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CONTENTSMay 1997Number 255

Volume 23ISSN 0268/4519

42 PROJECT:Compact AF power amplifierDesign by T Giesberts

r FOCUS ON._

20 ISDN:Integrated Services DigitalNetworkBy our Editorial Staff

/ 4I RS & MICROPROCESSORS

26 PROJEC .

Long-distance IrDA linkDesign by W. Hacklander

56 Using the p-i-n diodeBy Joseph Carr

14 PROJECT:Wideband millivoltmeterDesign by F. Hueber

34 PROJECT: LCR meter Part 2Design by H. Bonekamp

52 PROJECT: Logic analyserDesign by A. Ti chten

MISCELLANEOUS. INFORMATION

61 Corrections71 Data sheets82 Index of advertisers49 In passing ...60 P.O. Box 141466 New Books73 New products11 News82 Next month in Elektor Electronics64 Quickroute Pro+ 3.668 Readers' services61 Switchboard

Copyright 1997 Segment BY

CONSUMER PRESS

straightforward

11:40F Irrcomplex-.

LOW COST DEVELOPMENT SYSTEMECAL comprises a versatile relocatable assembler withintegral editor which runs about ten times faster thantypical assemblers. Support includes 4, 8, 16 & 32 bitprocessor families including75X, 6502, 6809, 68HC05/11.8031/51, H8-300, 78K, PICs, ST6& Z801180, 68000, 80C196, H8-500 & Z280.

ECAL is either available for asingle processor family or allfamilies.

Single processor version £295Multiprocessor version.... £395

Overseasdistributors

required

OEMA Ltd.,7 & 7A Brook Lane,Wars ash,Southampton S031 9FHTel: 01489 571300Fax: 01489 885853

The PC based ECAL hardware emulator is fullyintegrated with the assembler. Connection is made tothe target through the eprom socket so a single pod

can support all processors.Facilities include windows forthe inspection or change ofregisters or memory. You caneven watch your programexecuting at source level!

Download time is about twoseconds!

Pods can be daisy -chained for16 32 bit systems.

Applications include softwaredevelopment, hardwaredebug, test and, finally,teaching about micro -controllers in education.

ECAL emulator £475

Quantity discounts ofup to SO% make ECALsoftware ideal foreducation.

Produced and published byELEKTOR ELECTRONICS

Publishing)

Editor: Len SeymourTechnical Editor: Jan Buiting

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Elektor Electronics is published monthly, except in August, by Elektor Electronics (Publishing), P.O. Box 1414. Dorchester, Dorset DT2 8YH, England. The mag-azine is available from newsagents, bookshops, and electronics retail outlets, or on subscription at an annual (1997) post paid price of £30.00 in the UnitedKingdom; AIRMAIL: £38.00 in Europe, £47.00 in Africa, the Middle East and South America; f49-00 in Australia, New Zealand and the Far East; and SUS 64.00in the USA and Canada.Periodicals Postage Paid at Rahway NJ.Postmaster please send address corrections to Elektor Electronics, do Mercury Airfreight International Inc, 2323 Randolph Avenue, Avenel, New Jersey, NJ. 07001.

DIGITAL AUDIO BROADCASTLNG ISDN IN EUROPE FLIGHTS TO RED

PL4NET ' HIGH TECH MARKET FOR ESA MATCHBOX µCOMPUTER

DAB FOR ALL?A new stage in the spread ofDAB - digital audio broad-casting - has been markedby the inauguration in Lon-don of a World DAB Forumto succeed the EuropeanDAB Forum (EuroDab)founded in 1995. At least 20countries, including Aus-tralia, Canada, China, Indiaand many European na-tions, will have operationalor pilot services running bythe end of this year whenthe first consumer radio setswill be available. DAB willtake radio into the multi-media age, offering text anddata as well as near -CDquality sound.

The Forum brings to-gether companies and orga-nizations from all sectors ofthe broadcasting industry --including receiver and otherequipment manufacturers,public and private broad-casters, transmission pro-viders, regulators and sat-ellite operators. The primepurpose is to help take theEureka 147 system of DABfrom the laboratory to theimplementation stage andto work together to make ita commercial and consumersuccess.

It is estimated that in Eu-rope more than 100 millionpeople will be within reachof DAB by the end of thisyear. Most of the world'sleading receiver manufac-turers will be displayingDAB products at the majorInternational ConsumerElectronics Fair (IFA97) inBerlin in August/September.

DAB is a fundamentaladvance in radio technol-ogy, a bigger step than theintroduction of FM, and onewhich- will revolutionizeradio in the way CD hastransformer the music in-dustry. It offers consumersinterference -free reception,near -CD quality sound,easy -to -use sets, a wider

choice of programmes, andtext and data services as wellas audio ones - in otherwords, multi -media radio. Itis the first radio system de-signed to work equally wellwith fixed, portable and carradios.

The Eureka 147 systemnow being introduced in Eu-rope, Canada and plannedfor other countries, as de-vised by a consortium of Eu-ropean broadcasters, re-search institutes and elec-tronics companies. It is theonly digital system to befully specified and to meetthe ITU's requirement for aworld standard. The originalEureka Project membershave since been joined bymany others, and among thepartners are such majormanufacturers as Bosch/Blaupunkt, Clarion, Delco,Grundig, Kenwood, Pana-sonic, Philips, Pioneer andSony.

ISDN IN EUROPEISDN - Integrated ServicesDigital Networks - is a trans-mission technology that hascome to fruition rather belat-edly in most of Europe. For-tunately, because broadband

ISDN, which will almost cer-tainly be based on ATMtechnology, is likely to be alargely compatible enhance-ment, the overall ISDN mar-ket will probably receive asecond chance.

A good deal of credit forthe development of ISDNshould be given to the Euro-pean Commission, whichhas for long been the primemover in the liberalization ofthe European telecommuni-cations market, a processthat has led to the entry ofmany significant new com-panies in the arena.

At the same time, the es-tablished national telecom-munications administrationshave been obliged to be-come more efficient by re-

ducing costs and bureau-cracy, and becoming muchcloser to the user. As ISDNcoverage and subscriptionsexpand, it will, no doubt, be-come the de facto standardfor many types of new ter-minal, and for carrying newtypes of communicationsservice.

There are three dimen-sions of market growth inthe ISDN industry: thegrowth in ISDN networksand the number of sub-scribers, the expansion in theuse of terminal equipmentand adaptors connected tothese networks, and therange of new digital servicesthat offer much enhancedfunctionality compared withthose available using ana-logue circuits. These threefactors are very closely asso-ciated and, indeed, they cas-cade down from one to theother

It is unfortunate thatmost national Telecommuni-cations Administrationshave had somewhat equivo-cal feelings towards ISDN,while they have been gener-ally quite unprepared topromote the types of appli-cation that are needed todrive it. Instead, they havetypically allowed the marketto dictate developmentwithout themselves provid-ing very much of a lead.

This serious failing couldwell be exploited by the newfixed -network operators thatare due to start operations inmost European countriesfrom the start of 1998. Theywill certainly offer ISDN, butthe more strongly financedorganizations could welltake more imaginativestrategies prior to the avail-ability of broadband ISDN,and this trend would ad-versely affect the ISDN mar-ket, certainly for major usersof higher bandwidth.

Nevertheless, severalbasic demographic and cul-

tural developments are com-ing to the aid of ISDN,which should provide astrong market pull in thecoming years. The Internet,for example, cries out for theusage of ISDN access, whilethe strong move in manycountries towards home- ortele-working is rapidly ex-panding the demand forfaster and higher quality, butstill narrowband, communi-cations facilities to be avail-able on a modest cost dial -up basis.(Anyone seriously interestedin western European tele-communications shouldnote that the Financial Timeshas published a report enti-tled 'Liberalizing Telecomsin Western Europe. This re-port provides you with 17country profiles - the 13 EL:countries plus Norway andSwitzerland. Each profilegives you a detailed analysisof the state of liberalization,its impact on both estab-lished and new operators,and the prospects for the fu-ture in each country. Phone0171 896 2235 or fax 0171 8962234 for more details).

EUROPEAN SPACEAGENCY AIMS FOR

HIGH TECH MARKETIN SPACE

(By Dr C R Lavers)The last two years have seenthe development of the Eu-ropean Space Agency's RA-DIUS Programme (ResearchAssociations for the Indus-trial Use of Space), whichhas been established to cre-ate a commercial market forprivate sector utilization ofthe International (formerlyAlpha/Freedom) Space Sta-tion.

The RADIUS Programmeoffers industrial custo,mersthe possible commercial ben-efits of materials fabricationand processing in a micro -gravity environment. Com-panies interested in such

Elektor Electronics 5/97

work have so far come fromareas involving biotechnol-ogy, pharmaceuticals, elec-tronics, optoelectronics andmetallurgy. Several areassuch as the crystallization ofproteins and the purificationof macromolecules, based inFrance, and the growth ofsemiconductor and electro-optic materials, based atFreiburg University in Ger-many have already beentested in space. The Ad-vanced Protein Crystalliza-tion Facility (APCF) hasflown on several Shuttlemissions, and has allowedoptimisation of crystalgrowth parameters, and in-cluded three different meth-ods of crystal fabrication.

A study of fluid physicsand dispersion, based at theMicrogravity Research Cen-tre at the University of Leu-ven, in conjunction withdata from orbital flights hashelped their customer, theFrench oil company ElfAquitaine, to determine theoptimum position of drillingsites and the most effectivemethod of crude extraction .

The next proposal is aFrench health investigationof osteoporosis, wound heal-ing and the study of cancerswhich will have potentialbenefits for the pharmaco-logical industries.

The RADIUS Programmeis to be incorporated intoESA's Manned Space Flightand Microgravity Pro-gramme to guarantee partic-ipants access to space andalso the International SpaceStations which will start tobe assembled from later thisyear onwards.

REVISED RADIOAMATEURS'

EXAMINATIONSCity & Guilds have an-nounced that it is to simplifythe format of the Radio Am-ateurs' Examination (RAE)from May 1998.

Following a request fromthe Radio Society of GreatBritain, the national repre-sentative organization forRadio Amateurs in the UK, ithas been agreed that the re-vision will start in May 1998.

Currently, the examina-tion is taken in two parts, ata cost of £19.40 per paper(E38.80 for the complete ex-amination). From May 1998,the two papers will be amal-gamated into one paper of30 multiple choice questions.The cost for the revised ex-amination will be reduced to£26. Candidates who havepassed one paper of the cur-rent RAE will be able to con-tinue to carry over that passuntil May 1998 when theywill need to resit the fullnew examination. A pass isrequired in the examinationto obtain a Radio AmateurLicence. The RAE is con-ducted at approved exami-nation centres throughoutthe UK in May and Decem-ber every year.

It is hoped that thischange will encourage morepeople to take up AmateurRadio in the future.

For further informationabout the new course, con-tact the City & Guilds Cus-tomer Services EnquiriesUnit at 1 Giltspur Street,London EC1A 9DD, phone0171 294 2801/2805/2797.

INTERNET PROBLEMSAll existing telephone linesare too slow and thereforenot suitable for serious workon the Internet.

Control of the contents ofdata on the Internet is virtu-ally impossible.

All software now in use iswholly or partly not suitablefor serious work on the In-ternet.

There is (as yet) no good,safe and internationally suit-able system for making pay-ments for goods or servicesvia the Internet.

All PCs now in use aremuch too slow for seriouswork on the Internet.

Virtually all existing cablenetworks are intended forunidirectional transmissions.They must be converted forbi-directional traffic.

Copyright control is verycomplex and in many casesimpossible.

The levying of VAT andother local sales taxes ongoods sold via the Internet is

almost certainly impossible.All modems now in use

are too slow for serious workon the Internet.

JAVAOS "I ONARM RISC

Advanced RISC Machines(ARM) and Sun Microsys-tems, Ines JavaSoft businessunit have collaborated to en-able the JavaOS'" operatingsystem to run on the ARMRISC architecture. The ARMversion of JavaOS is now di-rectly available from Java -Soft. JavaSoft will licenseJavaOS for the ARM archi-tectures and provide techni-cal support directly to li-censees electing that plat-form.

JavaOS is a highlycompact, dynamically exten-sible operating system de-signed to run Java" appli-cations directly on micro-processors in anything fromnetwork computers (NCs),PDAs, mobile phones, print-ers and set -top boxes, tocountless other devices.JavaOS is one of the smallestand fastest implementationsof the Java platform avail-able. In addition to the ARMprocessors, JavaOS runs onX86 and SPARC" proces-sors.

ARM's strong semicon-ductor partnership andhigh-performance, power -efficient technology will en-able Sun to build upon itscurrent Java base in the net-work computing market andoffer affordable, user-friendly consumer informa-tion appliances.

ARM is one of the leadingarchitectures in the growingmarket of NCs: Wyse Tech-nology's ARM -based WM-term 4000 Enhanced Net-work Computer (ERIC) wonBYTE Magazine's Best ofComdex award for Best Sys-tem. Additional ARM -basedNCs and Internet appliancesinclude the Acorn OfficeNC, the Alpha Vision KisunInternet Terminal, theBoundless Technology NC,the Daewoofleknema Inter-net TV set -top box, the Ora-cle NC, the TeknemaEasyRider and the Viewcall

Netsurfer.The StirongARM SA -110

microprocessor, co -devel-oped by ARM and DigitalSemiconductor, has thehighest published scores forthe CaffeineMark 2.01 inter-preted Java applet perfor-mance benchmark, in com-parison to other well-knowndesktop systems.The Stron-gARM results were obtainedwith a prototype Internetterminal, a reference hard-ware design for the Stron-gARM SA -110 chip that wasused by Digital to port theJavaOS operating system tothe StrongARM architecture.

The ARM architecture isan ideal solution for cost -and power -sensitive mar-kets. The ARM family in -dudes the ARM7TDMI'Thumb', which reducessystem cost with its excellentcode density, the ARM7500and ARM7500FE, which pro-vide highly -integrated sys-tem solutions for Internetappliances, and the ARM810and StrongARM processor,which enable supercom-puter performance from twoAA batteries.

ARM is the leader in mi-croprocessor IntellectualProperty. ARM designs andlicenses fast, low-cost,power -efficient RISC proces-sors, peripherals and 'sys-tem -chip' solutions for em-bedded control, consumer/educational multimedia,DSP and portable appli-cations. ARM supports itsprocessor offering with De-velopment Hardware andSoftware and contract De-sign Services. ARM licensesits technology to leadingsemiconductor, software,and OEM partners world-wide who focus on appli-cations, design and manu-facturing. Each partner of-fers unique ARM -relatedtechnologies and serviceswhich together satisfy abroad range of end -userneeds. Through this partner-ing, ARM is rapidly becom-ing the global volume RISCstandard.

ARM's semiconductorpartners include: AKM, Al-catel Mietec, Atmel ES2, Cir-

A 12 Elektor Electronics 5/97

rus, Digital, GEC PlesseySemiconductors, LG Semi -con, NEC, Oki, Samsung,Sharp, Symbios Logic,VLSI, and Yamaha.

ARM also partners withleading Operating System,Development Tool, Designand OEM companies fromaround the world.

RED PLANET STILLESCAPES LEGACY OF

RED EMPIRE(By Dr C R Lavers)

The failure of the Mars 96 or-biter launch on 16 Novemberlast year from Baikonur cos-modrome in Kazakhstan willbe remembered as a signifi-cant set -back to the ailingRussian Space Agency. Theagency has suffered a severelack of funding in the after-math of the collapse of theformer Soviet Union. Spacescientists have experienced afall in both real income andin research funds. Many ofthe scientists working on theproject were unpaid - hop-ing against the odds that themission would succeed inspite of an inability even tocarry out vital pre-flighttests. The desperation tolaunch was nothing short ofScientific Russian Roulette,which in this case resulted ina final burn-up somewhereover the Pacific Oceancaused by a failure in thefourth series of booster rock-ets. Without a successfulfinal stage boost it was notpossible for the Orbiter togain the necessary velocityto escape the Earth's gravita-tional field.

What makes this failuretragic is that it was almostcertain to fail; the previousten missions attempted since1962 resulted in seven totalfailures: the other three havedelivered the bare minima oftechnical data. Only a coupleof weeks before the launch,Vasily Moroz, a senior scien-tist on the project, explainedthat funds no longer existedto carry out vital tests on twoof the four landing craft thatthe Orbiter was to dispatch,and that tests would have totake place throughout theduration of the flight, with

any software modificationsto take place as necessary.

The result is that the Rus-sians, although havingnearly four decades experi-ence of powerful spacerocket design, will not be in aposition to mount furtherlaunches to the Red Planet inthe foreseeable future. Thedisaster is not only one forthe Russians, but for the Eu-ropeans as well: twenty Eu-ropean countries, in additionto the USA, had a significantamount of electronic hard-ware on board the six -tonnecraft costing £40 million.Some of the European equip-ment had taken the best partof a decade to design, andreplacement in the shortterm is impossible. Followingin the wake of the Clustermission destruction on ESNsnew Ariane V rocket, the im-mediate prestige of Euro-pean space missions hasbeen severely dented.

The result of these cata-strophes is that NASA hasthe field completely free ofcompetition for any Martianmissions well into the nextdecade. The track record forNASA is more encouragingsince the failure of the firstMars Observer upon enter-ing Martian orbit a couple ofyears ago. On 4th July thisyear, the Mars Pathfinder (as-suming a more successfullaunch than the Mars 96probe) will descend on to anancient Martian flood plainand will signal the first USreturn to the Red Planetsince the Viking missionsback in the seventies whichbroadcast stunning informa-tion for a couple of years. Itwill deploy a small rover toexplore the region aroundthe lander and will photo-graph the terrain in a rangeof spectral energies. Theoverall aim is quite simple: toestablish whether a low-costsoft landing is possible. Thiswill be followed in Septem-ber this year by the MarsGlobal Surveyor, which willrelay information obtainedfrom the Mars Pathfinder.The Mars Global Surveyorwill enter into orbit aroundMars by 'aerobraking', that

is, using friction with theplanet's tenuous atmosphereto decelerate it. It will scanthe surface from a height of400 miles and give a resolu-tion of one metre.

The Americans intend tosend a pair of spacecraft toMars every 26 months until2005, with a possible sample -return mission launched asearly as 2003. A landerwould deploy a robotic roverto collect geological speci-mens and a return rocketmay insert the samples intoan Earth orbit for possibleanalysis on the InternationalSpace Station. The Europeannations would be wise toconsider future partnershipswith NASA if they wish tomaintain a stake in the ac-tion. Apart from Japan noother country has the tech-nological expertise, thewillpower, and the money, toreach out and, hopefully,land safely on the RedPlanet.

MCS251 µCOMPUTERIN A MATCHBOX

Based on the latest SIvID andmultilayer technology, mi-croMODULE8 from Phytecrepresents the latest in sub-miniature microcontrollerboards. Equipped with theIntel MCS8XC251 8 -bit con-troller, the microMODULE8is a computer in matchbox

x36x8 mm) format. Thiscan be treated rather like a'big chip' on a larger appli-cation board.

The MCS251 family mi-crocontroller can be run in adownwards compatiblemode to the 8051. Thismeans that existing 8051 soft-ware can be run on the mi-croMODULE8 without anychanges having to be made.With the same crystal fre-quency, the existing 8051code is executed up to 5xquicker. Application pro-grams that use the MCS251code, running in the 'sourcemode' of the controller, areup to 15x quicker

In addition, the MCS251controller on the micro -MODULES can run in thepage mode. The speed ad-vantage gained from this is

useful and arises from thefact that during a page hit nofurther high address linesare placed on the multi-plexed bus.

Various forms of the 251currently exist: Step A toStep C. The latest Step Ccontroller operates in the 18address -line mode. Thismeans that the external ad-dressing totals 257 Kbytes.Flexible address decoding al-lows for the easy partitioningof the address space. Whenconnecting external periph-erals, three additional chipselect signals are available.

The microMODULE8'sdock frequencies are up to16 MHz, allowing for ahigher data throughput. Thememory consists of up to512 Kb SRAM and 512 Kbflash EPROM, sufficient forcomplex applications.

The on -board program-ming of the flash EPROMsvia the serial interface to theRS232 allows for the simpleconfiguring of the memory,the downloading of the ap-plication programs, as wellas in -the -field software up-dates.

The serial interface can al-ternative be configures toeither RS232 or RS485. Inorder to function, the micro -MODULES only requires aregulated 5 V supply. Its cur-rent drain is about 120 mA inthe temperature range of0 °C to +70 'C.

Powerful MCS251 devel-opment tools, i.e., C com-piler, assembler and debug-ger, are also available fromHitex (see p. 8) for softwaredevelopment. During pre-liminary stages, or whendealing with small appli-cations, an efficient monitordebugger is available.

The standard micro -MODULES comes ready -as-sembled and tested. It is fit-ted with 128 Kb SRAM and128 Kb flash EPROM, allnecessary documentation,embedded pin/socketboards, and a utility diskwith flash programmingtools.

The price of the standardmicroMODULE8 is £125.


High -frequency sig-nals cannot be mea-sured with standardvoltmeters or multi -

meters. Such volt-ages, which are com-

monplace inreceivers, transmitters

and other high -fre-quency equipment,

can only be mea-sured with a special,

wide -band millivolt -

meter. Commercialversions of this kind

of instrument tend tobe expensive. This

article shows that ifcertain limitations areacceptable, it is pos-

sible to construct asuitable instrument

with modest means.

Design by F. Hueber

wide -bandmillivoltmeteraccurate measurements

with simple means

Standard operational amplifiers are notsuitable for use in test drcuits owing totheir frequency limiting properties.Even special op amps can operate overa frequency range of only a few hun-dred kilohertz. It is for this reason thatin wide -band instruments the circuitsare often designed with discrete r.f.transistors. These transistors provideonly small amplification and low -impedance circuits, require goodshielding, and are fairly ex -pensive.

Brief specificationFrequency range 30 Hz -3 MHz (±0.2 dB, ±1 digit)

«10 Hz- 15 MHz (-3 dB,Measurement ranges 200 mV, 2 V, 20 VLower measurement limit about 10 mVInput impedance 50 fl shunted by 15 pF

(may be switched to 20 IQ)Display 3.5 digit liquid crystalPower supply 240 V, 1.5 VA

A possible alternative is the use ofan r.f. rectifier probe followed by a d.c.amplifier, but this design may experi-ence stability problems. Also, owing tothe curvature of the operating charac-teristic of the rectifier, the frequencyrange is too narrow for a reasonablequality millivoltmeter

A better idea is the use of op ampswith current feedback which havebeen available for several years andwhich can be used in rf. circuits. Infact, they are used as video amplifiersin television receivers, as antennaamplifiers, and in a score of other typesof r.f. circuit. Thanks to the vast pro-duction quantities, the price of thesedevices is also very reasonable. All inall, these op amps are eminently suit-able for use as instrument amplifierand rectifier in a millivoltmeter.

It is, of course, possible to measureII. signals with an oscilloscope, but notas accurately and conveniently as witha millivolbneter with digital display.

A14 Elektor Electronics 5/97

The block diagram of the millivolt -meter based on an op amp with cur-rent feedback as described in this arti-de is shown in Figure 1. Note that adata sheet of the op amp is given else-where in this issue.

Since it assumed that in the vastmajority of circuits to be tested withthe present instrument the highest cf.voltages will not exceed 20 V, thislevel is chosen as the upper inputlevel. This greatly simplifies thedesign of the input stage, since a lin-ear input voltage divider would needa number of expensive high -tolerancecapacitors.

VTRI2122112YIVAS

CIRCUIT DESCRIPTIONThe tf. component of the signal to bemeasured (the measurand) is appliedvia input socket K1 to a potentialdivider. The value of coupling capaci-tor Cs is fairly high to ensure that evenlow -frequency signals are passed with-out loss. Since large -value foil capaci-tors do not have good r.f. properties,C2 is shunted by a ceramic capacitorC1. To_ ensure a stable 50 SI inputimpedance, R1 may be switched intocircuit with SI.

The potential divider consists ofresistors R2, R3, and R14, and compen-sating capacitors C3 and C.I. Thedivider ensures a stable source imped-

ance at the non -inverting input of ICI.This is important since this IC, in com-mon with virtually all ri. op amps,requires a fairly high input current. (Avarying source impedance wouldresult in constantly changing input off-set voltage). The present designensures an input impedance of 22142,which is a reasonable compromisebetween the requirements of r. and Lf.measurement techniques.

The three voltage ranges, 200 mV,2 V and 20 V, are selected with switchS2. In the two lower ranges, the inputsignal is applied directly to the inputof the op amp, but in the higher range

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it is first divided by ten.Diodes DI and Ds are the usual

limiting devices that short-circuit toohigh or too low input signals to thesupply line. The use of a resistor ascurrent limiter is not possible since itwould form a high-pass filter with theinput capacitance, which would nar-row the usable frequency range. Itshould, therefore, be noted thatalthough the instrument is a.c. cou-pled, it can cause a short-circuit whenthe signal level or the signal frequencyis too high.

Diodes D9 and D10 are protectiondevices against too high or too lowsupply voltages.

Circuit ICI is arranged as a stan-dard x2.5 amplifier, whose offset iscompensated with preset P2. Since theoperation of this type of op amp isstrongly dependent on the ambienttemperature, preset P1 provides addi-tional fine compensation of the offsetvoltage. Resistor R7 increases the out-put load of ICI. This resistor is recom-mended by the manufacturer of ICI" toobtain a large bandwidth.

Circuit IC2 is arranged as a classicalhalf -wave rectifier (with offset com-pensation if required). NetworksR11 -D3 and RIB -D4 form a constantload for the two half waves at the out -

112

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put of IC,. These diodes cannot bestandard 1N4148 or BAT85 types, butmust be suitable for use in cf. circuitswith very low capacitance, Co, andvery low recovery time, t11. In the pre-sent design, the BAT81 is used (C0«1.6 pF and ta.«1 ns).

It is not only the peak voltage, UF,(about 500 mV) that plays a role in thelimiting of the voltage level in linearrectification, but also the x1000 ampli-fication of the op amp. The theoreticalminimum level is = 500µV.Owing to the effect of output offsetsand various non-linearities, this figurereduces by a factor 10 and even a littlemore at the extremes of the frequencyrange. In general, however, it may be

Elektor Electronics 5/97 15

2Module Type 120120 (seim from sack)

Figure 2. How to con-nect the millivoltmeterboard to a commer-cial voltmeter module.

assumed that the output is linear withinput signals of 10 mV and higher.

The half -waves at the output of IC,are rendered into a smooth direct volt-age by integrator R13-05.

Precise calibration is afforded bymaking the potential divider variable(R13 -R15 -P4).

In the 2 V and 20 V ranges, resistorsR16 and R17 divide the voltage by 10,so that the output of the millivoltmeteris a direct voltage of 0-200 mV. Thethree display ranges are distinguishedby S2, switching the decimal point asappropriate.

The rectifier is intended for usewith sinusoidal signals and producesthe average value of these. When asquare -wave signal is being measured,the display shows a value that is 11%too high (form factor = 1.11).

The power lines are provided by an

integrated mains supply that uses ashort -circuit -proof mains transformer.The secondary voltage of the trans-former is rectified and stabilized to±12 V by two regulators. The ±5 Vpower lines for the display module arestabilized by D9 -R18 and D10 -R19.

DISPLAYThe millivoltmeter may be built as astand-alone unit or as an adaptor for adigital multimeter (DMM). In the lat-ter case, the earth and the test outputcircuit of the instrument are linked viaa suitable cable to the DMM, whichshould be set to its 200 mV direct volt-age range. Mind the decimal point!

Connecting the instrument to a liq-uid -crystal -display (LCD) module israther more complicated since the cir-cuit and the board layout are not uni-form. The most frequently encoun-tered (and least expensive) moduleuses an analogue -to -digital converter(ADC) Type 7106 and needs only asimple 9 V supply line (such as a PP3battery).

The -ve terminal of the battery(-BAT) must NOT be linked to the sig-nal earth line LO), even when themodule internally generates the req-uisite negative (wr.t. the signal earth)voltage.

