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SAM 2001 - XT An IBM compatible with 10Mbyte hard disk, will run all IBM software. Can be upgraded to run as fast as an AT. CEDS From £1995.00. A full PCB design system allowing the design of boards from schematic diagrams. Note: All prices exclude VAT and are Systemm expandable from basic manual subject to change without notice. placing and routing to auto -tracking and schematic capture. Also available with Terms: Strictly CASH WITH ORDER. technical drawing facilities and auto dimensioning. Software from £1200.00. High resolution colour systems from £6000.00.

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www.americanradiohistory.com Editor ELECTRONICS 8 PHILIP DARRINGTON Deputy Editor GEOFFREY SHORTER, B .Sc. 01- 6618639 ire Technical Editor wor MARTIN ese ECCLES over 70 years in independent electronics publishing 01- 6618638 Projects Editor June 1985 RICHARD LAMBLEY 01- 6613039 OR 8637 News Editor Volume 91 number 1592 DAVID SCOBIE 01- 6618632 Drawing Office ROGER GOODMAN Fast camera interface 17 Look after your nickel cadmium cells 60 01- 6618690 by Safa S. Omran by Rod Cooper Taking one pixel from each line of a video camera NiCd cells are expensive to buy yet are often BETTY PALMER signal to feed a micro is a solution to the speed thrown away for lack of a few drops of water. Rod problem. This method uses eight. Cooper discusses more failure modes and Advertisement Manager suggests how to avoid them. BOB NIBBS, A.C.I.I. 01- 6613130 Sampled -data servos new analysis -a 34 MICHAEL DOWNING by D.M. Taub Cassette recording with the BBC micro 01- 6618640 Fourth instalment in this new tutorial series by David Stonebanks 64 derives the response of a servo system to Improved performance with conventional ASHLEY WALLIS sinusoidal input. recorders and an alternative digital method. 01- 6618641 Northern Sales Managing research and development HARRY AIKEN Valve disc preamplifier by R.E. Young 061 -872 8861 In which the 'small -team' approach to R & D by Richard Brice 73 contrasts with the hierarchical style of Simple design without overall feedback, using Midland Sales management. passive RIAA equalization. BASIL McGOWAN 021 -356 4838 Helical antennas for 435 MHz by James Miller 43 Power'85 Classified Manager Simple -to -make design having true circular List of exhibitors 75 BRIAN DURRANT polarization. Intended for satellite working, but 01- 6613106 excellent also for local and long distance IAN FAUX operations. Two -dimensional digital filter design 01- 6613033 by R.N. Gorgui -Naguib, K.M. Henein and 76 Switched -mode power supplies 49 R.A. King Production by K.L. Smith Thik detailed comparison of current design BRIAN BANNISTER This part of the d.c. supplies series explains the techniques follows the authors' earlier article on (Make-up and copy) theory, practice and design of switchers. one-dimensional filters. 01- 6618648

Reactivating Band Ili 57 Channel code and disc format 80 Current issue price 85p, back issues (if A report from the Mobile Radio Users' by John Watkinson available) £ 1.06, at Retail and Trade Association conference which discussed trunked Part of our definitive Compact Disc series, this Counter, Units 1 & 2, Bankside Industrial repeater networks and worsening interference continuation shows how the information is Centre, Hopton Street, London SE 1. Available on microfilm; please contact problems. organised on the disc surface. editor. By post, current issue £ 1.30, back issues (if available) £1.40, order and payments to EEP Sundry Sales Dept., Quadrant House, REGULARS The Quadrant, Sutton, Surrey SM2 5AS. Tel.: 01- 6613378. Editorial & Advertising offices: News Commentary 6 Circuit ideas 29 Wirelesswörld Quadrant House, The Quadrant, Sutton, New blood Trip for power switches Surrey SM2 5AD. End of ATS -1 Two -i.c. shortwave calibrator Telephones: Editorial 01- 6613614. Advertising 01- 6613130. See leader page. Towards a thinking computer Fast converter for repetitive signals Telex: 892084 BISPRS G (EEP) Sending text to Wireless World ' Centronics -to -RS232 converter Subscription rates: 1 year £ 15 UK and Coming to this screen shortly... , £21 outside UK. Student rates: 1 year £ 10 UK and £ 14 outside UK. 69 °`Feedback, Distribution: Quadrant House, The Books D.c. supplies .... Quadrant, Sutton, Surrey SM2 5AS. 20 Telephone 01- 6613248. Electro reductionism Subscriptions: Oakfield House, Relativity Perrymount Road, Haywards Heath, Energy transfer Sussex RH16 3DH. telephone: 04444 coter shows the 70cm 459188. Please notify a change of Communications 23 Front address. aerial ma de by James Miller for USA: S102.70 airmail. Business Press Costly DEF the RSGB's headquarters International (USA). Subscriptions Office, V.h.f. changes New Products 84 205 E. 42nd Street, NY 10017. Radar up -date Fast tape storage station at Potters Bar. USA mailing agents: Expediters of the JAS -1 in 1986 256K s.ram Photography by Grahame Printed World Ltd, 527 Madison Avénue, Circuit diagrams on a micro Richardson. Suite 1217, New York, NY 10022, 2nd class postage paid at New York. © Business Press International Ltd 1983. ISBN 0043 6062.

www.americanradiohistory.com i ' Comes in a 16K EPROM and 40tk disc for the BBC EI o Complete Wordwise style integrated A editor with special debugging aids Assembles for 7 different MPU families .. right now - FREE updates take this up to 11 -"' ETA Nestable Macros (with parameters), ' ASSEMBLER Nestable IF /ELSE /ENDIF conditional assembly Specially integrated Macro Library facilities fully is both an Editor and a very special Assembler. Macros and IF /ELSE /ENDIF Conditional Assembly are META Meta can Assemble all these 16K EPROM, but the tables supported, and both are nestable. Macros may also pass Most of META resides on a instruction sets right now: defining the language the Assembler is to translate Assembler parameters, and contain local labels. There's also a range of for ANY instruction set - you specify which you want to use EQU pseudo -ops for data setup, all of which may have a list 65xx series incl. cmos can also in your source code. of arguments seperated by a comma. Disc datafiles The large box on the right details all the instruction sets be inserted into the object code. A complex integrated Macro 68xx /63xx series incl. that have been coded for META right now: all these are Library system is also included - you can invoke a routine 00,01,02,03,05 supplied free with META. The other 4 instruction sets will be and pass parameters by just giving its name. in fast (we 6809 65816 supplied as soon as they are written and tested as A FREE Source code is Assembled two passes don't ... inferior UPGRADE. Were on Freepost, so you won't even have to use the groaning slow BPUT & BGET as do some 8048 series pay postage. Assemblers. Instead portions of the source code are META contains a fully integrated Editor. This follows effectively *LOADed in at top speed.) The resultant object 8080/8085 RAM, user or Wordwise as closely as possible in its philosophy (ie cursor code may be sent to disc files, sideways the down Z8 keys used to move text - quickly - up and down about printer port (full details and examples in manual), or central editing line etc), and includes Global /Selective Search/ the RS423. META Z80 Replace, Markers (copy,save,delete, find marked text), load Remember that all instructions sets supported by the Library etc) text to cursor, character count and heaps of other features. have access to all the above features (Macros, And Free updates ('Real manual and If an error is detected during assembly, the Editor is right META comes complete with a comprehensive Soon Now') include: BBC game there: on the bad line with a plain English error message function key strip. 16K of source code for a 6502 describing the fault. is included free and the META system disc, which 68000 8088/8086 well Complex expressions are allowed by the Assembler, demonstrates many of the features of this assembler. (as Z8000 Micro Nova including brackets to 8 levels (!). All calculations are to 32 as being a neat game!) bits. CRASH BARRIER FREEPOST METNA55EMBLER £69'9s FLITWICK All inclusive. Free updates included in price - BEDFORD updates expected to be available early July. META is available right now. MK 45 1YP Dealer enquiries, as the saying goes, are welcome. (0525) 717148 Generous discounts to educational institutions.

CIRCLE 83 FOR FURTHER DETAILS. COMPUTER APPRECIATION 16 Walton Street, Oxford OX1 2HQ Tel: Oxford (0865) 55163 Telex: 838750 £50.00 UNITRON Model 2200 Microcomputer, Apple 11/E and CP /M compatible machine with 6502 and TEKTRONIXModel4601 harda copy unit for 400 series graphic terminals computer output £75.00 Z80 processors, 64 Kbyte memory, detached keyboard with numeric pad and floppy disc TEKTRONIX Model 611 Graphics storage display. For use with any DAC £225.00 interface. BRAND NEW AND BOXED £325.00 FACh Model 4020 High speed paperand tape reader. Parallel IlL interface £250.00 ROCKWELL AIM 65/40 single board 6502 development system with display, keyboard, power FACIT Model 4070 Paper tape punch £425.00 supply and casette recorder £350.00 CALCOMP Model 563 AO drum plotter. 0.1 mm step size P 0 A MANNESMANN /ITALY Model M80MC Matrix Printer with microprocessor control 200CPS CALCOMP Model 763 .As above, but high speed with type 915 magnetic tape bidirectional printing with WI case, self test. Compact but heavy duty machine. BRAND NEW AND CALCOMP Model 1036 AO Graph plotter. High speed 3 colour plotter P 0 A BOXED £95.00 unit for optional off. line use, and Selectable for 7 /9 track, 800 /1600B.P.I.etc A CENTRONICS Model 702 Matrix Printer, 132 col., 165cps, bidirectional printing with self test. In C.I.L. Model6000, 2 Pen AO high speed graph plotter P O £250.00 good ex -demo condition £150.00 HEWLETT-PACKARD Model 75C portable computer integral graphics display, printer and CENTRONICS Model 150 -2 printer, NEW £325.00 HEWLETT-PACKARD Model 85 desk top computer with £690.00 DIABLO HYTYPE II DAISY WHEEL PRINTER (45CPS) £125.00 tape drive OLYMPIA SCRIPTA, Daisy wheel printer with centronics interf ace. Two available, both less GENERAL DATACOMM (IAL) Model LDM -1 private line modem £150.00 used with above processor chip and prom but otherwise complete. The pair £120.00 GENERAL DATACOMM Model TDM 1240 4 line statistical multiplexer as £150.00 PERTEC Model FD 5148" Floppy disc drives. AS NEW £50.00 modem. 280 controlled. Manufactured 1981 £500.00 SHUGART SA400 51," Floppy disc drives £50.00 DEC LS 1 -11 /23 processor with MM U sold DEC boxes and power supplies. Various models available (BA11 MF SB11 AA, BA11 LX) all with 22 NEC Model 5510 spinwriter, 55cps daisy -wheel printer with RS232 interface. As new, and £650.00 bit addressing or easily modified and various optional processors etc...P.O.A. with tractor unit, manual and complete set of mechanical spares ITT Model 3510 telefax facsimile transmitter /receiver. Micro -processor controlled (8085) CCITI group 2 machine for transmitting documents over an ordinary phone line. BRAND NEW AND Please note: VAT & CARRIAGE extra on all items Visitors by appointment. please. Technical manuals are BOXED £295.00 available from as for many items stocked. CIRCLE 85 FOR FURTHER DETAILS.

Electronic ftn Corporation r RADFORD THRULINE® Directional Wattmeters Audio Measuring Instruments, TERMALINE® RF Coaxial Load Resistors Audio Amplifiers, Loudspeakers and TENULINE® Attenuators and accessories Loudspeaker Components for the from stock professional and enthusiast Aspen Electronics Limited RADFORD AUDIO LTD. The exclusive UK representative for Bird Electronic 10 BEACH ROAD 2/3 Kildare Close, Eastcote, Ruislip WESTON -S -MARE, AVON BS23 1AU Middlesex HM 9UR TEL. 0934 416033 Tel: 01- 8681188 Tlx: 8812727

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www.americanradiohistory.com * COMPUTER PERIPHERALS * * * NI -CAD BARGAINS * * RALFE ELECTRONICS 10 STREET, LONDON, NW1 TEL: 01 -723 8753 Ex- equipment but little -used, re- chargeable Nickel -cadmium CHAPEL 1.6MB 8" FLOPPY DISC DRIVES - New batteries at fraction of L.P. Stock DEAC Type 1000DK 6 Cell Button -stack (7.2V) Measures 214' Diem. Capacity 1AH. Price each BRAND NEW At a surplus price. Fully Shugart compatible'MFE C3. -inc vat (pp 25p) CORPORATION' Model M -700 DOUBLE -SIDED industry standard 8" DEAC Type 600DKZ 3 Cell Button -stack (3.6V) Floppy disc drives. Double -density, up to 1.5MBytes Power Measures 11.1ï Diam. Capacity 600mAH Price requirements V5V and - 24V 0 1.1 A. 240V AC 50Hz. each f1 50 Inc vat IOp 25P, LOWEST PRICE EVER Or 60 - INC VAT CARRIAGE B HANDBOOK *it STEPPER MOTORS ** DRE 4000A DRIVES Brand new stock of 'ASTROSYN' Type 20PM- Data Recording Equipment Model 4000A 5 + 5 MB Top - A055 stepper motors. 28V DC. 24 steps per rev. loading disc drives in stock. Brand new including full 15 oz -in torque f 100PPS. Body length 21/ ", technical manual. Few remaining C250 each + VAT. 2 x diameter shaft 1/4" diam 41/4" spirally TEKTRONIX 454 Dual -trace 150MH0 sweep delay £650 SHUGART 8" Flexible disc drives model SA800. threaded. Weight 16oz. Price each Ell. 50(p &p TEKTRONIX 453 Dual -trace 50MHz sweep-delay £500 Condition as new £150 + VAT (Including postage and 50p). Connections supplied. INC. VAT TELEQUIPMENT 075 Dual -trace 50MHz. Delay. £400 handbook copy) C300 i TELEOUIPMENT 563 15MHz Dual 8 Differential !!! NEW STOCK !!! * STEPPER MOTORS * TELEOUIPMENT DM63 as above « STORAGE £500 * MULTI -RAIL LINEAR PSU's * TELEOUIPMENT £83 50MHz Dual -trace C450. In stock used, but excellent condition, 4 -phase 50 by4 £650 - steppers. 35MHz Dual -trace COSSOR CDU150 Recent stock of brand new COUTANT ESM- Series Power Supplies at steps /rev motor with (removable) gearbox giving a 300:1 reduc- -PACKARD 141A 20MHz Storage £350 HEWLETT ieesemosinsomoe surplus prices. Model ESM15.2 giving regulated. stabilised OC tion, 6V DC operated. Complete with a driver board requiring just a outputs 5V 15A and 312V to í:15V 1.5A each and an un single 6V rail and pulse input. Motor measures 1' . 2 diameter, 1000 WATT AUDIO AMPLIFIERS stabilised 24V 2A. 240V AC input. Measures 548.115 Fully gearbox'/; x 2'/; output enclosed. In original canons with handbooks. E45 each o VAT I. shaft 3/161. Sold com- carriage 0) plete with connections. :v+y CCT diagram of motor, ,j Iw H 8 H PROFESSIONAL AUDIO POWER AMPLIFIER MODEL 3500 -0 available ex -stock in superb. little- COUTANT LINE CCT details of half - SUPPLIES: used condition at vastly reduced price. Specification includes: Dual -Channel 500.500W. THD MODEL ASA2000. 5V. 20A. £35 And pulse) stepping etc. 4- 0.005% IMD 0.02 %. Output impedance 2.5- 16ohms. Frequency response: ±rdb 10Ho -20KHz MODEL ASC300. 24V. 2A. C20 generator. Complete L0.50 inc. vat. (pp 500L ¡NB. For industrial applications these amps' can be configured to DC response) Forced air cooled (inc vat, pp £4 8 C2 respectively) dIssipators for reliability and cool operation. Size 19' Rack mount x 3.5' Ht ESCAP DC MOTORS. PRICE JUST 1275 inc vat 8 handbook. Carriage £5. INB.. List price over C700.I Swiss -made precision 6V DC motors with 701 reduction gearbox giving final drive 16rpm 4D 6V. Diameter 2) cros. 4cms speed of PHIWPS TEST EQUIPMENT * long. PRICE INC. VAT 8 CARRIAGE. C5.25. MARCONI * Brand new, surplus to requirement stock NOT to be repeated. Ex -equip. tested 6 guaran teed) * 125W MAINS INVERTERS * TEST One -offs only.: 12V DC Battery Input to 230V AC. Output 125 EQUIPMENT Model 1051 DIGITAL VM PM2554 MILLI -VOLTMETER. DATRON watts crystal -controlled 50Hz time -base I; e,``: oscillator. fully enclosed in blue -steel cases PM6661 FREQUENCY COUNTER.

Ali integral 13A socket Dimensions approx 195533 with Fully re- conditioned test eq wpmrnl. PM6307 WOW 8 FLUTTER METER. 8 d # iiii 4.6x10'. BRAND NEW. £60 Inc VAT 90 -day guaranteed. Carriage. TF995B/5 AM /FM SIGNAL GENERATOR 1051 Multi-function digital voltmeter (DC) with Options fitted 0.2- 220MHz £500 for AC Volts and Resistance. Total list is over C2200 Little TF1245 0 -METER WITH OSCILLATORS * CENTRIFUGAL BLOWERS * used condition 124687 L £750. MAINS CONDITIONERS TF2002 AM /FM SIGNAL GENERATOR 'TORIN' Type U62B1. 230V Cap'Start (supplied), very powerful R. 240V 50Hz. Input to 110V CROSS -HATCH GENERATORS * * TRANSVE RTE 01 -72MHz £550 (200W, 3.000 rpm) centrifugal fans for large rack cooling or * * TF893A AUDIO POWER METERS TO 10W 60Hz Out O 250W. £350. enclosure extraction applications. Overall dimensions 20.12 cros. . LABGEAR COLOURMATCH CM6004PG. TB5 each inc. VAT, pep ADVANCE MT140A. 230V 150W outlet 6.4 cros. BRAND NEW. Surplus stock. £15 UHF teevision pattern generators TF2905 SINE SQUARED PULSE 8 BAR £20 vat (pp C21 £1.50. giving -hatch, dot and greay scale GENERATOR £250 cross GOULD 'ECVN' 220V 250W pOopzranteetl. (2504 ELECTRONIC VOLTMETER C150 £45 vat (pp C31 INSTRUMENT COOLING FANS Npatterns.JUST L2Ó incVAT * * GOULD 'TCVN' 220V 1500W CM6010RG Gated Rainbow colour vat (pp £51 LABGEAR COLOURMATCH £95 EDDYSTONE Communications receivers Ail tans available ex -stock and GUARANTEED generators. Cross- hatch /dot 8 gated rainbow (RGB) CETRONIC 'REGUVOLT' 220V 3KW pattern 770R/1 Covering 19- 165MHz 8 £200 230V 10W 5 -Blade 3)3;.1- NEW E7 colour bar patterns t85iec £350 vat (pp C101 770U/2 Covering 150- 500MHz £225 t t 5V 13W 5 -Blade 3;.3;.1- NEW T0 UNAOHM E0684 PAL Colour -bar 8 pattern gen 1275. 115V 4)4)x1;- 5 -Blade NEW £6 115V 7W 4) 3 -Blade WHISPER C5 KORTING 82512PAUNTSCColour 8 pattern gen 275. COMPANIES PLEASE NOTE That we would be very pleased to receive your invitation to tender 230V 40W Papst 350M /Hr, Ex-equip- C13 Mail Order customers please add £2.50 postage each item. for your surplus or redundant equipment Contracts stirred for factory contents removals on regular basis All prices include VAT (pp 50p)

CIRCLE 67 FOR FURTHER DETAILS. FORTH = FIELD ELECTRIC LTD 3 SHENLEY RD, BOREHAMWOOD, HERTS. TELEPHONE 01- 953 -6009 TOTAL CONTROL /OFFICIAL ORDERS /OVERSEAS ENQUIRIES WELCOME THUR.9.00am /1.00pm FORTH programs are instantly Application Development Sys- OPEN 6 DAY'S A WEEK 9.00am /5.00pm portable across the most popular tems include FORTH with virtual FARNELL FAN COOLED MULTI -RAIL SWITCH MODE + 12V microprocessors. memory, multi- tasking, assembler, AT 15AMP -5V AT lAMP + 12V AT 4AMP -12V AT lAMP full- screen editor, decompiler, £28.00. utilities, and full documentation. FORTH is interactive and very GOULD PMA47 12V 3AMP D.C. LINEAR £16.95. fast. LMI Z80 FORTH - CPM 115 V.A.C. 4" FANS NEW & BOXED £4.95. 2.2 £95 230 V.A.C. 4 FANS EX- EQUIP: NEW CONDITION £5.00. LMI 8088 FORTH - FORTH programs are structured, G.E. PANEL METER 0 -5A A.C. £7.00. CPM-86, MSDOS £110 modular, and easy to maintain. BOXED. LMI PC/FORTH - NOT SCALED NEW & PC/DOS £110 M.P.I. 1/2 HEIGHT DISK DRIVE 51/4 " FORTH gives control of all MPE-FORTH 8809 - 40 TRACK SINGLE SIDED NEW £65.00. interrupts, memory locations, and FLEX, 0S9 £175 i/o ports. LMI 88000 FORTH - ALL PRICES INCLUDE 15% VAT UNLESS STATED. CPM 68K £225 CIRCLE 82 FOR FURTHER DETAILS. FORTH gives full access to DOS FORTH+ has 32 -bit stacks and files and functions. directly accesses the whole address space of the processor. SATELLITE TELEVISION FORTH appliation programs can PC FORTH+ £225 to turnkey programs. RECEPTION EQUIPMENT be converted 8088 FORTH+ £225 88000 FORTH+ £225 ANTENNA FORTH Cross Compilers can 1.8m dia aluminium petal dish complete with polar mount 45.4 dB gain generate ROMmable code for: Extension Packages include at 11.45 GHz £609 + VAT (carriage included) 6502, 6809, 68000, 8080, Z80, floating point, cross compilers, SATELLITE TELEVISION RECEIVERS - 8086, 6800, 6801/3, 1802, Z8, 8087 support, colour graphics, suitable for 4GHz and 12GHz I.F. input 430- 930MHz £399 + VAT 8070, Z8000, 99xxx, LSI -11 interactive deluggers (carriage included)

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4 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com Sowter Transformers With 42 years' experience in the design and manufacture of several hundred thousard transformers we can supply AUDIO FREQUENCY TRANSFORMERS OF EVERY TYPE YOU NAME IT! WE MAKE IT! OUR RANGE INCLUDES: Microphone transformers (all types), Microphone transformers (all powers), Column Loudspeaker trans- Splitter /Combiner transformers, Input and Output formers up to 300 watts or mc re. transformers, Direct Injection transformers for Gui- We can design for RECORDING QUALITY, STUDIO tars, Multi- Secondary output transformers, Bridging QUALITY, HI -Fl QUALITY OR P.A. QUALITY. OUR transformers, Line transformers, Line transformers to PRICES ARE HIGHLY COMPETITIVE AND WE SUPPLY G.P.O. Isolating Test Specification, Tapped impedance LARGE OR SMALL QUANTITIES AND EVEN SINGLE matching transformers, Gramophone Pickup transfor- TRANSFORMERS. Many standard types are in stock mers, Audio Mixing Desk transformers (all types), and normal despatch times are short and sensible. Miniature transformers, Microminiature transformers OUR CLIENTS COVER A LARGE NUMBER OF BROAD- for PCB mounting, Experimental transformers, Ultra CASTING AUTHORITIES, MIXING DESK MANUFAC- low frequency transformers, Ultra linear and other TURERS, RECORDING STJDIOS, HI -Fl ENTHU- transformers for Transistor and Valve Amplifiers up to SIASTS, BAND GROUPS AND PUBLIC ADDRESS 500 watts, Inductive Loop transformers. Smoothing FIRMS. Export is a speciality and we have overseas Chokes, Filter, Inductors, Amplifier to 100 volt line clients in the COMMONWEALTH, EEC, USA, MIDDLE transformers (from a few watts up to 1,000 watts), 100 EAST, etc. Send for our questionnaire which, when volt line transformers to speakers, Speaker matching completed, enables us to post quotations by return. E. A. Sowter Ltd. Manufacturers and Designers E. A. SOWTER LTD. (Established 1941), Reg. No. England 303990 The Boat Yard, Cullingham Road, Ipswich, IP1 2EG, Suffolk, P.O. Box 36, Ipswich. IP1 2EL, England

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ELECTRONICS & WIRELESS WORLD JUNE 1985 5

www.americanradiohistory.com NEWS COMMENTARY

Cellular data A method of reliably CDLC products will be add -on by cellular phones 16 days left transferring data modems for cellular telephone network from and to which will provide 1200 /s Weather Report - a mobile subscriber has been pseudo -full -duplex developed. Racal Vodata has transmission. Any digital Clear and bright worked with Racal Research to equipment with RS232 named CDLC may be To beat develop a protocol interfacing connected to (Cellular Data Link Control) the system. These include blistering which is specifically designed to personal computers, printers, midday heat: overcome the problems of data v.d.us and other terminals. 4am start! transmission encountered on a Racal -Vodafone believes that cellular radio network, this is at the forefront of world particularly when switching cellular technology and will be a between cells which are subject major factor in persuading to fading and hand -off. The first customers to use their system. Tape makers slam levy Can your computer climb Mount Everest? The challenge is games of posed by Summit, one of four entertaining proposed levy time the distributors and strategy for young geographers in a new software pack The Government from BBC Publications. The others include an exploration on blank recording tape is retailers have added their mark- game designed to give an understanding of contour maps condemned as unworkable, up and v.a.t. is added, the levy and an intercontinental airliner simulation in which the unnecessary and punitive by the could be doubled. The scheme pilot must navigate his way safely to his destination. The Tape Manufacturers Group. could be circumvented by the games tie in with a BBC radio series for schools, but can levies would be import of tape from overseas be used independently in the classroom or at home. Under the plans Introducing Geography is available for the BBC Micro on inposed of 10% on the price of undercutting the local product. three well -filled discs at £20 and there is an accompanying audio and 5% on video tapes. "The incentives to counterfeit book for £4.95. Each cassette would carry a the levy stamp would be From the same source comes Maths with a Story, which levy stamp and manufacturers enormous." with subtlety and imagination introduces children of and retailers selling tapes The Group also maintains primary school age to elementary probability, the four- that the need for levies has not colour map problem, graphical co- ordinates and the without stamps could be fined. In concept of symmetry. A cassette for the BBC Micro Those caught using unstamped been proven. an independent (transferrable to disc) costs £10.95 and versions for the tapes could also be prosecuted. survey of video recorder use, Acorn Electron, Spectrum and Commodore computers are Christopher Hobbs, Chairman less than 1% of recorded in preparation. The associated book for parents will be of the TMG likened the levy to material is kept for repeat published on May 23. "the Government adding £50 to viewings. The vast majority of the price of cars sold to allow video usage is for time -shifting; for offences that the owners recording programmes for End of ATS- 1 might commit." He also said viewing at a more convenient that the scheme would be an time. In audio, another survey "administative nightmare, full has shown that less then 22% of after 18 years of loopholes for the the population buy blank tape unscrupulous to exploit the for any purpose; almost 70% of After more than 18 years of navigational effects of satellite public." record taping is from the user's service, NASA's first communications. The proposals of the own records and 25% do it to Applications Technology In 1971 it was used for the percentage levies are for the maintain their records in good Satellite, ATS -1 has failed to link between us and Soviet manufacturers' prices. By the condition. respond to commands to scientists during an correct its eastward drift and atmosphere, sea and ice will lose its useful orbital conditions experiment inthe position in about six months. Bering Sea. Launched in 1966, with an It has been employed in Powerful exchange expected life of three years, the several medical connections world's most completion next year. satellite has provided voice and including the transmission of Claimed to be the The exchange has been communications to wide cardiographs from Hawaii to powerful exchange, the data over the past nine area around the Pacific Basin. New Zealand and from Alaska international telephone upgraded House, months and all the operations During its service it has scored to the University of exchange at Keybridge can handle including replacing the central several significant Washington; for a link -up Vauxhall, London, attempts an hour. processor have been carried out achievements: between 12 nations for medical 800 000 call exchange can cope without disrupting the service. It was the first to transmit a conferences with the University The digital with data, text, facsimile and It is used primarily for full -earth, cloud cover picture of Hawaii and as a link to as well as telephone international direct dialling calls from geosynchronous orbit. paramedics in remote parts of graphics is supplied by Thorn and it is linked to BT's other It transmitted real -time tv Alaska. speech. It and is based on the international exchanges . It also pictures from the Apollo 4 ATS -3, launched in 1967 is Ericsson AXE10 design with an handles transit calls (from one splashdown in the Pacific. still in operation and covers the Ericsson APZ212 processor. At present country to another through the It was used between 1967 US and most of the Atlantic as it has capacity for 13800 UK) and operator- connected and 1968 for two -way well as the eastern Pacific and this is to be calls. communications tests between including Hawaii. circuits expanded to 50 000 circuits on aircraft to determine 6 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com unobstructed by mounting taken as luggage on scheduled struts and hardware which in air services. A two -man crew Here isthenews... other designs lead to side - can have it up and running in as lobes. little as 15 minutes. without interference GEC McMichael designed the A special feature of the antenna using specially - package is a video compression A 14GHz satellite terminal Commission's exacting technical developed computer software. codec which makes it possible made by the British company specifications. They say there is no simple to transmit the video and sound GEC McMichael will soon be The orbital positions of mathematical expression to signals in digital form at a helping bring to American satellites used by American represent the curvature of the choice of data rates ranging television audiences live broadcasters for temporary dish; but its overall shape is farom 1.5Mbit /s to 8Mbit /s. pictures of new events which links are so close together that elliptical, combining a large The rate can be selected to suit until now would have been off -axis radiation by ground radiating area with the operating conditions: with -0 impossible to cover. stations using them must be compactness, transportability the slower ones, the clarity of The CBS network has strictly controlled. Newshawk and low wind -loading. the picture is reduced in areas ordered GEC McMichael's meets the requirements easily Two versions of the terminal where movement occurs. Newshawk satellite terminal, by virtue of its unique one -piece are available: the 3m -high GEC McMichael Ltd., Sefton which is the first transportable antenna design. An offset -fed' trailer -mounted model shown in Park, Bells Hill, Stoke Poges, Ku -band earth station to meet Gregorian configuration the photograph, or the version Slough SL2 4HD, tel 02816- the Federal Communication provides an r.f. path bought by CBS which packs 2777. away so small that it can be

