOURCES Aligned to your specified frequency in the range 30-1000MHz. Very high stability phase -locked oscillators operating directly on the Masthead or local use. signal frequency using a low frequency reference crystal. Phase TYPE 9006. NF 0.6dB. Gain 10-40dB variable. In the range noise is typically equal to or better than synthesized signal 30-250MHz £78 generators. Output will drive the Types 9247 and 9051 wideband TYPE 9006FM. As above. Band II 88-108MHz £78 linear power amplifiers and the Types 9252 and 9105 tuned power TYPE 9002. Two stage Gasfet preamplifier. NF 0.7dB. Gain 25dB amplifiers. adjustable. High O filter. Tuned to your specified channels in bands TYPE 8034. Frequency as specified in the range 20-250MHz. Output IV or V £102 10mW £120 TYPE 9004. UHF two stage Gasfet preamplifier. NF 0.7dB. Gain TYPE 8036. Frequency as specified in the range 250-1000MHz. 25dB adjustable. High O filter. Aligned to your specified frequency in Ouput 10mW £170 the range 250-1000MHz £102 TYPE 9182. FM or FSK modulation. 20-1000MHz. Output 10mW TYPE 9035. Mains power supply for above amplifiers £39 £248 TYPE 9010. Masthead weatherproof unit for above amplifiers £12

UHF LINEAR POWER AMPLIFIERS rM Tuned to your specified frequency in the range of 250-470MHz. 24V. + DC supply. ' o , 4, .1. TYPE 250mW input, 5 watts output £289 9123 .i watts £335 ?;1 TYPE 9124 2-3 watts input, 25 output TYPE 9006 TYPE 9002 WIDEBAND AMPLIFIERS FM TRANSMITTERS 50 watts RF Monolithic microwave integrated circuits in a fully packaged 88-108MHz. output microstrip module format. Full -wave shottky diode protected inputs. TYPE 9086. 24V + DC supply £945 Temperature compensated bias circuitry. Voltage regulated local or TYPE 9087. Includes integral mains power supply £1,110 remote operation. TYPE 9182FM exciter *75KHz deviation. Output 10mW £248 TYPE 9007. 1-900MHz. NF 2.3dB at 500MHz. Gain 20dB £150 TYPE 9008 Gasfet. 100MHz-2GHz. NF 2.5dB at 1GHz. Gain 10dB. r--, Power output +18dBm, 65mW £150 NF at 1GHz. Gain 20dB. TYPE 9009 Gasfet. 10MHz-2GHz. 3.8dB A Power output +20dBm, 100mW £150 lb: .. TYPE 9253. 40-860MHz. NF 6dB. Gain 30dB. Voltage output 100mV, 100dBuV, -10dBm £94 t a.

. --.7.1"" TYPE 9263 TYPE 9259 TELEVISION LINEAR POWER AMPLIFIERS Tuned to your specified channels in bands IV or V. 24V + DC supply. TYPE 9113 TYPE 9252 TYPE 9261. 100mV input, 10mW output £218 TYPE 9252. 10mW input, 500mW output £254 PHASE LOCKED LOOP FREQUENCY CONVERTERS TYPE 9259. 500mW input, 3 watts output £290 TYPE 9113 Transmitting. Converts your specified input channels in TYPE 9262 500mW input, 10 watts output £530 the range 20-1000MHz to your specified output channels in the TYPE 9263. 2-3 watts input, 15 watts output £400 range 20-1000MHz. 1mV input, 10mW output (+10dBm). AGC TYPE 9266 10 watts input, watts £1,585 controlled. Gain 60dB adjustable -30dB. Will drive transmitting 50 output for Amplifiers I amplifiers directly £356 See below Television in bands & Ill. TYPE 9114 Receiving. Low noise Gasfet front-end. NF 0.7dB Gain 25 dB variable. £356

TMOS WIDEBAND LINEAR POWER AMPLIFIERS TYPE 9246.1 watt output 100KHz-175MHz 13dB gain £108

, S Y r r

TYPE 9105 TYPE 9158/9235 TMOS RF LINEAR POWER AMPLIFIERS Tuned to your specified frequency in the range 20-250MHz, or your TYPE 9176 - TYPE 9271 specified channels in bands I or III. 24V +DC supply. TYPE 9247.4 watts output 1-50MHz 13dB gain £108 TYPE 9105. 10mW input, 1 watt output £230 TYPE 9051. 4 watts output 20-200MHz 13dB gain £108 TYPE 9106 500mW input, 10 watts output £284 TYPE 9176. 4 watts output 1-50MHz 26dB gain £254 TYPE 9155.1 watt input, 30 watts output £327 TYPE 9177. 4 watts output 20-200MHz 26dB gain £254 TYPE 9158. 5 watts input, 70 watts output £448 TYPE 9173.20 watts output 1-50MHz 10dB gain £308 TYPE 9174. 20 watts output 20-200MHz 10dB gain £308 TYPE 9271. 40 watts output 1-50MHz 10dB gain £616 COMPLETE TELEVISION RETRANSMISSION SYSTEMS TYPE 9172.40 watts output 20-200MHz 10dB gain £616 AVAILABLE TYPE 9235. Mains power supply unit for above amplifiers £164 All prices exclude p&p and VAT. RESEARCH COMMUNICATIONS LTD Unit 1, Aerodrome Industrial Complex, Aerodrome Road, Hawkirtge, Folkestone, Kent CT18 7AG. Tel: 0303 893631. Fax: 0303 893838

CIRCLE NO. 19 ON REPLY CARD

974 ELECTRONICS WORLD + WIRELESS WORLD October 1989 ELECTRONIC SURVEILLANCE

by the telephone manufacturer. But the problem is that when the target's hand- THE INFAMOUS EAGLE set is replaced, a switch (the hook - switch) most inconsiderately disconnects the microphone from the line. So a The most famous of all the known passive modulate it. But how to energize it and get technique was needed to by-pass the bugging operations is the case of the the speech out of the embassy? hookswitch. but without seizing the American Eagle in the US Embassy in The Russian answer was our old friend telephone line, which would be equiva- Moscow. This Eagle emblem contained a RF flooding. Send a concentrated beam of lent to lifting the handset and alerting Russian cavity resonator device which was RF energy at the resonant frequency the exchange. like a passive microphone, vibrated by directly at the Eagle and then monitor the Wright's swamping system used RF room sounds as are many normal room RF disturbance - phase modulation - to jump the hookswitch and make the objects. Speech causes air pressure to caused by speech modulating the resona- carbon granules in the microphone go change and air pressure will move objects. tor. Basically quite simple. So why is it not into a state of high excitement, which That is how a simple magnetic microphone used more frequently? could he done from a remote point and works. The Eagle device was a deliberate The problem is the immense power without needing access to the premises. action of introducing into the embassy a needed to get just a little energy into the The circuit shown in Fig. 2 is not the specially designed diaphragm cavity, bugging device. Modern equipment would whole story, since the exchange inter- knowing that any speech in the room would detect this power source very quickly. face circuitry is omitted. The purpose was to use an RF carrier to extract audio from the carbon microphone. Various types of modulation ly, the RF waveform was clean, sim- Scanlock. This is an automatic hug were considered. hut amplitude mod- plifying demodulation and reducing detector which provides AM. FM and ulation of the applied carrier at the RF beats with legitimate RF transmissions FM sub -carrier demodulation, in con- generator terminals. by the change in in the area. trast with many such devices which resistance of the microphone in re- The outcome of all this was that the merely indicate the presence of a car- sponse to room audio, was greatest and device would pick up normal room rier although some do possess was chosen. A level of 15OmV of RF conversation within a radius of about rudimentary demodulators, the per- was needed and the output impedance ant. formance of which varies between poor of the generator was greater than that of Countermeasures and abysmal. In essence, they are simp- the microphone: a modulation depth of It is possible to detect the RF carrier by ly field -strength meters, which respond 25% could be obtained by impedance means of an RF sweeping technique, but to Radio I as well as to the carrier from ratios of between 5:1 and 10:1 over a it is likely that the signal would not be a bug. Many are the stories of expensive frequency range of 30k1 Iz to 20MIIz. recognized. since no modulation would panelling or air-conditioning ducts The conflicting constraints of small appear in even the most sensitive sur- being demolished in an attempt to lo- hookswitch capacitance and distance veillance receiver. But there is an cate a bug, which turned out to he a between energizing source and target answer which will stop the earwiggers in standing wave on some innocent piece enforced a frequency of around 1M I Iz. their tracks: a (1.01µF capacitor across of tntnking, the origin being the dear In the method of excitation used, the the line terminals or across the mic- old BBC. drive circuit and line capacitance were rophone. It will cost about 50p. I con- Scanlock prevents this kind of grief. made a series -resonant tuned circuit, so fidently expect someone to invent one It is a receiver scanning from 10M1-Iz to that the RF at the load was increased by of these components and sell it for £ 10(1(1 20MHz and their harmonics at high between five and ten times. Additional - as an anti -bugging unit! speed. the strongest signal found being

* Select for resonance at operating freq. * " F 5 at resonance

12 127k 300 L3

30oNáj 250N Z1N198 To line :150p* g 180p 133k 2N2222 250y,1 2N2222 101 - - 186p 150p T To audio amplifier ISO 10n 1k5 10n 10n

OSCILLATOR RF STAGE TUNER -DRIVER DETECTOR a

Fig. 2. Spycatcher Peter Wright's RFswamping system, which used the telephone microphone to listen in to room audio.

October 1989 ELECTRONICS WORLD+ WIRELESS WORLD 975 ELECTRONIC SURVEILLANCE

BUGGING PARLIAMENT FOR 30 YEARS

Without doubt there is a growing threat to indi- that a person who 'improperly obtained' informa- ly resists (and suspects) any system of seemingly vidual privacy through the ready availability of tion using a device adapted for surreptitious bureaucratic control that involves licensing (for electronic surveillance devices. They are freely surveillance would have a legal duty to keep that example, the recent rejection of a dog licence to advertised in the press, sometimes euphemistical- information confidential. Any unauthorized use of control vicious dogs). ly as 'security products' or explicitly as 'little information that caused damage would constitute Many MPs, especially those on the political left, buggers', and their price (some devices cost less a breach of confidence, and be actionable through see a more sinister motive for this rejection, and than £50) has begun to make some MPs sense that the civil courts for compensation. claim that the Government prefers to keep the immediate action is vital to contain a growing The first piece of legislation in the UK that hands of the security services free from official menace. defined when and how individual privacy can be control. For example, if Younger's or Cran's recom- In practice, the use of surveillance devices has lawfully infringed using some electronic surveill- mendations into electronic surveillance were ever never been off the parliamentary agenda since ance techniques, occurred in 1985 with the enacted, the legislation must bring into focus the 1961, when Lord Mancroft introduced the first of a passage of the Interception of Communications thorny problem of when and how the state can succession of 'Right of Privacy' bills. By the end of Act. This act was introduced by the Government, legitimately 'bug' its citizens. Having been badly the decade the defeat of another privacy bill, following a ruling from the European Court which mauled and branded as illiberal and authoritarian sponsored by Labour MP Brian Walden, worried stated that unfettered telephone tapping infringed by MPs of all parties during the passage of the the Government enough to establish an official individual privacy, and was specifically limited to Official Secrets Act 1989 and Security Service Act enquiry. It was known as the Younger Committee address the Court's concerns. As a result, the act 1989, the Government is not eager to debate on Privacy and its comprehensive report into the was (and still is) criticized as being too narrow in another can of national -security worms, which such threats to individual privacy has stood the test of application (i.e. restricted to the official intercep- legislation would necessarily entail. time. tion of telecommunications and letters), and too To mollify some of the growing pressure, the With respect to electronic surveillance, and this lax with the official supervision of interceptions3. Government did announce, during a debate on included all aural and visual devices and subse- However, the pressure for legislation has still press freedom, the formation of a new privacy quent disclosures of gathered information, Youn- continued and, in the last parliamentary session, committee with terms of reference that may go ger's recommendations' were all -embracing. They November 1988 to July 1989, James Cran, Con- beyond the simple examination of the salacious called for a 'criminal offence of unlawful surveill- servative MP for Beverley, has hounded the Gov- activities of the tabloid press. How far this commit- ance by surreptitious means' and commented that ernment. In the presentation of his Control of tee can examine new issues, or whether it will 'as incitement to commit the offence would be an Electronic Surveillance Devices Bill°, he has called merely repeat the ground covered by Younger, is offence', the sale of unlawful surveillance devices for a strict regulatory regime that would require a as yet unclear. However, given a thirty-year record through the advertising of 'their aptness for sur- licence from the Home Office to sell, manufacture and two official reports buried under ten or more reptitious surveillance' could also be penalized and buy surveillance devices; unlicensed behaviour years of dust, there are many who believe that the through the criminal courts. would automatically be a crime. Although the classic definition of a committee as being 'the The Committee argued strongly that new crimin- Younger Committee rejected a system of licensing place where controversial subjects go and get al penalties were necessary, to ensure that once as 'unworkable', Cran believes that this is the only buried' is being employed. surreptitious surveillance was suspected, the effective way to send a clear signal to the whole Chris Pounder aggrieved individual could call upon 'the resources community that the invasion of privacy by these References of the police' to investigate and prosecute offen- devices will not be tolerated. I. Report of the Committee on Privacy, ders. They reinforced their criminal law proposals The Government rejects this view and believes paragraphs 562-570. Cmd 5012,1972. by suggesting that the courts be allowed to award that regulation cannot control the use of electronic 2. The Law Commission ('Breath of Confi- compensation to individuals who suffer damage surveillance devices5. According to Tim Renton, dence'), paragraphs 6.35-6.46, Cmd 8388, through the use of information gained through such the Home Office minister who has been responding 1981. surveillance. to Cran's frequent initiatives, either the draft law is 3. See the 2nd -reading debate on the In- Although Younger's recommendations were worded too narrowly, in which case the next piece terception of Communications Bill, Hansard, never enacted, the civil law recommendations of technology is outside the law, or the law would col. 151-261, 12 March, 1985.

were taken one step further in a second official be drafted too broadly, in which case the applica- 4. 1 lansard, column 872, 10 May, 1989. report, this time from the Law Commission2. In tion of the law could become unreasonable in 5. Hansard, column 187, 13 March, 1989. their draft legislation, the Commission suggested operation. In addition, the Government consistent- 6. Hansard, column 593, 21 April, 1989.

fed to a demodulator. Signals of One area in which it is possible to But do not forget that industry has a IS(IOMHz have been located in this way. make interception especially difficult is tendency to go home at 5.30 p.m. and The theory is that the bug provides the the radiation from computer monitors, also that any captain of industry staying strongest signal in the room if one is which is easy to detect and reassemble late at the office might he using the only close enough to it and Scanlock locks to anywhere in the immediate vicinity of a working computer. that signal, which can he identified. building. Most circuitry within a compu- The use of a Faraday cage, while Public broadcasts are thereby elimin- ter is of a synchronous nature and most effective, would he unwieldy. Rut an ated. of the communication between PC and alternative to the CRT - the gas plasma screen and PC and printer is a serial data display - is effective in reducing screen Tempest stream. If it is possible to receive the emanations. While a CRT is continually This is security service jargon for elec- data stream. it can he decoded to a being refreshed, the gas plasma display tronic eavesdropping of data and character stream in much the same way only updates pixels when necessary, the speech. which has been known to occur as standard PC serial communication. It resulting radiation being largely unin- in the world of commerce but which is also possible to capture the data telligible. These displays, together with mainly. because of the massive expense. stream from a keyboard, which means optical -fibre cables for data, make the is carried out by government agencies. that it is then possible to capture the theft of data considerably more diffi- It must he said that, if one of these keystrokes required to gain access to cult. agencies decides to intercept your radio confidential systems. or telephone communications, there is The way to heat this - or, rather. to Television absolutely nothing you can do about it stake it relatively hard - is to ensure During the last few years. vision has unless you wish to bankrupt yourself. that any computer which is processing been added to sound in the well -dressed Life can he made difficult for the 'sensitive' data is surrounded by masses spook's working outfit. In such systems, 'spooks', but there is no hope of beating of other computers or in the middle of the difficulty lies in concealment rather them. an industrial zone which radiates noise. Continued on page 979

976 ELECTRON ICS WORLD + WIRELESS WORLD October 1989 ELECTRONIC SURVEILLANCE

I á

=- -- - .., 1

1.3

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CS'., O35

A selection of devices available to the well equipped spy. (1, old-style video recorder and camera in a briefcase; t2) Sranlock bug detector; (3) video and sound microwave receiver in briefcase with 1.4G11z masthead preamp, radio control built-in; (4) scanner receiver; (5) 1.3GHz "how-tie"antenna; (6) new video and sound receiver using Sony Watchman and s variable -bandwidth 950-1750MHz PLL tuner; (7) Pressure Zone microphone; (8) and (10) single -channel VHF receiver; (9)simpleSSB tracking receiver; (1I) heavy-duty pulse target tracker; (12) PZ microphone; (13) body -worn microphone: (14) FM radio microphone: (15) personnel target tracker; (16) low-cost microwave TV transmitter; (17), (18), (22), (23) commercial lapel microphones; (19) parallel telephone transmitter; (20) series telephone transmitter without battery; (21) Canon camera with M911A night -vision lens; (24) Mullen lOOmW body-worn VHF transmitter; (25) sucker microphone; (26) phantom -powered line pre -amp; (27) line amplifier; (28) target tracker transmitter in a pen; (29). (30) Gem VHF and I. IGHz IOOmW and 20m W body, room and telephone transmitters; (31) infrared target tracker; (32) "visiting card" audio VHF transmitter; (33) Wild (1970) VHF pen transmitter; (34) "visiting card" tracker transmitter which responds to light; (35) TV camera with motorized auto iris: (36)scrambler module: (37) video AGC unit for long cable runs; (38) Antenna Eye main unit.

October 1989 ELECTRONICS WORLD + WIRELESS WORLD 977 ELECTRONIC SURVEILLANCE

"free covered country lane. nothing visible to the naked eye. Moonless night, but under open sky. Z nailed ere codj(j The"grain- in the picture is due to individual photon strikes. resolve the outline ofa vehicle hut no details. 11w light in the sky is reflected from a town some ten miles distant. Seeing in the dark

The M9IIA image intensifier. shown the M9I IA uses a channel plate photo - here coupled to a Canon AEI SLR multiplier. Since the secondary emis- camera, is standard issue to both UK sion is confined to localised channels, and US security services. It weighs the device can't he blinded by a single around 500g and runs for up to 12 hours bright light in its field of view. This from a pair of self contained AA batter- enables the operator to look past bright ies. It also incorporates an IR illumina- lights into the shadows behind them. tor for operation in total darkness. The technology originated as an aid to It is sensitive enough to detect indi- military pilots to enable sight of the vidual photons: its operator can see ground around searchlights without quite clearly even on the darkest of being blinded. nights deep in the country solely from The green colour is that of the output ambient light. This is at least 1110 times phosphor of the intensifier. All the better than the human eye. night vision pictures were taken using Unlike earlier night vision devices, 1600 ASA film, I/30th second exposure.

r- - Mlodern night vision devices can see past bright lights and ltu This picture was shot in total darkness using the "panic light - the shadows. built into the intensifier.

978 ELECTRON ICS WORLD + WI RELESS WORLD October 1989 ELECTRONIC SURVEILLANCE

Phase sh if t =antro Il er ti ----To IF/RF of 1st mixer receiver

FSK 4 SLG ,yr :emoC reg gen

1111F Local oscillator

Fig. 3. Block diagram of a spread- spectrum transmitter and receiver. The maximal -length sequence synchronizing code is separately transmitted on UHF. than in equipment supply, since small The problem is the lack of low -power spectrum: message screening: high - cameras and lenses are now on the transistors in the range of frequencies resolution ranging: and interference re- market. up to about I.5GHz. Devices for the jection. In days of old, visual surveillance was 900M1 Iz cellular telephone business ex- Spread spectrum transmission is re- often carried out from a van parked ist, but they seem to have difficulty in lated to the frequency -hopping type of close to the target. "systems- \crying reaching I.4GHz. Very insanitary operation used by the military to gain from holes bored in the side of a an to a transmitters have appeared as a result. protection against both detection and revolving roof ventilator modified to some of them being derived from the decipherment. A frequency hopper its the contain a periscope. Long periods of amateur television fraternity. The only constantly changes frequency. duty gave rise to predictable bodily way round the constraint is to move up receiver being sychronized to change discomfort, which could sometimes be frequency in step with the transmitter, alleviated by making a hole in the van sc that there is apparently an unbroken without the floor and parking over a drain! The vans Bugging tele- transmission. A listener were never totally secret: after a day of required receiver would simply hear a misery, it was common to hear a bang- phones is burst of noise as the transmission passed ing on the outside of the van and the simple the frequency to which he was tuned. voice of the target gleefully shouting childishly Instead of changing frequency. a that one could now go home! spread -spectrum transmitter changes But now, the briefcase camera has to military specified devices. which not phase in response to a code generated taken over. at least in following suspects only cost hundreds of pounds but can by a maximum sequence length gener- or even in private offices. A built-in often work up to about 6G1lz; some ator, with which the receiver is also microwave transmitter provides a signal clients mistakenly insist that. since the provided. In the receiver, a voltage - to a crew a short distance away. If the devices work in this region, that is controlled phase -shift network directed inevitable dropouts of the transmitted where they want to he and, since they by the code provides a reconstruction of signal are important. for example when are paying the bill, that is where they go. the original signal. court evidence is being gathered, then it The ideal transmitter is a synthesized. A synchronizing signal to ensure that is necessary to record the output of the frequency -modulated. 2W unit cover- the receiver is at the correct point in the camera, a process which initially was ing IGI-Iz to 2GHz with digital frequen- sequence is transmitted separately using performed by a stripped -down minia- cy selection, and a sister unit covering wide -hand FSK and frequency hopping. ture camcorder in the briefcase, but 2GHz to4GI lz. AM transmissions have Figure 3 shows a block diagram of a which is now done very well by those been picked up on ordinary domestic spread -spectrum system. nice people at Sony. I have already used television sets, as the very large their Watchman video recorder/ 'mother' and 'baby' in its pram found The Antenna Eye monitor, which will give three hours of when an elderly man discovered a pic- Keeping video and sound observation recording with batteries in the brief- ture of his own street while idly tunirg from a parked vehicle has been the case. round the band. He mobilized the subject of many schemes, some hila- When a transmission is needed. to neighbours and wrathfully descended riousand some plain stupid. Ideally. the provide real-time information to a hack- on 'muse'. who wisely fled - all sixteen vehicle should he a common saloon car ing team who might need to take instant stones of him. and, furthermore, unoccupied; a car I impassive passengers parked by action. I have found that the best fre- As regards detectability, support the full of quencies for omnidirectional covert spread -spectrum method, covering the the kerb for anything up to 14 hours a is pass work lie between 1.2GHz and I .5GHz. band 1GIIz to 2GIlz with a separate day not likely to unnoticed. The DTI allocation for this work is UHF frequency -hopping channel car- One of the methods tried was an 22GIIz, but this frequency is virtually rying the maximum sequence length adaptation of the endoscope used in useless for covert operation and has generator. Such a system would possess medicine; an optical fibre with a lens on little to offer for overt point-to-point selective address capability; code divi- the end is capable of having its tip working. sion multiplexing: a low -density power moved about in response to a control at

October 1989 ELECTRONICS WORLD+ WIRELESS WORLD 979 ELECTRONIC SURVEILLANCE

hidden in the aerial tube. An automatic iris is incorporated, BUGGING HOTSPOT driven by the level of video at a selected point in the camera. In the early days of covert Body Mic use, Colour is a problem, since the best some bad techniques were employed by colour camera available will only work non -technical staff. They took the simple at an illumination of 3lux at f/I.4. Since line that to get more range they could the Antenna Eye camera is rated at increase the power; so milliwatt transmit- about 1/8, its performance begins to fall ters gave way to watt transmitters, even as off quite seriously in anything less than high as five watts. Apart from the incon- bright sunlight. To provide surveillance a venient need to carry a tank battery, there in any possible condition. an image - was a painful consequence which many intensified solid-state camera specified operatives soon discovered. One old friend for 24 -hour operation is needed, which of mine, now retired, has a party trick of also must he fitted with an auto iris and a dropping his trousers to reveal a very neutral density spot to avoid damage to Fig. 4. Complete Antenna Eye assem- unusual burn mark in a very private place. the image intensifier. The use of an bly, with rotation motors and drives. Like many of his colleagues of the day he intensifier means, of course. that the was badly burned by the heat of a five watt picture will be in black and white, since waves all contribute to 'boominess': in RF device strapped to his skin. When under no colour intensifier exists. this business, perfect acoustics are not the influence of the happy juice he lets rip In addition to a monochrome image, the norm. Two microphones produce about his intended lawsuit against the the use of an intensifier also reduces such a remarkable improvement that it department for depriving him of offspring, resolution to around 2511 television is difficult to understand the commer- a failure he insists is due solely to the BWM lines, which is insufficient for the identi- cial spy's insistence on using only one. burning away his manhood potential. fication of subjects at a distance from Often, these people pay no attention to the camera. It must he said, however, bandwidth, noise, speed stability of the that Eyes are in use and have led to recording or microphone placement. arrests. On average. I am asked several times a the other end, so that it can he inserted Some over -enthusiastic correspon- week to process some atrocious record- in ones inside and look about to see dent to the 13I3C television programme ing. the result of bad microphone tech- what is wrong. The doctor looks Tomorrow's World thought it would he nique. through an eyepiece down the fibre. In fun to feed all this information to the Concealment dictates the use of small my application, I coupled the eyepiece programme, which broadcast it to the microphones and the fet-amplified type to a low -light camera, which fed a world; incorrectly, as it turned out, used in hearing aids are often em- transmitter. The system worked, but because the car aerial is not used as the ployed. Since they need a direct -voltage there were problems with installation in transmitter aerial, as stated. Neverthe- supply and usually have three terminals, a variety of vehicles. less, the system was compromised and they are not ideal for the purpose, but In the I986/87 solution to this prob- its effectiveness reduced. although it is the recorder or amplifier can easily he lem, shown in Fig. 4, a common telesco- still in use. modified. pic car aerial is used, the risk of some Room acoustics present problems too bored hooligan casually snapping it oft Microphones and rooms with phase cancellation of direct and being accepted. A very small right- Bugging a room for audio is not simply a reflected waves. The Pressure Zone angle lens with an automatic iris looks matter of fixing a microphone under the microphone goes some way towards sideways out of a 3min hole in the coffee table with chewing gum and overcoming this effect. as shown in Fig. remotely controlled rotable aerial and hoping for the best. There are probably 5, which shows the difference between sends its image down a length of optical more failures in this kind of operation the response from a badly placed, fibre to a camera concealed in the car. than in any other sector of this cowboy - phase -cancelling microphone and that If it is required to transmit the picture ridden business. from a PZ type. rather than rely on recording, frequency Most commonly. a single high -gain and aerial type are important factors for microphone is used, well away from the Body -worn microphones consideration. A preferred method is to speech. so that direct and reflected Microphones and their associated trans - use a I.4G1 Iz transmitter at around 6W in the car, transmitting to a nearby THE DISCOMFORT OF WATCHING roof -mounted receiving aerial, very like There was no favourite van, any van of the right size In the early days this consisted of little more than a all the other tv aerials. The signal is and shape would do. Certain individuals in certain funnel and a rubber hose but the rubber hose had converted to a lower frequency and police forces and certain security services tried to to go somewhere. To the occupants of the van this re -transmitted to a remote base. In this lay down guide -line laws dictating the choice and became a scene of high drama but to any informed way, the car -mounted aerial need only use of a particular van. But as the waves defied onlooker it became a scene of high comedy. be small and inconspicuous and yet the King Canute so the pressures of supply, availability The rubber hose had to go down a drain so the and urgency defied the rigid rule book. van had to park not only over a drain but in the right whole system will have as much as range Due to the limited technology available the vans position over the drain that the rubber hose could might be needed. had to be occupied and sometimes for long reach it. Life, however, just does not seem to favour The average subject for surveillance stretches, maybe more than 14 hours. This pre- the righteous, the antics involved in trying to look would not suspect that a television sented some major headaches: first the van had to invisible while trying to move other vehicles so that camera could he concealed in a car be large enough and with enough headroom for the the van could get in the correct position over its long suffering occupants to stand up and even chosen would form basis for a Mack aerial and, of course, he would he right, drain the more vital it had to be provided with toilet facilities. Sennett comedy. since it is only the fibre and lens that are

980 ELECTRONICS WORLD + WI RELESS WORLD October 1989 ELECTRONIC SURVEILLANCE

CLARITY - BUGGING IN STEREO

The simple introduction of twin microphones world for its supply of microphones. These tiny and twin audio circuits with moderate gain fet-assisted capsules require a DC voltage and creates the first quantum leap. The separation are often provided with three terminals, not between the two mics does not have to be always convenient if all one has available is two excessive. One technique which works very well old bell wires. However it is not difficult to FREQUENCY is to place one mic close to the operative's modify them to work on two wires, or rather (linear scale) collar on the right hand side and the other on the modify the amplifier or recorder. wrist of his left arm; in practice the arm is kept If time is short and you have to get in and out away and, as far as is possible, extended over a quickly, place one close to the noisy side of the table or chair or counter. This achieves remark- room and the other in the quieter part of the able improvements over the single channel, room. With a little more time and some prepara- single mic systems. tion, take with you a miniature tape recorder/ player on to which you have previously recorded This is the most commonly performed area of about 10 minutes of normal speech. Set the bugging yet it is the least understood by the tape player going at low volume in a position to commercial sector. More foul-ups and lousy simulate where speakers would be expected to recordings are produced than in any other sr: or recline. Then move about the room and FREQUENCY section of spying technology. listen through a single portable mic. With a little Wiring rooms poses different problems when experience and commonsense you will soon a microphone designed for high gain is placed in Fig. 5. On the left, the result of interfer- begin to "read" the response of each room and a position well away from the source of the know where to the mics. ence between direct and reflected waves put speech. room -boom is the major product. The "how" of placing mics is critical. A On the showing phase cancellation. Targets are not well known for providing perfect knowledge of acoustics would come in handy. right, the output of a Pressure Zone acoustic surroundings. You need to create a pressure zone and place microphone. As a start, no room should ever be tackled the mic capsule in the pressure zone lust above with a single microphone, two microphones in a the boundary where direct and reflected sounds body are, in mitters worn about the stereo set-up is the absolute minimum. combine effectively in -phase over the audible essence, identical to the radio mic- In the world of professional entertainment range. In a perfect room every wall and every rophone used by entertainers. In prac- recording engineers pay attention to bandwidth, surface would be covered with thick sound tice. the two systems are quite different. signal-to-noise, temporal stability and, most absorbing material, killing interfering reflected problem The problem common to both is the important, the spatial characteristics of the sound waves. The arises because sound signal. To record spatial characteristics, flected sound arrives at the microphone slightly proximity of a concentration of fat and you must start from a basis of using two or more delayed behind the direct sound. When these In its water (the body) to the aerial. channels. So why does the commercial spy two sounds combine at the microphone out of entertainment function, the transmitter world stick to one channel and consistently phase the result is phase cancellation of various need only possess enough range to get produce unusable results? frequencies, sometimes called the 'comb -filter the signal out of shot or oft stage, For purposes of concealment the electronic etfect'. This is the condition which produces whereas in its spying role it might need spy world turns, once again, to the hearing aid unnatural sound and distortion. to transmit to the nearest back-up crew. There is also the question of conceal- Portable system f= 35MHz f=45MHz ment; a stage microphone only needs to -20- n front of body -20- Portable system be neat and comfortable to wear. the at side of body Pocket sized and being insulated -15- -15- aerial hanging free - system from skin contact by clothing, but a G ldB) -10- -0- device used spying must be completely Portable system Portable system Pocket sized at side of body -5- in front of body system concealed, including its aerial, if the -5- operator entertains any ambition to stay 01 01 03 Ó9 0'2 03 alive. It may even need to survive a body search. ala -20 20 A covert device presents. therefore, Portable system f =57MHz Portable system f = 80MHz at side of body conflicting requirements - long range in front of body and in the early days, and concealment, -10- Pocket sized -10- Pocket sized increasing power up to as much as 5W system system Portable system was the only response to the problem. Portable system at side of body in front of body This, of course, presented the further problems of battery life and heat dis- 01 0:2 03 o-4 05 tl1 02 03 04 04 sipation, the 'heat sink' being, of necessity, the spy's body. f=153MHz Much work has recently been carried -20- Portable system out on the design of body -worn mic- at side of body rophone systems. but the type of equip- Portable system ment still being offered by commercial -20' in front of body Pocket sized security companies is very basic, little system thought having been applied to body loss, noise suppression absorption, path 0'1 0'2 03 0'4 05 of selectivity. Figure 6 shows data compiled by the Tesla-Popov Research Fig. 6. Diagrams from a report by the Tesla-Popov Institute showing the variation Institute in Prague. in aerial gain for different frequencies at different positions on the body.