When all these points are found inorder, the LCD module may be con-nected to the millivoltmeter board viaterminals K, as shown in Figure 2.Modules that are provided with rangeresistors should be wired permanentlyin the 200 mV mode.

Next, link up the four wires viawhich the decimal point is controlled.The decimal -point terminals are notthe same in all cases: often, theirsequence is not uniform. So, it is vitalto consult the connection diagram ofthe display module when connectingdecimal -point switch S.

Current feedbackOperational amplifiers (op amps) with cur-rent feedback are outwardly indistinguish-able from those with voltage feedback. Inthese types of op amp, the current throughthe feedback loop determines the perfor-mance. This is because the inverting (-ve)input is not connected to a high -imped-ance differential amplifier, as in a standardop amp, but to a low -impedance emitterfollower. Therefore, such an op amp, suchas the LT1252, is eminently suitable for dri-ving low -impedance (and capacitive) loadssuch as a coaxial cable. In fact, it can beused in all applications that require a largestable bandwidth that is independent ofthe amplification factor, a high slew rate,and good linear transfer.

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CONSTRUCTIONSince the instrument is intended formeasuring signals at frequencies up to15 MHz, it is best built on the double -sided, through -plated board shown inFigure 3. The construction is not par-ticularly difficult. During soldering, itis advisable to place a strip of card-board under the component beingworked on to avoid it touching theground plane.

Of all the components, only poten-tial dividers R, -R3 and R16 -R17 shouldbe soldered on to PCB pins.

Do not yet solder ICI and IC, intoplace.

When all components (except ICIand IC,) have been soldered intoplace, carefully check their polarityand position where relevant andinspect the board for dry joints andany blobs of solder that may latercause adjacent tracks to be short-cir-cuited.

Set all potentiometers to the centreof their travel, connect the mains volt-age and check the following voltages:across C6 and C7: about ±17 V;at pins 4 and 7 of ICI and 1C2: -±12 V;at pins 7 and 8 of K,: about 4.7V.

If these potentials are found allright, disconnect the mains and solderthe ICs into place.

Fit the board and display moduleinto the case, and wire up all parts,including the BNC socket, poten-tiometer Pi and the range switch.

Reconnect the mains voltage andcheck that the display reads 'some-thing'; set the decimal point with therange switch.

CALIBRATIONLeave the instrument on for about15-20 minutes to enable it to reach itsnormal operating temperature. (It isgood practice in later use also to let theinstrument warm up for about fiveminutes before making any measure-ments).I. With open input, Si open, P1 at thecentre of its travel, and S, in the200 mV range, measure the offset volt-age at pin 6 of ICI with a digital mul-timeter (DMM) set to its 200 mV a.c.range and adjust P, until the DMMshows 000.0 mV. Disconnect the DMMand adjust P3 until the millivoltmeterdisplay also reads 000.0 mV.2. To set the sensitivity, reconnect theDMM to pin 6 of IC1 and apply a300 Hz sinusoidal signal at a level ofaround 190 mV to the input. Adjust P4until the display shows the same valueas the DMM.3. To check the precision of the poten-tial divider, leave the signal generatorconnected to the input (300 Hz at190 mV) and set the range switch to2 V, whereupon the display shouldread 0.190. Connect a low -value resis-


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Parts list

Resistors:RI = 49.9 a 1% = 200 id), 1%R3 = 22.1 kf2, 1%R4 = 220 kilR5 = 590 (/R6 = 910 i2R7 = 750 ctR8 = 100 kitR, = 100 SZ1110-Ri2 = 392 it, 1%A13 = 10 kI2R14 = 22R15 = 33 MIR16 = 900 la 1%R/7 = 100 Ica 1%R16, R19 = 1.5P1 = potentiometer, 100 kf2, linear

P3 = multiturn preset, 20 kU. radialP. = multiturn preset. 100 k12, radial

Capacitors:C.. CI0-C15 = 100 nF. ceramicC2 = 4.7 pF foilC3 = trimmer, 20 pFC4 = 100 pFC5 = 1 pF, foilC6, C7 = 220 pF, 25 V, radialC6, C9 = 47 pF. 16 V, radial

Semiconductors:D1. = 1N4148D3, 04 = BAT81D5 -D6 = 1N4001D,, D10 = 4.7 V zener, 500 mW

Integrated circuits:ICI. IC; = LT1252 (Linear Technology)IC3 = 7812IC4 = 7912

Miscellaneous:K1 = BNC socket. chassis mounting = PCB mounting 8 -way pin headerK, = 2 -way PCB terminal block with

screw clamps, pitch 7.5 mmS1 = single on switchS2 = 3 -pole, 4 -position rotary switchTr1 = mains transformer, secondary

2 x 12 V. 1.5 VA, short -circuit -proof. e.g.Vefleman 2120018M (from Maplin)

Case 150 x80x 55 mm (Bopla E440 orOKW A9032065)

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tor in series with R17 if the reading issmaller or in series with R16 if it islarger.4. Repeat the same procedure as in 3.,but increase the signal generator out-put to 1.9 V and set the range switchfirst to 2 V and then to 20 V. The rele-vant resistors are then R2 and R3.5. Reduce the output of the signalgenerator to 190.0 mV and check that

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the setting of P4 still gives the requiredsensitivity. Readjust the control as in 2.if necessary6. To set trimmer capacitor C3 as nec-essary, set the range switch to 2 V andthe signal generator output to a levelof 1.9 V and its frequency to >300 Hz.Note the display reading. Then, set therange switch to 20 V, whereupon thedisplay reading should remain thesame. If not, correct it by adjusting C3as appropriate.

This completes the calibration: themillivoltmeter is now ready for use.

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Elektor Electronics 5)97

72r focus on: ISDNdigital communication lines

Some of the mostlikely causes for the

increased demand forISDN connections arethe wider acceptance

of fax machines forprivate use, the needto have several tele-

phone lines available,and, of course, the

widespread use of theInternet as a global

medium. What isISDN, what does thesystem offer, and forwhom is it useful? Inthis article we exam-

ine the history andtechnical features ofan ISDN connection.

By bur eclitciaTstaff

ISDN (Integrated Services Digital Net-work) is an advanced, but by not nec-essarily new, set of telecommunicationservices based on a digital version ofthe existing telephone networks(PSTN, public switched telephone net-work). Instead of analogue signals,which have been used ever since theinvention of the telephone, the ISDNsystem employs digital datastreamswhich may, in principle, be conveyedvia available PSTN links. Because thedata format is the only elementary fac-tor in a digital system, ISDN offers farmore applications than just voice calls.The term data formal covers, amongothers, the structure of the data blockand the associated control signals.Since nearly all digital informationmay be translated or converted into auniform format, ISDN is a good choicewhen it comes to distributing digitisedaudio, video and high-speed data. Themain condition for this to be realisedis that sufficient bandwidth is avail-able. The advantages of digital asopposed to analogue communicationare obvious: improved speech quality,higher transmission speeds, fewertransmission errors, greater flexibilityand shorter dial -up and connectiontimes.

HISTORYIn the nineteen -fifties, there were basi-cally two networks for telecommuni-

cation: the public switched telephonenetwork (PSTN) and a digital telex net-work for written (typed) messages.Since its introduction, the analoguetelephone network has seen few ele-mentary changes, while the telex net-work is based on a primitive digitalstructure using a speed of 50 bits/s.

In the early seventies, the limitedspeeds and long switching timesrequired to set up telephone or telexcalls prompted network and telecomoperators to investigate the feasibilityof specialized digital network services.By and by, the telex network wasphased out as it faced increasing com-petition from services using packetswitching. In 1976, the X25 protocol forpacket suitching was accepted, allow-ing standard data rates of 4,800 and9,600 bits's.

TELEPHONE GOESDIGITAL, TOOAlongside the above mentioned devel-opments, the regular telephone net-works underwent a change to digitaltechnology. Using digital techniques,vast improvements were achieved inthe speech quality on long-distancecalls. The audio information (speechsignals) was initially sampled at 8 kHz,as well as 8 -bit encoded. The result is adatastream with a speed of 64 kbWs.Since the early seventies, telephonenetwork operators have gradually

20 Elektor Electronics 5197

pushed back the older analogue sys-tems, replacing them with a digitalinfrastructure. The digitally enhancedtrunk links have a capacity of 30 digi-tal channels (23 in the USA) which areconveyed in interleaved fashion.

ISDN: THE BASICTECHNOLOGYIn a nutshell, ISDN is the digital coun-terpart of the conventional analoguetelephone line. The term IntegratedServices means that a number of ser-vices are coupled to this infrastructure.The ISDN standard was laid down bythe CCITT in 1984, and extended in1988 by the European Telecommuni-cation Standards Institute (ETSI).

An ordinary telephone connectionhas a bandwidth of about 3,100 Hz(300-3,400 Hz). The equivalent amountof information may be conveyed overa digital channel with a bandwidth of64 kbit/s. In telecom lingo, this is calledthe B (bearer) channeL With ISDN, a16-kbit/s D (diagnostic) channel isadded to the B channel. With an ordi-nary telephone call, the B channel isused to exchange digitised speech,while it conveys data when two com-puters are connected to it. The extraD channel is a common signalling chan-nel which is used to convey, for exam-ple, control information, electronicpayment and personal identification,and signals generated by alarm sys-tems. The extra services are suppliedvia this additional channel, and so donot affect the main channeLIn the UK, ISDN is supplied in twoflavours by British Telecom: one usinga system called Basic Rate Access (BRA,also called ISDN-2), and another calledPrimary Rate Access (PRA, also calledISDN-30). The essential differencebetween these two versions is thenumber of B channels put to the cus-tomer's disposaL

BASIC Rate Access ISDNBasic Rate Access ISDN is the directreplacement for the analogue tele-phone line, and thus the obviouschoice for private customers andSOHO (small office/home office) users.The actual connection is made via thetraditional (already available) copperwires.

By exploiting the benefits of digitaltechnology, a Basic Rate ISDN con-nection considerably expands the pos-sibilities of an ordinary analogue con-nection. Each Basic Rate ISDN con-nection gives you two B channels witha digital bandwidth of 64 kbit each.and one D channel with a bandwidth

of 16 kbit/s.By trading in one analogue phone

line against this basic ISD\ connec-tion, the subscriber gets two telephonelines which may be used indepen-dently. This allows you to surf theInternet or send long faxes while theother line is used to place or receive anordinary phone call. With most ISDNequipment, these two lines may beconnected to put a call through. Fur-thermore, it is possible to bundle thetwo B channels, which creates a singledigital channel with a bandwidth of128 kbit/s. An ISDN-2 connectionallows up to eight extensions to beconnected, of which two may be usedsimultaneously.

Primary Rate Access ISDNThe Primary Rate Access ISDN con-nection (ISDN-30) offers 30 indepen-dent B channels and one D channelwith a capacity of 64 kbit/s (30B+D). Aconnection of this type is intended forprofessional users, for example, largecompanies, which may employ (andpay fort) ISDN-30 to enable their tele-phone exchange systems and local net-works to communicate with the out-side world.

Because of the large difference incapacity between Basic Rate and Pri-mary Rate ISDN (2B+D versus30B+D), some network operators alsooffer slimmed -down versions of PRAusing, for example, six B channels(6B+D).

ISDN AT HOMEAt the end user (customer) location,the two -wire ISDN connection has tobe terminated with a so-calledLinebox. This interface converts ISDNline signals to a 4 -wire bus (called S -bus

Figure 2. A standard ISDN-2connection allows up to8 users to be connected.

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by BT and the CCITT), and employs anormal telephone cable.

There are two connection arrange-ments available for the ISDN equip-ment: point-to-point or point-to-mul-tipoint. In point-to-point mode, oneISDN device is connected, and thecable may have a length of up to 1 km.In point-to-multipoint mode, up toeight ISDN devices may be connectedin parallel, in which case the distancecovered by the cable is reduced toabout 200 m. The end of the S -bus isterminated by resistors, while theequipment is connected with the aidof an 8 -pin version of the standardmodular telephone plug (RJ-45).

Apart from two transparent B chan-nels of 64 kbit/s each and the 16-kbit/sD channel, the S -bus also conveysbytes which arrange miscellaneousfunctions including synchronisation.

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Figure 3. Dependingon the number ofextensions in thehome (or small office)either a point-to-pointor a point -to -multi -point link is set up tomake the connec-tions.

The control of the datastream involvesan overhead bandwidth of 48 kbit/s,resulting in a total traffic of 192 kbit/swhich may be conveyed via the S -bus.

In a system with several devices inparallel, each device (extension) isgiven access to the D channel using aspecial procedure. The B channel,

I Figure 4. ISDN sub-scribers may continueto use their existinganalogue telephoneequipment. An AiD-DIAconverter is insertedbetween the ISDN lineand the 'old' equip-ment, while the newerISDN equipment isdirectly connected tothe ISDN line.

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however, is reserved for the devicewhich was involved in establishing theconnection. All other devices areexcluded from this channel while thecall lasts.

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EURO ISDNAs is often the case when new servicesand/or options are introduced, anundesirable number of (partly) incom-patible versions arises within a shortperiod if there is no tight regulationright from the start. ISDN, too, was asad example of this happening in prac-tice. In many cases, national telecomoperators set their own standards forlocal markets. Not a problem for mostusers, fortunately, because everyonewithin a one country will use the samesystem. A major stumbling block, how-ever, for the development of a globalor European market Taldng hardwareacross national borders is only possibleif international standards are definedand accepted. In 1993, most Europeantelecom operators signed a Memoran-dum of Understanding in which theyagreed to offer services complyingwith a European standard: Euro ISDN.The following services and/or facilitieshave been defined for this standard:

Basic Rate Access (BRA) and Pri-mary Rate Access (PRA);

Q> a voice service which connects tothe analogue standard;

Q:e a data speed of 64 kbit/s per chan-nel.

Furthermore, the following five sup-plementary services have been defined:

Calling Line Identity Presentation(CLIP);Calling Line Identity Restriction(CLIR);Direct Dialling In (DDI)Multiple Subscriber Numbering(MSN);

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SUPPLEMENTARYSERVICESAs few of you will be familiar with theexact meaning of the above mentionedextra services, short descriptions aregiven below

As implied by its name, Calling LineIdentification Presentation (CLIP, actuallya standard service with ISDN) ensuresthat the called customer can requestthe identity of the calling party Thisoption works within ISDN networksonly, and may be disabled by the call-ing party for reasons of privacy.

Using the Connected Line Identifica-tion Presentation feature, the caller getsan identification of the called numberas soon as the connection is estab-lished. If the number is not available,or set as not released by the calledextension, the calling subscriber is noti-fied accordingly. Two special functions,Calling Line Identity Restriction andConnected Line Identity Restriction,allow the displaying of phone num-bers to be disabled for identity protec-tion (per call or permanently).

Multiple Subscriber Numbering(MSN) enables up to eight directorynumbers to be allocated to one ISDN-2 line.

Thanks to Terminal Portability (ter-minal disconnect/connect), an ISDNuser may carry his/her ISDN terminalset to another socket on the sameISDN-2 line without losing the call.

In addition to these standard func-tions, lots of other services may beoffered including billing information,number blocking, call announcementduring a call, and connect -throughfunctions. The availability of these sup-plementary services depends on what isoffered by the telecom providers, andthe demands of their customers. Inmost cases, supplementary services areoffered at extra cost.

As already mentioned, each ISDNlink has a D channel besides theB channels. The D channel isemployed for the so-called carrier andtelesenices. The carrier services playan important part in the linking ofISDN and the traditional telephonenetwork, PSTN. In the ISDN infra-structure, the function of the teleser-vices is to ensure that the right exten-sion/device of a customer is reached(for example, telephone set, fax orcomputer).

BEARER SERVICESThe bearer services indicate the typeof information conveyed via an ISDNchannel. The following bearer serviceshave been defined for use within EuroISDN:

64 kbit/s unrestricted;Q:e 64 kbit/s structured for speech;

64 kbit/s structured for 3.1 -kHz audio.

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IF71:411-14Every ISDN link makes use of one of


these three services. Each time a con-nection is being set up, the right ser-vice is automatically selected.Although the data speed is 64 kbitls inall three modes, it is still essential forthe characteristics of the relevant infor-mation to be accurately known, mainlybecause the network operator makesdifferent selections depending on themode. An ordinary yoke call, forexample, has different requirementsfrom a computer connection. Withvoice services, especially transatlanticones, the usual selection is data com-pression. With data links, data corrup-tion or loss can not be tolerated. Anidentification of the connection typethus makes it easier to make the bestuse of the available infrastructure in anefficient way. The overview belowshows the options available for 'treat-ing' (or processing) the datastream.4:;P In 64 kbit/s unrestricted mode, a fully

transparent link is employed, and

Figure 5. Using a spe-cial insertion card likethe Elcon Diva Pro 2.0pictured here, any PCmay be linked to theISDN network. Thisbrings fast data con-nections within reachof any PC user.

data processing is not allowed.cw,-s In 64 kbit/s structured for speech

mode, analogue -to -digital junctionsmay employ conversion toG.71I/G.713. Underway, compres-sion up to 32 kbit/s is allowed.The 64 kbit structured for audio modetreats the datastream in the sameway as speech signals, but thenwithout recourse to echo cancella-tion circuits. This type of link isintended for analogue modemscommunicating via ISDN.

Analogue modems justas fast as ISDN?As we write this, modem manufacturers are consolidating a new standardto achieve a data speed of about 56 kbitls using 'ordinary', analogue tele-phone lines. This would make data communication across an analogue linealmost as fast as across an ISDN line. But do these connections offer exactlythe same features? To enable the highest possible data speed to beachieved on an analogue line, a number of conditions have be satisfied. Forinstance, the user has to be connected to an all -digital (System -X) local tele-phone exchange. Such an exchange always leaves a small part of the clocksignal on the line. The new modems use this 'residue' to synchronise. Apoint which is often forgotten in discussions about 56-kbit modem technol-ogy is that the fast connection is only one-way: from an ISDN connection(i.e., the digital exchange) to an analogue connection. Consequently, twousers, each having an analogue connection, will never be able to realise a56 kbitls link between them. However, Internet providers in particular willwelcome the new technology, as it enables them to offer a fast connectionto customers having analogue modems.

In addition to these standards, a num-ber of other modes have been devel-oped:

2 x 64 klaWs unrestricted;-;- 384 kbitls unrestricted;-7. 1,920 kbitls unrestricted;

Packet mode via the B channel;Packet mode via the D channel.

TEL ESERVICESThe teleservices indicate the purposefor which a link will be used, therebyallowing a feature called end -to -end sig-nalling. The system enables, forinstance, a Group -4 fax machine to bereached directly on an ISDN numberwhich also has a telephone set and aPC with an ISDN connection. Thesefeatures are automatically added to thedatastream by the equipment or theapplication. Within the Euro ISDN sys-tem, a communication provider maydecide to implement the followingteleservices:.c? Voice 3.1 kHz

TeletextGroup -4 fax

o Mixed modec;) Videotext

In this way, the use of teleservicesprovides a high degree of flexibility toany single ISDN connection. In thenear future, further extension of theteleservices is feasible. Examples ofadded services include voice 7 kHz,message handling, video telephony,desktop/video confere_ncing, picturemail, film retrieval and audioretrieval. Some of these services arestill under construction, while othersare partly finished. Whether or notthey will be used in practice isdecided by the telecom providers.

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* long-distanceIrDA link

infrared data link covers up to 20 mThe infrared data link

discussed in this articleis based on the IrDA

(Infrared Data Associa-tion) standard, and is

suitable for any moderncomputer in combina-

tion with any peripheraldevice having an RS232

serial interface. Thelong-distance IrDA sys-tem goes even further,however. A full -duplex

mode operating at up to19.2 kbit/s coupled with

RTS/CTS handshakingenables links to be estab-lished which used require

cables. In contrast with thestandard IrDA specification

(range up to 3 m), dis-tances of up to 20 m may

be covered.

MAIN SPECIFICATION replaces serial cable connection by infrared suitable for all computers and peripherals range of over 20 m beam pointing not required with shorter links RS232 compatible IrDA 1.0 compliant (2.4-115.2 kbitis) no special driver(s) required choice between half -duplex and full -duplex

Design by P Hoppingand W. Hacklender

The subject of IrDA was cov-ered by two earlier articles,one on the basic of the sys-tem (Elektor Electronics, April1996) and one on a Win-dows 95 hosted IrDA trans-ceiver for the standardrange (Elektor Electronics,November 1996). The latterdesign (which was a first for homeconstruction) allows a half -duplex link

to be set up which runs at upS I to 115,200 bits/s. The typicaldistance covered by this sys-tem is about 1 m, or 3 m max-imum, while the transceivershave to be accurately pointedat one another because of theoptical aperture angle of 30'(±15').Like the add-on transceiverdesign published in theNovember 1996 issue, the1rDA interface typically found

in today's laptop and notebook com-puters complies with the IrDA stan-

dard. Thestandard ismarked bythe use ofshort pulseswhich enableIR LEDs(transmitting

devices) to beoperated at

high (pulsed)currents. The pulse length of the serialsignal on the RS232 interface, however,depends on the programmed bit rate,and is, therefore, variable. The IrDAinterface converts a serial bit with logicvalue '0' into a pulse with a minimumand maximum length of 1.6 its(default) or 3116th of the RS232 bitduration, respectively. To be able torecover the original bit length of theRS232 signal, the bit rate has to beknown, in other words, the IrDA inter-face has to be programmed to operateat the right bit rate.

Apart from the range that can be

A26 Elektor Electronics 5197

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Figure 1. Circuit dia-gram of the long-dis-tance IrDA interface. Amicrocontroller han-dles all bit rate set-tings, transmissioncontrol (full/halfduplex), as well aseverything to do withthe conversion of theRS232 signals intoIrDA-compliant 1.6-iispulses (and the otherway around).

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covered reliably, the IrDA standard isalso marked by restrictions as regardsdata security. Because the receiver con-verts each received IR pulse into a ser-ial bit, it is unable to detect the differ-ence between the odd noise pulse anda start bit of a serial byte representingthe value OFFh. Despite the use of anAGC (automatic gain control) in thereceiver, noise -induced bytes mayoccur if the optics are misaligned. Inpractice, however, few problems willoccur as long as the receiver is notpointed directly at a noise source (forexample, an electric bulb). A possiblyannoying factor, however, is the half -duplex nature of the link, which

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requires a certain recovery time to bebuilt into the transceiver to prevent thereceiver being overloaded by the localtransmitter

LONG-DISTANCE IRDAApart from the standard IrDA mode,the long-distance IrDA interface offersan extended mode which achieves bitrates of up to 19.2 bits's using RTS/CTShandshaking. As opposed to theextended (full -duplex) mode, the (half -duplex) standard mode is IrDA com-patible. There is only one deviationfrom the IrDA standard in that thetransmit power has been optimized forrelatively large distances (up to 20 m).

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IrDAgate T1

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receiver

0 SO 100 150 200

Figure 2. RS232 dataand the IrDA signal intransmit and receivemode. The shiftbetween the two sig-nals is caused by thelatching operation(byte -wise process-ing) of the UART inthe microcontroller.

Table 1. data rate settingbit rate SW4 ISW3 SW2 1SW1(bitsis) (1 = closea 0 = open)

1200 0 0 0 02400 0 0 0 1

4800 0 0 1 09600 0 0 1 1

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*) full duplex

The obvious advantage of the higherpower is that it is no longer necessaryto accurately point the receiver andtransmitter at each other if shorter dis-tances are covered, say, in an averagesized office.

The use of a special IrDA driverwith the standard -range transceiverdiscussed in last year's Novemberissue causes two restrictions: the inter-face is only suitable for Windows 95,and it can not be used with a periph-eral device such as a printer (unless, ofcourse, in the rare case of the printerhaving a built-in IrDA interface).Because of this, the present long-dis-tance IrDA interface does not employ

time [psi -0.250

970041. II

software -controlled bit rate settings. Infact, the bit rate is set by means of DIPswitches as shown in Table 1.

WITH CONTROLLERA microcontroller is employed for gen-erating the bit rates, the conversion ofRS232 signals into IrDA pulses, and therecovering of RS232 signals from IrDApulses. An Atmel AT89C2051 single -chip microcontroller is used in the cir-cuit (Figure 1). This controller is com-patible with the industry standard80051 as regards internal architectureand instruction set, offering 2 kBytesof ROM, 128 bytes of RAM, a UARTand two timers. A particularly usefulfeature of the 890051 is that the ROM

implemented as anelectrically programmable and erasable

3

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In transmit mode, the controllersupplies a 1.6-ps pulse for each 0 -bitreceived from the RS232 interface viathe MAX232 level converter. Alterna-tively, several 1.6-ps pulses may besupplied because the 'dead' (recovery)time is filled with pulses. In receivemode, the controller has to detect theoccurrence of an infrared pulse withina certain period. If such a pulse arrives,the value of the bit is '0', else, it is '1'.The basic IrDA system timing is illus-trated in Figure 2.

The 1.6-ps pulses supplied by pin 8in transmit mode drive the gate of Tl,an n -channel 5 -volt logic -level com-patible MOM -EL The FU T' switches thepulse current through the special IRtransmitter LEDs, with double limitingof the maximum current. On the onehand, the 3.9-0 resistors (R1 -R13) limitthe peak current through the series -connected transmit diodes to about1.5 A. This amount of current is onlyallowed, however, if the pulse/pauseratio (duty factor) is smaller than 0.01.1Vith higher bit rates, the duty factorrises with the number of pulses persecond, enabling resistor R9 to provideadditional current limitin:z. A, a mat -

Figure 3. Block dia-gram of the IrDAreceiver IC type SIR2from Novalog Inc. This

all the necessary com-ponents (preamplifier,filter, pulse shaper).

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(Analog)

150NA ,s1.714j OUTPUTDRIVER

Flash EPROM, so that the controllermay be erased and reprogrammedwithout having to expose it to UVlight. Another advantage is that theAtmel controllers are so cheap thatthey may also replace OTPs (one-timeprogrammable PROM memories).Finally, the Atmel 89C controllers arepretty fast, too - here, the CPU oper-ates at a dock speed of 22.118 MHz.

D7 D6 D5 D4 D3 D2 D1 DO

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OUTPUT

?7.41-13

ter of course, the high peak currentsthrough the LEDs call for suitablydimensioned copper tracks on the cir-cuit board.

For short pulses, reservoir capaci-tors C10 -C13 and C22 act as voltagesources with a low internal resistance.The eight high -power IR-LEDs typeTSHA6203 (from Temic) are speciallydesigned for long-range digital

Figure 4. Structure of the control byte,which Is continuously bounced back 'PI

and forth between two long-distanceIrDA boards.


COMPONENTS LIST

Resistors:R1 = 100k0R2,R4 = 1000R3 = 2700R5 -R8 = 309R9 = 330 1W

Capacitors:C1.C2 = 22pFC3 = 2r/F2 10V radialC4,C6,C7.C8 = 100nFC5 = 10OnF MKTC9,C20 = 100uF 10V radialC10-C13,C19 = 100/iF 25V radialC14-C18,C21 = 101/F 63V radialC22 = 470tiF 25V radialInductors:L1.L2 = 2 -hole ferrite bead, 0.4mm

CuL wire, see text

Semiconductors:D1 = BPV23NFL (Te.mic) or

SFH2O3FA (Siemens)D2 = LED. red, high efficiencyD3 -D10 = TSHA6203 or TSHA5203

Temic) OR diode. 12'. 875nm)D11 = 1N4001Ti = BUK552 (Philips Semiconduc-tors)

IC1 = AT89C2051-24PC (pro-grammed, order code 976504-1,,

IC3 = MAX232ECPEIC4 = 7805IC5 = 7812IC6 = 74HCT123IC2 = SIR2 (Novalog)-

Miscellaneous:X1 = 22.1184MHz quartz crystalS1 = 4 -way DIP switchK1 = 9 -way sub -D socket, angled

pins, PCB mountK2 = mains adapter socketEnclosure: approx. size

120x70x3OmmPCB and programmed 89C2051:

order code 970041-C. Available from C -I Electronicsfax (-31) 10 4861592

infrared transmission systems, highpulse loading capacity and short turn -on times. The rise and fall times, forexample, are just 300 ns at a pulsedcurrent of 1.5 A. Another equallyimportant aspect is, of course, that theradiation wavelength of 875 nmmatches the spectral sensitivity of thep-i-n photodiode, D1, employed in thereceiver circuit.