Sending text to us

Business Press International, Transmit in capitals EWW, the our parent company, has system will respond with installed a Case Beeline System + + +STF GO; Then type the which can be used by those destination, e.g. "For the with a microcomputer and a attention of the editor "; your modem to send text. The details and the message, in modem needs to be set up to upper and lower case. Sign off 300Ba id, even parity with with NNNN, in capitals. 10bits /character. To use the Terminate call. At the receiving system dial 01- 661 -8978, wait end the message is treated like for a response tone from our a Telex and rushed straight to modem, connect your modem. us. Coming to this screen short) y Now that negotiations for the not of engineers or programme - while Westminster and The something like £50 000 an BBC's tv licence fee are over, it makers but of dark- suited Times try to steer us away from hour. Cable tv hopes to get by is worth looking at what the businessmen whose instinct the licence fee system, the on £5000 an hour or less. opposition is up to. And by that tells them that there is money cable tv industry is doing the Certainly, part of the difference we don't mean ITV. Or even to be made out of cable, exact opposite; the difference can be accounted for by the radio. without so far having revealed being that the monthly 'licence broadcasters' organizational The cable tv industry has been precisely how. fee' for a cable tv connection structure and high labour costs. in the doldrums lately. The The whole affair turns on now works out at two to four But how can cable possibly euphoria brought on by the money, of course, and it is times as costly as the ordinary compete? Even the rubbish Government's initial interesting to note that there is broadcast one (which cable from the BBC and ITV is announcements a couple of general agreement that there is subscribers have to pay as usually good quality rubbish. years ago soon evaporated. And no prospect of supporting cable well). The inevitable conclusion as disillusion with British tv entirely through advertising Television costs money, and must be that there is only one prospects for the new medium income. The tv audience of the good programmes generally way cable can get anywhere in set in, several powerful Anglo- future will be fragmented into cost big money. From that Britain. And that is by American engineering marriages ten, twenty or more minority point of view, signs from the lobbying: by so demoralizing formed to exploit it found groups watching ten or twenty cable tv business are not the existing broadcasters and themselves on the rocks. But different channels. How could encouraging. Burdened by the undermining them financially now things are looking up once any programme deliver enough heavy cost of setting up their that they lose the will to more; and on council estates in viewers to attract the networks without the survive. If that happens, then Croydon and elsewhere a few advertisers? It would scarcely government aid enjoyed by cable tv's endless pop promo brave spirits are hard at work be worth the expense of operators abroad, the new compilations, low- budget pushing cables down holes. producing the commercials. stations must get their talking heads and wall -to -wall 'I But, these sporadic ventures So most of the money for programmes from the cheapest Love Lucy" shows may just apart, the British cable tv cable programmes will have to possible sources. begin to look good by industry is far from booming. It come from viewers' The cheapest network tv comparison. still consists for the most part subscriptions. In other words, programmes now cost

ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com NEWS COMMENTARY

than likely that the arts people the concept of a broad are quite so overcome with education, and it is to be hoped New blood euphoria. They may, however, that this time the Council Looking at higher education as effect: 475 new places in the derive some solace from the means what it says. a whole, the effect of cuts in first phase of the programme stated belief of the Council that However vital it is for the spending continues to bite ever- will be available this coming "a broad education to a late nation's economic growth that more deeply. The Chancellor's October. Dr Kenneth Miller, stage is vital" for the provision there should be a flow of well- Budget allocation of £43M to Director- General of the of "numerate arts graduates and trained scientists and engineers provide additional places in Engineering Council, expresses articulate science graduates ". coming out of universities and engineering and technology at himself as "extremely gratified" The intention is that pupils will polytechnics, it is equally as selected higher education with the outcome of the not have to decide at, or before important in the longer term institution has to be seen campaign. He points out that the age of 16 whether to that they should be as against the overall picture, "the squeeze could affect be scientists or `artists'. This "articulate" as the products of w which still looks very grey engineering education has been said before, by the the other faculties and no less indeed. disproportionately" and that the Council of Engineering appreciative of those facets of new money will help to avoid Institutions in 1980, when the life which have little commercial Nevertheless, the this effect. `breadth' of proposed new value. Education is not, or Engineering Council's campaign Those concerned with courses was to be dealt with by ought not to be, a meal ticket; over the last year for more engineering will, no doubt, the inclusion of "supplementary nor is it a factory process to engineering education resources rejoice at this evidence that the subjects as desired ". A produce a generation of single- has been remarkably successful Government's heart is in the sideways glance at literature or minded technocrats to bolster and is to have an immediate right place, but it seems less history is mere lip- service to the economy. Towards a thinking computer Intelligent knowledge -based Each project is a mathematics but uses logical interfaces, seven are exploring systems is one of the major collaboration between inference, comparison with natural language, three for research areas of the Alvey companies and /or academic previous situations using image interpretation and the project; part of the quest for research establishments and in extrapolation and interpolation, development of robot vision. the next generation of super all, 28 different firms and 26 and estimating. A start has Other areas are inference and computers. Fifty projects, universities, polytechnics and been made in the development knowledge representation, costing about £20M, have been research establishments are of symbolic processing intelligent computer -aided announced which are aimed to involved. languages such as Prolog and instruction, and declarative establish the necessary The research is intended to Lisp, but the development of systems architecture. technology upon which develop systems which can much larger and more powerful There is also a support infra- subsequent industrial and reason and even guess the expert systems is a long -term structure for the programme commercial applications of answer to a problem. They aim, likely to take decades. and include community clubs i.k.b.s. can be based. The would need to be able to handle Demonstation projects under where companies with common researches into `artificial logical relationships and such way include a system to interests and problems can intelligence' include projects on trial -and -error based knowledge monitor the performance of jointly commission the develop- novel computer architecture, to be found in codes of practice, machinery and to permit ment of an expert system. One logic programming languages, rules of thumb or `hunches'. In automatic adjustment to give such club has been formed to expert systems, the under effect they are trying to emulate optimum performance. Another produce software to demon- standing of natural language the human reasoning process is the formulation of mixtures in strate the use of expert systems and image interpretation. which often involves little actual chemical works, such as a in the real -time process control lubricating oil for a specific of chemical plants; another for application. the development of a system for The main research pro- use in civil engineering, partic- gramme is carried out under a ularly quantity surveying. The number of specific research third club is to set up a financial themes and cover an enour- advisor on the performance and mous range with thirteen pro- health of small business jects related to expert systems, companies. Several more are two on intelligent front -end planned or are being set up. Life -saving pager Patients waiting for organ be completed rapidly. Under transplants can now be in the scheme, patients waiting for constant touch with their heart, kidney, liver or other hospitals through Life Page, a organ transplants will be issued service offered free by BT with a standard radiopager. The Radiopaging, Many potential first recipient of a pager at the This liquid level sensor, low and high levels. The transplant patients are still official launch of the service developed by the RNIB, contact sets into motion a active and mobile, not recently was Paul Stokes who is vibrates when liquid bridges miniature Portescap motor necessarily tied to their homes on the waiting list for heart the metal probes in the cup with an eccentric load or beds. However if a transplant surgery at Papworth Hospital. and may be felt by those who weight, producing an audible organ becomes available they BT launched the service to are deaf as well as blind. buzz and a gentle vibration. need to be contacted very celebrate their 250,000th Two sets of probes indicate urgently so that the surgery can subscription to Radiopaging.

8 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com IRVINE BUSINESS SYSTEMS LTD

1 Montgomery Place Irvine, Ayrshire KAl2 8PN Telex 777582 (mark: attn IBS) THE ENGINEERS Z80 COMPUTER WITH IEEE 488

* 2 X Z80 CPU's (4MHz) * 64K DYNAMIC RAM * UP TO 32K EPROM * FLOPPY DISK CONTROLLER FOR 3 ", 5" and 8" Disk Drives NEW * 2 X RS232 SERIAL I/O CHANNELS * I/O MAPPED VIDEO GEN. 80 Cols. 24 R5635 CCITT V22 bis, full- duplex Switched -Capacitor Filter I.C. with MUXes. Lines R5636 Bell 201 /CCITT V26 combo filter I.C. * 4 x PARALLEL I/O CHANNELS R5637 Bell 208/CCITT V27 combo filter I.C. * PARALLEL KEYBOARD PORT R5638 Bell 209/CCITT V29 combo filter I.C. (POWERED) R5630 Bell 103, full- duplex filter I.C. with MUXes. * IEEE 488 INTERFACE R5631 CCITT V21, full- duplex filter I.C. with MUXes. * HARDWARE REAL TIME CLOCK R5632 Industry Standard, Bell 212A/CCITT V.22 full -duplex combo filter I.C. * 2 X 8 BIT SWITCHES (I /O MAPPED) R5633 Selectable filter array I.C. for 103, V21, DTMF and Videotex applications. * MONITOR PROGRAM IN PROM R5626 Mask programmable to your specification. * PROM BASED SOFTWARE AVAILABLE such as ASSEMBLER /EDITOR, and XTAL Contact: EG & G RETICON BASIC WITH IEEE DRIVERS The IBS 750 is an Industrial Quality Product designed for reliability 34/35 Market Place, Wokingham, Berks and ease of use. It is normally supplied fully -built and tested but is RG 11 2PP. Telephone: 0734 788666. also available in a number of partially -built options. The Monitor PROM contains 22 user commands which will assist in Telex: 847510 EGGUK. writing and de- bugging of the SBC's console and printer requirements by just opening or closing links on the PCB. The same configured version of CP /M 2.2 is available for various Disk sizes. A complete Development System and Desk Top Computer based on this board is available with a variety of Disk Drive sizes and case styles to suit users requirements and environment. n EEsE I%,_I I l r WHERE VISION AND TECHNOLOGYJ MEET Tel (0294) 75000/73333

CIRCLE 85 FOR FURTHER DETAILS. CIRCLE 70 FOR FURTHER DETAILS. ELECTRONICS & WIRELESS WORLD JUNE 1985 9

www.americanradiohistory.com 1000's OF BARGAINS 1 COMPUTER WAREHOUSE FOR CALLER at TED 'ALADDIN'S' OAVE OP COMPUTER AND ELECTRONIC E 6 UIPMENT far Anderson Jacobson MOT LINE DATA BASE RECHARGEABLE BATTERIES AJS10 VIDEO Dry Fit Maintenance FREE by Sonnenschein. DISPLAY TERMINAL A300 07191315 12v 3 AH same as RS 591-770 NEW Made the RS 591 © by one of USA's £13.95 A300 071 91 202 6 -0 -6 1.8 AH same as DISTELdial up data base Miniature PCB mount 3.6v 100 THE ORIGINAL FREE OF CHARGE largest peripheral manufacturers 382 EX EQUIP £4.99 items and one off bargains the AJ510 Professional VDU Mah as RS 591477 NEW £1.00 SAFT VR2C 1.2v "C" 1000's of stock size NICADS in 18 cell ex equipment pack. Good condition ON LINE NOW 300baud, Çtols,8bit terminal has too many - easily split to single cells C10.50 + pp C 1.90 word. no parity features to include in space 01-679 1 YO available - just a few are: internal Z80 cpu control, very readable 15" non glare green EX -STOCK INTEGRATED CIRCUITS MAINS FILTERS screen, 24 lines by 80 characters, 2732 ex equip £3.25. 27128- 250ns NEW £12.00. Cure those unnerving hang ups and data glitches caused 128 ASCII character set with lower 8118 -200 £4.50, 6116 -250 £3.95, by mains interference news letter matchbox case and graphics, standard RS232 interface, Cursor 6264LP-150 £22.00. 4164-200 C3.50,4864-150 £4.00, SD5A As recommended by ZX81 addressing, numeric key pad etc Supplied in good 4116- 300 ,£1.20,2114£1.75.6800£2.50,6821 £1.00, size up to 1000 wan load E5.95 TESTED second hand condition with full manual £14.50, L2127 compact completely cased unn with 3 pin fitted 68A09 £8.00, 68809 (10.00, 88809E £225.00 + Carr £ 10.00. Data sheet on request. D8085AH -2 £1 2.00, D8086 £20.00, 280A £2.99. cncket Up to 750 watts E9.99 000Inf TAP A over production problems, and a special Keep your hot parts COOL ¡d ABLE Major company's with our range Of BRAND NEW professional cooling fans BULK PURCHASE enable TWO outstanding offers. ETM 99111101 Dim. 92 a 92 a 25 mm. Miniature 240 v equipment tan complete with Mar guard £9.95. COULD JB-3AR Dim. 3" a 3" a 25" compact v NEW £6.95 MONITOR SPECIALS running 240 operation. COLOUR very Quiet B UHLER 69.11.22. 8 -16 v DC micro `SYSTEM ALPHA' 14" Multi Input Monitor. miniature reversible fan Uses a brushless Made in the UK by the famous REDIFFUSION Co. for their own professional servo motor for extremely high air flow, y computer system this monitor has all the features to suit your immediate and future almost silent running and guaranteed 10.000 monitor requirements. Two types of video input, RGB and PAL Composite Video, hr life. Measures only 62 x 62 x 22 mm. allow direct connection to most makes of micro computers and VCR's. An internal Current cost C32.00. OUR PRICE ONLY with data. 0 speaker and audio amplifier may be connected to your system's output or direct to £12.95 complete Many features MUFFIN -CENTAUR standard 4" a 4" x 1.25" a VCR machine, giving superior colour and sound quality. other fan supplied tested EX EQUIPMENT 240 vat include PIL tube, Matching BBC case colour, Major controls on front panel, C6.25 or 110 v at C4.95 or BRAND NEW 240v Separate Contrast and Brightness - even in RGB mode, Two types of audio input, at £10.50. 1000's of other fans Ea Stock Separate Colour and audio controls for Composite Video input, BNC plug for all tans C1 6 11 for Details. Post 6 Packing on composite input, 15 way 'D' plug for RGB input, modular construction etc. etc. BUDGET RANG This must be ONE OF THE YEAR'S BEST BUYS!!! Supplied BRAND NEW and BOXED, complete with DATA and 90 day guarantee. VIDEO MONITORS SUPPLIED BELOW ACTUAL COST -ONLY £149.00 + Carr. At a price YOU can afford, our range of EX EQUIPMENT video monitors defy DECCA RGB 80 -100 Monitor. competitionii All are for 240v working with hardly used manufacturer's surplus enables us to offer this special are Little or standard composite video input. Units converted DECCA RGB Colour Video TV Monitor at a super low price of only pre tested and set for up to 80 col use on interface, safety where MINOR screen £99.00, a price for a colour monitor as yet unheard oft! Our own BBC micro. Even PIL with the tried and burns MAY exist - normal data displays are modification and special 16" high definition tube, combine unaffected. tested DECCA 80 /100 series chassis to give 80 column definition and picture SOLD TO DATE quality found only on monitors costing 3 TIMES OUR PRICE. In fact, WE 12" KGM 320 -321, high bandwidth input. GUARANTEE you will be delighted with this product, the quality for the price has to will display up to 132 columns x 25 lines. be seen to be believed. Supplied complete and ready to plug directo to a BBC Housed in attractive fully enclosed MICRO computer or any other system with a TTL RGB output. Other features brushed alloy case. B/W only £32.95 include internal audio amp and speaker, Modular construction, auto degaussing 24" KGM large screen black 8 white 34 H x 24 D, 90 day guarantee. Supplied in EXCELLENT condition, ONLY £99.00 monitor fully enclosed in Tight alloy case + Carr. Also available UN-MODIFIED but complete with MOD DATA Only £75.00. Leal sch I shops. clubs etc NLY£55.00 Carriage £ 10.00 Carriage and Insurance on monitors £10.00

SPECIAL 300 BAUD MODEM OFFER EX STOCK Another GIGANTIC purchase of these EX BRITISH TELECOM, BRAND DATA MODEMS NEW or little used 2B data modems allows US to make the FINAL REDUCTION, and for YOU to on the exciting world of data DEC CORNER Join the communications revolution with £29.95. Made to our super range of DATA MODEMS with communications at an UNHEARD OF PRICE OF ONLY PDP 1140 System comprising of CPU. prices and types to suit all applications the highest POST OFFICE APPROVED spec at a cost of hundreds of 124K memory + MMU 16 line RS232 and budgetsii 2B has all the standard requirements for data base, interface, RPO2 40 MB hard disk drive. pounds each, the TU10 9 track 800 BPI Mag tape Most modems are EX BRITISH All this and more!! drive. dual made to the highest business or hobby communications. rack system. VT52 VDU etc. etc. Tested TELECOM and are modes standard for continuous use and reliability. 300 baud full duplex CALL. ANSWER and AUTO and running £3750.00 vlt k Standard RS232 serial interface RS232 interfaces are standard to all our Full remote control BA11 -MB 3.5" Box, PSU. LTC £385.00 Built in test switching modems, so will connect to ANY micro etc. CCITT tone standards NOW ONLP DH11 -AD 16 x RS232 DMA with an RS232 serial interlace. Supplied with full data £29,95 240v Mains operation interface £2100.00 1 year full guarantee 2B SPECIAL OFFER centre of Modular construction firM. DLV11 -J 4 x EIA interface £310.00 DATEL see Just 2 wires to comms. line this ad. Direct isolated connection , ¡ DLVII -E Serial. Modem support £200.00 MODEM 13A, 300 baud. Compact unit only Order now - while stocks last. Carriage and Ins. £10.00 DUP11 Sych. Serial data i/o £650.00 2' high and sanie size as telephone base. D0200 Dilog - multi RK Standard CCITT tones. CALL mode only controller E495.00 Tested with data. ONLYE45.00 + PP E4.50. -B mua £650.00 MODEM 20-1, 75-1 200 baud. Compact unit SUPER PRINTER SCOOP DZ11 8 line RS232 board for use as subscriber end to PRESTEL, riso KDF11 -8 M8189 PDP 1123+ £1100.00 MICRONET or TELECOM GOLD. Tested with LA36 Decwriter EIA or 20 ma loop £270.00 BRANO NEW The "Do Everything Printer' al a ice that will data E39.95 + PP 56.50. NEVER be repeated Standard CENTRONICS LAX34 -AL LA34 tractor feed £85.00 -1 1200 -75 MODEM 20 -2. same as 20 but CENTRONICS pere llsl interface for direct connection to BBC, MS7 1 -JP Unibus 32 kb Ram £80.00 baud E99.00. OR IC. DRAGON etc. Superb pont quality th lull MS11 -LB Unibus 128 kb Ram £450.00 TRANSDATA 307A. 300 baud acoustic %.3Z` pin addressee. graphics and 4 type fonts plus MS11 -LD Unibus 256 kb Ram £850.00 coupler. Brand new with RS232 interlace. HIGH DEFINITION internal PROPORTIONAL SPACED MODE for WORD PROCESSOR applications 80-132 MSC4804 Obus (Equiv MSV1 1 -L) ONLY £49.95 columns, single sheet, sprocket or roll paper hendling plus 256 kb £499.00 DACOM DSL2123 Multi Standard Modem, much more Available ONLY Irons DISPLAY ELECTRONICS PDP11 /05 Cpu, Ram, i /o, etc. £450.00 switchable CCITT or USA BELL 103 standard. at the ridiculous price 011101 IEOM.M + VAT Complete with V21 300-300, V23 75-1200. V23 1200-75 or lull manual etc Limitad quantity -Harty while stocka last PDPI1 /40 Cpu, 124k MMU £1850.00 1200-1200 half duplex. ;N;+9 Options. Interlace cable (specify) for BBC. ORIC. RT11 ver. 38 documentation kit £70.00 Auto answer via MODEM or CPU CALL or f.t T DRAGON or CENTRONICS 36 way pig £12 .50. Spare ribbon RK05 -J 2.5 Mb disk drives £650.00 ANSWER modes plus LED status indication. £3.50 each BBC graphic. screen dump utility program £860 KL8JA PDP 8 async i/o £175.00 Carnage ana ins. £ i0.00 s VAT Dim 2.5" x 8.5" x 9' BRAND NEW fully MI8E PDP8 Bootstrap option £75.00 guaranteed ONLY 061.00 + PP E4.50. VT50 VDU and Keyboard - DATEL 2412 Made by SE LABS for BT this current loop £175.00 for data links at HUNDREDS OF PRINTERS two part unit is synchronious VT52 VDU with RS232 interface E250.00 1200 or 2400 baud using 2780/3780 Office for Details. protocol. Many features include Auto answer. EX STOCK FROM £49.00. Call Sales 2 or 4 wire working etc. etc. COST OVER 1000's of EX STOCK spares for DEC PRICE E185.00. PDP8, PDP8A, POP11 systems 8 £800. MIR 1 1036 AO 3 pen drum plotter and DATEL4800, RACAL MPS4800 high speed only large CALCOMP peripherals. Call for details. All types of good condition E1f.00 CARR E10.00 offline 915 magtape controller. Good working order. Computer equipment and spares wanted £2500.00. for PROMPT CASH PAYMENT. ADO VAT TO ALL P ' ICES All prices quoted are for U.K. Mainland, paid cash with order in Pounds Sterling PLUS VAT. Minimum order value £2.00. Minimum CreditCard orderE /0.00. Minimum BONA FIDE account ordersfrom Government Depts., Schools, Universitiesand established companiesf20.00. Where post and packing not indicated please ADD £1.00 + VAT. Warehouse open Mon -Fri 9.30 -5.30. Sat 10.30 -5.30. We reserve the right to change prices and specifications without notice. Trade, Bulk and Export 1=1 32 Biggin Way, Upper Norwood, London SE19 3XF L 1\ S f ¡IL j Telephone 01 -679 441 4 Telex 894502 Data 01 -679 1888 ,J

& WIRELESS WORLD JUNE 1985 10 ELECTRONICS

www.americanradiohistory.com ERS - PRINTERS - PRINTERS - AR/ TERS PR INTERS - PRINTERS - PRINTERS PR/ SUPER DEAL? NO - SUPER STEAL!! GE MODEL CE TERM1!PRIfNT6R The FABULOUS 25CPS TEC Starwriter 30 RANDNEVI At ONLY £4 +VAT - - ii_i Made to the very highest ' - spec the TEC Sterwrlter FP1500.25 features a heavy duty die cast 1 chassis and DIABLO type print mechanism giving A large purchase of these stand alone superb registration and LOW print quality. Micro- terminal units offers an EXTREMELY processor electronics PRICE for a professional printer for direct A massive purchase of these desk top offer mandcompatOUME connection to your micro. The printer has a printer -terminals enables us to offer you a fraction standard RS232 serial interface with these quality 30 cps printers at a SUPER command computability of its LOW PRICE against their original cost of and full control via CPM Wordstaretc. original switchable rates of 110, 200 and 300 over £ 1000. Unit comprises of full OWERTY, Many other features include bi directional cost. baud. Upper and lower case characters electronic keyboard and printer mach with printing, switchable 10 or 12 pitch, full width 381 mm paper handling with upto are printed by a matrix head with charac- print face similar to correspondence quality 163 characters per line, friction feed rollers for single sheet or continuous paper ter widths up to 132 columns. Unit accepts typewriter. Venable forms tractor unit internal buffer, standard RS232 serial interface with handshake. standard fan fold sprocket fed paper from enables full width - up to 13.5" 120 column Supplied absolutly BRAND NEW with 90 FREE wheel paper, upper - lower case, standard RS232 day guarantee and daisy 4" to 9.5 ". Many other features such as and dust cover. Order NOW or contact sales office for more information. serial interlace, internal vertical and Optional extras RS232 data cable £10.00. Tech manual £7.50. Tractor feed numeric keypad, electronic keyboard, auto horizontal tab settings, standard ribbon floor £140.00. Spare daisy wheel £3.00 Carriage & Ins UK Mainland) £10.00. motor on /off and FREE stand. adjustable baud rates quiet operation plus Supplied in good S/H working condition - many other features. Supplied complete complete with manual ONLYE95.00 with manual Guaranteed workingLIAO.M or untested L55.00, optional floor £ 12.50 OFFER CARRIAGE 6 INS. E10.00 stand ROFESSIONAL KEYBOARD Carr 8 Ins £ 10.00. An advantageous purchase of brand new surplus allows a great OWERTY, full travet, chassis keyboard offer at fractions of their original costa. ALPHAMERIC 7204/80 full ASCII 60 key upper, lower + control key, parallel TTL output plus strobe. Dim 12" a 6" +58-12 DC.LW.M. EXTEL PRINTERS TELETYPE ASR33, ., DEC LA34 Uncoded keyboard with 87 quality, GOLD, normally open switches on standard X, Y matrix. Complete with 3 LED indicators 8 i/o cable - ideal micro EX NEWS SERVICE compact, quality I/O TERMINALS conversions etc. pcb DIM 15" x 4.5" In MI Carriage on keyboards £3.00. built 50 column matrix printer, type AE11. FROM EI95 + CAR. +VAT Unit operates on 5 BIT BAUDOT code Fully fledged industry standard ASR33 data ELECTRONIC from current loop, RS232 or TTL serial terminal. Many features including ASCII COMPONENTS interfaces. May be connected direct to keyboard and printer for data I/O auto data EQUIPMENT micro, or comms receiver via simple filter detect circuitry. RS232 serial interface. 110 66% DISCOUNT reader for Due toour massive bulk purchasing programme which enables us to bring you the best possible network to enable printing of most world baud 8 bit paper tape punch and off line data ridiculously bargains. we have thousands of I.C. s. Transistors. Relays. Cap's. P.C.B's. Subassemblies, wide NEWS, preparation and TELEX and RTTY services. in Switches, etc. etc. surplus to our requirements. Because we don t have sufficient stocks of any cheap and reliable data storage. Supplied Supplied in tested second hand condition good condition and in working order one item to include in our ads. We are packing all these items into the 'BARGAIN PARCEL OF A with 50 and 75 baud xtals, data sheet and LIFETIME. Thousands of components at 'giveaway paces, Guaranteed to be worth Options: Floor standE I1.í0 +VAT large paper roll. ONLYE49.95. at least 3 times what you pay. Unbeatable value!' Sold by weight. ' KSR33 with 20ma loop interlaceE /25.00 + Dimensions 15" D x 5" H x 10" W Sound proof enclosure E25.00 + VAT 2.5kIs E4.25 + pp £1.25 5kIs ES.90 + £1.80 I CARR E6.00 Spare paper rolls £4.50 each Okls E10.25 + pp £2.25 20 kls E17.50 + £4.75 20,000 FEET OF ELECTRONIC AND COMPUTER GOODIES ENGLAND'S LARGEST SURPLUS STORE- SEEING IS BELIEVING!! D.C. POWER SUPPLY SPECIALS DUAL DISK DRIVE/ SEMICONDUCTOR Experlmentors PSU ExGPO. All silicon electronics. Outputs give +5v @ 2 amps +12v @ 800 ma -12v @ 800 ma +24v @ 350 ma and 5v floating @ 50 ma. WINCHESTER CASES Dim 180 x 120 x mm. All are fully regulated and short circuit proof. `GRAB BAGS 350 outputs Very smart, fully enclosed case unit Mixed Semis amazing value contents in NEW with Supplied or little used condition. Complete circuit. include transistors, linear. I.C,'s £1 +2 custom made to accept two full digital, triaca Only 5.50 £2.50 pp diodes, bridge recs., etc, All FARNELL Volt 40 amps. Type number G6-40A. This miniature switching PSU 51/." floppy disk drives or two etc. devices 5 height guaranteed brand new full spec. with manu- measures only 160mm wide 175mm deep and 90mm high, yet delivers a massive 51/4" winchesters such as the facturer's markings, fully guaranteed, 40 120 amps!! Fully regulated and smoothed with over voltage protection etc. or RHODIME RO200 or TANDEM 50 +0.05 100 +/1.15. 240 volts AC input. NEW and boxed with circuit at a fraction of Supplied BRAND TTL 74 Series A gigantic purchase of an the list price. + cart 8 Ins. series etc. An internal switched current Only £130.00 £3.00 across the board range of 74 TTL series LAMBDA SV AC input with 5 volts 10 mode PSU supplies all the required LMCC BRAND NEW 240v DC at 8 to C's enables us to offer 100+ mixed amps fully regulated output. Completely enclosed unit measures only 9" x 4" x 5" voltages to enable you to plug in "mostly TTL" grab bags at a price which two £29.99 your drives and go!! or three chips in the bag would nnormally LAMDA LMCCSV 110v AC input with 5 volts DC at 8 to 10 amps fully regulated Other features include mains filter, cost to buy. Fully guaranteed all I.C.'s full output. Slightly smoke damaged, hence ONLY £10.95 spec 100 +16.50 200 +EIl.30 300 +119.10 PERIPHERAL SYSTEM SUPPLY. Runs almost any system. Fully cased unit internal cables with standard drive supplied In a brand new or little used condition. Outputs give 5v @ 11 amps "+" connectors, space for internal PCB, 15-17v @ 8 amps " -" 15 -17v @ 8 amps and " +" 24v @ 4 amps. All outputs are standard fan cut out and mounting, NORTH STAR HORIZON crowbar protected and the 5 volt output is fully regulated. Fan cooled. Supplied tested with circuit. £55.00 + £8.50 car!. air filter. Overall dimensions Pro 5100 system with dual 5" floppy 1000'a of other POWER SUPPLIES EX STOCK - 28 cm W x 30 cm D x 19 cm H drives, software, manuals etc. CALL SALES OFFICE FOR DETAILS ONLYE55.00 +16.00 CARR. £850.00 Call sales office for details

ULTRA COMPACT 300 BAUD PROFESSIONAL 8 FOOT LOGICAL KEYBOARD 19" RACK CABINETS Heavy duty unit in attractive satin alloy LARGE 19" equipment cabinet. Totally case. 55 full travel keys are laid out in a ACCOUSTIC MODEM COUPLER logical format of: - enclosed with locking front and rear A Major manufacturer's over production and a bulk buy doors. An internal sub fram 63" high is pre special enables us to offer this BRAND NEW drilled for standard 19" TRANSDATA 307A ultra compact, BT APPROVED, equipment etc. Other 300 baud full duplex accoustic modem at a fraction of features include internal _' manufacturer's list price. The unit operates on the 12" cooling fan, two - iflhi!' tone blue and grey 0e111s standard CCITT V21 frequencies with RS232 finish with alloy trims. Making a very useful keyboard, idea fo interface via 25 way 'D' skt. on 4 heavy Mounted persons unfamiliar with or confused by the Combine the adjustable cup system, which duty castors, mains standard OWERTY layout. All keys generate fits almost any phone with the benefit of ' panel etc. And at a the equivalent ASCII outputs and various "No jacks or phone cables" and a light current cost from control codes shown in data. A 7 bit latched < IMHOFS weight of only 1.2 Kg and you have a truly of over parallel TTL output with strobe enables £500 A snip at ONLY direct connection to any similar micro port portable modem!! Supplied complete with £125. Supplied in NEW etc. Many other features such as internal data, 90 day guarantee and ready to use. or little used condition. 240v to 5v PSU MAINS CN /OFF switch. Carriage £22.00. Supplied In NEW or little used condition Ext. Dim 72.5 "h x with data. ONLY £25.95 Post and packing £4.50 ONLY £49.95 + £3.00 pp 23.5 "w x 26 "d 1000's of other EX STOCK items including POWER SUPPLIES, RACKS, RELAYS, TRANSFORMERS, TEST EQUIPMENT, CABLE, CONNECTORS, HARDWARE, MODEMS, TELEPHONES, VARIACS, VDU'S, PRINTERS. POWER SUPPLIES, OPTICS, KEYBOARDS etc. etc. Give us a call for your spare part requirements. Stock changes almost daily. I Don't forget, ALL TYPES and QUANTITIES of electronic surplus purchased for CASH

CIRCLE 63 FOR FURTHER DETAILS.