October 1989 ELECTRONICS WORLD + WIRELESS WORLD 981 ELECTRONIC SURVEILLANCE

It is common practice to use FM, or kept under wraps in the immediate sometimes even FM -on -FM for the future. transmitter, possibly with inverse scrambling. In my view, it would be far Telephone tapping better to use the double-sideband, On the official level, tapping telephones BLUFF suppressed -carrier technique; Figs 7 is easy. An engineer known in the trade The best of the illegal squirrels carry false and 8 show large improvements in path as a 'squirrel', working in the frame BT passes which identify them as from the loss and power consumption over FM, room of the target's local exchange, Investigation Branch. If confronted they Additionally, of course, the need to simply links the target pair to another are trained to verbally attack. Should some provide a stable carrier for insertion pair connected to the 'Tinkerhell' tap- innocent unsuspecting telephone engineer into the received signal would make it a ping centre, wherever that is. Every accidentally bump into one of them the bit more difficult to reconstruct the time the target telephone is in use. the tactic will be for the Squirrel to instantly speech in an intercepted transmission. tapping centre receives the same in- hint at some serious criminal matter he is formation. There is no possibility of Bug detectors would find that the part investigating and demand to know how the putting a stop to this. of the carrier that might show up would luckless BT engineer fits into the crime; A method of detecting a tap might he look very much like noise. I have tested usually enough to get the BT man making a a tinge -domain reflectometer which all the commercial detectors I could find hurried exit. with a DSBSC transmitter and none of could be used to determine line length them could detect the device from a to the exchange; a tap would increase range of 30cm. Nevertheless, equip- the line length by the distance to the ment available to the security services tapping centre. Contrary to the impress- just upped the brickwork and moved ion would fare better. given by film and television, the the exchange and, ill any case, you can To make it almost impossible to de- tapper does not reveal his work by soon check that. If it turns out that the mysterious clicks on the line. Indeed, tect transmissions, there is a process, exchange is still there and still in opera- the technology to detect already under investigation, which de- telephone taps tion as your local exchange then the must he very advanced; and the process rives from work on interference sup- chances are that Tinker -Bell has a little pression in radar. In this field, the result is time-consuming and expensive. love affair going with you. of the process would be the conceal- You carry out this process every day Tapping by unofficial agencies is ment of one FM transmission inside the of your life. One day your TDR reads quite a different matter, if only insofar carrier of a stronger one. All attempts to vastly more than the eight or tell miles. as the tapper has no access to the find the weaker transmission will only Now, it is highly unlikely that they have exchange. Many techniques exist, find the major one. The difficult hit is. perhaps the most common being to obviously, extracting the information. } open a street box, identify the target The use of two microphones in stereo DSBSC pair and another pair going to a non- -Ill 150 would not only enhance intelligibility, m working telephone in an empty room á_14O nearby. The then but also allow the use of advanced am two are linked so that techniques for the extraction of signal u=130 the outgoing and incoming calls can he from noise - adaptive filtering. This is heard in the empty room, with the ó 120 not the place for a full description. but numbers of the outgoing calls. It is also an illustration will show the benefits to II 110 possible to connect a tape recorder, he had. á taped to the roof of the street box, to the Certain cars of a certain department -20 -40 -60 target part, but constant visits to change in a certain country are kept for the use RELATIVE AUDIO INPUT LEVEL (dB) batteries and tape would need to be of visiting dignitaries and are bugged. explained away. They have screens between the driver Fig. 7. Comparison between path losses To find the number of an incoming and passengers and the VIP compart- in double-sideband, suppressed -carrier call is not easy. With the older ex- ment has a radio/cassette player, which working and FM. changes, the concerted efforts of a num- is provided in the hope that the visitors ber of engineers in different exchanges will turn on the radio and imagine that were needed to trace the call- to its the sounds will mask their own voices. EFFECTIVE OUTPUT POWER origin. The process was seldom successful and Wrong! Zero 100mW 00 mW an 'unofficial' squirrel stands no 1200 chance at all. In a Three microphones are used - two in cc- modern electronic the VIP section 33 F exchange. on the other hand, the num- and one external. The b adaptive-filter computer is controlled az ber can be found in a matter of mil- cró 800- W liseconds. by the external microphone and radio r dr output to subtract them from the two r There is an expert alternative. This is s a parallel -connection crystal NBFM stereo tracks from the VIP compart- z ó 400- ment microphones. This system never ¢Q transmitter with its own onboard NiCd DSBSC fails and the resulting speech is crystal- battery pack and charging circuit; it is clear. o-_ commonly called a "Pole Job". As the None The ultimate in concealment must be Speech Tone name implies, it is normally installed at INPUT that due to Bill Edwards of the CIA SIGNAL the top of a suitable telephone pole and who, twenty years ago. showed me a is connected to the target telephone line system capable of being implanted in a Fig. 8. Output power against power pair and also to another innocent pair. tooth. Developments on the theme consumption in DSBSC and FM trans- Whenever the target telephone is used have obviously continued, but must be mitters. Continued on page 998

982 ELECTRON ICS WORLD + WIRELESS WORLD October 1989 Small in Size, . . , the new Analog Bargraph DMM's Big on Features, from SOAR. Competitively Priced. .

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Fred Myers describes Plessey's advanced GaAs MMIC process and two of its many applications: a radar component and a satellite -borne downconverter.

Fet -based GaAs monolithic microwave integrated circuits (MMIC) were first demons- Protection/passivation dielectric trated in the mid -1970s by Ples- Spiral inductor Transmission line MIM capacitor top plate sey and others. Since then the technology has matured into a proven ;fl, O O process commercially available from / 1/2/ Bond pad top many manufacturers. metal The MM IC. like manv other new Interlayer dielectric 13 devices, had an initially slow take-up O 'fl? r e', but it is now revolutionizing microwave Bond pad bottom metal applications, certainly to 21161-Iz and in the next few years. with enhanced technologies. probably to I(IIIGI-Iz. The revolution is comparable to that wrought by the silicon IC in the last 2(1 Metal -intrinsic -metal capacitor bottom plate years or so. MM ICs will replace large. bulky and expensive hybrid circuits, the microwave equivalent of the PC board. with small reliable and low-cost chips (at least in volume). Gate finger Interconnection transmission line Most GaAs MMICs are based upon the field effect transistor (fet). the ubiquitous workhorse of solid-state microwaves. This device is fabricated upon semi -insulating substrates, which have very acceptable microwave properties, Through GaAs via hole Mesa resistor and the material doping and depth are chosen to optimize the device's properties. In a discrete fet, performance can be optimized by adjusting the circuit Fig. 1. Plessey's AIM1(' process. cult designers to exploit fully the capabi- matching to a particular device: mater- lities of the medium. The gate length of ial variations. although important, can the fet here is 0.51.1m which allows the be tolerated to some extent. For an process to be used to at least 206 Hz. MMIC this is not so: every device and Fabrication technology The first level metal (Fig. I) is created every circuit must be identical time after Many manufacturers now offer either at the same mask level as the gate metal. time with no adjustment - one of the standard MMIC parts or a foundry resulting in all the critical dimension process's many advantages. service, or both. However. a proportion components being manufactured with Volume and performance require- of the processes used must be consi- the same sub -micron accuracy techni- ments call for such repeatability that ion dered little more than derivatives of a ques inherent in the gate process. This implantation is now established as the fet process: although acceptable for first level metal is used for capacitor industry standard. "Throughput of a first -generation circuits they have little bottom plates, gates. all underpass in- typical production machine (>30(1 'stretch' capability for the future. The terconnects as well as some transmis- wafers/hour) and doping uniformity process described here is a multi -metal/ sion lines and other passive compo- (--2%) make it close to ideal. multi -dielectric process that allows cir- nents. Inter -layer dielectrics are then

98-4 ELECr RON ICS WORLD + W I REI.ESS WORLD October 1989 MICROWAVE

placed on the water to separate the metal layers, planarize the wafer surface, provide the overlay capacitor dielectric and (if required) to passivate the active devices. Holes ('vial') are etched through the dielectric layers and filled with metal at points where connections must be made between the various metal layers. At this stage a thick top-level metal is added which contains the low -loss transmission lines, inductors, capacitor top plates. bond pads and other inter- connect features. The front -face wafer processing is then completed by adding Fig.2. Typical broadband low noise software package which will enable the a covering dielectric to act as a surface amplifier. engineer to produce complex ICs more protect ion/passivat ion layer. efficiently. The program Linmic+ is The most widely used MMIC dielec- proving particularly amenable to this led technique and is consequently be- trics are Si3N4, Si02 and polyimide, application. coming the common approach to vias. although Ta,OS has also been reported. Modern cad is so accurate that most The choice of dielectric depends on linear circuits (e.g. low -noise ampli- many factors. For capacitor dielectrics. MMIC circuit design fiers) can be expected to work satisfac- capacitance per unit area, thickness At frequencies between I and 20GHz. a torily on a single -pass design basis: only control and freedom from pinhole de- totally different design philosophy from one mask design and process batch fects are the main considerations. For that commonly encountered by electro- needs to be produced to obtain chips interlayer dielectrics which separate the nic engineers has to he used. At lower working to specification. Complex, first and second level metals, the step frequencies, elements are largely consi- novel circuits may require two or more coverage capability of the dielectric film dered as lumped (i.e. pure) L, C and R: design iterations, and cad engineers, is important in order to avoid short hut at microwave frequencies. distri- circuit engineers and technologists are circuits at crossovers. I lere polyamide is buted effects and stray coupling are very constantly striving to improve this posi- especially useful since it has a low important. making layout a vital part of tion. dielectric constant (=3.5) and can he the design. In other words, component spun on the wafer at typically 1µm geometry strongly influences the per- Examples of GaAs MMICS thicknesses (cf. Si3N4 at 0.21.m). formance. Going from an equivalent Many circuit functions over the fre- After front -face processing has been circuit to a finished layout is a complex quency range 3-30GHz have been suc- completed, the IC wafer is thinned and, iterative procedure requiring a con- cessfully realized as MMICs. Space if required. holes are etched before final siderable database for design. Because does not permit more than just a men- hack -face metallization and chip of the distributed nature of the chips. tion of these. Among circuits demons- separation. Thinning the wafer and only relatively simple concepts can he trated are backing with metal provides both a investigated by breadboarding the cir- amplifiers-small signal, broadband and ground plane for the microstrip trans- cuit using discrete devices: and. as in the power. mission lines and a controlled parasitic silicon IC industry, this approach to M M IC design is now virtually dead. image plane for the lumped elements. Low -noise Balanced IF/buffer IF amplifier Accurate control of the final wafer Prior to mask layout and mask - amplifier mixer amplifier thickness is essential to maintain accu- making, extensive computer -aided de- rate transmission line characteristic im- signs of the chips are carried out by RF pedances. Although GaAs can he thin- means of such software as Supercom- 58-71GHz Filter ned to 1(1(1 ± 5µm, the mechanical pact and Touchstone together with a r- - fragility of such a thin wafer precludes number of in-house programs. Much External local oscillator its use in genuine production processes: attention at Plessey. and doubtless else- 2.456Hz 21111µm is the usual thickness standard. where, is now being given to the de- Through -GaAs vias are required to velopment of a sophisticated GaAs IC provide a low -inductance path to Fig.3. (a) basic functional block dia- ground and as such they are essential for Lange coupler Low -noise gram of downconvcrter; (h) GaAs high -frequency (> I2GI-Iz) and/or com- ceramic) amplifier AIM/C implementation of down - pact area circuits. The simple concept of RF in converter. "drilling" holes through the semicon- 90° ductor is however far from straightfor- S gnat RF/LO r utirg combiners ward in practice and a great deal of Filter I not MMIC) IF amplifiers process r&d has been invested in the Low -noise development of a high -yield technique amplifier IF out for the vias. Wet etchant chemistry can create vias in thin GaAs wafers but its Mixer IF buffer amplifier poor directional control causes difficul- Active Lo m splatter All components except for the Lange coupler ties in 200µm -thick wafers. Reactive ion and filter are GaAs MMICs etching (RIE) is a much more control-

October 1989 ELECTRONICS WORLD + WIRELESS WORLD 985 MICROWAVE

»MR LS5t111C11.1

Fig. 5. Voltage controlled oscillator (frequency 6-IICIIz: power. 20mW: chip TS I area l.5cnr2). eurcram 01 cTrn+

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986 ELECTRONICS WORLD + WIRELESS WORLD October 1989 MICROWAVE

oscillators - fixed frequency downconverter of Fig. 4 Receiver and broadband tunable. Antenna could now (two years after protection limiter MMIC) the prototype was demon- mixers single -ended. bal- (not - Circulators strated) be replaced by four anced. image -rejecting etc. complex chips and ultimately phase -shifters - time delay by a single chip. and constant phase. A typical individual transmit/receive unit, or switches-SPDT. DPDT etc. module, is as shown in Fig. multipliers- x2. x4 etc. 6. Figure 7 shows the realiz- ation of the small signal cir- power combining and split- cuitry with modern single - ting circuits. function MMICS (each chip logic circuits. Main function-switching performing just one func- phase shift and gain IMMICI tion. such as amplification) RF signals out RF signals in Figure 2 shows an example of operating over 3-6G11z, a typical MMIC produced mounted in a 16mm x I 6mm using this process, a broad- Fig. 6. Functional block diagram of ceramic microwave package. band amplifier working over radar transmit/receive module (shaded The high power stages the frequency range 2-6GIIz region refers to the single chip in Fig. 8). (--IOW) cannot as yet he with a gain of 2IdB in a chip achieved with GaAs MMICs area of 5mm2. The yield to specification mounted feedthroughs from the dis- but are produced at present with dis- of circuits such as this is typically around tribution PCI3. crete GaAs high power transistors. 511%. illustrating the mature nature of the The prototype unit shows a \ery Similarly. the non -reciprocal circulator process. significant weight reduction over typical is realized using ferrite devices and the The building blocks listed above find hybrid designs and a reduction of receiver protection limiter with p -i -n application in many microwave systems. volume of approximately 4: I . diodes. The square chip in the centre of Below are examples of two such applica- The complete downconverter is the package is not a GaAs device. It is a tions chosen to illustrate the use of shown in Fig. 4. With 18 chips it repre- silicon serial -to -parallel converter used N MICs. sents a very high density of GaAs to drive the phase -shifter. MMICs. Such a downconverter is rep- But Plessey's process offers far more Satellite downconverters resentative of a whole class of applica- sophistication than has been used to and it allows the circuit complex- GaAs MMIC technology makes possi- tions. and future de\elopments will see date; ity per unit area to he dramatically ble the development of receivers of the MMICs making inroads into such televi- increased. As with silicon ICs. circuit small size and weight, low power con- areas as direct broadcast satellite is elements can be created that have no sumption and with radiation -hard char- sion (DBS). In this case an oscillator hybrid equivalent. allowing circuit func- acteristics. The MMIC implementation required as an integral part of the subsystem. The NIMIC is ready for the tions to he implemented efficiently. of a 6-4GHz transponder incorporates and an example of a high - Through these techniques, which would a low -noise amplifier, mixer, miniature challenge frequency voltage -controlled oscillator require a separate article to describe filter, high gain I F amplifier and integral is shown in Fig. 5. The Q factor them, all the GaAs chips of Fig. 7 can be power supply. This is a receive -only unit (VCO) realized in the one advanced chip shown (Fig. 3), but it also downconverts the of such an oscillator is usually too low in Fig. 8. The observant reader will spot nominal 6GHz signal to 4GHz, and so for it to be used directly but synthesizer dielectric resonator stabi- that Fig. 8 does not contain the LNA. requires a balanced mixer. This particu- techniques or be although this was for convenience only. lar mixer has a conversion loss of 3dB lization can applied. The significance of this development and a noise figure of 14dB and was be seen when it is recognized that realized using the non -linearity of fets Radar transmit/receive can the module of Fig. 7 requires 28mm2 of rather than diodes. The noise figure is modules GaAs to achieve its function whereas not critical because the device is pre- A most attractive solution for high- the multifunction chip only occupies ceded by several stages of low -noise performance radars is the phased array 10mm2. All the intermediate stages of amplification, a balanced configuration in which the beam is synthesized and testing and chip/wire bonding are saved of MMICs. controlled by integrating the output also. resulting in a potentially much To apply the externally -derived local from many (several thousands) of indi- lower cost. oscillator input, an active splitter chip vidual radiating elements. The key to The GaAs N MIC has now come of has been used. With a single input the the commercial success of such a radar is age and should he considered as the device provides 10dB gain per channel the individual transmit/receive unir be- first -choice medium for many applica- balanced to 0.2dB. Additional phase - each radiator. Unless this can he hind tions. There remains considerable shifting for optimum signal combining produced at low cost the radar will he 'stretch' in the MMIC and the integra- of the mixer is provided by passive uneconomic despite its performance tion of more advanced devices into the N MIC chips using high-pass/low-pass advantages. process, beyond the scope of this arti- networks and providing the necessary Development at Plessey makes such a cie. will result in even higher perform- routeing and combining functions. radar feasible. Spin-offs will allow the ance and extended frequency opera- The MMICs are mounted on four GaAs MN IC to find applications in tion. tungsten copper gold-plate carriers with other areas and the advanced multifunc- signal routeing on alumina microstri- tion chip concepts will lead to 'systems Fred Myers is at Plessey Research Cas- pline. DC bias is supplied via vertically on a chip'. Indeed. the 18 chips in the well Ltd.

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VUTRAXS&A A multi -sheet schematic drawing PC DOS A very powerful New low price system with special features for XT AT 20 schematic circus £500 lii face to drawing vatication May be used 640k or drawing program with ECA-2 extra) for entry of occults into ECA-2 8087/ later extensive features STRUMECH ENGINEERING LIMITED 80287 much favoured by pro- Portland House. Coppice Side. Brownhills fessional users Walsall. West Midlands WS8 7EX. England Telephone Brownhills (0543) 452321 Those Engineers have been providing circuit designers with micro -based simulation and pcb layout software since 'Telex: 335243 -SEL.G. 1983 We now have a broad vane of packages covering many applications and running on machines from the BBC Micro to 386 -based PCs The chances are. if you want computer -based analysis software or a layout system. we .Fax : 0543,361050 have a cost-effective CAD package to suit your needs. When you telephone Those Engineers you will be speaking to an engineer who will see it a, his duty to advise you - our reputation is built on service and not opportunistic sales. Access payment add VAT to above prices. epaacccepted-please

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988 ELECTRONICS WORLD + WI RELESS WORLD October (989 SOFTWARE

PC breadboard

Simulating a circuit on a PC can save weeks of costly prototyping. More than that, it can provide important information about the likely manufacturing yield by answering the question: "What happens if ...?" John P. Martin reviews two popular simulators.

There was a time when fabricat- But if the circuit's performance is more on the suspicion that a computer doesn't ing a prototype integrated cir- critical. many weeks (or months) of know quite as much about a BCI09 cuit cost an arm and a lee, and testing with expensive equipment mas transistor as does an engineer who has no engineer would dare to he necessary. For this reason alone a been using them for some years. Simi- commit his design to silicon computer simulation may prove cheap- larly. what can a computer know about without being highly confident that the er and immune from the errors that test circuit would work, and would continue equipment itself can introduce. More to work in varying conditions of temper- importantly. perhaps. is a simulator's ature and where the parameters of the ability to answer the designer's eternal The benefits are a more devices might vary greatly within their question: -What if .. ?". For example. controllable, flexible and tolerance ranges. To create this pre- a transistor with a nominal h1_1. of IOU production confidence. computers could actually have an 111.1. of anywhere reliable approach to product (which then cost a mere leg) were between 50 and 200. If the half -dozen manufacture. programmed to simulate the design circuit prototypes were all made using mathematically and provide data on the the same hatch of transistors, then the performance of the design over a wide likelihood is that the transistors would range of possible conditions. Most all have a fairly closely matched 111.1:. So the inductive effects of PCB tracks or prominent of those simulation prog- all the prototypes might well work with- the proximity of an amplifier's input rams was Spice (Simulation Program in specification. But then. in the middle stage to a mains transformer? Clearly. with Integrated Circuit Emphasis) de- of a production run of 100 000 units. any simulator is only as good as the veloped at the University of California transistors are taken from a new hatch. information it is given. and this informa- in Berkeley in the mid -1970s. and suddenly all units fail to meet a part tion divides into two categories: Spice spawned many offspring of of the specification. At best, this prob- Full details of the circuit must he varying legitimacy but the modern ver- lem can be solved by the alteration of Liven to the computer. This may seem sions are now more accurate, more some resistor values: at worst the circuit obvious. but the effects of stray capaci- friendly, relatively cheap. run on the may need to be re -designed to t.tnce and inductance will he taken into ubiquitous IBM-compatible PC and accommodate a possible spread of h1.1.. account by the simulator only if they are provide those all-important colour Naturally. this situation can he pre- included as part of the circuit descrip- graphics without which no modern com- dicted by calculation, but for large cir- tion! puter program is complete. For the cuits. the amount of number -crunching Devices used in the circuit must he engineer who is not engaged in inte- involved would be impossible without a accurately modelled. It is this aspect grated circuit design. libraries of stan- computer. which is most often neglected. Compu- dard components are available, enabl- Simulators are becoming an integral ters deal with numbers and those num- ing the simulation of discrete electrical part of many computer aided design bers are derived from mathematical and electronic circuits, which may (cad) systems and the benefits are a models which are, in turn, derived from themselves include standard or custom more controllable. flexible and reliable pseudo -physical models based on the

integrated circuits. approach to product manufacture. I can observed operation of real devices. Re- do no better than to refer the reader to sistors and capacitors are quite straight- Why bother? Mike Walsh's excellent article "Design- forward and idealized models are usual- The design method which uses the back ing with cad" (July. page 694) for a ly sufficient, although non-linear effects of a cigarette packet followed by the fuller development of these arguments. can he included if necessary. But semi- building and bench -testing of half-a - There is an understandable feeling conductor models are more complex. dozen prototypes seems to have a lot to that anything simulated on a computer Simple linear analysis packages such commend it. For simple. non -critical is going to be rather "ideal- compared as Analyser II use ideal, linear models circuits, this approach may well suffice. to a "real'' circuit. This feeling is based for transistors. Pets and op -amps. with

October 1989 ELECTRONICS WORLD + WIRELESS WORLD 989 SOFTWARE

the provision for including input resist- Table 1: main features of PSpice and ECA-2.

ance and capacitance. ECA-2 uses the PSpice ECA-2 well-known Ebers-Moll model for the Price £1195 £675 bipolar junction transistor, while DC analysis PSpice uses an enhancement of this, the DC sensitivity Frequency response (small -signal AC) Gummel-Pooh model. AC sensitivity It is the passing of parameters into Transient analysis (time -domain) these models which creates specific de- Fourier analysis (no graphics) Distortion analysis vices like the BCI09. Similar models are Noise analysis provided for fets. op -amps. etc.. which Temperature runs have been the subject of many papers Monte Carlo and worst-case £190 extra Component sweeping a themselves: but for now it is sufficient to Parts libraries accept that the models used by these Digital/logic simulation £190 extra simulators are more realistic than those Parts modelling program Supplied models used by many engineers who design by complex simple Hard -copy output but needs £50 extra hand. This is not to belittle the know- driver for EGA how of designers. but merely to point Documentation very good good Minimum out that the polynomial functions used hardware 512Kbyte ram, hard disk 256 Kbyte ram, single floppy maths coprocessor to describe the non-linear characteris- Circuit size' 100 transistor equivalents > 100 nodes with 256K ram tics of semiconductor devices are ex- (1 transistor equals 10 resistors) 500 nodes with 512Kram traordinarily tedious to work with using Direct comparison is difficult Memory is used for circuit data and for the results of analyses. so there may be a anything other than a computer. PSpice trade-off. The figures are quoted by the suppliers, has an extensive library of common devices with good models, and an interactive parts modelling program to very good value but is not quite in the and my ads ice is to obtain both and assist in the translation of manufactur- same class as PSpice and ECA-2, which make your own mind up before commit- ers' data sheets into PSpice parameters. provide DC and time -domain analyses ting yourself. You will also find the using non-linear modelling. Table telephone support from the UK sup- Electrical, electronic? compares the main facilities available pliers to be excellent. PSpice and ECA-2 are "electrical" cir- from PSpice and ECA-2. both of which cuit simulators. which means they deal run on IBM -compatibles. PSpice is 75% Hardware requirements with volts. amperes. seconds, ohms etc. more expensive than but has ECA-2 the ECA-2's hardware requirement is quite A group of transistors acting as a logic advantage of being an industry stan- modest: the suppliers recommend a gate is treated no differently from a dard. It also comes with a library con- minimum of a single -drive PC with 256 group of transistors acting as an audio taining several thousand common de- kilobytes of ram. All types of display are amplifier. vices, whereas ECA-2 does not have yet supported but a graphics display is re- The difference is in the application of a library. commended. Similarly. most modest the circuit, not its operation. Since logic ECA-2 is a relative newcomer (1985) Epson -type dot-matrix printers will pro- signals are merely a special form of and in therefore. a sense. has to prove vide adequate graphical hard-copy. analogue signal, and since megavolts itself: but it has made a a good start by If you have an enhanced colour dis- have no greater significance to a compu- running taster and being more inter- play such as the IBM -EGA, or use a ter than microvolts. these analysis pack- active. Apart from PSpice's extensive laser printer, then you will need an ages are useful for all types of circuit. component library, there is not a great extra program called Print -D which is For logic designers who are more in- deal of ditference between the two utterly hideous to set up. Speed of terested in Os and Is than in volts, there packages. your will and choice depend operation is increased by two to four are. of course, specialized logic analysis on cost and personal preference. That times if a maths co -processor chip of the packages. however. PSpice has a preference is likely to depend on pre- 8087/8(1287/80387 type is fitted, but "digital files'' option and an extensive vious computer awareness mo e than on since the prices for those devices range library of common TTL and c-mos previous electronics experience. PSpice from £84 to £641 many users may be Darts, which could useful to those is prove more expensive and gobbles up a lot content with the slower speed. wishing to mix analogue digital more and memory than ECA-2. but the PSpice arrived on three quad -density circuitry. either with discrete compo- result is a more user-friendly package disks, which meant I had to use an AT nents or on a custom or semi -custom on all levels. machine to make working copies on to integrated circuit. Fortunately. both suppliers can pro- eight DD disks before installing the vide evaluation/demonstration versions program on my Amstrad PC 1640's hard Which simulator? of these packages at very modest cost. disk. Minimum hardware requirements Analyser II is a good introductory pack- for PSpice are 512Kbyte of ram. a hard age for those new to computer simula- disk and a maths coprocessor chip. tion and for schools. colleges and simi- Again. most display and printer types larly under -funded institutions. It runs The various types of are supported and the user can confi- on a BBC Microcomputer or on an analysis can be gure the software to recognize these by IBM-compatible used in an personal computer almost infinite ec iting two refreshingly English - and provides a basic linear analysis of number of looking files. PSpice is supplied with a frequency versus gain. phase. input and combinations. dongle - a special plug which fits into output impedence and group delay for the serial port of the computer - and transistor. fet and op -amp circuits. It is without it the program will not run. This

990 ELECTRONICS WORLD + WIRELESS WORLD October 1989 SOFTWARE

is to prevent the use of pirate copies of "hatch mode" whereby the input file is the software. analysed completely. If the circuit de- The documentation supplied with All nodes in the circuit scription or analysis parameters need to are assigned a node number both packages, in the standard 113 M - he adjusted, the input file must he type jacketed ring hinders, was good. (see examples) re-edited and the simulation run all over Having been around longer, the PSpice again. With ECA-2, the operation can manual has a more user-friendly feel Circuit description is he in hatch mode or more interactively: and a rather more helpful and logical written using internal that is the simulation can be inter- layout. text processor (ECA-2) or rupted. a parameter "tweaked'' and the internal/external simulation continued. This saves time in process processor (PSpice). the early stages of product develop- Simulation Alternatively a netlist ment. However. most engineers would The basic sequence of steps for simulat- file can be imported from want to run simulation again ing a circuit is shown in Fig. I. The first some schematic packages. the entire any tweaking. stage is to provide the simulator with a after description of the circuit to he analysed. A successful simulation run produces Also includes in the With both ECA-2 and PSpice this can two types of output: textual and description file are: graphical. The text files can he simply he done from within the program by device model parameters read from the screen or sent to a printer typing in the netlist'. or by importing irput signal descriptions in the usual way. the netlist from a schematic capture analysis type details The graphical outputs package like Votrax for ECA-2 and specification of special from the two programs are handled OrCAI)/S1)T for PSpice: or by writing output formats rather differently. With PSpice a data the description file using any simple text tile called PHorlr:.nAr is created by the t simulation and this is then subjected to edition. Which entry level you choose The simulation is run the Probe graphics post -processor prog- will depend on your previous experi- interactively or in batch ram supplied. High -resolution colour ence of package -driving. but I find that mode (ECA-2); or in batch mode only graphics then appear in a fully interac- creating an input file on a simple text (PSpice). ECA-2 editor to he the most satisfying. Also can provide results as the tive menu -driven environment and data simulation runs. PSpice included in the input file must he the can then be mathematicallly manipu- generates two output lated into the required form. For exam- parameters for the required analyses. files: a text file and a ple. simple ratios of voltages can he and some information specifying the graphics data file. displayed on the or can he required output format. Figure 2 shows graphs, converted into logarithmic (dB) scales. a simple audio amplifier circuit with its complete input file in PSpice format. For PSpice, graphical data Figure 3 shows a screen -dump of the is subjected to the Probe Lines starting with an asterisk are resulting frequency response requested graphics post -processor, in Fig. 2. having logarithmic scales for optional comments. . which is interactive. One of the fundamental differences frequency and for voltage gain. between PSpice and ECA-2 emerges at ECA-2 gives a similar graphical output, with slightly less on -screen in- this point. PSpice runs in a kind of formation, but has the advantage of Fig. I. General sequence ol'steps for A 'waist is a textual list of components and circuit simulation. presenting the graphs as the simulation their interconnections. Net lists can he gener- progresses, rather than waiting for the ated manually or extracted from many cad Fig. 1. Simple amplifier circuit showing complete range of analyses to he com- packages which use schematic capture node numbers and (below) its associated pleted. Thus the simulation itself can (screen-drawini'). Netlist formats vary be- PSpice description file analysis become interactive. is tween manufacturers and the examples containing This particularly parameters a frequency response shown in the text can he compared with for useful during the early stages of product those in "Designing with cad" in the July measurement. The resulting frequency development when the basic circuit is issue of this magazine. response curve is Fig.3. being "computer -breadboarded''.