Apart from the IR transmitterdiodes, the MOSFET also drives a reg-ular red LED, D2. This LED is usefulas a visual transmit indicator. In full -duplex mode, the LED lights brightly,

5

Figure 5. Track layoutand componentmounting plan of thePCB designed for theinterface. Board avail-able ready-madethrough the Publish-ers' Readers Services.

indicating a properly operatinginfrared link. If there is no communi-cation, the LED lights only dimly.

The IR receiver section consists ofone, special, IC in combination withthe IR receiver diode. The special IC isa type SIR2 IrDA receiver from Nova -log. This chip is IrDA-1.0 compliant,i.e., it is capable of handling data ratesbetween 2.4 and 115.2 basis. As indi-cated by the block diagram in Figure 3,this one -chip IR receiver contains asensitive preamplifier stage, a com-parator for pulse shaping, and an out-put driver. The IR photodiode is

directly connected to the IC input,with a 100-nF capacitor, C7, decou-pling the cathode to ground. The sup-ply voltage for the receiver IC isdecoupled with the aid of R2, C8 andC9. The received IrDA pulses are avail-able with TTL compatible swing at thebuffered output. The microcontroller,IC1, handles their processing. The out-put of the receiver chip, pin 5, is con-nected to the P3.3 (INT1 interrupt) lineof the microcontroller.

In addition to a microcontroller, anIR receiver and an RS232 converter, thelong-distance IrDA circuit also containsa type 74HCT123 monostable multivi-brator, IC6A. In full -duplex mode, thisIC generates an interrupt when theinfrared link fails.

The circuit is powered by an ordi-nary mains adaptor with a rating ofabout 12 V/0.3 A. The adaptor is con-nected to the circuit via socket K2. Thereverse polarity protection, D11, is fol-lowed by an L -C filter, Ll-C19, which

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In principle, an RS232 link consists of three wire pairs. Asfar as differences exist between pin numbers on 9 -way sub -D and 25 -way sub -D connectors, the numbers in brack-ets apply to the older 25 -way version (also in the drawings).

data: RxD and TxD at pin 2 or 3 (3 or 2) handshake 1: RTS and CTS at pin 4 or 5 (7 or 8) handshake 2: DSR, DCD and DTR at pin 6, 8 or 20

(6, 1 or 4)

The RS232 interface appears in so many versions that anew link may not always function spot-on. If DOS reports

a write error to a COM port, the most likely causeis a fault in the handshaking system. This may beresolved as follows.Of each of the wire pairs mentioned above, onewire is an input, and the other, an output. It seemslogical to always have an input (for example, at thecomputer side) connected to an output (for exam-ple, at the printer side). If the relevant wires arecrossed, then outputs and inputs are intercon-nected, which makes no sense. If you are hesitantabout soldering inside the relevant plug, or evenunable to do so (for example, because of amoulded plug case), then an insertion -type adaptermay be employed to correct the situation with thecrossed wires. An output is easily identified usinga multimeter, because it normally supplies a neg-ative or a positive voltage of 10 V or thereabouts(usually, the range is 8 to 11 volts). Inputs, on theother hand, are usually at 0 V. or a low voltage(smaller than 2 V).So, in case of problems, take a deep breath andcheerfully start measuring potentials on the serialports of the PC and the peripheral device. If, forexample. a voltage of -10 V is measured on pin 2at both sides of the link, an insertion adapter hasto be made (in the simplest case, two sub -D con-nectors fitted back-to-back with short wires

between the pins). Pin 2 is then crossed over to pin 3, andpin 3, to pin 2. If, on the other hand, pin 2 is at - 10 V atone side, and at 0.9 Vat the other side, pin 2 may be con-nected to pin 2, and pin 3, to pin 3.The same procedure applies to the other wire pairs, andthe RS232 link will almost certainly function if everything isproperly measured and connected. Do not forget to con-nect pin 7 (5) to pin 7 (5) to establish the indispensableground link. The drawing shows all four variants which existfor RS232 serial links. The long-range IrDA board has a9 -way socket with a standard DTE-DCE pinout

suppresses noise. All ICs receive their5-V supply voltage from voltage reg-ulator IC4. The LEDs, on the otherhand, are powered by IC5, operatingat 12 V.

FULL DUPLEXIn full -duplex mode, the transmitterand receiver 'bounce' a control byteback and forth all the time. In this 'dia-logue', the actual information isinserted between the control bytes.Figure 4 shows the contents of thecontrol byte, which may be any bitpattern, as long as it is dissimilar fromthe occasionally occurring noisepulses. Only bits 0 and 1 have an addi-tional function:

When DO (data) is at '1', the trans-mitter informs the receiver that the

_control byte will be followed by a databyte. If the data bit is at '0', no data fol-low, and the circuit is switched toreceiving.

Bit D1 (CTS) is set to the valuewhich exists at the CTS input of theRS232 interface. The receiver then sup-plies this value at the RTS output.

Because only a part of the trans-mission time is actually used for databytes, the transmitter and receiverinternally operate at a bit rate which is6 to 8 times higher than the speed ofthe data conveyed over the IR link. Forexample, if the speed of the infraredlink is set to 192 kbitis, an internal bitrate of 115.2 kbit/s is used. In full -duplex mode, this creates the follow-ing constantly repeating sequence:1. Transmit control byte. Set bit DO ifthe RS232 interface has serial dataavailable for transmission;2. If data are ready and available,transmit them, else continue at step 3;3. Wait for control byte;4. Process control byte. Copy value ofbit Dl to RTS. If bit DO is at '0', returnto step 1, else continue with step 5;5. Receive data byte and output it viathe R5232 interface. Return to step 1.

As you can easily see, the two IR trans-ceivers wait at step 3 when the link isinterrupted. In that case, the mono -stable causes a restart after some time.Because of the maximum data speed

of 115.2 kbit/s, it was necessary to opti-mize the entire program by having theCPU count clock cycles. The eight bitsthat form a byte are thereforeprocessed linearly rather than in a loopstructure.

Because the full -duplex mode isasynchronous in a number of respects,the setting of the serial port shouldinclude the parameter '2 stop bits'. Par-ticularly at lower bit rates, when thecomputer comes very dose to the the-oretically possible data transmissionspeed, small delays could add up andcause data loss under certain condi-tions.

CONSTRUCTION AND TESTThere is a choice between two com-ponent types which may be used inthe transmitter, and the same goes forthe receiver: T5HA6203 or ISHA5203for the IR LEDs (both from Temic),and SFH2O3F (Siemens, Farnell) orBPV23NFL (Temic) for the receiverdiode. The SFH2O3F has the samecase as the LEDs, which makes it eas-ier to fit.


Start the population of the board(Figure 5) with the passive parts andthe IC sockets. The ICs, includingare not fitted yet. Check the value ofR9 to make sure the LEDs work in thesafe operating area. The IR LEDs mustbe fitted the right way around! Thecathode terminal is at the flat side ofthe enclosure. Next, connect the 12-Vmains adapter, and use a DMM tocheck the voltages at the regulator out-puts (5 V on C20, 12 V on C21). If the12-V supply is too low, temporarily tiethe gate of T1 to ground. The LEDsthen stop drawing current, and thesupply voltage should be at 12 V.

Remove the ground connection. LIEDD2 should light brightly, and R9should drop about 8 V. If everything isall right so far, the supply may beswitched off, the ICs inserted in theirsockets, and IC2 soldered in place. Ifthe supply is connected again, D2should light up briefly, and then verydimly. Using an oscilloscope, you mayexamine the processor's oscillator sig-nal at pins 4 and 5, and the transmit-ter pulses at the 1R diodes (or at thegate of T1). In half -duplex mode at9,600 bits/s, the scope should indicatesix 1.6-ps pulses, the first four spacedat about 9ps, and the last two, at about17 cis. This pulse train is repeatedevery 3.5 ms, which corresponds withthe period of the monostable.

As soon as a second, fully opera-tional, long-distance IrDA board comesin range, the two units will start tocommunicate, even if an RS232 linkhas not been set up yet with a com-puter or a peripheral. In this activestate, the current consumption of aboard is just over 100 mA. If no com-munication is established, then at leastone of the two boards is not function-ing properly. Try to establish the pres-ence of received pulses at pin 7 of themicrocontroller (connected to the out-put of the IR receiver, IC2). When theother board has no supply voltage,pin 7 will supply the six pulses sent by

Figure 6. Finished andoperational prototype.Two of these boardsare required for anIrDA link between twodevices having a ser-ial interface.

the local transmitter Once the otherboard is powered up, additional pulses(those from the receiver) shouldappear on the scope. This test isrepeated with the other unit as theboard on test In this way, you are ableto find out if a board transmits andreceives, as well as which board isdoing so.

Inductors LI and -12 consist of afew turns of enamelled copper wirewith a diameter of about 0.4 mm(SWG28) through a small ferrite beadwith two holes. These inductors act as

RF chokes, and their actual inductanceis uncritical.

Because capacitors C10 throughC13 and C22 are fairly heavily loadedby pulse -shaped current, it is recom-mended to employ special versions asfound in switch -mode power supplies.These capacitors are marked by a lowinternal resistance, and betterendurance under heavy loading con-ditions. Because suitable types like the2.5V101MA31 from RSH are rare birdsand by no means commonly available,'normal' electrolytic capacitors mayalso be used, provided they are fromreputable manufacturers, and knownto be suitable for use in switch -modepower supplies.

APPLICATIONConnecting -up is easy: the cable fromthe RS232 interface on the computer orthe peripheral device is connected tothe RS232 socket on the long-distanceIrDA board. So, one board may be con-nected to your PC's RS232 port, andthe other board, to a printer. Obvi-ously, no wires or cables are connectedbetween the two IrDA boards, as theircommunication is by means of (invis-ible) light. With relatively short dis-tances, say, within an office, an indirectlink is possible, that is, walls and ceil-ings may be used to reflect the infraredbeams. As a matter of course, the

the system with non-alignedboards is more likely to be degradedby direct sunlight, incandescent bulblight and similar light sources, than inthe case of a line of sight path.

A line of sight path and accuratepointing of the optics are essential ifyou want to use the IrDA link to coverdistances of up to 20 m. Also, precau-tions should then be taken to ensurethat the IR beams are not interrupted,because that may cause transmissionerrors which are beyond correction.

An obvious condition for a seriallink between two IR boards is that theequipment at both sides operates prop-erly in combination with an RS232cable connection. The crucial point inconnecting the long-distance IrDAboards is the right connector layout andpinning. Unfortunately, differencesabound in this respect, so that it may benecessary in some cases to swap a cou-ple of wires before the RS232 connec-tion is up and running (see also the'RS232 troubleshooting' inset).

Komi)

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Surplus alwayswanted for cash!

LOW COST PC's -SPECIAL BUY'AT 286'

40Mb HD + 3Mb RamUMITED QUANTITY ene of tnese 12Mhz HI GRADE 286 systemsMade in the USA to an industrial specification. the system wasdesigned foe trof raliabety. The compact case houses the mother-board. PSU ane EGA video card with angle Sere 1.2 Mb floppy diskdrive & integral 40Mb hard disk drive to the front Real erne dockwith tattery backups provided as standard Sup -eked in gm -0 usedcord -tin ccmptete earn enhanced keyboard. 640k + 2Mb RAM.DOS 4.01 and 90 DAY Full Guarantee. Ready to Run rOrder as HIGRADE 286 envi £12 9. 00Optional Fitted extras: VGA gracees card1 4Mb 3W tioppy creek drive Instead of 12 Mb)Wordeerfect 6_0 for Dos - alien 3W FDO Wen orderedeE2i.lee Ethernet (thick. ten or twiste-d) netwerk cam

£29.00£19.95£22.50£29.00

LOW COST 486DX-33 SYSTEMLimited quantity of this 2nd user, superb sma9 size desktop unitFee/ fevered wee standard atom connectors 30 & 72 pit. Suppedveth keyboard. 4 Mb of RAM. SVGA monitor output. 256k cache andintegral 120 Mb IDE drive with single 1.44 Mb 3.5' floppy der( driveFr -Ley tested and gua,antaect Fogy er7..*andaVe oneMany other options amiable - call for details. £399.00

(E)

FLOPPY DISK DRIVES 3'h" - 8"51/2" or 31/2" from only .£18.95

Massive ciumtases of standard 5e and 3W dries enables us topresent prime product at industry beateg low pews! AS units (unlessstated) are BRAND NEW or removed from often brand new equeomem and are fully tested, aligned and steeped to you with a 90 daygearantea are operate tram standard voaages end are of standardsae. All are IBM-PC compatible 314' Reported on your PC).3W Panasonic JU36314 720K or equivalent RFE £24.95(B)355* Mitsubishi fe.F3.55C-L 1.4 Meg Laptops only £25.95(B)3W Mitsubishi PAF355C-D. 1.4 Meg. Non laptop £18.951B)SW Teac FD-55GFR 1.2 Meg (for IBM pis} RFE E18.95(B)SW Teac FD -55F -03-U 720K4:1130 (for BBC's etc) RFE £29.9518)SW BRAND NEW Mitsubishi MF501B 360K £22.951B)Table top case with integral PS1.1 for HH 5W Flopp or HD £29.95113)8" Shugart 800/801 8' S5 refurbished & tested £195.00(E)8" Shugart 810 8' SS HH Brand New £195.00(E)a- Shugart 851 8* double sided refurbiste & tested £250.00(E)Mitsubishi M2894-63 8' double sided NEW I275.00(E)Mitsubishi M2896 -63-02U 8' DS sernTrie NEW £2135.00(E)Dual 8' cased drives with integral power s;p:Iply 2M4) £499.00(E)

HARD DISK DRIVESEnd of line purchase scoop! Brand new NEC 02246 8' 85 Mbytedrive win industry standard SMD interlace, replaces Fujitsuequivalent more=. Fug manual. Only £299.00 or 2 for E525.00 (E)3,X' FUJI FK-309-e5 20mb MFM M1= RFE £59.95(C315" CONNER CP3e24 20 mb IDE I/F (or Kure )RFE 959.95(C)

CONNER CP3044 40mb IDE (or equiveRFE £69.00(CRODIIAEReene7S 45rrib SCSI OF (Mac & Acorn) £69.00)C

3' WESTERN DIGITAL 850mb IDE OF Brand New £185.00(C' . MINISCRIBE 3425 2Orrito M.FM VF (or equiv.) RFE £49.95(C)

5 .' SEAGATE ST -238R 30 mb RLL 11F Refurb £69.95(C)Ill i* CDC 94205-51 4Orrib HH META IfF RFE tested £69.95(C)

. HP 97540 850 Mb SCSI RFE tested £89.00C)5"i' HP C3010 2 Gbyte SCSI differential RFE tested £195.00(Ca' F1JJfTSU M2322K 160Mb SMD RFE testae £195.00(E)Ham disc controeers for MFM . IDE. SCSI. RLL etc. from £16.95

THE AMAZING TELEBOXConverts your colour monitor into a DUALITY COLOUR TV!!

TV SOUND &VIDEO TUNERCABLE COMP Al7BLE

The TELEBOX s an attractive lofty cased mans powered Lee me-taining all electronics ready to plug into a host of video mentorsmade by makers such as MICROVITEC. ATARI, SANYO, SONY,COMMODORE. PHIUPS, TATUNG, AMSTRAD etc The emcee:sevideo output wit also pig directly into most video recorders, Oatenreception of TV channels not normally receivable on most televi-sion receivers' (TELEBOX MB) Push button controls on the frontpanel allow reception of 8 fully tuneable 'off alt UHF colour telenstochannels. TELEBOX MB covers virtually al television frequenciesVHF and UHF including the HYPERBAND as used by most cableTV operators- A composite video output is treated on the rear paneltor desist connection to most makes of monitor or desktop computervideo systems For complete oempattiety even to monitors ye:h-e-et sound an integral 4 watt audio amplifier and law revel Hi Fiudo cutout are provided as standard.

TELEBOX ST for composite video input type monitors £36.95TELEBOX STL as ST but fitted with integral speaker £3950TELEBOX MB Mute:tend VHF/UHF/CablaHyperband tuner £69.95For overseas PAL versions stale 5.5 or 6 mHz sound specification.'Fir cable I hypertand reeepten Telebox MIB shou'd be connected:s a caSe Weser.- ce c:'7 cose Ts'at.cre's S IS)

DC POWER SUPPLIES

1C's -TRANSISTORS - DIODESOBSOLETE -SHORT SUPPLY -BULK

6,000,000 items EX STOCKFcr MAJOR SAVIVG5 - CALL FOR seteCoutiutTOTI Mauer

VIDEO MONITOR SPECIALSOne of the highest specification

Amonitors you will ever see -At this price - Don't miss it!!

Mitsubishi FA3415ERCL 14' SVGA Mullieync occur men/cc van feepeel tete acid resat:on of 1C24 x 71M. A

ers".ncurfrigi'd 11111.-1. r - VG.illf& SVGAmodes. BBC, COMMODORE fncierrg AmgaARCHIMF_DES zed APPLE Pee try'leaves Etched

=on eeireereed. Repled n EXCEL -T

e:` . sverd-ine arts LOWRADIATION MPR

LEN tee used corxicenTat & Sahel Base Et75 Only £119 et?rteSf,.1AVGA ratle for IBM PC included.Enerrai cables for other types of computers CALL

As New - Used on film set for 1 week only!!15' 0.28 SVGA 1024 x 768 res. colour monitors.

Swivel & tilt etc. Full 90 day guarantee. £145.00 (El

Just in - Microvitec 20' VGA (800 x 600 res.) colour monitors.Good SH condition - from £299 - CALL for Info

PHIUPS HCS35 (same style as CM.8833) attractively styled 14'=lour monitor with both RGB and standard composite 15.625Khz video Inputs via SCANT socket and separate phono jacks.Integral atan power amp and speaker for all audio visual uses.Witt connect direct to Amiga and Mad BBC computers. Ideal for allvideo monitoring / security applications with direct connectionto most colour camerae High quaky with many features Rich asfront concealed flap controls. VCR correction button etc_ Gooduses oenezien - fully tested - guaranteed only EQRDimensionsV/14'x Hine )(1St.' D.PHIUPS HCS31 Ultra compact 9' colour video Monde: with stan-dard composite 15.625 Khz video input via SCANT socket Idealfor at mon-torina I security appIcatiens. High quality, ex-equiprientfully tested & guaranteed (posseee minor screen burns). In atuarefn.* square tee< pastic case measuring W10' x H10' x 13ee D.240 V AC mans pewered. Only £79.00 (0)KME 10' 15M10009 high definition tabu/ monitors Wei 0.25' dotpitch. Superb clarity and modem styling._Operates from any 15.625 khz sync RGB videosource. with RGB analog and composite syncsuch as Atari, Commodore Amiga. AcornArchrnedes & BBC. Measures only 13W a 12' xla.' G°c4 v5e1:1 ca'cLlicn Only £125 (E)

20" 22" and 26" AV SPECIALSSuperbly made UK manufacture. PIL. all sold state colour monitors,compete with compite video & optional sound input Attractiveteak style case. Perfect far Scheele, c Deco. CMrbs, eternEXCELLENT tittle used condten with full 90 day guarantee.

20"....£135 22"....£155 26"....£185(9

SPECIAL INTEREST ITEMSFA3445ETKL 14' Industrial spec SVGA monitors £245

2kW to 400 kV/ - 403Hz 3 phase power sources - ex stock £POAIBM 8230 Tyw 1, Token ring base taut diner £950IBM 53F5501 Token Reg ICS 20 port lobe modules £750IBM MAU Token ring distribution panel 8228-23-5050N £95AIM 501 Low castortion Oscelatore 9Hz to 330101z. IEEE £550Trend OSA 274 Data Analyser with G703(2M) 64 Le £POAMarconi 6310 Programmable 2 to 22 GHz sweep, generator £6500HP16508 Logic Analyser £3750HP3781A Pattern generator & HP3782A Error Detector £POAHP APOLLO RX700 system units £950HP6621A Dual Programmable GPIB PSU 0-7 V 160 wane £1800HP3081A Ineesuie. workstation eve Bar ode swipe reader £175HP6264 Rack mount variable 0-20V S 20A metered PSU £675HP54121A DC to 22 GHz tour channel lea set £POAHP7580A AI 8 pen HPGL feet+ spend drum plotter £1850EG+G Brookdeal 95035C Precision lock in amp £650View Eng_ Mod 1200 computerised tweeter+ system £POAUng Dynamics SkV/ programmable vibration test system £POAComputer controlled 1056 x 593 mm X Y table & coritrocer £1425

£POA£3750£9500£POA£2200£1200£1150£1450

Kerthley 590 CV capacitor /voltage analyserRacal ICR40 dual 40 channel voice recorder systemFiskers 45KVA 3 ph On Line UPS - New tans DEC 1935ICI R5030UV34 Caanfne ultrasonic eteenng systemMann Tally MT645 High opecd tine printerIntel S BC 486/133SE Multbus 466 system 8l.tb RamZeta 3220-05 A0 4 pen HPGL fad drum plottersNikon HFX-11 (Eprieeot) exposure control unitMotorola VME Bus Boards & Components List. SAE CALL £POATrio 0-18 vdc linear, metered 30 amp loran PSU. New £550Fujitsu M3041R ECO LPM band printer £1950Fujitsu M304113 6C0 LPM printer yeah network interface £1250Perkin Elmer 2e98 Infrared sceeerereceeetet £POAVG Electronics 1035 TELETEX-7 17 ...a mei Meter £3750Andrews LARGE 3.1 m Sate 7, - . . : For iceeore) £950Sekonlc SD 150H 18 channel c - al reorder £1995TAYLOR HOBSON Tallystat a - 7 i -e- £750

19" RACK CABINETSSuperb quality 6 foot 40U

Virtually New, Ultra Smart" Less than Half Price!

Tcp quality 19' rat caeriets rnaW n UK byOptima Enclosures Ltd. Units featurereegner, smoked acrylic kickable front door.full height lockable half louvered back doorand louvered removable side panels. Fullyarleatabe internal fierg struts, ready punchedfor any configuration of equipment mountngpies ready mounted integral 12 way 13 ampsodat switched mans datribution step makethew racks some of the most versatile we

have ever sold. Racks may be stacked sea try side are teeraforerequire only two side panels to stand singly er in multiple bays-

Overall reneriskets are: 77W H x 3214* D x W. Order as:OPT Rack 1 Complete with removable she panels_ £335.00 (G)OPT Rack 2 Rack. Less sde pa es £225.00 (G)

32U - High Quality - All steel RakCabMade. by Eurocrat Enclosures Ltd to the highest possible spec,rack features all steel construction with removableado, free are tack dots- Front and back doors are oee.hinged for easy access and an are lockable withfive secure 5 lever barrel locks_ The front dooris constructed of double walled steel with a 'designer style' smoked acrylic front panel to . eee 'enable status indicators to be seen through the'panel, yet remain unobtrusive. Internally the rack Ifeatures fully slotted reinforced vertical fixing members to take the heaviest of 19" rackequipment. The two movable vertical fixing struts j(extras available) are pre punched for standard'cage nuts'. A mains distribution panel :ly mounted tot a bottom rear, provides 8 x IEC 3pat Euro sockets and 1 x 13 amp 3 en switchedutility socket. Overall ventilation is provided byfully louvered back door and double ski nod top sectionwith top and side louvres_ The top panel may be renewed for fetingof integral fans to the sub plate etc. Other features include: finedmeters and floor levelers, prepunaied utility panel at brew rear forcable / connector access etc. Supplied it excellent, slightly usedcondition with keys. Colour Royal blue External dimensionsmmeiE25H x 635D x 603 W ( EA' H 25' D x'W)

Sold at LESS than a third of makers price

A superb buy at only E195.00 (G)

Over 1000 racks - 19" 22" & 24" wide3 to 44 U high. Available from stock !!

Call with your requirements.

TOUCH SCREEN SYSTEMTne inmate in 'Touch Screen Technology' made by the experts -AlleroTouch - but said at a price below cost It System consists ofa fiat translucent glass laminated panel measuring 29.5 x 235 eeconnected to an electronic conuceer PCB. The controller producesa standard metal RS232 or TTL output which continuously givessnipe serial data containing positional X & Y co-cmteates as to*here a finger is Leeching the panel - as the fnger moves. the datainstantly charges. The X & Y information is green at an incrediblematrix resolution of 1024 x 1024 positrons over the entire screensize A host of available translation software enables dirt e:n-nection to a PC for a myriad C applications inclurfria: control pan-els. pointing devices. POS systems. contrreers for tSe disabled orcomputer un-trained etc etc. Imagine using your linger withWirKSOWS.. OSICALI of a mouse !I (a drier is indeed available. Theapplications for this amazing product are only limited by yourimagination!! Complete system irioludng Controller, Power Supplyand Data suppled at an increlbse price of relyerr INCROTOUCH software support pact £145.00 (R)and camels rurlBYcceaswiftas PC's C29.95 RFE- Tested

LOW COST RAM & CPU'SINTEL 'ABOVE' Memory Expansion Board. Full length PC -XTand PC -AT compatible card with 2 Mbytes of memc-ry on boardCard is fully selectable for Expanded of Extended (2116 processorarid above) memory. Full data and driver disks supplied. RFEFully tested and gearanteed. Windows compatble. £59.95(A1)Half length 8 bit memory upgrade cards for PC AT XT expandsmemory either 256k or 512k in 64k steps. May also be used to MItri RAM above 640k DOS frnit Carepetee with data.Order as: XT RAM UG. 256k. £34.95 or512k £39.95 (At)

SIMM SPECIALS1 MB x 9 SIMM 9 drip 120rts Only £16.50 Al)(1 MB x 9 SIMM 3 dip so rts £19.50 or 7Ons £22.95 Al)1 MB x 9 SIMM 9 chip 5Ons £21.50 or 7171s £23.75 Al)4 MB 70 ns 72 pin SIMM -with parity- Only £95.00 (Al)INTEL 486-DX33 CPU £55.00 INTEL 486-0X66 CPU £69.00 tat)Full RANGE OF CO -PROCESSORS EX STOCK -CALL FOR DM

FANS & BLOWERSEPSON 130412 4ex40x20 trim 12v DC £7.95 10 / E65PAPST TYPE 612 60x60a5 mm 12v DC £8.95 10/£75MITSUBISHI MMF-1361312DLerweree5 mm 12v DC £4.95 10 / £42MITSUBISHI MM F -08C1 2DM 50x50125 mm 12v DC £5.25 10 / £49MITSUBISHI MMF-0913120H 92192x2.5 mm 12v DC £5.95 10 / £53PANCAKE 12-3.5 92x92x18 mm 12v DC £7.95 10 / £69

Virtually every type of power System Video 1152 PAL Wee El.-, men £485 EX -EQUIP AC tans:ALL TESTED 120 x 120 x 38 mm speely 110supply you can imagine .Over Test Lab - 2 mu square queesee oe-iiiste test cabriets e300 or 240 v £6.95. 80 x 80 x 38 mm specify 110 or 240 v £5.95

10.000 Power Supplies Ex Stock Kenwood 9601 PAL Vecuxscope - NEW £650 IMHOF 826 1900 race mnt 3U x Blower 1 10a40v NEW £79.95Call for info/ list. Please call for further details on the above items Srkpp-ng on all fans (A). &3om-5 (B). 50,000 Fans Ex Stock CALL

Issue 13 of 'Display News now available - send large SAE - PACKED with bargains!