ELECTRONICS & WIRELESS WORLD JUNE 1985 11

www.americanradiohistory.com LOW 1 SERVICE BUSINESS SYSTEMS LTD PRICES 66, MAPLE DRIVE, EAST GRINSTEAD, WEST SUSSEX, 5H19 3UR ADVICE

The PC-16 16-bit computer provides PERFECT COMPATIBILITY with the IBM PC /XT range. The motherboard can be supplied in two versions for stereoscopic conveneince. The 'N' version has no memory on board and the 'B' version with space for 64 to 256K RAM. Addition of the Memory Expansion Card provides a further 64 to 512KB of RAM. BASIC FEATURES INCLUDE: * 8088 CPU operating at 4.77 MHz * RUNS MS /PC -DOS & CP /M 86 * Provision for 8087 co- processor * READS & WRITES IBM -PC format * Four DMA channels * Accepts IBM -PC Peripherals * Three TIMER channels on board * Up to 256K RAM ON BOARD * 8 EXPANSION SLOTS SYSTEM -5 PC16 (B/3) - PRICE £1599 - Main computer employing 'B' board with 128K on board (upgradeable to 256K on board) PLUS Colour /Graphics adaptor providing signal capable of running monochrome displays on RGB output for full colour. Multi I/O card, providing floppy drive controller for two drives, one parallel port, one serial port, one games port with batter backed clock calander. RAM extension card for 512K. Two DS /DD floppy drives. 83 -key keyboard. All complete, built & tested in case with power supply together with Concurrent (multiuser, multitasking)CP/M,CCP /M manual, Basic manual and computer operations manual - ready to run!

MOTHERBOARD 'B', 8 -slot, Sanyo DMC 7650 IBM /Apricot MR521 10MB Hard drive £523 DRIVES - MEGABYTES FOR 128K £490 colour monitor £349 MR522 22MB Hard drive £735 MICROPOUNDS! MOTHERBOARD' N', 8-slot £395 12in HI -RES GREEN MON £84 IBM COMPATIBLE KEYBOARD (83 5" Height 500KB 40/80 £119 MULTIFUNCTION card with 128K 64K RAM EXTEND MODULE £18 key) £139 5" Height 1 MB 40/48 £125 (expandable to 256K) one PLL-port, TEAC 55B DS /DD Floppy drive..£172 KEYTRONIC 5150 K /BOARD £175 5" Height 1.6MB 40/80 £159 one SER -port (2nd option) Clock/ WD 1002 SWX -2 Winchester KEYTRONIC 5151 K/BOARD £210 5" Height 2MB 40/80 £199 Calendar with backup £195 controller £249 130 watt Switching Power 5" Height 500KB £119 MONOCHROME /Graphic adaptor 512K Expansion RAM card - comes Supply £160 3" Height 1 MB £125 with printer port £279 with 128K RAM installed fully IBM Add on serial port kit £23 8" Full Size 1.6MB £309 MULTI I/O CARD - one pli, one compatible £119 FDD-100 drive controller for 4 8" Size 1.6MB £282 serial port, one games port, floppy PC Case £112 drive £96 All brand new, uncased, with full electronics - drive controller, clock calender with standard power requirements. battery backup £256 Full documentation and technical details available.

Add 15% VAT to all prices given. Remember, VAT is also applicable on carriage at 15%. Terms CWO. DEALER ENQUIRES WELCOME. FOREIGN enquiries if possible by telex please. However, French & German speaking staff at your disposal. MONEY BACK GUARANTEE. SEND E1.00 for our latest catalogue of over 3000 Items, computers, peripherals. consumables, robotics, et( etc **,TEL: (0342) 313427.24631/2 YMlxK140 TLX: 357547* CIRCLE 86 FOR FURTHER DETAILS.

LINEAR ICs OPTO FO CLIPS 3 t® -rimer 17.40 556 21 M1926 1.80 CT100oKB Cluck 3rnm :ea 9 5mm red 9 40 M1927 1.80 CT6000 t Programmable 1nm green 12 Smm peen 12 556 A M1928 ONE 110 CHUM 741 72 Timer 3910 3nm Yellow 12 5mm yellow 12 1.00 XK114 Reay Kit for above 190 Rectargur spwe crow a 748 30 641.929 MM71C911 6.50 X0101 Electronic Lock 11.50 Iron/pear Mat taco 00590 3.30 Industrial Computer AY38910 390 MM7/C915 96 X0102. 3-Note Door Chime 5.50 Red 15 Green Il Yellow 10 CANSO 85 MM71C922 3.90 XKt04 Solid State Switch 2.40 &cob. 65 Hashing Red 50 CA3130 85 MM74C9261.50 XK112 Moms Wiring Remote I celas Red, 42.00 CA3140 10 NE567 125 Control Round 32 Continuous 55 IC17107 8.66 55660 210 1111111011414111111 X0113 MW Radio 5.50 Rectangular 45 ICL7126 8.00 S5760 220 XK120 DVMIThemomete 15.50 1174110111 55 M0C3020 1.10 ICM7555 95 SA80529 3.50 DL10130K 4th Light Chaser 15.95 X074 070 MOC3040 1.50 8.95 011038 3.10 SABOS00 2.50 OLZ1000K 4th light Chaser ORPI2 75 MEIJI 35 DIA11 Opto Input for above 70 LF351 40 SL41) 1.95 Seven Segment LED Ospays 0L3000K 3-Ch sound to light 12.95 1F353 70 SLUt 1.35 DI7O4 3 cc 75 4 ON 117 cc T0300K 300W Toudidimmer 735 LP356 80 SL486 1.85 t F505005 ca 115 DIRECT DRIVE 40 2.05 TS340K t 300114 Touchswitch 7.75 LM324 SL490 END5015 ca K Osplay 7.00 LD340K t 300W Lightdimmer 3.95 1M3312 85 TBAB 70 TDR300K t IR Remote Controlled 400V TRIACS LM335z 120 TBA810AS 90 Ughtchmmer 14.95 1M339 40 T001024 120 4A 49 8A 5B MKS' IR Transmitter for 111348 55 TDA1290 1.96 TOR300K b MK7 4.50 12A OS 160358 Y TL061 40 isolated 65 16A ï 3 TOEIK t Touchdimmer En. 2.50 BA 95 LAM 120 TL062 60 + 25A 2.10 71.044 1.30 TSA300K 1 Time Delay Touch 1M361 1.40 BA sensitive 66 Lac 18 IM382 1.10 TL071 45 . Switch 1300141 5.00 . .. . 7.. MK1 Thermostat 4.60 1.61336 N 11072 70 MK2 Solid State Relay 2.60 SPECIAL OFFERS LM1035 3.85 11074 1.30 MK4 Proportional Temperature 2716 3.10 2800 PIO 1.98 1.641456 34 TINI 35 £258 Controller 6.50 2732 3.20 ZBOA CPU 1.99 LM2911 190 T1002 48 MK5 Mons Timer 4.50 2764 4.20 6871 1.40 LM3900 BB TLDB4 1.00 MK7 Single-channel IR Recover 77128 7.50!! IM3908 M T1170 50 * Control BASIC and Z80 Assembler Language 1.75 11507C 120 12401/1 10.50 1503911 On Board EPROM Programmer MK9 4-way Keyboard 1.90 COMPONENT PACKS 1M3914 2.40 TMS1121 8.50 * MK10 16way Keyboard 5.40 1603915 2.40 TMS1601 9.50 Detachable Hand -Held Keyboard and Display 1 650 Resistors 47R IOM * MK11 1Othannel 1.3 analogue LM13600 1.10 UA2210 1.45 10 po value 4.00 * 4K Bytes of Battery Backed Memory olp IR Receiver 13.50 LS7210 1.75 18.N2M3 75 2 10 I6V Electrolycs 10 1000t MK12 16-channel IR Receiver 13.50 1S1220 2.75 ULN21104 75 * Up to 64 Relay Outputs 5 per value 125 MK13 11way Keyboard 4.35 157225 2.60 ZN414 BO 3 60 Polyester Capacitors * Up to 64 Opto- Coupled Inputs AC Power Controller 5.20 ME 10C 2.97 25425 3.40 MK14 001 laF 250V 5 values 555 MK15 Dual Latched SS Relay 4.50 ML922 3.10 2N127 5.70 * 4 Analogue Inputs 4 45 Resets 1000 1M 3 00 MK16 Mains-powered IR M1924 2.50 ZN428 4.50 5 30 low Ratite IC Sockets * 1 Analogue Output Transmitter 3.50 181.925 2.10 1741031E 1.80 8 14 b 16 pm 240 MK17 Single-channel IR NOW IN STOCK SP0256A02 1.15 * RS232 Interface 6 75 Red LEDs t5mmi 1 75 Receiver 112\1 10.50 * Cassette Back -Up Memory Mktg Coded IR Transmitter 6.80 We stock: VERO, 28pa4e * Real Time Clock MK19 DC Controlled Audio VEUEMAN KITS. catalogue sard906 SAE today! Amplifier 1030 PANTEC KITS, TebphoneOrders Access&BarcdayCard solution to all 'Includes box. t Includes Xontpanel. ANTE? IRONS, The Chum One A offers the complete 01 -567 AO kits include PCBs, components BOOKS FROM RING 8917124Fks) measurement and control problems. Programs can be Five She Seven Eight NneTen and assembly Instructions. BABANI. T.I. in RAM then at a touch of a For further details send S.A.E AND ELEKTOR. written, tested and modified blown into an EPROM. ORDERING INFORMATION: ALL PRICES EX- switch CLUDE VAT. FREE PSP on orders over 020 (UK 11 -113 BOSTON RD only) othermse add 75pVAT. Overseas PEP Europe WARWICK DESIGN GROUP, 12 ST. GEORGE'S ROAD LONDON W7 3SJ 12.75. EhaaS se E550. Send c heprelPO18ar4ayardl Access No with order. Giro No. 529314002. Tel Orders 01 567 8910 LEAMINGTON SPA CV31 3AY (0926) 34311 AND EXPORT ORDERS ENOUIRIES- 01 579 9794 LOCAL AUTHORITY SUBJECT TO Shop Hours Mon Rh 9am 5pm WELCOME. GOODS BY RETURN Sal 10am 4pm AVAILABILITY. CIRCLE 87 FOR FURTHER DETAILS. CIRCLE 9 FOR FURTHER DETAILS. 1985 12 ELECTRONICS & WIRELESS WORLD JUNE

www.americanradiohistory.com TWO STAGE GASFET TYPE 9048 TYPE STRIPLINE PREAMPLIFIERS Tuned to your specified TMOS WIDEBAND LINEAR 9010 POWER AMPLIFIERS. 4W'1f1W »("(.-( watts RF output. Without channels in bands IV or V tuning. Power gain 10dB. 24V. + supply TYPE 9046 100KHz.-100MHz. 4 watts £84.50 +£3.50 p &p TYPE 9051 15MHz.- 200MHz. 4 watts £84.50 +£3.50 p &p TYPE 9171 15MHZ.- 200MHz.10 watts £140.00 + £8.00 p&p TYPE 9002 Two stage Gastet preamplifier. N. F. 0. 7dB. Gain 25dB. High ()filter £85 +£2p&p TYPE 9172 As above with integral power supply unit TYPE 9004 UHF two stage Gasfet preamplifier. N.F. 0.6dB. Gain 25dB. Aligned to your specified £200.00+£ 15.00 p&p TYPE frequency in the range 250- 500MHz. High 0 917415MHz.- 200MHz. 20 watts C180.00 + £8.00 p&p filter +£2 TYPE 9175 As above with integral mains power £85 p&p supply unit TYPE 9012 Gasfet preamplifier mains power supply unit £24.50+ £3 p&p £240.00+ £ 15.00 p&p TYPE 9010 Masthead weatherproof unit £9.50 + 52 p&p

TYPE 9152 TYPE 9159 TELEVISION LINEAR POWER AMPLIFIERS. Tuned to your specified channels in bands IVorV. (or 400- 900MHz). TYPE 9061 150mV. input, 10mW. output £140 +C5 p&p TYPE-91-52 i0mW. input, 500mW. output £180 +£5 p&p TYPE-9159 500mW. input, 5 watts output £210 +C5 p &p TYPE t' -...... , TYPE 9006 - 9035 GASFET RF PREAMPLIFIERS. Aligned to your specified frequency in the range 30- 250MHz. Masthead or local use. TYPE 9157 TYPE 9006 N.F. 0.6dB. Gain 10 -40dB. variable £65.00+ £2 p&p TYPE 9006FM As above. Band 1188- 108MHz £65.00+ £2 p&p TYPE 9035 Mains power supply unitfor above types £24.50+ £3 p&p

TYPE TYPE 6034 9155 i9St TYPE 8034 PHASE LOCKED SIGNAL SOURCE using low frequency reference crystal. Specify TMOS RF LINEAR POWER AMPLIFIERS. Tuned to your specified frequency in the range 10- output in the rance 1- 600MHz. Output 1 Om W. +10dBm £84.50 +£2 p&p 250 MHz. TYPE 9190 80 WATT COLOUR TELEVISION TRANSMITTER. 40 -250 MHz. American, British or Continental system TYPE.910.510mW.Input, 3 watts output £160.00 +£10.00 p&p f1500.00 TYPE 91553 watts input, 30 watts output £240.00+ £ 10.00 p &p TYPE 9191 10 WATT COLOUR TELEVISION TRANSMITTER. UHF bands IV or V American. TYPE 9156 As above with integral mains power supply unit £320.00 +£f5.00p &p British or Continental system £ 1500.00 TYPE 9106 100 mW. input, 10 watts output £180.00 + £ 10.00 p&p TYPE 9086 FM TRANSMITTER 88- 108MHz. 50 watts RF output. 24V + supply. Complete mod- TYPE 915810 watts input, 80 watts output £320.00+ £ 10 p &p ular system . £480 +£30 p&p TYPE 9157 As above with integral mains power supply unit £400.00 +£15p&p TYPE 9087 As above with integral mains power supply unit £540+£40 p&p RESEARCH COMMUNICATIONS LTD. rAs p4Eps UNIT 3, DANE JOHN WORKS, GORDON ROAD, CANTERBURY, KENT CT1 3PP oN °j P` TELEPHONE: CANTERBURY (0227) 456489 CIRCLE 80 FOR FURTHER DETAILS.

WIWKIAKARO ASCO SOLENOID VALVES SPECIAL OFFER. CLAUDE LYONS VOLTAGE SPECIAL OFFER Fantastic value!! These valves are STABILISER. Input 210-270V HIGH-GRADE a.c. Output 240V ISOLATION TRANSFORMERS . designed for air gas water L.T. Oil nor- a.c. ±5%III Rated at 2.9k0Á. Ideal for stab malty closed. Approx '" bore ideal for lising computer supplies Open frame terminal block connections CREDIT. CARDS MS0NS E1% Inc Carriage (ELECTRONICS) LTD. central 240 ac our price £9.50 inc ACCEPTED FOR carting only a left 240V,250 want, open frame typeltag connec- 9-10 Chapel Street, Marylebone TELEPHONE tions,£10, P&P E2, VAT E1.80. Pri 100-110.200. JOYSTICK CONTROL London NW1 5DN ORDERS GOULD ADVANCE P.S.U.s. 13.8V 30amp d.c. 210 -220- 230 -240 -250V, Sec 220- 230 -240V Joystick controls made for the video game supplies. Great for linearstll ONLY E65 Inc. 6001N, can be used in reversed open frame 21 -23 Bell Street, London, NW1 industry with sturdy micro switch action. 2 way VAT. Carriage0 Limited offer connections, E7ó, Carr. control C1.95 inc VAT 8 post. 2 way heavy service 01- 2625125 &01 -7237851 type 02.95 inc VAT 8 cary. 4!ryC180tVATE2..571ock 6000w CONSTANT VOLTAGE TRANSFORMER PARMEKO NEON TRANSFORMERS We are stockists of the complete range of "DOUGLAS" transformers. DIGITAL CLOCK MOVEMENTS BY REGAVOLT PRI tapped 200- 220 -230-240 -250V. Size 7000V Please ring or send S.A.E. for details. A well made clock 'movement' fitted with This high grade piece of equipment has inputs 55 M /A. Totally enclosed in wall mounting timer mechanism and neon illumination. Size of either 220 or 240V a.c. - 20% + 12% steel case. Size 912x812x412in. approx 110mmx 50mmx 50mm 240V a.c. Output 220 or 240V + - 1% Please Note This £17.50 inc. VAT and carriage Precision made Swiss D.C. motor running operation. A Snip £3.95 inc VAT & Carraige C.V.T. Has Isolated SecOndgrjes 1 SAMP ISOLATION At 1 PRI tappedPaged -2500. Size 5000V on 6 -9v dc these motors have a 70:1 Size 17.5'x 11.55'x226"WWeI ht3cwt 202223240 gearbox and are extremely powerful) TRANSFORMERS BY FAMOUS Price £550 inc VAT Ring for carriage details 20 M /A. Totally enclosed in wall mounting size 26 mm x 45mm 3mm output shaft nor- MAKERS Note: this transformer is ideal for computer steel case. Size 7x6x5in. mal cost over £20 our price £4.95 Inc VAT These high grade transformers are as 9v 800m /a DC SUPPLIES P.S.U.s J £12.50 inc. VAT and carriage 8 postage. new and were manufactured for a top As made for afamous micro computer firm U.K. electronics company to extremely a high standards. Each transformer has a these units have mains lead and stand- GPO JACK FIELDS NIGH GRADE AC 240v BLOWERS and jack output C5.50 inc VAT á postage. large range of tappings for adjusting As new perfect condition 7 contact £6.50 L.T. TRANSFORMERS. ex computer equipment In good condition inputs and outputs. Inc VAT á postage housed in metal frame size ll "x7 "x7 "air Size approx 220mm x 280mm x32omm By famous makers fraction of list price all primaries outlet 4 "x3" motor spec 1300 rpm cont Weight approx 37kgs. Our price E95 inc. HIGH GRADE LT TRANSFORMERS 240 v price includes Postage 6 VAT. No 1.43v 3A rated £5.95 postage £3.00 VAT Ring For Carriage Details ALL PRIMARIES 240v E.H.T. TRANSFORMERS 66.9e No 2. 40v 3A £699. No 3. 21v 3A and 40 v OPEN FRAME TOP PANEL CONNECTIONS High -grade E.H.T. Tranny, PRI 240V, sec. ^ /A £6.99. No 4. 27.5- 0 -27.5v 1.2A and 7 -0 -7 MEMOREX V.D.U.s 1377 í0,000V, 18 750m /A í1.a6. No 5. 17.5v/A ¡times 16.50. No 6. 1 M /A. Probablyyused for boiler '27v1A We do full No tappedpped 2- 3- 4- 5- 6- 7- 8- 9- 10- 11- 12 -13 -14 22v1A 1001 A 1001 A 06.96. No 7. 60v1.5A notasyethave information on BATTERIES tion but with 101 other uses!!! We d very attractive units which fee- RECHARGEABLE 15v 8A E10. No 2 12v BA E7.50. No 3 tapped [4.96. No 8. 10- 7- 0 -7 -t0v 500m /A 29- 21- 0-21 -29v We have on offer these fantastic long life ES inc. carr. 370m/Á 51.96. No 9. 28- 27- 0 -27 -28 3503 /A C4. %. tures a 12' monitor mounted in an 13-12 -10 -8v 812A E9. No 4 Sec 6.3v 2A 6.3v 2A &VAT. batteries which have a large variety of uses. No 10. 2402A 04.50. No 11. 14v3A [4.50. No 12. adjustable cradle, and a full Alpha and 32 -0 m/a 5 unspillable using a special jelly and -32v 280 £4.75. No Sec 37v PARMEKO OP TRANSFORMERS 8.3vÚ8. 3v2Á32 -0- 32280m/Á [1.60. Nd 13. 13v2Á Numeric Keyboard. But response lo y r p electrolyte. 1.5A, 150 2A, 9v 50 £3.95. No 6 Sec Pri 6000 or 80000 or CT Sec 3.75 or 150 Ser/ 1501 A [4.e6. No 14. 27.501n/Á £1.60. No 154.5- them has been such that we feel you NO Type 1 D it 12v 5.7ÁH. Size 3%,x6x2'/," 2A ß.a5. No 7 Sec 27.5- 0 -27.5v 1.2A and 7-0-7 -0- 0-4.5v 200m /A 2.2 v 8003 /A C2.25. 16. 13- should be told Comes Par for £3.752 12.5W E4.50. Pri 5000 for g about them. with Price C9.5 inc VAT 8 carr. 13x1 A 12v 5003 /A [196. No 17 65v 2.2A 30 -0- diagrams for monitor offered to you 7v 750 m/a ß.5O. All prices include postage 3W Sec ß.7s or 150 SBr /Par E2.50. Pri at Type 2 Yuasa 1202ÁH. Size 5x6' /,x63/1. 30-45- 30v 100m/A 10v 3003 /A E4.96.No18. 55Ns0orn /A inc VAT. 17.00. Ring and VAT. £85.00 Carriage f Price 60 -90 to 1 also 90T01 for push /pull Sec 175!3 £3.96. No 19. 24.30.320 2A C/.96 for details. C24 inc VAT 8 Carr. PARMEKO LT TRANSFORMERS E2/. All prices include postage and VAT. NEW TRANSFORMER Open frame type top panel connections. BARGAINS PAPER BLOCK CAPACITORS prices postage Wp G CAPMCOITORS STOP PRESS 8MFD 2500V WKG DC £6.50 Ac wh have in stock a very limited number of By famous makers No 112. 118 -320 2A 0C rlatingi9 and 12 -18 -32V MFD 9 kg Paca We 1OMFO350V WKG DC £15.00 t Epson portable computers BRAND NEW No. 1. Pri 115 -230V Sec 21V 3A + 2.3IDC) E9. No 2 12-18-32V to (DC) and 12- 0.25 14400 £1.50 460. E1.75 P 8 MFD 4000 WKG DC £2.50 0.75 never been used offered fantastic low 40V 300 M/A E5 25 18 -32 V4Á E5. Na 3 12 -18 -320 12A (DC) and 12- 4400 EIaO 4400 4 MFD 10000 WKG DC £2.00 prices. Please ring for details!! 1 400v No. 2. Pri 220-240V Sec 17.5V 1A 3 18 -32V 100 m/a ß.95. No 4 12 -18 -32V 1/4A E1.56 6000 72.00 1 MFD 1000V WKG DC £1.25 times ES 75 (DC) and 12 -18 -32V 1/4A (DC) and 12- 18-32V 50 25 36M £1.50 300v £2.0 0 All prices inc. VAT and No. 3. Pri 220.2400 Sec 29-28-27-0. carriage m/a (DC) E2.50. No 5 32V 100 m/a (DC) and 27 700v E1.75 4 250v £1.50 27- 28-29V 0.3A £4.00 32V 25 m/a DC E2.50. All prices include po tage and VAT PARMEKO HT TRANSFORMERS FANS ALL PRIMARIES 220 -240V No. 4. Pri 220-240V Sec 6.3V 5ACT MUFFIN 412" 110V £4.00 L.T. TRANSFORMERS ELECTROLYTIC 'CAPACITORS POTTED TYPES 6.3V 2ACT £5.00 WOODS 6" Parmeko Atlantic Series poned type. Pri and 8" 240V £9.50 All prices include VAT 8 post high ripple type. No. 5. Pri 220 -240V Sec 40V 3A Tangential 220 -240v. Sec tapped 2-6v 1.6A and 14 -420 g Blowers 240V approxpprox No No 4 1.6A. The following voltages can be obtained 2 -4- 20,000mfd 40v dc wkg £3.50 3 Sec 400- £6.25 3 "x15" vent. Very powerful. £11. 6- 8- 12- 14- 28- 36- 40- 42- 44 -48v 6 í.6A 7100 mfd 40V dc wkg E2.50 0-400V 150 m/a and 150.0.1500 20 m/a £6.50 All prices inc. VAT and carriage All prices inc. VAT and carriage conservatively rated C7.50 inc VAT 8 Carr. 4700 mfd 40V dc wkg £2.50 inc postage and VAT. No 5 Sec 350-325- 0-325- Repanco. Pri 240V. Sec 25.3v 3A 10.5v 2A 4500 mid 64v dc wkg £2.50 350V 120 m/a £6.50 inc postage and VAT. Gre- 10.5.0.16A 6500 mid 80v dc wkg £2.50 open frame type C6.75 inc VAT 8 sham Pri 220-240V, Sec 250V 80 m/a 6.3V 4.5A AUTO STEPDOWN TRANSFORMERS postage FOR AMERICAN EQUIPMENT PARMEKO HT 15V 1.2A £5.95 inc postage and VAT. Pri 230- 250V, Sec tapped 190 -210V 24 m/a 6V 1A GARDENERS 'C' CORE SH 6.95 10H 75m /a ßs0 240/110 Volts. 80-2250 watts. Regular stock line. Types 80 -1500 wens are fully postage and VAT. Pri TRANSFORMERS 5H 250m/a Q50 IOH 753/e ß'95 inc 220 -2400 Sec shrouded. Fined with American two or three pin socket outlets and 3 core 240V U. PRI +10V, OV, 200V, 220V, 240V, (screen) 300V 200 m/a 30V 100 m/a 6.3V 5A half mains lead. Types 1750 and 2250 watts are steel cased with two American socket £5.75 15H 60 72.50 Main outputs s eí2 windings and 3V 56 ß,5O shrouded, dub chassis mounting £3.60 Inc outlets. Neon indicator, three lead SAE 25040e ß.a5 00H 120m/e core mains and carrying handle. Send for tapped at 1 V will givegi 260, 280, 290, 30V, 33V postage end VAT. Pri 220.2400 Sec 376490- price 2.5H 2503 /a Q50 SOH IOMa 12.50 list and further details. American sockets, plugs,9 adaptorsp also available. at 15amps. Size 150X133X170 4100 6 m/a £2.75 inc postage and VAT.`1NW -18 Price 716.00 inc. VAT &Carriage. 20H 120m /a £4.75 25H 60m/e Q75 All pnces include postage and VAT CIRCLE 68 FOR FURTHER DETAILS. ELECTRONICS & WIRELESS WORLD JUNE 1985 13