Simple amplifier frequency response

Circuit description: Vcc 20V R1 1 C 15k

R2 1 2 lk R3 5 0 300 R4 3 4 3.3Meq R5 10k R5 8 4 10k C4 R6 6 7 lk (a R7 7 100k Ry 0 4 (b1 Cl 2 0 47OpF 1N C2 2 3 4.7uF C3 3 5 470pF R R lk C4 4 6 luF Ql 4 3 5 Q2N3707 Bipolar.11b 2N3707 .LIB 'Input descriptions: vin 5 t vcc 8 o 20V 470p y Vout Vin 1 0 AC 1 V .AC Dec 10 1Hz 1MegHz R1 15k C1 470p R3 300 R7100k I Node 0 OV 'Generate data for PROBE graphics: .PROBE .END

October 1989 ELECTRONICS WORLD + WIRELESS WORLD 991 SOFTWARE

Types of analysis be used for evaluating "worst -case- portents within their specified tolerance Table I lists the principal types of analy- conditions. i.e. when all the component ranges. and can thus produce the family sis available from these packages. tolerances conspire in a direction which of responses shown in Fig. 4. However, remember that these analy- causes out -of -spec operation. Coupled It is worth repeating that these are ses can he run together in an almost to this is the Monte Carlo analysis which only some of the more conunonly used infinite number of permutations and randomly assigns actual values to corn - features of these programs. and that the combinations. For the newcomer. the following outline of these analyses Simple amplifier frequency response Date/Time run: 07/06/89 18:58:14 Temperature: 27.0 might be useful: 30+ DC analysis calculates the static volt- -+ -+ -+ -+ -+ -+ ages and currents at all points in the circuit. Capacitors are treated as open - circuits and inductors as short circuits (unless any resistive parameters have been specified in their models). The result of a DC analysis is a textual list of all nodes with their corresponding 25 -k direct voltages. Currents through all components are available too. DC sensitivity analysis calculates the effect on the DC analysis of variations in the parameters of any specified component or components. AC analysis is the name given to 20+ frequency -domain measurements. resulting in Bode diagrams. It is a small - signal analysis. which means that the actual input voltage specified is immate- rial and may conveniently be set to unity so that the output voltage is numerically the same as t he gain of the circuit. -f W sensitivity reveals the percentage 15+ -+ -+ -+ 1.Oh lOh 100h 1.OKh 10Kh 100Kh 10Mh change in a specified AC parameter in VdB (7) response to a percentage change in a Frequency component value. Transient analysis might better be cal- Fig. 3. Frequency response curve for the circuit of Fig. 2 (PSpice). led time -domain analysis since the out- Effect of 10 random values 1:45 vi puts of thin 20% generated are more like an oscillo- Date/Time run 07/11/89 18:47:05 Temperature: 27.0, 27.0, 27.0,... scope display. The actual values of input 304- -I- -I- -I- -f- -F- voltage are used in the calculations so f that the effects of clipping and other non-Iinearities can be evaluated. Fourier analysis can he requested at any point in the circuit, and the computer output lists the harmonic content of the output waveform. PSpice can display this graphically as a spectrum and it also 25 4- calculates the percentage total harmonic distortion due to harmonics up to the tenth - this is the harmonic analysis

referred to in Table I . Noise analysis is provided by PSpice. though not by ECA-2. This is a summa- tion of all the noise generated by the 20 + components of the circuit. Temperature sweeps can he performed on the circuit in much the same way an oven might be used on actual prototypes. Each component should therefore he assigned a temperature

coefficient during the circuit description 15+ -+ -4- phase. Some manufacturers are able to 1.0h 10h 10- 0h 1.OKh 10Kh 100Kh 1.0Mh o e o . x V supply ready-made PSpice models dB (7) for Frequency lie ir co iii pone nit s. If the circuit components are assigned Fig. 4. Ellect ol'¡1)random values ol'R; within a 21)% tolerance, obtained from a tolerance range. this information can Monte Carlo analysis (PSpice).

992 ELECTRONICS WORLD + WIRELESS WORLD October 1989 SOFTWARE

various analyses can he used in an almost infinite number of combinations. The simple examples shown here cannot begin to reflect the true poten- SPIT elc,rtcal Circuit oiriúlator p,os_an distribu,,(r tial of either PSpice or ECA-2 when sion 4.81. January 1989 pyright 198i - 1989 !ilj j".3Taicrosystens used with larger and C. circuits, potential IcroSin Corporation toman Road. Canberleu converts to computerized circuit simula- rized copy_rg of thas --I GU 3llF tion should obtain the demonstration/ ;layan is prohibited, . MS evaluation programs, which contain worked examples. aníating circuit: FOG 4 Simple cuylifter frequeuey response Sources file I>

ECA-2 is available from Those En- gineers Ltd. 106a Fortune Green Road, London N W6 IDS; tel. 01-435 3757. Fig. 5. PSpice's information screen provides status reports throughout the simulation. The price is about £675 with various optional extras. An educational -users' discount may be available. A demon- +-- +- stration version is also available as are other Spice -type packages with GEM graphics front -ends. I r

Since John Martin completed his re- rt9% , . , view of ECA-2, version 2.49 has been introduced by Those Engineers Ltd, who tell us that it adds the following enhancements: (1) up to four variables can he NJ plotted with independently - scaled parameters; (2) graphs may be titled independently of circuit title; (3) hatch files may now be chained and/or nested; (4) a thyristor model is added. 15+ -+ ------+- +-. +- 1,8h 18h 188h 1.8Nh 1DNh 1eeNh Analyser II is available from Number ="U dB (7) a V de :1) r-- quency One Systems Ltd, I -larding Way, St

I ves. Huntingdon. Cambridgeshire, 8)11xit 11Add Trace 211(enoue Tracé 33X Axt's 4)( Axis 5)Piot Control 8)Hatd Copy PE 17 4W R: tel. (0480) 61778. The price AK amor ' I is about £195 for the PC version and £ 130 for the I3BC N icro version.

-+ 4- John Martin B.Sc., C. Eng., MIES, isa +- ---- senior lecturer at the Anglia Higher . 1 Education College, Cambridge. 1

Fig. 6. /'Spice screen showing essentially SEt.» the same response Fig. 3. i as The red ittf -r ------t- -4 trace is the response at node 4 { hile the o -1(000)w(9) green trace is the response at node 7. 4.BV+ -+ t a- 4- after the DC -blocking capacitor.

Fig. 7. Split-screen facility offered by PSpice. The lower trace shows the input- output characteristic of a simple TT L e.eVti inverter circuit. The upper plot has the a - same (viz. input voltage) but eeu e.5V 1.BU 2.51) X-axis o u(8) shows the power consumption of the u(1) gate. The peak is caused by tite gate ) 8)Exit attempting to operate in its linear 1)(idd Trace, 2)11enove Trace 3)X Axis is? Axis 5)Add Plot 6/Select Plot 7)Renove A)Cursor 1 region. ?lot B)Hard Copy 9)Suppress Symbols

October 1989 ELECTRONICS WORLD + WIRELESS WORLD 993 COST-EFFECTIVE MEASUREMENTS OF EMC COMPATIBILITY AND BROADCAST EMISSIONS

The Farnell 352C Spectrum Analyser is a low cost, portable and easy to use instrument designed for monitoring spurious EMI radiations in the range 300kHz to 1000MHz. Its features include:

Built-in radio receiver with AM and FM demodulation Picture store. Hard copy evidence of offending emissions with optional printer Field strength measurement option Portable. Line or vehicle DC operation. Rechargeable battery option Cursor measurements on screen of level and frequency Control settings memory Wide range of optional accessories

PRE -CHECK YOUR EQUIPMENT BEFORE YOU SUBMIT IT FOR APPROVAL REGARDING EMISSION LEVELS

Six page colour brochure available on request to: FARNELL INTERNATIONAL 0 JUBILEE HOUSE, SANDBECK WAY, WETHERBY, WEST YORKSHIRE, ENGLAND LS22 4DH Farnell International TEL. +44937 61961 FAX +44 937 66487 TELEX 55478 FARINT G

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Whither the OTA? using simple beam balances and but perhaps someone more detectors are both bulky and spring balances. The gyroscopic expert :n the conversion of wildly inefficient. I found the article on current - 'levitation' demonstration is angular momentum into linear Dr Aspden admits that a gyro feedback ( WW, op -amps E& easily repeated but with a simple momentum could give me the supported at one end of its shaft August 1989) interesting for Newtonian explanation. 1 use real reason. Did I hear someone and precessi ng /reel y exerts a more than one reason. Apart these demonstrations to indicate shout "conservation laws!"? downwards thrust on the support from the improved performance that care is needed in making M. Hamer just equal to its weight. any other these devices offer, I was dynamic measurements and Ullingsss'ick forces being very small. This reminded of the operational - further that the senses can easily Hereford proposition Professor Lait hwaite t ransconductance amplifier he confused when applied to would at one time have strongly (OTA). which was developed in three dimensional phenomena. Anti -gravity and cold contested. Now if, as Aspden the late 1970s. It was hailed as a If anyone still believes that claims, the downward thrust can breakthrough in analogue gyroscopes are non -Newtonian fusion he made much smaller by engineering hut, curiously. then I shall he pleased to arrange H. Aspden's July letter is too encouraging the gyro to precess was nothing further heard of it a short demonstration at The contentious to be allowed to pass at slightly more than the free rate after a time. City University. London. unchallenged. In support of his ('- a heavy flywheel ... lifted by I would he interested to know As an example of apparent claim that several of the accepted Professor Eric Laithwaite's little of its fate. Perhaps one of your anti -gravity effects in electronics conservation laws of physic; finger'). then the thrust should readers me. could enlighten consider the case of a charged might be invalid, he cited he made much greater if the gyro B.D. Runagle particle moving in a plane passages from the 1966 edit ion of is inadvertently encouraged to Burton on Trent normal to a uniform magnetic a hook by H.S.W. Massey. They precess at slightly less than the Staffordshire field. It is well known that the have all the earmarks of having free rate. i.e. handling it would particle will move in a circular been written a decade or two he quite tricky. My recollection Gyroscopes path. If now we take into account earlier, since by that date of seeing Professor Lan hwaite As a relatively new regular a gravitational field acting in the quantitative experimental and two volunteers (a man and a reader of your magazine I have plane of motion. i.e. at right evidence was available woman) handling a heavy gyro in been impressed by the breadth angles to the magnetic field, the confirming Pauli's hypothesis turn is that each used the palm of and depth of coverage of topics. path does not sink downwards that the apparent breakdown of one hand to support the end of Therefore it is to he expected but drifts sideways: apparently energy, momentum, and angular the shaft. and that the volunteers that aspects of mechanics will defying the law of gravity. The momentum conservation in beta were told not to try to influence enter into articles and problem described is also readily decay arises through ignorance the motion of the gyroscope. but correspondence. solved by classical mechanics. of the fact that, in such decays. a simply to swing round so as to I was, however, surprised to In all the above examples it is third particle is emitted. This follow the free precession. i.e read that some readers still assumed that speeds do not unobserved third patticle was that no such critical control was believe that gyroscopic approach that of light so that the subsequently called a neutrino. required. phenomena fall outside the theory of relativity does not need Articles reviewing wide I am now of the opinion that jurisdiction of Newtonian to be considered. range of such experiments, along the progressive upward tilting of mechanics. Whilst appreciating H.R. Harrison with a presentation of modern the gyro shaft sometimes that any physical law is only an Dept. of Mechanical beta decay theory which observed in such experiments is approximation and is only valid Engineering& Aeronautics provides a detailed systematic associated with the frictional until proven incorrect, all The City University coherent account of them. can be torque exerted by the spinning observed gyroscopic phenomena London EC I found in the Sieghahn's'Alpha-, gyro on its shaft. Anyone holding are quite adequately explained Beta-, and Gamma -Ray the shaft and turning with the by Newtonian mechanics. Anti -gravity Spectroscopy'. Other articles precession of the gyro has to The basic equation of motion deal with parity violation in beta oppose this torque to prevent the for rigid body motion in thre Philip Lonsdale's letter in the decay (discovered in the late shaft from twisting in hisor her dimensions were established by July E& W Wdescrihingthe 1950s). and review the hand. and in so doing sets up L. Euler (1758) and gyroscopic "Dean Drive" was most appropriate experiments. The torque about the vertical axis motion in particular was interesting. Presumably it most dramatic consequence of through the centre of the gyro. discussed in some detail by E.J. consisted of two dumb -hell parity violation is that elect-ons This causes the gyro to precess in Routh (19(15). An excellent weights shuttled across a rotating emitted in beta -decay show a vertical plane, leading to the contemporary text is shaft at twice the rotational strong longitudinal polarization. upward tilting mentioned above. Gyrody narnics by Arnold and frequency; or two contra - even when the emitting nuclei I found Dr Aspden's January

Maunder (1%1). In the seventies rotating devices, more likely. A are oriented at random. I was description of 'The force- I published an article to help less developed type of Dean myself involved in one of the precessed gyroscope' dispel some of the Drive seems to be known to earliest experiments to unconvincing. If in diagram (a) misconceptions t hat were being many I 1/2 to 3 year old toddlers as demonstrate this polarization'. (page 30) the mechanical system perpetrated at that time. Also at they persuade tricycles and specifically in electrons emitted exerting a torque Ton the the same time other dynamicists trolleys to move, albeit slowly, in by Au'''. Previously no-one hearing assembly S exerts no and myself took part in a meeting one direction on level surfaces by suspected its existence, so that it thrust on the vertical shaft the with the same objective. I undulating their bodies and not played havoc with the first two gyros should tilt. but in such thought the matter now was just using their feet at all. Anyone attempts (in the 1931 s) to check a way that the centre of gravity of history. but apparently this is not who has laid a concrete floor with Mott's Dirac theory calculations the bearing. sleeve, and gyro pair so. a vibrating screed will also know of fast electron double -scattering does not move. In fact, he Asa direct result of these that there is a definite preferred experimentally. Successful implies that it moves upwards. 'close encounters' we direction of travel for these neutrino detectors have now which suggest tome that the constructed some simple devices. been in operation for many torque generating system did experiments to show how I have always assumed that the years. hut because neutrinos can exert a thrust on the vertical rotating objects and oscillating horizontal force resulted from pass right through the earth with shaft. If I'm wrong, that in itself bodies apparently 'levitate' when asymmetrical frictional forces only a mild loss of intcnsitythe proves his case, if not his

October 1989 ELECTRONICS WORLD + WIRELESS WORLD 995 LETTERS

interpretation of the behaviour conditions, and the filter is often and not electromagnetic? I low damaging for the image of of the full system is invalidated. not exactly centred on the else could it distinguish between science (which the general public C.F. Coleman correct frequency. The result is the negatively charged has come to regard as the fount Grove that they often have 2% or more conduction electrons and the of all indisputable knowledge). Oxfordshire distortion on the narrow equal positive charge on the They would rather there was References. position. but the magazine atoms in an uncharged never any public dissent. I reviewer will never say that he conductor? Remember William maintain that these people are I . Alpha-. Beta-, and Gamma - Ray Spectroscopy. ed. K had to offset his generator to get of Occam's razor' and try harder wrong. As in politics, dissent is a Siegbahn, North Holland, the less than 1% claimed. to explain odd phenomena in sign of a healthy system. It is only Amsterdam, 1965. I will continue to apply the termsof the laws which have damaging to a false image of 2. Cavanagh, P.E. Turner J. F. hest engineering practice to my served us so well since the days of science. Although many Coleman, C.F. Gard, G. A. and designs, and if the manufacturer Ampere and Coulomb. (I have scientific doubts can be resolved Ridley, B. W. Phil. Mag 21 want to add five dollars worth of retired, so 1 am not going to do in private by appropriate (1957) 1105. polypropylene coupling all the work, but hints for the research, there will always he capacitors to the audio output of mercury fountain are hydrostatic some which can only he resolved Pseudo science his tuner, and the purchaser pressure due to the 'pinch effect' by discussion amongst a wider wishes audience. The article Science v. to pay 50 dollars more for and the question of convection subjectivism in audio the satisfaction of knowing that current as well as conduction.) But who are these dissenters? is was that engineering (July 1988) by no electrolytic capacitor *Oman's razor a rule Why do they always sound so D.R.G. Self was excellent. It corrupting his sound. that is his hypotheses are not to be paranoid? Why have so many unnecessarily. could also be applied to FM business. An electrolytic multiplied original ideas originated from capacitor still couples the FM D.A. Bell outside the universities? My own tuners, at least in the USA and I detector to the Beverley when I suspect Great Britain as well. Mr output stereo experience started to Self did an outstanding job in decoder, however. North Humberside doubt the universal validity of disputing the claims of Jon GrosJean the second law of "electrolytic capacitor sound" or Connecticut thermodynamics have given me the effect of 100 dollar per foot USA Doubt and faith an insight into these questions. cables, and the argument is It is an old problem with the I thought (and still do think) equally applicable to FM tuners Alpha -torque forces scientific method that the could see a flaw in the reasoning which have only a 17kHz audio After reading the recent article validity of all scientific laws is behind this law. Furthermore response at best because of the (E& WW June 1989 p.556) my dependent on them being open thought 1 could see a way that the requirement to filter out the 19 first comment is that I do not to theoretical and empirical law might he circumvented to kHz FM stereo pilot. The claim understand the statement that refutation. This status should not build what is known asa that an NE5534 operational "Electron beams in a vacuum do change with the passing of time. perpetuum mobile of the second amplifier modifies the sound of not obey Ampere's force law" After all. Newton's laws had kind. At first. I thought that it the low-pass filter is ridiculous. since the designers of electron been established for 200 years was likely I might he wrong and In one tuner, the manufacturer microscopes appear to have been before Einstein carne along! At that some friendly colleague or provides a low-level audio successful in using magnetic the same time. it is helpful for the consultant might point out the output before the NE5534 for focussing of electron beams. pragmatic scientist to be able to error. This did not happen. The those who want purer sound: the Perhaps the word 'solely' is have faith in certain next step was research in public real result is that the capacitance omitted. "fundamental" laws of science. It and university libraries. This of the cable connecting the tuner Then Fig. I of the article is inevitable that the scientific showed me some mistakes I had to the audio amplifier messes up illustrates the danger of trying to community is sceptical whenever made that the people I consulted the resistive termination of the reduce a three-dimensional someone claims to have found could have shown me but low-pass filter and causes a peak problem to two dimensions: violations to them. nothing that destroyed the idea. at 16 kHz. This, of course. inspection of the diagram reveals Both doubt and faith in well In fact this research enabled me soundsa little brighter. immediately that as drawn 2a + e established principles are to refine my theories and The other situation which = 180° so that the last term in healthy attitudes for science to encouraged me to think that I continually causes problems is equations (1) and (2) is simply adopt. But they are in conflict might be on to something. the desire for more selectivity. the number +1.5 (cos 180°= -I) with each other and a proper Writing to academics who had No non -technical person and and sin (2a + e) in equation (3) is balance must be struck. It is my been recommended to he as very few engineers understand zero. This is true whatever the belief that in recent years the knowledgeable in the field was that filter selectivity and relative positions and directions emphasis has been too much in unsuccessful. Usually I received distortion produced on FM of the current elements in the the direction of faith. no reply at all (although one signals are related. Furthermore. plant. The trouble is this: it is almost lecturer wrote hack and told me the IEEE/II IF specifications on Ampere said that a three- impossible fora single mind to he was not interested in FM tuner measurements allow dimensional magnetic force simultaneously have doubt and discussing ideas which defined for "slight retuning" of a tuner problem could he reduced to two faith in anything. Consequently "Common Sense"). Trying to get when measuring T11 D. Digital dimensions, but how do we know when a discussion about the my ideas published also failed synthesized tuners cannot that the hypothetical alpha - absolute truth of a law arises. it (even in Wireless World). Could usually he slightly tuned, but the torque force obeys the same laws tends to be between two factions it have been the style rather than generator can, so this is usually as the magnetic force due to of scientists (usually in the pages the content? I never knew done. Unfortunately. the user is currents? In any case, three of a journal with the subscribers because I always received my not able to ask the station to dimensions can be handled as as onlookers). Scientists being manuscript hack without slightly alter its frequency. There easily as two with vector algebra only human, this debate can comment. The only practical are some very expensive tuners (which was not known to degenerate into personal experiments I have been able to on the market today with a Ampere). If the alpha -torque attacks. Even if it doesn't. there afford have proved to be narrow bandwidth selection for force is "ponderomotive", does are those who believe that this encouraging but equivocal. Even those difficult reception this imply that it is akin to gravity sort of discussion can only he the avenue of patenting my

996 ELECTRONICS WORLD+ WIRELESS WORLD October 1989 LETTERS

device is denied to me because I tidy up the explanation. Of everything. A,=A/( l + ). am advised that the law forbids course, if this were anything To turn to the bipolar/hybrid it. There seems no avenue left more than a diversion. scientists output stage. the driver open to me to find the truth of would have long since sorted it transistors do indeed operate in

the matter. I am sure that these out. Class AB. but I doubt if these And the equation for the experiences are not unique to Incidentally. a more revealing relatively fast TO5 devices have a Michelson-Morley experiment me. way of expressing the division of had effect on the crossover should have a + rather than a - The next time you read an x" -y" by x-y is by saying that it behaviour: all that can be said is on the left side. article in these pages by someone equals the sum of n terms. the that the stage asa whole is E.W. Silvertooth challenging a scientific first and greatest of which is x" remarkably linear whithout any Olga orthodoxy. remember these with each succeeding term y/x overall feedback. My own view is Washington things. He has probably had to times its antecedent. This that the poor matching of the USA refute many spurious objections changes the order used in the not -so -very -complementary from people who ought to know January examples which seemed MOSFETs around the crossover better. He has probably been easier to memorise. region is probably the cause of ignored my many academics to Name and address supplied what crossover perturbations can Help! whom the fear of ridicule he seen. I have tried Class -A I am currently working as part of damaging their career prospects Feedback and fets drivers with AB bipolar output the British Volunteer is far greater than their lust for devices. and there seemed to be Having just read Ivor Brown's Programme in the electronics knowledge. He may even have no benefit to be had. letter in the July 1989 issue. I feel department of the National been laughed at by people who Finally, it might he valuable if that the matter of slew -limiting University of Engineering. have not the wit to understand all of us provided more needsa little more ventilation. I Nicaragua. We are perhaps one tenth of what he is trying to measurements in articles and quite agree that in the amplifier amongst your more far flung say. letters, as otherwise comparison system he describes. the slew - subscribers: we receive EWW If anyone is interested in and reasoned discussion are very rate of the early stages has a via our sister university in discussing my revised theory difficult. In particulat. designs of marked effect on the distortion Holland. the Technical the second law and its are often labelled "low produced. However, to bring University of Delft. which has an applications. I would he happy to feedback" or "lashings of this about, he has had to assume extensive programme of co- hear from them. feedback'. without specifying a dead -band effect in the output operation and aid with us. R. Lerwill how much. While measuring stage: in other words. for small EWW is in fact the only Castle Mills open -loop gain is not always signals there is no output at all. as journal we receive because none Chirk, Clwyd easy, the results should be highly in a Class -B stage with zero of the free circulation journals informative, and perhaps Mr quiescent current. Since much of seems willing to mail to a third - Brown will reveal the results for No integers for the design work done on world country. Likewise, it is his design in his forthcoming amplifiers in the last thirty years difficult to obtain data hooks: I an+bn=Cn article. has been aimed at eliminating have only two dog-eared Intel Douglas Self My previous notes, neatly and such gross crossover books from 1980 and 1981. Forest Gate faithfully reproduced in the discontinuities. I must admit that I wonder if any of your readers London. E I 5 January issue. assume that it I am inclined to view the would he interested in helping would he absurd to expecr a demonstration as tending out by sending us surplus copies solution simply by replacing the towards the not very useful. Motion through the of journals or data hooks t hat common exponent 2 in The sharp spikes seen on the they are replacing. We would he Pythagorean equations with a distortion residual of every ether interested in the whole range of greater integer. This after all is under -biased Class -B amplifier The May issue of. E & WWcarried specialist subjects. e.g. merely an opinion and no matter are a demonstration of this an article over my name. telephony. radio, microwave,

how many might share it. hardly effect. Improving the slew -rate With reluctance I must report satellite comms. industrial, a proof. of the early stages will make three errors w hich are of digital, micros. computers. Regarding any applicable set these spikes more narrow. but importance if the content (tithe electrical, power. Airmail is not of integers. or P triple as some will not reduce their amplitude. paper is to be correct. I have no that expensive and takes about

would call it. e is one of the odd and this would be considered a idea how these carne about and I three weeks. numbers and a is usually the even faulty or maladjusted amplifier apologize. hut thought your We would also he very one. Let this he the case at rather than one under -designed journal should at least he made interested in designs for present. for clewing. Increasing the aware. electrical or electronic products If c' -h2 = a2 then a2 would. quiescent current reduces the The equations for wavelengths which could form student like c2 -h'. he divisible by c- h. height of the spikes until they published as projects. and ideally which could So also would a" because this is a merge into the main body of the he adapted for small scale

multiple of a2.'f hen a"/(c- b) = distortion products. and in fact Ai=x(I+ manufacture here. " /. a"-' (c+h) which is the product this is the only reliable way of \ c The address to send to is: of two even numbers. setting quiescent current. With it El Director However. when n is odd. the correctly set, a well -designed Escuela Eléctrica/Elcctrónica other side. now (e" -h")/(c-h). output stage will have only very Universidad Nacional de equals the sum of an odd number small slope changes around the x,=x(1- 1 hrgeuie ria of odd numbers. crossover point, and the early c MANAGUA Apartado 5595 In a different way it can also he stages are not called upon to NICARAGUA shown that when n is even. the make particularly rapid Donald Power supposition is again adjustments to servo -out these should he Escuela de Ingeniería Eléctrica/ unquestionably absurd. Fellow - errors. Clearly, with poor design Electrónica readers might like to amuse slew -rate could he a problem. x =x/(I+ " Managua . themselves w ith this one while I hut then so could almost c Nicaragua

October 1989 ELF( ''IRONICSWO12LD+ WIRELESS 90121...1) 997 ELECTRONIC SURVEILLANCE

Continued from page 982 detected by Promon, but not by the device finds application in more handset unless the number of rings straightforward guise in large stores; the to receive or make a call the Pole Job goods detector at the door recog- transmits the speech and dialled num- exceeds three - more than three causes stolen a diode in the tag ber information. When the target tele- the target telephone to ring. Promon nizes the presence of seizes the line and listens a hand- fixed to the goods. phone is not in use and, allowing that for shake I do not propose go the innocent pair are also not in use, the signal from headquarters, which to into other of remote Pole Job will recharge its NiCd battery activates Promon to carry out instruc- applications control techniques because they include those used to from the current on the innocent pair. tions such as recording from specified microphones. recording detonate bombs. Since it is not possible for this or any telephone calls from specified other device to take more than 2 to 3mA numbers. synthesizing out -of-order or engaged signals or run- from a telephone line without pulling the handset is Tracking the line down to fault, it is sometimes ning the recording. If In this particular area. Hollywood has it necessary to take the charge current lifted during these operations, Promon sends a dialling tone to the handset and right. The device hurriedly placed from a number of different lines. the master under a car anti giving away the car's The Pole Joh transmitter, seldom shuts down controller. position to a mob of heavies in a follow- of more than 10nAN , will transmit to a ing car is fact, not fiction. The device is receiver fitted with a carrier switch and larger than the ones usually seen on film a stop start recorder: again the installa- because of the need for batteries, but tion is left unattended. I lowever, as the essentially it is portrayed correctly. receiver can he a few hundred yards Transmitters of this type put out a away from the telephone pole fitted train of pulses which are picked up by with the transmitter, the chances of The world of the following tracking receiver, which discovery are greatly reduced. has four aerials on its roof. A computer Another serious professional ploy is surveillance uses the four inputs to determine direc- to use a parasitic parallel transmitter, became crowded tion and displays the result graphically: operating from the telephone line cur- the Plessey PRS3640 is such a device. I rent but only putting out about ImW,or with crooks, have repeatedly tracked and located less. The range is very short, but this vehicles at ranges up to five miles with does not matter. A repeater is em- charlatans, idiots ployed to receive the signal and then and dangerous the PRS3640. transmit it at high power. on a different More secure and less obtrusive sys- frequency, for long range reception. opportunists tems now exist, but the Plessey device is In the USA current favourite device still one of the best, providing distance is known as the "Brady Bug". This is information as well as direction; with- not strictly a telephone tapping unit but out this, it is easy for a quarry to give a a room -audio gatherer which uses the pursuer the slip. telephone line to get its collected in- Battery life is not quite the problem it formation out to the "listeners''. With a is with other miniature transmitters, "Brady" fitted and one of the other taps since the pulsed nature of the transmis- in place then the listeners get both room Remote control sion conserves power. speech and telephone speech. The So much equipment exists for the re- "Brady" is a small microphone and mote control of electronic devices that audio circuit which fits into a wall often only a simple modification is telephone socket. It puts room sounds needed. For example, the infra-redcon- Them and us (therefore room speech) on to the tele- trols for television receivers or video The gulf between field operatives and phone line in a way which is inaudible to recorders are perfectly usable, as are people in technical support leads quite the human ear. It never switches off. but model radio control systems. predictably to some fairly serious it is never heard by normal users of the The simplest requirement is an on/off clashes of interest. The operative, who telephone line: only the "listeners" control, which a single tone will acti- has just seen the latest Bond film, wants know how to recover the 60k1 iz signals. vate, to switch off a bugging transmitter a device fitted inside his dress ring which A device of considerable enterprise is when the operator is aware that a detec- will transmit colour television and Promon, which is a complete telephone tion team has arrived or when it is clear sound from Istanbul to London. last for exchange in the target premises. using that nothing is going to happen for some six years in continuous operation and the telephone line to transmit room time. simultaneously receive totally secret audio. It covers up to six rooms, with It should be mentioned here that coded messages from his controller on two microphones, hard -wired to Prom - switching a device off is no guarantee holiday in Cuba. on. in each. It usually tits under the that it will not he found. A device called On discovering he is to be issued with floor or in the roof space where mains a non-linear junction detector emits a a device the size of a large hook which power and the telephone line are ac- 600M1-Iz signal at high power and looks will transmit for a maximum of 36 hours cessible: electrically, it is interposed for harmonics of the signal to return. If with a range of 600 yards. the operative between the telephone and the line, the 600M I Iz encounters a semiconduc- immediately goes into spasm and calls and contains a remotely controlled tape tor junction. the presence of harmonics on his stock of expletives. I once heard recorder. indicates the fact. It is true that junc- myself described, over a period of The master controller at headquar- tions other than the semiconductor vari- several minutes, in very imaginative ters causes the target's number to be ety have roughly the same effect. but language indeed; the tirade ended with dialled, whereupon the ringing tone is there is an observable difference. The .. and those are his good points"!