-ELECTRONICS-

ALL MAIL & OFFICESOpen Mon -Fri 9.00-5:30Dept EK. 32 Biggin Way

Upper NorwoodLONDON SE19 3XF

LONDON SHOPOpen Mon - Sat 9:00 - 5:30

215 Whitehorse LaneSouth NorwoodOn 65A Bus Route

tt.Tiorntari Heath aSaParrat Park SR Rail Stations

DISTEL©The Original

FREE On line DatabaseInfo CO 20.000+ stock baneRETURNING SOON !

ALL a ENQUIRIES

0181 679 4414FAX 0181 679 1927

EST

25

Al races b- fir: Mai p...scrrE tat VAT to TOTAL ceder e-reket. ode £10. Ede Fee a=urr cre-es aoccetral tern Gee.emeart Se-cce.Urea-stes and L ates - mierrum exctrz orcna £5:1 Crecees met £100 we seeee to 10 eating days de err Care charges Okly.E4.C4.13;-£550. ;Cl-(R 5"n ai412.03, (Fret 500. (F113_00. (GALL Aloe wpm( 6 days for stEpprg - beer CALL Sootaxt sercharge CALL Al goods Reelect to cerSaetard Ca-eters ci Sa'e end tri.s staled giaeree..1 far 93 days AI peeerwes en a Teem to base bees Al titres re.w.so m Yam prixs specftsions winott peesretire Crews Reed It exie Crect-res tor ireere. Tqo CA -41 pices pert ler SSpitA TC&r_ AI Marla -raid et aceereheegad CiDepay 19EO E & 0 E. 05e

SURVEILLANCEPRonssioNAL 01 JA LEIN KITS

No. I for Kits'Whether your requirement for surveillance equipment is amateur. professional or you are just fascinated by this unique area ofelectronics SUMA DESIGNS has a kit to fit the bill. We have been designing electronic surveillance equipment for over 12 yearsand you can be sure that all our kits are very well tried, tested and proven and come complete with full instructions, circuitdiagrams, assembly details and all high quality components including fibreglass PCB. Unless otherwise stated all transmittersare tuneable and can be received on an ordinary VHF FM radio.

Genuine SUMA kits available only direct from Suma Designs. Beware inferior imitations!UTX Ultra-mlnlature Room TransmitterSmallest room transmitter kit in the word! Incredible 10mm x 20mm including mic.3-12V operation. 500m range 116.45

MTX Micreminlature Room TransmitterBest-selling micro -miniature Room TransmitterJust 17mm x 17mm includine m',.; 3-12V operation. 1000m range ........._._..C13.45

SIX HIghperlormance Room TransmitterHi performance transmitter with a buttered output stage for greater stability and range.Measures 22mm x 22mm including mic. 6-12V operation. 1500m range £15.45

VT500 HIghpower Room TransmitterPowerful 250mW output providing excellent range and performance. Size 20mm x40mm. 9-12V operation. 3000m range £16.45

VXT Voice Activated TransmitterTriggers only when sounds are detected. Very low standby current. Variable sensitivityand deiay with LED indicator Size 20mm x 67mm. 9V operation. 1000m range_119.45

HYX400 Mains Powered Room TransmitterConnects directly to 240V AC supply for long-term monitoring. Size 30mm x 35mm.500m range...... £19.45

SC RX Sub cart I et Scrambled Room Transmitter

Scrarrineo output from this transmitter cannot be monitored without the SCDM decoderconnected to the receiver. Size 28rrim x 67mm. 9V operation. 1000m range £22.95SCLX Subcanler Telephone TransmitterConnects to telephone line anywhere, requires no batteries. Output scrambled sorequires SCDM connected to receiver. Size 32mm x 37mm. 1000m range...........£23.95

SCUM Murder Decoder Untt for SCRXConnects to receiver earphone socket and provides decoded audio output toheadphones. Size 32mm x 70mm. 9-12V operation £22.95

ATR2 Micro Sin Telephone Recording interlaceConnects between telephone line (anywhere) and cassette recorder. Switches tapeautomatically as phone is used. All conversations recorded. Size 16mm x 32mm.Powered from line £13.45

*** Specials ***DLTX/OLRX Radio Control SwitchRemote control anything around your home or garden, outside lights, alarms. pagingsystem etc. System consists of a small VHF transmitter wth digital encoder and receiverunit with decoder and relay output, momentary or alternate, 8 -way dil switches on bothboards set your own unique security code. TX size 45mm x 45mm. RX size 35mm x90mm. Both 9V operation. Range up to 200mComplete System (2 kits) £50.95Individual Transmitter DLTX ........ ..... ..... ..... .......... _119.95Individual ReCeiler DLRX.. .......... £37.95

Mi3X-1 Micro BroadcasterNot technically a sun eillance device but a great idea! Connects to the headphone outputof your Hi -F. tape or CD and transmits Hi-Fi quality to a nearby radio. Listen to yourfavourite music anywhere around the house, garden, in the bath or in the garage andyou don't nave to put up with the DJ's choice and boring waffle. Size 27mm x 60mm.9V operation. 250m range

UTLX Ultra-minlature Telephone TransmitterSmallest telephone transmitter kit available. Incredible size of lOmm x 20mm!Connects to line (anywhere) and switches on and off with phone use.All conversation transmitted. Powered from line. 500m range._ .....................£15.95

TLX700 Microinisiature Telephone TransmitterBest-selling telephone transmitter. Being 20mm x 20mm it is easier to assemble thanUTLX. Connects to line (anywhere) and switches on and off with phone use. Allconversations transmitted. Powered from line. 1000m range._ 113.45STU( HI ghee °Hartmann° Telephone TransmitterHigh performance transmitter with buffered output stage providing excellent stabilityand performance. Connects to line (anywhere) and switches on and off with phone useAll conversations transmitted. Powered from line. Size 22mm x 22mm.1500m range £16.45

TKX1100 Signalling/Tracking TransmitterTransmits a continous stream of audio pulses with variable tone and rate. Ideal forsignalling or tracking purposes. High power output giving range up to 3000m. Size25mm x 63mm. 9V operation ..E22.95

CD400 Pocket Bug Detector/LocatorLED and piezo bleeper pulse slowly, rate of pulse and pitch of tome increase as youapproach signal. Gain control allows pinpointing of source. Size 45mm x 54mm 9Voperation £30.95

£0600 Professional Bug Detector/LocatorMulticolour readout of signal strength with variable rate bleeper and variable sensitivityused to detect and locate hidden transmitters. Switch to AUDIO CONFORM mode todistinguish between localised bug transmission and normal legitimate signals such aspagers. cellular, taxis etc. Size 70mm x 100mm. 9V operation 00.95OTX180 Crystal Controlled Room TransmitterNarrow band FM transmitter for the ultimate in privacy. Operates on 180 MHz andrequires the use of a scanner receiver or our CIRX180 kit (see catlogue). Size 20mm x67mm. 9V operation. 1000m rang ........ £4015

11111130 Crystal Cointrolled Telephone TransmitterAs per QTX160 but connects to telephone line to monitor both sides of conversations20mm x 67mm 9V operation. 1030m range... £40.95

4SX180 Line Powered Crystal Controlled Phone TransmitterAs per OLX180 but draws power requirements from line. No batteries required. Size32mm x 37mm Range 500m

QIU(1110 Crystal Controlled FM ReceiverFor monitoring any of the '0' range transmitters. High sensitivity unit. All RE sectionsupplied as a pre -built and aligned module ready to connect on board so no difficultysetting up. Outpt to headphones. 60mm x 75mm. 9V operation £60.95

A build-up service is available on all our kits it required.UK customers please send cheques, POs or registered cash. Please addE. 2.00 per order for P&P. Goods despatched ASAP allowing for chequeclearance. Overseas customers send sterling bank draft and add £5.00 perorder for shipment. Credit card orders welcomed on 0827 714476.

OUR LATEST CATALOGUE CONTAINING MANY MORE NEWSURVEILLANCE KITS NOW AVAILABLE. SEND TWO FIRSTCLASS STAMPS OR OVERSEAS SEND TWO IRCS.

SUNIADESIGNS

DEPT. EETHE WORKSHOPS, 95 MAIN ROAD,

BAXTERLEY. NEAR ATHERSTONE,WARWICKSHIRE CV9 2 LE

VISITORS STRICTLY BY APPOINTMENT ONLY

Tel: 01827 714476Fax: 01827 714476


advanced LCR meterPart 2: Construction

The design consider-ations and the circuit

layout of the LCRmeter were described

in last month's firstpart of this three-part

article. This secondpart describes the

construction of theinstrument. Because

of the required preci-sion, ample screening

is needed, but withsome dexterity the

construction willprove to be not too

demanding. The care-ful work will be

rewarded by aninstrument with excel-

lent properties.

Design by H. Bonekamp

Because of the use of integrated com-ponents, the number of buildingblock constituting the LCR meter hasbeen kept small, as may be seen in theintroductory photograph showing theinstrument with upper half removed.

Since small signals and well-defined parasitic impedances are used,good screening is required in severalplaces. The resulting tin-plate screensform an important part of the con-struction. Note that any deviationsfrom the described screening mayadversely affect the performance ofthe instrument.

The printed -circuit board, the vari-ous screens and the front panel are alldesigned for use with the specifiedenclosure.

The instrument should be built onthe double -sided, through -platedprinted -circuit board shown in Fig-ure 5. Start the construction by cutting

the switch (51-S3) section and a littleextra from the main board. The extrapiece of board removed makes spacefor the liquid -crystal display (LCD) thatwill be fitted to the inside front panel.When the section has been cut out,hold the main board in the enclosureto see that it fits. Note that the six ven-tilation slots are at the rear of the enclo-sure, where later the mains inlet andon/off switch will be located.

Of the various tapped bosses in thebottom half of the enclosure only fiveare to be retained: four to screw theboard to and one coinciding with thespace Ieft by the extra piece of cut-outboard. The superfluous bosses are eas-ily removed with a sharp knife or a 10 -mm drill. When this is done, try theboard for a correct fit again.

Gouge out a little material from thebottom panel of the lower half of theenclosure underneath PC4 (to make


Parts list5a

Resistors.R1. R,8. R22 -R18. R3,3 = 10 kitR2 -R5 = 10 ka 1%. high stabilityR6, R19 = 100 ftR7 = 100 kit, 0.1%, high stability138 = 100 a 0.1%. high stabilityR9 = 4.7 kitR10 = 1012

= 1 kit. 1%. high stabilityR17 = 5.49 kitR26 ---- 18 ICUR21 = 1212R29 = 22R31 = 1.5 itP1 = 10 kit preset, horizontal mount-

ing

Capacitors:C1 = 56 pFC2 = 65 pF trimmerC3. C5, C18 = 10 pF, 10 V, radialC4. C10, C15. C20. C22. C24, C28, C29,

C31 -C40, C.13-054 = 100 nF, highstability

C6, C7 = 1 pF*C8, C9 = 1 nF*

= 470 nF-C12, C13 = 200 nF*C14 = 47 nF'C16, C17 = 22 pF. ceramicC19 = 150 pF. ceramicC21 = 2200 pF, 16 V. radialC23, C25 = 1000 pF, 35 V. radialC26 = 300 nF'C27, C. C41, C42 = 10 pF. 16 V,

radial = MKT (metallized polyester)

Semiconductors:DI. De D7 = 1N414802, 03 = 8AV4504, D5, De = BAT85D9 --D12 = 1N4001D13-1)16 = 1N4002D17 = zener. 5.6 V, 1.3 WDie, Di, = zener. 16 V. 1.3 W

= BC337

Integrated circuits:ICI = AD1847JPIC2 = AD847JNIC3, IC, = OP282GPICS = ADG433BNIC6 = AD620ANIC7 = PGA103P (Burr -Brown)IC6 = 27C512 (976507-see Readers

services toward the end of thisissue)

IC9 = ADSP2101 KP80IC10 = 22V10 (976506-see Readers

services toward the end of thisissue)

IC11 = ST93C46CB1 (SGS)1C12 = 7805IC13 = 7815IC/4 = 7915

Miscellaneous:L1 = inductor, 100 pHRef = relay, Siemens V23042 -A2001 -

B101S1 -S3= Push button switch 06 -R -RD

with protective cap MO -RD -CAP

Xi = crystal 24.576 MHzX2 = crystal, 10 MHzTr1 = Mains transformer. secondary

9 V. 4.5 VA (e.g., Velleman

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1090050M from h.laplin)Tr2 = Mains transformer, secondary

2x15 V. 1.5 VA (e.g., Velleman2150018M from Maplin)

PC1, PC2 = PCB mounting phonosocket, red

PC3. PC. = PCB mounting phonosocket, black or white

= 6 -pin mini DIN socketK2 = 20 -way PCB mounting box

header, straightK3 = 4 -pin single -row IC socketK.; = 2 -way PCB mounting terminal

block, pitch 7.5 mmHeat sink. 11 K Fischer

SK104/38.1 (Dau - phone 01243553 031)

LCD. L1642B1J000, 16x2 characters(Seiko)

Enclosure, UM32C-09L with 2 off FPK30018 (front and rear panel) and 1off UM -ASK (feet) (Bopla fromPhoenix Mecano. phone 01296 398855)

= fuse, 50 mA, slowS4 = double -pole mains onroff switchMains inlet with integral fuse holder20 -way Rateable about 15 cm longPCB+GAL+EPROM Order No.

970028-C or if board not required:GAL Order No. 976506 and EPROt.Order No. 976507

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space for the fixing screw of this com-ponent) and RI, and D19 (to makespace for the solder pads).

A screen is needed in the lower halfof the enclosure. This is made by cut-ting a strip of 0.5 mm thick tin-plateinto the shape shown in Figure 6. Notethat this must be the exact size speci-fied to prevent safety problems (themains voltage input to the transform-ers is present at the track side of theboard). Make the cuts for the small lip(bottom left-hand of Figure 6) and drillthe three specified holes in the tinplate. Bend the screen along the linesindicated and turn the cut-out lipslightly inwards. The screen shouldnow- fit neatly into the bottom half ofthe enclosure. Secure it in place witharaldite or superglue and fasten the lipon to the fifth tapped boss with a self -tapping (preferably nylon) screw.

SOLDERINGWhen the mechanical work has beencompleted, a start may be made withpopulating the board. Since the LCRmeter is not intended for beginners, it

Figure 5b. Track lay-out of the printed -cir-cuit board for the LCRmeter.

Figure 6. Template formaking the tin-platescreen for the lowerhalf of the enclosure.For safety reasons it isvital that the exactdimensions areobserved.

is assumed that you are well versed insoldering. Nevertheless, there aresome points which should be speciallynoted.

Sockets Pcl-Pc4 must be fastenedwith small self -tapping screws beforeany solder connections are made tothem.

The crystals must be fixed into posi-tion so that they float about 1 mmabove the board; this prevents any riskof their metal case causing a short-cir-cuit between adjacent tracks on theboard.

In a similar manner, but for a dif-ferent reason, regulators IC13 and IC14must, after their terminals have beenbent at right angles, be suspendedabove the board with the aid of 5 mmlong plastic or nylon round clearancespacers. This enhances their air cool-ing.

Test resistors R7 and R8 should befitted last on to the board. This isbecause the less they are exposed tomechanical stress and heating, the bet-ter their stability will remain.

--A-

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970028 - 2 - 11

All other components may be fittedin the usual way. It is advisable, butnot necessary, to use sockets for theICs.

Solder a 4 -pin section of a single -row IC socket to the section of boardfor switches S1 -S3. Before any solder-ing, cut the pins of the IC socket shortso that they do not protrude at thecomponent side of the board and donot touch S, when this is pressed. Fitthe switches with protective caps asspecified so that they do not interferewith one another when they arepressed.

Link terminals 17-20 of connectorK, to the switch -board via K3 and ter-minals 1-16 to the display via a10-15 cm long piece of 20 -way flat -cable.

In the specified Seiko display mod-ule, the terminals for the backlight areisolated from the data terminals (as,indeed, in most displays). Pin 16 of K,is connected to the earth terminal ofthe backlight and pin 15 to the supplyterminal. These terminals are normallyidentified by or C (for cathode) and- or A (for anode) respectively. Theremaining terminals (1-14) of K, arelinked to the corresponding terminalson the display.

Fit the display and the switch-board to the plastic front panel (Fig-ure 7). Use countersunk Nri screws for

Elektor Electronics 5,97 37

DIY Test AdaptorA four -wire test is conveniently carried out with the aid of the test adaptor shown in this box. The outer pins pro-vide the current through the component on test, while the inner pins are used to measure a voltage (drop). Witha little dexterity and suitable tools (4 -mm tap, a set of standard size steel drills and a metal saw), the adaptor iseasily made in a home workshop. It is made from two strips of brass, 10 mm long, 2 mm thick and a strip ofpolythene (or plastic or nylon).

The construction drawing shows that the inner pins are electrically linked to the lower brass strip, whereasthe outer pins are connected to the upper brass strip. The polythene strip

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functions as the carrier: a nylon M4 size screw ensures that the strips stayfirmly together.

When the three strips have been cut to size, clamp them in a vice(edge -ways in the jaws) and drill the five 3.2 mm holes right through. Removethe strips from the vice and tap the holes where indicated. Holes that neednot be tapped should be reamed or drilled out to 4 mm diameter.

Cut the thread of the inner pins to the requisite length and use themto fix the lower brass strip to the polythene strip. The remainder of the workis evident from the drawing.

Cut the nylon fixing screw at the centre to a length that allows a gapof not more than 2-4 mm between the two brass strips. Glue some thin feltpads between the brass strips where indicated.

The last operation is to fit an M4 -size nut in each of the solid polytheneknobs. Ream out the hole in the knob to such a depth that the nut just pro-trudes from the knob. This ensures good electrical contact between the brassstrip and the screw when this is tightened. Finally, secure the nut with a dropor two of araldite or superglue.

Figure 7. Templatesfor the front andrear panels of theenclosure. The dis-play as well as theswitch -board mustbe fitted with coun-tersunk screws.

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8 Figure 8. Inter -wiring diagram for the LCR meter.

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the display and secure them with adrop of araldite or superglue. Usecountersunk M3 size screws for theswitch -board. It is important that thedistance between this board and thefront panel is determined by 5 mmlong round clearance spacers and nutsin such a way that the knobs of theswitches are level with panel. Lastly,fix the front panel foil, if used, intoplace.

Make appropriate cut-outs for themains inlet and on/off switch in therear panel (Figure 7) and fit theseparts. The wiring diagram in Figure 8shows how the various interconnec-tions are made.

MORE SCREENINGLike the lower half of the enclosure,the upper half must also be screenedto minimize the effects of any externalstray fields. This is accomplished by asheet of 0.5 mm thick tin-plate cut tothe size and shape shown in Figure 9.Bend the screen along the lines indi-cated. Place it into the upper half ofthe enclosure and fix it in place withtwo small self -tapping screws at thesides. The screen must be earthed withthe aid of a solder tag secured with a

Figure 9. The templatefor the screen for theupper half of theenclosure shows thebending lines, the cut-outs and the threeholes to be drilled.

small self -tapping screw at the front of This completes the construction ofthe screen. the instrument-Part 3 in next

Make sure that the metal screens month's issue will deal with the cali-cannot touch the metal parts of the bration and the software. 1971:02-2

LCD. If this should happen, the digi-tal and analogue grounds of the circuitwould be linked which wouldadversely affect the accuracy of theinstrument.

ELEKTOR

240V-50HzNote the importance of proper

earthing of the instrument to themains earth-see Figure 8.

No. 970028

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ORONO/diRD ResearchResearch House, Norwich Road, Eastgate, Norwich. NR10 4HAPcstace & packing £4.50. Prices quoted are VAT. Al IMCMC.-ki afe

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Fully integrated and interactiveBud the circuit on the screen and set up thesimulations try choosing options from menusand dalogues. Run the simulation and viewyour results without leaving the program.

Flexible visualisation of resultsResits can ce displayed in graphs. tables ordirectly in voltmeters and ammeters. Changefrom typical to worst rAcr analysis and includethe effects of temperature on components_You can customise everything. right down tothe colour of an indhrzfual trace so you see justwhat you need

VersatilityA plethora of components inchioe resistors.capacitors. inductors. mutual inductor/transformers. controlled sources, bipolar'unction transistors. wrier diodes. powerMOSFETs. JFETs. MOSFETs, voltageregulators. Opera! oral amplifiers. &pie -couplers. voltage comparators. quartz crystals_IBIS LO buffers and switching matrixcorrect. rs arid much more All devices andmodel parameters can be edited to suityour needs.You can also rriVirrienthierarchical circuits in your designs.

PowerThe ony limit on circuit size is available RAMwith B`Spice there is no limit on the numberof components or nodes in the circuit.

ModelsTr -re are literally thousands of them . Thecomplete Berkeley SPICE model library as wellas commit- at libraries from manufacturer=such as Motorola. Texas Instruments,Burr -Brown. Maxim. NationalSemiconductor, Comtinear. AMP, Blantet,Linear Technology. APE)Cand many more.Included with aSpte is a complete modeland symbol editing package. 'u mli be ableto create. import and edit your won custommodels

CommandsAC frequency sweep.DC operating point.Transient analysis.Fast fourierNoise.SensitivityDistortion.Tf (srnall signal transfer),

Simulation OptionsAdded facility for suPcircuim (macro -modest.You can set ail simulation optionsAllows you to set initial conditions at a! nodes.Allows you to set initial guess at nodes forsimulation.Allow `not given' state for all values_Full access to Berketay SPICE simulationcontrol options is provided. For example youcan set global defaults for transistor channellengths and widths! Pius much more.

Waveform AnalysisDisplay and compare multiple respohse curvesin a single graph at the same time. EiSpicesimulation results can be selectively displayedand analysed graphically and in numericalformat as well as exported to otherapplications. All of BSpicefiasplaycapatittes are completely

Devices & Stimulus for SimulationSinusoidal, constant. periodic pulse.exponential. singe frequentynt. AM, DCvoltage. AC voltage. VCO. Vct. pietowlselineac exponential. polynomial /arbitrarysource, voltage -controlled voltage, voltage -Controlled current. current -controlled voltage.current-contrc4ted current. Laasy and idealtransmission tine. MESFET uniform RC.Current and voltage controlled switches are allavailable.

Cross ProbingCross probing allows you to display waveformresults simply by marking pins. wires anddevices on the circuit drawing.Monitor results while the simulation is inprogress then plot the results on linear or togscales.

GraphsTraces may be displayed as raw voltages andcurrent values or further p=essed usingarithmetic expressions, functions and FastFourier Transforms. law plot valuescorresponding to the cursor position on thegraph and gel data from multiple simulations inone graph. Split windows to allow multiplegraphs to be horizontally aligned andcompared

Data AnalysisPosition detection with mouse for data paints.Import arid export data to and from otherindustry standard SPICE programs PoiWSmith and Nyclust charts are all supported.


p *compact

power amplifierFast high -end design

The battery -powered preamplifier published in our February 1997 issuemust have made many of our readers long for a matching power ampli-

fier. Odd as it may seem, it is almost two years ago that we last pub-lished a high -end power amplifier. This realization prompted the present

compact power amplifier whose quality and layout match those of thepreamplifier. It offers medium power output. is not overly complex and

has a very high slew rate.

Design by T. Giesberts

442Elektor Electronics 5 97

The introduction gives a good idea ofthe power amplifier described in thisarticle.

The term 'compact' refers to boththe power output and the dimensionsof the amplifier. Of course, compact-ness is a relative term, because theamplifier contains no fewer than 19transistors. Over the years, compact-ness has taken on a different meaningthan, say, ten years ago. Then, a com-pact amplifier was understood to con-tain not more than eight to ten tran-sistors; today this figure is nearer totwenty-five. After all, as everybodynow realizes only too well, qualityalways has its price.

As far as output power is con-cerned, the present amplifier is defi-nitely intended for normal domesticuse. It produces some 50 watts into 8 SIor 85 watts into 4 a which is morethan ample for its intended use. Evenat relatively high volume, a domesticpower amplifier seldom provides more

than 1-2 power output. To high -volume freaks it may sound

odd, but most loudspeakersproduce a sound pressure

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of about 90 dB at a distance of 1 metrefor an input of only 1-2 watts-enough to make the neighbours rushfor the telephone.

It is dear, therefore, that the presentamplifier has more than ample reserveto reproduce even the highest peaks ina piece of music without any dis-cernible distortion.

A further benefit of the circuit is theuse of such a relatively high quiescentcurrent that with power outputs up to2.5 W the amplifier operates in Class A,which enhances the overall quality ofthe reproduced sound.

There are some other aspects whichwill be reverted to in detail later.Firstly, the power output is producedby two insulated gate bipolar transis-tors (IGBTs). These bipolar MOSFErsor, if you prefer, gate -controlled tran-sistors have been used in power ampli-fiers published by us before.

Secondly, the amplifier uses currentfeedback instead of the more usualvoltage feedback This has a beneficialeffect on the open -loop bandwidth, thepower bandwidth and the slew rate.

Thirdly, as may be seen from the

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technical data, the figures for har-monic distortion, intermodulation dis-tortion and the damping factor arevery good, indeed. They make it clearthat although the amplifier is small insize, it is large in performance.

THE DESIGNExperts in audio amplifier technology,as well as many other knowledgeableconstructors, will see from Figure 1that in some respects the design of thepower amplifier is different from theusual arrangement.

To start with, the almost obligatorydiffer el itial input amplifier is not there.In its stead there is a symmetricalinput stage that has some resemblanceto the buffer stage used at the input of

Figure 1. The mostconspicuous aspectof the circuit diagramis the omission of thetraditional differentialamplifier at the input.The output stage isbased on insulatedgate bipolar transis-tors.

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Elektor Electronics 5 '97

atommonou -woo ti MOMTechnical dataInput sensitivityOutput impedanceOutput power (0.1% THD)Power bandwidth (25 W into 8Slew rate

Signal-to-noise ratio (1 W into

Total harmonic distortion (B =1 W into 8 f225 W into 8 f2

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80 kHz)

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Dynamic intermodulation distortion(Square wave 3.15 kHz, sine wave 15 kHz)1 W into 8 f225 W into 8 II

Damping factor (8 0)

Open -loop parameters (R8 open)AmplificationBandwidthOutput impedance

0.0015% (1 kHz)0.0025% (1 kHz)0.008% (20 kHz)

0.0025%0.008%

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These data show the excellent performance of the power ampli-fier; exceptionally good are the power bandwidth and the slewrate. Some audio enthusiasts feel that performance data shouldbe taken with a pinch of salt and that the important thing is ahearing test. This is not an opinion shared by this magazine. It is Ctrue that figures do not reveal everything, but it is surely admittedby all that poor data point to properties that cannot have a bene-ficial effect on the sound quality.

As usual, the data are accompanied by a number of curvesobtained with an Audio Precision Analyser.Curves A show the total harmonic distortion (THD-1-11) between20 Hz and 20 kHz. The upper curve refers to 25 W into 8 SE andthe lower to 1 W into 8 SI_ Both curves show an exemplary perfor-mance; note that the usual increase in distortion at high frequen-cies is small.Curve B illustrates the distortion at 1 kHz as a function of thedrive power over a bandwidth of 22 Hz to 22 kHz. The slightincrease above about 2.5 W shows that from that point on theamplifier no longer operates in Class A. The clipping point is at50 kHz.Curves C refer to the output power of the amplifier as a functionof frequency with a load of 4 f2 and 8 f2 respectively.Curve D illustrates a Fourier analysis of a 1 kHz signal for an out-put of 1 W into 8 Q. Although the 2nd and 3rd harmonics areclearly visible, their levels at -105 dB and -122 dB are well belowthat of the fundamental. All other harmonics remain below thenoise floor.Listening tests showed the very good performance of the poweramplifier even better than the technical data. The sound repro-duction was very pleasant with good presence and transparenthigh -frequency performance that never became sharp. Low -fre-quency performance, both with classical and popular music,remained remarkably taut. The amplifier held the loudspeakers inan iron grip as it were and never relinquished control.

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the battery -operated preamplifier.In combination with current feed-

back this results in an amplifier that isappreciably faster than one with thetraditional differential input stage.

The power amplifier has an open -loop bandwidth of some 40 kHz at therelative low amplification of x2500.This enables the overall feedback,

which many enthusiasts do not like, tobe kept to a quite conservative level.