www.americanradiohistory.com B. BAMBER ELECTRONICS Tektronix Storage Oscilloscope Type 5646 £280 Marconi Delay Generator Type TF 1415... £50 Tektronix Storage Oscilloscope Type 564 £250 Marconi White Noise Test Set Type OA 20908 £220 RADIOTELEPHONE EQUIPMENT Tektronix Oscilloscope Type 556 c/w 1A1 Plug -ins £250 Marconi Carrier Deviation Meter Type TF 791D £120 Pye Base Station Type F30 AM High Band 8 Low Band 0220 Tektronix Oscilloscope Type 567 c/w 3576 6 3T77 Plug -ins . C450 Hewlett Packard SHF Signal Generator 7 -11gHz Type 620A .. £220 Pye Base Station Type F401 AM High Band £350 Tektronix Oscilloscope Type 661 0/w 4S3 Plug -In ... £180 Hewlett Packard Power Supply 0 -40v e1 30amp. Type 62688 £330 Pye Base Station Type F4001 AM High Band £550 Tektronix Oscilloscope Type 585 c/w Type 86 Plug -in.. £120 Hewlett Packard Power Supply 5 volt 4e B amp. Type 62005E £30 Pye Reporter Type MF6 AM High Band 8 Low Band £90 Tektronix Oscilloscope Type 453 50m Hz £375 Hewlett Packard Power Supply 5 volt A 60 amp. Type 62605L...... £85 Pye Europa Type MF5FM High Band £90 Tektronix Oscilloscope Type 454 150mHz C675 Rohde 8 Schwarz Standard Signal Generator 4 -300 mHz Type BN 41409.£150 Pye Olympic Type M201 AM High Band £65 Tektronix Oscilloscope Type 515A £100 Rohde 8 Schhwarz Decade Signal Generator 0.3- 500mHz Type BN41104. C850 Pye Motofone Type MFSAM High Band 8 Low Band £45 Dynamo Oscilloscope Type 07100 £290 Rohde 8 Schwarz Power Signal Generator 0.1- 30mHz. Type BN41001 £120 Pye Westminster Type W15AM High Band 8 Low Band £50 Telequipment Oscilloscope Type S51 £75 Avo Meters Model 7 £40 Avo Meters Model 8. C80 Pye M294 FM High Band C200 Telequipment Oscilloscope Type 554 £150 General Radio VHF Oscillator Type 1363 56- 500Mhz £50 Pye Base Station Type F9U UHF £90 Telequipment Oscilloscope Type S34 .. C85 Wayne Kerr AF. Signal Generator 10 Hz -120 Khz... £40 Pye Base Station Type F9AM High Band C90 Solartron Oscilloscope Type CT436 .. £85 General Radio Audio Oscillator Type 131IA 50 Hz -10Khz . £50 PLC Base Station Type F17FM High Band £250 Cossor Oscilloscope Type CDU 110 C150 Airmec Oscillator Type 858 30Khz -30Mhz E65 Pye Base Station Type F412 UHF E200 Tek. 500 Series Plug -ins. D-C20. E -C15, G -C20. H -C20, W -C20, Z-C20. K- EH Pulse Generator Model 139LB C45 ITT Base Station Type 30LRU43A UHF £150 £15, L-C15. 0 -C20. 1A4 -0100, 1A7- C50. 101 -050, Type 80 -C15. Solartron Pulse Generator Model GO 1101 £25 Pye Pocketfone Type PF2FM High Band 6 Low Band £80 Tektronix Time Mark Generator Type 180A £90 Armee Oscillator Type 304A 50 Khz- 100Mhz... CBS Pye Pocketfone Type PF2AM High Band 8 Low Band £80 Tektronix Square Wave Generator Type 107. £40 Airmec Modulation Meter Type 409 £90 Pye Pocketlone Type PF2UB UHF £80 Tektronix Pretrigger Pulse Generator Type 111 040 Airmec Modulation Meter Type 210A £40 Pye Pocketlone Type PF5 UHF £40 Tektronix Trigger Countdown Unit Type 280... 020 Ad -Vu Precision Phase Meter Type 405H £85 Pye Pocketlone Type PF8 UHF [80 Tektronix Low Level Preamplifier Type 122. . £20 Bruel 8 Kjoer Microphone Amplifier Type 2604... £50 Pye Pocketfone Type PF9 UHF .. 080 Marconi AM /FM Signal Generator Type TF 995A/5 £120 Dawe Phase Meter Type 632A £40 Pye Mains Power Unit Type AC15 C25 Marconi AM /FM Signal Generator Type TF 9958/5 0240 Dawe Vibration Meter Type 1433A E55 Pye Mains Power Unit Type AC200.. £120 Marconi AM /FM Signal Generator Type TF 1064 C60 Ferrograph Series 7 Mono Tape Recorders .. £100 Pye Power Amp. Type A200 High Band £50 Marconi AM /FM Signal Generator Type TI 2008. C875 Avo Valve Characteristic Meter Type VCM 163 with data £250 Pye Controllers Type PC1 £85 Marconi AM Signal Generator Type 801D 10mHz- 485mHz £90 60 amp. Alternator 8 Generator Noise Filters Lt Pye Controllers Type M81 ...... £195 Marconi Standard Signal Generator Type TF 144H/45 £90 Tektronix Oscilloscope Probes £10 Pye Westminster Type W30 AM High Band 8 Low Band £25 Marconi UHF Signal Generator Type TF 1060/2 t90 Mullard Van -cap Tuners Type ELC2003 Ex Brand New Equip £3.50 Pye Westminster Type LW15 FM High Band £40 Marconi FM Signal Generator Type TF 10668/1 10- 470mhz 0300 Pye Cambridge/Vanguard 18 Way Control Leads £4 Pye Base Station Type F3OFM Mid Band £200 Marconi RC Oscillator 20Hz- 200kHz Type TF 1101 . L65 BNC Plugs 75 ohm 50p Pye Europa Type MF5FM Mid Band £60 Marconi Valve Voltmeter Type TF 1041B £40 Circulators 590 -720 Mhz 'N' sockets. L25 PLEASE NOTE all sets are sold less crystals, mikes, speakers. power leads Marconi Power Meter Type TF 893A C50 Transistors Type 263055 Brand New . 4 for CI etc unless otherwise stated. Marconi RF Attenuator Type TF 1073A £25 Transformers 30 volt 49 1 amp 0/ CARRIAGE on FIT equipment Mobiles C2.00 each. Base Stations £15.00 - Marconi RF Power Meter Type TF 1020A. E65 Transformers 36 volt re 1.5 amp ... L7 each. Red Star available at cost. Marconi Universal Bridge Type TF 1313 £220 10.7 Mhz SSB Xtal Filters (2.4 Khz Bandwidth) Low imp. type. Carrier and Marconi Universal Bridge Type TF B68B £90 unwanted sideband resection min -40db (needs 10.69535 8 10.70165 xtals Size approx 2m z 1 in .tin £10 Marconi Universal Bridge Type TF 868A £60 for USB /LSB no supplied) WANTED LOGIC ANALYSERS DIODES Electronic Surplus. we also welcome the opportunity to quote for complete Fluke Model 3010A Programmable PCB Logic Tester £1.500 165406 8 165407 10p each. 100 of C5, 1000 of £30 factory clearance, Fluke Model 3020A Programmable PC8 Logic Tester £2.500 V.A.T. at BREAKING TEK 545A SCOPES P. & P. or Carriage and PYE POCKETFONE PF1 RADIOSONDE RS21 15% on total must be added to all FOR SPARES RECEIVER METEOROLOGICAL BALLOON orders. UHF very welcome, strictly be- 440 -470 MHz, Single Channel, int. CRT type T543 P2 C18 each. Mains TRANSMITTER Callers 1 p.m and 2 and speaker and aerial. Supplied complete Transformers T601 £15. with Water Activated Battery, contains tween 9 a.m. and with rechargeable battery and service High Voltage Transformer T801 with valves all- weather sensors, fully solid state, £5 5 p.m. Monday to Friday inc. manual, £6 each plus £1 p.p. plus V.A.T. £25. Also Switches, Knobs, Fans, each plus £1 p.p. plus V.A.T. Barclaycard and Access taken Metalwork. Capacitors and Official orders welcome ww2T BARCLAYCARD 5 STATION ROAD, LITTLEPORT, CAIVBS CB6 10E itill PHONE: ELY (0353) 860185 CIRCLE 49 FOR FURTHER DETAILS.

It's easy to complain about an advertisement. Once you know how.

One of the ways we keep a check on the advertising that appears in the press, on posters and in the cinema is by responding to consumers' complaints. Any complaint sent to us is considered carefully and, if there's a case to answer, a full investigation is made. If you think you've got good reason to complain about an advertisement, send off for a copy of our free leaflet. It will tell you all you need to know to help us process your complaint as quickly as possible. The Advertising Standards Authority. If an advertisement is wrong,were here to put it

ASA Ltd, Dept 1 Brook House,Tornngton Place, London WC1E 7HN

This space is donated in the interests of high standards of advertising. & WORLD JUNE 1985 14 ELECTRONICS WIRELESS

www.americanradiohistory.com Introducing... I I Ghz SATELLITE TV RECEPTION.

THE FOLLOWING TV TRANSPONDERS ARE AVAILABLE NOW FROM ECS /INTELSAT:- Premiere (UK film channel). Screen Sport (UK Sports channel) TEN (UK film channel). Childrens Channel (UK). RAI (Italy). Teleclub (Switzerland). Olympus (Pan European TV) Film Net (Belgium, mainly American films). WPN (World Public News). PKS (Germany). TV5 (France). New World Channel (Norway - religious, multi language). SKY. Music Box (Stereo pop video channel). Norway (C -Mac system). Additional channels late 85 - Cable News Network, Life Style channel, plus all TV transponders on ECS 3 due for August launch. A typical system consists of our I.6m dish in either fixed, AZ /EL or Polar mount. Scalar horn & feed in Aluminium, brass or phosphor bronze. Low noise block downconverter (2.2 - 3.0 dB noise figures) converting the 10.9 - I I.7Ghz signal to 950 -1750Mhz IF feed to the indoor unit. Demodulator, gives audio & video output to feed a colour monitor or a VCR.

Package price for a complete system from £ I 550 plus VAT & carr. Through our joint venture Company "Tele Aerials" of Harrogate, we can offer an installation service from a single point to a Major Hotel System, Housing Complex etc. The Company has supplied systems to:- Foreign Embassies, British Government, Overseas Hotels, Universities, Research Organisations, TV retail Trade and the Public. Serpent SCARA assembly robot TO DISCUSS YOUR REQUIREMENT, i4 t, CONTACT: - D.J. STANDEN. '=ri ' On show at Automan NEC 14 -17th May ':._.?4,1!' .,' -': ' and at Training & Development NEC 9-11th July East Sate

AND To be featured as a Manufacturers of Microwave Dishes, Feed Horns and Specialised Electronics Suppliers of Satellite Systems and Closed Circuit T.V. Equipment Çybernu t c constructional project in .,s ppllcations Practical Electronics CROPTON, PICKERING, NORTH YORKSHIRE Y018 8HL 0264 50093 September issue. TEL: LASTINGHAM (07515) 598 VAT No. 347 557132

CIRCLE 38 FOR FURTHER DETAILS. CIRCLE 74 FOR FURTHER DETAILS.

We are Cash Purchasers of large and small parcels of

Surplus I /C, Transistors, Capacitors, Connectors and related electronic stock. We also welcome the opportunity to quote for For Education, complete Factory Clearance incl. Production Machines & Tools. Training and Industry

We would appreciate a telephone call or a list available. r

We pay top prices and collect. NEPTUNE I Enquiries also welcomed from Europe. NEPTUNE II' NEPTUNE - for clean hydraulic power - LANCO LTD. - tap water Is the 10 LABURNUM HOUSE fluidi LORDSHIP TERRACE, LONDON N16 OJB TELEPHONE: 01 -249 5373

Lynwood GD1 VDUs: Intelligent Green micro controlled, RS232, printer port, 101 key k/b. Full Video enhancements. ONLY £149+ £15 P &P (S /H) Burroughs MT686/7/TD710: Intelligent Green 12" VDU with 3 micros and 64K store. RS232. Programmable... Only £199 new or £149 S/H + £15 P &P Open Chassis Video Monitors from above VDUs £40+7.00130 Multirail Switching PSUs from above 5v 4A 12v +24v NEPTUNE 16 erses, B Nt control system. 1 SKy Robots may also be taught by lead by the £25 +£1.50 r apactry. 1120mm react, nose method Data 6012 VDU's very attractive display working RS232 Extensive is General NEPTUNE ll , axes I2 HI comsat system. software supplied free with each robot. with integral 73 key k/b either dumb terminal mode or page 2 5Kg capacity I r e tch buffered Only £120.00 + El 5.00 p&p Leads available for connection to BBC. IX MENTOR DC servo desktop roba, H bu Centronics 306 Line printers: Professional fast (120 cps), Spectrum. Apple Ile. Commodore 64 and antral system 300gm capaury 420mrn reach VIC 20 superb quality 80 column printer. Parallel i/f ONLY £99+ £ 15.00 P &P Most other micros are also easily usable with floppy f ram Osborne Executive Portable CP /M system with oodles of software. Twin Rnbnit programmed keyboard ar hand these robots held SimoialUl ¡model rnrr riI drives £900 +£15 p &p Robots also available ready built Diablo 630 Daisywheel printer. OEM i/f NEW £599 +£15P&P o Calcomp 565 Drum Plotter, l Othou steps. ONLY £450 + £ 10 P &P . Please phone for brochure: 0264 50093. () West Portway Industrial Estate, Andover SP1 O 3 WW. BECKENHAM PERIPHERALS LTD _! ybernetie A private and independent company giving prompt, We also buy Callers welcome ppllcations personal service by appointment 01 -468 5582 redundant peripherals 34 Rodwsy Road, Bromley Kent BR1 3J1 CIRCLE 61 FOR FURTHER DETAILS. CIRCLE 30 FOR FURTHER DETAILS. ELECTRONICS & WIRELESS WORLD JUNE 1985 15

www.americanradiohistory.com TURN YOUR BBC MICRO INTO A PROFESSIONAL MICROPROCESSOR DEVELOPMENT SYSTEM THE OPERATING SYSTEM FLEX -The Professional Operating System Versatile, Flexible & Powerful, the ideal operating system for industrial control Provides the power, sophistication and ease of development, previously only offered by larger, more expensive systems

THE HARDWARE 6809 Advanced 16 Bit Processor Choice of Industrial Interfaces for Target Applications: - High Resolution Colour Graphics - Industrial input/output boards - IEEE communications - and many more THE TOOLS PL9 -A fast, efficient control language CMS FORTH Interpreter & Compiler Cross Assemblers for most 8 bit & 16 bit micro's "C", BCPL, PASCAL Cambridge THE SUPPORT 44a Hobson Street Cambridge CBI. 1 NL Microprocessor Top rate after sales technical support JUl (0223) 324141 Systems Limited Systems / Hardware Design

CIRCLE 66 FOR FURTHER DETAILS.

EXTRACTOR FANS - MAINS OPERATED Toroidal Woods extractor. 5" - £5.75, Post £1.25. 6" - £6.95, Post £1.25. Transformers 5' Plannair extractor as manufacturers we are able to £6.50. Post £1.25. offer a range of quality Toroidal 4" X 4' Muffin 115v. Transformers at highly competitive £4.50. 230v. £5.75. Post 75p. prices and fast delivery. All the above ex- computer, those below are unused. Mail Order Price List 4" x 4" £8.50. Post 75p. 15VA 6.92 30VA 7.18. 50VA 8.86. 80VA 9.92. 120VA 10.59. 160VA 12.10. 225VA 13.69 9" American made £11.50. Post 300VA 14.77. 500VA 19.20. 625VA 22.09. 750VA 26.17.1 KVA 38.82. 1.2KVA 44.06 price includes p +p & vat. £2.00. 6- 0- 6,9 -0- 9,12 -0- 12,15 -0 -15. Tangential Blower 10 X 3 air Available from stock in the following voltages :- 30-0-30,35-0-35,40-0-40,45-0-45,50-0- outlet, dual speed £4.60. 18-0-18,22-0-22. 25-0-25, volt. Post £1.50. 50,110,220,240(max.10 amp). Primary 240 Quantity Prices and delivery on request MICRO SWITCHES V3 type all 250V 10 amp SpST 15p (we also manufacture conventional El type transformers) 1000 - £100 Spdt 20p 1000 - £150, very low torque Spdt 30p 1000 for £200 AIR Airlink Transformers. Unit 6, The Maltings, Station Road, LINK Sawbridgeworth, Herts. Tel: 0279 -724425. ROCKER SWITCHES Standard size fit 11.5 x 28 mm cut out. Single pole on /off - 10p each 1000 for £75. Single pole changeover 20p l I RCLE 59 FOR FURTHER DETAILS. each - 1000 for £100. Single pole changeover with centre off - 25p each - 1000 for £125. Single pole on /off with neon - 36p - 1000 for £180. MINIATURE WAFER SWITCHES ELECTRONICS C.A.D. 2 pole, 2 way -4 pole, 2 way -3 pole, 3 way - 4 pole, 3 way -2 pole, 4 way -3 pole, 4 way - "ANALYSER" 2 pole, 6 way - 1 pole, 12 way. All at 25p each or 100 for £20. PERFORMANCE ANALYSIS of UNEAR CIRCUITS using the BBC MODEL B AND SINCLAIR SPECTRUM 48K MICROS. Simulates Resistors, Capacitors, Inductors, Transformers, Bipolar and Reid effect Transistors,and 12 volt MOTOR BY SMITHS Operational Amplifiers in arydrwlt configuration. Made for use in cars, etc. these are very Performs FREQUENCY RESPONSE ANALYSIS on Circuits with up to. 30 Nodes powerful and easily reversible. Size 372" 100 Components, for Phase and Gain /Loss, Input Impedance andnd Output long by 3' dia. They have a good length of Impedance. /, spindle - Ideal br the analysis of ACTIVE and 0°SSNE ALTERS, AUDIO, WIDEBAND and R.F. Price £3.45 or 100 for £250. AMPLIFIERS, UÑEAR INTEGRATED CIRCUITS etc, etc ANALYSER" can greatly reduce or even eliminate the need to breadboard new designs. USED BY INDUSTRt ,LAND UNIVERSITY R &D DEPARTMENTS WORLD WIDE. N.B. ELECTRONIC SUPPLIES VERY EASY TO USE. PRICES FROM £20 ACCESS OR AMERICAN EXPRESS WELCOME... 34 America Lane, Haywards Heath, Sussex R1116 3QU For further details write or phone NUMBER ONE SYSTEMS Phone 0444 454563 for Access or B.C. DEPARTMENT VAX/ 9A CROWN STREET, ST IVES Please add £1 if order under £20 HUNTINGDON CAMBS. UK. PE 17 4EB TEL 0480 61778 TELEX: 32339

CIRCLE 79 FOR FURTHER DETAILS. CIRCLE 60 FOR FURTHER DETAILS. & WIRELESS WORLD JUNE 1985 111 ELECTRONICS

www.americanradiohistory.com Fast camera by Safa S. Omran interface Signals from standard video cameras are too fast to feed directly into a microcomputer. A solution is to take one picture element from each line in successive frames until a picture is built up. This design is faster, taking eight elements at each pass.

Video cameras scan a picture in Howard in the February 1982 pixel. An entire picture with a a sequential series of horizontal issue of WW on pages 30- 36. horizontal resolution of 256 lines. This scanning makes it The major problem with this pixels is stored in 5.12s. possible for one video signal to type of interface is the high Our method is to make the include all the elements for an speed of the camera relative to microprocessor store eight entire picture. Television the microprocessor. pixels from each scan line at frames conforming to the CCIR Howard's method involves each pass which redces the time standard consist of two fields, storing one picture element, or for storing a picture by a factor each of 312.5 lines. A line is pixel, from each scan line in the of eight. The time needed to 641.ts long and picture field then storing the next store a picture with a horizontal information is transmitted for picture element from each line resolution of 256 pixels is thus about 40µs of this time. of the next field, and so on for 256 divided by eight, multiplied A method of interfacing a all the pixels across the picture. by 20ms, which is 0.64s. The video camera to a micro In this way, the microprocessor circuit designed uses this computer was described by P. has 64µs in which to store each resolution with an eight -bit Fig. 1. Block diagram for the Output port Input port video camera interface timing (30) (20) circuit. By taking eight pixels 1 from each line in successive frames, the interface allows Monostable a 256 -pixel by 256 -line C. 74121 picture to be stored in 0.64s. Width 7408 -. circuit Reset Reset

Pixel Clock Oscillator counter Field gate

Line sync. Video Sync. signal seperation Digital circuit comparator

oad Load Field sync. 3 bit

Clock Field Clock Decoder 5 bi counter Binary counter counter Clock

Reset a b c Digital video signal 710

Vref I 1 DO Input 0 3 -to -8 á0 8 latches CKO port 1 8 bit LS74 8 bit decoder 07 CK 1281 7 LS138 (4 off) nal

Safa Omran is with the Institute of Technology in Baghdad. ELECTRONICS & WIRELESS WORLD JUNE 1985 17

www.americanradiohistory.com compared with output from the field and binary counters by a Addr. Content Label Instruction Comment digital comparator which H,4000 Set HL register to start of picture store 6000 21 00 40 L):I generates a pulse when its two 6003 3E 00 STRT: MVI A,00 6005 77 MOV M,A Clear memory location inputs are equal, Fig. 3. 6006 23 INX H Go to next location Assume that output from the 6007 76 MOV A,H field counter is one, i.e. 00001. of picture store? 6008 FE 60 CPI 60 End When output from the pixel 600A C2 03 60 JNZ STRT Go back if not 600D 21 00 40 LXI H,4000 Set HL to start again counter is zero, the binary 6010 11 20 00 LXI D,0020 counter output is also zero so 6013 OE 00 MVI C,00 Reg.0 contents=no. of lines the two digital comparator 6015 3E 02 MVI A,02 inputs are unequal, being zero 6017 D3 30 OUT 30 Initialize video camera interface 6019 3E 03 MVI A,03 and eight. 601B D3 30 OUT 30 When output of the pixel 601D 3E 01 MVI A,01 Open field gate counter increments by one, the 601F D3 30 OUT 30 binary counter output also 6021 DB 20 FLD: IN 20 Wait for field pulse 6023 E6 01 ANI 01 increments by one, but the two 6025 FE 00 CPI 00 inputs to the comparator are 6027 C2 21 60 JNZ FLD still not equal. They remain Wait for strobe pulse 602A DB 20 PLSE: IN 20 unequal until the output of the 602C FE 02 CPI 02 602E DA 2A 60 JC PLSE pixel counter becomes eight, in 6031 DB 28 IN 28 Put data in A reg. which case output of the binary 6033 77 MOV M,A Store it in memory counter is zero. Now the two to next video line 6034 19 DAD D Go inputs to the digital comparator 6035 OC INR C 6036 79 MOV A,C End of 256 lines? are equal (00001000) so it 6037 FE 00 CPI 00 generates a pulse. next line 6039 C2 2A 60 JNZ PLSE If not, go back to store data from In the next count, outputs of 603C 26 40 MVI H,40 the pixel counter and field/ 603E 2C INR L Increment content of Reg L 603F 7D MOV A,L End of 256 pixels? (32 x 8) binary counters are also equal 6040 FE 20 CPI 20 (00001001) so another 6042 C2 21 60 JNZ FLD Go back if not comparator pulse is generated. HLT Stop 6045 76 END: This is so for each count until output of the pixel counter becomes 16 (00010000), so Assembly language program word 8085A microprocessor. field pulses only. Width of the eight pulses will be generated for reading the camera field sync. pulses is about 2ms, from the digital comparator in this scan line, Fig. 4. interface using the 8085 Circuit description while that of line pulses is about microprocessor. 21.i.s. From the RC circuit, the After 64µs, another eight As shown in the block diagram, signal feeds a comparator with a pulses will be generated for the Fig. 1, the video signal feeds positive reference of 2V, which next scan line, and the process the synchronization separator gives only field pulses. will be repeated for all the scan which separates the line and Line -sync. pulses are passed lines of the field. This means field sync. pulses. to a circuit which increases that the comparator generates The video signal is +0.5V their width. This is required eight pulses corresponding to peak combined with because data only exists for eight pixels (pixels 8 -15) of synchronizing pulses of +0.2V. about 401is of the scan line. A each scan line. To separate sync. pulses, the voltage -controlled oscillator, In the next field, output of video signal is first passed to a v.c.o., determines the number the field counter is two (00010) comparator with a reference of of picture elements wanted on a and the comparator inputs are 0.1V, Fig. 2, which gives only line. Output from the width equal when the output of the sync. pulses at its output. This circuit enables the v.c.o. and pixel counter is 16. In this case, output is passed to an RC only allows it to oscillate for output of the binary counter is circuit with a time constant of 40µs. zero. These inputs remain equal about 50µs which integrates Output of the pixel counter is until the output of the pixel counter becomes 24 (00011000) which means that the digital comparator generates another eight pulses corresponding to the next eight pixels for each scan line. This process is then repeated so that eight pulses are generated by the comparator in each field. These eight pulses enter the Fig. 2. Sync. separator decoder counter, the output of circuit. The first 710 which varies from 000, to 1112 comparator takes composite as shown in Fig. 4. This output line /field pulses from the is the input of the decoder, one video signal and the second output of which is active for one produces field pulses each state of the decoder only with the aid of an RC counter. The eight latches put integrator at its input. eight consecutive pixels from & WIRELESS WORLD JUNE 1985 18 ELECTRONICS

www.americanradiohistory.com 5V 330p 56k 14 11 1110 16 11 4 14 To input 4 9 port 120) 74121 13 14 1/2 741_500 74LS193 12 74LS193 5 74LS193 47_13 7 2 OV

7 6 2 3

116 I6 15 15 15 13 12 10 15 13 12 10 t 1¢a 16 3 68k 471311 1 3 4 11 15 1 2 111 110 tOk 74LS138 2 2 74LS193 5 3 6 741585 74LS85 16 10 3 Ea i 74LS123 9 10k 1k 7

11 9 7 9

47T 2 3 t ti68k 13 16 4 330p 100k 11 1 10 6 74LS193 74LS 193 74L5193 16 14 5 74121

tl 14

v -41-OV

. From output Field sync. Line sync. port 130

the video signal on to the input e. repeats steps (a) to (d) 32 Fig. 3. Timing circuit for the video- camera interface. Data port of the microprocessor, times, equal to the number latches, video driver and i/o gating are hence the microprocessor of pixels in a line, i.e. shown in the block diagram. stores eight pixels at a time 32X8-256 from each scan line. f. ends Software For step (b), a monostable i.c. Movement of data from the stretches the strobe pulse to camera to the microprocessor is about 16µs to make it suitable controlled by software which for the microprocessor. An stores 256 pixels per line for assembly -language program is 256 lines in the field. shown for the 8085 At the start, the field and microprocessor assuming 256 decoder counters are loaded pixels by 256 lines. In this with their maximum counts by a program, memory location pulse from the microprocessor. 4000i6 is the start of the picture This ensures that the output of store and location 5FFF16 is the the field counter is zero after its end. Port 30 is used for output Fig. 4. Output of the digital comparator, top, consists of first count and that output of and ports 20 and 28 are used eight pulses which step the decoder counter. On each the decoder is zero to ensure for input, see block diagram. count, one pixel from the line is latched ready for reading that the microprocessor stores Figure 5 shows a circuit by the microprocessor. the first pixel. Next the diagram which was digitized microprocessor opens the field using the interface and Fig. 5. An example of a circuit diagram digitized using the gate and displayed on a storage video camera interface and displayed on a storage oscilloscope. oscilloscope. a. waits for the field sync. pulse

b. waits for a strobe pulse from the digital comparator

c. stores the eight pixels from its input port in less than 64µs d. repeats steps (b) and (c) 256 times, equal to the number of lines required ELECTRONICS & WIRELESS WORLD JUNE 1985 11

www.americanradiohistory.com BOOKS

The Hacker's Handbook by Hugo Learning Microsoft Basic for the they work and then hands over to Cornwall: Century Communications, Macintosh by David A. Lien: contributors from Intel (on the Uosat data decoder The 458 pages, 2920), NEC (on the 7720) and 149 pages, soft covers, £4.95. Compusoft Publishing, p.c.b. Book They Tried To Ban. soft covers, ISBN 0 932760 27 9. Texas Instruments (on the Fascinating guide to dial -up Chatty, persuasive introduction to TMS320) for the practical details. A new printed circuit board computer systems and the Basic on the Apple Macintosh, with is available for the high - psychology of people who devise numerous examples, exercises and performance G3RUH Uosat and use them. Gives few real cartoons. Single -chip Microcomputers data demodulator (Wireless secrets away, but could be worth edited by Paul F. Lister: Granada World, May 1983). having just for the technical Learning TRS -80 Model 4/4P Publishing, 231 pages, hard covers, The board includes the reference material. Rather Basic by David A. Lien: Compusoft ISBN 0 246 12106 8. An 1200 baud circuits, (limiter, expensive. Publishing, 483 pages, soft covers, introduction to some commercial ISBN 0 932760 19 8. Ditto for the chips with design examples: the phase -locked loop, integrate - new TRS -80 models. Just shows Motorola M6801 and M6805 (with a and -dump and lock An Introduction to Z80 what you can do with a word - speedometer /tachometer/ detector), regenerated and Machine Code by R.A. and J.W. processor! odometer); the Texas TMS1000 RS232C output interfaces. Penfold: Bernard Babani (with a speech synthesizer The input filter, 300 baud (Publishing), ref. BP152, 127 Micro Interfacing Circuits, book interface); the Zilog Z8 (with a data and c.c.d. line -sync pages, soft covers, £2.25. logger); the National Semiconductor 1 by R.A. Penfold: Bernard Babani detectors have been omitted. Beginner's guide for the home COPS400 (with a digital tv tuning (Publishing), ref. BP130, 96 pages, is computer user. Chapter 3, which The p.c.b. single sided soft covers, £2.25, ISBN 0 85934 system) and the Mostek MK68200 the instruction set, (with a and legended, measures describes 105 4. Practical guide for the machine controller). of the book. 160X100mm and has space takes up about half hobbyist. Chapters cover address modes are covered for an RS Components Addressing decoding, serial and parallel i/o in just four pages 12V RS rather sketchily chips, driving relays, de- bouncing Telecommunication Principles by encapsulated p.s.u., with no program examples. At the switches, d -to -a and a -to -d J.J. O'Reilly: van Nostrand 591 -281. A suitable case is are a few brief specimen end conversion. Reinhold, 143 pages, soft covers, RS 508 -605. Connections to listings for the ZX81, ZX £5.75, ISBN 0 442 30592 3 pbk. the p.c.b. are via a single Spectrum, Amstrad and for Electronics Engineers Tutorial guide for first and second - 16 -pin d.i.l. plug. Memotech micros. Pascal by J. Attikiouzel: van Nostrand year undergraduates covering Prices: p.c.b., Reinhold, 148 pages, soft covers, communications theory, modulation instructions and (air mail) £5.75, ISBN 0 442 30597 4 pbk. methods, radio receiver principles An Introduction to 6502 postage - UK £10, Europe Tutorial guide at first -year and digital communications. Three Machine Code by R.A. and J.W. £11, overseas £12. Note undergraduate level, with exercises case studies at the end describe Penfold: Bernard Babani that the Wireless World and worked examples. Makes techniques used in stereo f.m. (Publishing), ref. BP147, 107 a attractive use of marginal notes for broadcasting, U.K. colour tv and article is not included: pages, soft covers, £1.95. Much hints and asides. Three case studies videotext. reprint is available at an the same treatment as in the Z80 at the end illustrate the use of extra £1 (abroad £1.40). version above. Demonstration Pascal for writing circuit analysis Available now from the to the BBC listings at the end relate programs. Transmitted Picture Assessment author (for address see table /Electron, Oric, VIC -20 and Micro by John Allnatt: John Wiley and Commodore 64. 3) or from Amsat -UK, Practical Electronics Building Sons, 303 pages, hard covers, London, E12 5EQ. Blocks, book 2, by R.A. Penfold: £19.50, ISBN 0 471 90113 X. A practical guide to assessing tv Microprocessors: Hardware and Bernard Babani (Publishing), ref. BP118, 94 pages, soft covers, picture impairments in the Applications, by Andrew Veronis: laboratory and in the field. The Prentice -Hall International, 928 £1.95. Audio stages, filters and flip -flops for beginners. author is head of the Visual pages, hard covers, £51.45, ISBN 0 Performance Standards Section at Data Recording 8359 4382 8. Heavyweight guide to Answers on Radio British Telecom's Martlesham continued from page 64 a wide selection of 8 -bit and 16-bit Questions and laboratories. types. Chapters cover chip Repair by Les Lawry Johns: may need to be varied for differ- architecture, programming, Newnes Technical Books, 106 ent heads. It does not seem criti- memory systems, i /o, interrupts, d- pages, soft covers, £2.65, ISBN 0 The Motorola MC68000 of practical cal. to-a and a -to -d conversion, disc and 408 01509 8. Heaps Microprocessor Family by humour from an During reading, the write out- tape storage, single -chip advice and good Thomas Harman and Barbara microcomputers, arithmetic experienced practitioner. put is shorted to prevent noise Lawson: Prentice -Hall interfering with the read signal. processors and trouble - shooting International, 574 pages, hard The read signal is applied to A3, a with logic analyzers. Data sheets for Radio and Television Servicing, covers, £37.90, ISBN 0 13 603960 several of the chips are included 1983 -84 models edited by R.N. X. Heavyweight guide to Motorola's non - inverting amplifier with a among the ten appendices. Wainwright: Macdonald, 863 pages, 16- bitters. Chapters cover the gain of about 25. Because of the hard covers, £22.50, ISBN 0 356 instruction set, program control, head's inductive reactance, this 10259 9. Diagrams and servicing arithmetic operations, programming amplifier must have a high input An Introduction to Programming information for a variety of models techniques, system operation, i/o impedance to preserve the signal the Atari 600 /800XL by R.A. and by Alba, Binatone, Fidelity, handling and interfacing. Numerous at high frequencies. About G.E.C., Hitachi, Luxor, Mitsubishi, J.W. Penfold: Bernard Babani exercises. 400mV (peak -to -peak) is avail- (Publishing), ref. BP143, 108 National Panasonic, Network, able of A3. pages, soft covers, £2.25. All about Perdio, Philips, Pye, Roberts, Saba, at the output Atari Basic, with a few games Salora, Sharp, Sony, Tatung, Murphy's Law and other reasons Coupling between A3 and A4 is listings thrown in. Teleton, Thorn-EMI and Toshiba. why things go wrong, by Arthur via a small -value capacitor which The out- Bloch: Price /Stern /Sloan Inc. , Los differentiates the signal. Signal Processor Chips edited by Angeles, 94 pages, soft covers, put to the BBC Micro is a 1.4V An Introduction to Programming David J. Quarmby: Granada $2.95 ISBN 0 8431 0428 7. peak -to -peak square wave with the Sinclair QL by R.A. and J.W. Publishing, 179 pages, hard covers, Treasure chest of quips, axioms and very little jitter on the edges. Penfold: Bernard Babani ISBN 0 246 12171 8. Not ordinary aphorisms for engineers and others. This design has proved to be (Publishing), ref. BP150, 99 A es, analogue chips, but digital Also Murphy's Law Book Two, very reliable over the past year. soft covers, £1.95. Programnfingg programmable l.s.i. chips with 94 pages, $2.95 ISBN 0 8431 0674 The cost of the components is filters, 3. Sample rib -tickler: "A computer and interfacing with Superbasic. widespread applications in about £3 plus a cheap cassette have been modems, speech processing, sonar does what you tell it to do, not what Listings look as if they recorder (mine was £9.99 from printed by a bus -ticket machine - and video. The editor contributes you want it to do" (Greer's Third a pity. chapters on what they are and how. Law). Woolco). 20 ELECTRONICS & WIRELESS WORLD JUNE 1985