998 ELECTRON ICS WORLD + WIRELESS WORLD October 1989 UNBEATABLE PRICES

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TELECOMMUNICATIONS METERS Hewlett Packard 8970A Noise Figure Meter, Fluke 8050A 41/2 Digit Bench DMM £ 175 26.5GHz £ 3,950 Hewlett Packard 3476A RF Voltmeter, Marconi 2955 Radio Communications Test Set £ 4,500 10kHz-12GHz £ 300 Marconi 2958 Cellular Radio Test Set, TACS £ 6,000 Marconi 2610 True RCS Voltmeter, 5Hz-25kHz £ 650 Wandel & Goltermann PF -1 PCM Bit Error Marconi 8938 AF Power Meter, 20Hz-35kHz £ 450 Rate Tester £ 2,000 Solartron 7150 61/2 Digit Systems DMM £ 525 3? , SPECTRUM ANALYSERS COUNTERS Advantest TR4131, 10kHz-3.5GHz, 7008 Marconi 2438 Counter, DC-520M.Hz f 400 range dynamic £ 5,650 Philips PM6654 Systems Counter, 1.5GHz £ 1,850 Packard Hewlett 3582A, 0.02Hz-25.5kHz, Racal 9921 Counter, 10Hz-3GHz £ 350 dual channel £ 4,750 Hewlett Packard 8568A, 100Hz-1.5GHz, HP/B £13,000 RECORDERS Marconi 2370, 30Hz-110MHz £ 3,750 Sotartron 3530A Orion Alpha Data Logger £ 2,000 Marconi 2383, 100Hz 42GHz £25,000 Watanabe MC6623-6Z 6-channel Chart Recorder £ 1,450 Yokogawa 3033-13 A3 Single -channel Recorder £ 950 NET WORK/SCALAR ANALYSERS Marconi 6500-001 Amplitude Analyser £ 1,950 LOGIC ANALYSERS 7 Hewlett Packard 1630D 43 -channel, 100KHz £ 2,750 GENERATORS Hewlett Packard 1630G 65 -channel, 100MHz £ 3,700 Adret 742A Signal Generator, 100kHz-2.4GHz 7,500 tot a £ Hewlett Packard 1650A 80 -channel, 100MHz £ 3,950 Hewlett Packard 3325A Synthesiser, 21 MHz, Tektronic 1240 72 -channel, 100MHz Mainframe £ 1,700 sweep, HP/B £ 1,950 1_- Hewlett Packard 8340A Sweeper, 10MHz-26.5GHz £23,000 PROGRAMMERS Marconi 2017 Signal Generator, 10kHz-1024MHz £ 4,000 Stag PP39 Portable MOS Programmer £ 300 Marconi 2022 Signal Generator, 1GHz £ 2250 Stag PPZ Universal Programming Mainframe £ 1,850 Wavetek 166 Pulse/Function Generator, 50MHz £ 1,500 Stag Zm2000 Universal PROM Module for PPZ f 995 Wiltron 6663A Microwave Sweeper, 2-40GHz £ 9,500 Stag ZL30 Logic Programmer f 800

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1000 ELECTRONICS WORLD + WIRELESS WORLD October 1989 APPLICATIONS SUMMARY

Switch -mode advantages without the switching OLRD 7 Vcc Sync OL Overload GND Nearly all power supply ICs are either 16 shutdown switch mode or linear so you have the choice between efficient but noisy and Over voltage quiet but inefficient. Cherry now manu- RSD undervoltage Soft start SS remote 12 factures a resonant -mode power supply

IC - the CS3805 - that represents a UV0V15 compromise. Rather than switch, a resonant -mode power supply oscillates: it regulates by VC VC 0 Monastable shifting the oscillation frequency towards or away from the resonant point. Rosc Resonant -mode converters can he phy- 14 sically very small since they can operate 5V regulator Vref Cosc 11 at up to IMIlz. as opposed to the Ton 9 50-100kHz limit for a normal PWM design. 9 UTA This circuit is from the 3805 data SE0 Flip sheet. There is little explanation of the lop circuit in the data sheet but there is a 60UT 88 manual for the 3805 demonstration kit > SPGND that describes components used. Cherry Semiconductor, Clere Electronics, Kingsclere, Newbury, Berkshire RG15 8N L. Tel: 0635 298574.

r1 T1 12 o 1 BYV43 45 I ,Vout .4. 22 n 12 1 aTaTP2 22n fvvvy I I I 1N8 2n2 51 720p 220p 220}r 1113 -Vout BY V 43 3 - 14 -1"Vv' N ` 2n2 51 / 47 IRFP250 BYV 29-200 01 51k 170V BY e 7680p

2n2

220 1N I 3k6 422n 4148 TP1 O IT* T 1180k 33 22k49 29C 3805A 3k9 1k I 1 1 R50 OL 2V - 1N4001 1P2 OLRD OVUV 22k1 2 T4}1/ 300~ .5V R OSC 1N4001 -- AGND VCO VPO10' 7812 BGND BE 11140 . 4N3 ....22N OUTB COSO 470 1k BYV 27-200 100p VN1306 Vcc CNY 17-3 8 9 wom TON ..r47p N3 OUTA 4y7 =220n o 10k 220n 3 2Ó0 =220n /v =22p 51k TP3 n 20n 1300k T100p 7k87 00 1M 1k - ONO 22n

m"1. 2n2

October 1989 ELECTRONICS WORLD + WIRELESS WORLD I1101 We've bridged the gap ...

o A E L ; 5`y ;_/910 4 1 11 - ,r,-12 0. l i3 21 14 / 15 CHANNEL FREO

SPKR SOL USB

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THE COMPLETE DESIGN SERVICE CAD Analogue and digital design, simulations and PCB artwork produced for new or old circuits.

CUSTOM SILICON capability. PALS, Gate Arrays, ASCI's designed and supplied.

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1002 ELECTRONICS WORLD + WIRELESS WOILI.D October 1989 APPLICATIONS SUMMARY

C10 68p R3 SV 15k SK6

-5V 31 EDMACK 1` C2100n VDD input LKB V 106 LDAC SK3(` v C3 VouT ECE6 A A CS C22 DMWR A REFOUT WR/SYNC BB DM/ 15 -V D13/5DATA 811 DMD 14 C5 D12ISCK 812 1 10y D1t/FORMAT Cr REF B~ IN LS A T?V Lh7 DMD1 ICI AD7840 B13 SKI ti ALt-l.. LK5 AGND C r 7 Analogue IC6 output DGND r_l A DMD12 D10/JUSTIFY B14 LK6 DMD11 D9-0 Data Pus 815-25 DMD VS5 A32

79L05 Digital -5V n Out ii ground IC5 GND 100n 5K4 2 4 10 5 9 25.2213 1 11 13. 4 2 9 SK5 A 7

100k pull up resistors ( resistor packs RP1 and RP2 )

from 78 to 84dB distortion and from 76 shown here including PCB foil patterns. Serial/parallel to 80dB signal-to-noise ratio, depend- Signal names on the interface connec- D -to -A converter ing on the version. tor relate to the ADSP2100 DSP chip Designed for both general-purpose but the design is general purpose; tim- board and digital signal processor interfacing, ing details for the converter are given in the 7840 has serial and parallel data the data sheet but there is no informa- Monolithic data converters, other than loading channels; its serial channel can tion about the interface timing require- those specifically for audio, are now be clocked at up to 6MHz. ments. reaching a quality level that allows their Within the 7840 data sheet are inter- distortion and noise specifications to be facing details for a number of DSP Analog devices, Station Avenue, quoted without causing analogue en- devices and 68000/8086 general- Walton -on -Thames, Surrey KT12 IPF. gineers to wince. An example is the purpose processors. There is also a Tel. 0932 232222. AD7840 14bit d -to -a converter with description of the evaluation board

REFOUT REFIN VDD VSS . R

VOUT 14 -bit DAC

3V reference 1 14 DAL latch

AGND 4 Input latch -DGND LDAC Contra 14 CS/SERIAL logic WR/SYNC Parallel and serial Interface ÁD7840

013 SC14TA

October 1989 ELECTRON ICS WORLD + WIRELESS WORLD 1003 APPLICATIONS SUMMARY

From sensor 1 x2 Rx - B

Tx -2 1 x 2

1 x2 Rx- A

Tx -1 1 x 2 To sensor

r---- f1 r5L, ti --Af1

Lr_D

Light Wheatstone ti -Af2 Optical -fibre sensors for general instrumentation applications. like pressure and temperature measurement, are now established, and biomedical/ ti -Bf1 biochemical applications, in which the fibre cladding is replaced with a reagent LED so-called biosensors are emerging - - Ñ fast. ti -Bf2 --- f2 rxj A fibre's optical characteristics drift TRANSMITTERS RECEIVERS FILTERS 0/P with temperature and the light changes in an optical -fibre sensor are minute. To the electronics engineer, the most obvious measurement configuration would be an electrical Wheatstone bridge, but the optical Wheatstone solution shown here avoids the additional +5V Vin Vout -5V errors that occur when converting the ToVor GND light signals to electrical ones. see table 1 For many applications the optical 2100n bridge would have been prohibitively =100n ,4I yl I expensive were it not for developments V+ ONO Vin1 m2 D Vout V- in optical waveguides in glass. A brochure front Corning outlines LMF 90 4th -order waveguides. their fx 1 optical applications bandpass fo in telecommunications and instru- LDxR R = 33.3,50 or100 mentation, and the company's wave - 1 see table 1 guide products which include both cus- Level Non -overlapping tom and standard parts. The brochure's '--11 shift clock generator LD=2.596 or716 see pin description full title is "Photocor integrated optic custom components." Apora, 21 Victoria Avenue, Harrogate, Yorkshire IIG/ 5RD. Tel: 0423569 307. "A/W W R LD XTAL2 XTAL1 CK XLS Switched -capacitor 7 ToV+V br ONO To "- .5V see table 1 or ONO notch filter +5V see pin description Et'nl clock in - 1-11-11-1- -5V This notch filter needs no external components for defining its response and it needs only variation in clock frequency to move the notch centre. Clock -to - centre -frequency ratio, attenuation and Operation of LMF90 programming pins. Values given are for nominal levels of attenuation. notch width are all programmable. In the data sheet for the LMF90 R V (foo,/fo = 100) GND (fox/fo = 50) V' (foiK/fo = 33.33) fourth -order elliptic filter IC are ten D 'N A BW/fo SBW/f0 A BW/fo SBW/f0 Am; BW/fo SBW/fo (dB (dB) - (dBg applications circuits showing how to the 30 0.12 0.019 -30 0.12 0.019 -30 0.12 0.019 operate device from single or dual GND 30 026 0.040 -30 026 0.040 -30 0.26 0.040 supplies and how to use the crystal or V' 30 0.55 0.082 -30 0.55 0.082 -30 0.55 0.082 35 0.12 0.010 35 0.12 0.010 35 0.12 0.010 external clock options. GND ONO 40 026 0.024 40 026 0.024 40 026 0.024 National Semiconductor, The Maples, V' 40 0.55 0.050 40 0.55 0.050 40 0.55 0.050 Kembrey Park, Swindon, Wiltshire SN2 6 UT. Tel:: 0793 614141.

1004 ELECTRONICS WORLD + WIRELESS WORLD October 1989 SPICE AGE Non -Linear Analogue Circuit WAN D J & M Computers specialize in all Simulator £245 complete redundant Electronic Equipment, working Those Engineers have a reputation for supplying the best value -for-money in microcomputer -based circuit simulation software. Just look at what the new fully -integrated SPICE or not, i.e. Advanced Graphics Environment (AGE) package offers in ease -of -use, performance, and facilities: Computer equipment and peripherals SPICEAGE performs four types of analysis simply, speedily, and accurately: (resistors I.C's) Module 1- Frequency response Module 3 -Transient analysis Components to Module 2- DC quiescent analysis Module 4- Fourier analysis Test equipment

1 Frequency response Modems u SPICEAGE provides a clever hidden benefit. It first solves for circuit quiesc- Printer circuit cards ence and only when the operating point is Redundant stocks established does It release the correct small -signal results. This essential con- End of job lots cept is featured in all Those Engineers' software. Numerical and graphical (log 8 Cable tin) impedance, gain and phase results can be generated. A 'probe node' feature Factory clearances allows the output nodes to be changed. If you have redundant equipment now or Output may be either dB or volts; the zero dB reference can be defined in six differ- in the future, would you contact us. We Frequency response of a low pass fitter ent ways. circuit woud be pleased to price and collect it at

2 DC Quiescent analysis our own expense. SPICEAGE analyses DC voltages in is 1 '.. 1 1:. any network and useful, for example, for 41/1 11 ::241:r1 setting transistor bias. Non-linear compo- 4.111111 u 1.111111.ü 1:1111 -1.4111.1d 1..1111 nents such as transistors and diodes are ü 12: v i:ia u catered for. (The disk library of network Computer models contains many commonly -used . components - see below). This type of analysis is ideal for confirming bias condi- Eight Acres, Maldon Road, Wickham tions and establishing clipping margin akKai2._ Bishops, Witham, Essex. prior to performing a transient analysis. . u Tabular results are given for each node; Telephone: Maldon (0621) 892701 the reference node is user -selectable. DC conditions within model of 741 circuit Fax: (0621) 891414

3 Transient analysis CIRCLE 11íO. 49 ON REPLY CARD The transient response arising from a wide range of inputs can be examined. 7 types a1 of excitation are offered (impulse, sine wave, step, triangle, ramp, square, R.F. and pulse train): the parameters of each are user-definable. Reactive components may be pre -charged to steady-state con- ACCESSORIES dition. Up to 13 voltage generators and current generators may be connected. FILTERS, ATTENUATORS, Sweep time is adjustable. Up to 4 probe nodes are allowed, and simultaneous COUPLERS ETC. Impulse response of low pass filter plots permit easy comparison of results. transient analysis) A CONNECTORS 4 Fourier analyses SPICEAGE performs Fourier trans- forms on transient analysis data. This AND CABLES allows users to examine transient analysis waveforms for the most prevalent fre- V CABLE ASSEMBLIES AND quency components (amplitude is plotted against frequency). Functions as a simple TEST LEADS MADE TO spectrum analyser for snapshot of transients. Automatically interpolates from ORDER transient analysis data and handles up to 512 data values. Allows examination of Coaxial or Multiway. waveform through different windows. E Powerful analytical function is extremely RF, video, audio and data easy to use. Spectrum of rectangular pulse train (Fourier analysis) Double braid and tough PTFE coaxial cables. Customers already include If your work involves designing, developing or verifying analogue or digital circuits, you will wonder how you ever several universities and managed without Those Engineers circuit Simulation polytechnics, government Software. departments, broadcasters and A good range of properly supported and proven programs is BT - Cellnet. available and our expert staff are at your service. WAVEBAND úIosQ ELECTRONICS HETInw I c 3 Lon Howell, Denbigh, Clwyd LL16 4AN. OCCita [k anu leo *coa ~01. Qssw oa aC,Z./3 coa Telephone: 01-435 2771 Fax: 01-435 3757 Tel: 074 571 2777.

CIRCLE NO. 44 ON REPLY CARD CIRCLE NO. 48 ON REPLY CARD

October 1989 ELECTRONICS WORLD + W IRELESS WORLD 1005 10 SENSORS C %SYSTEMS

Sensors & Systems, the international transducer exhibition and conference, promises an unrivalled opportunity for catching up with the latest products and techniques. This year's event takes place at the Wembley Conference Centre, October 24, 25 and 26. On these pages we present some highlights of the technical sessions. `dip 111 SENSORS THE INTERNATIONAL TRANSDUCER EXHIBITION & CONFERENCE

WEMBLEY CONFERENCE CENTRE OCTOBER 24 25 26 1989

Sensors and systems Robot wrist sensor: a team from Delft University describes a capacitive wrist ¡ sensor for multi -axis force and torque r sensing in robots. This replaces conven- f tional strain -gauge sensors. Robots equipped with the sensor can he used in applications where a tool must he moved over a curved surface while being pressed against it with a constant force. R.F. Wolffenhuttel et al.. Laboratory for Electronic Instrumenta- tion. Mekelweg 4. 2628 Cl) Delft, The Netherlands.

Brushless 360° angle sensor (pictured right): a stand-alone analogue shaft angle transducer, based On a rotary variable auto -transformer. is now avail- A cost-effective solution to shaft angle sensing: the Komi brushless sensor developed able in commercial form. Radiodetec- by Radiodetection. It can also be used as an inclinometer. tion Ltd, Western Drive. Bristol: tel. 0272-839581. ocean basins, carrying chemical. geo- ultra -violet, elect rochemical. ionization logical and physical sensors. Previous and electron -capture types. Brian Mil- Liquid/solid mixtures: Dr John Coult- investigations of this sort have meant ler. 22 Ashhourne Road, Runcorn. hard Byrne and Dr Benjamin of Tees- lowering an instrument platform trout a Cheshire WA7 41 1): te1.09285-65884. side Polytechnic survey techniques for ship, which then had to maintain its measuring the flow of granular or pow- station for up to eight hours. Dr Varney Open path gas detection: this new dered fuels using electrostatic, gamma also mentions some unique sensors for approach to detecting the build-up of ray and X-ray sensors. They also de- detecting trace substances in ocean hydrocarbon gases in hazardous con- scribe mass -sensing methods based on waters. Department of Oceanography. centrations is said to avoid the problems ultrasound. School of Information Southampton University. Southampton which arise with single -point sensors - Engineering. Teesside Polytechnic, SO9 5N I -I . siting these can he crucial to their effec- Middlesbrough. Cleveland TS 13RA. tiveness. By means of a novel dual - Toxic gases in the workplace: new reg- wavelength technique using infra -red ulations coming into force this month beams. it is possible to monitor a sub- Environmental sensors make it necessary to monitor the air in stantial area with a single instrument. Sensing the oceans: Dr Mark Varney of workplaces to assess the risk of expo- Sieger l.td. 31 Nuffield Estate. Poole. Southampton University describes the sure. A consultant, Brian Miller. sur- Dorset 111-117 7 RZ; tel. 0202-676161. Autosub. an underwater vehicle which veys some of the instrumentation avail- will he able to dive independently to the able for personal. portable and fixed I3iosensors for pollution monitoring: depths of the oceans and travel across use; among the sensors are infra -red, the marriage between microbiology and

ELECTRONICS WORLD + WI REI.ESS WORLD October 1989 ¡ill SENSORS

..SYSTEMS

electrochemistry offers enormous potential in areas such as environmental monitoring. Prof. David Rawson of ACTIVITIES AT SENSORS & SYSTEMS

Luton College of I ligher Education describes progress with transducers In parallel with the main exhibition and conference, a variety of other activities has based on living cells such as those of been arranged. bacteria and algae and considers some of their possible applications. Theatre Workshop. Hands-on demonstrations by conference speakers and exhibitors will take place on all three days of the show. at the Theatre Workshop in the main exhibition area. Morning Optical -fibre sensors and afternoon sessions have been designed to Commercially available devices: a re- complement each day's conference programme. cent survey by ERA Technology Ltd For example, a visitor could spend the morning identified over 200 potential manufac- listening to conference presentations on, say, optical fibre sensors, and the afternoon seeing turers of optical -fibre sensors world- them demonstrated in the Workshop. wide. Dr S.D. Crossley of Bradford University reviews current commercial R&D Village. New devices and applications from devices and others which are in the final universities and leading research centres in the stages of development. UK will be on show in the R&D Village. This feature, sponsored by the Department of Trade and Industry, aims to highlight the importance of Distributed temperature sensor: Geoff collabcration between research and industry. Acc elerat on sensor, with a poppy seed Gamble describes a way of using stan- loading the paddle (scanning electron dard multi -mode optical fibre as a One -day course. To accompany the show. a micrograph by NovaSensor). temperature sensor. Using optical time - one -day course on silicon sensors and ^ . domain reflectometry. his system (pic- microstructures is being organized, with the aim tured below) monitors hack -scatter to of increasing awareness among technologists and business managers. Silicon m cromachining, give a temperature profile over the according to some, is creating the same kind of entire length of an optical fibre up to revolution that led to the emergence of Silicon 2km long. York Ventures and Special Valley 30 years ago. Micromachining, the three- Optical Products Ltd, York House, dimensional sculpting of silicon using School Lane, Chandlers Ford. Hamp- semiconductor batch processing technology, is the foundation of a new generation of diverse shire S05 3DG; tel. 0703-26041 I . sensor -based products which could change our lives in the coming years. Topics covered will include the birth and evolution of silicon sensor techno ogy. silicon Catheter sensor chips surrounded by salt processing and micromachining, advanced crystals (NovaSensor). f silicon sensor designs and the emerging technology of silicon microstructures. The all -day Sensors & Systems, the international course, 13 be held on Wednesday, October 25, transducer exhibition and Conference. will take will be presented by Dr Janusz Bryzek and Dr pla.:e at the Wembley Conference Centre, Phillip 3arth of NovaSensor (USA-tel. 0101-415 October 24-26, 1989. Organizers are Trident 490 9100: fax 0101 415 770 064E) Fee is £ 125, Inte rnatioral Exhibitions Ltd, 21 Plymouth Road, including lunch, refreshments and course notes. Tavistock. Devon PL 19 8AU: tel. 0822.614671.

Meet Electronics World + Wireless World at the exhit ition. Stand Lla in the upper display area.

Optical -fibre hybrid sensors: Walter Gross of Siemens AG presents a hybrid sensor for measuring temperature with Infrared and optical 0.2% accuracy. This unit obtains its sensors power from the cable using a optically, Optical rotation sensors: ring laser specially developed optical -to -electrical .. gyroscopes and optical -fibre gyroscopes which to converter can deliver up show considerable promise for applica- 150mW to the sensor head. Advantages tions in inertial navigation systems, DC isolation and a reduced risk are of being potentially cheaper and more reli- explosion in hazardous environments. able than conventional gyros. An Siemens AG, Paul Gossen Strasse 100, assessment of both types is provided by D-8520 West Germany. Erlangen, Dr John Nuttall, of the Ferranti team behind the Ariane rocket's navigational -frequency a Measuring low vibration: successes. Ferranti International, Sil- passive optical accelerometer (right) verknowes, Edinburgh EH4 4 AD; tel. has been developed for measuring low - 031-332 241 1. frequency (0.1-10Hz), large amplitude (10-15mm) movement of offshore structures. Dr Robert Jones. Cambridge Probing plastics: as packaging materials Consultants Ltd. 0223-420024. grow ever more complex. modern tech - - -

October 1989 ELECTRONICS WORLD + WIRELESS WORLD 1007 SokSENSORS C 1r SYSTEMS

piques such as multi -layer co -extrusion of plastics films (for example. nylon with polyethylene) present new challenges to the engineer. In producing the films, a essential harrier layers must he of the right thickness and optical flatness is rL w - important. Thickness can he monitored on the production line by a method based on near -infrared absorption, which in many cases can provide sepa- i rate measurements of individual layers. , . I)r I.R. Benson. Infrared Engineering OAff V17:T4,1, 41 Ltd. The Causeway, Maldon, Essex: -. tel. 0621-852244.

Laser -based pyrometer: temperature

readings in industrial furnaces. such as -2 those used for steel -making or petro- chemicals, tend to he erroneously high u because of energy emitted by the hot furnace walls. A system now in commercial production eliminates this error by making it possible to measure directly the emissivity Of opaque, diffuse targets. Graham Kilford and I)r E.K. Matthews. Emmallex Ltd, 192 Main - Road. Stafford ST17 (MN: tel. 0755- Bolted to this pipe -stack is a gamma -ray density sensor, designed in Britain for 665566. manufacture by Kay Ray Products of Chicago (Rosemount Ltd). the University and at the Admiralty venience of the latest generation of Surface resistivity and reflectivity: Research Establishment, Holton personal computers. National Instru- I).M. Calcutt and 1)r R..I. Batt of Heath. ments. tel. 0101-512 25(191 19: fax 010'- Portsmouth Polytechnic describe a 512 335 2569. pyroelectric method of measuring thin Calorimetric flow -sensing: Giinther Weber reviews flow sensors and their conducting films. Digital measurement devices: by the design. both intrusive and non -intrusive use of digital transmission in place of the types. A promising area of application conventional current loop. intelligent for flow -sensors is likely Smart sensors, solid-state calorimetric measurement devices can he integrated to be the industry. Weber automobile into distributed control systems. In this sensors Sensortechnik Gmbl-I, Kollmar, D- way, the system can he said to be 2201 Germany; tel. ((11049) 4125 591. Silicon Microstructures:advanced distributed right down to the process micromachining and other processes Measuring fluid density: Mark Reales itself. Ilarvey Dearden, Foxboro GB are bringing new silicon devices such as and Tim Williams present a Ltd, Devon PLI9 SAU; tel. 0822 a silicon accelerometer, which offers microprocessor -based instrument 614671. improved performance at a traction of which uses a gamma -ray absorption the cost of conventional devices, and a Field instrumentation: Lynne Rolfe in- variety of special-purpose sensors. method to determine the density of a pipe. whole troduces two technologies for digital actuators and Miniature mechanical ele- fluid in a process The instrument is bolted to the pipeline and communications between transmitters. ments. Dr .lames Knutti of IC Sensors com- can be read and configured at a remote control systems and hand-held Inc. describes these devices and the municators: Rosemount Ltd's Hart Pro- production techniques which make terminal vía a digital communications Heath Place. tocol and Fieldbus, all all -digital Eure- them possible. Eurosensor Computer link. Rosemount Ltd, I3ognor Regis. Sussex: tel. 0243-863121. ka proposal. Rosemount l.td. Heath Controls Ltd. 20-24 Kirby Street, Lon- Place. Bognor Regis. Sussex. tel. (1243- don EC I N 8TS: tel. 01-405 6060. 563121.

Thick -film gas sensors: organic semi- Digital systems Gas detection: Mike Scott of Sieger Ltd conductors such as the metal -based Virtual instrumentation: I)r James describes his company's digital systems phthalocyanines make highly sensitive Truchard and Richard I-louse of Nation- for gas detection in the offshore oil gas sensors, but they lack discrimina- al Instruments Corporation (USA) industry. These are based on a network tion. Dr .1. K. Atkinson, of the Depart- show how measuring instruments can of intelligent transducers addressed ment of Electronics and Computer Sci- he constructed on the computer screen. through a master -slave protocol de- ence at Southampton University. has With plug-in data acquisition boards veloped in co-operation with South- been trying to produce sensor systems replacing dedicated instruments. the ampton University. Sieger Ltd. 31 Nuf- which can distinguish between different user call exploit to the full the graphics field Estate. Poole. Dorset I31-117 7RZ: gases - with the help of collaborators at capability. processing power and con- tel. (1202-676161.