There is another side to everythingand current feedback is no exception.A well-known but unavoidable draw-back is the poor common -mode andsupply -line suppression. In the presentdesign, the effects of these have beencountered to a large extent, however,

by the use of two regulators in thepower lines to all voltage amplifiers.This, in turn, has the drawback thatthe level of the supply voltage to theseamplifiers is lower than that to the cur-rent amplifiers, although it shouldreally be higher This limits the maxi-mum drive, but that is compensatedby making the current amplifiers

444 Elektor Electronics 5197

amplify x2. Because of this, the outputstage is not arranged as the usual emit-ter follower, but rather as a compoundconfiguration.

Output transistors 117 and T18 are,as mentioned earlier, insulated gatebipolar types. These may be consid-ered as transistors with a MOSFETinput, which has the advantage ofrequiring a smaller current from thedrivers, Tis and T16. As this results inlower loading of the local feedbackloop, it. means that the amplificationof the drivers can be higher, whichenhances the linearity of the currentamplifiers.

INPUT STAGEThe input stage of the amplifier con-sists of emitter followers Ti and T, andsymmetrical voltage amplifiers T5 andT6 (Figure 1). Current feedback isobtained by coupling the output of thepower amplifier to the emitters of T5and T6.

The emitter followers provideimpedance matching and arrange thebase bias of T5 and T6. This arrange-ment relies on the fact that the dropacross R10 and Ru is virtually the sameas that across R3 and R4. The potentialacross the latter two resistors is heldconstant by current sources T3 and T4.Moreover, the reference voltages forthese current sources are provided byD1 and D2, the current through whichin turn is held constant by currentsources T7 and T8.

To prevent the operating levelsbeing upset by temperature effects inspite of these measures, T3 and T6 arethermally coupled to Ti and T2, whileDi and D, are thermally coupled tocurrent sources T3 and T4.

For best performance, it is advisableto select transistors Ti and T, on thebasis of equal base -emitter voltage andcurrent amplification, but make surethat the (offset) potential across R,<50 mV. Since complete symmetry isvirtually unattainable, there willalways be some offset which is whythe circuit based on IC3 has beenadded. This stage compensates theinput offset by placing an identicalpotential at feedback junction R10 -R11.This will be reverted to !attn.

Combinations R14 -C9 and R17 -C11are compensating networks, while Csand C10 minimize the effects of theparasitic capacitances of T5 and T6.

VOLTAGE AMPLIFIERSAND OUTPUT STAGEVoltage amplifiers T5 and T6 drive apush -Pull amplifier based on T9 -T13,which is arranged as a cascode stagefor the following reasons. Firstly, suchan arrangement limits the potentialacross, and the dissipation of, theactual voltage amplifier T9 -T10. Sec-ondly, a cascode configuration is ideal

for obtaining high amplification cou-pled with a large bandwidth.

The d.c. operating point of the volt-age amplifier is held stable by zenerdiodes D3 and 1D4, the current throughwhich is in turn held constant by cur-rent source T11.

The voltage amplifiers are loadedby the input impedance of 115-T16.Since this varies in accord with theoutput current of the power amplifier,it is linearized by resistor R. Capaci-tor C17 prevents any direct voltagefrom reaching the base of Tie.

The circuit based on T14 forms atemperature -independent transistorzener which has become a familiaraspect in many power amplifiers. Thistransistor is mounted on the heat sinkadjacent to output transistors T17 and118 and stabili 7PC the quiescent currentthrough these devices. The level of thiscurrent is set with P1.

Resistor R2,- provides the additionalnegative temperature coefficientneeded to compensate the time delayand thermal decay in the heat sink

The output of the voltage ampli-fiers is applied to current amplifierT15 -T18. Strictly speaking, this is acompound rather than a currentamplifier, since, apart from currentamplification, it also provides voltageamplification. The voltage gain (x2) isdetermined by resistors R-,9 and Rao;capacitor C18 serves to improve theresponse of the stage.

Since in a compound amplifier thecollectors of the driver transistors formthe output of the current amplifier, thegate -emitter potential does not influ-ence the maximum drive from thevoltage amplifier. This is an importantbenefit, because the gate -emitterpotential may be several volts. Theonly limiting factor in the presentamplifier, is, therefore, the knee volt-age of T17 and T18.

Emitter resistors R34 and R38 arelow -inductance types to prevent anytendency to oscillation or other spuri-ous effects.

Inductance 1 wound on R39enhances the performance of thepower amplifier when the load iscapacitive.

Zener diodes D5 and D6 protect thegates of 117 and 118 against overdrive.

In operation, the temperature ofdrivers T13 and T16 strongly affectsthe setting of the quiescent current.So as to make the power amplifier asstable with temperature variations asfeasible, these transistors are, there-fore, also mounted on the same heatsink as Ti4, T17 and T18. While it istrue that the quiescent current willalways vary to some (small) degreewith temperature, the thermal cou-pling of the various transistorsensures that any drift is well withinacceptable limits.

MISCELLANEOUSASPECTSSo as to keep the power amplifier ascompact as possible, it does not containelaborate protection circuits.There is,however, a power -on delay to suppressannoying clicks and plops at on and offswitching. Delayed °MAI switching ofthe power lines is effected by relay Rel.To avoid any noise on the signal pathsvia the supply lines, the relay has inde-pendent power lines. For this purpose,D10 and DI' rectify the secondary volt-age of the mains transformer. Theresulting direct voltage is buffered by

which ensures that the energizingvoltage for the relay is 22-24 V.

After the power has been switchedon, T19 begins to conduct slowly via1244 -R45 -C14. It takes a few secondsbefore this transistor is fully on: onlythen will the relay be energized. Whenthe power is switched off, C,4 israpidly discharged via R46 so that therelay is deenergized without any dis-cernible delay.

To aid the offset setting, IC3 com-pares the output of low-pass filterR40 -C,1 with the direct voltage at theoutput of the power amplifier. If thereis a difference, the operating point ofT5 -T6 is adjusted via R42 in such amanner that the average output of thepower amplifier remains at earthpotential. This arrangement ensuresthat the offset voltage at the outputcannot exceed that of IC3 100AV at25 °C). It is a fact, however, that tinyvariations caused by temperaturechanges cannot be eliminated entirely.

Zener diodes D7 and Ds reduce thesupply voltage of ±-23.2 V to the req-uisite level for IC3.

The reasons for regulation of thesupply lines to the input and voltageamplifiers has already been men-tioned. The regulation is provided byIC1 and IC2. Type LM317 and LM337respectively have been used for theseregulators because they provide very%good ripple suppression and tolerate ahigh peak input voltage. A furtheradvantage of them is that their outputpotential can be adjusted very accu-rately by means of resistors R20 -R21and R23 -R,4 respectively. CapacitorsC13 and C16 increase the ripple sup-pression to 70-80 dB.

CONSTRUCTIONThe power amplifier is best built onthe double -sided printed -circuit boardshown in Figure 2. Making the boarddouble -sided meant that it could bemade very compact without the neces-sity of (too) long copper tracks atessential locations. The layout is unam-biguous so that population of theboard is straightforward.

Transistors T14 -T18 are locatedneatly in a row at one side of theboard to facilitate their fixing on to the


Figure 2. The double -sidedprinted -circuit board for thepower amplifier. Large currentsflow over only a few tracks.

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Parts list

Resistors:F19, Ra = 470 12

R2 = 47 ki-2R3. R4 = 47 12R7 = 36.5 12, 1%Ra, R, = 340 SI, 1%R10. R11 = 22.1 11, 1%R,2. R15, R20. R21 = 270 12R13, R16 = 221 12, 1%R14, R17 = 150 0R18, R28 = 10 kc2

9 = 27.4 1-2, 1%

R21, R24 = 4.7 kfl1.8 ki-2

A26 = 1 MIR27, R31, R33, R35. R37, R43 = 22 SIR29, R30 = 47 12, 5 WR32, R36 = 390R34, R38 = 0.22 C2, 5 W. low inductalceR39 = 2.2 S2, 5 W

8.2. R41=1450 I<S2

R42., R45 = 27 kC2= 1 kit preset

Capacitors:C1. C14, C21. C22 = 2.2 pF metal-

lized polyester, pitch 5 or 7.5 mmC2, C7. C8, C,0 = 1 nFC3, C4 = 100 pF, 25 VC5. C6, C15, C16 = 10 pF, 16 V.

radialCg. C, = 10 nFC17 = 1 pF. metallized polyester.

pitch 5 or 7.5 mmCia = 4.7 nFC,9. C20 = 1000 pF, 40 V, radialCn = 100 pF, 40 V radialC24 = 220 pF, 25 V, radial

Semiconductors:D . D2 = LED. 5 mm, flatD3, D4 = zener diode, 4.7 V. 500 mWD5, D6 = zener diode, 5.1 V. 1.5 W07, Da = zener diode, 5.6 V, 500 mWD9 -D11 = 1N4002T,, T3, T6, Tg, =BC560CT2, T4, T5. Tic = BC55OCT7, Tg. T11 = BF245AT12 = BF872T13 = BF871-114 = BD139T15 = tv1JE15030 (Motorola)T16 = MJE15031 (Motorola)T17 = GT20D201 (Toshiba)T18 = GT20D101 (Toshiba) ig = BC640

Integrated circuits:= Liy1317T

IC, = LM337TIC3 = OP77 (Analog Devices)

Miscellaneous:Lt = see text

= relay, 24 V. 875 12 with singlemake contact 16 A. 250 V, e.g.Siemens Type V23056 -A0105 -A101

5 off PCB mounting flat 3 -way socketsHeat sink 1.2 K W-1 or smaller - seetext; e.g. Fischer SK85SAr75 mmfrom Dau (telephone 01243 553 031)

Insulating washer and insulatingbushes for T14 -T15

PCB Order No. 970043 - see Read-ers Services towards the end ofthis issue

446 Elektor Electronics 5 97

heat sink. They must, of course, beelectrically isolated from each otherwith the aid of insulating washers andbushes for the fixing saews. In view ofthe required temperature stability, it isadvisable to keep the terminals of T14as long as possible to ensure that thedevice, when mounted, is at about thesame height as the centre of Tu. Thismakes for good thermal coupling.

The other semiconductors and inte-grated circuits do not need extra cool-ing.

As mentioned earlier, good thermalcoupling of a number of components(T145; T7 -T6; D1 -T3; and DrT.1) in theinput stages is also imperative for goodperformance. The easiest way, ofensuring this is to secure the variouspairs of components together withcable ties. In the case of D1 -T3 andD -,-T4 this is possible only if flat diodesare used. Tie the pairs together beforefitting and soldering them on to theboard. Mind the orientation of the

Suggested power supply (for monoamplifier):

Toroidal mains transformer. sec-ondary 2x22 V. 160 VA

Bridge rectifier 200 V, 35 A4 off electrolytic capacitor 10,000 pF,

50 VFuse holder and fuse 800 mA. slow

Figure 3. Photographof the completed pro-totype board with heatsink. Two- and three -pin flat PCB mountingconnectors are usedfor the loudspeakerand power line con-nections.

Figure 4. The powersupply may be keptsimple, but shouldhave ample reservepower. Note that thediagram shows adesign for a monopower amplifier.

power -ondelay

OAS T

diodes. It is advisable to mark the tran-sistors with n -p -n or p -n -p, as the casemay be, so that it is dear at a laterstage which pair is which.

Inductor L1 consists of eight turnsof 1.5 mm dia. enamelled copper wirewound around a 9 mm drill bit. Whenit is wound, withdraw the drill bit,insert R39 into the coil and fit and sol-der the assembly on to the board at aheight of a few millimetres above thesurface.

All connections that carry large cur-rents are output via PCB mounting flatsockets. The power connections are atthe middle of one side of the boardmarked LS+ and LS-. The power linesto the relay are connected via ordinary

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The Home of'e-.'e://te().4-e. Its not what you do,its HOW you do it that counts!.

Hart Audio Kits and factory assembled units use the uniquecombination of circuit designs by the renowned John LinsleyHood, the very beat audiophile components. and our ownengineering expertise. to give you unbeatable performanceand unberweable value for money.We have always led the field for easy home construction toprofessional standards, even in the sixties we were usingeasily assembled printed circuits when Heathkit in Americawere still using tagboardst. Many years of experience andInnovation, going back to the early Dinsdale and Baileyclassics gives us incomparable design background in theneeds of the home constructor. Tills simply means thatbuilding a Hart kit is a real pleasure, resulting in a piece ofequipment that not only saves you money but you will beproud to own.Why not buy the reprints and construction manual for the kityou ere Interested in to see how easy it Is to build your ownequipment the HART way. The FULL cost can be creditedagainst your subsequent kit purchase.

'AUDIO DESIGN' 80 WAIT POWER AMPUFIER.

This faintest.: John Linsley Hood designed amplfier is the Pagshipof our range, and the ideal powerhouse for your ultimate hifisystem This kit is your way to get OK performance at bargainbasement prices. Unique design features such as fully FETstabilised power supplies give this amplifier World Classperforrrarr_e with starting carry and transparency of sound, Mewlto the famous HART quaky corrponeW as ease of corabuction.Standard moat cares with a verwelee passive front-end geeing 3switched inputs. wait ALPS precision 'Blue Velvet' low -noisevain* and balance controd. no need for an external preamplConstruction is very simple are ereoyable with aS the Wien vie*done for you. even the wiring is pre-termirated, ready for instantuse!. All versions are avertable with Standard components orveneey selecMd S.Qer Autophee components and Gold Platedveake to rnmaS and at are also avaliabie factory assemble -aK1100 Cona;we STANDARD Stereo Amptter Kit. £415.21K1100S Conde& SLAVE AmplEar Kit, 53.62K1100IA Corplee MONOBLOC Amplifier . E271.20RLI111 Reprints of blest ArnpVer articles . _ £1.50K1100061 Construction Manual with hi parts £5.50

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In passin_qboard terminals. Note that these linesconsist of three wires: this means thatthe earth line must NOT linked to theamplifier earth.

The completed board with heatsink is shown in Figure 3. The heatsink must have a thermal resistance of1.2 K W-1 or smaller.

POWER SUPPLY ANDQUIESCENT CURRENTWhen the board has been completedand thoroughly inspected for anyfaulty workmanship (including a one -by -one check of the componentsagainst the part list), a few operationaltests need to be carried out. Naturally,a power supply is needed and a suit-able arrangement for this is shown inFigure 4. This is a traditional setup ofpower -on delay, mains transformer,with a 2 x 22 V, 160 VA secondary, a35 A bridge rectifier and four 10,000I.LFelectrolytic reservoir capacitors. Thissupply provides sufficient currenteven when 4 fI loudspeakers are used.Note that the diagram is for a supplyfor a mono amplifier: two are neededfor a stereo amplifier.

The diagram also shows how thepower lines for the relay are obtained.

The power -on section is advisablebut not obligatory. It serves to preventlarge current peaks during switch -on.

As in all power supplies, good,firm, well -soldered connections are ofprime importance. They ensure thatthere is no unnecessary resistance inthe path of large currents.

Before the power is switched on, itis vital that preset P1 on the poweramplifier is turned completely anti-clockwise. If this is not done, there is arisk that the quiescent current throughthe output transistors quickly reachesa very high level and the circuit is notdesigned to cope with this.

After the power has been switchedon, check with a multimeter whetherthe potentials at the output of ICI andIC, are as indicated on the circuit dia-gram in Figure 1 (±23.2 V respec-tively). Then, measure the output volt-age of the amplifies; which must be 0 Vor very nearly so. If it is not, recheckthe entire construction, particularly theinput stiges.

When up to this point all is welland the LEDs light, it may be assumedthat the entire power amplifier is ingood working order. It is then time tocheck all the potentials at the testpoints indicated in Figure 1.

Next, set the quiescent current withPi. This is fairly high in this poweramplifier: about 400 mA when a heatsink as specified is used; if a heat sinkof 0.6K W-1 is used, the current mayeven be as high as 500 mA. Connect amillivoltmeter set to its 200 or 250 mVrange across R34 or R38 and turn PIslowly clockwise until the meter reads

88 mV (current = 400 mA) or 110 mV(current = 500 mA).

Leave the amplifier to warm upthoroughly and then readjust P1 asrequired.

ASSEMBLYThe design of the printed -circuit boardis intended for its use as a monoamplifies From a quality point of NieW,this is the best way of building anamplifier. Use a compact enclosure,perhaps with integral heat sink, andassemble board and power supply inthis to make a stand-alone monoamplifies A stereo amplifier is obtainedby building two of these mono unitsand simply stacking them.

Wiring up the assembly is straight-forward. Use heavy-duty wire for the+ve, -ve and earth supply lines andlink them to the appropriate terminalson the board. Use heavy-duty wirealso for linking the loudspeaker termi-nals with the LS+ and LS- PCBmounting 4 mm sockets on the board.

Link the phono input socket at therear of the enclosure to the two inputterminals on the board via a shortlength of screened audio cable.

Next, link the two 22 V- and 0lines to the relay - remember that the0 line must not be connected to theamplifier earth - see below.

The mains inlet should be of goodquality, preferably with an integralfuse holder The fuse rating is shownon the serial number label that shouldbe affixed to the rear of the cabinet

It is imperative that earth loops areavoided. This is best done by ensuringthat there is link between the mainsearth, the 0 supply line and the cabi-net earth at only one point. Normally,and most conveniently this is at thesignal input socket. If a non -insulatedphono socket is used, this is automat-ically connected to the cabinet earth,so that no further action is needed.

It is, of course, possible to assembletwo mono amplifiers using a singlepower supply in one cabinet, but thisis not advisable. Even if it is desired touse only one cabinet, each of the monoamplifiers should have its own discretepower supply. The introductory pho-tograph shows that this is how theprototype was constructed. The cabi-net used for the prototype was pro-vided with an integral heat sink andmeasured 445x75x305 mm(WxHxD).

19741103i

1.41114:41111:i.

Eitri

Most readers of this magazine knowthat it is published in identical form(at least as far as the articles are con-cerned) in Dutch, French and Ger-man, as well as in Greek, Polish, Por-tuguese, Spanish and Swedish in non-identical form. The Dutch, English,French and German issues are pro-duced in the Netherlands, but pub-lished in the relevant country. Theseissues are the responsibility of aninternational team of writersltransla-tors and technical editors.

On the face of it, there should beno problem in producing a suprana-tional electronics magazine, sinceelectronics is more international thanany other branch of engineering. Theelectronics market is a world market:there is not one semiconductor or ICmanufacturer who does not operateinternationally. Also, norms and spec-ifications tend to be internationallyagreed.

Working in a multi -language teampresents no real difficulties: most ofthe editorial staff have workedtogether for almost twenty years. Ofcourse, technical translating is quitedifferent from literary translating. forone, the technical translator has toknow and understand the subject!

Most difficulties arise from the dif-ferences in standards laid down manyyears ago. For instance, an article ontelevision will have to take intoaccount that France (and easternGermany) uses Secam, England PAL -1 (but many other English-speakingcountries NTSC), and Germany andthe Netherlands PAL -BIG. The sameapplies to the different mains voltageoutlets in the four countries. Astratransmissions are popular in Britainand in Germany, but not much in theNetherlands. Similarly, GSM mobiletelephones for the E -band(1800 MHz) are in use in Britain andin Germany, but not in France andHolland.

Surprises still occur as well: chip-board or PVC tubing of the densityspecified in a German design are notavailable in the Netherlands. AndSiemens products are not not easilyavailable from retail outlets even inGermany. Strangest of all: try to finda bicycle rear light that is standard inall four countries!

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Cowing &Selecti4y. 1V RI

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V

on abudged

This is probably thesimplest and cheap-

est logic analyser youhave ever seen. A

handful of inexpen-sive components incombination with a

straightforward BASICprogram enable you

to check the logicstate and correlation

of up to four digitalsignals with a 5 -volt

swing.

When logic does not function in a logicway, or you don't understand the logicof it all, the best thing to do is take adeep breath and start analysing theindividual components that make up alogic combination. No problem if youhave an oscilloscope or, in some cases,a simple multimeter. Next, you have tolook at how the various 'components',which will usually be digital signals,interact. And that's where the prob-lems start because you do not have therequisite test equipment which dis-plays the logic states in one go.

Logic analysers used to be confinedto the realms of professional electron-ics design laboratories and repair sta-tions. These instruments normally costa small fortune, and are able to displaytens of digital signals simultaneously atvery high sampling frequencies. Yet,the basic elements lurking in these pro-fessional instruments are (1) logic leveldetectors, and (2) a common visualisa-tion (display) device.

Look at the single star at the top ofthis page and you know that it is not

Design by A. TOchter

4 -channellogic analyser

our intention to mimic or evenapproach the operation of a profes-sional logic analyser. Here, we'll makedo with four channels, extremely sim-ple hardware and a PC acting as thedisplay device.

LOGIC LEVEL DETECTIONA logic level detector is required to beable to tell the difference between alogic 'high' level, also called '1', and alogic low level, or '0'. In nearly all oftoday's logic circuits, '0' means 0 V,and '1', +5 V, simply because the sup-ply voltage is 5 V That is theoretical,however, and most of you will knowthat these ideal levels are hardly everencountered in practice.

The circuit diagram in Figure 1shows four identical converters whichtranslate logic signals (0 or 1) into cor-responding signals which can be readand processed by a PC. As all convert-ers are identical, we may call themchannels. Each of them consists of aSchmitt -trigger gate followed by anopto-isolator. Let's look at the topchannel, whose input signal arrives onICIa via input 1. The two Schmitt trig-ger gate inputs are held at 0 V by resis-tor Rl. This is done to set a logic 0 onthe channel when it is not used, andto ensure that the gate does not oscil-

late or produce spuri-ous output sig-

nals. If alogic 1 isapplied toinput 1, alogic 0

appears atthe output of

the gate,because it inverts.

If a logic 0 isapplied, or no signal,

then the gate suppliesa '1' at its output, and the

LED inside opto-isolatorIC2 is switched on. Resistor

R12 serves to limit the LEDcurrent to a safe value. The LED

light causes the phototransistorinside 1C2 to conduct, so that its

collector potential drops. The resul-tant level on the CTS line may be readby the PC via its RS232 port.

The following handshaking signalsare used to convey the logic levels atthe four inputs:

Channell: CTS (clear to send)Channel2: DSR (data set ready)Channel3: RI (ring indicator)Channel4: DCD (data carrier detect)

The common positive supply voltageof about 10 V for the phototransistorsis derived from the PC via the RxDline.

The PC is connected to K1 bymeans of a standard RS232 cable with9 pins at both sides, and non -crossedwires.

The 5-V supply voltage for the74HCT132 and the LEDs inside theopto-isolators has to be supplied exter-nally. The maximum anticipated cur-rent consumption will be of the orderof 75 mA when all four channels are at'0', and less than 0.5tiA when all chan-nels are at '1'. This sort of current con-sumption is easily managed by a 7805voltage regulator in its standard appli-cation circuit. Alternatively, you mayobtain the 5-V supply voltage from thedigital circuit under test.

The copper track layout and com-ponent mounting plan of the circuitboard designed for the interface isshown in Figure 2. Unfortunately, thisboard is not available ready-madethrough our Readers Services. Con-struction is all plain sailing if you workcarefully, and stick to the parts list and


the component overlay. Be sure to usea socket, not a plug -type (male), con-nector for KI.

THE PROGRAMThe pmgram you have to run on yourPC to visualize the logic state of thefour input signals is given in Figure 3.It is written in GW-BASIC, and prettystraightforward. Even if you do notfancy building the hardware, the pro-gram is still worth examining if youare interested in learning how, say, anRS232 port is read using a simple lan-guage like BASIC.

The program and the hardwaremay be used on any PC having GW-BASIC and a free COM port. Even anold AT may be dusted off for use inthis project. If you are not sure aboutthe number of RS232 ports on the PC,use the BIOS setup to locate the portsand their addresses. In most cases, twoports will be available: COM1 at 3F8H,and COM2 at 2F8H. Check theseaddresses against those in line 6 of theprogram. Obviously, to avoid annoy-ing problems with IRQ conflicts, youshould choose a free COM port toattach the logic analyser hardware. Ifyou don't fancy tweaking the BIOSsettings in your computer, useMicrosoft Diagnostics (MSD), a DOSprogram which will tell you the PCsettings instantly.

The core of the program is formedby the routines which translate logiclevels read from the RS232 port regis-ters into an oscilloscope -like trace onthe PC monitor. The screen layout hasbeen kept as simple as possible to pre-vent distraction from the four logiclevel traces displayed in the centre.

The program starts by reading a number of variables which determinethe operation of the software. Thesevariables include wS for the COM portnumber (1 through 4), k$ for the num-ber of analyser channels (1 through 4),HCAdr for the COM port status regis-ter address (base+3, where base is 2F8,3F8, 3E8 or 2E8), and measS, which

COMPONENTS LIST

Resistors:R1 -R8 = 10kgR9 -R12 = 1500

Capacitor:Cl = 100nF

Semiconductors:IC1 = 74HC132 (or 74HC00)IC2-1C5 = CNY17-2

Miscellaneous:K1 = 9 -way sub -D socket, PCBmount, angled pins

6 solder pin

+54

I 73rnA

I = 0,A2

IC1.74HC132

IC1a

IC1b

3

if&

I C 1 c

004

0

10 ff&

12IC1d

MIM

13 ffa

selects the sweepmode: continuous, sin-gle sweep or withpause. Remember, theprogram reads the sta-tus of four handshak-ing signals, RI, DCD,DSR and CTS, from the RS232 portregister.

In the *** drawmeasured signals ***routine, the variableCstate is evaluated to

6

11

R10

IC21 6 I5

2

CNY17-2

IC3

4

1 6 15

R11

2

CNY17-2

IC41 16

K1*

2 14

CNY17-2

ICs1 16

02_0

0

a

4_0

CNY17-2

Figure 1. The logicanalyser interfaceoffers four electricallyisolated input chan-nels for 5 -volt 77Llogic.

5

970042 - 11 vr

0

0

determine if a 'high' ora low' line has to bedrawn in the timingdiagram which appearson the screen. Thereading of the variabletakes place in a loop

which checks all four channels. Onceall four traces have been drawn on the

screen, the programreads the sweep modevariable to determinehow it continuous.

Figure 2. Playout andmounting p

CB trackcomponentIan.