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www.americanradiohistory.com COMMUNICATIONS COMMENTARY

Costly Def time. So as soon as the problem possibility of "community radio" submarines at extremely low is detected, it is necessary to stations between 105 and data rates. At e.l.f. even a 30- establish very rapidly Do the Services and tax- payers which 107.9MHz, a part of the mile antenna is very short in equipments contain devices spectrum now expected obtain value for money in their to be terms of wavelength and from the suspect batches purchases of radio, electronic - cleared of present efficiencies are extremely low. impossible to full and related equipment for do without communications services by Signals can, however, be traceability... The advanced weapons and low cost of about 1990 rather than the received at great range and at many consumer items is gained 1995 communications system? In the date originally written into considerable depth on compact as the result of automated flow case of some projects, such as the 1979 WARC. frame antennas. line production; once you The conference, the first the painful long-running £5000 - part The American customs disturb this process to add million saga of British torpedo of which was held in 1982, service is planning to use six inspection and test stages, development, patently not. For the produced a formal "Geneva Orion long -range patrol aircraft production costs can increase all military equipment, price Agreement 1984" covering equipped with airborne (AN/ very rapidly indeed." tags tend to be very high Region 1 and part of Region 3. APG -63) radar capable of when These arguments seem judged by civilian equipment very To this is annexed a "Geneva detecting and tracking small convincing, that is until you standards. But are these not Plan 1984" covering frequency low -flying aircraft and surface start to wonder how much justified by the high standards all assignments for more than vessels. This is part of the these extra precautions have of reliability and environmental 53,000 sound broadcasting current American campaign to really added to reliability in the testing involved in the stations. The UK part of the reduce the large -scale field. When a few years ago I manufacture of equipment to plan foresees five national smuggling of drugs into the asked the technical director of a the defence and MIL -spec networks (four for BBC, one for USA, although this campaign firm supplying military standards demanded Independent National Radio), could be rendered ineffective by by the UK, communications equipment NATO and USA services? the BBC and IBA local radio the increasing manufacture of what had been the effect of the stations In general terms all most of which will be synthetic hard drugs within the DEF component specification he semiconductor devices and grouped into separate sub -sub- USA. Target information from replied that it had greatly components are required bands, plus the proposed new the patrol craft will be passed to to increased costs but work over the impressively had made tier of community radio. the US Coast Guard and other very little difference to large temperature range of -55 government agencies whose reliability. The Pentagon is to +125 °C. Semiconductors Radar up -date task it is to intercept and for currently complaining that it aerospace applications have to apprehend suspects. has to spend something The Fylingdale long-range be in hermetically sealed metal approaching a quarter of its radar, which forms part of the or ceramic packages. Batch annual budget on maintenance American ballistic missile early testing of samples, normal and repair of equipment. warning system (BMEWS) is practice for most electronic Horror Cordless tv stories abound of the American soon to be up- graded and equipment, is ruled out. To services paying $110 for electric modernized. A radically One of the most thankless, yet permit traceability, all stages of plugs available in hardware different solid -state phased vitally important, tasks of manufacture and assembly have stores for about 5c, $7622 antenna array, similar to one governments is to uphold, and to be documented and currently being installed at if possible improve, the monitored. rather than less than $100 for coffee makers fitted in cargo Thule, Greenland, is likely to regulation of the radio As one reader who is involved planes, $170 for battery- be installed. These have 2560 spectrum. While in recent years with making equipment to operated torches. In the UK it active elements in each 84 -ft in the UK public attention has defence specifications puts it: is more difficult to high antenna face, providing been focussed primarily on "The standard 'commercial' discover just how much is paid almost a megawatt of power. "pirate" broadcasters and device will rarely have received for what. - and with what results. Nobody Unlike the present mechanically before that on 27MHz c.b., the very much in the way of testing likes the idea of people steered antennas, the phased - general situation has been before despatch; normally being the sent into action array is fixed with electronic deteriorating alarmingly rapidly. procedure is one with poorly of lot sample made beam steering under the control Point -to -point services are testing with the entire batch equipment, but it has been pointed out that video of CDC865 computers. Such tending to occupy and hold accepted or rejected on the games in arcades arrays can simultaneously track channels not registered with the results of the sample testing. are expected to withstand rough treatment a number of targets. International Frequency MIL -spec devices, on the other without being made to - The Americans are also Registration Board; megawatt hand, will have been 100 per MIL spec standards! currently building a network of over -the -horizon radars, cent tested and burned -in for over- the -horizon h.f. radars including Russian pulsers and 168 hours at 125 °C.. . with an operational range of American continuous -wave Traceability also adds quite a about 5000 miles, almost twice radars, are taking over chunks cost Vhf changes penalty. It is necessary to that of the BMEWS of h.f. not allocated for radar in be able to check on a specific As a result of decisions made at installations. For the reception ITU Radio Regulations; out -of- semiconductor device, for the 1984 ITU Regional of o.t.h. signals, 4980ft long - band high -power h.f. instance, right back to the Administrative Conference for wire Beverage antennas are broadcasting is flourishing (the materials used and to the the planning of the v.h.f. used. DTI has described this as diffusion process. This facility is broadcast band between 87:5 Much longer antennas are "semi -regulated anarchy "); by essential when batch related and 108MHz, attended by 500 needed for transmission of no means all private mobile problems are discovered so that delegates from 77 countries, a extremely low frequency (e.l.f.) radio networks strictly adhere suspect batches can be isolated considerable number of communication signals at to their regulations; licensing very rapidly and appropriate frequency changes are due to frequencies below 100 hertz, authorities find it increasingly action taken... drop-offs do take effect before July 1987 to and a 30-mile antenna is difficult to cope with all the occur even in the best regulated UK local radio (BBC and ILR) reportedly to be erected in administration and paperwork; circles! The most worrying stations, including some later Scotland though it is not clear the Merriman Committee noted thing, from an equipment this year. Eventually all UK whether this will be an the increasing need for the UK manufacturer's point of view, is local stations will be in two sub - American or British operated Radio Regulatory Department that such problems often to not bands of 94.6 to 97.6MHz and system for broadcasting to devote "adequate resources" become evident for quite a long 102.0 to 104.9MHz with the messages to submerged to "spectrum monitoring, ELECTRONICS & WIRELESS WORLD JUNE 1985 23

www.americanradiohistory.com COMMUNICATIONS COMMENTARY

particularly of the mobile and lowest power Multiview unit amateurs, including those from the transmitters located in fixed bands, as an aid to with its built -in antenna, have overseas, will be able to operate Embassies or other diplomatic efficient spectrum one feature in common; the use the station provided that they buildings in the days when management ". of any would clearly contravene produce their licence certificate. British Intelligence operated On one of the few occasions the Wireless Telegraphy Acts under the transparent cover of when the Radio Regulatory and could be seized if used - Passport Control. A more regime has been the subject of yet is is perfectly legal, despite powerful transmitter, the Mark an adjournment debate in the last year's Act, for the company The Mark III X, had an 813 power amplifier of Commons (March 26, to make, advertise and sell and was sometimes used. House H.W. King's graphic account 1985) it started at 8.43 a.m. these transmitting units! When early in 1940 the first ( "S0E" in Feedback, April an all-night sitting and results of Bletchley Park's after 1965) of the travails of Veljke ended 17 minutes later at 9 cracking (with the aid of the Dragieevi6, as SOE's first radio when the motion duly Poles and French) of the a.m. operator in Yugoslavia, in lapsed "without Question put ". German Enigma machine Amateur having to hump around a 80- Barry Henderson, became available, Special 100lb "Mark III" transmitter MP for north- Liaison Units were set up to Conservativve Radio package, highlighted the been distribute what became known east Fife, who has problems of clandestine radio in as "an unobtrusive as "Ultra" to overseas described occupied countries in the period New Technology man with old commands, and the Mark III Jas -1 in 1986 1941 -42, though personally I values" attacked the efficiency became the mainstay of SLU An amateur radio satellite, JAS- doubt if his package included an of RRD, drew attention to its communications. During late 1, currently being built and HRO receiver in what became draconian powers and provided 1944, there were no less than tested jointly by JARL the known as the "coffin" a number examples to show about 45 SLU out - stations in Japanese national amateur-radio configuration. More likely is how delays and errors were contact with the "Windy Ridge" and NASDA, Japan's that the receiver was a adversely effecting business and society base station, handling large national space agency, is due to "straight" r. f. /regenerative personal users of the radio quantities of Ultra and Pearl be launched from the detector /a.f. receiver similar to spectrum. In reply, John traffic enciphered with one -time Tanegashima space centre in the Mark XV receiver. It once Butcher, Under - secretary of pads or Britain's successful early 1986 on board a newly fell to my lot in less State for Trade and Industry, answer to Enigma, the Type X developed H -1 two -stage unfavourable circumstances to simply filled in time by cipher machine. launcher, as part of a multi - manoeuvre a "coffin" package describing some of the many So while agreeing that the payload. This will be the first up a steep narrow spiral tasks of RRD without getting idea of mule- humping such multi- payload launch by NASDA staircase and can confirm it was round to his promised outline of equipment around the and the agency will depend on no lightweight, miniaturized "Government's policy on the mountains of Yugoslavia must the telemetry from -1 iin equipment! enforcement of wireless JAS have been well calculated to assessing results. Orbital height However I must come to the telegraphy legislation" before fuel the often bitter rivalry of the 50kg JAS-1 will be about defence of what Mr King terms being saved by the bell. between S0E and British 1500km, inclination about 50° "the notorious Mark III" While RRD has been -a Intelligence, it can be argued and period about 120 minutes two -stage transmitter built in successful in closing some but that the "notorious" Mark III (roughly similar to Oscar 7). various versions throughout of by no means all of the pirate successfully provided some Ground stations will have about World War II at Whaddon and broadcasters, a good example of the most vital radio links of eight passes per day, with Little Horwood, near Milton confused state of WWII, despite its bulk and lack the of about 20 minutes. Keynes. Allegedly based on a enforcement concerns the "windows" of miniaturization! JAS -1 will carry two mode -J 1938 design in one of the power given to RRD by the (145MHz up, 435MHz down) American amateur radio 1984 Telecommunications Act transponders with a design handbooks it usually comprised In brief to specify "restricted" lifetime of three years. One will a wooden -boxed, crystal - After a long interval, amateur transmitting equipment and so be a conventional linear controlled 6V6 oscillator and radio licences are again being make manufacturing, selling, transponder, the other a digital 807 power amplifier with a issued in Turkey, with the first offering for sale or hire of it store- and - forward transponder separate (heavy) mains power going to Dr Unal Akbal who illegal. In the twelve months for communication between supply unit. It delivered about becomes TA1A... A number of following the enactment of this stations in different time zones. 25 watts r.f. output between special callsigns with the prefix legislation not a single The digital transponder will about 3 to 16MHz with plug-in "GV" were issued for use in restriction order has been have four input channels in the coils. It was a versatile and early May by special event formulated. 145MHz band using p.s.k. /f.m. reliable transmitter although the stations marking the 40th What is one to make, for with a single 1200 -baud power unit could occasionally anniversary of the end of World example, of the low -power downlink at 435.91MHz. catch fire, and it was all -too- War 2 in Europe... British television transmitters recently AMSAT -UK reports that two easy to tune the p.a. to a Standard BS6527:1984 provides announced by Waveview more Russian amateur harmonic. a specification for "Limits and Holdings Ltd of South London? satellites, RS -9 and RS -10, may Although not designed for measurements of spurious These range from outputs of 4 be launched this year. RS -10 field operation it was sometimes signals generated by data to 200mW for their "Multiview" will carry Mode A (145.9MHz run from vehicle batteries with processing and electronic office but does not appear series and 1 to 1000 watts for up, 29.5MHz down) and Mode the aid of a rotary converteror equipment" low -power television. The K (21.2MHz up, 29.5MHz alternatively from a 150 watt specifically to cover home Multiview units are being down) and possibly also a Onan petrol -electric generator, computers which can be the offered for use in homes, 21.2MHz up, 145.9MHz down though these were far from source of considerable problems hotels, etc. as local "cordless" transponders. "portable ". to radio amateurs... The distribution systems with JARL hhas a special station at The original purpose of the Tyne -Wear Repeater Group outputs tuned to u.h.f. channel the large International Science Mark III was for the British reports that both of their and 36, one of the non -allocated and Technology Exposition 85 Intelligence h.f. network repeaters - GB3TW (R5) are now channels between Bands IV and at Tsukuba (100km north of organized from 1938 onwards GB3NT (RBo) - Pat Hawker, V and used by airport radars, Tokyo) from March 17 to by (Sir) Richard Gambier -Parry operational. etc. All such units, even the September 1, 1985. Visiting ( "G.P." or "Pop") with most of G3VA. 1985 24 ELECTRONICS & WIRELESS WORLD JUNE

www.americanradiohistory.com VISIT OR ߣfßTRf

PHONE EnRaDfrn OPEN 6 DAYS HEflRV'S gig!: A WEEK ALL STOCKS AUDIO ON DISPLAY ELECTROf1ICS `'2 Equipment Communications Computers Components INSTRUMENTS STOCKED SWITCH MODE AND LINEAR POWER SUPPLIES SCOPES (UK C/P £6.50) Gould and ITT/SIC HAMEG (UK C/P & ins. £1.50 eachl HM203/5 Dual 20MHZ £264.00 HM204 Dual 20MHZ £365.00 A.12/15V 500mA linear £6.91 HM605 Dual60MHZ £515.00 8.12 /15V lamp linear £8.65 ' CROTECH C. 5V 3 amp linear £8.65 3030 15MHZ Portable C188.00 D. 5V 2 amp Eurocard linear £7.78 3035 15MHZ Bench £208.00 E. 5V 10 amp SW made £15.61 3132 Dual 20MHZ £312.00 F. 5V 20 amp SW mode £ 19.96 ('HAMEG /CROTECH INCLUDE COMPONENT TESTERSI 6. 5V5Á.- 23V0.25A.- 12V CIA. HITACHI 12V 0.5A. SW mode £ 17.35 V212 Dual 20MHZ £329.00 H. 5V 2A. - 30V 0.025Á. - 12V 0.1A. 12V mode £ 17.35 V222 Dual 20MHZ' £395.00 0.35A. SW I. 24V input 12 volt 1.2A mode V223 Dual 20MHZ £450.00 DC SW convertor V423 Dual 40MHZ £650.00 £5.17 v650 Dual 60MHZ' £880.00 'with probes SOFTWARE THANDAR SC11OA 10MHZ battery/mains £175.00 (Please state format required and machine) GATEWAY /PATHWAY Relational database SCOPE PROBES 01 -010 £10.00 for all CP /m £100.00 MDIS Intelligent Disassembler for all GENERATORS (UK C/P £1.00) CP/m based £50.00 (F) Function (P) Pulse (A) Audio (RI RE IVC HI -RES Provides Pseudo high resolution 500 0.1 HZ- 500KHZ (F) £110.00 Ì graphics £15.00 TG101 0.02HZ- 200KHZ IFI £110.00 Here is the complete for TG102 0.2HZ -2MHZ (F) £160.00 DISKPEN (063) Low cost word processor range of lCOlv1 marine radio -telephone equipment, from left to 111501 0.005H2 -5MHZ (F) £295.00 muffiboard based overlays tor diskpen £50.00 right: the M700 HF TG105 5HZ -5MHZ IPI £105.00 MAXIFILE £20.00 SSB transceiver offers long -range capability at SPOOLER £15.00 a sensible price. The M5 VHF hand AG202A 20HZ- 200KHZ (A) E 99.00 -portable, quick channel tAG27 10HZ -1 MHZ (A) £115.00 HENRY'S CP /m UTILITIES access with its push -button keyboard. M12 and M2 VHF hand - SG402 100HZ -30MHZ (R) £79 00 41 Programs £15.00 portables, 12 and 56 channels respectively LSG17 100HZ- 150MHZ (R) £115.00 ALL DISC Variable disc format for GEMINI/ using knobs or thumb - ÁG203 10HZ-1MHZ £155.00 wheels. Finally the M80 VHF (Al NASCOM CP /m's £150.00 radio -telephone, a wide range of PREZTEL 2 Interface Galaxy or Nascom to POWER (UK C/P £2.00) options are available for this and all other ICOM marine radios. SUPPLIES Modem for use with BT Preste) service £26.04 ' Twin ICOM radios are versatile, rugged, water -resistant and meter Single meter (switched) + Digital 241 0 /30v 0 /1AMP £33.00 ASCII KEYBOARDS most important of all - reliable. 242 0/30v 0 /3AMP £52.13 More detailed information is readily available from your 154 5/15v 0 /4AMP £43.43 69S D5 Compact 64 key local ICOM dealer or from '2302 0 /30v 0/ 2AMP + - 5 function keys. Hall direct Thanet Electronics Ltd. 5v 1A AND PULSE GEN £230.00 effect keyboard with + PL320 0/30v 2AMP £145.00 reprogrammable (2716) frame for COUNTERS ASCII output decoder EPROM. Steel key (UK C/P £1.00) good rigidity. Negative going strobe. Requires 5 volt Thanet - LED LCD AN 8 digit 12 Electronics Ltd volt supplies. (UK C/P £1.00) Suppliers of Radio Communication Equipment to the Ministry of Defence. * 100 100MHZ £99.00 £21.70 143 Reculver Road. Herne Bay, Kent. England. Tel (0227) 363859/363850. 600 600MHZ £125.00 2070 COMPACT 58 KEY KEYBOARD + 1000 1000MHZ £175.00 Contactless capacitive high reliability keys. Full 128 + TF600 600MHZ £132.50 ASCII codes. Steel key frame for positive rigidity CIRCLE 28 FOR FURTHER DETAILS. TF 040 40MHZ £120.00 1mS strobe. single ( 5 volt supply. Repeat TF200 200MHZ £175.00 key. control and caps. lock. (UK C/P £ 1.00) £28.26

TV EQUIPMENT (UK C/P E1.00) COMPUTER POWER SUPPLY TC40 VHF /UHF F/S meter £215.00 LTC910A Tube Tester £ 199.00 Switch mode. Stabilised. Self protecting S/C MC321 PAL(UK) Colour gen. £252.00 protected. etc. 220/24011 AC 5V 3.3A , 12V MC32BPAL(B) Colour gen. £252.00 2.4A. 40% cycle - 5V 0.5A - 12V 0.5A. Suitable LHM80A 400v meter £30.00 Apple replacement I UK C/P £1.50) £50.00 STOCK SELECTION ITT 2020 CABINET Ipanfechnic) (UK C/P 65p 'UK C /PE1.50) LP1 10MHZ Logic Probe £24.95 Professional computer case OP70 30MHZ Logic Probe £29 00 wiVC keyboard cutout. 50MHZ Logic Probe £57.00 DP71 18 x 15.5 x 4.5 (Irani slopes). ST300 AC Clamp Meter £30.87 Ideal for single board computers like YF501 Elec. Ins. Tester £59.13 the Nascom or Gemini Multi- board (3 ca ds. etc). DM6013 Digital Cap Meter £60.43 Very heavy gauge (.25 ) plastic with metal base. KDm6 200MHZ TR DIP Meter £48.70 Anractive silver grey finish. (UK C/P £1 78) LCR740 LCR Bridge £230.00 £ 19.95 design manufacture and 0M358 Scope Multiplexer £169.00 supply H165 Scope Comp. Tester £24.00 COMPUTER FANS TCt Transistor Tester £24.30 (UK C/P 60p each. £1 00 per pair) CM200 Bench Dig. Cap. Tester £89.00 4 220/230V AC Brand new £6.52 POWER AMPLIFIERS 4 220/240V AC Ex -units £4.78 (UK HAND DMM's 3'/: digit C/P 65p) 4 '.: 110/115V AC Ex -units £4.35 HIGH POWER ASSEMBLIES (R) Rotary (PB) Push -Button With case 350010A AC /DC (R) £41.48 CONTROL CIRCUITRY 3510 Plus Hie & Buzzer (R) £47.78 CASSETTE ti ME540 10A AC /DC Auto /Man (R) £41.50 MECHANISMS DM73 Auto -range probe buzzer £39.75 KD615 10A DC Hfe Tester (R) £34.75 Fitted counter. Motor. Stereo for application 6010 10A AC /DC (Pit) £37.83 record and erase heads. in 703010A AC/DC 0.1% (PB) £46.91 Aulostop. solenoid. Brand new K955C t0A AC /DC (R) £38.70 available 6V DC or 12V DC (state which). KD528T Minature with Hfe test £29.52 (UK C/P 65p) £5.17 INDUSTRY DM20 10A AC /DC Hfe conductance IR) £47.00 ALSO miniature stereo cassette replay 0M77 IDA AC /DC Auto buzzer IR) £46.00 mechanism 12v. 105 x 100 x 40mm. PUBLIC ADDRESS 353010A AC/DC Me Cap. buzzer IR) £57.29 (UK C/P 65p) £4.78 HI -Fl BENCH OMMs IUK C/P £1.001 TELETEXT BOARD TM355 3y2 digit LED 0.25% £85.00 Mollard VM6101/5 board. Complete and brand new TM356 3y, digit LCD 0.25 % £95.00 IUK C/P El 00) t Thorn TX91 TM351 3,6 digit LCD 0.1% £115.013 £10.87 s available 5025 3'¡a digit Auto-rnanual comparator £210.00 'TOROIDAL TRANSFORMER 5030 3) digit Auto -manual comparator £137.00 250 watt isolating trans Rus 22v 1A. 't Yr'> 1503A 4y4 digit LCD 0.05% £169.00 6.3v lA 4' /r dia. x 13/4 . 1503Ha 431, digit LCO 0.03° ° £185.00 OFF THE SHELF 15044 4 digit LCD True OMS £199.00 £4.50 IUK C/P 85p) CUSTOMISED ALSO IN STOCK Large ran e of analogue multimeters. breadboards. C A D DESIGNED SUPPLIERS OF ELECTRONICS FOR EVERY PURPOSE Official Orders Welcome (Nhpol to cnrhrrmnat,oni ORDER BY POST OR PHONE 301 Edgware Road, London W2 Test Equipment Audio 01- 724 3564 404 Edgware Road, London W2 Up to £1000 instant credit sis tel. 01.361.8715 132 High Road Available through sr ALL \ Computers 01.402 6822 Lombard Tricity Finance PRICES telex 266 873 New Southgate Equipment 01- 724 0323 EXCLUDE PANTEC G LONDON N11 1PG. CALL IN AND SEE FOR YOURSELF Components 01-7231008 VAT CIRCLE 37 FOR FURTHER DETAILS. CIRCLE 58 FOR FURTHER DETAILS.

ELECTRONICS & WIRELESS WORLD JUNE 1985 25

www.americanradiohistory.com 01-208 1177 TECHNOMATIC LTD 01-208 1177 DISC DRIVES BBC Micro Computer System TECHNOMATIC drives are fitted with high quality slimline Mitsubishi mechanisms and are available with or without integral mains power supply. The dual drive power supplies are switch BBC Computer & Econet Referral Centre mode type and are generously rated. All drives with integral power supply are fitted with a mains indicator. All drives are supplied with all the necessary cables, manual and a formatting disc. All drives BBC Computers: are capable of operating in single or double density modes. Model B: £299 (a) B +DFS: £346 (a) Single Drives: Model B +Econet: £335 (a) B +Econet +DFS £399 (a) 1 X100K 40T SS: TS100 £85 (b): PS100 with psu £125 (b) 1 X400K 80/40T DS: TS400 £125 (b); PS400 with psu £149 (b) ACORN 10 Mbyte Hard Disc £1300 (a) Dual Drives ACORN 2nd Processors: 6502: £175 (a) Z80: £352 (a) Stacked Version: TORCH UNICORN: Z80 Card: £275 (a) Z80 Disc Pack: £599 (a) 2X100K 40T SS: TD200 £175 (a), PD200 with psu £200 (a) 2X400K 80/40 DS: TD800 £250 (a); PD800 with psu £290 (a) TORCH Graduate G80012 £999(a) Plinth Version: 20 Mbyte Hard Disc +400K Floppy: £1950 (a) 2x100K 40T SS: TD200P £195 (a); PD200P with psu £220 (a) 2x400K (80/40) DS: TD800P £265 (a); PD800P with psu £305 (a) We stock the full range of ACORN hardware and firmware and a very wide range of other peripherals and firmware for the BBC. For detailed specifications Authorised Distributor for leaflet. and pricing please send our Data Recording Products 3M PRINTERS 3M FLOPPY DISCS Industry Standard floppy discs with a lifetime guarantee Discs in packs of 10 RX100 (a); EPSON: RX8OT £210 (a); RX8OFT £220 (a); £345 40 Track SS DD £13 (c) 40 Track DS DD £18 (c) FX80 (a); FX100 £430 (a); JX80 Full Colour Printer £525 (a) £315 80 Track SS DD £22 (c) 80 Track DS DD £24 (c) KAGA TAXAN: KP810 £255 (a); KP910 £359 (a) BROTHER: HR15 £340 (a); JUKI 6100 £340 (a). FLOPPICLENE DRIVEHEAD CLEANING KIT GRAPHICS PLOTTER WORKSTATION Complete £490 (a) FLOPPICLENE Disc Head Cleaning Kit with 28 disposable cleaning discs ensures continued Basic Plotter £270 (a); HI- Plotter £399 (a) optimum performance of the drives. £14.50 (b) DRIVE ACCESSORIES Single Disc Cable £6 (d) Dual Disc Cable £8.50 (d) ACCESSORIES 10 Disc Library Case £1.80 (d) 30 Disc Storage Box £6 (c) EPSON Serial Interface: 8143 £28 (b); 8148 with 2K buffer £57 (b). 30/40 Disc Lockable Box £14 (c) 100 Disc Lockable Box £19 (c) EPSON Paper Roll Holder £17 (b); FX80 Tractor Attach £37 (b); RX/FX80 Dust Cover £4.50 (d) BUFFALO 32K Buffer for Epson printers £99 (d). EPSON Ribbons: MX/RX/FX80 £5.00; MX/ RX/FX100 £10 (d). MONITORS Ribbon £2.50 JUKI: Serial Interface £65 (c); Tractor Attach, £99 (a); Sheet Feeder £180 (a); MICROVITEC 14in. & 20in RGB (a) 1431 Std Res £165 (a); 1431 Ap std Res PAUAudio £205 (a); BROTHER HR 15: Sheet Feeder £199; Ribbons Carbonor Nylon £4.50; Muf88trike £5.50 - 1451 Med Res £240 (a); 1441 Hi Res £389 (a); (d); 2030CS Std Red £380 (a); 2040CS Hi Res £665 (a) 200C Sheets Fanfold with extra fine pert. 9.51n. - £13; 14.51n. £18.50 (b). Plinth for 14in. Monitors £8.50. BBC Parallel Lead £8 Serial Lead 127 (d). Microvitec Monitors with TTULinear Inputs also available.