1008 ELEC' RON ICS WORLD + WIRELESS WORLD October 1989 . . : SE°

, -f110°",(;/0I' ? , 1 85 , p..r r- - . No M W/1111'5 - THE RING AND EXHIBIT - CONFERENCE HOTLINE 'if0822614671

COMPETITIONS LETS INNOVATIONS SENSORS ,DETAILED. & , KNOW EXACTLYSWHAT'S CONFERENCE PRODUCT GUIDE YOU REAL WORLD HAPPENING IN THE THEATRE WORKSHOP THE Sensors & Systems FEATURING offers excitement and A uniquely dedicated THAN NEW NEWER For dedicated delegates answers. It's your one - event, it assembles the there's a full stop opportunity to complete spectrum of Don't miss the R & D international conference problem -solve, to keep new and established Village (sponsored by plus a programme of up to date with the latest sensors & transducers the DTI) for your pre- hands-on demos open in products and plus instrumentation for production preview of to all. innovative systems. recording, controlling devices and applic- and reacting to ations from the leading analogue and digital research establishments input. in the UK.

11\ 5 .. ERNA MAI SETHE

*El1111 LONDO CENTRE CONFERENCE 1989 Trident International Exhibitions Ltd. WEMBLEY 24 21125 II 26 21 Plymouth Road OCTOBER Tavistock Devon PL19 8AU England GYNERE Yoc/ ARE" R/CiwrINTouCN! Tel: 0822 614671 Fax: 0822 614818

CIRCLE NO. 39 ON REPLY CARD SENSORS Better magnetic sensors Alan Collins of MR Sensors shows how these thin-film devices can, with advantage, replace inductive sensors in the measurement of movement and velocity

Ferromagnetic thin-film magneto - passing a constant current I through the resistive sensors are solid-state magnetoresistive stripe: the magnetic magnetic -field sensors for sensing field is then detected as a change in and measuring. Although the voltage v across the device. magnetoresistive effect in ferromagne- The relationship between the field tic materials has been known for more and field -dependent output voltage (y)

than 100 years, it is only recently that we is non-linear. 1 lowever, the sensor may Conductor stripes have exploited the effect in thin film he linearized by biasing the sensor in the sensors. linear region by means of biasing field 11 The simplest form of a ferromagnetic which rotates the magnetization within Fig. 3. Linearization using "barber- magnetoresistive field sensor is shown the stripe to an angle of 45° to the stripe pole"structure to rotate current in Fig. I. The sensor's operation relies length. H may be provided for example, direction inside stripe. on the fact that. when a magnetoresis- by a permanent magnet. The signal tive thin-film stripe is placed in a output from the detector is then directly magnetic field which is in the plane of proportional to the signal field which is pole" device. In these devices the cur- the stripe and perpendicular to the superimposed on t he bias field. rent direction within the stripe is ro- stripe's length, a change in resistivity of Other methods exist of biasing the tated (rather than the magnetization) the stripe occurs. sensor, some of which extend the linear by depositing narrow gold stripes over The magnitude of the change in re - region of the device. such as the "barber the magnetoresistive stripe at 45° to the length, as shown in Fig. 3. The transfer characteristic of a "barber pole" magnet resistor is shown in Fig. 4. Electrical conductors Single, multiple and bridge detectors Constant-current Magnetoresistive with a wide range of dimensions, satur- source stripe ating fields (

Fig. I. Basic magnetoresistive sensor. Changing magnetic field varies resistivity of'magnetic stripe. 60 -vo 40- sistance.lt of the basic sensor stripe is a function of the applied field amplitude 20-

I -I as shown in Fig. 2. The field 11s;,,

I I I I t l t t necessary to saturate the change in -8 -6 -4 -1 2 4 6 8 resistance, the maximum change in re- --20 H sistance R, the zero field resist- - -1.0 ance. and the sensitivity dR/dH at any point on the characteristic may be tail- --60 ored by a suitable choice of the magnetoresistive stripe's material and dimen- Fig. 4. Linearized transfer sions. Fig. 2. Characteristic of sensor. characteristic of barber -pole current The sensor is normally operated by Resistance is non-linear. rotation.

lull ELECTRONICS & WIRELESS WORLD October 1989 COMPUTER APPRECIATION M & B RADIO (LEEDS) Theatre, 30/31 Northgate, Canterbury, Kent CT1 1BL The Penny THE NORTH'S LEADING USED TEST -EQUIPMENT DEALER Telephone: (0227) 470512 Oscilloscopes Clymer 1585 AF Poner Meter f85 TB 1599 Racal 409 Meter 1210 MHZ 1150 HEWLETT PACKARD MODEL 550IA LASTER TRANSDUCER. With prezoelectrlc tuning for precise control Tektronix 470 200MHZ Dual Trade Delayed i Test 1200 in measuring applications. With various minors and accessories £250.00 Tektronix 2445 150MHZ Four Trace Delayed TB £1450 (Radford 1002 OMS,' Audi Set of wavelength £50 VICKERS INSTRUMENTS MODEL M17 METALLURGICAL MICROSCOPE with binoculars/micrographic head Tektronix 7503 Main Frame 7853 7A18 7018 1900 HP 202C Audio O.. ator alum nator An £75 and all eyepieces With 4 Microplan objectives 8 Nomarskl interference contrast, variable etc Tektronix 475A 250MHZ Dual Trace Delayed TB £750 Farnell LFM2 Audio Generator £75 immaculate instrument from the clean.room of a major semiconductor manufacturer New cost over C6500 00 1935A 35MHZ Dual Trace Portable £350 Farnell TM4 Microvolt Meter £1250.00 Tektronix Tektronix T9,2 Portable Storage 14(0 Levell TM3 Microvolt Meter £35 Dual Trace £225 Leven TG 150 Audio Oscillator £20 old with negative ion capability Tektronix 1915 I SMHZ KRATOS MS30 DOUBLE BEAM MASS SPECTROMETER. Approximately 8 years 1450 HP 4001 AC Voltmeter £150 probes 8 with gas chromatograph inlet HP 1703A Dual Trace Storage Oscilloscope 8 fast atom bombardment (FAB). With gas & direct introduction sample 150 recorder An HP 1715A 2(OMHZ Dual Trace with DVM Opt 185,5 HP 34009 RMS Voltmeter £ system Output spectra are available directly via a HEWLETT PACKARD storage display 8 a UV 4074 HP 17400 1GCMH2 Dual Trace Quill Trace 16(0 HP 3403C True RMS Voltmeters from £300 on-ºne DATA GENERAL DS60 computer system. which includes a graphics printer 8 two TEKTRONIX New £455 UPM550 10 HZ 1 MHZ AF Meter L195 output. The various sections of the instrument may be available separately A new high flux Kikusi 5060 nOMHZ Oscilloscope Booed as £ennheiser terminals, analyses £450 magnet was fitted shortly before the instrument was decommissioned P.O.A. Trio C52100117CMHZ Dual Timebase £425 Fadford LDO4E Oscillator Phaps 34.2 10MHZ True Dual Trac. £155 DAWE 4I9C White Nose Generator £45 265 POWER SUPPLY and Random None Generator £195 SPECTRA PHYSICS MODEL 164 4 WATT ARGON ION LASER with MODEL Ph Ps 3234 10MHZ Storage Oscilloscope £3(0 Cell RAD 1383 C1500.00 transformer for 3 phase supply. Suitable for research applications or a light show, Teleguipment D755 50MHZ Dual Trace Delayed -B £2'5 Gen Rad 13908 Random Noise Generator £75 Teteguiprrent D83 50MHZ Dual Ira. e Delayed TB £250 Fadiomet5er SMGI Stereo Generator £150 HELIUM NEON LASER with power supply. A powerful Helium Neon SPECTRA PHYSICS MODEL 164A 30mW Te leouipnrem 081 15MHZ Dual Tra. e f1.5 hP 538aA 80MHZ Freg Counter 1100 holography £350.00 laser ideally suited for Telegulprnert 01016 10MHZ Dual Trace £135 Racal 9839 570 MHZ Freg Counter £135 Cossor [DUI 50 35MHZ Dkuai Trace Delayed TB 1155 Pacer 9915M 560MHZ Free Counter £195 LUMONICS SYSTEM 2000 RUBY LASER wah 0 -switch, temperature controlled KOP frequency doubler, output low I vafsu SC7I03 10HZ-1 GHZ New Free Counter £425 monitor 0 per pulse, O -swathed output. 6 ppm Suitable for holography involving moving objects A 3 Joule Herconi 2432A Free Counter £400 power He/Ne laser for mirror alignment and all manuals are included Current new price of equivalent model SIGNAL GENERATOR AM FM £400 HP34650 Digital Mulhmeter £150 exceeds £15000 00. £3500.00 Marconi Tr 2308 I OkHZ 51 OMHZ Marconi 772002 10kHZ 72MHZ AM FM £100 Lolatron.Schlumberger 7065 IEEE Voltmeter £350 HEWLETT PACKARD Model 5045A digital tC tester with CONTREL Model H310 automatic handler. With Marconi T=2015 10KHZ.520MHZ AM FM £375 Pacal VHF RT Calibrator f25 failure IEEE interface 8 print out of test results either pass -fail or lull diagnostic including pin voltages at point of Marconi TF2015 with TF2171 Synchronizer £500 Racal VHF -UHF Calibrator 9054 £75 mag. test programs for 74 series With full complement of pin dnver cards 8 complete with substantial library of card Marconi TF2012 UHF 400MHZ-520',HZ FM £ISO AIM 401 LCR Comparator Dalabridge £275 testing of ICs which are sorted into 2 bins Price includes TTL 8 other ICs CONTREL handler allows fully automatt Marconi TF1086 10 470MHZ AM FM í1r5 Wayne Keir Comp Meter Set £ 300 fully operational) for maintenance backup Very useful for recycling eves - originally a second HP5045A (believed Marconi TF995 1.220MHZ AM FM £35 Philips Pulse Generator IHZ 100MHZ £65 00 £150.00 cost over £6000 Philips PÁ5324 110MHZ AM FM with Sweeper £175 HP VHF Oscillator 32008 1050060e £200 Racal 9015062 I OKHZ.160MHZ Synhesized £500 HP 65113 Test Oscillator 1150 ITT PERFECTOR TELEX MACHINE. With 32k memory, screen with slow scrolling, keyboard etc -together with Gen Rad 13108 2HZ 2MHZ Oscillator £95 operators and service manuals £99.50 TEST EQUIPMENT Gen Rad 1362 UHF Oscillator 220 820MHZ £75 BIOMATION Model 810D LOGIC ANALYSER. Combines with any oscilloscope to provide 8 channel logic Marconi 72950 Mobile Radio Test Set £500 HP 501 IT Logic Trouble Shooting Kit £ 100 analyser. Sue and colour to match Tektronix 400 series portables £75.00 Marconi TF2331 Distortion Meter £250 Bradley 156 Oscilloscope Calibrator 4200 Marconi 7=2000 AF Oscillator An £250 Marconi TF 1245-1247 1248 Q Meter £300 new. Needs easy modification DIGITAL O-BUS, box, power supply, and 8 . dual slot backplane all brand 72005R Dual AF AF Oscillator 4 Att £325 Thorn WG83 R TV Sync Pulse Generator £195 £75.00 Marconi (14 wirewrap connections) to update. Marconi TF2160 or Monitored Attenuate! £190 Brandenburg 470 0.2 5KV Power Supply £75 Marconi TF 1313 01% LCR Bridge £150 Cohrent Radiative 212 Power Meter LISO Model 4051 intelligent graphics display wah BASIC in ROM and RCA tape cartridge drive Good TEKTRONIX Marconi 712120 Waveform Generator £225 fluke 616,A Free Synthesizer 0.30MHZ £150 tube and useful for maintenance purposes £99.50 Marconi 72300 Modulation Meter £175 1V( IN MKIII Multimeter £60 new £330 rP Rs 128 Freg Meier 2640GHZ LIAD ADLER/ROYAL Office Master 2000 DAISY WHEEL PRINTERS. 20 cps. Full IBM 8 DIABLO 630 Marconi 72303 Modulator Meter as TRIUMPH rd2A Att 40GH7 £ 100 COMPATIBILITY. CENTRONICS INTERFACE. Features include underscore, bold subscripts, superscripts Marconi 72600 AF MAlrvolt Meter £30 rP R Variable 26 to 40112 £50 underline etc 132 column; micro proportioned spacing. Complete with typewheel 8 ribbon, manufactured to Marconi TF2604 RF Millivolt Meter 11500MHZ) £75 HP 4320 Crystal Detector 10MHZ 12 at 43000 highest standards in West Germany by Europe s largest typewriter manufacturer 8 offered elsewhere over Marconi TF2650 FIT Mutt Traders £ 1.00 HPI820 85588 Spectrum Analyser I 1 50112 £350 00 Ex demonstration condition Guaranteed 90 days C69.00 (C6.50 care) Marconi TFI 065 Radintelepnone Rf/AF Power - Mono 150 4P141T 85538 85520 l IOMHZ Spectrum Analyser Marconi 7(460 RF Power Meter 10MHZ 40GHZ f250 £2000 Including free software disc for IBM or MATMOS PC. PLESSEY Model 124 V22/V22 bis 2400 Baud MODEM. Adrel Codasync 10MHZ Syth-Geneetor £195 HP8443A Tracking Generator £650 modern featuring the latest technology 8 the highest possible data rate over the ordinary Compact, automatic Dymar 1795 Mod Meter 3 480 MHZ Mains.Batt £65 HP8750A Normalizes £500 phone system Offers. both V22 8 V22 bis compatibility 12002400 Baud operation with auto bit rate re...ognition operation on both ordinary phone (PSTN) 8 private circuit (PC) auto call and auto answer, duplex operation line. allowing simultaneous transmission 8 reception of data at 2400 Baud in both directions over a single phone compact size(B" x 9' a 2112"), 81 approved 8 suitable for new PRESTEL V22bis service £59.53 (care. £5.00) ALL PRICES PLUS VAT AND CARRIAGE

Please note: *VAT & carriage (also + VAT) must be added to all prices. 86 Bishopgate Street, Leeds LS1 4BB. *Guarantees vary from item to item, please enquire before purchase. *A full stock list with many other items and special offers is available on request. Tel: 0532 435649. Fax: (0532) 426881

REPLY CARD CIRCLE NO. 32 ON REPLY CARD CIRCLE NO. 17 ON With 48 years' experience in the design and manufacture of South Midlands several huhcred thousand transformers we can supply: SMC Communications AUDIO FREQUENCY TRANSFORMERS OF EVERY TYPE

RADIO YOU NAME IT!. - WE MAKE IT! TRANSCEIVERS/RECEIVERS OUR RANGE INCLUDES: SMC the leading European specialist in general types). Microphone Splitter/Combintr transfor- modular I-- ._ - tr.y. Microphone transformers (all radio communications have developed Injection transformers for Guitars. systems for rapid delivery, particularly useful 13 r mers. Input and Output transformer. Direct for emergencies, disasters, political unrest and C, Mull -Secondary oubut transformets. Bridging transforme's. Line transformers. aid concerns. This can consist of rugged, simple ól r r to B.T. Isoating Test Wiecification. Tapped impedance match- FTBOC with a Linet-ansformers to use, HF transceivers i.e. the y Audio Mixing Desk transfor- frequency range of 1.5-30MHz used with either ing tansformers. Gramophoie PIck.3p transformers. one of the SMC basic wide band antennas, or fners (all types). Miniature tansforrne"a. Microminiature transformers for PCB more efficient, the multi spot frequency FT80C moLnting. Experimental transformers. Ultra low frequency transformers. Ultra antennas complete with transportable masts. linear and other transformers for Va ve Amplifiers up to 500 watts. Inductive Loop More powerful and complex transceivers are Amplifiers to 100 volt line also available. transforrners. Smoc hing Clokes. Filter, Inductors, 1.000 watts), 100 volt line transformers to Where monitoring or reception is required then risk transformers (from a few watts up to either the FRG8800 HF receiver with VHF option speakers. Speaker' -natchin3 trans'orners (all powers), Column Loud -speaker or the FRG9600 VHF, UHF all mode scanning transformers up to 300 wattsor more. receiver are available with proven quality, 41, rt sensitivity and reliability, at realistic prices. V1e can design for RECORDING QUALITY, STUDIO QUALITY, HI-FI QUALITY OR P.A. QUALIT'. OUR PRICES ARE HIGHLY COMPETITIVE AND ANTENNAS FRG8800 WE SUPPLY LARGE OR SMALL QUANTITIES AND EVEN SINGLE The TWB2530 and TEB3 are just two samples of TRANSFORMERS. Many standard types are in stock and normal dispatch the large range HF, VHF and UHF antennas times are short and sensible available from SMC. Both have been specifically designed for users with very different CUR CLIENTS COVER A IAFGE NUMBER OF BROADCASTING requirements showing the breadth of our MIXING'DESK MANLFACTURERS, RECORDING STUDIOS, transportable TWB2530 AU-HORITIES, capability. The rugged AND PUBLIC ADDRESS FIRMS. is a full self-contained extremely lightweight, HI -Fl ENTHUSIASTS, BA'JD GROUPS yet tough enough to withstand rough handling Expxt is a speciality and we. have overseas clients in the COMMONWEALTH, and quick assembly in adverse terrain. TWB2530 EEC, USA, MIDDLE EAST, etc. frequency HF beam The TEB series of spot enables 'us .to post antennas give excellent forward gain, rugged Send for Our questionnaire whch when completed, construction for long life, at a cost effective quclations by return price. If you require further information on the 300 various support mounts, HF. VHF or UHF antennas, simply call for our new shortform S OWTER catalogue. Both can be supplied with the most efficient TRAHSFORMERS antennas and desirable accessories. TEB3 r`

SMC LTD, SM HOUSE, SCHOOL CLOSE, CHANDLERS FORD PO Box 36, Ipswich IP1 2EL, England. INDUSTRIAL ESTATE, EASTLEIGH, HANTS S05 3BY. Phone: 0473 252794 & 0473 219390 - Tel: (0703) 255111. Telex: 477351 SMCOMM G. Fax: 0703 263507 Telex: 987703G Fax: 0473 236188 ENTER 260N REPLY CARD CIRCLE NO. 41 ON REPLY CARD 1011 October 1989 ELECTRONICS WORLD +WIRELESSWOR-LD SENSORS

security cards, and tickets. Because the Head transfer function Head output pulses sensor detects magnetic field amplitude for 0 010 data I I (whereas inductive read heads detect the rate of change of field dH/dt), the (a) (Cl output is independent of the speed of the recorded medium past the sensor. +H Magnetoresistive sensors are, there- 1 Mark coin Al I+H' 100,1, fore. suitable for use as read heads in hand-held magnetic swipe and , o card tick- 0 10 2Q 30 40 50 et readers. POSITION OF COIN (mm) 0 Ib) The basic characteristics of the un- Fig. 8. Example ofcoin scan, showing biased magnetoresistive sensor head en- difference between a standard British o able improved decoding techniques to coin and the closest foreign one. Field changes for he employed which, to date, have not put from the head is a series of single - pattern 0010 been fully exploited. For each transition polarity pulses, as shown in Fig. 5(c), in NRZ recording, the field detected by Fig. 5. Transfer characteristic of rather than the pulses of alternating the head changes from -I l' to H' (Fig. magnetoresistive head. Head does not polarity obtained from an inductive 5, which shows for illustrative purposes differentiate between positive and head. a convenient representation of the field negative excursions, so output is a train The sensors can he used in a wide changes arising from an encoded data ofsingle-polarity pulses. range of applications. For example, pattern). As the magnetoresistive head they are used to advantage in the requirement and electronic signal pro- cannot differentiate between the posi- measurement of position and velocity of cessing extends the operation and ap- tive and negative going fields, the out - both linear (Fig. 6) and rotating move- plication of the devices. ments and the fact that the signal is proportional to field amplitude can Applications Coil again be useful in low -speed applica- The high sensitivity. spatial resolution drive tions. and frequency range of thin-film ferro- Coil magnetic magnetoresistive sensors Coin evaluation make them well suited for a wide range Magneto resistor Detection of a varying magnetic field of magnetic -field detection applica- due to eddy currents has been used in a tions. Because the characteristics and novel coin valuation system. The eddy form of the sensor can easily be mod- Coin currents are induced in a conducting ified using standard thin-film processing material passing through the field by a techniques, it is relatively simple and Y high -sensitivity nlagnetoresistive cost-effective to customize sensors for 11W sensor. specific applications. Microprocessor Figure 7 involves either a single mag- Any physical quantity which can be netoresistive sensor or an array of sen- transformed into a magnetic field is sors, depending upon the degree of measurable using magnetoresistive sen- discrimination required. In the time the sors. Accept coin takes to pass the sensor(s) the Traditionally, magnetoresistive sen- gate system performs a multitude of sors have been mainly employed as measurements (a scan) across the coin read-only heads for sensing magnetical- which effectively allows an electro- ly encoded information on tape, discs Fig. 7. Magnetoresistive sensor in a coin magnetic fingerprint of the coin to he and stripes. In particular, magnetoresis- valuation system. Sensor scans coin as it generated. This scan is a point -by -point tive read-only heads have been used to passes through to provide comparison of the phase difference be- read the information on magnetic discrimination between coins of similar tween the applied magnetic field and stripes on hank, transaction, credit and size. that due to the coin. This phase -shift scan is used to discriminate between differing coins. Permanent The scan generated is Direction of motion x magnet S independent of - the velocity and acceleration of the coin S \ passing the sensor within the normally Direction Magnetoresistive N x of expected range of operations, which I N( I I element motion I simplifies the design of the mechanical flight deck of the coin mechanism; signal processing is carried out using a microprocessor. Setting up can be car- Constant ried out on -site, if necessary, and re - current is source calibration also possible during (a) (bl routine maintenance. Id ax h1 ox Discrimination achieved with this sys- v(t) of dx t=time It) of dx tem is excellent. Examples of the signal dt dt scans for a standard British coin them- Fig. 6. Methods of detecting position (a) and velocity (h) ofa magnet in linear selves and the closest false coin are seen movement. in Fig. 8.

1(112 ELECTRONICS WORLD + WIRELESS WORLD October 1989 TELECOMMS Towards the passive all -optical ne :: ork

Costs of installation and interfacing have limited the use of optical fibre to long-distance networks. But progress has lowered costs and fibre now looks very attractive

pplications for Thus each system can sup- local optical fibre port up to 128 customers. cabling include Light transmission is dup- telephone service lex at 1300nm. Data trans- and cable tele- mission on TPON uses a vision, in both narrowband total bit rate of 20Mbit/s and and broadband configura- in the exchange-to -customer tions. Experiments already direction employs time - conducted show that this division multiplexing (TDM) technology is entirely feas- in blocks of 8kbit/s to allow ible and only the lack of services of, say, 56, 64, 144 standards, uncertain market or 384 kbit/s. Return trans- demand and an unclear reg- mission uses time -division ulatory situation are holding multiple access (TDMA); back its introduction. the head -end control system An obvious route to take delays transmit pulses from is to substitute optical fibre customers so that they arrive for the metallic cables cur- at the exchange perfectly rently used and combine this . interleaved with other with digital loop carrier transmissions. n (DLC). y: the end a "iX1`t At customer's For larger users (25 lines network terminator converts or more) another mature `' N ,t`=K°¿y9. the digital bit streams into is available: Flex- `r t .. technology the appropriate format using ible Access System or FAS, ,« ., ;,' ' 771Z . one or more interface adapt- which is already being in- A o .it '&4'a,-11th4 / i ers. For example, a tele- widely by British . stalled I' Y phony interface adapter Telecom in London and d translates the bit -stream has the abil- the road for copper wiring? British Telecom elsewhere. FAS The end of back to analogue speech, normal TPON telephony over passive optical netorks ity to deliver both considers that - detects signalling and pro- service and leased small business customers by the 1990s. telephone will be cost-effective for vides ringing current. channels. It lines in 2Mbit/s The transfer to TPON and is cabled as a separate overlay network, using a 96 fibre cable on and its unique feature is that it is indeed EPON will inevitably be gradual. re- the main line. Subsidiary cables with 48 passive: no active devices are used be- gardless of the obvious advantages they or 24 fibres are split at joint points and tween the central exchange and the offer over the existing copper cable - led to customers' sites. subscriber's termination. Intermediate based local networks. British Telecom Both the former schemes, though distribution points contain no electro- considers that TPON will he cost- admirable, are not really tailored to the nics. The system also uses a single rather effective for small business customers economics of serving small users, nor than multi -fibre cable between the ex- with, say. five lines by the early 1990s. are they ideal for distributing wideband change and distribution points. Under while research continues to develop services such as cable television. For the current scheme a single optical fibre further improvements. these applications a radically new solu- leaves the exchange and is taken to a tion has been devised by British Tele- cabinet at an intermediate point; here a com Research Laboratories, arguably a passive optical splitter feeds up to eight world -leader in this field. fibres. Each fibre then goes to a dis- The name of this is TPON or Tele- tribution point where another splitter phony over a Passive Optical Network, serves cables to up to 16 customers.