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lektor Electronics 5/97 53

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REM Simple Logic Analyser using RS232

CLSCLEAR

DIM CAdr(4), p(4, 3)

CAdr(1) = SH3F8: CAdr(2) = CAdr(3) = tH3E8:CAdr(4) = &H2E8

REMKEY(1) ON: ON KEY(1) GOSUB flKEY(2) ON: ON KEY(2) GOSUB f2

REHPRINTPRINT TAB(24); CHR$(201);PRINT TAB(24); CHRS(186);PRINT TAB(24); CHR$(186);

CHRS(186)PRINT TAB(24); CHR$(186); STRING$(30,PRINT TAB(24)) CHRS(200); STRINGS(30,LOCATE 25, 30PRINT '<F1> Restart

Write Logic Analyser logo to screen

STRINGS(30,STRINGS(30,

PC -

Declare subroutines for Keys <F1> and <F2>

CHR$(205)); CHR$(187)CHR$(32)); CHR$(186)Logic Analyser

CHR$(32)); CHR$(186)CHR$(205)); CHR$(188)

/ <F2> End'; SPC(20);

REH determine COH portLOCATE 10, 8

PRINT 'COH port : (1) COM1 (2) COH2 (3) COH3 (4) COM4";

DOwS = INKEY$

LOOP UNTIL (VAL(w$) < 5) AND (VAL(w$) > 0)PRINT 'CON"; wS

REM Number of channels to useLOCATE 12, 8

PRINT 'Channels (1-4)DO:

kS = INKEY$Channel = VAL(kS)

LOOP UNTIL (Channel < 5) AND (ChannelPRINT Channel

REM Sweep modeLOCATE 14, 8

PRINT 'Sweep mode: (C)ontinuous;

DOmeasS = UCASES(INKEY$)

LOOP UNTIL measS = "C" OR measSPRINT measS

REM Sample rate delayDO

LOCATE 16, 8

> 0)

/ (S)ingle sweep / (P)ause:

= '5" OR measS = "P"

DOCLS

REM Draw X-axes and write additional text to screen

FOR w = 1 TO ChannelLINE (0, w 80)-(640, w 80), 15, , 255p(w, 0) = 0COLOR w + 2, 0

LOCATE 1, 1 + ((w - 1) 10)PRINT 'Channel"; w;

NEXT wCOLOR 15, 0

PRINT "Com"; wS;measS

LOCATE 25, 30PRINT '<F1> Restart / <P2> End"; SPC(20);

Delay :"; Delay; ' Sweep node :";

REM Draw reference linesFOR e = 1 TO 640 STEP 10

LINE (e, 25)-(e, 320), 8, 1024NEXT eREM Draw measured signalsFOR i = 1 TO 640

FOR x = 1 TO ChannelCState = INP(HCAdr + 6) AND 240IF CState AND 2 (3 + x) THEN

LINE (p(x, 0), p(x, 3))-(i - 1, p(x, 1) - 50), x +2

p(x, 3) = p(x, 2)ELSE

LINE (p(x, 0), p(x,p(x, 3) = p(x, 1)

END IFp(x, 0) =

NEXT xFOR q = 1 TO Delay:

NEXT q, i

REHselected

IF measS = 'P' THENLOCATE 25, 28

3))-(1 1, p(x, 1)), x + 2

After each sweep: Determine what sweep mode was

PRINT "Paused! Press any key to continue"; SPC(20);SLEEP

END IFLOOP UNTIL measS = "5"LOCATE 25, 20PRINT 'End of Measurement! Press any key to continue";SPC(10);

SLEEPRUN

INPUT "Delay (0 - 50.000) :", Delay REMLOOP UNTIL (Delay >. 0) AND (Delay <= 50000) fl:

RUNRETURNHCAdr = CAdr(VAL(w$))

OUT HCAdr + 3, IHP(HCAdr + 3) OR 64FOR w = 1 TO Channel

p(w, 1) = w * 80: p(w, 2) = (w * 80) - 50:BO

NEXT w

REM MeasurementSCREEN 9

Figure 3. Listing of theGW-BASIC program

Start GW-BASIC, type the programinto GW-BASIC, save it to disk, andRUN it. As shown in Figure 4, it willprompt you to enter a number of set-tings discussed above. Having donethat, the display should show fourhorizontally running lines. Now applya logic 1 to channel 1 by connectingthe relevant input to the +5 V supplyon the interface board. If everythingworks, the channel 1 trace shouldrespond by shifting to the 'high' posi-tion.

The instrument is then ready foruse. Remember, its inputs are suitablefor connection to 5 -volt digital logiconly. In practice, that covers most, if

p(w,REH

3) = w f2:

SCREEN 0CLSEND

RETURN

Figure 4. The welcomescreen with theanalyser settingprompts.

not all, of today's circuitsusing TTL logic, as well asmany CMOS and HCMOSapplications.

Figure 5. Example of atiming diagram sup-plied by the logicanalyser on a PCscreen (note: screen -dump converted fromcolour to mono-chrome).

Subroutine for Fl

Subroutine for F2

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The p-i-n (or PIN)diode is a semicon-

ductor diode thatcontains a region of

almost intrinsic(i-type) semiconduc-

tor between thep -type and n -type

regions. The deple-tion layer associatedwith the p -n junctionis entirely contained

within the i-typeregion in the

structure. At low sig-nal frequencies the

diode behaves simi-larly to a normal p -njunction, but at high

frequencies it exhibitsa variable resistance.

The p-i-n diode isused extensively as amodulator and switch

in microwave sys-tems.

By Joseph J. Carr, BSc. MSEE

usingthe p-i-n diode

A

N-T;;:e

N-Tyce

++T_+ + + + +++++++ + + +

Figure 1. (A) PN junc-tion diode; B) P -I -Ndiode.

Let us consider some of the appli-cations of the p-i-n diode. Most mod-ern radio transceivers (i.e. "transmit-ter-receivers") use "relayless" switch-ing to go back and forth between thereceive and transmit states. Relaylessswitching is usually done with p-i-ndiodes. Receiver U. filters and front-end bandpass filters are selected witha front panel switch that handle onlydirect current. How? Again, p-i-ndiodes. These interesting little com-ponents allow us to do switching atr.f., i.f. and audio frequencies withoutrouteing the signals themselves allover the cabinet. In this article we willsee how these circuits work.

The p-i-n diode is different fromthe standard p -n junction diode (seeFig. IA). It has an insulating (intrin-sic', hence the 1' in 'p-i-n) regionbetween the p- and n -type material(Fig. IB). It is therefore a multiregionsemiconductor device despite havingonly two electrodes. The i-region isnot really a true semiconductor insu-lator, but rather is a very lightlydoped n -type region. It is called an'intrinsic' region because it has veryfew charge carriers to support theflow of an electrical current.

When a forward bias potential isapplied to the p-i-n diode, charge car-riers are injected into the i-regionfrom both n- and p -regions. But thelightly -doped design of the intrinsicregion is such that the n- and p -typecharge carriers don't immediatelyrecombine (as in p -n junction diodes).

;77113- tlb

There is always a delay period forrecombination. Because of this delayphenomenon, there is always a smallbut finite number of carriers in thei-region that are uncombined. As aresult, the resistivity of the i-region isvery low.

One application that results fromthe delay of signals passing across theintrinsic region is that the p-i-n diodecan be used as an rf. phase shifter Insome microwave antennas phaseshifting is accomplished by the use ofone or more p-i-n diodes in serieswith the signal line. Although thereare other forms of r.f. phase shifterusable at those frequencies, the p-i-ndiode remains popular.

Several styles of package are usedfor p-i-n diodes at small signal powerlevels. Most of these will be familiar tomost readers, but some are probablyrecognized only by people with someexperience in u.h.f. and up switchingcircuits. The NTE-553 and ECG -553p-i-n diodes will dissipate 200 mW,and use the standard cylindrical pack-age style. The NTE-555 and ECG -555devices, on the other hand, use theu.h.f. flat package style and can dissi-pate 400 MK I used these diodes forthe experiments performed to writethis article because they are serviceshop replacement lines, and both ECGand NTE are widely distributed inlocal parts stores. An alternative thatmight be harder to come by is theMPN3404, which uses a TO -92 plasticpackage.

Radio frequency signals can passthrough the p-i-n device, and in fact


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Figure 2. Series p-i-ndiode switch circuits:(A) RF choke loaded;(B) resistor loaded.

ckcas:sh=r-asalasamer-samit

see it in some circumstances as merelya parallel plate capacitor. We can usep-i-n diodes as electronic sitches fortf. signals, and as an EL delay line orphase -shifter, or as an amplitudemodulator

P -I -N DIODE SWITCHCIRCUITSP -I -N diodes can be used as switchesin either series or parallel modes. Fig-ure 2 shows two similar switch cir-cuits. In the circuit of Figure. 2A thediode (D1) is placed in series with thesignal line. When the diode is turnedon, the signal path has a low resis-tance, and when the diode is turnedoff it has a very high resistance (thusproviding the switching action).When sitch S1 is open, the diode isunbiased so the circuit is open byvirtue of the very high series resis-tance. But when S1 is closed, thediode is forward biased and the sig-nal path is now a low resistance. Theratio of off/on resistances provides ameasure of the isolation provided bythe circuit. A pair of radio frequencychokes (RFC1 and RFC2) are used toprovide a high impedance to r.£ sig-nals, while offering low d.c. resis-tance.

Figure 2B is similar to Figure 2Aexcept that the r.f. chokes are deleted,and a resistor is added. Figure 3shows a test that I performed on the

circuit of Figure 2B using a 455 kHzsignal (the 'scope was set to show

only a few cycles of the 455 kHz). Theupper trace in Figure. 3A shows theinput signal and the lower trace theoutput signal. The amplitude of thenearly unattenuated output signal is1200 mV peak -to -peak. The trace inFigure. 3B shows the same signal-when the switch open (Le. +12 V d.c.disconnected), but with the oscillo-scope set to the same level. Increasingthe sensitivity of the 'scope showed alevel of 12 mV getting through. Thismeans that this simplest circuit pro-vides a 100:1 on/off ratio, which is 40dB of isolation. [Note: for this experi-ment the ECG -555 and NTE-555 hotcarrier p-i-n diodes were used].

Figure 4 shows the circuit for ashunt p-i-n diode switch. In this case,the diode is placed across the signalline, rather than in series with it.When the diode is turned off, theresistance across the signal path ishigh, so operation of the circuit isunimpeded. But when the diode isturned on (S1 closed) a near-short-dr-cuit is placed across the line. This typeof circuit is turned off when the diodeis forward biased. This action is incontrast to the series switch in whicha forward biased diode is used to turnthe circuit on.

A combination series -shunt circuitis shown in Figure 5. In this circuit, D1and 13, are placed in series with thesignal line, while 133 is in parallel withthe line. Di and D2 will turn on witha positive potential applied, while 133turns on when a negative potential isapplied. When switch Si is in thelower position, a positive potential isapplied to the junction of the threediodes. As a result, Di and D, are for-ward biased and thus take on a lowresistance. At the same time, D3 ishard reverse biased, so has a veryhigh resistance. Signal is passed frominput to output essentially unim-peded (most p-i-n diodes have a verylow series resistance).

But when Si is in the upper posi-tion, the opposite situation obtains. Inthis case, the applied potential is neg-ative so DI -13-, are reverse biased (andtake on a high series resistance), while133 is forard biased (and takes on alow series resistance). This circuitaction creates a tremendous attenua-tion of the signal between input andoutput.

OTHER P -I -N DIODEAPPLICATIONS

When used as a switch, p-i-ndiodes can be used to switch devicessuch as attenuators, filters and ampli-fiers in and out of the circuit. It hasbecome standard practice in modernradio equipment to switch d.c. volt-ages to bias p-i-n diodes rather than

Figure 3. Switched andunswitched input/out-put waveforms.

S

Kt

DIPIN DIODE

Figure 4. Shunt switchcircuit.

Figure 5. Series -shuntswitch circuit.

SI

970013.1G


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TRARSUITTERAn

(

RECEIVER

Art

Figure 6. P -I -N diodeTi!? switching.

directly switch r.f./Lf. signals. In somecases, the p-i-n diode can be used tosimply short out the transmissionpath to bypass the device.

The p-i-n diode will also work asan amplitude modulator. In this appli-cation, a p-i-n diode is connectedacross a transmission line, or insertedinto one end of a piece of microwavewaveguide. The audio modulatingvoltage is applied through an r.f.choke to the p-i-n diode. When a c.wvsignal is applied to the transmissionline, the varying resistance of thep-i-n diode causes the signal to beamplitude modulated.

Another application is shown inFigure 6. Here we have a pair of p-i-ndiodes used as a transmit -receive (TR)switch in a radio transmitter; modelsfrom low-h.f. to microwave use thistechnique. Where you see a so-called'relayless TR switch', it is almost cer-tain that a p-i-n diode network suchas Figure 6 is in use. When switch S1is open, diodes D1 and D, are unbi-ased, so present a high impedance tothe signaL Diode D1 is in series withthe transmitter signal, so blocks itfrom reaching the antenna; diode 1),,on the other hand, is across thereceiver input so does not attenuatethe receiver input signal at all. Butwhen switch S1 is closed, the opposite

14 II -T

-

Figure 7. IF bandpassfilter switching.

situation occurs: both DI and D2 arenow forward biased. Diode D1 is nowa low resistance in series with thetransmitter output signal, so thetransmitter is effectively connected tothe antenna. Diode D, is also a lowresistance, and is across the receiverinput so causes it to short out_

Figure 7 shows how multiple If.bandpass filters are selected with onlyd.c. being routed around the cabinetbetween circuitry and front panel.When the switch is in the positionshown, V+ is fed to filter no.2 diodesand V- to those of BPF1; so filter no.2 is activated and BPF1 is blocked.When the switch is in the oppositeposition, the alternate filter is turnedon. This same arrangement can beused in the front-end of the receiver,or the local oscillator, to select LCcomponents for different bands.

Another filter selection method isshown in Figure 8. This circuit is apartial representation of the front-endcircuitry for the Heathkit SW -7800general coverage shortwave receiver.

The circuit of Figure 8 is shownusing a switch (Si) to apply or removethe +12 V d.c. bias potential on the

diodes, but in the actual receiver thispotential is digitally controlled. Thedigital logic elements sense which ofthirty bands are being used, andselects the input r.f. filter accordingly.

P -I -N DIODEATTENUATORSAnother application for p-i-n diodesis as a voltage -variable attenuator inr.f. circuits. Because of its variableresistance characteristic, the p-i-ndiode can be used in a variety ofattenuator circuits. One of the sim-plest is the shunt attenuator of Fig-ure 9. The p-i-n diode acts like anelectronically variable resistor. Theresistance across the diode's terminalsis a function of the applied bias volt-age. This voltage, hence the degree ofattenuation of the r.f. signal, is pro-portional to the setting of poten-tiometer R1. The series resistor (R2) isused to limit the current when thediode is forward biased. This step isnecessary because the diode becomesa very low resistance when a certainrather low potential is exceeded. Thiscircuit is used as an r.f. gain control onsome modern receivers. 19m31

vo

PROUANTEVA

Figure 8. Front-end fil-ter switching.

Figure 9. Simple vari-able r.f. attenuator cir-cuit.

BPF

57C.:13 - 15


underlines on cd-romDear Editor-I was surprised tonote on the CD-ROM with winningprograms of the software compe-tition that all hyphens in the filenames have been altered intounderlines.(US: underscores). Irefer in particular to the program-mable remote control - Minilap -to be found in directory NL\21.

The underlining does not posea problem as far as the EXE filesand the device drivers are con-cerned, but when XP-ZAP.EXE(altered into XP_ZAP.EXE) is start-ed. the program looks for ini-fileXP-ZAP.EXE, which it cannot findbecause this is now calledXPZAP.INI. This means that thepreferred settings of the user canno longer be loaded.

lit is not clear to me why thisalteration was found necessary: Ihave never had problems withhyphens in file name, and itoccurred to me that it would beuseful to other readers to write toyou. Users may note that the prob-lems can be resolved easily byrenaming the file name XP_ZAP.INIto XP-ZAP.INI.

M.M.

There are several CD-ROM for-mats: most PCs use theISO -9660 standard. In this stan-dard a number of ASCII symbolscannot be used in file namesand one of these is the hyphen.For the production of ourCD-ROMs I50-9660 is used andthis means that during the writ-ing of the disk all hyphens areautomatically converted intounderlines. It is possible to cir-cumvent this conversion (and

Ir.

this is, indeed, often done nowa-days), but the disk would thenno longer meet the standard. Asyou have already correctly point-ed out, the remedy is simple:copy all files to a directory onthe hard disk and replace theunderlines in the file names bya hyphen. All will then work 'nor-mally' again.

remote control(April 1989)Dear Editor-I have been lookingfor the Elektor Electronics issuewhich contained a project for aremote control extension. This isfor use to control a VCR or TVreceiver from a room adjacent tothe one where the equipment islocated.

P.H.

This project appeared in our April1989 issue (p. 31). Since this isobsolescent, a new design forsuch an extension will be pub-lished in a future issue of thismagazine.

motor controller(February 1997)Dear Editor-Your February 1997issue contains an article describ-ing a 'Motor controller for R/Cmodels'.

The data for this circuit statethat the controller is suitable foroperation from supply voltages of6-10 V. My question is: can thecontroller be used with a 12 V sup-ply or do I have to alter a few com-ponents?

P.K.

No problem: the controller canwork from 12 V. The processor,IC7, operates from a regulated+5 V line, irrespective of theinput supply voltage. Neverthe-less, we recommend anabsolute limit of 15 V. What ismore important, however, is thecurrent drawn by the motor: thismust not exceed 40 A to ensurethat the ratings of the MOSFETsare not exceeded.

magnetic field meter(January 1997)Dear Editor-When I connect the'Magnetic -field meter' to my com-puter and start the associated pro-gram. I get the message whenusing DOS: 'interface not found':when I use Windows the programdoes not start at all. I have care-fully checked the completed boardbut cannot find anything wrong.

C.S.

We have checked your boardwith several of our computersand have experienced no prob-lems: all worked well. It is prob-able that the problem lies in theprinter connection of your com-puter. In modern computers, achoice may be made in the BIOSbetween standard mode. EPPmode and ECP mode for theprinter port. In many motherboards the standard setting isEPP+ECP. When in that case theECP or the EPP+ECP mode isselected, the circuit does notwork. You will therefore have tocheck the BIOS settings andmake sure that the EPP mode forthe printer port is selected.

pc sound card asof analyser(March 1996)Dear Editor-The 'PC soundcardas AF analyser' uses the soundcard present in the computer. Towhat degree does the quality ofthis card affect the test results?

I have a simple, inexpensivesoundcard and have been advisedthat the output of this card con-tains steep -skirted filters to sup-press any interference causes bythe PC power supply or the carditself. This is manifested by the factthat when I use a tone generatorprogram the peak values of thehigh -frequency signals start drop-ping from about 6 kHz. Are suchfitters also used on a card like the

Soundblaster 16?On asking several dealers trad-

ing in such cards, I could not getthe right information because thespecifications supplied with thecard do not include this. Cardsfrom Terradec. I understand, aresuperior as regards the audiospecification to SB16 cards fromCreative Labs. Can you give meany advice as to which to obtain?

The second question I have is:what can be done to suppressinterference and noise signalsinside the computer? For instance,does whole or partial screening ofthe soundcard make sense?

J.W.

There are, indeed. appreciabledifferences in quality betweenthe various soundcards on themarket. Inexpensive soundcardsoften have a poor frequencyresponse which rolls off verysteeply at both sides of theband. If reliable measurementsare to be carried out. the sound -card used must have a wide, lin-ear frequency response and, ifat all affordable. low distortion.We cannot advise on which tobuy, but suggest that you gleanthe tests on soundcards that arecarried out from time to time byvarious computer magazines.

Soundblaster cards are gen-erally of good to very good qual-ity and, therefore, normally agood buy. What is importantwhen such a card is used incombination with test softwareis the protocol by which the cardprovides its drive power. ManySoundblaster-compatible cardssimulate (in DOS) an old 8 -bitSoundblaster card. Test softwarerunning under DOS that require16 -bit precision cannot copewith that. So, make sure that youuse a genuine Soundblaster card(or an OEM product with a Vibrachip).

Screening the card is a goodmeans of excluding externalstray interference and noise. Itdoes not reduce such interfer-ence on the supply lines. how-ever These can only be avoidedby locating the card outside thecomputer and give it its ownpower supply.

460Elektor Electronics 5/97

SWITCHBOARDSwitchboard allows all PRIVATE READERS ofElektor Electronics one FREE advertisementof up to 1013 characters, including spaces.commas, numerals. etc., per month.

Write the advertisement, which MUSTrelate to electronics, in the coupon on thispage; it MUST INCLUDE a private telephonenumber or name and address: post officeboxes are NOT acceptable.

Elektor Electronics (Publishing) can not ac-cept responsibility for any correspondence ortransaction as a result of a free advertisementor of any inaccuracy in the text of such an ad-vertisement.

Advertisements will be placed in the orderin which they are received.

Elektor Electronics (Publishing) reservethe right to refuse advertisements withoutgiving reasons or without returning them.

FOR SALE. EPROM programmer and agreat deal of hardware add-ons for aBBC computer. \Vrite to Robert Serow-son, 6 Bolinbrook Road. Macclesfield.Cheshire SK19 3DJ.

WANTED. COM3X01 Twinax controllerchip: please contact Indrajit one-mail:multiaserverindo.net.id

FOR SALE. 1 Mbit EPROMs. £2 each.Phone Andrew on 0131 556 7181.

WANTED. Sage Audio Supermos 2modules. Desperately needed. Phone DBell at 01656 725319 (South Wales).

FOR SALE. WEKA Electronic RepairManual and Modern Amateur Electronic

Dark -room timer(October 1996 - 960086)The proposed stop scale for thetimer (Figure 5) should be turnedaround because the delay timeincreases when the control isturned clockwise. Also. the valueof C1 is incorrectly given as 1 pFin the parts list, whereas the cor-rect value is 1.8 pF as shown inthe circuit diagram.

Matchbox BASIC comput-er as data logger(September 1996 - 960065)Owing to a text conversion error,all underscores in the names ofvariables have dropped out of theprogram listing shown in Figure 4.The correct variable names areLOG_MAX, START_LOG,COM_CHR, LOG RAM,LOG_DATA, READ_MAXIM andDUMP_PTR.

Also, The compiler is unable toprocess the lineWHILE DUMP_PTRG MAX DOwhich is best replaced byWHILE DUMP_PTR GMAX DO

Manual Both plus two supplements:£20 each (E40 new). Write to W. Allen.47 Westthorpe Gardens, Hendon, Lon-don NW4 1TU or phone 0181 2036023.

WANTED. Details on radio data systemencoders. circuit diagrams or w.h.y.Phone Paul on 0976 725 684 or e-mail106004.2306

WANTED. Someone to finish RF pro-ject. Willing to pay. Phone Paul on0402 742744.

WANTED for Casio keyboard PT -50.RAv1 pack: also TA -1 interface plug-inmodule required. Have tried every-where - please help. \Vrite to N.H.Hill,179 Mersey House. H.M.P. ChanningsWood, Denbury. Newton Abbot, DevonTQ 12 6DW.

FOR SALE. Videocrypt decoders TypeS\A1, price £10 each plus postage.Phone 0118 970 1163.

FOR SALE. Tektronox Logic AnalyserModel 7603+DF1+7D01. Has no podsor manuals, but believed working.Price £295. Phone Mark on 0181 7617259.

WANTED. 2764 EPROM (programmed)for MIDI -to -CV interface from ElelctorElectronics January 1991. Phone Larson +45 4353 3218 (Denmark)

WANTED. Someone to build TV signalprocessing project. PCB and most bitssupplied. Willing to pay. Phone Ron on0402 742744 or 0976 895273.

WANTED. Late Labcenter PCB draw-ing, software PhoneMark on 0181 761 7259.

Motor controller for R/Cmodels(February 1997 - 960095)The text incorrectly states that Diand D2 are not required for unidi-rectional mode. This should be D1and T1. The penultimate paragraph

on page 17 and the first completeparagraph in the right-hand col-umn on page 18 should beamended accordingly.

68HC11 Emulator(February 1997 - 970008)The correct name of the Talker foruse with a 5 MHz crystal isTKAXTS_800 (inset Talkers for use

with the emulator, page 25).Contrary to what is stated underthe Applications examples, FAQsheading, the Hi -Tech compiler isnot in the M11DISK\UT1LI\ direc-tory. Users having access to ver-sion 7 of this compiler may.however, use SYMWICE.EXE tobuild a small high-level debugger.Likewise, the SYMWICE.0 file mayhelp users of other compilers orearlier versions of the Hi Tech

Send this coupon toElektor Electronics I Publishingi

P.O. Box 1414Dorchester DT2 81'11

England

B ock capitals please- one character to each box

ELEKTOR ELECTRONICS 5/97

Name and address MUST be given

FOR SALE. Low-cost PCB drill -stand &UV lightbox plans. £ 2.00 each. Writeto R. Hammond, 34 Gould Firm Lane.Aldridge. West Midlands WS9 OLX.

compiler. SYMWICE.EXE alsoworks for the WICE emulator.The text In the latter case, ports Band C... (page 23, third line from the

bottom) should be corrected to read:

In both cases, ports B and CThe TL7705 will switch at a low -

supply voltage of 4.5 V, not 3.6 Vas stated at the top of the right-hand column on page 24. The ref-erence voltage is calculated from:

Vrei (R2+R1)/R1 =2.53 x17.8/10 = 4.5 V.

Simple inductance meter(February 1997 - 970009)In the circuit diagram on page 32,diodes D2 through 09 should beconnected to K1 pins 2 through 9,not pins 1 through 8. The layoutof the printed circuit board is notaffected.

Copybit inverter(January 1996 - 950104)The input stage around gate ICiamay start to oscillate when the opti-

mum sensitivity is reached byadjusting preset P1. This spurious

oscillation may upset the normaloperation of the circuit. The problem

is remedied by fitting a 47µF/25Velectrolytic capacitor in parallel with

G2 at the track side of the board. The

relevant connections should be kept

as short as possible.The settings of the three presetson the board are determined to alarge extent by the quality of theapplied S/PDIF signal. The settings

are, therefore, dependent on thedigital signal source.

Icr meter - part 1(April 1997 - 970028/1)Some unfortunate errors havecrept into some text and the boxon p. 32.In the 8th line. centre column,102/105 should read 102//105.Zaur in the 9th and 12th linesshould read Z (where dot is thedevice on test).

In the formulas in the box, 2nishould read 2ni in all five cases.The first formula should start:Uicosfi = , and the second for-mula: U1sinqi1.

Elektor Electronics 5197

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ed Heidi box 89.75Speed Regulator for Model Trainsf963113 Catt--ewas se!

subject change without prior notice, exclusive of(81W) and P&P. E 8 0. E. Private customers in EU countries add 81W

(soles lox) at 17.5%, then P&P.Compact AF Owe of Aspfifier0970043 Pats or!.bcotutli

Optiria-conild nap (Orallef920031 Posts rid colts 85.00

eat ;Into ki 69.00*Jailor to void Fridgeid Te ane

P&P: Airmail, recorded delivery. Europe: KG 15.00 for weight to lkg.sit

tut_ parer sooply 329.00 Fins 101Y113 18 _50n1mgi enc.:4 CO3---xurts acrid t.,..-. 2150 Outside Europe: NW 15.00 for weight up to 150g. Extensive orderingPins- GT700101 34 95012002.3.1 34.95S4aterl /6.71 17 50

1010173 21 33

Ftl Clothwawa T(14 1 23

Pratt 31W4'3 i.csL9325259 495LIA35(7 11 95

info supplied with catalogue. Please ask for a C -I orderform.

VISA - MASTER - ACCCESS - EUROCARD ustri.evms

Get out of a pickle -

get into SpiceAge!

Hands up all who have beenthere? A great idea turns intosleepless nights: getting onething right breaks somethingelse...