KAGA TAXAN 121n. RGB Vision II Hi Res £225 (a); Vision Ill Super Hi Res £325 (a) Green Screens; KAGA 12G £99 (a); SANYO DM811 112CX £90 (a); BT Approved Modems Swivel Stand for Kaga Green £21 (c) MIRACLE WS2000: BBC Leads: KAGA RGB £5 Microvitec £3.50; Monochrome £3.50 (d) The ultimate world standard BT approved modem covering SOFTY II SANYO CD 3125 NB 14in. RGB Std Res £169 (a) all common BELL and CCITT standards up to 1200 Baud. Allows communication with virtually any computer system in This low cost intelligent the world. The optional AUTO DIAL and AUTO ANSWER eprom programmer can UV ERASERS PRINTER BUFFER /buffer provides a simple way to boards enhance the considerable facilities already provided program 2716, 2516.. UVIT Eraser with built -in timer and mains indicator. This printer sharer upgrade a multiple computer system by providing the modem. Mains powered. £129 (c) Auto Dial Board/ 2532, 2732, and with an interlock to avoid accidental exposure on Built -in safety greater utilisation of available resources. The buffer adaptor, 2564 and 2764. Auto Answer Board £30 (d) each (awaiting BABT approval). to the harmful UV rays. otters a storage of 64K. Data from three computers Software lead £4.50 Displays 512 byte page on It can handle up to 5 eproms at a time with an average can be loaded into the buffer which will continue BUZZBOX: TV- has a serial and par- erasing time of about 20 mins. £59 + £2 pip. accepting data until it is full. The buffer will automati- to next as soon as This pocket sized modem complies with V21 300/300 Baud allel I/O routines. Can be UV1 as above but without the timer. £47 + £2 pip. cally switch from one computer all its data. The computer and provides an ideal solution for communications between used as an emulator, cas- For Industrial Users, we offer UV140 8 UV141 era- that computer has dumped then is available for other uses. LED bargraph indi- users, with main frame computers and bulletin boards at a sette interface. sers with handling capacity o114 eproms. UV141 has cates memory usage. Simple push button control II full built in safety features very economic cost. Battery or mains operated. £62 (c) Softy í195.00(b) a built in timer. Both offer provides. REPEAT, PAUSE and RESET functions. Mains Adaptor £8 (d) BBC to Modem data lead £7 Adaptor for 2764/ UV140 £61, UV141 £79, pip £2.50. Integral power supply. £205 (a). 2564 £25.00 Cable set f30. ATTENTION CONNECTOR SYSTEMS All prices in this double page advertisment are subject to change without notice. AMPHENOL TELEPHONE I.D. CONNECTORS EDGE CONNECTORS CONNECTORS ALL PRICES EXCLUDE VAT 36 way plug Centronics (Speedblock Type) 475p 4 -way plug 110p Please add carriage 50o unless Header Recep- Edge CONNECTORS (solder 500p (IDC) No of 6 -way plug 180p indicated as follows: was Plug 'acre Conn. 36 way skt Centronics 500p n ang.skt 160p £1.50 (dl £1.00 0.1" 0156- (solder) 550p (IDC) 6-way (a) £8 (b) £2.50 Ici 20 1445p 1255pp 195p 2 6-way (commodore) - 300p 24 way plug IEEE (solder) Flexible cable 26 175p 150p 240p 150p 2.<10-way - 475p (IDC) 475p 4 -way 50p /m 34 200p 160p 320p 2 x 12-way laic 201 350p IEEE INTERFACE - 24 way skt IEEE (solder) 72p /m ACORN 40 220p 190p 340p 2 x 18-way - 140p 6 -way A full implementation of the IEEE -488 standard, pro- 50 235p 200p 390p 2 x 23-way (ZX81) 175p 220p 500p (IDC) 500p 225p 220p Pin viding computer control of compatible scientific & 2 x 25-way PCB Mtg Skt Ang RIBBON CABLE 2 x 28-way (Spectrum) 200p 700p 36 way 750p than other sys- - 24 way (grey /metre) technical equipment, at a lower price 2 x 36-way 250p - D CONNECTORS 10 40p 34-way leap in work 1 s 43-way 260p -way tems. Typical applications are experimental No of Ways - 2 x 22-way 190p - GENDER CHANGERS 16-way 60p 40 -way 180p in academic and industrial laboratories. The inter- 15 37 9 25 2 x 43-way 395p - 25 way D type 20 -way 55p 50 -way 200p 500p of up to 14 other compati- 1 x 77 way 400p face can support a network MALE: 26 -way 120p 64 -way 290p ble devices, and would typically link several items of Ang Pins 120 180 230 350 2 x 50.wayiS100conni 600p - Male to Male ... £10 test equipment allowing them to run with the opti- Solder 60 85 125 170 Male to Female £10 DIL HEADERS IDC 175 275 325 Female to Female £10 mum of efficiency. The IEEE Filing System ROM is - IDC FEMALE: EURO CONNECTORS Solder 40p 100p supplied £282. St Pin 100 140 210 380 14 pin RS 232 JUMPERS 50p 110p Ang Pins 160 210 275 440 DIN 41612 Plug Skt 16 pin 60p Solder 90 130 195 290 2 X 32 way St Pin 230p 275p (25 way DI 18 pin - INDUSTRIAL PROGRAMMER 2 X 32 way Ang Pin 275p 320p 24" Single end Male £5.00 20 pin 75p - IDC 195 325 375 £5.25 way St Pin 260p 300p 24" Single end Female 24 pin 100p 150p EP8000. St Hood 90 95 100 120 3x32 Female £10.00 400p 24" Female 160p 200p controlled Emulator Programmer is a pow- Screw 130 150 175 3X32 way Ang Pin 375p Male Male £9.50 26 pin This CPU - 24" 200o 225p tool for both Eprom programming and develop- Lock IDCSktA +B 400p 24" Male Female £9.50 An Din erful IDCSkIA +C 400p ment work. EP8000 can emulate and program all MISC CUNN . eproms up to 8Kx8 bytes, can be used as stand TEXTOOL ZIF For 2 x 32 way please specify DIL SWITCHES 105p 21 pin Start Connector 200p duplicating EPROMS, as a SOCKETS 24 -p, 17.50 spacing (A + B, A + C). 4 -way 90p 6 -way alone unit for editing and 8 Video Connector 200P 28 -pin £9.00 40 -p"- [12.00 8 -way 120p 10 -way 150p pin slave programmer or as an eprom emulator £695(a) Using 'Prestel' type protocols. For information TECHNOLINE VIEWDATA SYSTEM. TEL: 01 -450 9764 and orders - 24 hour service, 7 days a week

ELECTRONICS & WIRELESS WORLD JUNE 1985 26

www.americanradiohistory.com 741526. 0.60 74 SERIES 74273 2.00 , 502 0.55 7415273 1.25 74C SERIES 74276 1.40 4503 0.36 LINEAR ICs 7400 7415279 4504 0.95 COMPUTER COMPONENTS 74278 1.70 0.70 74000 0.70 4505 3.60 L01709 0.35 7401 7415280 1.90 007581 15.00 T60810 0.90 CPU 8287 4.25 EPROMS MC14411 9.00 KEYBOARD 74279 0.90 74C04 0.50/ 4506 0.90 A000808 11.90 LM710 O.4 7402 7415283 0.80 160820 0.80 1802CE 6.50 82680 11.00 MC14412 7.50 E NC ODE R5 74263 1.05 4507 0.35 451791000 25.00 1M711 1.00 4069 1608209 0.75 26504 10.50 7403 7415290 0.80 4508 1.20 AN103 87755A 18.00 2516+5V 3.50 75107 0.90 74742 3.20 74C08 0.70 2,00 151723 0_50 780920 2.00 A752376 11.50 7404 74LS292 9.00 4510 655 0-I-5050 100 LM7245CH 3.00 6502 3.50 TMS9903 25.00 2516-35 5.50 75108 0.90 74290 0.90 74010 0.70 764950 2.25 AY53600 7.50 7405 74L5293 0.80 4511 0.55 AY-3-1350 3.50 1.18733 0.65 65CO2 12.00 TMS9911 18.00 2532 4.50 75109 1.20 74293 0.90 74C14 0.50/ 4512 0.55 TC9109 5.00 740922 5.00 7406 7415295 1.40 AY3.8010 4.50 LM741 0.22 TCA210 3.50 6502A 5.50 TMS9911 14.00 2532 5.50 75110 0.90 74298 1.80 401064584 4513 1.50 AY.3-8910 400 LM747 0.70 740923 6.00 7407 7415297 9.00 TC4220 3.50 65028 8.00 2564 9.00 75112 74351 2.00 4514 1.10 41.3.0912 5.00 LM748 0.30 Z80PIO 2.40 1.80 74C20 0.70 4515 TCO270 3.50 6800 2.50 2708 4.00 7408 74365A 7415298 1.00 1.10 CA30194 1.00 LM1011 480 Z80P10 2.50 75113 1.20 BAUD RATE 0.80 74C32 1.00 4516 0.55 100940 1.75 6802 7409 74L5299 2.20 CA30284 1.10 LM1014 150 7001010 215 3.00 Z8OCTC 2.50 2716+155 3.50 75114 1.40 GENERATORS 74366A 0.80 74C42 1.50 4517 2.20 7409 7415321 3.70 CA3046 070 1M1801 3.00 1041022 400 6809 6.50 2.75 2716-35 5.50 75115 1.40 74367A 0.80 74C48 á5I8 0.1 CA3059 161830 2.50 Z80ACTC MC14411 7.50 74LS322A 1.50 3.25 1041024 1.10 6809E 12.00 2732 4.50 7410 74368A 3.90 519 0.32 cA3060 3.50 LM1871 3.00 Z80DART 8.50 75121 1.40 0.70 74C73 1.00 1001005 3.00 68809 12.00 COM8116 6.50 7411 7415323 3.00 4520 060 CA3o8oE 0.70 LM1872 3.00 Z80ADART 7.00 2732A-2 7.00 75122 1.40 74376 1.60 74C74 1.20 4521 7042002 625 47028 7.50 7412 7415324 3.20 1.15 CA3066 010 LM1886 5.50 1002003 110 68609E 16.00 Z800MA 7.00 27326-30 6.00 75150P 1.20 74390 1.10 74C76 1.00 4522 0.50 CA3089E 2.10 M1889 3.50 1042004 240 68000-L8 36.00 2732A-35 5.00 7413 74393 74LS348 2.00 4526 070 TMS4500 14.00 75154 1.20 1.20 74C83 2.00 CA309040 375 LM2917 3.00 T1142006 320 3.50 7414 74LS352 1.20 4527 0.80 8035 TMS9901 5.00 2764-25 4.50 75159 2.20 74490 1.40 74C85 CA3130E 0.90 LM3302 0.90 7042020 310 74L5353 2.25 4528 0.65 8039 4.20 27256-30 AY31015P 3.00 7416 1.20 74C860.50/40/ CA31301 1.30 LM3900 0.80 7042030 2.50 TMS9902 5.00 54.00 75160 5.00 4529 1.00 CA3140E 0.45 043909 1.00 8080A 4.20 27256-25 63'51013P 7417 74 LS SERIES 7415356 2.10 TpA2591 4.00 Z80ADMA 7.50 60.00 75161 3.50 3.00 70 4507 4531 0.75 CA31401 1.00 LM3911 1.60 8085A 3.00 7420 74LS363 1.80 4532 TDA3810 750 21306310 27C6425 10.00 75162 4.00 COM8017 3.00 74C90 1.90 0.65 CA3146 2.25 1443914 3.50 7.00 7421 741500 0.24 7415364 1.80 4534 3.80 1047000 350 8086 22.00 2712825 9.50 75172 3.00 I646402 4.50 74C93 1.50 543160E 0.90 1363915 3.40 TEA1002 741501 0.24 7415365 0.50 4536 2.50 700 8088 17.50 MEMORIES 2712830 9.50 75182 7422 CA3161E 2.00 163916 3.40 TLO61CP 040 0.90 74L002 74C95 1.60 4538 0.75 6.00 LM13800 1.50 8741 16.00 MODULATORS 7423 0.24 7415366 0.50 CA3162E TL062 0.60 2016-1504.00 27256-25 36.00 75188 0.60 74C107 1.00 4539 075 CA3169E 2.70 6515131 2.30 8748 18.00 7425 741503 0.24 7415367 0.52 TL061 0.90 TMS2716 5.00 75189 0.80 4541 0.90 CA3240E 1.50 9515161 4.50 2101 4.00 6MHZ 3.75 741504 74C150 5.00 TLO71 040 TMS1601 12.00 7426 0.24 7415368 0.50 4543 070 683712 200 2102 75365 1.50 740151 2.00 CA3280G 2.70 11072 070 TMS998012.00 2.50 CRT BMHZ 4.50 741505 0.24 74L5373 4551 1.00 12.10 MC1310P 1.50 75450 7427 0.90 CA07002 11074 1.10 21078 5.00 CONTROLLER 0.80 74C157 2.50 4553 2.40 D7002 6.00 MC1413 TM5999512.00 SOUND 8 VISION 7428 741508 0.24 7415374 0.90 0.75 71,08; 0.35 21116-35 4.00 75451 0.50 74C160 1.60 4555 0.36 DAC1409.8 3.00 MC1458 0.15 WD55 14.50 CRT5027 18.00 7430 741509 0.24 7415375 0.75 4556 11082 015 2114-3 2.50 75452 0.50 74C161 1.80 0.50 DAC0800 300 5514953 250 Z80 2.80 CRT5037 1200 12MHZ 12.00 7432 741510 0.24 4557 2.40 DAC0808 100 TL013 0.15 2147 4.00 75453 0.70 74C 162 1.80 3.00 11004 1.00 CRT6545 9.00 74L511 0.24 7415378 1.40 00305 3.00 Z80A 3.25 75454 CRYSTALS 7433 0.95 MC14965 0.70 TL091 2.00 4027-3 0.70 74C163 1.80 4566 1.40 1.90 808 7.00 3.00 EF9364 8.00 7437 7415 12 0.24 7415379 1.40 MC3340P 2.00 110170 0.50 75480 1.50 32.768KHZ1.00 74C173 1.00/ 4568 2.40 ICL71o6 6.75 SUPPORT 4116-15 2.00 EF9365 25.00 741513 MC3401 0.70 1L430C 7438 0.34 74L5381 4.50 4569 1.70 ICL7611 095 1.20 4116-20 1.50 25.00 75491 0.65 1.00MHz 2.70 4076 1853403 0.65 U4410033 935 DEVICES EF9366 7439 7415 14 0.50 7415390 0.60 572 0.45 ICL76500 4.00 75492 0.65 1.8432MHz225 MF10CN 3.00 2. 1 4118-3 5.00 EF9367 36.00 74C174 ISO 4583 0.90 V4759 3.20 7440 741515 0.24 74L5393 0.95 £1.7840 2.50 MK50240 9.00 4125820 10.0000 8T26 1.20 2.00MHz 2.25 74C175 1.50 4584 0.1 ICL8038 4.00 U42240 1.20 3242 8.00 MC6845 8.50 7441 741520 0.24 74L53954 0.60 6650398 1.00 U44170 1.70 4164-15715.00 8T28 1.20 2.45760MHZ(L) 74C192 150 4585 0.00 0472168 22.00 ML920 5.00 3245 4.50 MC6845SP 0.50 7442A 741521 0.24 74L5399 1.00 4724 UC144801 A 5.50 4164-15 3.00 8T95 1.20 74C193 1.50 £047217 7.50 ML922 1.00 6520 3.00 MC6847 8.50 2.00 1.50 ULN20034 0.75 4164-20 74434 74LS22 0.24 7415445 1.80 lust 9.00 ICM7555 0.90 144982214 3.00 3.00 8796 1.20 2.45760Mhz(S) 74C194 1.50 111.520044 0.75 6522 3.50 SFF96364 8.00 741524 0.50 7415465 1,20 .12 7.50 ICM7556 1.40 NE529 3.20 4416-15 4.00 8797 1.20 7444 74C195 ULN2068 2.90 6522.5 5.50 TMS9918 15.00 250 1.50 11416 3.00 LC7120 3.00 NE531 1.20 7445 741526 0.24 7415467 1.20 ULN2802 1.00 4532-20 2.50 8798 1.20 2.5MHz 250 74C221 2.50 14419 210 LC7130 3.00 NE544 1.90 6532 4.80 TMS992810.00 7446A 741527 0.24 74LS490 150 ULN2803 1.80 4816AP-3 811595 1.40 14490 4.20 LC7131 3.50 NE555 6551A 2.00 2.662MHz 1.75 74C244 2.00 0.22 ULN2804 1.90 5.25 7MS992910.00 7447A 74LS28 0.24 7415540 1.00 14495 4.50 LC7137 3.50 5101/5501 3.70 81LS96 7.40 3.276MHz 1.50 74C245 2.25 NE556 0.60 URC575 2.75 68821 2.20 7448 741530 0.24 7415541 1.00 14500 5.50 LF347 1.20 NE561 400 5514/5114 1.50 61LS97 1.40 UPC59214 2.00 6829 1250 3.5795MHz1.00 74C373 2.25 11599 2.00 IF351 0.50 NE565 1.20 5516 5.50 NTERFACE 7450 741532 0.24 7415608 7.00 UPC71566 3.00 81LS98 1.40 4.00MHz 1.50 74C374 2.25 22108 3.50 LF353 0.90 NE586 1.50 6840 3.75 ICS 7451 74L033 0.24 7415610 19.00 13PC118514 5.00 88LS120 3.00 22101 7.00 LFS55 0.90 NE567 1.25 68840 8.00 4.194MHz 2.00 74C902 1.20 X6210 4.00 ÁD75811 15.00 7453 741537 0.24 7415612 19.00 7.00 Lf356N 1.10 6116P -3 3.50 9602 3.00 4.43MHz 1.00 74C911 9.00 NE570 4.00 362206 4.00 6850 1.80 74L538 0.24 7415624 3.50 wä14 15357 1.00 NE571 2.50 4.00 ADC080812.00 9636A 1.80 7454 XR2207 315 68650 2.50 61161P -3 4.608MHz 2.50 74C912 4.50 40085 1.20 LMIOCLH 4.50 NE592 AD561J 20.00 7460 741540 0.24 7415626 2.25 090 X62211 575 6264P- 1522.00 9637AP 1.80 4.9152MHz2.50 74C922 6.00 40097 0..16 LM3014 030 6852 2.50 7470 74LS42 0.50 7415628 2.25 NE5532P 1.50 002216 6.75 AM25S10 3.50 9638 2.00 74C923 40098 0.40 101307 0.45 NE5533P 1.60 6854 8.50 5.00MHz 1.50 6.50 1102240 130 AM25152521 3.50 7472 741543 1.50 7415629 1.40 40100 1.50 101308CN1 0.75 NE5534P 1.20 6810 1.60 5.068 74C925 6.50 26404 1.00 68854 8.00 DISC 1.75 7473 741547 0.80 74L5640 3.00 40101 1.25 LM310 2.25 NE5534AP 1.50 745189 2.25 AM25152538 3.50 74C926 76414 0.50 6875 5.00 CONTROLLER 6.00MHz 1.40 7,50 40102 1.50 L6311 0.60 OP07EP 5.00 AM26LS31 1.20 7474 74LS48 0.90 7415640-1 3.00 2N419P 1.75 745201 3.50 ICs 40103 2.00 1M318 1.40 RL024 500 8154 8.50 6.144MHz 1.40 7475 741551 0.24 7415641 2.00 214423E 1.50 745289 2.25 AM26LS321.20 74ALS SERIES 40104 1.20 1.6319 1.50 RC4156 0.55 8155 3.80 7.00MHz 1.50 74L554 214424E 1.30 4917910pC 25.00 7476 0.24 7415642 2.50 40105 1.50 16324 0.45 RC4151 2.00 93415 6.00 6843 8.00 7.16MHz 1.75 40106 26425E8 3.50 8156 3.80 7480 741555 0.24 7415642-13.00 74ALSOO 0.45 0.45 LA1331Z 1.15 RC4195 1.50 931422 9.50 06C80- 8271 P.O.A. 40107 0.55 1043352 1.30 ZN426E8 100 8205 2.25 8.00MHz 1.50 7481 7415734 0.30 74LS643 2.50 74ALS02 RC 4558 0.55 93425 I C81-V 28.00 0.45 40100 3.20 101336 1.50 26427E8 6.00 8212 2.20 6. 8272 13.00 8.867MHz 1.75 7483A 7415740 0.35 7415643-1 3.00 74AL504 55668 2.20 26428E8 450 DM8131 6.00 FD1771 0.50 40109 1.20 LM339 0.40 550240 9.00 8216 1.80 PROM 30.00 10.00MHz 1.75 2N429E8 1n DP8304 3. 74844 741575 0.45 74LS644 3.50 744L508 0.50 40110 215 LM318 0.00 5441900 19.50 FD1791 20.00 ZN447E 9.50 8224 P.A.O. 10.50MHz 2.50 7415760 0.36 7415645 40114 2.25 3.1349CH 3.60 1150 20L22 053691 3.5500 7485 2.00 7441510 0.45 SA010240 ZN949E 300 8226 4.00 F01793 20.00 10.70MHz 1.50 40117 2.50 LM351P 5FF96364 4.25 7486 741578 0.42 741545 -1 4.00 7401520 0.45 0.50 500 26450E 750 24510 2.50 DS8830 1.40 0765A 13.00 40163 00 LM 377 3.00 51490 3.00 8228 4.50 11.00MHz 3.00 7489 74LS83A 0.70 7415668 0.90 7401532 25459CP 100 185030 2.00 DS8831 1.50 FD1797 2200 0.45 40173 1.20 LM3B0N-8 1.50 55760335 3.00 8243 2.60 12.00MHz 1.50 741585 0.75 7415669 40174 1.00 2911034E 2.00 1856030 DS8832 1.50 7490A 0.90 744L574 0.70 L3A3BON 1.20 SN76477 6.00 2.00 W02793 27.00 14.00MHz 1.75 40175 2641040 6.00 8250 9.50 7491 741586 0.35 7415670 1.80 74AL5138 1.50 1.00 LM380 1.50 5576989 4.00 74S188 1.80 058833 2.25 264134.1 23.00 8251A 3.25 WD2797127.00 1431MHz 1.60 7492A 741590 0.48 74LS682 2.50 74ALS139 40192 1.00 10030145 1.70 5674495 400 745287 DS8836 1.50 1.50 40193 1.00 254234E 9.50 82530-5 2.25 WD1691 15.00 14.756 2.50 140302 2.00 SN76660 111 3.50 Duu'Sp8838 7493A 741591 0.90 74L 6684 3.50 744L5244 4.00 40194 1.00 8703CJ 12.00 745288 1.80 2.25 WD2143 8.00 16393 317 SP0256AL2 7.00 82556C-5 3.80 15.00MHz 2.00 741592 0.35 74LS687 40244 1.50 745387 7494 3.50 74415245 4.75 LM384 2.20 TA7120 1.20 8256 2.25 MC1488 8:60 16.00MHz 2.00 40245 1.50 18.00 7495A 74L593 0.54 7415688 5.50 74015573 2.60 163865-I 00 747130 1.40 82523 1.50 ..RAC TER 40257 1.60 8256 24.00 MC1489 0.60 17.734 1.50 7415958 0.75 74LS783 21.00 L44387 2.70 TA7204 1.50 NE RAT 7496 74AL5574 4.50 40373 1.40 825123 ISO MC3446 :ai ORS 18.00MHz 130 100389 1.60 7A7205 0.90 8257C-5 4.00 2.50 7497 74L596 0.90 744L5580 2.60 40374 1.50 825129 1.75 745 LM391 100 747222 1.50 82590-5 4.00 MC3459 4.50 18.432MHZ1.50 7415107 0.40 SERIES 00095 74100 0.n 4043925 1.10 T47310 1.50 R032513UC 7.50 19.969MHz1.50 4005 SERIES 90097 8271 P.O.A. EE PROM MC33470 4.75 74107 7415109 0.40 0.75 1144393 0.65 R032513LC 7.00 3ßf:99 780231 1.20 8275 29.00 MC3480 8.50 20 000MH21.50 7415112 74500 0.50 4000 0.75 LM394CH 400 74109 0.45 0.20 784800 0.00 2816 -30 MC3486 2.25 5N745262AN 1.75 74502 0.50 4001 0.24 8279C-5 4.80 24.000MH2 74110 7415113 0.45 4 2Kx8 30.00 10.00 74504 0.50 0.25 VOLTAGE REAL TIME 8284 60 M C3487 2.25 48 000MHZ1.75 74111 7415114 0.45 4006 9306 256 bits MC4024 74505 0.50 0.70 REGULATORS CLOCK 8282 4.50 5.50 116MHz 2.50 74116 7415122 0.70 4007 (16616) 4.00 74508 0.50 on 8283 4. MC4044 650 P001000 12.00 74118 7415123 0.80 4008 060 MC6818P 4.00 74510 0.50 IA FIXED VOLTAGE PLASTIC 70220 74119 7415124 1.40 4009 0.45 M5817AN 9.90 74511 0.75 4010 0.60 +VE -VE LOW PROFILE SOCKETS BY TI WIRE WRAP SOCKETS BY TI 74120 7415125 0.50 V MSM5832RS 3.50 74520 0.50 4011 0.24 7805 045 7905 0.50 74121 7415126 0.50 4012 o.n 6V 7806 0.50 7906 0.50 74522 1.00 TELETEXT 8 p0 9p 18 po 16p 24 in 24p 8 pn 306 IB pin 24 pn 75p 74122 7415132 0.65 4013 0.36 DISPLAYS 7608 0.50 7908 050 50p 74530 128 7812 7912 DECODER M pn 10p 20 pin lap 28 PIP 14 p 42p 74123 7415133 0.50 0.50 4014 0.60 0.45 650 20 20 pin 66p 28 pin 1006 74532 0.60 4015 0.70 15V 7815 0.50 7915 0.50 16 pat 11p 22 pin 226 40 pn 300 16 pl 456 759 40 74125 74L5136 0.45 SAA5020 600 22 pin pn 130p 74537 0.60 4016 0 36 13V 7818 0.50 7910 650 74126 7415138 0.55 4017 0.55 2417824 0.50 7924 0.50 SAA5030 7.00 74538 0.75 4018 1.00 TURNED PIN 8 pin 14 pin 16 pin 18 pn 20 74128 7415139 0.55 060 FN0357 to FIXED VOLTAGE PLASTIC 1092 50.55041 16.00 pn 24 p 28 pin 40 Pin 74540 0.50 4019 LOW PROFILE SKTS. 74132 7415145 0.95 0.80 FN0500/ SAA5050 9.00 25p 32p 30p 40p 45p 55p 115p Sop 4020 5V 78105 79L05 74551 0.45 0.60 TIL730 1.00 0.30 51/ 0.45 74136 7415147 1.75 4021 6V 70.06 74564 0.45 0.60 0.30 12V 791_12 050 74141 7415148 1.40 4022 070 FND507/ BV 78L08 0.30 15V 79115 050 IP' 3A 74574 0.75 TRANSISTORS 350 2N1611 36p 256059 325p 1A400V 74142 7415151 0.815 4023 0.30 TIL729 1.00 2V 71112 0.30 iIP29C 4op 25p 74585 3.00 4024 041 sV 78115 0.30 2041711 36p 256107 65p IA 600V 3012 74143 7415152 2.00 MAN74/ 00161 2 45p BF 629 450 11P30A 35p 74586 1.00 4025 0.24 252102 70P 256247 190p 24 50V 3011 74144 7415153 0.65 DL704 1.00 BC10.' 8 I8p 51030 45p 71P30C 40p 745112 1.50 4026 060 OTHER 2 N2160 1500 256254 1300 24 100V 35p 74145 7415154 1.60 4027 0.40 MAN71/ 1311095 200 BF X84.5 Sop T173 A 40P 2N22196 745113 1.20 Sop 256290 850 24 400V 45p 74147 7415155 0.65 4028 080 DL707 1.00 REGULATORS BC 69C 1ßp BF X86,7 30p 1P31C 45p 2522224 30p 745114 1.20 4029 0.75 2SC1306 100p 3A200V 800 74148 7415156 0.65 MAN3640 1.75 Fixed Regulator. BC172 18p 51088 Sop TIP32A 45p 252369A 30p 745124 5.50 4030 0..15 2501307 1500 306008 72p 7415157 0.50 MAN4640 2.00 104309K 1A BC177 8 300 TIP32C 40p 74150 4031 1.25 5V 1.40 262484 30p 2SC1957 90p 44 100V 9Sp 745132 1.00 MAN6610 2.00 L632311 34 5V 3.50 BC179 30p TiP33A 70p 741514 74LS158 0.65 4032 1.o0 01050 3ßp 252646 SOp 2501539 1500 40400V 10op 745133 0.60 4033 781405NC 50 5V 5.40 OC182 J 11P3JC 74153 7415160 0.65 115 5585881 5.70 15p U751 2 Sop Bop 252904,5 30p 25C2028 800 745138 1.80 4034 2.50 78012 5A 12V 6.40 60 500 90p 74154 74L51614 0.75 TIL311 6.50 0E184 í6p BFY56 330 T1P344 90p 2N29060 30p 2SC2029 4035 0.70 78705 10A 5144 9.00 200o 60100V 1009 74L51624 745139 1.80 TIL729 1.00 BC187 30p 717345 120p 74155 0.75 4036 2.50 VARIABLE REGULATORS 81090 90p 2 62907 Sop 2502078 1600 66400V 120p 745140 1.00 LM305AH BC212 J 16p 74156 74L51634 0.75 4037 1.10 TIL730 1.00 2.50 80739 450 71P35A 1200 2N2926 12p 2SC2335 200V 11.43171 1044000 200p 7415164 0.75 745151 1.Sß 1.00 61458910 1.50 70.220 50 BC214 16p 85019,20 300 71P35C 253053 360 74157 LM317K 1400 25C2612 200p 2544008 400p 745153 1.50 4039 2.50 003 240 KU 37 16p 74159 74151654 1.10 MAN8940 2.50 LM337T 0E1104 225p 11P36A 14op 253054 Epp 31.128 200p 745157 2.10 4040 0.60 2.25 C32 16p TRIALS 74160 74151664 1.50 LM3507 10A+VAR 4.00 BU105 1900 T1P36C 150p 253055 550 35140 200p 745158 2.00 4041 0.55 BC331 16p PLASTIC 74161 7415168 1.30 4042 0.50 1M396K 100+VAR 15.00 BÚ108 2500 71741 A Sop 253442 1400 35141 200p DISPLAY I 147236 745163 4.00 40444 0.50 BC3.38 18p 80109 225p 11715 74162 7415169 1.00 0.60 78HH050C 550 253553 240p 35201 2007 745169 7.00 0< 0.80 DRIVERS SA 5V 5.75 BC461 40p 80126 1500 34400V 000 7415170 1.40 7814GKC 11P42A 60p 253584 2500 35204 200p 74163 4015 1.00 541-VAR 6.50 6A40UV 70p 745174 3.00 78GUIC 10+VAR BC4%7.8 36P T1P42C 850 40290 2500 74164 74151734 1.00 4046 0.60 2.25 253643,4 46p 64500V 745175 9368 4.50 79HGKC BC516 7 50p 85205 200p 71354 2N3702/3 BBp 74165 7415174 0.75 3.20 1047 0.60 54-VAR 6.75 1800 259 40361.2 75p 9370 4.50 79GUIC IA-vAR BC547B 200 84400V 75p 7415175 745188 1.80 4040 0.55 2.50 BU208 200p TIP55 180p 253704/S 250 40595 12Op 74166 0.75 LM39I4 3.50 SWITCHING REGULATORS BC548C tep 64500V 95p 745189 2.25 4049 0.36 Hunos 145p TIP120 75p 253706/7 259 40673 gap 74167 7415181 2.00 ICL 7680 2.50 BC549C 160 12Á400V 85p 745194 3.00 4050 0.35 1,053915 3.50 BUX80 6000 TIP121 75p 253708 25p 40871,2 100P 74170 7416183 1.90 4051 065 5G3524 3.00 110 124500V 105p 745195 3.00 LM3916 3.50 TL194 BC5578 BUV69C 350p TIP122 80p 7415190 4052 3.00 253773 200p 164400V 74172 0.75 0.60 UDN6118 3.20 BC559C 24p E310 TIP125 220p 745196 3.50 4053 0.60 TL497 3.00 50p 75p 253819 40p DIODES 74173 74L5191 0.75 UDN6184 3.20 78540 BC 770 30P 164500V 130p 745200 4.50 4054 0.60 2.50 MJ41J 2500 TIP12/5 80p 2143823 Sop 7415192 0.80 RC4195 72800 130p 74174 4055 0.80 ULN2003 0.90 1.50 BC V71 360 MJ802 400p TIP142 1200 BY127 120 745201 3.20 253866 907 7152060 74175 7415193 0.80 4056 0.55 ULN2004 0.90 BO! II 75p MJ2501 225p TIP 147 120p BYX36300 20p 80p 745225 5.20 OPTO -ISOLATO RS 11C226D 74176 74151940 0.75 4059 1.00 0192068 2.90 BD. 32 800 MJ2955 90p 7172955 9Sp 0447 10p 75p 745240 4.00 4080 2143904 22p 74178 74151950 0.75 0.70 130125 401, MJ3001 t11246D 1100 4063 ULN2802 1.90 ILD74 1.30 TILI11 0.70 225p TIP3055 lop 253906 22p 0690/91 9p 745241 4.00 0.65 39 74179 7415196 0.80 4066 0152803 1.80 11074 2.20 BD, 40p MJ4502 400p 11593 30p OÁ95 9p 745244 5.00 0.40 TIL112 0.70 254036 650 THYRISTORS 74180 7415197 0.80 4067 2.30 MCT26 1.00 B5140 409 MJE340 80p VN10K1r1 SOp 04200 9p 745251 2.50 LR N2804 1.90 TIL113 0.70 254037 65p 74181 7415221 1.00 4068 0.25 BD189 600 MJE2955 150p VN66AF 90p OÁ202 10p 745257 75491 0.70 MCS2400 1.90 TILT16 0.70 2144123 4 27p 74LS240 0.80 2.50 4069 0.24 BD2J2, 130p MJE3055 120p AF 1N914 4p 10400V 45p 74182 75492 0.70 MOC3020 1.50 6N137 3.60 V508 El 54125.6 27p 74L5241 0.60 745258 2.50 4070 0.24 80233 75p MPF102 1N916 7p 84600V 180p 74184 4071 0.24 6N139 1.75 40p ZTX108 1Sp 254401 3 250 745260 1.00 052 15 85p 124400V 160p 74185A 74LS242 0.90 4072 0.24 MPF103,4 40P IT X300 18p 254427 90p 154148 4p 745261 3.00 OTHERS 130241 164100V 180p 74190 74LS243 0.90 4073 0.24 LEDS flop MPG 105 /op Zi%452 45p 254871 Sop 15400112 5p 745283 4075 0.24 55242 800 164400V 180p 74191 74LS244 0.80 2.70 2205777 0.50 MPSA06 300 ZrX500 20o 255087 27p 164003/4 60 4076 0.65 C106D 45p 7415245 745287 2.25 0.125" 0.2" BD.379 9ßp MPSA12 50p ZTX502 20o 1N4005 011 74192 1.00 4077 0.25 BP%25 1.80 2N5089 27p 745288 2.00 RED TIL209 0.12 05380 Bop MPSA13 1N4006/7 7p MCR101 38p 74193 7415247 1.10 4078 On BPW21 280 TIL220 0.15 SOp Z1 X504 22P 2515172 27p 171211 05677 400 155401/2 253525 130p 74194 7415248 1.10 745289 2.25 4081 0.24 OCP71 180 GRN 0.19 TIL222 0.18 MPSA20 50p IT X552 55p 255191 90p 120 YEL 131244 40p 1 254444 180p 7415249 1.10 745299 5.50 4082 0.25 TIL 212 0.20 TIL226 0.22 MPSA42 SOP IT X652 60p 255245 40p N5403/4 14p 74195 o.w ORP12 1.20 012565 50p 255060 309 7415251 745373 4.00 Sect LEDs MPSA43 50p ZTX752 lop 255401 60p 155400/S 140 74196 0.75 0.75 ORP60 1.20 255061 32p 745374 4.00 (R /Gat) 0.30 BF257/8 lop MPSA56 30p 25697 35p 255459 155404/7 19p 74197 7415253 0.75 4089 1.20 ORP61 1.20 COUNTERS 300 255064 33p 745387 COD (BI Colour) 01337 36p MPSA70 506 25698 450 15920 9p 74198 7415256 0.90 2.25 035 SFH205 1.00 255460 60p Ó9' 690 1.00 01039 320 MPSA93 40p :N71)64 360 74199 7415245700.70 11132 74C925 8.50 25515 45p /FIVERS 0.55 BF040 1 32p BRIDGE 4095 0.90 10 LED 74C926 MPSLJ06 83p 25708 380 255875 2500 7474221 74L52584 0.70 4096 0.90 11/78 0.55 8.50 01079 320 MPSU07 RECTIFIERS BarGraph: 74C928 80p 25918 45p 255883 375p 27V33V 74251 7415259 1.20 4097 270 TIL 318 1.20 6.50 BFR80 1 320 MPSU45 Red 2.25 7216B 90p 2N930 30p 256021 30p IA 500 199 400mW 9p 74259 7415260 0.75 4098 0.75 TIL 81 110 22.00 BF096 180p MPSU65 78p 4099 0.90 Grat 2.25 251131, 50V 256052 300p 141000 20p 1W 74265 7415261 1.20 TIL 100 0.75 ZN1040 8.70 15p 4501 0.36