October 1989 ELE('TRONICS WORLD + WIRELESS WORLD 1013 THE ORIGINAL SURPLUS WONDERLAND! THIS MONTH'S.SPECIAL! FLOPPY DISK DRIVES SPECIAL EXPERIMENTERS PSU's Very high resolution, fully cased 14' green or amber screen - BARGAINS GALORE ! These 2 PSUs are built to BT'S rigorous specs and give fully monitor with non -glare screen and swivel/tilt base. The very protected DC outputs ideal for the electronic hobbyist & ex- latest technology at the very lowest price) Fully NEW 51/4 Inch from £29.951 compatible and perimenter. Type EPSU1 Input is 240v AC; outputs are 5v @ plug compatible with all IBM PCs and clones fitted with a high Massive purchases of standard 51/4' drives enables us to 2a.112v @ 1 a, 24v @ la, 5v fully floating 50ma. EPSU2 input res Hercules or equivalent card) Enables superb graphics and present prime product at Industry beating low prices' All units Is 30-70vdc outputs are 5v @ 6a,12v @ la, -12v @ 0.5a & 5 resolution, all at a give away price. Has many extra features (unless stated) are removed from often brand new equipment and others. Circuit diagram on request for EPSU1. No data with including aux+58 12v DC outputs to power at least 2 disk drives, are fully tesled,aligned and shipped to you with a 90 day EPSU2 - hence the price' Both at parts alone price) it your PC power supply Is getting hell Supplied BRAND NEW guarantee and operate from +5 & +12vdc, are of standard size and EPSU1 £16.95 and boxed. State whether amber or green accept the standard 34 way connector. lc) EPSU2 £9.95 IC) screen required. SHUGART Amber £79 Green £69 (El SA405. BRAND NEW í19.95(B) TANDON TM100-2A IBM compatible DS £39.95(B) BARGAIN' PARTS & BOARDS PACKS COMPUTER' SYSTEMS TANDON TM101-4 80 Track DS £49.95(B Its stock taking time once more so we have made up a lot of our CANON,TEC etc.DS hall height.State 40 or 80T £75.0003) famous bargain parcels agalnl These parcels represent the best TATUNG PC2000. Big brother of the famous Einstein. The TEAC FD -55-F.40-80 DS half height. BRAND NEW £99.00(B) value for money available and the greatest bargains of the TPC2000 Professional 3 piece system comprises: Quality high 31/2 INCH BRAND NEW AT £19.9511 century - a real thrill to open them up when you find that you resolution Green t2' monitor. Sculptured 92 key keyboard and Never before seen price for a 3W drive. Standard size believed have bought equipment and components (mostly brand new) plinth unit containing 280A CPU and all control circuits. PLUS 2 to be by Canon. Brand new and packaged - mint condition' 40 for well under a third of our normal low pncelll Integral TEAC 5.25 80 track double sided disk drives. Generous track SS, run from +5 & +12vdc with standard power Mix of general electronic parts & other features include dual 8' IBM format disk drive support. connec- equipment: for Only £19.95 or 2 for £34.50(B) Sklos weight for.... Serial and parallel outputs, lull expansion port, 64K ram and £8.95(B) 20 kbs weight for ....4'72 SO(D) ready to run software. Supplied complete with CP/M, Wordstar CHOOSE YOUR 8 INCHI Boards Parcels for parts recovery: and Basic. Brand new and covered Shugart 800!801 SS refurbished & tested £125.00( Parcels contain almost any type of boards Including ICs, by our famous 90 day Shugart guarantee and backup. Normal price of this unit Is over £14001 851 double sided refurbished & tested £195.001 memory, logic, passives and vast assortments of partsl Mltsubl rhl 1,42994-63 double Our price .... only £299 (E) sided sw tchable 10 board parcel....£7.50(B) 20 board percel....£13.95(C) hard or soft sectors- BRAND NEW £250.00(E) PC -AT 286 CLONE Lowest ever priced 8 mhz PC -AT clone POWER complete with a 20mhz hard drive, a 5.25' 360k floppy, 640k of SPECIAL OFFERS!! SUPPLIES Dual 8" with RAM plus Hercules card compatability. The keyboard is NCR drives 2 megabyte capacity housed in a smart case All PSUs 220-240vac input and are BRAND NEW unless with built In power supply' stated. with 85 keys In an attractive beige, grey and cream finish to Only£499.00 F Many types ranging from 3v to 10kv always In stock. Ideal as exterior drives) ( ) match the computer. The monitor Is very high resolution 14' Byte BD301 5vdc @ 1.6a. 12vdc @ 1.5a.Pertect for disk drives; End of line purchase scoop) Brand new NEC 02246 85 with non -glare, with your choice of amber or green screen. A very 8' Molex sockets.Very attractvely cased.11lum. sw. £19.50(B) megabyte of hard disk storagel Full CPU control and nice package at a super price' Industry Greendaie 19ABOE 60 watts switch mode.+5v @ 6a.±12v @ standard SMD Interface. Ultra hi speed transfer and access time 1a,t15v@ I a. AFE and fully tested. 11 Our price .... only ...... £799 (E) leaves the good old ST506 x20x5.5cros. £24.95(C) Interface standing. In mint condition Conver 130 and with AC130. watt hi -grade VDE spec.Switch mode.+Sv comes complete manual. Only £399(E) @ 15a. SPECIAL PURCHASE -5v @ 1 a,312v @ 6a.27 x 12.5 a 6.5cros MAINS,SUPPRESSORS & FILTERS £49.95(C) V22 1200 baud modems Boshert 13090. Switch mode.ldeal for The "Man" from Crotan is a British made high current mains drives & system. +5v@ 6a, +12v @ 2.5a, -12v We got a tremendous buy on further spike suppressor and RF filter In one, capable @ 0.5a, -5v @ 0.5a. stocks of this popular of handling up £29.95(B) Master Systems 2/12 microprocessor controlled V22 full duplex to 10 amps' The attractive case has an Integral 13 amp socket 1200 baud modem - we can now bring them to you at half last for your equipment plug and a flying lead terminates Ina quality .IBM KEYBOARD DEAL advertised price! Fully BT approved unit, provides standard plug (to BS 1363A standard) to go to the mains socket. There V22 high speed data A replacement or backup Comm, which at 120 cps can save your Is an Internal fuse plus one In the plug. Two LED indicators, one keyboard, switchable for IBM PC, phone bill and connect lime by a staggering 751/4I Ultra slim 45 PC -XT or PC -AT. LED's for Caps,Scroll & Num for power on and the other lights if the internal fuse falls. Di ms:6' Locks. Standard mm high. Full featured with LED status Indicators and remote 85 keyboard layout. Made by NCR for the English 8 markets. x 3' x 2'. Brand new. Normal distributor's price is £65.001 US error diagnostics. Sync or Async use; speech or data switching; Absolutely standard. Brand new & boxed with manual and key Our price only £15.95 each or 2 built in 240v mains supply and 2 wire connection to BT. Units for £29.95 (B) template for user slogans on the function keys. Attractive Belling -Lee type L2127 mains RFI filters rated at are In used but good condition. Fully tested prior despatch, with 250 volts 3 beige,grey and cream finish, with the usual retractable legs amps maximum. Comes a data and a lull 90 day guarantee. What more can you ask for complete with built in mains cable underneath. A generous length of curly cord, terminating in the and at this price!' ONLY £69 (D) (English coding), and a three pin miniature non -reversible sock- standard 5 pin DIN plug. A beautiful clean piece of manufac- et and a mating plug, to go to the equipment. Ideal for those turers surplus. What a deal) Write to us today and get your name on our mailing who are bugged by RF Interlerence. Very compact. Dims 3.118' BRAND NEW AND BOXED ONLY £49 (B) Ilst for our FREE eight weekly bargain flyer 716 Diliuy x2.5'x1.5' £3.95 each or3 for £10(A) 546 ss with thousands of unadvertised special offers. COOLING FANS THE AMAZING TELEBOX! MONITORS Please specify 110 or 240 volts for AC fans. Converts your colour monitor into a QUALITY COLOUR MONITORS 3 Inch AC. 112" thidk £ 8.50(0 COLOUR TVII Decca 16" 80 series budget range colour monitors. Features 312 Inch AC ETRI slimline.Oniy 1' thick. £ 9.95(B) TV SOUND Include PIL tube, an attractive teak style 4 inch AC 110/240v 112' thick. £10.95(B) case and guaranteed rel.reóx z & VIDEO 80 column resolution, features which are only normally seen on 4 inch AC 112' thick £ 9.95(B colour monitors costing 3 times our price) It is absolutely ready 10 Inch Round.312 thick. Rotron 110v £10.95(B It. TUNER! 62 mm DC 1' to connect to a host of computer or video outputs. Manufacturers thick. No.812 for 6/12v.814 24v £15.95(A Brand new high quality, fully cased, 7 channel UHF PAL TV tuner 92 mm DC fully tested surplus, sold In little or hardly used condition with 90 12v. 19 mm thick. £10.95(A system. Unit simply connects to your TV aerial socket and colour 4 inch day full RTB guarantee. Decca 80 RGB TTL and sync Input for DC 12v. 12w 112' thick £1250(B) video monitor turning same Into a fabulous colour TV. Dont worry 4 Inch DC 8w. BBC and similar type interlace etc.Decca 80 COMPO 75 ohm 24v 1- thick. £14.50(B) if your monitor does nt have sound, the TELEBOX even has an composite video Input with Integral audio amp & speaker. Ideal integral audio amp for driving a speaker plus an auxiliary output for use with video recorder or our Telebox ST or any other audio RECHARGEABLE BATTERIES for Headphones or HI Fl system etc. Many other features: LED visual use. Any type only £g9.00 (E) LEAD ACID Status Indicator, Smart moulded case, Mains powered, Built to HI -DEFINITION COLOUR MONITORS Maintenance free sealed long lice. Type A300. BS safety specs. Many other uses for TV sound or video etc. Brand new Centronic 14' monitor for IBM PC and compatibles 12 volts 12 volts 3 amp/hours 3. 9514.1 Supplied BRAND NEW with full 1 year guarantee. at a lower than ever pricel Completely CGA equivalent. Hi -res 6 volts 6 volts3 amp/hours £ 9.95(4.) Telebox ST for composite video input monitors ...... £29.95(B) Mitsubushi 0.42 dot pitch giving 669 x 507 pixels. Big 28 Mhz 6-0-6 volts Centre tapped 1.8 amp hours £ 5.95(A) Telebox STL as ST but with Integral speaker £34.95(0) bandwidth. A super monitor in attractive style moulded case.Full 12 volts 12 volts 24 amp hours. A200. RFE. E29.0003) Telebox RGB for analogue RGB monitors £59.95(B) 90 day guarantee. Only £149 (E) SPECIAL OFFER! NOT suitable for IBM or Clone type colour monitors. 20",22" and 26" AV SPECIALS 100 amp/hours at 6 volt! Brand new Chloride Powersafe Superbly made UK manufacture. PIL all solid state colour 3VB11. Leakproof with additional snap -on security lid. Perfect 'BRAND NEW PRINTERS monitors. complete with composite video & Inputs. sound Attrac- for uninterruptable power supplies, portable power source, Epson MX -80 F/T One of the most popular printers around' tive teak style case. Perfect for Schools,Shops,Disco, Clubs. caravans etc. Normally costs £801 £39 (E) Bi-directional printing with full logic seeking. 9 x 9 dot matrix for In EXCELLENT little used condition with full day guarantee. 90 NICKEL CADMIUM e nl a rged,bold,co nde nsed etc. Standard parallel interface. Brand 20"....£155 22"....£170 26"....£185 (F) Quslity 12v 4ah cell pack. Originally made for the Technicololor label removed from front. Handles tractor,lanfold and Individual MONOCHROME MONITORS video company. Contains 10 GE top quality D nicad cells in a paper. OK with IBM PC and most others. A tremendous buy) smart robust case with a DC Wang green screen 12' chassis monitor with composite video output connector. Ideal for portable £129.00 (E) equipment. Brandnew. Hazeltine Esprint small Input. Adjustable for tilt. Requires 12 vdc. Brand new and boxed £19.95(B) desklop.100 cps with RS232 and Ex -equipment NICAD cells by GE. Removed standard parallel. Full pin addressable 6 in perlect condition. Only £39 each or 2 for £75 (F) from equipment and user selectable and in good, used condition: D size 4 fonts. Up to 9.5' paper. Sheet & tractor feed. Motorola M1000-100 5' black & white compact chassis measur- 4ah for £5(B) £149.00(E) F size 6 Centronics 150 series. Always known for ing only 11.611 x 12W x 22D. Ideal for CCTV or computer 7ah for £8(B their rellabilty In continuous use - real workhorses In any applications. Accepts standard composite or Individual H & V environment. Fast 150 cps SPECIAL INTEREST with 4 fonts and choice of syncs. Needs 12vdc at only 0.8a. Some units may have minor Interfaces. screen Racal-Redac real time colour drafting PCB layout system. In- 150-514 up to 9.5' paper £155.00IE) blemishes. Fully tested with 30 day guarantee and full cludes 150 data. furniture and huge monitor.Complete ready to gol £3950 -SW up to 14.5' paper £199.00(E) í19.00(C) DEC VAX11/750Inc. 2 Meg Ram DZ and full Fully cased as above In attractive moulded desk standing documentation, In Specify whether serial parallel brand new condition' £3900 or required. swivel. Dim 12 x 14.5 x 26cm. £39.00(C) Large Calcomp plotter £ 650 CALL FOR THE MANY OTHERS IN STOCK JVC 751 ultra compact chassis monitor for 12vdc 0.7a. Dim 111 Tektronix RM529 Waveform Monitor £ 300 a 14 x 18cm. Simple DIY data Included to INCLUDING DAISY WHEELS. convert to composite 1.5kw115v 60hz power source. video input .Full data. BRAND NEW £65.00(B) £ 950 Wayne Kerr RA200 audio real time freq.res.anaiyser. £3000 Visit our Shop - Technical help always on hand 20" Black & white monitors by Aztek, Cotron & National. All VG Electronics 1033 Teletext Bridge £3750 plus many un -advertised solid state, fully cased monitors ideal for all o1 specials. You can buy a types AV or CCTV Tektronlcs R140 NTSC TV test signal standard. applications. Standard £ 875 colour television for as little as £291 Come composite video inputs with integral Vereatek V80 Printer plotter and audio amp and speaker. In good £1500 Sold used condition - fully tested DECLS11/02 CPU board Join the gang at 215 Whitehorse Lane? with 90 day guarantee. £85.00(F) £ 150 LARGE CIWINTITES OF OSCILLOSCOPES AND TEST GEAR ALWAYS AWAILABLE - CALL NOW! MAIL ORDER 8 OFFICES LONDON SHOP bISTEL ID The Original AL ENQUIRIES i~ "4' iN Open Mon -Fri 9.00-5.30 100's of pargainsi Firs dial -up sil ... Dept W. 32 BlggIn Way, Open Mon -Sat 9-5.30 1000's of items+lnfo On Llne Át. ? . : : 01-679-4414 T Upper Norwood, 215 Whitehorse Lane, 300 bd 01.679-1888, =MI « South Norwood, 1200/75 bbl 01-679-6183, Fax- 01-679-1927 ...':. London SE19 3XF. Visa London, SE25 6RB. 1200/1200 bd 01-679-8760 Telex- 894502 I

l prices for UK Mainland. UK customers ADD 15% VAT to total order amount Minimum ostler £10 PD orders from Gwemment,Uniaersrbes,Schools & Local Aut o ties eorn>minimumk account order C25. Carnage charges (A)..£1.50. (Bl C3.50. (C) -Electronics= -C6.50. (DI.So. (E)-(12.50 IF).£15. (G).Cali . NI goods supplied subject to our standardst Conditions of Sale and uriess adherenceen dated guaranteed for 90 days. AlI g,n rantees given on a return to base basis We reservereser see nigh to change prices 8 cations without prior notice. Orders accepted subject to dockOuotations w.thngry given tor higher quantities than dose stated. CIRCLE NO. 22 ON REPLY CARD PIONEERS

Thévenin's theorem is known engineering department at the École made a very careful study of Kirchoff's and used throughout the Supérieure. This was the start of his Laws and discovered the rule which he world, But as is usual with teaching career and his introduction to then expressed in his theorem, having such things, little thought is the work that led to his famous proved it by a clever application of the now given to the man whose theorem. already established Superposition name it hears. He has been described as He developed an interest in electri- Principle. a humble man and a model engineer and cal measurement and, with his former Thévenin's Theorem was published employee. He was hard working, held teacher Jules Raynaud, he translated a in three separate scientific journals in strict principles, was scrupulously moral British work on units and physical 1883 :n a paper entitled "Extension of and kind at heart'. That alone would constants into French. Translation of Ohm's Law to complex electrical was a make a wonderful epitaph. such foreign publications was part of circuits'. It introduced as ''new He is remembered today almost en- the routine work of the School. In theorem of dynamic electricity" and gave a simple method of calculating the tirely for one small piece of work. I Iis conjunction with this work, Thévenin theorem, published in 1883, was based current that would flow in a new con- on his study of Kirchoff's Laws and is ductor when it was added to an existing found in every basic textbook on network. Nowadays it is expressed electrical circuits. It has made rather differently (in terms of an his name familiar to every stu- equivalent circuit consisting of a a resis- dent of electrical circuits and to voltage source and series It every electrical and electronics t3r) but it is the same theorem. engineer. was Thévenin's first article and appeared in the same year Léon Charles Thévenin was t of the joint horn at Neaux just outside as the publication Paris on March 30, 1857. He translation with Raynaud. graduated from the École Three further articles follow- year. first gave a Polytechnique in 1876 and two ed in that The a galvanometer years later joined the Corps of method of using Telegraph Engineers, later the to measure potential, and made new theorem to French PTT, as one of the use of the second intake to the newly - achieve its ends. The second reopened École Supérieure de da)described a method for measur- the third was Télégraphie. The public tele- ing resistance; and graph service was to be his on the use of the Wheatstone working life until his retire- Bridge.' ment in 1914 on the eve of the first World War. During those A good launch 4 les' 36 years he showed himself to Publication of the theorem in be a great engineer. an excellent tt ree journals gave it a good launch, administrator and, perhaps first but Thévenin also taught it himself and foremost. a reacher. He con- ir his courses to telegraph engineers tinued some of his teaching duties . . France. By 1889, a century ago, to the end of his life. ,. .S others were already writing the start of his career, Thévenin of it as the "théoréme de At t .." joined the department responsible for Thévenin". It is an early long-distance underground tele- example of practical engin- ao a r graph lines which was then vastly r, 4 eering theory. in this case expanding its service and requiring telegraph theory, being ori- most of the newly trained young ginated by an engineer and engineers leaving the École taught by an engineering Supérieure=. But he did not ~r school quite outside the stay there long. His unusual scientific tradition of math- talents were recognized and ematical physics. he moved to the Department All was not, however. of Materials and Construc- without problems. Thévenin tion which had started to reported his discovery to the tackle the problems involved French Academy of Sciences in the construction of power but first he disclosed it to lines. His standardization of another French telegraph en- the rules for the erection of PIONEERS gineer whom he deeply overhead power lines stayed admired. A. Vaschy. Vaschy in force for many years. found the concept attractive Léon Charles Thévenin (1857-1926): but thought the theorem was Teaching engineer, teacher and administrator wrong. Others were con- grew In 1882 Thévenin was asked sulted and controversy it was right or to take on the job of teaching as to whether the young inspectors of the W. A. Atherton wrong.

1015 October 1989 ELECTRON ICS WORLD + WIRELESS WORLD PIONEERS

Though Thévenin produced a rush of EDWARD LAWRY NORTON publications in 1883, he seems to have published nothing thereafter. Yet his career continued to advance and his teaching skills were sought outside the Norton's theorem complements Thévenin's the same year, Columbia University awarded by presenting an equivalent circuit consist- him a Master's degree. Norton then spent the PTT. In 1885 he was asked to teach a ing of a current source and parallel resist- rest of his working life with Bell Labs. Even course in industrial tools. and later one ance instead of Thévenin's voltage source after his retirement in 1963 he continued to on industrial electrical engineering, at a and series resistance. It was published in work as a part-time consultant school of commerce. The Institut 1926. His areas of work ranged wide, starting National Agronomique employed him with network theory and moving into mecha- from 1891 to teach mechanics. and later Edward L Norton was born on July 29, nical and acoustic networks, relay theory. 1898, at Rockland, Maine, and it was there anti-aircraft directors and bomb sights (dur- to lead seminars in applied mathema- that he went to high school. He served in the ing World War 2), guided missiles (he was a tics. Ile continued all of these teaching US Navy during World War I. After starting at patent holder for the Nike missile guidance appointments until his death in 1926. the University of Maine he gained a B.S. system), automation, data processing and Ile had already proved himself as degree from MIT in 1922 and then joined high-speed data transmission. In all he held head of the Bureau des Ligues (where Western Electric. When the company's re- about 20 patents. He died, aged 84, at he improved and unified the construc- search laboratories merged in 1925 with Chatham, New Jersey, on January 28, 1983, tion of lines and pesonally supervised those of AT&T to become the Bell Telephone leaving a widow, Blanche, and a son, John. Laboratories, Norton joined the new labs. In the implementation of his policies) when in 1896 he was appointed director of the telegraph engineering school. It was a job which brought him immense satisfaction. I laving no ambition to rise further he had almost to be prised out of that 1926 - the year Thévenin died. How- position in 1901 to take over as ever, both theorems. it is said, had been Corrections: Konrad Zuse engineer -in -chief of the workshops, a anticipated by the German physicist Dr Konrad Zuse has provided some position he held with distinction until Helmholtz in 1853. corrections to the July article about his retirement in January 1914. Thévenin remained a bachelor for his invention of the first successful life, but provided a home for his computer. He was born not on July A crucial theorem mother's widowed cousin and her two 10, 1910 but on July 22; the Z1 children. Later he adopted the children. computer's memory was to hold 64 His theorem is now a fundamental part His favourite recreation was of the theory of electrical engineering angling binary numbers of 24 bits, not 16 and he owned a boat which he used bits; and, very the was and was crucial in developing transmis- on important, Z3 the River Marne for fishing. in 1941 the Z4 begun sion network theory. It was to prove of Ilis stu- completed and dents at the Institut Agronomiyue in 1942. immense practical value to engineers. It nick- named him The Admiral. Ile was also a is now usually taught alongside its complementary theorem, Norton's talented violinist but played only in private. this Theorem (see panel), which dates from Dr Atherton's previous subjects Late in 1926, Thévenin was taken to year have included the following: Paris for medical treatment and it was THEVENIN'S THEOREM there that he died on September 21. A Hidetsugu Yagi and the Yagi-Uda kindly man of simple tastes, Thévenin antenna (January, 90). had requested that Below is a translation' of Thévenin's only his family Harold S. Black, inventor of the theorem, as originally stated ín Annales should attend the cemetery and that a negative -feedback amplifier (February, télégraphiques: single rose from his garden should 194). Assuming any system of linear conductors adorn his coffin. So it was when he was Harry Nyquist and Hendrik Bode and connected in such a manner that to the buried in his home town of Meaux. their epic work on the stability of feed- extremities of each one of them there is back amplifiers (March, 220). connected at least one other, a system Russell and Sigurd Varian, creators of having some electromotive forces, E,, the klystron (April, 4I7). E2... E3, no matter how distributed, we con- C.F. Gauss and W.F. Weber, and their sider two points A and A' belonging to the exceptional scientific partnership (May, system and having actually the potentials V References and V'. If the A A' 521). points and are connected 1. C. Suchet, Electrical Engineering, vol.68, by a wire ABA', which has a resistance r, with 843-844,1949. Alan Turing, the solitary genius who no electromotive forces, the potentials of wanted a 2. I I. Thomas. Annales des Postes, Télég- to build brain (June 582). points A and A' assume different values of V raphesetTéléplrones, 11190-1098, 1925. Konrad Zuse (July, 732: see note and V', but the current i flowing through this 3. Comptes rendus, vol.97. 159-161: Journal above). wire is given by the equation de Physique, Vo1.2, 418-419: and Annales Sir Charles Bright, who spanned the V-V' i = télégraphiques, vol.3. 111: all 1883. Atlantic with a telegraph cable (August, r+R 4. A.J. Hutrica, Ph.D. thesis, Iowa State 810). University, 1986. Joseph Henry, actor turned engineer in which R represents the resistance of the and scientist (September. 906). original system, this resistance being mea- The author is indebted to A.J. l3uirica of A A', which sured between the points and are the University of Pennsylvania and P. Next in this series of pioneers of electric- considered to be electrodes. carré of France Telecom for the in- ity and electronics will be Lee de Forest, formation on which this article is based. irrve,tlorof the triode valve.

1016 ELECTRONICS WORLD + WIRELESS WORLD October 1989 AN UNBEATABLE COMBINATION

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1018 ELECTRONICS WORLD + WIRELESS WORLD October 1989 ANALOGUE ACTION

OP -AMP RUN-DOWN What's so good about c-mos op -amps?

Most integrated circuits today are c- mos. You wouldn't believe this to be so if you looked only in the analogue manufacturers' data and application books: BJTs seem to be far more popular than c-mos devices for a variety of different but very valid reasons. But, if low input bias current and a high, almost infinite, input impedance are important in your application, then diagram of Linear take a look at the c-mos op -amps such as Fig. 1. Simplified block Battery -power the OP -80 from PMI. Data sheets of Technology's L TC1052 chopper -stabilized these c-mos op -amps show extremely op -amp. instrumentation low input bias currents at 25°C, typically Switches SI and S2 are toggled in amplifier in the 10fA range, which for almost any phase at 330Hz by an internal oscillator application would seem to be virtually (not shown) and the circuit alternates Another new offering from Linear zero. But, what you might look at between auto -zeroing and sampling Technology is a so-called micropower closely is how this figure increases with states. Capacitors Ce and Cb together instrumentation amplifier, the LT1101, rising temperature; for example, the with S2 form a sample -and -hold func- which draws 751.1.A supply current. It is OP -80 has a quoted maximum input tion. With both switches down, the based on the structure shown in Fig. 2, bias current at 25°C of 60fA and this input is shorted to ground and Ca in which all the resistors are on -chip and rises to a maximum of 20pA at 125°C, charges to the output offset at RL2. the gain is set at either 10 or 100 simply almost three orders of magnitude in a Output of the amplifier is directly pro- by pin selection. The features one 100°C temperature rise. Quite an in- portional to the voltage across Cb, this would expect from a high quality instru- crease, but still a very respectable input being the voltage acquired by Cb at the mentation amplifier are all there. bias current for 125°C. One version of end of the previous sampling switch .However, as you would anticipate from Murphy's Law states that high speed state. When both switches are up, the a micropower device, the' frequency performance is incompatible with high input is connected to the first transcon- performance is not high: gain - impedance and the OP -80 does not ductance gain stage. The DC offset bandwidth product is around 250k Hz. disprove this, with a gain -bandwidth voltage stored across C3 during the But the particularly interesting feature product of around 300kHz and slew - auto -zeroing state is fed back to cancel of this device is that it can be run on a rate of some 0.4V/µs. Mos op -amps the output offset voltage, reducing it very low DC voltage supply, as low as have a reputation of poor input offset almost to zero. Not shown ín the figure 1.8V, without loss of gain accuracy. voltage, and whilst they cannot get close is the additional circuitry needed to This feature is of real value to the to the best bipolar op -amps, the figures provide a feed -forward path at high designer of battery powered portable are quite reasonable at around frequencies and to correct for anti- instrumentation, which is one of the key ±0.5mV. aliasing errors introduced during the .areas for micropower devices. sampling process. Generally the two capacitors áre external to the chip, but -stabilized intro- Ground Output Chopper Linear Technology has recently (ref) duced a new device, the LTC1050, in amplifiers capaci- which the two sample -and -hold Ref Out To achieve the best performance in DC tors are integrated on to the chip, giving G=10 G=10 offset and drift, you cannot beat the the device excellent performance whilst -stabilized amplifier design, reducing the external component count. chopper +In sometimes referred to as an auto The device features typical offset volt- -In C- zeroing amplifier. Figure I shows a age of ±0.5µV, drift of 0.011V/°C, DC voltage of 1.61V simplified diagram of a typical chopper to 10Hz input noise v- V+ stabilized amplifier, the LTC1052 from peak -peak, slew -rate of 4V/µs and gain - Linear Technology Corporation of Mil- bandwidth product of 2.5MHz Priced R=92k pitas, California. Excellent overall DC at around £2.11 per piece (25 -up), the instrumentation features are achievable without the device is certainly very good value if Fig. 2. This micropower runs on supplies as low as 1.8V need for high -quality DC performance your application requires excellent DC amplifier (Linear Technology). in any of the gain stages of the amplifier. characteristics.

1019 October 1989 LLL("1'I2ONICS \\'ORI I) t- \\ I ItLITSS WORLD ANALOGUE ACTION

New topology op -amp Bob Widlar, father of the ubiquitous current mirror. has recently published his latest work', co -written with Mineo Yamatake, on the development of a new fast settling op -amp with low supply current. The design is quite novel and will give its manufacturer, National Semiconductor, a firm lead in what could well he a new generation of op -amps. The new configuration is based on a fully complementary BJT structure. It promises the precision of the best bipolar op -amps without the usual slew -rate restrictions. In some ways the design is Fig.4. Outputs of this active loudspeaker crossover circuit, when summed, produce an like the transimpedance amplifiers (see exact replica of the input signal (National Semiconductor). Analogue Action, Electronics & Wire- less World August 1989, 826-7) in that it differential inputs, which means that is capable of delivering high speed with the available output current from the Constant -voltage low quiescent current; but no degrada- input stage to drive the second gain loudspeaker tion of DC performance occurs in stage and the internal compensation achieving this goal. capacitor is not limited to the value of crossover The input stage of a conventional long -tail source. Loudspeaker crossover networks, both op -amp is a simple long -tail pair and it In the design of bipolar ICs it is active and passive, are will saturate for relatively small error common practice to make liberal use of still keenly de- bated in voltages between the two inputs emitter -followers to raise the effective the audio world, This active crossover (Fig.4) is one few (-60mV), severely limiting the current current gain. When a follower drives of that will allow output of a dual -loudspeaker sys- available to slew the internal compensa- the base of another transistor, strange tem to truly represent the input tion capacitor. Various techniques have things happen at frequencies signal - in theory at least. been employed to improve slew -rate, approaching the fr of the transistors'. When such as the use of emitter degeneration, Even a simple two -stage follower can added, high and low outputs of a constant -voltage but these techniques reduce the poten- exhibit high -frequency oscillation, crossover produce an -exact replica of the input signal, tial open loop gain and as a result DC especially with capacitive loads. Com- unlike most gain accuracy is sacrificed. puter models are inaccurate close to fir conventional crossovers. In practice of course, voice A diagram of the input stage of the and cannot be used to predict perform- driver -coil align- ments and driver delays new op -amp is shown in Fig. 3. The ance and to date no consistent ex- come into play, that main difference between the new design perimental results have been obtained but applies to any crossover net- and the conventional long -tail pair input in attempt to explain these high fre- work. The main drawback of this un- doubtedly neat is stage is that the constant current source quency oscillation phenomena. little circuit that it has a roll -off of only 12dB/octave. has been replaced by a new circuit which To steer round the problem, the Apart from the op -amp functions as a constant current source manufactured device, the LM6218 (the type, this for low differential input signal levels. LM6118 military specification device is crossover circuit from the LM6118/6218 data sheet is identical Buffers Tr7 and Trs increase the output due to be released in November) has to one in National 1986 current drive capability for higher leve been designed with fewer emitter - Semiconductor's applications followers than other precision designs. handbook. In the data sheet, there is no Large signal test results for the reference back to the original applica- LM6218 show the effectiveness of the tion note and no information on the new slew -boost technique, with a very revised circuit's operation or advan- clean response and no evidence of any tages. oscillatory tendencies especially for the In the original circuit, the LM833 inverter configuration. Closed -loop low -noise dual op -amp was used. It has voltage -follower slew -rate is 70V/0, a 15MHz gain -bandwidth product, whereas the unity voltage gain inverter 0.002% distortion and 7V/µs slew rate. 6118 a is 140V/µs. The settling -time (0.01%) is The has 17M Hz gain bandwidth 400ns for an output voltage change of product, 140V/µs slew rate and a simi- 10V. The price for 100 -up quantities of larly low distortion figure. Its input the LIv16218 is in the region of £3.50 to noise figure seems higher (its noise is £4.00. not specified in the same way), but on the other hand it can output higher References currents. I. R. J. Widlar and M. Yamatake, 'A fast settling op -amp with low supply current', IEEE Fig. 3. Slew -boost input stage for National Journal of Solid State Circuits, Vol 24, No. 3, Analogue Action is written by John Lidgey Semiconductor's new LM6218 op -amp. .tune 1989.131)796-802. of Oxford Polytechnic.