Some circuits require the refi-ning of many interdependentvariables. SpiceAge provides avirtually limitless inventory ofcomponents, signal functionsand instruments with facilities ,

for sweeping values, with amand fm through arbitrary func-tions. It can guide you to a solu-tion that could take much longer 41

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SpiceAge up your design without burning a hole in your pocket. Prices from just £85 + VAT to £695 +VAT. Friendly technical help comes free (dreadful puns optional). For a demonstration kit and details of our other and thirdparty support programs (includes schematics, PCB layout, filter synthesis and modelsynthesis), please contact:Charles Clarke at Those Engineers Ltd, 31 Birkbeck Road, LONDON NW7 4BP.Tel 0181 9060155 FAX 0181 906 0969 Email 100550. [email protected]

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1.17110tVg.tv'T

62 Elektor Electronics 5)97

Component sets to ELEKTOR ElectronicsWe are a mail order company and menu -factoring parts sets dedicated to ELEKTORsince 1985. 'The following sets are Inclu-ding all required components :

according to the componets est.fit on ELEKTOR PCB.In high quality from major manufacturerELEKTOR-PCB/software,IC -sockets

The sets included not descrotion. mainstransformer and enVosure

970021 W.decano imete.encosure E440 o 0\0.! E 48 95

970028 LCR-meter £157.60970028 enclosure -set £ 42.91970041 Long distance IrDa E 38.89970043 Compact 50 -watt audio amplifierInd heatsink w/o power supply 66.71

ECBMINEW.1.0 re-V:77A.960112 Digital thermostat £ 57.33970022 2 -wire domestic alarm system

incl. enclosure £ 41.00970031 OptIcatIcoax converter E 17.22970036 Universal power supply E 12.58

:::.1112FAE27.93960098 Electronic fuse

970003 Battery -operated AF-sgnal generator £ 22.03

970008 Battery simulator970010 Eprom programmer £ 34.83976003 Software £ 14,85970037 uCcontrotled mixer -board £ 74.9611raMlitreaienn980094 Battery -operated AF -amp. £153_55

UC 202 enclosure E 26.28960095 Motor contr. f. RtC models £ 33.42970007 Minl LED running light P. 5.72970008 68HC11 emulator £ 78.67970009 Self-inductance meter £ 21.05970015 Sceak;ng doothei £ 24.55

960089 f.',d-g e se..tcn r :ase £ 13.'2960100 /.facn eto-fied meter inci.case 22.63960113 Speed regulator incl. enclosure

aro knobs £ 29.55

STE

970001 Monitor to guard fridge tempratureenclosre £ 26.01

966022 Small workshop disc £ 10.00976003 Software competition £ 15.00

:1980068 RemotecliniiOlby visible light

ivro case, battery, brass £ 23.18KM 14 enclosure £ 2.35960082 Guitar -effects switch £ 35.79960098 RS 232 data aquisition card

incl. software 956508. 956018 £ 39.42960106 Primary -battery refresher £ 24.51960110 20 -bit A -D convener

incl. mains transformers £ 169.03964010 Radio failure protection £ 6.88964031 AC-mV-adaptcir incl. case £ 10.96984062 Electrically 1eot.12C bus P. 12.43964070 Mains voltage cleaner £ 25.49964079 Battery trick_ LED inci. case 8.82964082 EMI tracer P. 17.57964088 Strobositop f. motorcycles £ 24.38984089 Capacitance comparator 11.62f;' 7 .Gain 50 Watt AF-ampilfier

w/o power supply Incl. heatsink £ 22.48960087 Noise -generator each: £ 10.42-A aircraft -B helioopter -C steam-engine980105 816 -programmer inc1.9.66018 39.12960107 WA -Interface wid option

incl. enclosure. software 966020 £ 32.63950107-0 Parts 'optionally' P. 3.76960109 Headphones amplifier E 12.03ilea,a960071 Putty crystal

former and tin-plate frame £ 21 92960075 Mini metal detectorinci.M1 and wire wio search coil £ 20.04

960076 Video test chart generator Intltransformer, modulator, software £107.73(moon Mini flash programmer incl. Disk

966015 and test socket £ 36.32980088 Dark room timer incl. transformer

and enclosure E 430 £ 32.31980091 Electric -bulb tester £ 10.22960093 Sampling rate converter

inci. 958511 4111. X1.33.866111 hi £102.41

960010 [iota! minimax thermometer

Stippler-ElektronikInh. Georg Stippler

P.B. 1109 D-86656 Bissingen / GERMANYTel. and Fax -49 9084 463

eMail [email protected]

incl. case HE 222 £ 43.42980051 Power limiter incl. heatsink £ 11.60960063 Stand by unit incl. transt. £ 31.99

Enclosure SG 433E £ 13.19960085 Digital compass inci. case £ 52.99960090 RS232 Interface for ICL 7106

incl. disk 966018 and ICL 7106 £ 21.181:4NEWEAT-'264f 'Ora Prfriginan930095 Solar -charging regulatorincl. case (metal), heat sink, £ 35.60936010 Symmetrical power supplyincl. mains transformer. heat sinks.

switch, insulated terminals £ 16.18936024 Harmonic distortion meter

1% -capacitors, enclosure £ 27.56936037 Grid dipper

mcl. enclosure typ 1590C. moving coil.knobs, screws. witnout corm £ 61.84

936039 Continuity tester £ 8.34950123 Sound -to -light unit £ 30.90964016 Lambda probe monitor £ 9.14984020 Miniature power amplifier £ 9.08964032 DVM as phase meter £ 14.21964038 Joystick change over,ncl. enclosure HE 222 £ 15.94

964039 50 MHz decibel-milliwatt meterinci. case 159013 £ 96.92964040 Battery capacity tester £ 18.34964076 Video fader £ 31.03984104-1 Single -chip AF power amplifierinci. heat sink SK 42175 48.03

964092 Inexpensive AD/DA converterscte.a'e 95.5CC9 E 1931.

950126 Ke,:daro s,..ap lc' PC E 11-92960005 Puslismeter incl. E 430 £ 26.17980022 Burglar deterrent lighting £ 14.02SG432E Plug In PSU-case £ 13.32

960035 'Stop that barking'inci. enclosure £ 10.75

960072 23 an ATV amplifierIncl. tin plate case £ 30.54

960073 Active wer buffer £ 19.78960077 Flesh-Eprom programmeremulator without Eprom £ 63.97

960077-K Flatcable ÷ connector £ 3.2229F010-12 Rash-Eprom £ 6.81

WRINENNUMWASIVARM960049 Suthvoofer out LS.

incl. components filter, amplifier, trans-formor, heat sink SK 47/100 £111.98Power supply £ 80.11SPH 300 10 (Weight 5.5 kg) £ 51.60

960033-1 Logic analyser : main board16 channel Incl. of all parts as probedips, case RE1, mars. disk £104.27

Extension board Without PCB Incl. ofsill parts as IC 21, probe clips £ 48.91

960033-2 PCB extension board £ 15.90960055 Mains voltage monitor

Incl. transformera, case E 411 £ 29.51950098 Digital VU meter £144.51

Enclosure LC 750 £ 12.09

950120 U2402 battery chargerincl. transformer. U2402B-C £ 31.91

960043 Water leak alarm incl. case 9.34960052 Centronics interface

incl. software 960052 £ 21.98960053 PC soundcard- AF analyserincl. case (metal) without software £ 11.39

966001 Software AF analyser £ 24.35

You also get these setsb our native dealer :

England :nyin errtny 06ervices

20 Orchard Rafts CrescentWingfield, Rotherham S61 4AFITelrFax (÷44) 01709 560650

Indonesia :PATTRA ELECTRONICSJI.Pagarish no.184/87 Bandung 40262JI.Oulatip no. 67 BandungTel. /Fax 022 433179Israel :Elektorcal Ltd.P.O.B. 41096 Tel Aviv 61410Tel. 03 6591991 Fax 03 6596244

Sweden :PB Elektronik ABBox 5516 S-14105 HuckfingeTel. 08 7100370 Fax 08 7401806

Prices. ordering & char.es:AA prices In £ without 15 % VAT (51W). stoners inside EU add price -I- -EP V T 15Neese send orders only by mail or fax. After we received your order you w8 get a prigorma-invoice with details how *pay. Please do not send cheques or giro transfer In advance!Credit card : Please don't forget card number, expiry date and signature fWe accept : Ameran Express. Diners Card, Eurocard. Mastercard, VISACharges for P&P (air me)rrside cr EU : £ 4.00 up to E 25. cuacie of EU 8 up to E 50.00. (Depends on weight)

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Baylin PublicationsNEWBLACKBOOK 5EuropeanScramblingSystems, CircuitsTactics &Techniques. ByJohn McCormac.Smart cards, piratedecoders, forhackers.5th Edition. £34.World Satellite TV & ScramblingMethods. By Baylin, Matiox &McCormac. For the service engineer.

Digital Satellite TV, Theory,£29.Installation & Repair. Dish theory.cables, site survey, polar mougtadjustment. NIPEG & Internet L36.

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Outside Europe +30%.

DIGITALSATELLITE TV


software far electrrnicsQuickroute 3.6 PRO+

Quickroute is a modern,powerful and easy to use

program for the designof circuit diagrams andPCB layouts. The pro-

gram, which is stored ondisk as a compressed

file, runs on any PC witha 386 processor or bet-

ter, at least 4 MB RAM(8 MB recommended)and 5 MB of hard diskspace. The program is

Windows 3.1 or 95hosted. This article dis-cusses the PRO+ ver-

sion of Quickroute, whichis aimed at (semi -)profes-

sional users, offering anauto -router and file

import and export func-tions. New for Quickroute3.6 PRO+ is the ability to

accept plug-in modules,the first of which were

launched recently.

Quickroute consists of two programmodules, one for drawing circuit dia-grams ('schematic capture') and onefor designing printed circuit boards.The schematic capture program isdivided into four sections (see above).The menu bar at the top of the screengives access to a large number of toolsand functions, which may be selectedby mouse clicks or keyboard shortcuts.Many of the functions for editing andarranging objects, as well as the oblig-atory file functions like New, Open,Save and so on, are integrated in thesymbol bar which appears directly

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below the menu bar. The two bars atthe top of the screen provide a veryeasy-going user interface. The status listappears at the bottom of the screen,indicating the cursor position, magnifi-cation, and the active circuit layer. Italso shows condensed information onthe meaning of the symbol or functionat which the cursor is pointed. At theright of the screen is the active library,which indicates frequently used objectlike component symbols, connectionsor texts. The largest part of the screenis occupied by a window in which thecircuit diagram is created. This area hasthe usual vertical and horizontal scrollbars. Furthermore, extensive optionsare available for moving and display-ing the working area.

Quickroute includes a range of sym-bol libraries covering more or less stan-dard electronic components, and thesemay be extended with your owndesigns. The PRO+ review copy wereceived came with two supplementaryplug-in library packs: CMOS & SMTand TTL & ADC/DAC. Further packsmay become available from Quickroute,and (prospective) users are advised tocheck the Quickroute web site athttp:/Avww.quickroute.co.uk for avail-ability of new additions and releases.

The component symbols are pickedfrom symbol selection windows,dragged and placed onto the 'con-struction area', moved if necessary,copied or deleted, and then linked to a

network of connections. All objectshave attributes indicating position,object size, type, value and othersalient details. To edit an attribute yousimply double-click on the relevantsymboL This opens a window in whichthe necessary modifications may bemade.

The component picking phase maybe shortened by moving frequentlyused symbols, along with their attrib-utes, into the working library, fromwhich they are instantly available foruse in circuit diagrams. Finishedschematics and parts lists may beprinted (optionally in HPGL or Post-script format) or saved as a bitmap file.Exporting to WMF or DXF file formatis also possible. A very interesting fea-ture of Quickroute 3.6 PRO+ is its abil-ity to generate Tango, Spice orSpiceAge netlists, allowing these pro-grams to simulate or test a circuit. Alink to Electronics Workbench is also pro-vided.

Having drawn the schematic, yournext task is to design a printed circuitboard. This is done in a window whosestructure and operation closely resem-bles the one used for drawing the cir-cuit diagram. The working area is dis-played as an inverted image, while thelibrary now contains componentshapes instead of circuit diagram sym-bols, and a few extra icons in the sym-bol list. For the rest, everything remainslargely as before.


Several options are available for thedesign of a PCB layout: using manualdesign the mouse is used to pick PCBsymbols from the (working) libraryand drag them onto the working area.The process of placing solder pads,copper tracks, symbols and text ontoone or more PCB layers is basicallyidentical to assembling the circuit dia-gram. The result of the manual designwork is a PCB layout (consisting ofmultiple layers) which may be printed,saved or exported in different file for-mats. The second option (illustrationat the top of this page) is to have theprogram produce a rats -nest. In thisprocess, the schematic symbols arereplaced by component shapes (PCBsymbols), and all connections betweenthe symbols are automatically made.The operation is initiated by clickingon the rats -nest symbol in theschematic capture program, where-upon the active schematic is analyzedand replaced by a corresponding net-work in the PCB layout program.Next, you arrange the network sym-bols until they have the desired posi-tion on the board, striving, of course,to achieve the lowest possible numberof crossed rat lines. After this re -posi-tioning operation, Quickroute offersan automatic comparison of schematicagainst PCB layout. In PRO+, thisconnectivity check is pretty fast andeasily controlled.

Quickroute offers manual as well asautomatic routing of the rats -nestlinks. If you select manual routing, a ratline linking two or more points isreplaced by a PCB track whose courseon the board is determined by theuser The type of PCB track is selectedfrom the Options/Track Type menu.Once all rat lines have been replacedby tracks, the routing is checked.

The PRO+ program offers a pow-erful auto -router, RouteASSISI theresults of which may be seen in thescreendump at the bottom of thispage. The auto -router operates on anynumber of layers, using a time limit,mixed track types, through -contactsand other options, all of which are exe-cuted at high speed. An incompleteautomatic routing operation may beterminated manually, or modified.RouteASSIST even allows individualPCB tracks to be automatically routed.

As soon as a design has been trans-lated into a corresponding network ofPCB tracks, using manual or automaticrouting, Quickroute runs an automaticcheck on the PCB track distances, andhighlights all tracks and solder padswhich violate the design rules set upby the user.

Further interesting and useful func-tions of the PRO+ software include:Forward AnnotationWhen comparing the circuit diagramwith the actual Pat layout, PRO+ not

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only highlights differences, but alsoindicates which corrections whichhave to be made to a PCB as a resultof changes to the schematic. Theprocess is also called EngineeringChange.Copper FillLarge regions of filled copper are notonly useful on RF boards; they areoften applied wherever there is arequirement for additional screeningof circuit sections. Quickroute PRO+is capable of automatically filling thefree regions of a board surface with acopper layer, and still observe the min-imum distance to be maintained tocopper tracks and solder pads.livtorisationQuickroute PRO+ is capable of replac-ing filled polygon shapes and otherobjects by equivalent elements con-sisting of copper track segments. Thisis not only useful with the automatic

RoifAiwev 111

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checking of minimum track distances,but also when exporting a layout in afile format that does not support cer-tain object types.Import/ExportIn addition to the standard formatssuch as Windows BMP, PRO+ sup-ports a large number of file typesincluding Gerber, NC -Drill, DXF, Tangoand WMF (Windows Metafile).

Finally, we should mention thatQuickroute Systems recently launcheda plug-in module called SMARTRoute1.0. Priced at £149 plus VAT, this mod-ule offers an extremely powerful 32 -bitauto -router extension for Quickroute.

(174050)

Quickroute 3.6 PRO+ costs £399, and Isavailable from Ouickroute Systems Ltd.,Regent House, Heaton Lane, Stockport,Cheshire SK4 1BS. TeL (0161) 476 0202,fax (0161) 476 0505. [email protected].

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Elektor Electronics 5/97 65 16\

SOUND OUT OF SILENCEA Life of Alexander Graham BellBy James MackayISBN 1 85158 833 7320 pp; illustratedPrice (hardback) f 20.00Mainstream PublishingAlexander Graham Bell was born 150years ago in March 1847, the son ofMelville Bell, inventor of VisibleSpeech which revolutionized phoneticsand linguistics. Aleck, as he was called,was inspired by his deaf mother to try tocommunicate with deaf-mutes andteach them to spek. While exploring themechanism of speech, sound, and hear-ing. he discovered the principles of thetelephone, arguably the most importantinvention of all time, without which thegramophone, radio, television, intemet,and videophone, could not have beenpossible.

The telephone made him wealthy,but Aleck went on to invent the ironlung, pioneer aircraft, improve thebreeding of sheep and co-found the Na-tional Geographic Society.

The superb new biography followsBell from his birthplace in Edinburghto his studies and teaching in Londonand Europe and thence to riches andfame in the United States and Canada.Set against the colourful backdrop ofVictorian Britain and the exhilarationof the New World, Sounds out of Silenceis the definitive story of one of theworld's greatest inventors.

Dr James Mackay is historian andauthor. Widely regarded as the world'sgreatest authority on the life and worksof Robert Bums, his definitive biogra-phy, Bunis, won the 1994 Saltire SocietyBook of the Year award. He is theauthor of Vagabond of Verse: a Biogra-phy of Robert Service, William Wallace:Brave Heart, Allan Pinkerton: the Eyewho never slept, and Michael Collins: aLife.

This is a fascinating study of a manand his world when electronics wasyoung. A full review is planned for ournext issue.

,MODERN DIC770N4RY OFELECTRONICS (Sixth Edition)By Rudolf GrafISBN 0 7506 9870 51152 pp; illustratedPrice (soft cover) £ 30.00Focal Press*The Modem Dictionary of Electronics isa classic, comprehensive reference bookfor engineers. technicians. students,hobbyists and writers - in fact, in thisreviewer's opinion it is by far the bestdictionary of electronics currently avail-able. It includes practical terminologyfor consumer electronics, optics, micro -

NEW BOOKSelectronics, communications, medicalelectronics, and packaging and produc-tion. Where appropriate, abbreviationsand letter symbols are represented, andtables of SI units and schematic sym-bols are included at the back of thebook.

MARCH OF THE MACHINESHuy the new race of robots will rule theworldBy Kevin WarwickISBN 0 71267 756 9263 pp; illustratedPrice (hardback) £ 16.99Century BookHuman beings see themselves as beingthe superior race amongst all livingthings - and the most intelligent. Yet,advances in robotics mean that withinthe next 10-50 years we will have to ac-cept that our reign as the dominantforce on Earth could come to an end.Computational power will be greaterthan that of humans. We rely on ma-chines for both military and manufac-turing purposes. Advancements in ro-botics, particularly in optical and bio-logical systems, are also speeding up in-telligent machines' abilities to move,operate and be effective in the everyday

r

world. Robots can already beat us atchess, and play music.

Professor Warwick, one of theworld's leading experts on cybernetics,refutes the sceptics not only by ques-tioning their assumptions and preju-dices about what should be consideredas intelligence and consciousness, butalso by revealing what he has achieved,building robots that communicate intheir own language, share experiences,teach each other lessons and behave aswish with regard to human beings -andwarns that future generations will rulethe world.

This thought -provoking book is amust for anyone interested in not onlyrobotics but the future of mankind.

1 -.'Focal Press books can be ordereddirectly fromCustomer Services DepartmentHeinemann Publishers OxfordPO Box 382Halley Court, Jordan HillOxford 0X2 8RUTel: +44 (0)1865 314301Fax: +44 (0)1865 314029

Books from Elektor Electronics

Build your own Electronic Test Instruments (0 905705 37 8) £ 15.95Build your own AF valve amplifiers (0 905705 39 4) £ 14.95Build your own high -end audio equipment (0 905705 40 8) f 14.95Short Course 805118032 Microcontrollers

& Assembler (0 905705 38 6)SMT Projects (0 905705 35 1)306 Circuits (0 905705 43 2)305 Circuits (0 905705 36 X)304 Circuits (0 905705 34 3)303 Circuits (0 905705 26 2)302 Circuits (0 905705 25 4)301 Circuits (0 905705 12 2)Microprocessor Data Book (0 905705 28 9)Data Sheet Book 2 (0 905705 27 0)Data Book 3: Peripheral Chips (0 905705 30 0)Data Book 4: Peripheral Chips (0 905705 32 7)ST62 Microcontrollers (0 905705 42 4)SCSI: The Ins and Outs (0 905705 44 0)PICs in Practice (0 905705 51 3)I2C Bus (0 905705 47 5)

£ 9.959.95

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10-95f 9.95£ 9.95£ 10.95£ 9.95£ 10.95£ 10.95£ 2+95£ 2+95£ 2495

2+95

Planned for publication:PC Faultfinding & Repair (0 905705 41 6) -May 1997The CD-ROM System (0 905705 46 7) - June 1997Circuits for Lasers (0 905705 52 1) - July 1997Matchbox Single Board Computer (0 905705 53 X) - August 1997Satellite Radio & TV Receivers (0 905705 49 1) - SeptemberDesigningAudio Circuits (0 905705 50 5) - October 1997Handbook for Sound Technicians (0 905705 48 3)- November 1997

L

SUS29.50SUS28.00SUS28.00

SUS18.50SUS18.50SUS29.50SUS28.00SUS23.95SUS20.25SUS18.50SUS18.50SUS20.25SUS18.50SUS20.25SUS20.25SUS46.00SUS46.00SUS46.00SUS46.00

-41


Safety requirements refer mainly tothe 240 V mains voltage, but also tothe temperature of touchable partsand fire protection. Most problemsconnected with a mains power supplycan be prevented by the use ofapproved and correctly rated mainsadaptors. As regards mains -operatedequipment, there are two classes ofinsulation: Class I: single insulation,which always requires a three -coresupply cable with earth. and Class II:double insulation, which requires noearth and only a two -core supplycable. Thus, the requirement is alwaysfor double protection. With the enclo-sure shut, all touchable, conductingparts must be at earth potential.Class IClass I requires insulation between themains voltage and each and everytouchable part that withstands aflashover voltage of 2120 V. To preventflash -over, the distance betweenmains voltage carrying parts andtouchable parts must be a 3 mm. Alltouchable, conducting parts must beproperty earthed.Class IITne requirements of Class II are Iden-tical to those of Class I except that thetest voltage is 4240 V and theflashover distance is 6 mm.Practical considerationsA safe rule of tnumb is to keep the dis-tance between mains carrying partsand other parts as large as possible,but never less than required_ Try tomake the mains carrying part as com-pact as possible. Use an approvedmains entry with integrated fuseholderand onfoff switch. Note that the manu-facturer's statement 'suitable for250 V' does not mean that insulationof the switch is approved, merely thatit does not break down at 250 V.If you do not use an integrated entry.use a strain relief on the mains cableat point of entry_1. A single -pole mains onfoff switch isallowed on equipment that is poweredby transformers with isolated primaryand secondary windings.2. An ontoff switch not in the mainscircuit is allowed it the transformer hasisolated primary and secondary wind-ings. and the power consumption inthe 'off' position is not more than10 W. There must be a visible indica-tion that the equipment is plugged intothe mains.

CLASS I

3. Al on off switch is not required ifthe power consumption of the equip-ment is s 10 W or if the equipment isintended for continuous use. such asan antenna amplifier.Equipment not meeting these threeconditions must have a double -poleonfoff switch.Fuses, inductors, capacitors and resis-tors for interference suppression neednot be switched off. It is advisable.though not mandatory, to precede theswitch by a fuse.Never solder mains carrying wiresdirectly to a printed -circuit board: usesolder tags. The use of crimp -on tagsis also mod practice.The mains earth must be connected toother parts that need to be groundedby a yellow/green wire. Pay particularattention to the metal spindles ofswitches and potentiometers: if touch-able. these need to be earthed aswell.Close to each and every fuse, even iffitted on a Pce, must be a label statingits rating and type.One of the side panels, or the rearpanel, must have a label stating theidentity of the equipment. for instance.EE power supply from no. 213. themains voltage, and mains frequency. Ifoperation from ac. only is possible.the label must carry the symbol -. Incase of a failure, there should not beany danger to the user.The temperature of touchable partsmust not be so high as to cause injuryor create a fire risk.All risks can be eliminated by the useof correct fuses, a sufficiently firm con-struction, correct choice and use ofinsulating materials and adequatecooling through heat sinks and byextractor fans. The rating of a slowfuse should be not greater than 1.25times the normal operating current,whereas that of a fast fuse should beequal to the normal operating current_Fast fuses are used. for instance, incase of several secondary windings.but if there is an electrolytic capacitorbehind the secondary, a slow fusemust be used to allow for surges inthe charging current.The equipment must be sturdy:rep-eatectly dropping it onto a hard sur-face from a height of 50 mm must notcause damage. Greater impacts mustnot loosen the mains transformer,electrolytic capacitors and other

TOUCHABLE CONDUCTINGPARTS

(CASE SVITTC.4ES. ETC I

CLASS II

Figure 2. It is advisable, and also practical, to build equipment to ClassII. Important aspects are:1. Use a mains cable with moulded -on plug.2. Use a strain relief on the mains cable.3. Attach a label near the fuse holder stating the mains voltage and

frequency, and the value of the fuse.4. Use an approved mains on off switch; this should not have a

metal lever since that is normally not insulated properly.5. Push wires through the eyelets and solder.6. Use Insulating sleeves for extra protection.7. The distance between transformer terminals and core and other

parts must be 6 mm.8. Use wire with an insulation of_ 4 mm and a core diameter of

0.75 mm.9. There are no special requirements for the board and circuit other

than that it must be secured firmly.10. The earth of the circuit may be touched because the mains trans-

former is double insulated.11. Although the enclosure may be a metal one, since tire trans-

former is double insulated. a plastic one is preferred.

important components.Do not use dubious or flammablematerials that may emit poisonousgases.Shorten screws that come too close toother components.Keep mains -carrying parts and wireswell away from ventilation holes, sothat an intruding screwdriver or inwardfalling metal object cannot touch suchparts.TransformersFigure 1 shows how a transformershould be connected in line withsafety requirements. Although double -pole °Waif switches are shown, these

......, ci '\-,) /-.)-'7'

,S,11 ZIT I ;A 1-.

vim} GLASSE

lWJ TRANSFORMER

C.,`4-°0aM 11.

5 '''G4 -m2=15ti V406, LP

',....--0 -.0 0 1-0-.,. 04-p2

-C

a, (36'6

*Et:CLOSURE

Figure 1. At the left a Class I equipment powered by a double -insulated transformer. All touchable.conducting parts must be properly earthed: outputs need not. At the right a Class //equipment

also powered by a double -insulated mains transformer.

may be sinale-pole since in bothcases the transformer is a double -insulated type. It is as-sumed that thetransformers are short -circuit -proof,whence the absence of primary fuses.If the assumption is not true, a primaryfuse must be used. The figures and

indicate. respectively, whether sin-gle or double insulation is required.

Working in safetyAs soon as you open an equipment.there are many more potential dan-gers. Most of these can be eliminatedby unplugging the equipment from themains before the unit is opened. But,since testing requires that it is pluggedIn again, it is good practice (and safe)to fit an earth leakage switch rated atnot more than 30 mA to the mainssystem (this may be fitted inside theoutlet box or multiple socket). Earthleakage switches more sensitive than30 mA need to be used only if theleakage current is expected to remainbelow 30 mA, which is rarely the case.

These guidelines are drawn up withgreat care by the editorial staff of thismagazine. However the publishers donot assume. and hereby disclaim anyliability to any party for any loss or dam-age. direct or cvlseguential, caused byerrors or omissions in these guidelines.whether such errors cr omissions resultfrom negligence, accident or arty othercause.