PLEASE ADD 50p p &p & 1507o VAT TECHNOMATIC LTD (Export: oo VAT, p&p a Cost) MAIL ORDERS TO: 17 BURNLEY ROAD, LONDON NW 101ED Orders from Government Depts. & Colleges etc. welcome.

SHOPS AT: 17 BURNLEY ROAD. LONDON NW10 1119111191:1 Detailed Price List on request. 1,13.4 (Tel: 01 208 1 177 4 lines) Telex: 922800 Stock items are normally by return of post. l 305 EDGWARE ROAD. W2 (` LONDON - Minimum Telephone Order £5 CIRCLE 89 FOR FURTHER DETAILS.

ELECTRONICS & WIRELESS WORLD JUNE 1985 27

www.americanradiohistory.com TESTINSTRUMENTS

A wide range of high performance instruments that put professional test capability on your bench. COUNTERS - TF600 5Hz to 600MHz TF200 10Hz to 200MH/ TF040 10Hz to 40MHz PFM200A 20Hz to 200MHz (nand Held model) TP600 prescaies to 600MHz TP1000 orescales to 1000MHz

MULTIMETERS TM351 01 °.o 3' digit LCD TM356 0 25 °'o 3' : digit LCD TM355 0 25% 3' 2 digit LED TM354 0 75 °o 3' . digit LCD (nand -neld model) TM451 003 °Po 4' 2 digit LCD witn autoranging and sample Hold TM452 005° o 41? digit LCD with built -in frequency counter (handheld model)

OSCILLOSCOPE - SC110A 10MHz 10mV sensitivity 40mm CRT wrh 6mm grahcule divisions

THERMOMETERS TH301 -50 °C to -750 °C 1 resolution TH302 -40 °C io +1100°C and -40 °F to +2000 °F 01° and 1° resolution Both accept any type K thermocouple.

GENERATORS - TG101 002Hz to 200kHz Function Generator TG102 0 2Hz to 2MHz Function Generator TG105 5Hz to 5MHz Pulse Generator TG501 0005Hz to 5MHz Function Generator TG502 0005Hz to 5MHz Sweep Function Generator TG503 0005Hz to 5MHz Pulse Function Generator LOGIC ANALYSERS - TA2080 8 channel 20MHz TA2160 16 channel 20MHz ACCESSORIES Bench rack test leads carrying cases mans adaptors rot -.es 'ne -nog 6uple probes microprocessor disassembly options

For turner information contact Thandar Electronics Ltd London Road St Ives Huntingdon. Cambs PE17 4HJ Telephone (0480) 64646 Telex 32250 2\vi thandor ELECTRONICS LIMITED CIRCLE 57 FOR FURTHER DETAILS.

NEW NEW NEW NEW NEW NEW NEW NEW FOR QUYS/ALITMAILCOMPONENT BY ORDER // l 'ELECT RCVAILLIEj

83000 SUB -ASSEMBLY The 83000 is a single board micro -computer with an alphanumeric display and keyboard. It is based on an 8085 microprocessor and is ideal for control applications requiring up to 26 input /outputs. Opto- isolation of the inputs is provided and there is a 14 bit timer on board. Software utilities are available for operating the display FREE POSTAGE and keyboard, initialising the system and performing self FREE GOOD DISCOUNTS tests. Applications include:- 44 PAGE GOOD SERVICE * Remote Intelligent Display PRICED AND THOUSANDS OF * Password Security Applications ILLUSTRATED STOCK ITEMS PHONE YOUR ORDER * Small System Process Control CATALOGUE ACCESS OR * Watchdog Monitoring ON REQUEST BARCLAYCARD * Printer Interface 000 Automation ELECTROVALUE LTD 28 St. Jude's Road, Engletield Green. Egham, and Control Surrey TW20 OHB Phone Egham (0784) 33603. Telex 264475 O O O North Branch, 680 Burnage Lane, Manchester M19 1NA O O Technology 432 4945 Phone 061 March Barton, Exeter EX2 8QW. Tel: 37190. C Please mention this publication when replying Cotton Road, NEW NEW NEW NEW NEW NEW NEW NEW_ CIRCLE 51 FOR FURTHER DETAILS. CIRCLE 72 FOR FURTHER DETAILS.

28 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com CIRCUIT IDEAS

Automatic Inverter inverter switch RLA1 s& ptY -2-RLA o Electrical appliances such a as 240V load blender or sewing machine RL A2 require power intermittently and when run from an inverter, power consumption of the idling s inverter can exceed consumption of the appliance. r 12V This circuit automatically gInverter switches on the inverter a 1k8 3k9 1N4007 vi when output 100p RLB1 load is connected, and removes winding 7 the need for remote switching 6 741 BC639 when the power is to be 3 distributed. 500 15 BC ©2N3055 When a load is connected, it 639 takes the lower contact of the c2 68n 10p 10k 500 second relay, and therefore the 2x 3A 400V comparator inverting input via 3A 400V R1, to ground. The first relay is CV energized by the comparator output being high and power is delivered to the inverter and the disconnected, the leftmost chatter during switch on and speed or half-power operation. coil of the second relay. transistor turns off and allows off. The first relay only has to If the anode of the appliance With the second relay the comparator inverting input be large enough to switch the diode is connected to R1, the energized, the load is connected to go high, removing power inverter in its idling state; the load will not be sensed. to the inverter -transformer from the first relay coil and second relay connects the load Heat sinking for the parallel output winding through the therefore disconnecting the at 230V and the first relay does diodes and power transistor parallel- connected diodes. inverter input. Standby current not open until the load is should be isolated from earth Voltage drop over these diodes is around 12mA. disconnected. and all connections to the keeps the left -most transistor The power -transistor emitter A changeover switch is inverter should be insulated for switched on and therefore the diode ensures that the included to change the inverter safety. comparator inverting input transistor switches off when the output phase since some Nicholas Butt remains low. comparator output goes low. appliances place a diode in Glemsford When the load is Capacitors C1.2 stop relay series with the load for half- Suffolk Lower -noise

+ 5V oscillator 10 ACK Standard two -gate oscillators 13 3 Z 4k7 generate noise spikes around IQ 15 r CLR 1RC the zero -crossing point. This BUSY 8 cheap circuit using a 4001/4011 < 2 1c type i.c. provides a much 1n cleaner output +sV1 1A which is also 18 3 Centronics STR 2 Dip TBRL TRE buffered. Further, the oscillator 74221 interface 26 TBR1 may be gated on and off using NO one of the inputs shown 74L508 strapped together. 01-R 74LS24S u:art_ from I have used more expensive Zk2 printer 4093 i.cs for similar applications but I found that 4V7 11 32 they had a higher failure rate. EN TBR7 I.J. Eamus Ampro Enterprises Aylesbury Buckinghamshire

Centronics -to- we added a buffer to protect its acknowledge pulse of inputs when power is on and approximately 51.i.s. The original RS232 converter the link is disconnected. The monostable circuit gave a pulse computer needs to stop sending of approximately 25ms so we y We have made one or two data when a serial printer buffer replaced it with a t.t.l. modifications to Burd's is full so we added an And gate monostable i.c. excellent idea for producing to combine the data -terminal John Wike and Dave Pinch serial output from a Centronics ready signal from the printer South Wales Radio Therapy and printer interface, described in with the uart THE signal. Oncology Service NO. 0°Output the February issue. Finally, the Centronics Velindre Hospital As the uart is a cmos device, standard specifies an Cardiff ELECTRONICS & WIRELESS WORLD JUNE 1985 29

www.americanradiohistory.com CIRCUIT IDEAS

d -to -a converter most - Fast converter for significant input through an Or Two i.c. shortwave calibrator inputs are low. repetitive signals gate; all other Inexpensive portable shortwave many cases. To obtain a sample, the receivers are often quite This circuit uses two c -mos is pulsed. Its leading strobe line sensitive but have vague dial i.cs to generate a modulated digital edge clocks bistable device IC,d Flash analogue -to- markings, making tuning calibration signal at switch - -hold And gate, and the converters and sample- and through the difficult. Lack of a b.f.o. selectable frequencies of output state circuits are widely used for comparator precludes use of a conventional 1O0kHz or 1MHz. The signal is but appears at the output of IC,d. sampling analogue data, crystal calibrator since its audible as a distinctive tone trailing edge when the input signal is The strobe signal signals would be inaudible in when the receiver is tuned to repetitive, there is a good case clocks the two -bit counter, for using a successive making Qo and Q, outputs of an decoder low and high approximation technique - the 22k effective sampling rate as good respectively. Thus if the input as for flash converters is signal was greater than the possible at a fraction of the most significant bit when the 0 9k1 outpu cost. Speed of this circuit is strobe leading edge occurred, 4049 (couple loosely to only limited by the comparator output of IC,d will be high, 9k1 aerial of receiver) and acquisition time of the D- otherwise it will be low. Optional signals must be un modulated type bistable devices of IC,. Four strobe 10M output Commercial a -to -d converters applied at the same point in 1MHz / single -chip i.cs and successive signal repetitions, are usually -_ 12,101MHz allowing enough time for the 1MHz 5-60p the time taken for each CARRY approximation is not externally converter to settle between CK 4017 controllable, so discrete each one. When four strobe 14 This have been applied, data RESET ENABLE, components are used. signals 330p 1T330p circuit is for four -bit con- can be read at outputs A to D, 115 113 version, but expansion to six or the reset signal applied, and the eight bits is relatively easy. sequence restarted at a different When the reset line is pulsed, point in the signal cycle. Device 9V 11 +16 outputs of the bistable elements types depend on the application 1. 40n 4049 i40 4017 and the two -bit counter are and resolution required. t8 cleared. The one -of -four T. Hunter T ÌB decoder Qa output becomes Doncaster high. This signal is sent to the South Yorkshire

Signal in o

Comparator 0 Q3 Q CK

R IC30

IC1b 0 I03b Q1 Q CK 01

d -to o IC3c CK converter Two 02 -bit Analogue counter output IC3d D Qo o CK --B- R

IC1d 0

Q CK

R

0 0 0 o o I.s.b A -+D m.s.b Reset Strobe Output

30 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com CIRCUIT IDEAS

Trip for power switches Overcurrent protection for switching power transistors is provided by this simple add -on circuit. Emitter current is monitored by R2 and the comparator. At the trip current, the p-n -p transistor turns on and shunts the base drive away through R2 to provide positive n,6ÌlÍIÏt!tllif feedback. The stage remains disabled until the drive is removed, which is useful for p.w.m. systems. any multiple of the calibration The comparator is an open - frequency. collector one. Base -drive R, must exceed the fall over R2. MJ11030 transistors at 50A, The last inverter stage - current multiplied by R2 should A safe rule is to let the normal 339 comparators and 2N3703 actually a linear operational be around 250mV and base - excess drive, shunted through p-n -p transistors, Vref was amplifier fed by a summing emitter voltage of the output R replace the drop across R2 100mV and was shared between network - functions as a Darlington should be at least before the transistor comes out several stages. Resistor R was modulator. The output 900mV; if not add a resistor or of saturation at the trip current. about 2Q and R2only 2 mQ. diode. waveform is somewhat odd - To ensure that the Typically, this makes R2 quite D.H. Potter looking (see photograph) but comparator circuit switches small. Axminster definitely amplitude modulated. right over, the rise in voltage of As an example using Devon Modulation can be adjusted by varying one or both of the diodes. If only one display is 9.1kQ resistors. needed it also saves two i.cs. Adapting for M. Covington The 4011 detects inputs Athens greater than nine and double -sided Georgia illuminates the second digit. USA drives The same signal causes six to be added to the 4008 adder Microcomputers designed to Easy to read input. The result always has an select independent single -sided overflow of 16, with the effect disc drives can be interfaced hex. display that 10 is actually subtracted, with double -sided drives using leaving a number between zero this small modification which Onlug's circuit for displaying and five which can still be makes the drive's second side hexadecimal numbers in decoded by the 4511 i.c. appear as an independent drive decimal form (Dec. 1984) can John Cook to the computer. To do this, a be simplified. This circuit does Ipswich drive- select signal forms the the same job, but saves 14 Suffolk side -select signal. The circuit, which may be installed in the microcomputer or in any of the drives, relies on drive and side - select signals being open -collector sourced; check this before installing. Using signals shown, DSO selects the first side of the drive and DS1 the second side. Which drive- select signals are used will depend on the logical position required for the drive. Decouple the 7417 close to the supply pins and connect all unused inputs to the positive rail through a common 1kQ resistor. In many drives, supply, ground and signal lines will be available at dil sockets. Pin numbers shown are for a standard 5'/4in drive interface (further details in the article Floppy discs on pages 44/45 of the January issue). David March London