1020 ELECTRONICS WORLD + WIRELESS WORLD October 1989 CIRCUIT IDEAS

Random -time *12V security light 1100k 10)J Unlike commercially available units, this night-time security light has a IC1 pseudo -random lighting up time. 16

During daylight, IC3 is clocked by 3 oscillator ICI,. When darkness falls, ABN 15 15 output of ICi;, goes low, stopping the A oscillator. Device IC3 stops with a ran- 13 dom count. 12 At the same time, the relay is acti- 4k7 vated, the 10 turning lamp on, and the AO reset signal to IC2 clears, allowing it to IC4 start counting. Four bits of this count A=B 100k BC212L are compared with four bits of the HC 85 random count, by IC4. When equal, and when output 012 of IC2 is high, the B3 ere BC184L equality output goes high. This output is 6 14 used to stop the oscillator, so that IC2 I' 7 11 stops counting, and is also used to turn the relay 9 104001 off. GND R 1 BO Nothing more happens until daylight, 8i 11i 121-7. 8 when the circuit resets. The count on IC2 will be, l J I xxxx 0000 0000 where xxxx is the random four -bit count on IC3, hence the lamp will be on for R1=180kf2, the lamp will be on for lamp does not fall on it. Adjust the 100016. toIF0011,counts. between 120 and 230 minutes. potentiometer so that the lamp switches The time for one count is approx- Ensure that the light sensitive detec- on at the desired darkness level. imately R1.C1 so, with Ct=IOµF and tor is positioned so that light from the D. Stewart, Aberdeen

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VR IC2 Transistor tester cum hFE meter in position six, close the switch; if the We developed this inexpensive circuit and when Vice- Vhe bottom led lights (or extinguishes in the for checking transistors and measuring IhFE= Rh/12c. hFE. case of a p -n -p device), the transistor is Resistances Re In all transistors, Rh and are varied until functional. In this second test, refer- the condition = is indicated by a ence voltage VR is slightly less than the < VCC VhC Vice(sat) I I Vile (sat) change of state in the top led. At this VC1 of a normal transistor with zero base Rh is divided Re and when VeC=Vhe, the hFE of a point, by to calculate current. transistor can be calculated from values hFE. The circuit is suitable for both silicon To test a transistor, set the switch to of resistances Rh and R. Assuming a and germanium transistors, and does transistor in its active region, position six from position one and look not suffer from errors associated with for a change in the state of the top led: if circuits that use diodes for Vhe com- V.= V11- ICRC the led does not change state, the tran- pensation. Vcc-IbhFNRc sistor is faulty. A. Karnal and K.C. Tripathi also, Just because the led changes state, it Bhabha Atomic Research Centre does not necessarily mean that the tran- Kashmir Vhe= Vcc- IhRb sistor is fully functional. With the switch India

October 1989 ELECI-RONI('S WORLD + WIRELESS WORLD 1021 CIRCUIT IDEAS

FSK The circuit uses three channels (Z,,, Z80 -compatible transmitter Z1, Z3,) of a Z80 counter/timer. All three channels are used in the counter Recently I needed an FSK transmitter non-standard channels could be used. mode; Z is the FSK output. To create that could be controlled by a Z80 sys- This transmitter allows full channel and the two frequencies required (f, + f2), tem. The requirement was total control shift control while requiring no setting channel Z is loaded under interrupt of channel frequency and shift so that up in terms of frequency. control with the two constants required to create the shift. Channel Z3 produces To system an interrupt signal at the required hit clock SV rate. When an interrupt occurs the 4K7 output channel is loaded with a constant relating to twice the output frequency MF4 required. This pulsed output is divided by to the Z2CK0 2CO -2 two obtain correct square wave output. HIi 2[2 Channel Z, controls the break fre- CK3 Control 8 quency (fb) of the MF4 low-pass filter, data bus Counter/ used to remove the unwanted harmo- timer nics from the divider. 121

To interrupt . control D.J. Virden Leeds -feedback and voltage feedback to define the With the component values shown Composite output impedance of the circuit. Pro- the amplifier has a gain of 13.6dB when amplifier vided that resistor R3 is small in com- terminated with a 60052 load and an parison with the design output impe- output impedance of 6009 to within 3i2 There are several methods of defining dance, virtually all the voltage de- up to 100kHz. the output of impedance of an ampli- veloped across the amplifier is available In practice, performance of the fier. In the simplest method, shown in at the output. I lowever with this con- amplifier corresponds well with the.pre- the first diagram, output source impe- figuration neit her side of the output is at dicted performance and our model dance is mainly defined by the series ground potential. This presents no showed no sign of instability when ter- resistor. The main objection to this problems if an output transformer is minated with various complex load im- simple circuit is that half the available used but it is not suitable where a direct pedances. Take care, however, to en- voltage swing of the amplifier is lost current output referred to ground is sure that resistors Rs, R7 and R4, R, are through the series output resistor when required. accurately matched. the circuit is correctly terminated. The third circuit is a modified form of Forward gain of the amplifier can be A well known circuit which overcom- the conventional composite feedback increased without significantly changing es this disadvantage, shown in the circuit which overcomes this disadvan- the output impedance by connecting a second diagram, uses composite current tage and allows one side of the output to resistance from the negative input of be grounded. IC, to ground. A value of 10k9 will Current sensing resistor R3 has been increase the gain by approximately Source moved to the amplifier side of the 0.7dB and a l kit resistor by 6dB. Resis- impedance voltage -feedback resistor chain and the tor R8 allows frequency response to be voltage developed across resistor R3 is limited by connecting a capacitor from sensed by the operational amplifier IC2. Output the output of IC, to its negative input load The voltage feedback component is also terminal. fed to the input of this amplifier and the o o resulting output used to provide nega- A.J. Chamberlain Output impedance defined by tive feedback to main amplifier IC,. address!) single resistor (no

Output load Output load

voltage Output impedance defined by composite Composite and current feedback with voltage and current feedback one side of output at ground potential

1022 ELECTRONICS WORLD + \VI RELESS WORLD October 1989 RF CONNECTIONS Minimum power radio telemetry In March 1966, RCA Review described way - results, he felt, substantially in the 1m transmitter output becomes an experimental project to develop a agreement with standard propagation equivalent to a conventional 6W trans- pocket HE transmitter suitable for such theory. mitter. This has been borne out in emergency applications as enabling an I was therefore interested to learn practice; we have a trial system operat- aircrew. ifter an emergency landing or from Ray Scrivens (Minisig Systems ing in Northumberland with several crash, to report their position by radio. Ltd, Unit 6E, Aberystwyth Science links operating over obstructed paths of The transmitter had an output of only Park, Cefn Llan, Aberystwyth, Dyfed 15 to 25 miles with simple dipole anten- I0(ImW and sent data at the very low SY23 3A11, (1970-625650) that his com- nas at the transmitters and a 3dB-gain speed of three hits per minute. To pany has been working for some time on vertical co -linear antenna at the re- achieve a high degree of frequency the development of very narrow band- ceiver. stability the crystal was specially cut for width radio data transmission with ex- "Of course, the data rate has to be a zero -temperature -coefficient turn- tremely low -power transmitters. Its first very low (one bit every seven seconds) over at 99°F (body temperature) system, for commercial telemetry ap- but there are many applications where mounted in a small enclosure held plications, operates in the de -regulated the parameters being measured can under the user's armpit to avoid the band 173.2 to I73.5MHz. Since the inherently change only slowly (e.g. power loss of a crystal oven. In addition, transmitter has an output power of only meteorological conditions, rivers/ because the bandwidth of the receiver I mW, and is approved to DTI specifica- reservoir levels etc.) or where some at base was only 0.75Hz, the transmitter tion MPTI328, it can be used over fairly long-term monitoring is required. frequency was arranged to sweep over a distances of 20-40km in normal terrain, With the availability of low -power mic- band of 2011z. During trials, using fre- not necessarily line -of-sight, without roprocessors, data can be pre-processed quencies between 13 and 16MHz. mess- the user's having to apply for a licence. at the remote site so that the amount of ages were received reliably over dis- Ray Scrivens writes: "The receiver data which needs to be transmitted is tances up to 200(1 miles. I do not think incorporates a digital signal processor decreasing, contrary to the present this equipment ever went into produc- which operates on the audio output of a trend in data communications where tion for either military or civilian ap- fairly conventional RF section. The everyone seems to think that it is neces- plications. although it may possibly DSP identifies the wanted signal, which sary to transmit at ever increasing rates! have done so for use in Vietnam. is processed through a filter with an "The technical difficulty with very The lower noise floor that can he used effective bandwidth of about I Hz. Be- narrow bandwidths is finding a techni- for VI IF receivers favours the use of cause of this, when compared with a que by which the receiver can identify even lower powers than 100mW. In conventional receiver with a 6kHz and lock on to the signal in a reasonably 1980. A.L. Mynett, ZS6BMS/G3HBW bandwidth, our system can operate with short time. In a normal receiver band- pointed out tome that he had found that input signals some 38dB weaker, so that width the incoming signal is well below l0mW output on 144M Iz can, without the noise level and, due to oscillator any very special techniques, be quite inaccuracies at both transmitter and easily received over clear, but not Some applications for telemetry at low receiver, its precise frequency is inde- necessarily optical, paths of up to 45km data rates using VHF transmitters of terminate. Digital signal processing has using only dipole antennas at each end. only 1mW output. Ranges of 20-40km provided us with an answer at quite low Signal strengths suggested that a range can be achieved in normal terrain: a line cost . of at least 70km could he covered in this of sight is not necessarily required. "Channel spacing with such a system

Meteorological station

Pipeline

Minisig'- receiver "7" Line modem/ y existing line Pu ing - telemetry -era twn station

Sewage works

\\ To private wire or es, public switched telephone net*ark

October 1959 ELECTRON WORLD+ WI RELESS WORLD 11123 RF CONNECTIONS

is determined almost solely by the frequency stability of the transmitter oscillator. At present we are able to operate 9 1k on five sub -channels, spaced at 2.5kHz l3 330 intervals, within each standard 12.5kHz channel. 290= E "The idea of the system originated in as i with amateur radio the desire to exploit 1 Negative loop open tropospheric scatter propagation using 2 closed 230 low -power transmitters. We were able Ug -2 V to communicate between mid -Wales Vc -10V and Sussex on the I44MHz band in 'flat' 170 conditions using a 5W transmitter and a 2 4 12 16 20 simple antenna. Admittedly it took ab- VOLTS (a) (b) out three minutes to send a three -digit number! With signals exhibiting the Experimental VHF voltage -controlled oscillator from Poland and (below) its considerable fading of tropo -scatter for performance. The design has switchable negative feedback. most of the time they were completely inaudible even through a narrow -band tors at higher power or at least higher mode, thus reducing the level of the CW filter. Error correction coding was stored energy (PO') but such an higher harmonic components. used to ensure that the odd missed bits approach is eventually limited by Their experimental VHF octave - would not corrupt the whole message. physical breakdown of the components. range VCO is shown in the diagram. Preliminary calculations indicate that it He suggests that probably the only Output variations in an octave frequen- should be possible to operate moon - parameter of oscillators which remains cy range did not exceed ±0.3óB, with bounce (Earth -Moon -Earth) using the to be fully explored lies in low - the second harmonic -55dB. With the system with reasonable transmitter temperature operation. Cryogenic negative feedback loop open the output powers and antennas. All we need now temperatures would not only reduce the power level varied by ±2.5dB over the is the time to do it! amount of noise produced in a given tuning range while the second harmonic According to the Minisig brochure. resistor but would also generally reduce was about -35dB. transmitter power consumption of their the value of the resistor. However, first system is very low (an important although he believes that low - consideration for remote sites). In a temperature operation remains an in- Radio physics and typical reservoir -monitoring applica- teresting area to be explored, he con- Auroral Oval tion, transmitting the water level every cludes. "It is highly probable that furth- hour, the mean current drain is about er physical barriers and limitations will The sixth National Radio Science Col- 6mA from 12V battery. With the addi- prevent the perfect oscillator from ever loquium (NRSC6), organized by the tion of a small solar panel and charging being achieved". soon -to -be -disbanded British National regulator, the transmitter could easily Also at the IEE frequency control Committee for Radio Science (URSI) he made self-sustaining. The receiver and synthesis conference, E. Efstath- and held this year at Southampton Uni- can separately identify and recover data ious and Z. Odrzygozdz (Warsaw Uni- versity, reflected the tightened purse from up to 33 transmitters operating in versity of Technology, Polish Academy strings of British radio -physics research. time -multiplex on the radio channel. of Science) described a more workaday This year, the 30 papers in a single approach to a voltage -controlled VHF stream of six sessions were largely oscillator with negative dynamic feed- drawn from a limited number of univer- Oscillators - back. They recall that the idea of nega- sities plus a few from NPL, DTI and and tive dynamic feedback in oscillators was RAL. Only a single ERA paper on limitations studied by J. Groszkowski (1952) who EMC standards came from a quasi - dynamic feedback showed that this could reduce the higher commercial organisation. Most of the harmonic content, permitting a better projects appeared to involve at least an Professor Michael Underhill (Philips- frequency stability to be achieved. element of Defence funding. MEL) has recently pointed out (IEE In their paper, negative dynamic The National Committee, as a com- Conference Publication No 303) that feedback is applied to a simple voltage - mittee of the Royal Society. is one of a there is a continuing need for better controlled oscillator based on a dual - number facing dissolution as an eco- purity and stability of oscillators, parti- gate mosfet type BF961. In such oscilla- nomy measure; however, it will con- cularly as the frequencies of operation tors the frequency range is strongly tinue as a panel, rather than the single of communications and radar systems dependent on the gain parameters of URSI representative originally pro- extend ever higher. While he notes that the active element as well as on the O of posed by the Royal Society. It is hoped in principle oscillators can he made the resonant circuit. They consider that to continue the annual NRSC, which is more stable by better control of the it is sufficient to prove that the ampli- less costly for participants than the more physical elements that determine the tude of an oscillator with negative dyna- formal IEE conferences. frequency, the presence of phase noise mic feedback is rendered insensitive to Professor Tudor Jones outlined the is fundamentally inescapable. Phase these influences. Moreover, they point major new SERC initiative in proposing noise can be reduced relatively to the out, such an oscillator can be dynami- a scientific radar within the northern desired output by operation of oscilla- cally controlled and holds the Class A polar cap, possibly to be located at

1024 ELECTRONICS WORLD + WIRELESS WORLD October 1989 RF CONNECTIONS

Longyearbyen, Spitzbergen, at an appreciably higher geographic and DATE geomagnetic latitude than the existing 20/7/88 21/7/88 22/7/88 23/7/88

EISCAP radar installation in northern 20.3-20 9 Norway. ,;17.5-18.2 Spitzbergen would provide access to E144-13.9 .1_7,10-2- 9.9 active areas of the Auroral Oval region §69-68 of intense ionopheric disturbances d5'2-49 under all conditions and could provide LL 3'2 an important new research tool. SERC 0 12 24 0 12 24 0 12 24 o 12 24 believes that the most cost-effective TIME installation, costing about £12 million, would comprise three fixed monostatic Reception times and frequencies ofthe Clyde River (Baffin Island) beacon 32 -metre dishes (one megawatt at about transmissions, monitored at Leicester over a four -day period. A severe disturbance 1GHz) looking in different directions. began on the second day. (University of Leicester). SERC would provide about £2M and is seeking to co-operate with international activity than with the magnetic index. digital signal processor board. partners, including Japan and USA The frequency of the received signals Dr L. Kersley (University College of possibly replacing France of the EIS - is often observed to spread over some Wales) spoke on recent observations of CAP partners (UK, West Germany, ± 10Hz, presumably because of Dop- Sporadic E propagation based on the France, Scandinavian group). pler shift from reflection by travelling reception of East European FM broad- Meanwhile, research into HF pro- ionospheric disturbances (TIDs), cast stations (about 70MHz) as received pagation within and across the Auroral although it has not been possible to at a network of stations in the East Oval is continuing at Leicester Uni- relate the frequency dispersion to any Midlands spaced from 8 to 80km. Little versity, based on beacon transmissions well-def ned feature of the auroral correlation is observed with these spac- from Clyde River, Baffin Island, Cana- ionosphere or to any changes in ings and further studies are being made da (about 700 North). Automatic trans- geomagnetic or auroral activity. Prof. with the spacing between receivers re- missions on 14 frequencies arranged as Jones emphasized that HF signals along duced to less than 10km. The team two sets of frequencies spread through such paths are subject to a whole zoo of supports the wind -shear theory of the the HF spectrum (3185/3230, 4900/ scattering elements: "Distorted wave - formation of SpE clouds of ionized 5200, 6800/6905, 9941/10 195, 13 886/ fronts present serious problems with particles. Vertical movements of ioniza- 14 373. 18 204/17 515, and 20 900/ adaptive (communications) systems". tions occur when a horizontal wind 20 300kHz) come from an Icom 735 The Leicester team, working with blows across the magnetic field. amateur -grade transceiver with Icom computer modelling and the ex- SpE layers form at height where the 2KL linear amplifier providing an out- perimental use of the large Canadian plasma flows towards the layer from put of about 350W to a vertical trapped Wullenweber D/F (direction -finding) both above and below, i.e. at nodes in monopole antenna. The 735 is used with antenna at Ottawa, has developed a the vertical ion velocity profile. Within a very -high -stability reference oscillator new algorithm that improves HF D/F the conventional structure of thermo- to permit accurate measurement of results. Improvements have been se- sphere winds, the nodes or nulls move Doppler spreads. cured by including in the modelling the progressively downwards, taking the Transmission format includes two - generation of a quality factor to indicate layer with them. However, short term minute transmissions on each frequency the reliability of individual measure- changes in the velocity pattern, perhaps with callsign in Morse, 30 seconds con- ments. Reception at Ottawa of CFH due to interfering gravity waves, may

tinuous carrier and 30 periods of Halifax on 8197k 1 lz suggests that a interrupt the slow descent, with short Barker -coded pulses (PSK) to provide useful improvement can be achieved as term upward and downward move- time dispersion. These signals are re- a result of the ability to discard part of ments, fading and reforming. Maxima ceived across the Auroral Oval at the spread of measurements. occur in the morning and afternoon, Leicester on a modified Racal RA6790 At Hull University, advanced syn- with a preference for summer months. receiver (3001Iz bandwidth) using a chronization techniques for MFSK The team has found no evidence of long-wire sloping-vee antenna, and also modems are proving successful. These "two -hop" SpE modes such as those to at Thule. Greenland, where the entire require no specific synchronization which amateur summer -time trans- path is within the polar cap. "overhead" in the transmitted signal, atlantic contacts on 50MHz have been Preliminary results have hen de- but function entirely using the unmod- ascribed: these have been thought not scribed at NRSC and at ICAP89 (E.M. ified. information -bearing signal for- necessarily to involve intermediate Warrington. T.B. Jones. S.M. Orrell). mats: if the transmission is interrupted ground (sea) reflection, but rather to Fig. 3 shows how reception across the or if the propagation delay changes take the form of a "chordal hop", with Auroral Oval is highly vulnerable to suddenly. recovery is automatic. Three signals launched into and out of such ionospheric disturbances. When a techniques have been investigated: entrapment by tilted SpE clouds. Many geomagnetic disturbance occurs. recep- modulation -derived synchronization questions concerning long-distance tion is affected strongly on the day (MDS): code -derived synchronization VHF propagation in SpE conditions following the onset of the disturbance: (CDS); and code -assisted hit synchro- remain unresolved. the deterioration in HF propagation nization (CABS). A modem for systems appears to he more closely correlated operating at 25Obit/s has been im- RF Connections is compiled by Pat with direct observations of auroral plemented on a single TMS320C25 Hawker

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Gen £375 NEW EQUIPMENT K r o I Please for quote on rates HP8290152 525 de yes ew an L20000 rung c'p 1742015 AM FM IO S20MH. Sp Gen wit' SrrK^x£550 HAMEG OSCILLOSCOPE 604 C,.r ire e 605TH, Debt Sweet' Les Component Test two probes 1575 GENERAL TEST AND MEASUREMENT EQUIPMENT MARtONI772015 w,dOH synr 1008,hWnese 1425 HAMEGOSCILLOSC0PE 2036 Dual Trace 2UMH.Compinenl Tester IOIVE peer rev r ter MARCONI 142016 AM FM 10KH/ I70MHz with Strut rsnner Manor' lost I r if., 0 : AL20000 f'essa serge 0000 work ix, probes 0714 TF 0400 Fluke AC/DC Dde'en0.. v M ' .010000 HP51278I meo counter ChM £17500 173 All other rr4deh oleo ab.e MARCU'n TT. 716 w trout syncrun ' £300 DatrOn 1030 RMS digital vo teneter £12500 AMP Veneer d,gilal counter 77170 655 00 2100 TF2.1( TF23031, m 337 (hand gen L17500 MARCONI NOD METE L150 ST AR MERSIpOc 45) Exact phase 10008: Wayne Ken 0244 Urinersal Bodge L250 00 1000 BLACK COUNT ER hysteria1515AM 1 Gen £200 Solanron beouenneres/analym 131002000 Warne Kerr 13641 Un.ersal ledge £12500 APOLLO 10 100MH. Rai ell Feu°4 'Time mervaleh L222 RACAL 9081AM FM I0KHz 104MHz S Gen Synlheseed L600 Feedback varable phase OSC 100104110000 000 Bridge £160 00 4 APOLLO IOU 1001Akh Ills above within°,,!wave's) £295 Urwersal 0150 11P618C oa Generator 1876LN, £400 HML 411 capacitor charger 20Kvnevi £100000 Ampe. 0070030 Video Rer eider 115000 81 AC6 STAR FREQUENCY COUNTERS loop 441 Melees LOO 11P6160 5.gnr Generator I b420Hz £450 £99 Device. instantaneous ralemeter 2751 040 00 EMI 610 Recorder 10.05T(MINT)LI5000 100MHz HP 61dÁ S;na Generator 80021030W 1450 Meteor 600600MHz 1129 Bea 6 Howelldatatesl cal uoelor FM012000 KEPCOPSU 0 20000 0 10M/1PSUOP52000£6000 h RE Rau meeri 101 Sg Gen 01530MHz 86 1,1000, Bo O 1000 IGH, L178 Dane type 1209D tran8stor strobe 160 tad) 4 Mete, Farr ea 040130 AC Voltmeter eel :ac r £750 and B.ACk STAR JUPITOR 500 FUNCTION GENERATOR Sine Square Singer Gertsch phase angle v meter L200 00 40 WI/ F FM Gou'd 0530000 O Scope dear £32500 LEADER sSG. Ira S g Gen AM M 0 I UMW /5 1155TH/Bit I.n 1,,,,,,, IH, LI10 Advance INST PGS2A pule g n/ 1100.00 Owl beam er ¿ISO Scopes 25 WI/ £14000 Stereo M -du Mt OR ON COLOUR BAR .LNFRATOR Pa TV video 1209 Ungar lP Molt'eter £5000 Sander Fir..agude WAVETE, 57 Preigranweb e Waveform Synlhesser 100 M roe Phlepsl 05168 'unction gen /50.00 Dymond St ape 150114 dual lrxe L115 00 I MHz Slue So lei 001 A_c L500 HUNG CHANGOMM"Jo'12d'g't Hari he 128 ranges eolud,ng 10 SE La'x 0 Scope EM10215MHz D/Trace 016000 Bryans X Y Plotters from 075.00 FEEDBACK FG601 Sig Gen 000IH/ IMO Sae S9 To 1115 An K.DC01 Watanabe MC611 S2L multoorder £5000 SWartron C0l400 tube OK no guarantee 0500 MARCONI Automatic Dnlnnor Meter 102337A 4COH or kH, Alarmh wlhbartery,rdleads016ptd1 L3950 R.kadenk' 3 14 2 pen chart recorder £5000 Please r rig for quote onc.p rates Measurescown to 001 £150 As above DOMES Wu 5 £3350 COL n Advance 50628 signal generator £5000 PHILIPS IR BAR GEN PM5519 UHF VHF V de Ner 2l lest Carryag, 4- r £300 ea Pattern 1400 r , r P.O e r een .0 E . -

SMALL SELECTION ONLY LISTED - EXPORT TRADE AND QUANTITY DISCOUNTS Age LANGREX wil

RING US FOR YOUR REQUIREMENTS WHICH MAY BE IN STOCK Cossor Oscilloscopes CDU150(CT531/3) £150 only. Solid state general SUPPLIES LTD purpose bandwidth DC to 35MHZ at 5MV/Cm - Dual Channel -delayed time base - illuminated graticule - Beam finder - Calibrator - power 200V - 250 volts AC - One of the largest stockists and protection cover containing polarized viewer and camera adaptor plate - probe distributors of electronic valves, tubes (1) - mains lead. Tested in fair condition with operating instructions. FEW AVAILABLE - NO PROTECTIVE COVER BUT MAINS LEAD + 1 PROBE -£125 and semiconductors in this country. -TESTED- Manual £15 extra. Tektronix 475 - 200Mc/s Oscilloscopes - tested from £500 less attachments to Over 5 million items in stock covering more £750 as new c/w manual, probes etc. than 6,000 different types, including CRT's, Telequipment D755 - 50Mds Oscilloscopes - Tested c/w 2 Probes - £250. Manual £5 extra. camera tubes, diodes, ignitrons, image Marconi TF2002AS - AM -FM Signal Generator - 10Kc/s to 72Mc/s - £85. Tested intensifiers, IC's, klystrons, magnetrons, probe kit- £15 extra- Manual £10 extra. microwave devices, opto electronics, Marconi TF2002B - AM -FM Signal Generator -1 OKc/s-88Mc/s. -£ 100 Tested to £150 as new- Probe kit £15 extra - Manual £10 extra. photomultipliers, receiving tubes, rectifiers, Marconi TF2008 - AM -FM Signal Generator - Also Sweeper - 10Kc/s-510Mc/s - tetrodes, thryatons, transistors, transmitting from £450 Tested to £550 as new with manual - Probe kit in wooden carrying box - £50 extra. tubes, triodes, vidicons. Don 10 Telephone Cable - I mile canvas containers or wooden drum new from All from major UK & USA manufacturers. £20. Army Whip Aerials screw type F sections and bases large qty available P.O.R. Obsolete items a speciality. Quotations by Test Equipment we hold a large stock of modern and old equipment - RF and AF return. Telephone/telex or fax despatch Signal Generators - Spectrum Analysers- Counters- Power Supplies - Scopes -Chart Recorders all speeds single to multipen- XY Plotters A4 -A3. within 24 hours on stock items. Accounts to Racal Modern Encryption Equipment - Racal Modern Morse Readers and approved customers. Mail order service Senders -Clark Air Operated Heavy Duty Masts-P.O.R. All items are bought direct from H M Government being surplus equipment; price available. is ex -works. S.A.E. for enquiries. Phone for appointment for demonstration of any items, also availability or price change V.A.T. and carriage extra. LANGREX SUPPLIES LTD JOHNS RADIO, WHITEHALL WORKS, I Mayo Road, Croydon, Surrey CR0 2QP. 84 WHITEHALL ROAD EAST, BIRKENSHAW, Tel: 01-6841166 BRADFORD BD11 2ER. TEL NO. (0274) 684007. FAX: 851160 Telex: 946708 WANTED: REDUNDANT TEST EQUIPMENT - VALVES - PLUGS - SOCKETS - SYNCHROS Fax: 01-684 3056 ETC. RECEIVING AND TRANSMITTING EQUIPMENT - GENERAL ELECTRONIC EQUIPMENT CIRCLE NO. 6 ON REPLY CARD CIRCLE NO. 30 ON REPLY CARD

October 1989 ELECTRONICS WORLD + WIRELESS WORLD 1027 ENTS CHRISTOPHER TERO 01-661 8640 DISPLAY APPOINTMENTS £27 per single col. centimetre (min. 3cm). Full page £2160 /2 page £1188 1/4 page £648 Full colour £400 2nd colour £275 Cheques and Postal Orders payable to REED BUSINESS PUBLISHING GROUP LTD and crossed.

A WORLD OF OPPORTUNITY FOR RADIO OFFICERS We offer a secure and rewarding shore -based career in the forefont of modern RF DEVELOPMENT telecommunications technology. Thirty weeks special training (plus 6 weeks for non -typists) will prepare you to undertake o wide range of specialist duties as a RADIO OFFICER covering the complete communication spectrum from ENGINEERS DC to light. To qualify you need to hold or hope to attain: an MRGC or BTEC HNC in a Telecommunications CAMBRIDGE £12K to £18K Neg. subject with the ability to read morse at 20 wpm. City and Guilds //// at advanced level, PROJECT LEADERS incorporating morse transcription skills, would SENIOR DEVELOPMENT ENGINEERS be advantageous. Anyone without the above qualifications DEVELOPMENT ENGINEERS who has 2 years radio operating experience We have challenging work in our very well equipped and in this attractive The work will will also be considered. expanding laboratories City. involve the development of a wide range of new products for the Age - preferably under 45 years. Satellite TV, MATV and CAN markets covering the frequency We offer you: range DC -1750 MHz. Comprehensive Training; Good Career Experienceof RF and analogue circuit design to component level is essential. A knowledge of TV signals would be an advantage. Prospects; Opportunities for transfers The Company offers negotiated salary, career development, within Generous UK and Overseas; good working conditions. Contributory Pension Scheme, 25 Leave Allowances and a Non- days holiday, canteen, sports and social club and relocation contributory Pension Scheme; Job assistance where appropriate. Security; Attractive Salaries - and To find out more about our opportunities, please write or telephone: - much more. David Parkin, Personnel Manager, Labgear Cablevision Salary (Reviewed Annually) - As a Limited, PO Box 182, Abbey Walk, Cambridge CB1 2QN. Radio Officer after training: Tel: Cambridge (0223) 66521. £11,568 rising to £17,057 pain 5 annual increments. (includes shift and weekend working allowance) Labgeor CIVIL SERVICE IS AN EQUAL OPPORTUNITY EMPLOYER. Cablevision : ...... For information :::"` .Zformmore and application r...... write or telephone: A Member of the Te/este Group of Finland THE RECRUITMENT OFFICE, GCHQ; ROOM A/1108 PRIORS ROAD, CHELTENHAM, GLOS GL52 5AJ /L7cHi (1R TELEPHONE (0242) 232912/3

WORK FOR DEVELOPMENT IN PERU RADIO ENGINEER CNR, the nationally coordinated committee for Peru's established WHAT IS AN INVENTION? community radio stations, urgently needs your skills to develop their technical training programme. This responsible and satisfying job BECOME A PATENT ATTORNEY offers you the freedom to use your initiative to create a team of and find out! technical trainers to provide a support service to the country's radio network. for High -calibre Electrical/Electronic Graduates sought CIIR Overseas Progamme acts to challenge poverty and promote training as Patent Attorneys by well -established Anglo - development. CIIR overseas workers are experienced professionals German partnership. motivated to share their skills with local communities in developing Must have an interest in new technology, an analytical countries. approach, a flair for written experession, and CIIR's comprehensive benefits package includes * a salary based on knowledge of German or willingness to learn. local rates * UK allowance * free accommodation * return flights * Competitive salary and excellent prospects for pre -departure grant * insurance cover * discretionary dependents' a minimum two year contract language training suitable applicants. allowance * * * extensive briefings * in country support. Initial traning in Munich followed by transfer to If you have experience and knowledge of analogue elecctronics and London branch. digital circuits, of installing and working with radio transmitters and studio equipment and are looking for a challenging job Please reply with detailed Curriculum Vitae to: TAKE THE INITIATIVE: Phone Sue James now on 01-354 0883 or S. J. Avery, Hoffman Eitle & Partners, write to Sardinia House, Lincoln's Inn Fields, The Enquiries Desk, CIIR Overseas Programme, 22 London WC2A 3LZ Coleman Fields, London 7AF. Please send a 28p SAE and quote REF: RPT/EWW/1 Telephone: 01-404 01 16 WORKING TOWARDS EQUAL OPPORTUNITIES

WIRELESS WORLD October 1989 1028 ELECTRONICS WORLD + WELL ROUNDED ENGINEER ROYAL POSTGRADUATE MEDICAL SCHOOL The person we are interested .i will (University of London) RF have good communication engineering background. Must be willing to do MAINTENANCE ENGINEER - MEDICAL maintenance and servicing and SCHOOL MICROCOMPUTER EQUIPMENT installation of all communicat.ons An Engineer/Technician is required to DES products. Must have a strong desire for establisdh an advancement. equipment management and repair service for Salary: to $45K Canadian per year. We microcomputers and associated devices used for ENGS look after immigration clearance. routine and research work by In the first instance please contact: the Royal Postgraduate Medical School. Extremely Competitive Northern Communication & Salaries Navigation Systems Ltd. Candidates should be capable of electronic servicing PO Box 2317, Yellowknife NWT. to component level and be sufficiently familiar with Canada X1A 2P7. Circuit and System Tel: (403) 873 3953 microcomputers to distinguish between hardware design using leading edge Fax: (403) 920 4282 faults, user difficulties and software problems. The radio architectures. post requires initiative and the ability to work with the If you would like to hear minimum of supervision. Applicants should, about outstanding UK A CAREER IN preferably, have experience of supervising others. and European TECHNICAL AUTHORSHIP Minimum qualifications are BTEC, HNC or equivalent high substantial work experience in opportunities to work in a for There is constant demand electronics/computing. satcoms, C` 1 radar, technical authors throughout mobile radio and personal Industry. If you have a technical Appointment will he on MLSO 2 (£11821 -£ 16890) or background, a qualification in comms, call Ingineur on: MLSO 3 (£15711 - £19543) scale depending on technical authorship can open up experience and qualifications. Both scales include a prospect of a new and rewarding Weighting. 0926 817612 career. For details of a London comprehensive Open Learning For a job description and application form please INGINEUR LTD (Agy), Course, leading to recognised contact the Personnel Office, Royal Postgaduate Pendicke Street, qualifications in this field, send for Medical School, Du Cane Road, London W I2 ONN free information pack to: Southam, (Tel: 01-740 3204) quot;ng ref: AP/RP. Warks CV33 OPN. TUTORTEX SERVICES WW4 Freepost For further details please contact Mr K Wilson, Head ULVERSTON of Medical Electronics. Tel: 01-743 2030 Ext 2210. incinEun Cumbria LA12 7BR Closing Date: 5 October 1989 ENGINEER IN EUROPE Telephone: 0229 56333 782 PRIVATE MOBILE FOR MORE RADIO/TRANSCEIVER VIDEO ENGINEER/TECHNICIAN (MOBILE) Maintenance Engineer required INFORMATION Ref: 82/89 by major courier Co. in SE t CALL: Salary according to experience up CHRIS TERO We have an immediate vacancy for a qualified Video to £15,000. Engineer/Technician to work in the Portsmouth and WEest Phone Dennis on ON Sussex areas. Experience must include maintenance and 661-3033 403 3636 8640 repair of high band U-matics, TBSs, Vision and Sound Mixers, three tube colour cameras and CCUs. The salary package inc ludes the pprovision of a company vehicle and an excellent pension and life assurance scheme. SKY TELEVISION For further information and an application form please contact Mrs A. R. Sive, Assistant Personnel Manager. BROADCAST Telephone: 02407 4461 Ext 407 ENGINEERS

Et7t7r7ffiffiffi7r7t7EEE Sky Television is seeking maintenance engineers to be based at its Centre in ELECTRONICS ELECTRONIC Isleworth, West London. WORKSHOP ENGINEERS Involvement will emend to the maintenance and TECHNICIAN Make your next career installation of the full range of broadcast 4/5) move a milestone not (Grade equipment and applicants will, ideally, have required in Department of a millstone. previous experience in a broadcast environment. Psychology, University of Irrespective of your career Reading, to design and objectives - financial or There will be a requirement for shift work, construct a wide range of geographical - let Cadmus put including nights. specialized equipment. The direction into your search. Departmental research and If you are a Qualified Service, Our benefits package includes: teaching activities depend Sales, Design, Production, Test heavily on the use of Contributory pension scheme or Quality Engineer, send your computers. The ideal C.V. to the address below or BUPA candidate will have had a membership telephone Norwich 761220 for recognised apprenticeship and an informal chat. Five weeks holiday allowance at least two years' of varied experience in electronics. The salary will be competitive depending on Knowledge of BBC and IBM experience to date. micro -computers would be an advantage. Salary scale £8645 Please forward written applications, including to £10632 pa. Application detailed CV, current salary and daytime phone forms available from the Personnel Office, no. to: Louise Stott, Personnel Officer, Sky University of Reading, CADMUS Television, 6 Centaurs Business Park, Grant Way, LIMITED Whiteknights. PO Box 217, PERSONNEL Isleworth, Middlesex TW7 5QD Freepost. Sackvdle P ace Reading RG6 1 AH. 44.48 Magdalen Street Telephone: (0734) 318751. Norwich NR3 I BR Please quote Ref TO1A OfflE7e7ffifflEEEfflEE CHRISTOPHER TERO 01-661 8640 CLASSIFIED DISPLAY: £27 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, c/o Quadrant House, The Quadrant, Sutton, Surrey SM2 5AS). Cheques and Postal Orders payable to REED BUSINESS PUBLISHING GROUP LTD and crossed.