L IXa a 1.7CgGENERAL

: :-nres (PCBs). sail-adoreVie front panellois. ROMs. EPROMs. PALE. Gels. 1,4 ,...,..4.roeus Apa*Skates tor prolcU *hies lure appered in POWBecirous mitt he ordered usns the Order Po-ro orratilopposite. The toms may also be used to eau bootstollste ceourres carp It no product description is Ohm Ono the 'gent is arali-do0 Otis! thud bard (PCB).

rams rot used Owe nay as be rralaL4 Nil ore. The artwork for rraikto a PC8 strict it ra nnieie

r44874144c 4110-1941 we Brews Serrets rosy be teatin =Meryl st:*

MOM, GALS PALS. (61K0s. VECris PICs rd etenorxectroSes se suppled readi-progretred

Prices vd deco description suefect 10 change Ireo..besrers reso-os the VII to cis '2e iris e7trz-ncr.i.r Prices led itto description those kereuprise* locals precise inns. E L 0 E

Article titleor item

Order Pricecods E USE

SPECIAL PRODuCTIL1.-2; LicrRavc s VOLUME 1996 OM COLLO* Tv

:s W-artalot norba; cio-ra 37 5: .f.-3WHE r...71m71:-753 r,:-alcr,:- 555 5-3 cr

IREA70R ELICIROWS REM TRACER 1235-1935.(m 3 5-rct Fox,/ 064) 26.53)5-1 10 CO 0690* reduced or0.e0.8 siescrtes Normal puce Ell 75 ce

OSS19 00ELEATOR WC/WKS HELP WUC...^.-rocrest =Ass brid decoder sotrrire Dt35.58.1 dm 966022.1 10.00 20 00REKTOR ELECTPIYXS SOFTWARE COMPETITION1996.1701 CO -ROWCorrcatben at se orde-rri-e-roerthesctere 547ilied.45 d. nottesUd try E7 7r 97E0334 15 75 31 50

MAY 1997Lx0-05trce bOt Ls* K.8 6362051 970341-C69051 asy 976503-1

Adread LCR Ikeer-PCB. GAL E4404 970326-C- GAL 221110 976506-1- ERMA 275512 9705071- fort ore tot 9700284Weeread WItrat lieu 970031-1C01 -W Pew knottier 970043-14-01,id Lox

APRIL 1997Efotr Tram-PCS &PSCI6C54 9 -M112 -C F1C7EC54 only 265501-1

JR-Cor0sie1M;ser Boars:- PC8 a 515.27258 970037-C-ST621256 -.-? 976502-1

F58 o- 97E037-1- Sanwa -7 r:07/ (A.0) 0/0006-194C-oor::: r:Tre MITTSAWTI-Pca 5 = i.:64 970022-C-F1C16CE: 976501-1Get-eli-Puo:-..se Pennih,

CrJ4-,z-Ccar-VCo77.-Mir 97570311

MARCH 1997En -1018 Ph_PCB- Oyee vil:easeaemert-Ocented AFSvatGerergor

FEBRUARY 1997Sarary-Pore '?'e5.-o-fe157,57 Ccrooler tor R. -C

- PcS P.C1 6984-PA 16554' 4-46671511 En.titar- PC3 rd 041.V,-7 0.44-erz -crZySea bp.-Xce PCS 4,-.1 Carle- 1:391:1e crsr

2525 505017_50 3500

62_50 1250123.50 53 007.75 1551

1350 27 CO21_50 430019 15 39.50

Pus arMs

3250 65_0022.50 4500

3275 651024.50 44001015 20_51

6.00 12.003

30.50 610023.50 4700

970336-1 553 17 00

7.00 1400

970010-1 15.75 31.50on CO-ROtt no 97E033-1

970003-1 1000 20 00

960094-1 34 25 6850

960055-C 22.75 45 50910,1 19.00 3350

970005-C 2600 56 Cd976002-1 11.25 2250

970039-C 15.25 3050975001-1 8.75 17.50

1997

PAST ISSUESFast issues. d 1,aiiszte. should be ordered trimWorldwide taliscriplios Unice Ud. UM 4. Gibbs ReedFun, Peskley Road. TICEHURST TN5 711E. Eneland.takektee (+4411589 290657. Itt (+44)1560 200616.Prices of pssr issues hum! .14.4,..get are Decerber).ire-kielog Kstice for sirioit Capin. are £3.20 (UDC 026Ekt): £350 turbo rota cosi& t/KL £3.75 (air marEurope): £4.50 (shwa outside Europe). Prices of past:ft/August and Detrcher isr..es, Incirding onstage Itsrge C90445 ere £425 (1.00. £4.50 (mere otol cutsiX

64.75 (dust! so 59 Okla; oids*hope).

PAST ARTICLES

For ktorrecri ca past recles. pkes conz ad E...rista26 44771410.430r1 Me in 0c,-costee Ile ephocz 01305255995: lee 25006. use estlorAgo.7usesuer cork

Artie* Vileor Hem

Ordercode

PriceC USS

Ti:74-7; Clost-e: 970015-1 10 50 21 50

JANUARY 1997Do-Ve Satoh 990029-1 7 00 14 00Lknre.ic-Fa(d Mete 960100-1 CM 1700Steed RelevealvIkO5

5113.1 393 17 03Move to Gerd 1114-e.TNroBatire 970301-1 800 16.00

DECEMBER 199620-45: 4.0 conere 960110-1 2275 4553Rite i:e CorVe uy VetelFyt 9600684 11 03 2200Phrrorifry Reteer K,010.5.1 11 25 2250RS232 dam atq.nstco card: PCB. PIC Lod Odic WiT-/.5-C 33550 71 00 &ea* 969319-1 725 1453 PsC 16571 coy -9055054 24 00 46 00

H3.-43-04;

Ikr0C74 V d_,-ra &....ks 955021-1 403 890Bectaty fsdVo i2C b;:s 025 1950Ce .10 Pal 964116-1 1550 37_00

VU Oge Corer 951070-1 1025 2050

NOVEMBER 19985762 Prolerrver- PCB ra ter PC8 cal- 60. odyBar --041 1.4e.roC so V Sus

960155-C960105-196631E-1

956021-1'*0109-1960119-1

1673 33.5012.75 2550600 1210

400 800625 12_50

oo 1600

960107-C 1525 30.50Te,rc teem 56E0201 8.90 1610

960087-1 725 1550

OCTOBER 1998Vd40 Test Ch -1 Gera.rder- PC8. MO_ EPROM rdEck 9M076 -C

- EKD EP1471102 9E-55074- EPSOM 270340 966507-2 MU any 96»0111

Stri Rash- PC8 ntl software (WA) 960076-C- &twee add (ask) 9660154itri ilY3 Omct:A 993275-1ONtreirt Timer 991066-155-7 p.12 Ram Commlv- PC8 3,4 536.2110 96CCMC- 5762110 )(C2) 956511-1Tt rryC,sIEOsee 40/714ac4v-977.b 95x0091-1/717.0:74,1.r.,419 Pmg

101.110 er 15. 9560134

SEPTEMBER 1996Ekte more: tr PCB rd 5162110 960010-C- 5762110 0C1) 956515-153-Otr.r 11-4 Ice TV E.o.....,i96COM-1

Correses 90065-185232 tertece tor 4.1)ConieW /CUM

7967 Is conco Ta co24.50 49007.03 14 50

21.25 42.5012.25 2450530 11 00

11:75 2150

2075 57501950 39 0012 75 25.506.50 1200

750 14.00

27 75 55101950 39 CO1200 2400750 1500

Article titleOr item

Ordercode

PriceUSE

5:th-us CA 5-7

JULY'AUGUST 1996

6_50

911.95950

16_50

5.0012_25

1200

390390

19.003300

16 E02430

Sgrirt-97za: POAS &S,Wolf ;3Sord4o-U0-4' Olt ;1.723-150-179-12 154 361039-1PrtristA 2.2tef CaMti1.14, 954040-1Veto Eke 954076-1serpermle X3J 04 Ccnitrea-PCii 954092-1 tea

sotwre en Os. 964204 700 1400SoOe-Chts AP Pose 4.79 .954104-1 5",a 12 50

JUNE 1996Pan EPFrat Provrrner:Ero r- 6-A 965 77-C 3300 66 00- rise arty E66017-1 1610) 32.03

Efibord Sew 1x PCs 550125.1 700 14.00Stop t.m. 960035-1 5.50 11.002.3om ATV crearrVe 960072-1 7 50 15.50.PLiseeter 950315-1 10 25 20 50eine,r13eetnt4l Liortio 950022-1 725 1450

MAY 1996Malone Chess MCI:-P68 87551 (9.M.15-1) 950097-C 41.75 S3 50- Val 94E645-1 00.755 6150

Ehoissi VU trete/ (2).- P58 + EPROM (9.8..11950698-C 35 00 7200-EPROM 2/5512 946646-1 17 75 35.50Salowid Saxe &brae (3)-PC8 960049-1 15.75 3350

%tun Vetat7to^...e-. PCB 9535e571 725 14.5064-CA5toN 1494 kiehser.- dtis1 P56 ea a E.4.05 960313-C 69.75133:°0- ti,l 4191016 966536-1 27 50 55.00- dot.1016 966535-2 2750 5503 Odk 114500.5) 966010.1 7.00 1400 cdereco PCBs 13-77-11 960033-2 17.00 34.03- scza n 40. 0.511016 956E06-2 27.50 55.50

APRIL 1696024026 Eatery aarob* 950120-1 1200 24.50Corzolcs Llerlam PC9 , (9501.08-1) 1525 3250- Dist tWinss) 966505-1 5.010 12.03PC-CoTra, AS kV 's& 121:- 5917,714e. r4V. 966001-1 26 00 52.00

MARCH 199650.1zu

(4 on 1 Mare) 950116-1 1000 20513PC-Con/71,e: 4190-xce,-.... PC8 + 960:60-C 7150 55 00- PC 16C-34 955505-1 22 75 45.50

FEBRUARY 7996SAW tE.F.E.`-P58 -. 'Imam (96503. -1I960039 -C 28 25 5550-EPROM 956503-1

hoetace tor Cerocats10 25 20.9

P-nrtPC8 60. (946202-1) 953063-C 2025 4010saran sareire m 555 946202-1 1225 24 50

Pnorre thew 950124-1 800 16.513toy Roads Woo:. y 0633L 1 503 1210

JANUARY 1996SE.C4M-t3-P41. Carets 950076,2 29_00 5E C3Ccorpt VAertg.- 950104-C 44.00 55.00-1.74CH GAL 9-7s513-1 3525 70_93Passne Car, art Tester- agon-1 1315 27_53- Front per Pal Piet FYS$Sd

DECEMBER 1995

Article title Orderor Item code

PriceC. USS

19-F tealpyre IrOtIV 953064-1 500 10.03Ds;zerde:- F59 65X60-1 12.75 25.50-ELI 12019) 956511-1 1050 2000- GAL 156122V101 956512-1linfET roar

rrceer PCB 930102

01 75

12.73

2350

1550Cop ,12v- PC6 wzr s55504.1) 450054-C 40 50 81.00

NACH rC 055504-1 355) 73.00o-Ci..a? 95E095-1 5_25 10.59

JULY/AUGUST 1995&ro.*R71-,..m.tto ob-ei. .q...0023-1 7 50 1503

01'29 950:65-1 575 1350Fist craw kr NCO 0,Mles-PCS smarm (9565 -2) -1i950376. -C 2275 45 50- STRT20 953509-1 14 75 29 50

S -ink 113 Cara 0540744 11.50 2150

JUNE 1995Fultszo gmb-rx-Fla 95C '065-I 2430 5900- Front peed foe 950066-F 17.75 35.50Dectob.: sardVass-

PCif 075751 (946647-1)950052-C 26_25 5210- 57C751 916517-1 17.75 35.50X=10 coed 950.0.1 4 75 9.507s4 aft iber 9503174 10 00 20.00

MAY 1995140; ra-leer-PCB r EPROM (956507-1)940020-C 3425 6830-EPROM 956507-1 16.75 33.50

PILVC.ti sr for 6.7 Loatsects Res bars. PCB EPROM t956644 -11955603-C 2650 53 00

EPRrAl 9465444 1450 29.00Prwri-cl&e sue sat orerrzr-- PCS + ask (9550054 ) 951604-C 19;0 39 00 o:c6S scererue on on 993305-- 1 1225 2450

144 ton-ro..a.111 2400-P513 + ST62115 (156556 -1)9M051 -C 25 25 5059- 5162715 956605-1 18 25 36 51

APRIL 1995Sul 9.551351 9 25 15:0FLneX.' w.eratx. PC8 r troriparei tce 991144-C 21 75 .0.330-KB 955044-1 11 00 1250- Fr= prei irs 95(044-F 12 50 2550

5`13mon wreak pca 8751 4. CAI M5015 -C 50 75 131 53-5751 9565-33-1 35_25 7050- F PC CV. 95E034-2 375 793

1 3-1511 PC'W Stop* 950106-1 925 1650Tm Tar 64-'4

PCS hr.re. ore 1:4 950016-C 30..50 6100PC8 orti 950016-1 17.25 34.51Frontse tee irer 950316-4 1375 27M

Smart Trard;mx TesL.n. PC8 + (656502-1) 550114-C 4425 63 50- PC 1E071 056500-1 35.50 7100

Lr.p.,5 PLO Sy +r PCB + 87CT50.51 + C44 950093-C 4450 69 00- ucman 956514-1 2430 49 C*

556015-1 10.00 20 03COrtrot 4vtsat.a163kAttire Late--retT 954599-1 9.50 19 03Dauer 954500-1 5.75 1150Ar..A5 (rate 800 1600Tr ray PC-0471-%77-tri 954X4 11 75 23.53

NOVEMBER 1995Pi? Prxms..z.-PC8 B7C51 i3sa05-11 950072-C 5475 10150 07C51 956605-1 3075 51.50Re nose 950069-1 1075 2150PA 300 case arre.45er 9500921 1975 39 50.4-102o910 951112-1 00 1403Os.:4cs:xe umors 9501154 27 75 55.93

OCTOBER 1995541040-&Nr.7-

- PCS_ 8I591. t rklOuta. Reference Cut 950011,C 59 25 118 50

-57551 9565084 43.50 67.073- Course is.e.ie. (Oos) 958M-1 11 50 23 CO-0301 Re' -:e Ced 950011-P 325 650

SEPTEMBER 1995

MARCH 1995is 1'' :re-5.G^, rr.era stitch- P53 + PIC 1946642-11 455010-C 22.60 44 CO MC 16554 946642.1 17.50 MO

95P e.rcXxi Wren:1P59 Os. 117956001-1)511*014(950501-1) 550314-C 49.00 26.03

- EPROM 27C512 556511-1 13.25 2630- .c.-rtwre C 11311 PC dsk 955307.1 1850 n 03- o_wem nom.-, 950014-P 750 1530415600 catnone.er 9533.24-1 9.53 19.00

FEBRUARY 1995ti -sr 940353-1

Owed srrrer 940104-1Lcia-eOrts obeesor 5401E04alro(r4 Sasrd CrOM 950012-1rOxtot MIN" perm, 9400454

JANUARY 1995Watt Falb 540 940099-11-1:1-3-1:1am CV:verte- PCB EPROM 940077-C- CAL 9466404- EPROM 94640-2P.05 T. twos.% crd- PCS + Geis )946639-1 li950008-C- GAL -1 945533-1- GAL -2 915539-2

551580 56PI93511yoe

10 75 2.1.M9.75 1950650 1303

18 75 37.507.50 15.03

14.75 2950

52_75 1055012.25 24_401575 31 50

25 55 5011.03 22 0013E0 25.03

For !yr-laity or dt'it cAsne cor',Iot OttD1, t0101t"

Elektor Electronics slipcase

Kra 9295 +P&P tE1.50 MOO mes3de. (91)


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Unless you have an approved credit account with us. all orders must beaccompanied by the full payment. including postage and packing chargesas stated above.Payment may be made by cheque drawn on a London clearing bank (butsee para. 4 below). postal order. VISA, Access. MasterCard or EuroCard(when paying by credit card. the order must go the cardholder's address).Do not send cash through the mail. Cheques and postal orders should becrossed and made payable to 'Elektor Electronics (Publishing)'.Payment may also be made by direct transfer from a private or businessGiro account to our Giro account No. 34 152 3801 by completing andsending to the National Giro Centre, in a National Giro postage paidenvelope. a National Giro transfer/deposit form. Do not send Giro transfersdirect to us. as this will delay your order.If you live outside the UK, payment may also be made by Bankers' sterlingdraft drawn on a London clearing bank, Eurocheque made out in poundssterling (with holder's guarantee card number written on the back), or USor Canadian dollar cheque drawn on a US or Canadian bank.If you pay by Bankers' sterling draft, make clear to the issuing bank thatyour full name and address MUST be communicated to the Londonclearing bank.

Our bankers are National Westminster Bank, 49 South Street,DORCHESTER, Dorset DT1 10W. England. Our account number is6966 3340.

Components for projects appearing in Elektor Electronics are usuallyavailable from certain advertisers in this magazine. If difficulties in thesupply of components are envisaged. a source will normally be advised inthe article. Note. however, that the source(s) given is (are) not exclusive.

TERMS OF BUSINESS

Delivery Although every effort will be made to dispatch your order within2-3 weeks from receipt of your instructions, we can not guarantee thistime scale for all orders.Returns Faulty goods or goods sent in error may be returned forreplacement or correction, but not before obtaining our consent. All goodsreturned should be packed securely in a padded bag or box, enclosing acovering letter stating the dispatch note number. If the goods are returnedbecause of a mistake on our part, we will refund the return postage. Goodsreturned for refund must be in resaleable condition and will be subject to a10% handling charge with a minimum charge of £2.50.Damaged goods Claims for damaged goods must be received at ourDorchester office within 10 days (UK): 14 days (Europe) or 21 days (allother countries) from the date on our 'Recorded delivery' slip.Cancelled orders All cancelled orders will be subject to a 10% handlingcharge with a minimum charge of £2.50.Patents Patent protection may exist in respect of circuits, devices,components, and so on, described in our books and magazines. ElektorElectronics (Publishing) does not accept responsibility or liability for failingto identify such patent or other protection.Copyright All drawings, photographs, articles, printed circuit boards,programmed integrated circuits, diskettes and software carriers publishedin our books and magazines (other than in third -party advertisements) arecopyright and may not be reproduced or transmitted in any form or by anymeans, including photocopying and recording. in whole or in part, withoutthe prior permission of Elektor Electronics (Publishing) in writing. Suchwritten permission must also be obtained before any part of thesepublications is stored in a retrieval system of any nature.Notwithstanding the above. printed -circuit boards may be produced forprivate and personal use without prior permission.Limitation of liability Elektor Electronics (Publishing) shall not be liable incontract. tort. or otherwise, for any loss or damage suffered by the purchaserwhatsoever or howsoever arising out of, or in connexion with, the supply ofgoods or services by Elektor Electronics (Publishing) other than to supplygoods as described or. at the option of Elektor Electronics (Publishing), torefund the purchaser any money paid in respect of the goods.Law Any question relating to the supply of goods and services by ElektorElectronics (Publishing) shall be determined in all respects by the laws ofEngland. January 1997

05/97

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Seme Ltd., the Melton Mow-bray based ComponentsSpares Distributor for con-sumer electronics have recog-nised another growth marketarea, that of Computer Acces-sories. They have assembleda range of products including3.5 -inch diskettes for IBM PCsand compatibles. mousemats, computer cleaning aids.4 -way mains extension withbuilt in surge and spike pro-

JPIEW PRODUCTSNew PC cards give Notebook PCs serialcontrol capability of industrial devicesNational Instrumentshas announced oneand two -port PCM-CIA-232 and PCM-CIA-485 interfacesthat give notebook

computers control ofserial devices for

portable or remoteapplications.

The PCMCIA-232 and PCM-CIA-485 are asynchronous se-rial interfaces that are Win-dows 95 Plug and Play com-patible for easier installationand maintenance. Applicationsoftware packages such asBridgeVIEWni, LookoutThi,LabVIEWR, ComponentWork-

0.1, and MeasureTm, as wellas development environmentssuch as Visual C++, can ac-cess the PCMCIA-232 andPCMCIA-485 using standard

serial I/O functions. The PCM-CIA-232 and PCMCIA-485 de-liver the additional serial portscommonly needed in industri-al applications to communi-

cate with devices such asPLCs, data loggers, and sin-gle -point I/o modules.The PCMCIA-232 and PCM-CIA-485 connect to RS -232and RS -485 devices, respec-tively. The PC operating sys-tem performs all board con-figuration; no jumpers or DIPswitch settings are required.The cards are also compatiblewith standard serial port dri-vers for protocols such as Op-toMux and ModBus.National Instruments Corp.(UK) Ltd., 21 KingfisherCourt, Hambridge Road, New-bury, Berkshire RG14 SSJ. Tel:(01635) 572400, fax : (01635)524395. e-mail :info.uk(ii natinst.com. Internet:http:1;www.natinst.comiuk.

977076'

World's smallest microcontroller withA/D converterMicrochip's revolutionary 8 -pinmicrocontroller family (theworld's smallest) now includesdevices with advanced ana-logue -to -digital features. ThePIC12C671 and PIC12C672 8 -bit one-time programmable(OW) microcontrollers enableintelligent features to be inte-grated into mechanical de-signs. They will compete di-rectly with 4 -bit microcon-trollers, but offer significantlyenhanced performance.The advanced analogue fea-tures include an on -chip ana-

logue -to -digital converter andfour analogue channels, whichare ideally suited to measuringenvironmental conditions suchas temperature, pressure, mo-tion and voltage. Specific ap-plications include intruder de-tectors, pressure gauges, watermeters, smoke detectors, ther-mostats, rheostats, batterychargers and rechargeable bat-tery packs.The PIC12C671 and 12C672have 1024 and 2048 words ofprogram memory respectively,plus 128 bytes of user RAM.

They also provide6 multiplexed I/Opins with on -chiposcillator (4 MHz),35 single -word in-structions, fullspeed 1 -us instruc-tion cycle at 4 MHz.8 -level deep hard-ware stack. 8 -bit real-timeclock/counter with 8 -bit pro-grammable prescaler, watch-dog timer, direct LED drive, low2.5-5.5 V operating voltage andless than 2 mA at 5 volts, 4 -MHz low -power consumption.

!IComputer accessor e. i

tection. D -type connectors,CD-ROM driver software,printer leads, null modemleads, gender changers,power leads and a compre-hensive range of monitorspares. L9770791

Seme Limited, Unit 2, SaxbvRoad Industrial Estate. MeltonMowbrm. Leics LE13 IBS.Tel. (01664) 65392, fax (01664)63976.

.Arizona Microchip TechnologyLtd., Unit 6, The Courtyard,Meadowbank, Furlong Road,Bourne End SL8 5AJ. Tel.(01626) 851077, fax (01626)850259.

;97i:E,D)

Elektor Electronics 5197

Sirius MicroSystems announces aPICTM microcontroller development systemSirius MicroSystemshas developed a mi-

crocontroller devel-opment system (PIC-

MDS-) for the inex-pensive Microchip

PIC- family of RISCmicrocontrollers.

The PIC-MDS is a completedevelopment system consist-ing of a development board,programmer, cross -assembler

and detailed training text. ThePIC-MDS was specifically de-signed to make learning howto program and use micro -controllers easier. Step bystep examples guide usersfrom writing and testing sim-ple programs to keypad, LCD,AID, serial 110, data loggingand interrupt routines.

The PIC-MDS developmentboard includes: bothPIC16C71 and PIC16C84 mi-crocontrollers, 16 key matrix

keypad, 2 line by 16 characterLCD display, ZIF socket,buffered LED port state indi-cators, RS -232 serial port, 2analogue input potentiome-ters, 256 byte serial EEPROM,oscillator socket for crystals orceramic resonators, on -board+5V and variable DC powersupply, and screw terminaland header connections to allPIC I/O pins.The PIC-MDS is ideal for en-gineers, technicians or hob-byists who would like to learnhow to use microcontrollers intheir designs. Since common-ly used microcontroller I/O de-vices are included on the PIC-MDS, users can refine theirapplications on the develop-ment system without theheadaches of hardware pro-totyping. Once applicationshave been proven on the PIC-MDS, the programmed PICcan be transferred to the tar-get system.Microcontroller applicationsare created and assembledon an IBM-PC using the PMMacro Assembler. The trainingtext fully explains each exam-ple and its operation. Userscan then write their own ap-

plications incorporating thetested software routines. Ap-plications are programmedinto the PIC16C71 orPIC16C84 using the includedEPICTm programmer.The EPIC programmer is ca-pable of programming all mid-range 18 -pin PIC microcon-trollers (PIC16C61 '62x, '71,'84). With optional 28 -pin and40 -pin socket adapters, EPICwill program the PIC16C73,'64, '65, '74. The EPIC pro-grammer attaches to the PIC-MDS development boardthrough an in -circuit program-ming connector allowing thePIC16C84 to be programmedwithout removing it from thePIC-MDS board. The cost ofthe complete PIC-MDS devel-opment system is US$299.00. Hobbyist and stu-dent versions are also avail-able. For more informationcontact

Sirius MicroSystems, 172 Har-vard Road, Waterloo, OntarioN2J 3V3 Canada. Tel. 1-519-886-4462. Fax 1-519-886-4253.Internet:http://wwwsiri usmicro.com.

(9770761

KEELOQ Encoders/Decodersfor secure wireless communication in consumer cpplications

Microchip's new Ad-vanced KEELOQ

Hopping Encodersand Single -Chip

KEELOQ Decodersprovide a complete

solution for unidirec-tional remote -key-less -entry applica-

tions. The only com-ponents required fordevice operation are

the push buttonsand RF circuitry.

The HCS360/HCS361 en-coders contain a programma-ble 28/32 -bit serial number toidentify the transmitter and a

64 -bit cryptographic keyunique to each device. Thekey is used to generate anultra secure 32 -bit hoppingcode. The encoders provide67 bit transmission length, a48 -bit seed in 'secure learn'mode and CRC error detec-tion. The encryption key, seri-al number and configurationdata are stored in on -chipEEPROM which is read pro-tected. The HCS360/361 havea wide operating voltagerange of 2.0 to 6.6 volts andtransmit up to 15 functions.The HCS509/HCS512 single -chip decoders extend Mi-crochip's family of KEELOQdevices to provide a com-plete, turnkey solution. Theyare the only single -chip de-coders to support KEELOQ

encoders and pro-vide on -chip EEP-ROM for the non-volatile storage ofdecryption keys.The HCS509/-HCS512 have avoltage range of 3.0to 6.0 volts.All four devices areavailable in 8 -pinSOIC and PDIPpackages and aresupported by evalu-ation, developmentand programmingtools. 49770771

Arizona MicrochipTechnology: Unit 6,The Courtyard,Meadowbank. Furlong Road,Bourne End SL8 5.kJ. Tcl.

FICS50-3CECODER--------

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The zniTTET 8051 RASH microcontroller family89051 189LV51 I 89C52 I 891V52 89C55 18958252 189C2051 18901051

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PC52 ate drop -in FLASH replacerne or the generic 87C51/87C52 devicesX145 5.3 single -chip 8051 in a 20 pin parka .even retaining the serial port

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89C-105112051 Microcontroller Demo Module ),

89C-105.12051 Microcontroller OEM Module

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i'filitf.;1112)1:Lf Optimising C Compiler Macro Assembler Softicware Simulatorti Deve Programmer Sample DevicesV HardwarelSoftware Documentation

FREE Atmel CD ROM data bookSystem supplied with I x Atmel AT89C1051and 1 x AT89C.2051 Microcontrollets

C -compiler + Assembler outputrestricted to 2k totalprogram code.

Order code: AT -890(051

--;711900diDLIDgtO6

The mbedded Solutions Company

SALES: 01204 492010 TECHNICAL: 01204 491110 FAX: 01204 494883 (INTERNATIONAL DIALLING CODE +44 1204)Num,,x,==liErr 2.0

Programming SolutionsSMART Communications offer the best range of low cost programmers for your every need.Unrivalled device support includes the latest MACH, pLSI, MAPL, PIC, WSI, Atmel, Xilinx and

Intel parts.

1ALL -07 Universal ProgrammerPin driver expansion can drive up to 256 pins.Supports over 2000 IC's -3 and 5 volt devices.

EPROMs, E2PROMs, Bipolars, Flash, Serial EPROMsup to 16 tvibits parts, over 150 Microcontrollersand PLDs, EPLDs, PEELS, PALs, GALS, FPGAs etc...

Universal DIL (up to 48 pins), PLCC and Rang PACs- significantly reduces the number of adapters required.

Powerful full colour menu system.Connects to the pc printer port with its own power supply.Latest programming algorithms.Tests TTL, CMOS and SRAM devices

- even identifies unknown parts.Approved by AtviD, WSI, NS, TI, Atmel, Microchip etc...

£595

EMP-20Multi -DeviceProgrammer

EPROMs, E2PROMs, Flash,Serial EPROMs to 16 Mbits.EPLDs, GALS, PEELs, PSDs, MACHs.

Intel, Microchip, Motorolaand Zilog Microcontrollers.

Fast programming algorithms.

£325

Erasers& in

convertorsAT -701 - ChipraseUltra -violet eraser.

Very compact16 chip capacityBuilt in timer

Pin convertorsfrom DIL to

PLCC, SOP, SOIC etc...

from £50

tvPilAtCOMMUNICATIONS

PB-10 ProgrammerLow cost programmer.

EPROMs, E'PROMs, Flash and 8748/8751.Fast programming algorithms.

simple but powerful menu driven software.

£139SMART Communications have a fullrange ot dedicated programmers for

the Microchip PIC range otmicrocontrollers - both single and

gang for DIL and SOIC toriants.

We also supply a wide range of development tools - Assemblers, Compilers, Simulatorsand Emulators - for a wide range of microprocessors, especially the Microchip range.

Our ROM emulators start at just £99.-All prices shown are exclusive of VAT and carriage

Unit 11, Sterling Industrial Centre Stirling Way Boreham Wood Herts WD6 2BT EnglandTelephone +44 (0)181 953 9292Fax +44 (0)181 953 9299

11

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