HAVING DIFFICULTY OBTAINING AN OBSOLETE VALVE/MAGNETRON/KLYSTRON? SUMMER SALE (or transistor, I.c., CRT, tray wave tube etc) OSCILLOSCOPES & GENERAL TEST EQUIPMENT All items supplied in tested and working condition. RARE & OBSOLETE TYPES A SPECIALITY! Calibration verified at no extra cost. * ALL POPULAR TYPES STOCKED AT COMPETITIVE PRICES TEK 475 200MHz - D. Beam - DT. Base £485 * SPECIAL PRICES FOR WHOLESALE QUANTITIES TEK 475A 250MHz Phone for details * OFFICIAL ORDERS FROM CVT DEPTS, MILITARY, PLCs, OVERSEAS ETC. WELCOME TEK 7603 c/w 7A 16, 7A 18, 7A26, 7B53A p/ins £999 * PHONE/FAX/TELEX FOR UP TO DATE PRICES ON YOUR REQUIREMENTS HP I 222A I 5MHz Dual Beam £165

Gould OS 1 100-S 1 30MHz Dual Beam £155 Visa - Barclaycard - Access accepted Philips PM32 18 35MHz £325 Philips PM3217 50MHz £325 ONaVALVES Cossor CDU 150 35MHz £149 SE LABS SM 1 1118MHz £145 -:IBIoLLINGTquality - Low Byspeciality - 39 Highlands Road, Horsham, Sussex, RH13 5LS, UK. Phone: 0403 210729. Fax: 0403 40214. Telex: 8727.1 SPECIAL TF2015 GENERATORS ° Office hours Món-Fri 9am-5:30pm. Callers welcome by appointment only MARCONI SIGNAL 10Mhz - 520Mhz AM -FM £300 Also - - (:(1(IhE INTEIi\A7'I(1!1AI, SERI ICES Telequipment CT 17 curve tracer - mint £350 Marconi TF2008 Sig Gen's 10Mhz -510Mhz AM -FM £400 11.1.1 11111511 II \T h Marconi TF2002AS Sig Gen's 10Khz - 72Mhz AM -FM £80 111.151 III III %I III INI111 U, 10 1.5Ghz £99 display always Marconi TF 2603 RF Millivolt We are looking for quality used test instruments. Large kits available. available in our showroom. Accessory Examples: Tektronix 7834 DC -400 MHz storage scope M/F £2500.00 Racal Dana 9915M TXO 8 digit DFM 5I0MHz LED £225 H.P. 8405A Vector voltmeter DC-16Hz RF. Phase volts, etc £750.00 Advance DMM3 Mains/Batt Digital Multimeters Northern Scientific Eton II plus height analyser £450.00 £45 £300.00 incl.case/probes Tektronix P6201 DC-900MHz probe kit Megger Insulation testers 250v, 500v, V8, 9A £35 - £50 VAT and carriage extra. Buisiness Hours 9 30am - 5.00pm. Mon. - Fri. MANY, MANY more items in stock and arriving daily at our three Mail Order available - Send for Stock Lists acre depot ín Nottingham. We are open to callers 9am - Gpm Cooke International, Unit 4, Fordingbridge She. Main Road, Barnham, weekdays - 8am - 4pm Saturday P022 OEB Bognor Regis, West Sussex PLENTY OF FREE PARKING. Telephone: 0243 545111 Fax 0243 542457 Anchor Surplus Ltd., The Cattle Market Dept., off London Road, Nottingham NG2 3GY 8048/41 Cross -Assembler for MSDOS Computers Telephone (0602) 864041 or Fax (0602) 864667 Suitable for all IBM PC/XT/ATs or Clones. Completely compatible with the Intel 8048 Assembler. Rob Taylor (Technical Manager) a 40 Manual and Mnemonic Card. Comes complete wioth page User ALL PRICES EXCLUDE VAT & CARRIAGE 742 Supplied with either 5.25 or 3.5 inch disc - please state which. The XA-48 Cross -Assembler is XA-48 Assembler source code for all available from: members of the 8048/41 family: RECHARGEABLE BATTERIES MAPLE Technology Ltd., WANTED HP799p HP20225 receivers, valves, 8048 8748 8035 8049 8749 8039 Park Road Centre, HPII L199 HP3 L495 Test equipment, 8050 8750 8040 8020 8021 8022 Malmesbury, Wilts SN16 oBY Each of our batteries may transmitters, components, cable be recharged up IP 1.000 scrap and quantity. 8041 8741 8041A 8741A 8042 8742 Telephone: (0666) 825141 times, UNIVERSAL NICAD and electronic BA-TERM CHARGER Prompt service and cash. (charges up to 4 x HP2- M 8 B RADIO Only £49.80 + VAT ('ncluding postage) I1.7and l PP3) WAS ANk L9 75 NOW L5Á`, 86 Bishopgate Street, R, MAINS socT plugs lrabltey Leeds LS1 4BB. a II_-.11'Ir mlo l3 amp socket bk 3. Tel: 0532 435649 41/2 6 712 9 and 12 volts DC at 426881 TO MANUFACTURERS, WHOLESALERS, 300mA Fax: 0532 9956 BULK BUYERS, ETC. TV AERIAL AMUHER - Enloy a clearer. crisper picture with this UHF TV Aerial STEWART OF READING Ampldier Simply plug into aerial lead LARGE QUANTITIES OF RADIO, TV AND Mains powered with FREE TV extension 110 WYKEHAM ROAD, lead READING RG6 1 PL. TEL: 0734 68041. FOR DISPOSAL SEND STAMP FOR FREE CATALOGUE I £8.95 ELECTRONIC COMPONENTS FAX: 0734 351696 SEMICONDUCTORS, all types, INTEGRATED CIRCUITS, TRANSISTORS, DIODES, J.E.C. PO Box 67, EASTBOURNE BN12 3LN Marl Please add LI per order TOP PRICES PAID FOR ALL etc. RESISTORS, C/F, M/F, W/W, etc. CAPACITORS, Order only. p&p costs. RECTIFIERS. THYRISTORS, TYPES OF SURPLUS TEST SILVER MICA, POLYSTYRENE, C280, C296, DISC CERAMICS, PLATE CERAMICS. etc. EQUIPMENT, COMPUTER ELECTROLYTIC CONDENSERS, SPEAKERS, CONNECTING WIRE, CABLES, SCREENED EQUIPMENT, COMPONENTS WIRE, SCREWS, NUTS, CHOKES, TRANSFORMERS, etc. ALL AT KNOCKOUT PRICES > RTICI.Ef FOR SALE etc. ANY QUANTITY. tDa - Come and pay us a visit ALADDIN'S CAVE. 21111 Computer 445 0749/445 2713 HEWLETT I'ACKARD TELEPHONE: I-IP98I6S with disc Basic: I IP 9121 twin WANTED R. HENSON LTD. 31/4' drive, MBA software. IIPIB. plus Receivers, Transmitters, Test North Finchley, London N12. and 21 Lodge Lane, I-11' 722511 fixed bed A4 plotter. all Equipment. Components. Cable IS minutes from Tally Ho Comer) 1613 Boxes, PCB's. Plugs manuals, cables. £2.450.(0 Epson PC Electronic Scrap. and Sockets. Computers, Edge hard disc. 51/4", Hercules with new 30MB Connectors. WANTED: VALVES TRANSIS- restful green monitor. £369.0l. AIM PAID FOR ALL TYPES OF Please mention I.Cs KT66, TOP PRICES TORS (especially types Electronics 501 ultra low distortion, ELECTRONICS EQUIPMENT. KT88 PX4, PX25). Also plugs, sockets IEEE oscillator 81-Iz to 300k1 -1z, £64I. A. R. Sinclair, Electronics WORLD and complete factory clearance. If WIRELESS 9812 programmable Stockholders, 2 Normans Lane, possible, send written list for offer by Time Electronics when replying to IEEI slyítchhox 24 way. £54(1. Nicole) Rabley Heath, Welwyn, return. Billington Valves, phone: 0403 Herts AL6 910 40214. 44. do to I(Nlkltz spectrum analyser 1/4.1 adverts 210729. Fax: 0403 See adjoining Telephone: 0438 812 193 advert. option. £2.350. All first class. octave Mobile 72 0880 214302 with manuals + VAT. known history Fax 0438 812 387 780 01-794 2839. WE BUY AND SELL TOP QUALITY TEST AND MEASUREMENTi EQUIP COURSES RALFE ELECTRONICS z 36 Eastcote Lane, --1 O S. HARROW, Middx HA2 8DB a Tel: 01-422 3593 Fax: 01-423 4009 O Please contact us for our latest stock lists of top-quality re -calibrated, test equipment. Good equipment also WANTED for stock and waiting customers for 'high -end' equipment. TRAINING Stock examples: TEK 2213 60MHz o'scopes £395. HP8559A IBA 21 GHz analyser £4950. HP3582A audio analyser £3250. Af18 3.M 1N31'd1(103 IN3IN321f1SV3IN UNV 1531 A1I1VfIU d01 Short Course Programme All dates are start dates. All fees exclusive of VAT. MANUFACTURERS SURPLUS STOCKS Communications Electronic Components, Test Gear, Radiotelephones, Computers, Photographic and Video Equipment. All at knockout prices. - Introduction to X25 Protocol - 2 days, 18 Sept, £365 Export and Trade Enquiries Welcomed. - Digital Communications 1 - 1 week, 27 Nov, £650 Catalogues available from: 765 - Digital Communications 2 - 2 weeks, 27 Nov, f1200 B. Umber' Electronics, Television 5 Station Road, Littleport, Cambs CB6 10E Telephone: Ely (0353) 860185 - Video Distortion Measurements - 11 days, 18 Oct,28 Nov, £255

RADIO LTD., - Television Principles - 1 week, 4 Sept, 6 Nov, 1650 G.W.M. PCB's DESIGNED AND DRAFTED 40/42 PORTLAND ROAD, WORTHING, - TV Principles & Measurements - 2 weeks, 4 Sept, 6 Nov, SUSSEX. CAD/manual desigrs under- Tel: 0903 34897 taken for single/double sided £1200 Receivers: Racal RA 1 7 Mkll with handbook E 180 boards from initial idea to pro- Eddystone 730/4 E 110 plus carriage Intedrrence Transmission measuring receiver manufactured by Eddystone for totype. Testing and production ritish Telecom 130Kcs to 33MHc Type No 40A if required. Quality pro- -TV Signals & Measurements (Video & RF) - 3 weeks, 6 Nov, solid state mains or battery E 140 inc p&p Racal service 850 calibrators useful for netting VHF/UHF Rs's duct to meet your deadline £1800 and Tx's 12 5 25150KHr channel spacing. mains needs. Quality in design and operation E27 inc Oscilloscope SE Labs SMI 11 - Radio & TV Transmission - 2 weeks, 25 Sept, £ 1200 Twin Beam 18 Megs solid state E 120 plus rapid service guaranteed. British made all brass quality marine carriage ckxks - Radio Transmission (MF & VHF) - 2 weeks, 4 Sept, 23 Oct, eight day mechanical 140m/517n dial round brass PCB DESIGN AND DRAFT- 11 case centre sweep seconds unused E 70 in( Mains Dec, £1200 isolation transformers 2301240v two secondaries ING SERVICES each 230/240v at I OOVA unused E4 each plus p&p 01-316 9571 day 01-552 2346 eve Satellite Television E4 negotiable for quantity Set of handbooks for Hewlett Pat Sara 3585A 4 volumes weight 12 kilos - Introduction to Satellite TV & MAC systems unused. Oilers Secondhand radio telephone equipment available and wanted Many bargains 20 min video (non -Technical) £48 for callers Pye Lynx black and white snurrry cameras from E65 788 - D/D2 MAC- Packet, Distance Learning & 23 min video, £522 Engineering Publications Service BASE STATION AERIALS 146-174Mcs I-IB £5. LB £5. I5 all hodymount complete VI IF highhand Collinear fibreglass sta n - whip base feeder (4.5m) prices ex VAT & For details call Stuart Webber on 0297-22051 less 60h gain 2(0W £27.911. UHF 420- carriage. Generous discounts 20+. Bushy 47(IMcs 60b gain aluminium Collinear Communications. Greenwich. London Harman Engineering Training College (WW2) 500W £24.50. Mobile Aerials VI IF (11-692 6137. Fore St Seaton Devon EX 12 2NS Fax 0297 -24419 fibreglass 3.30 Dh gain 54 £7.311. 1/a wave

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Rate £6 PER LINE. Average six words per NAME line. Minimum £48 (prepayable). Name and address to be included in charge if ADDRESS used in advertisement. Box No. Allow two words plus £15. Cheques, etc., payable to "Reed Business Publishing" and cross "& Co." 15% VAT to be added.

REMITTANCE VALUE ENCLOSED

PLEASE WRITE IN BLOCK LETTERS. CLASSIFICATION NUMBER OF INSERTIONS 111 DAISYWHEEL PRINTERS Olivetti: 25 CPS. daisy printers complete WITH DUAL BIN 720K -3:5-INCH DRIVES'` 09.50+ VAT SHEETFEEDERS and RS232 interface. Emulates IBM, Qume and Olivetti. Ribbons available. £175.00 (carr. £10.00) Japanese made (Y -E Data) high Triumph Adler Royal: 20CPS. 132 column, variable features reliability, modern, low component count, pitch, all the that you would expect from a quality printer. month guarantee, ribbon cast chassis drive. Surface mount design. Six and typewheel included. RS232 interface only. £99.50 (Carr £6.50) HURRY These drives have been removed from STOCKS COMING TO AN END! almost new systems being upgraded. FACIT ULTRA FAST DOT MATRIX PRINTERS They are in perfect condition, are boxed Prints at up to a maximum of 500 CPS. Made to a very high standard for and carry a full six month (money back if continuous use. Compact slimline desktop model (only 26 inches wide). not satisfied) guarantee. 80 track double Ideal for Universities, large mailing lists, central printer in department or any sided 1 M byte (unformatted). £39.50 each (carr. £3) £35 ten or mo e. other serious application £349.00 (carr. £25). Quantities of 25 or more POA. Cradle to fit drive in a 5.25" slot eg IBM pc £5.49 (Carr. £1.00; or free with drive) Power and data connectors to suit HITACHI COLOUR MONITORS £0.99p (carr. free) Box ten 3.5" discs £9.95 (carr. £1.50) CM 1457AE 14" PGA, 30.48KHz. Can be converted to VGA for £75.00 to provide high quality, maximum 640 by 480, £149.00 (carr. £6.50) Circuit for BONDWELL AT COMPUTER £475 286 DIY conversion provided free. Fully IBM AT machine with 80286 running at 10 MHz compatible CM2073A 20" ultra high resolution, 64KHz only £595.00 (carr. £30) Complete with ONE MEGABYTE of RAM, 101 Key keyboard, 1.2 M byte 5.25" floppy drive, Hercules video card. Centronics and serial ports, CM1255DE 12" 24KHz suit Olivetti or convert to EGA? £85.00 (carr. £5) real time clock. 5 expansion slots, MS DOS 3.2 and GW Basic. High CM 1588A 15" very high resolution but no details, hence £149.00 (carr. quality construction by famous name. Small footprint size case with £6.50) power supply all assembled and tested. Lowest ever price in the UK TRANSDATA Model 307 ACOUSTIC MODEM C475.00 (carr. £15) V24 interface, 300 Baud, originate mode, etc. Fits modern or old style EPSON 12" TTL MONO MONITORS (GREEN) - phones £9.95 (carr. £3 00) High resolution, IBM and Hercules compatible. TTL. Supplied complete with leads for direct connection to above or any other PC. £48.50 (carr. £5.50) STC SCRIBE KEYBOARDS Keyboards as supplied with Scribe wordprocessors. These are serial units RACAL V22 MODEM MPS1222 but no data is available £5.95 (carr £3) Microprocessor based modem providing full duplex communication at 1200, 600 and 300 baud Í SOUND EQUIPMENT all second-hand. to the CCITT V22 standard. Features include: STUDIO LOUDSPEAKERS 'Can be used on standard 'phone line (PSTN) and EX -BBC 5-2 15" bass plus 2 HF units £99.50 pair (Carr. £30) private circuit (PC) 'Auto answer but needs EX -BBC LS3-1 as above but in smaller cabinets £89.50 pair (carr. £20) telephone to dial '1200, 600 and 300 baud 'Very EX -BBC LS3-4 compact corner cabinet with one 8" bass plus HF £79.50 high quality construction 'BT approved 'Self tests and loop tests (V54) (carr. £17.50) 'Comprehensive manual included. Uncased card with front panel £24.95 EX -BBC RA8-1 mini monitor approx 14" high smart teak cabinets 8" bass seven cards in rack £195 (carr. one £3.50; seven £15) plus HF £49.50 (carr. £ 10) HARD DISC DRIVES EDC RADIO MICS CDC Wren 80 M byte ST 506 32ms £349.00 (carr. £5) Cygnus hand held system complete with mic., receiver, case and cables. Rodime 26 M byte ST 506 55ms £99.50 (carr. £4) £199 (carr. £4) CDC Wren 35 M byte non standard NRZ interface £69.00 (carr. £3.50) PA LOUDSPEAKERS FLOPPY DISC DRIVES IK WATT SYSTEM £495.00 Shugart SA455 5.25" (360K IBM) 40 track double -sided £34.95 (carr. £3.50) Panasonic 5.25" (720K IBM) 80 track double -sided £34.95 (carr. £3.50) CINEMA PROJECTORS Two x Bondwell 5.25" 1.2 M byte IBM AT style drive £49.95 (carr. £3.50) 35mm Gaumont-Kelle, Xenon lamp house, cinema projectors. Complete with screen, screen motor and sound equipment. Please ring for POWER SUPPLIES details and price. Farnell N180 cased 180 Watt PSU +5V at 20A, + 12V at 2A, -12V at 2A, VAT and carriage must be added to all items. +24V at 5A and -5v at 1A. £26.95 (carr. £3) Everything new unless stated otherwise. Visa Si Access Matmos Ltd. Unit 11, The Enterprise Park, Lewes Road, Lindfield, West accepted 24 hour Sussex RH16 2LX phone service QatfY105 Telephone: (04447) 2091 or 3830 Fax: (04447) 4258

CIRCLE NO. 15 ON REPLY CARD

INDEX TO ADVERTISERS

Appointments Vacant Advertisements appear on pages 1028 -1031

PAGE PAGE PAGE AEL Communications 1002 JAV Electronics 1018 RalfeElectronics 1018 Airlink Transformers 988 Johns Radio 1027 Research Communications 974 Amber Cascon 1026 L J Technical Systems 969 Schlumherger Instruments 945 Audio Electronics 956 Lab-Volt (UK) 10110/OBC Sherwood Data Systems 940 Carston Electronics IFC Langrcx Supplies 1027 Solex International 983 Cavendish Automation 1026 Laplace Instruments 969 South Midlands Computer Appreciation 1011 Levell Electronics 969 Communications 1011 Consumer Microcircuits 940 M & B Radio (Leeds) 1011/954 Sowter Transformers 1011 Crotech Instruments 973 M Q P Electronics 942 Stewart of Reading 1027 Display Electronics 1014 Matmos 1032 Strumech Engineering 988 Taylor Bros. (Oldham) 938/IBC Farnell International 994 Natel 1002 Thandar Electronics 1000 Field Electric 1027 National Instruments 951 Those Engineers 1005/988 I lenrys Electronics 958 Noral Micrologics Audio 954 Thurlby Electronics 942 1 R Group 1017/999 Number One Systems 961 Triangle Digital Services 956 ICOM (UK) 956 Pineapple Software 973 Trident International Exhibitions 1009 ITT Instruments Insert R. Henson 973 Tsien 1026 J & M Computers 1005 Raedek Electronics Co 942 Waveband Electronics 1005

OVERSEAS ADVERTISEMENT AGENTS France and Belgium: Pierre Mussard, 18-20 Place de la Madetaine, Paris 75008. United States of America: Jay Feinman. Reed Business Ltd.. 205 East 42nd Street, New York. NY 10017 - Telephone (212) 867 2080 - Telex 23827.

Printed in Great Britain by Carlisle Web Offset. Caxton Road. Newtown Trading Estate. Carlisle. Cumbria CA2 7NR, and typeset by Graphite Typresettin g. I 81 191 Garth Road, Morden, Surrey SM4 4LL, for the proprietors. Reed Business Publishing Ltd, Quadrant I louse. The Quadrant. Sutton. Surrey SM2 5AS. ( Reed Business Publishing Ltd 1989. F,'/erlruoer., and Wireless World can be obtained from the following: AUSTRALIA and NEW ZEALAND; Cordon & Cotch Lid. INDIA: A. II. Wheeler & Co. CANADA: The Wm Dawson Subscription Service Ltd., Gordon & Gotch Ltd. SOLIDI AFRICA. Central News Agency Ltd; William Dawson & Sons IS.A.i ltd. UNITED STATES: Worldwide Media Services Inc.. I IS East 23rd Street. NEW YORK. N.Y. IMKlll). LISA. Elerctronic& Wireless World $5.95074513í.

1032 ELECTRONICS WORLD + WI RELESS WORLD October 1989 TAYLOR R.F. EQUIPMENT MANUFACTURERS PERFORMANCE

& QUALITY 19" RACK MOUNT CRYSTAL CONTROLLED VESTIGIAL SIDEBAND TELEVISION MODULATOR PRICES FROM £214.13 (excluding VAT & carriage) Prices CCIR/3 £214.13 CCIR/3-1 £273.67 i

_ - p diµ fM YYxt Yr AY CAqqRq Ii v190°r ner a qf 19" RACK MOUNT VHFIUHF TELEVISION DEMODULATOR tL° PRICE AT ONLY £198.45 (excluding VAT. & carriage) rl901toissi

CCIR/3 SPECIFICATION

Power requirement - 240V 8 Watt (available other voltages) Video Input - IV Pk -Pk 75 Ohm Audio Input - 8V 600 Ohm FM Sound Sub -Carrier - 6MHz (available 5.5MHz) Modulation - Negative IF Vision - 38.9MHz IF Sound - 32.9MHz (available 33.4MHz) Sound Pre -Emphasis - 50us Ripple on IF Saw Filter - .6dB Output (any channel 47-860MHz) - .16dBmV (2mV) 75 Ohm Vision to Sound Power Ratio - 10 to I Intermodulation - Equal or less than 60dB Spurious Harmonic Output - 40dB (80dB if fitted with TCFLI filter or combined via TCFL4 Combiner/Leveller

CCIR/3-I - Specification as above but output level 60dBmV I000mV Intermodulation 54dB VVALLMOUNT DOUBLE SIDEBAND Other Options Available - I.F. Loop/Stereo Sound/Higher Power Output TELEVISION MODULATOR PRICES FROM ONLY £109.76 (excluding VAT & carriage) Alternative Applications - CCTV Surveillance up to 100 TV channels down one coax, telemetry camera control signals, transmitted in the same coax in the reverse direction. ird 802 DEMODULATOR SPECIFICATION Frequency Range - 45.290MHz, 470-860MHz A.FC Control - +/- 1.8 MHz Video Output - IV 75 Ohm Audio Output - .75V 600 Ohm unbalanced Audio Monitor Output - 4 Ohms Tunable by internal preset Available for PAL System I or BG

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

CCIR/5 MODULATOR SPECIFICATION Power Requirement - 240V Video Input - IV Pk -Pk 75 Ohms Audio Input - IV rms 30K Ohms Adjustable .4 to 1.2 Vision to Soerd Power Ratio - 10 to I Output - 6dBmV (2mV) 470-860MHz Modulation - Negative Audio Sub -Carrier - 6MHz or 5.5MHz Frequency Stability - 25 Deg temperature change 150KHz Intermodulation - less than 60dB Sound Pre -Emphasis - 50us Double Sideband Modulator(anwanted sideband can be suppressed using TCFL4 Combiner/Leveller)

CHANNEL. COMBINER/FILTER/LEVELLER to combine outputs of modulators

TCFL2 2 Channel Fi.ter/Combiner/Leveller. Insertion loss 3.5dB TCFL4 4 Channel Füer/Combiner/Leveller. Insertion loss 3.5dB Frices TSKO Enables up to 4xTCFL4 or TCFL2 to be combined. CCIR/5-1 1 Modulator £109.76 CCIR/5-2 2 Modulators £167.99 TAYLOR BROS (OLDHAM) LTD. CCIR/5-3 3 Modulators £237.59 BISLEY STREET WORKS, LEE STREET, CCIR/5-4 4 Modulators £307.19 OLDHAM, ENGLAND CCIR/5-5 5 Modulators £376.79 C1RC1 k NO. 2 ON REPLY CAKIJ TEL: 061-652 3221 TELEX: 669911 FAX: 061-626 1736 Telecommunications Training from fundamentals- to state--of=thé---a-rt technology

Lab -Volt offers a comprehensive range of telecommunications training equipment that covers basic RADAR SYSTEMS electronics, analogue arid digital communications circuits and_ systems, _fibre. optics, _and microwave and radar technologies. 11 I MICROWAVE SYSTEMS Our equipment is: modular and easy to upgrade industry relevant

engineered for educational purposes. ADVANCED DIGITAL COMMUNICATIONS SYSTEMS' TOM 80PSK/APK/OAM T1/CEPT MULTIPLEX DPSK/DOPSK Lab -Volt closely relates its telecommunications training equipment to operational systems found in industry, with educational enhancements such as fault insertion switches in many of the modules, DIGITAL COMMUNICATIONS SYSTEMS labelled and easily -accessible test points, short- PAM/PPM/PWM ASK/FSK/PSK PCM/DPCM/DELTA circuit protection, silk-screened component identifi-' cation; and full signal compatibility for system -level modules. We supply student and instructor manuals that are written specifically for the equipment; they ANALOG COMMUNICATIONS SYSTEMS provide practical hands-on technical training with AM/DSB/SSB FM/PM step-by-step exercises, laboratory experiments, and troubleshooting activities. 1

FUNCTIONAL ANALOGUE FUNCTIONAL DIGITAL COMMUNICATIONS CIRCUITS TELEPHONY COMMUNICATIONS CIRCUITS MULTIPLEX FM FREQUENCY SYNTHESIS FIBRE OPTICS PCM/DELTA COMMUNICATIONS FDM SSB PLL ASK/FSK/PSK.- PAM/PPM/PWM

RF COMMUNICATIONS CIRCUITS DIGITAL ELECTRONICS AM/FM

For more information about our telecommunications AF COMMUNICATIONS training equipment, please contact:

'UNDER DEVELOPMENT Lab -Volt (U.K.) Ltd. 4A Harding Way ELECTRICITY/ELECTRONICS FUNDAMENTALS Industrial Estate St. Ives Cambridgeshire PE17 4WR Or Call: 0480 300695 a6- o/t°

CIRCE E NO. 3 ON REI'I Y CARO