ELECTRONICS & WIRELESS WORLD JUNE 1985 31

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SN76660N 0.60 T8A5200 1.10 TDA2524 1.95 INTEGRATED CIRCUITS STK014 7.95 TBA530 1.10 TDA2530 1.95 TDA2532 1.95 STK015 5.95 TBA5300 1.10 AN124 2.50 0.95 TDA2540 1.95 MC1327 STK043 TBA540 1.25 AN2140 2.50 0.95 9.50 TBA5400 1.35 TDA2541 2.15 NEW BRANDED CATHODE MC13270 STK415 7.95 AN240P 2.90 1.20 TBA5500 1.95 TDA2560 2.15 MC1349P STK433 5.95 AN612 2.15 MC1351P 1.50 TBA560C 1.45 TDA2571 3.50 PLEASE ALLOW ADDITIONAL £3 AN7140 3.50 STK435 7.95 MC1351P 1.50 TBA560C 1.45 TDA2581 2.25 PER TUBE FOR CARRIAGE. AN7145 3.50 MC1357 2.35 STK437 7.95 TBA560C0 1.45 TDA2593 215 RAY TUBES AN7150 2.95 MC1358 1.58 STK439 7.95 TBA570 1.00 TDA2600 5.50 8A521 3.35 MC1495 3.00 STK461 11.50 TBA641011212.50 TDA2610 2.50 A1865/20 85.00 F31-10GM 65.00 CA1352E 1.75 MC1496 1.25 TA7061AP 3.95 TBA651 R 2.50 TDA2611A 1.95 AW36.11 25.00 F31-10GR 65.00 M50-120GV 69.00 CA3086 0.46 MC145106P7.95 TA7108P 1.50 TBA720A 2.45 TDA2640 3.50 CME822W 19.00 F31-10LC 65.00 M50-120LC 65.00 CA3123E 11.50 MC1723 0.50 TA7120P 1.65 TBA7500 2.65 T0A2680A 2.75 CME822GH 25.00 F31.10LD 65.00 M61-120LC 75.00 6776016 2.50 MC3357 2.75 TA7130P 1.50 TBA800 0.09 TDA2690 2.45 CME1428GH 45.00 F31-12LC 65.00 M61-120W 75.00 HA1377 3.50 M123161 175 TA7176AP 2.95 TBA810AS 1.85 TDA3310 2.95 CME1428W 39.00 F31-12LD 85.00 S6AB 45.00 HA1156W 1.50 ML23213 2.50 747203 2.95 TBA810P 1.85 TDA3560 5.50 CME1523GA 39.00 F31-13GR 65.00 SE4/D/P7 45.00 HA1339A 2.95 MSM5807 6.75 TA7204P 2.15 TBA820M 0.75 UPC566H 2.95 CME1523W 39.00 F31.13LD 85.00 SE42BP31AL 55.00 HA1551 215 PLL02A 5.75 TA7205AP 1.15 TBA8200 1.45 UPC575C2 2.75 CME1431 GH 39.00 F31-13LG 85.00 SE42BP31 55.00 LA1230 1.15 SAA500A 3.50 TA7222AP 1.80 TBA890 2.50 UPC1025H 1.95 CME1431W 39.00 F41 -123LC 160.00 SE52AP31AL 55.00 LA4031P 1.95 SAA1025 7.25 TA7227P 4.25 TBA920 1.85 UPC1028H 1.95 CME202GH 45.00 F41-141LG 180.00 SE5FP31 55.00 LA4102 2.95 SAA5010 6.35 TA7310P 1.00 TBA95092X2.35 UPC1032H 1.50 CME2024W 45.00 F41 -1421C 185.00 T937 65.00 LA4140 2.95 SAS560S 1.75 TA7313AP 2.95 TBA990 1.49 UPC1156H 2.75 CME2325W 45.00 M7-120W 19.00 T948N 65.00 LA4400 4.15 SAS570S 1.75 747321P 2.25 TCA270 1.10 UPC1158H 0.75 CME3126GH 45.00 M14-1000M 45.00 T948H 65.00 LM420 1.95 SAS580 2.85 TA7609P 3.95 TCA270S0 1.10 UPC1167C2 1.15 CME3128GH 45.00 M14-100KA 55.00 V3191 59.00 LA4422 2.50 SL901B 4.00 747611 AP 2.96 TCA650 3.50 UPC1181H 1.25 CME3128W 45.00 M14-100LC 45.00 V4150LC 55.00 175.00 LA4430 2.50 SL917B 6.95 TAA310A 2.50 TCA940 1.85 UPC1182H 215 CME3132GH 45.00 M17-151 GVR V42548 65.00 LA4461 3.95 SL1310 1.90 7443204 1.95 704440 2.20 UPC1185H 3.95 CME3155W 45.00 M17-151GR 175.00 V4274GH 65.00 LC7120 3.25 SL1327 1.10 T4A350A 1.95 TDA1001 1.95 UPC1191V 1.50 CRE1400 25.00 M19-100GY 55.00 V4283W 65.00 45.00 LC7130 3.50 S113270 1.10 744550 0.35 TDA1004A 4.15 UPC1350C 2.95 CV429 89.00 M19-100W V5002LD 65.00 55.00 LC7131 5.50 SN76003N 115 TAA570 1.95 TDA1006A 2.50 UPC1353C 2.45 CV1450 35.00 M19-101GR V5004GR 59.00 55.00 LC7137 5.50 SN76013N 115 TAA661 B 1.20 TDA1010 2.15 UPC1365C 3.95 CV1526 19.00 M19-103W V5004LD 59.00 LM324N 0.45 SN76023N 2.75 T4A700 1.70 TOA1035 2.50 UPC2002H 1.95 CV2185 15.00 M23-110GH 55.00 V6001GH 55.00 LM380N8 1.50 SN76033N 3.50 TBA120AS/B/C/ TDA1037 1.95 555 0.35 CV2191 19.00 M23-111W 55.00 V6006GH 85.00 55.00 LM380N14 1.75 SN76110N 0.59 SA/SB/T/U 1.00 TDA1170 1.95 556 0.42 CV2193 15.00 M23-111GH V6007DP31 59.00 LM383T 2.95 SN76115N 1.25 TDA1190 2.15 723 0.50 CV5119 85.00 M23-1111D 55.00 V6007GW 85.00 LM3900N 3.50 SN76131N 1.30 TBA395 1.50 TDA12700 3.95 741 0.35 CV5320 85.00 M23-112GM 55.00 V6008GW 59.00 M51513L 2.30 SN76226DN 295 TBA396 0.75 TDA1327 1.70 747 0.50 CVX389 55.00 M23-112GV 55.00 V6008W 65.00 M51515L 215 SN76227N 1.05 TBA440N 2.55 TDA2002 1.95 748 0.35 D9-110GH 39.50 M23-112GW 55.00 V6034WA 59.00 M51521L 160 SN76533N 116 TBA4800 1.25 TDA2020 2.95 7805 0.65 D9-120 45.00 M23-112KA 55.00 V6048CLA 59.00 MB3712 2.00 SN76544N 2.65 TBA510 2.50 TDA2030 2.80 7808 0.60 D10-210tH 45.00 M23-112LD 55.00 V6048F 55.00 MC1307P 1.00 SN76570N 1.00 TBA5100 2.50 7042522 1.95 7815 0.95 D10-210GH68B 65.00 M23-112W 55.00 V6048J 49.00 MC1310P 1.50 SN76650N 1.15 TBA520 1.10 TDA2523 2.95 D10-210G H72 65.00 M24-1200M 59.00 V6052GH 65.00 M24-120GR 59.00 BD204 0.70 D10-230tH 3500 V6052GR 65.00 BFR40 0.23 RCA16335 010 M24-120LC 59.00 SEMICONDUCTORS 8D222 0.48 SKE5F 1.45 D10-230GM 35.00 V60646LA 65.00 BFR81 0.25 010-2930Y/90 55.00 M24-120WAR 59.00 V60648P31 55.00 BD223 0.59 BFR88 0.30 TIM 0.40 M24-121GH 55.00 AC126 0.45 0.09 BD225 0.48 TIP29C 0.42 D13-30GH 49.50 V6064CLA 55.00 BC174A BFR90 1.50 M24-1211C 59.00 V6069GH 55.00 AC127 0.20 0.15 BC232 0.35 TIP3DC 0.43 D13-33GM 49.00 BC177 BF R91 1.75 M24-121 WA 59.00 V6070P31 AC128 0.28 0.15 BD233 0.35 TIP31C 0.55 D1347GH/26 5500 49.00 BC178 BFT42 0.35 M28-12GH 55.00 V7016A 85.00 AC128K 0.32 BC182 0.10 BD234 0.35 TIP32C 0.42 D13-47GH/34 55.00 BFT43 0.35 85.00 M28-12LC 55.00 59.00 AC141 0.28 0.10 80236 0.49 TIP33B 0.95 D13-51GL/26 87030 BC782LB BFW92 0.95 M28-131C 49.00 59.00 AC14/K 0.34 0.10 BD237 0.40 T1P34B 0.95 D13-51 GM/26 85.00 V7031GH BC183 BFX29 0.30 55.00 M28-131G 49.00 V7031/67A 59.00 AC142rK 0.30 0.09, B0738 0.40 TIP41A 0.45 0134500H/01 BC183L BFX84 0.26 D13471GH/26 55.00 M28-13GR 49.00 V7035A 49.00 AC176' 0.22 BC184LB 0.09 BD242 0.85 BFX85 0.32 T1P41C 0.45 M28-131GR 55.00 AC176K 0.31 0.10 80246 0.75 TIP42C 0.47 D13-550GH 65.00 V7037GH 45.00 BC204 BFX86 0.30 M28-132GM 55.00 V8004GR 65.00 AC187 0.25 BC207B 0.13, BD376 0.32 T1P47 0.65 D13-6000M 59.00 BFX88 0.25 59.00 M28-133G4 55.00 V8006GH 65.00 AC187K 0.28 0.13. BD410 0.65 TIP120 0.80 D13-61DGH BC208B BFY50 0.21 59.00 M31-100GH 55.00 V8010A 95.00 AC188 0.25 BC212 0.09, B0434 0.65 TIP125 0.85 D13-610GM BFY51 0.21 59.00 M31-101 GH 55.00 2BP1 9.00 AC188K 0.37 BC212L 0.09, B0437 0.75 TIP142 1.75 D13-611 GH BFY52 0.25 D13-6110M 59.00 M31-182GR 55.00 38P1 13.50 40142 0.79 BC212LA 0.09 BD438 0.75 BFY90 0.77 TIP161 2.95 53.00 0.65 013-630GH 59.00 M31-182GV 4EP1 30.00 40143 0.82 BC213 0.09 D520 BLY48 1.75 TIP2955 0.80 M31 -183W 55.00 D538 0.65 D14-120GH08 65.00 3WP1 18.50 AD149 0.70 BC213L 0.09 gg TIP3055 0.55 M31 -184W 65.00 014-150GH 75.00 3 H/OBM 55.00 AD161 0.39 BC214 0.09 D597 0.95 BR1ÓÓ TIS91 0.20 M31-184GH 65.00 1.25 Ó D14-150GM 75.00 58P1 9.00 AD162 0.39 BC214C 0.09 D701 BR101 0.49 TV106/2 1.50 M31-1841,31 85.00 1.25 D14.172GH/84 59.00 58HP1 30.00 AD161 /2 0.90 BC214L 0.09 Q702 BR103 0.55 241308 1.35 M31-185GH/VR 89.00 D 14-172GR 55.00 5BHP1FF 30.00 AF106 0.50 BC237B 0.09 6707 0.90 BRC4443 1.15 2N2219 0.28 89.00 D14-172GV 55.00 M31-186W 58HP31 30.00 AF114 1.95 BC238 0.09 DX32 1.50 BT100A/0210.85 2N2905 0.40 55.00 O 14-17304 55.00 M31-19004 5CP1 10.00 AF121 0.60 BC239 0.12 137106 2N3053 0.40 1.49 014-173GM 53.00 M31-190GR 55.00 6EP7/S 39.00 AF124 0.65 BC251A 0.12 F115 0.35 gg77116 1.20 2N3054 0.59 55.00 D14-173GR 55.00 M31-19014 130P1 13.50 AF125 0.35 BC252A 0.15 F119 0.55 8Ti19 3.15 2N3055 0.52 59.00 D 14-18104/62 65.00 M31-190W 138P4 17.50 AF126 0.32 BC258 0.25 F127 0.39 BT120 1.65 2N3702 0.12 59.00 0.20 014-1810H/98 65.00 M31-191 GH 17DWP4 25.00 AF127 0.65 BC258A 0.39 F154 BU105 1.95 2N3703 0.12 M31-191 GR 59.00 AF139 0.40 BC284 0.30 F158 0.22 014-181GJ 55.00 32J/1085 99.00 BU108 1.69 2N3704 0.12 M31-191GV 55.00 88D/89B/89D/89L 15.00 0.60 BC300 0.30 F160 0.27 1.25 O14-181GM 53.00 AF150 BU124 2143705 0.12 M31-191W 59.00 1273 39.00 AF178 1.95 BC301 0.30 F167 0.27 BU125 1.25 0.12 D14-181G M50 59.00 2N3706 59.00 M31-192W 59.00 1564 39.00 AF239 0.42 BC303 028 F173 0.22 BU126 1.60 0.12 O 14-182GH 2M3708 65.00 M31-195GH 59.00 1844 45.00 AU106 4.54 BC307B 0.09 F177 0.38 130204 1.55 2N3733 9.50 D14-182G M/98 M31-210GH 59.00 BC327 0.10 F178 0.26 014.2008E 89.00 9442E1 80.00 AU1O7 150 BU205 1.30 2N3773 2.75 M31-220W 59.00 95447GM 75.00 AU110 BC328 0.10 F179 0.34 D14-20004/50 85.00 3.50 BU208 1.39 2N3792 1.35 M31-270GV 65.00 95449GM 75.00 BC107A 0.11 BC337 0.10 F180 0.29 BU208A 1.52 O 14-2000M 75.00 2N4427 1.95 75.00 M31-271P31 65.00 7709631 78.50 BC1078 0.11 BC338 0.09 F181 0.29 BU208D 1.95 D14-210GH M31-2710W 85.00 BC347A 0.13 F182 0.29 2144444 1.15 D14-270GH/50 75.00 BC108 0.10 BU326 1.20 0.42 M31-271W 65.00 BC461 0.35 F183 029 2N5294 D14-310W 110.00 BC108A 0.11 BU407 1.24 0.48 M36-12W 75`00 TAPE HEADS BC478 0.20 F184 028 2N5296 014-320GH 85.00 BC108B 0.12 BU500 2.25 0.60 M36-141 LA 75.00 MONO HEAD 1.50 BC527 020 F185 0.28 2N5298 85.00 BC109 0.10 BU508A 1.95 0.45 014-3200H/82 M36-141LG 76.00 AUTO REVERSE 3.50 0.10 F194 0.11 2N5485 45.00 BC1098 0.12 BC547 BU526 1.90 D14-340GH/KM 75.00 STEREO HEAD 2.95 0.11 2N5496 0.95 45.00 M36-141W BC109C 0.12 BC548 0.10 F195 BU801Y 2.25 254715 0.80 014-340KA 75.00 0.10 F196 0.11 65.00 M36-170LG BC114 0.11 BC549A BUY698 1.70 2SC495 0.80 D 16-100GH M38-100GR 65.80 0.14 F197 0.11 69.00 ELECTRO -OPTICAL BC116A 0.15 BC550 MJ3000 1.98 2SC496 0.80 D16-100GH/65 M38-101G4 65.00 BC557 0.08 F198 0.16 D16-100GH/67 65.00 BC117 0.19 MJE340 0.40 2SC1096 060 M38-103GR 65.00 9524H 25.00 BC557B 0.08 F199 0.14 D16-100GH67A 75.00 BC119 0.24 MJE520 0.48 2SC1106 2.50 9677M 22.00 BC558 0.10 F200 0.40 D16-1000H/79 89.00 M38-120W 65.00 BC125 0.25 MPSA13 0.29 2SC1172Y 2.20 P4231BAM 19.00 BC139 0.20 BCY33A 1.60 F241 0.15 016-100GH/794 75.00 M38-120WA 95.00 MPSA92 0.30 2SC1173 1.15 BD115 0.30 F245 0.30 D16-10001197 65.00 M38-121GR 85.00 BC140 0.31 MRF237 4.95 1.00 2SC1306 89.00 M38-121 GHR 85.00 WIREWOUND RESISTORS BC141 0.25 F257 0.26 MRF,30A 13.95 2SC1307 1.50 O 18-160GH 0.59 F258 0.28 65.00 M38-121 LA 85.00 BC142 021 BD124P MRF453 1/50 2SC1364 0.50 D21-10GH 0.24 0.42 F259 0.28 69.00 M38-121 WA 85.00 a Watt 2R4-10K 0.20 BC143 80131 MRF454 23.50 2SC1449 0.80 D21-10GJ M38-122GW BC147A 0.12 BD132 0.42 F271 0.26 69.00 65.00 R47-22K 0.20 MRF455 17.50 2SC1678 1.25 O 21-10LD M38-140LA 7 Watt BC147B 0.12 BD133 0.40 F273 0.18 55.00 65.00 2.50 2SC1909 1.45 DG7-5 M38-141LA 1R5-15K 0.25 BC148A 0.09 BD135 0.30 F336 0.34 MRF475 65.00 11 Watt MRF477 10.00 2SC1945 2.65 DB7.6 35.00 BC148B 0.09 00136 0.30 F337 029 55.00 M38-142GR 65.00 1R-15K 0.30 2.50 2SC1953 0.95 DB7-36 M38-142LA 17 Watt BC149 0.09 BD137 0.32 F338 0.32 0C16W 45.00 65.00 ppCC23 2SC1957 0.90 DG7.32 0.30 F355 0.37 1.50 M38-340P31 65.00 BC157 0.12 86138 0C42 0.75 2SC1969 1.95 DG13.2 45.00 M38-341GR VALVE AND CRT BASES BC158 0.09 BD139 0.32 F362 0.38 65.00 0C44 0.75 2SC2028 1.15 DH3-91 55.00 M38-341P31 65.00 B5D 5.50 8138 0.50 BC159 0.09 BD140 0.30 F363 0.65 45.00 0C45 0.55 2SC2029 1.95 DH7.91 M38-344P39 65.00 B7G 0.25 814A 3.00 BD144 1.10 F371 0.25 35.00 0070 0.45 2SC2078 1.45 DP7.5 M40-120W 59.00 BD150C 0.29 F394 0.19 DP7.6 35.00 B7G SKTD 0.25 12PIN CRT 0.95 0071 0.55 2SC2091 0.85 M43-12GM/O1 65.00 BD159 0.65 F422 0.32 DN13.78 35.00 09G 1.50 NUVISTOR 2.95 F457 0.32 0081 0.50 2SC2098 2.95 M43-12LG/01 49.00 130160 1.50 2SC2166 1.95 F15.101LC 49.00 084 0.70 OCTAL 0.35 F458 0.38 020080 1.45 M44-120LC 49.00 610166 0.55 2SC2314 0.60 F16-101GM 55.00 B9A SK610 35.00 F459 0.38 6201013 1.45 M44-120GR 65.00 0.35 130179 0.72 0.36 55.00 F467 0.66 R2322 0.50 2SC2371 F16-101 LO M47-25GR/22 49.00 B9ASKT 0.40 UX5 1.75 60182 0.70 2SD234 0.50 F595 0.23 R2323 0.66 F21 -130GR 55.00 M50-120GH 49.00 09G 0.75 UX7 1.75 BD201 0.63 3N211 1.95 F21-130LC 55.00 0.65 F597 0.25 R2540 2.49 M50-120GR 49.00 8108 0.20 CANS 0.30 BD202 0.90 3SK88 0.95 F21-131 GR 78.00 BD203 0.78 FR39 0.23 RCA16334 BY206 0.14 N23WE 5.00 UNE OUTPUT TRANSFORMERS E HT MULTIPLIERS VARICAP TUNERS PUSH BUTTON UNITS DIODES BY208-800 0.33 144001 0.04 6.35 ELC1043/05 MOLLARD 9.65 7.95 0.33 0.04 DECCA 100 7.95 1TTCVC20 DECCA, ITT, CVG206WAY BY210-800 144003 6.35 ELC1043/06 MULLARD 8.65 10.19 AÁ119 0.06 BY223 0.90 N4004 0.05 DECCA 1700 MONO 9.95 ITT CVC30 ITT CVC57 WAY DECCA 1730 8.95 PHILIPS G8550 6.96 U321 8.25 PHILIPS GB (55016 WAY 14.49 &4115 0.13 BY298400 0.22 144005 0.05 8.25 RANK T20A 6.91 U322 9.25 BÁ145 0.16 BY299-800 0.22 144007 0.06 DECCA 2230 9.95 THORN 3000 /3500 7.57 BÁ148 0.17 BYX10 0.20 N4148 0.02 GEC 2040 GRUNDIG 1500 15.45 THORN8500 5.80 POTENTIOMETERS 20MM QUICK BLOW FUSES BÁ154 0.06 BYX36150R 0.20 N4448 0.10 8.00 0.15 GRUNDIG 5010-6010. 22225011-601113.45 THORN9000 STANDARD VERTICAL POTS 6.12 100MA 8p each BA156 BYX38-6008 0.60 N5401 0.12 TRIFLER 5.45 BÁ157 0.30 BYX55-6000.30 0.14 UNIVERSAL MIN. VERTICAL POTS 0.12 200MA -SAMP 5psech N5402 8.25 BAX13 0.04 BYX71-600 1.10 N5403 0.12 ITT CVC30 SANDARD PHILIPS GO 8.50 HORIZONTAL POTS 0.12 BAX16 0.06 BZV95C30 0.35 145406 0.13 REPLACEMENT 20MM ANTI SURGE FUSES 081058 0.30 CS4B 4.50 0.10 PHILIPS G9 8.99 MIN. HORIZONTAL POTS 0.12 145407 13.39 BT151 0.79 CS10B 9.45 145408 0.16 PHILIPS G11 ELECTROLYTIC CAPACITORS CONVERGENCE PRE -SETS 0.30 10.95 100MA 800MA 15p each BY126 0.10 0A47 0.09 TT44 0.04 PYE 725 SLIDERS LOG 0.48 - 12.40 DECCA 301400400/35081 2.85 '1A-5AMP 12p each BY127 0.11 0A90 0.05 177923 0.15 RBM T20A SLIDERS LINEAR 0.48 11.15 DECCA 80/100 2.99 BY133 0.15 0.06 TANDBERGE90* (400/350V) 0491 TT2002 0.10 DECCA 1700 BY164 0.45 0A95 0.06 TELEFUNKEN 7114 11.15 SPARES & AIDS 9.50 (200- 3.55 BY176 1.20 0.10 THORN 1590 200400-350V) 0A202 9.20 2.25 FOAM CLEANSER 0.79 PUSH PULL MAINS SWITCH BY179 0.63 IN21DR 5.00 THORN 8000 GEC 21101600/30081 ZENER DIODES 9.95 1.80 FREEZE IT 0.92 (DECCA, GFC, RANK, THORN BT182 0.55 IN238 5.00 THORN 9000 n-r CVC201200/40081 THORN 9800 22.40 PHILIPS G8 2.25 SOLDA MOP 0.64 ETC.) 1.02 BY184 0.35 1N23C 5.00 BZX61 Series 0.15 (600/300V) THORN MAIN TRANSFORMER PHILIPS G9 (2200/63V) 1.19 SWITCH CLEANER 0.79 PYE IF GAIN MODULE 6.99 BY199 0.40 IN23ER 5.00 BZY88 Series, 010 ANODE CAP (276V) 0.69 3000/3500 9.70 PHILIPS G11 (470/250V) 2.35 W D40 1.25

32 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com uscu4Y0 PHONE P. M. COMPONENTS LTD TELEX 0474 813225 SELECTRON HOUSE, WROTHAM ROAD 966371 3 LINES MEOPHAM GREEN, MEOPHAM, KENT DAI3OQY PM COMP

M8223 4.50 QS1202 3.95 UL84 015 3.35 6BC8 1.00 6JU8 2.50 12SJ7 0.60 833A 60.00 A SELECTION FROM OUR M8224 2.00 Q51203 4.15 UU5 3.50 3522 3.00 6604 1.50 6JS6C 4.95 12SN7GT 1.85 866A 4.50 M8225 3.50 QS1205 3.85 UU7 9.00 384 7.00 6606 2.50 6J7G 4.15 12SR7 2.50 872A 27.50 STOCK OF BRANDED VALVES ME1401 29.50 051206 1.05 UU8 9.00 357 4.50 68E6 0.72 6K7G 2.00 1250701 1.50 873 60.00 ME1402 20.50 GS1207 0.90 UY41 3.50 3824 10.00 68F5 1.60 6K8Y/G 3.00 1303 3.20 884 5.50 A1714 18.50 EL822 12.96 ME 1501 14.00 051208 0.90 UY85 0.70 68G6G 3.00 8KD8 5.50 1307 3.20 930 9.95 A1834 7.50 EBF80 0.86 MH4 3.50 3626 24.00 EMI 9.00 051209 3.15 V235A/1K 88116 1.95 931A 13.95 A1998 11.50 EBF83 0.85 MHLD6 4.00 3528 12.00 6KM8 2.50 1309 3.20 EM4 9.00 051210 L50 250.00 66118 1.50 954 1.00 A2087 1130 EBF85 0.95 EM80 ML4 4.50 3826 1.50 6K18 2.95 1313E7 2.50 0.70 051211 1.50 V2384/1K 68J6 1.20 955 1.00 A2134 14.95 EBF89 0.70 EM81 M548 5.50 304 1.00 61.1 2.50 13DR7 2.95 0.70 051212 3.20 68K4 4.00 958A 1.00 A2293 6.50 EBF93 0.96 EM84 MU14 1.50 295.00 3C23 19.00 6L15 3.15 115 051213 5.00 66K7Á 1.95 13E1 115.100 1299A 0.80 A2599 37.50 EBL1 2.50 EM85 3.86 MZI-100 125.00 051215 2.10 V240C/2K 3C45 24.00 6618 1.15 6L19 3.95 13EM7 3.50 EBL21 1819 2.50 A2792 27.50 2.00 EM87 2.50 N37 12.50 051218 5.00 225.00 3CB6 1.50 68M8 6L6GC 2.95 1457 1.00 EC52 0.75 V241C/1K 0.56 1625 3.00 A2900 11.50 EN32 15.00 N78 9.85 QU37 8.50 3CN3A 2.50 66N4 1.85 8L6GCIGE13.95 17DW4A 2.95 EC70 1.76 185.00 1626 3.00 A3042 24.00 EN91 1.10 0A2 0.96 QV03-12 4.95 3CS6 0.95 68N6 1.65 6LBGT 1.50 17EW8 0.95 EC80 9.50 V2484A/2K 2050W 4.50 A3283 24.00 EN92 4.50 OA2WA 1.50 QV05-25 1.75 3CX3 2.50 68N7 4.50 611320 0.80 17J28 4.50 2050 3.95 EC81 315.00 AC/HL/DD 4.00 716 ESU150 14.95 0A3 2.50 QV06-20 29.50 3CY5 1.50 6BN8 3.95 6LF6 7.50 1803 1.80 EC86 1.00 V339 3.50 3545 4.00 AC/THI 4.00 ESU872 25.00 082 0.96 OV08-100 306 4.50 6805 0.79 6LJ8 2.50 19AU4GT 404A ACT22 EC88 1.00 V453 12.00 2.50 10.95 59.75 EY51 0.80 OB2WA 1.26 145.00 3D21A 29.50 61307A 0.72 8L06 4.95 19G3 AH241 39.00 EC90 1.10 VLS631 10.95 17.00 927 15.00 EY91 2.35 0C2 2.50 OV2-250045.00 3022 19.50 68L7GTA 3.95 6N7 2.50 19H4 23.95 AH238 39.00 EC91 5.50 EYB3 1.50 0C3 VP48 4.50 3E22 1927 25.00 1.50 QY3-125 65.00 49.50 6N7GT 2.50 19115 33.50 AL60 EC92 1.75 EY84 VP133 2.00 4212E 6.00 5.95 OD3 1.70 QY4-250 70.00 3EH7 1.95 68135 0.70 8P15 1.50 1906 9.00 250.00 AN1 14.00 EC93 1.50 EY86/87 VR75/30 3.00 0.50 0M4 1.00 GY4-400 76.00 3EJ7 1.95 6BR7 4.95 6P25 4.00 20A2 10.50 4313C 4.00 ARP12 0.70 EC95 7.00 EY88 0.56 0M56 3.00 VR101 2.00 43280 9.00 910 4.00 3W4GT 2.50 68R8 2.15 6P26 4.00 2001 0.70 AR P34 1.25 EY91 5.50 OM6 1.75 VR105/30 1.50 5642 9.50 R16 12.00 455515 115.00 6BR8A 2.15 6P28 2.00 20LF6 3.50 ARP35 2.00 EC/3010 12.00 EY500A 2.50 ORP43 2.50 R17 1.50 VR150/30 1.15 5651 2.50 ECC32 3.50 4-65A 59.00 8857 5.50 607 1.20 20L1 0.95 ATP4 2.50 EY802 0.70 ORP50 3.95 R18 2.50 VT52 2.50 68W4 5654 1.95 ECC33 4687A 9.50 1.50 607GT 1.20 20P1 0.55 AX50 5.50 3.50 6235 0.75 0RP93 12.00 R19 2.50 VU29 4.50 68W6 5.35 5863 1.95 ECC35 3.50 4-125A 55.00 6R7G 3.15 20P3 0.60 9240 2.75 P61 2.50 R20 1.20 VU39 1.50 5670 3.25 AZ11 4.50 ECC81 1.15 4-250A 68W7 1.50 6S4A 1.50 20P4 1.95 E241 2.75 P41 2.50 R1169 55.00 W21 4.50 65.00 68W8 4.00 5672 4.50 AZ31 2.50 ECC81 Special 4832 35.00 6SA7GT 1.35 20P5 1.15 9280 0.75 PABC80 0.50 RG1-125 4.95 W77 65X6 0.48 5687 4.50 13163 2.00 Quality 1.95 5.00 46074 1.'5 BSC7 1.50 211U8 2.50 E281 6.75 PC86 0.75 RG1-240A14.50 W729 1.00 88X7GT 3.50 5692 3.50 BS450 67.00 ECC82 0.56 1.50 4826 1.95 6SG7 1.35 2481 39.50 EZ90 PC88 0.75 RG3-250A 3.50 W739 1.50 68Z6 2.50 5696 2.75 BS810 55.00 ECC82 Philips 4C27 85117 1.35 25L6GT 1.75 F6064 2.95 PC92 3.50 RG3-1250A X24 25.00 68Z7 2.95 5704 3.50 85814 55.00 1.95 1.00 4C28 6SJ7GT 1.20 25806 1.75 FW4/800 2.95 PC97 1.10 35.00 X86/X65 4.95 25.00 6C4 1.10 5718 6.15 CIK 19.00 ECC83 0.86 4CB6 6SK7 1.35 29C1 19.50 PC800 1.10 RK2K25 62.50 X76M 1.95 1.95 6C5 1.95 5725 2.50 C3JA 21.00 ECC83 Brimar G55/1K 9.00 4CX250B 6SK7GT 1.35 30C17 0.40 PC900 RK-20A 12.00 XC24 1.50 6C6 2.50 30018 5726 1.50 C6A 9.00 1.39 G180/2M 9.00 PCC84 1'79 SUMAC 49.00 6SL7GT 0.85 1.48 54.95 0.40 51.16 1.50 xC25 0.50 6C8G 1.50 30F5 0.95 5727 1.95 C1108 ECC83 Philips G240/2D 9.00 PCC85 0.64 4CX250BM 6SN7GT 1.35 5749 C112G 70.00 RPL16 12.00 XFW47 1.50 6C11 2.50 30FL1 1.00 2.50 116 GC108 17.50 PCC88 0.70 SUMAC 75.00 6507 1.35 5750 1.85 C1134 32.00 RPY13 2.50 XFW50 1.50 6C15 2.50 30FL2 1.35 EC084 0.50 GC10D 17.50 PCC89 0.70 4CX250K 6C18 8557 1.95 5751 2.95 C11484 115.00 RPY43 2.50 XG2-6400 2.50 6WGT 30FL12 0.95 ECC85 0.60 GC10/45 17.50 PCC189 0.70 RPY82 2.50 SUMAC 85.00 6CA4 4.95 1.75 5763 4.95 C1149/1 130.00 ECC/36 135.00 6U8 1.15 30f L13 1.10 2.75 GC10/4E 17.50 PCC805 0.70 RR3-250 4CX125C 125.00 6CA7 3.50 5814A 3.25 C1150/1 135.00 ECC88 15.00 XG5-500 22.50 6U8A 30F L14 1.25 0.95 GC12/48 17.50 PCC806 0.80 RR3-1250 35.00 XLI SUMAC 6C85 3.95 1.50 C1534 32.00 ECC91 -5V 1.50 BV6GT 30L1 0.45 5829WA 6.50 2.00 GD136W 6.00 PCE82 0.80 R5613 45.00 XL628FT 7.50 4CX350A 95.00 1.15 CCA 2.80'I ECC180 0.72 GDT120M 6C86 1.95 6X2N 1.00 30L15 0.00 5c36 5.50 5.00 PCF80 0.66 RS685 54.95 XNP12 40213 75.00 CC3L 0.90 ECC189 GE10 2.50 6CD8GA 4.50 6X4 1.50 30L17 0.60 5678 7.50 0.76 9.00 PCF82 0.80 RS688 52.15 4G57 2.25 CL33 2.00 ECC801S 3.50 GN4 XR1 -1600A 6CF6 1.S0 6X5GT 1.00 30P4MR 1.00 5840 3.50 6.00 PCF84 0.86 56F17 5.95 4GV7 2.25 CV Nos Prices ECC803S 3.50 GNU). 15.00 49.50 6CG7 2.25 6X5GTY 1.00 30P12 1.00 5842 11.00 PCF86 1.20 S8F33 25.95 4J52 75.00 on request ECC804 0.80 GR10G 4.00 XR1-3200A 6CH6 8.95 6X8A 2.25 30P18 0.80 5847 PCF87 0.40 811E12 38.00 4JC6A 2.95 10.95 ECC2000 12.00 GS10C 16.50 79.50 6CL3 3.95 7A6 30P19 1.00 PCF200 1.80 S30/2K 12.00 4X150A 35.00 4.50 5879 8.50 DÁ41201 22.50 ECF80 GS1OH 12.00 XR1-8400A 6CL6 9.25 30PL1 2.50 1.15 PCF201 1.80 5104/1K 10.00 5A/102D 8.50 7A7 2.00 5886 13.95 DA42 17.50 ECF82 G5120 12.00 99.50 6CL8A 1.50 30PL13 0.60 1.15 PCF800 0.40 5109/1K 15.00 5A152M 9.00 7AD7 1.75 5894 39.50 DA90 o 4.50 ECF86 1.70 GT1C 14.00 PCF801 Y503 25.00 6CM5 1.60 30P1.14 1.75 1.35 5130 5.9S 5A163K 10.00 7B6 3.50 5899 4.50 DA100 125.00 ECF200 1.86 GT1CS/S13.00 Y65 6.95 6CM7 2.95 31JS6A 5.50 PCF802 0.60 S130P 5.96 5A170K 8.25 757 2.50 5963 1.75 DAF91 0.70 ECF202 GTE 175M 8.00 Y602 12.00 BC56 0.75 33A/158M 1.85 PCF805 1.25 SC1/800 5.00 5A-180M 9.00 7C5 3.50 5965 2.25 DAF96 0.65 ECF801 0.85 GTR150W 1.00 PCF806 1.00 YD1100 75.00 6CW4 6.50 7C6 2.50 19.50 SC1/1100 8.00 YJ1060 5A-206K 10.00 35A5 6005 1.85 DC70 1.75 ECF804 6.00 GU20 35.00 PCF808 1.25 265.00 6CY5 1.00 7E7 2.50 4.50 SAMB 2.15 351.6G1 6012 16.00 DC90 1.20 ECF805 2.50 G1150 17.50 PCH200 1.50 SC1/1200 5.00 YL1020 29.00 6D6 2.50 2.00 YL1070 5AN8 1.20 7H7 3.50 35W4 0.70 6021 3.85 DCX4-1000 ECF806 1025 GXU1 13.50 PCL82 015 SC1/1300 6.00 195.00 5AR4 6DC6 2.35 YLI071 2.00 7AU7 1.50 35Z3 1.85 6057 2.50 12.00 ECH3 2.50 GXU3 24.00 PCL83 2.50 Sci /2000 9.00 195.00 5AU4 1.50 6DJ8 0.95, DCX4-5000 SD6000M YL1290 65.00 7J7 5.50 38HE7 4.50 6058 3.95 ECHO 3.00 GXU5OSS PCL84 0.75 588 2.50 BDK6 1.15 25.00 ECH35 3.50 45.00 Z77 1.20 6005 6.50 7Y4 2.50 40K06 5.50 6059 3.75 14.50 PCL85 0.80 58.110M 10.00 DET16 28.50 ECH42 1.00 SP41 5.00 Z302C 12.00 888 2.50 42 6.95 6060 2.25 GY501 1.20 PC1-86 0.85 55-254M 14.50 80068 2.50 DET18 28.50 ECH81 0.85 SP42 3.00 Z359 9.00 6DT6A 1.50 8510 2.50 47 6.00 6062 4.50 GY802 1.00 PCL800 0.80 5B-255M 19.50 6063 DET23 35.00 ECH83 0.78 GZ30 1.00 SP48 4.95 Z5055 15.00 60W4 2.15 8805 1.95 50A5 1.50 2.00 PCL805 0.90 58-256M 9.00 6064 DET24 39.00 ECH84 0.69 GZ31 1.00 55501 35.00 Z520M 4.00 6E44 8F07 1.95 5005 0.95 325 PD500 3.50 58-257M 9.00 4.95 6067 1.95 DET25 22.00 ECH2000 1.50 0Z32 1.00 ST11 1.50 2521 M 5.00 10132 1.25 50CD6G PD510 3.65 58-258M 14.50 6EA7 2.50 1.15 6072 4.20 DET29 32.00 E0.80 0.80 G233 4.50 STV280/40 Z7000 3.00 100E7 PE1-100 69.00 5C22 125-00 6EA8 2.50 2.50 50EH5 1.50 6080 DF91 0.70 ECL82 0.86 GZ34 215 11.95 Z749 0.00 8.50 PEN25 2.00 5R4GB 3.50 6E88 1.75 10F1 0.75 50JY6 2.95 6080WA 8.50 DF92 0.60 ECL83 2.50 GZ34 U L STV280/80 Z759 19.85 3.95 PEN40DD 2.50 5R4GY 3.50 6EM5 2.50 10GK6 1.95 52KU 2.00 6096 DF96 0.65 ECL84 0.74 G237 4.50 19.95 2800U 3.00 2.85 PEN45 3.00 514 5.95 6EM7 2.50 10P14 2.50 53CG 15.00 6132 10.00 DF97 1.00 ECL85 0.69 HAA91 SU42 4.95 1803U 15.85 10P18 1.00 PEN45D0 3.00 5114G 2.50 6EU7 0.78 61SPT 4.50 6136 2.50 O 663 1.20 ECL86 0.80 HABC80 0.90 TB2.5/300 241000 12.50 1.95 10LD11 1.00 OH77 PEN46 2.00 5114G8 2.50 7581 3.50 61468 9.95 0.90 ECL805 0.69 HBC90 0.75 85.00 ZA1001 1.50 6EU8 1.75 101012 0.65 DH79 PE06-40N 5V4G 1.25 75C7 2.50 6157 2.50 0.58 EF37A 2.00 HBC91 0.80 152-300 45.00 ZA1002 1.50 6EV7 2.95 11E3 55.00 DH149 2.00 EF39 1.10 42.00 ZC1040 5Y3GT 1.95 83 8.50 6158 3.20 HF93 0.75 PFL200 783/20n^ 8.00 6EW6 1.50 12A6 DK91 0.90 EF41 3.50 0.95 ZM1005 9.00 5Z4GT 0.05 3.95 84 3.00 6201 6.45 HF94 1.50 P121 2.50 15L-2-3uu 6/30L2 6EW7 4.50 12AD6 DK92 1.20 EF42 3.50 ZM1020 8.95 0.70 1.50 85M 6.50 6205 6.95 HK90 1.06 PL36 275.00 BF1 12AG8 DK98 2.50 EF50 2.50 0.95 ZM1021 8.00 6A/203K 9.00 2.00 1.50 85A2 1.50 6211 2.50 HL2K 3.50 PL38 1.50 TD7-1004 6A7 6F5 4.95 12AL5 1.00 90AV 10.00 DL35 2.50 EF55 4.96 HL23DD 4.00 ZM1023 7.95 6267 2.25 PL81 0.72 25.00 6A80 41.1: 6F6 2.50 12A16 0.95 9007 DL63 1.00 EF70 1.20 HL41 ZM1041 14.00 2.70 6350 2.00 3.50 PL81A 0.72 1003-10F 6AC7 2.00 6F8G 2.00 12AT7 1.15 90CG 13.50 DL70 2.50 EF71 1.50 HL4ppDD 3.50 ZM1082 9.00 6360 4.50 PL82 0.60 35.00 6AF4A 2.50 6F7 5.50 12AT7WA 2.50 DL73 2.50 EF72 1.20 HL90 0.70 ZM1084 10.00 90CV 12.50 6386 14.50 PL83 0.52 103-12 4.00 6AF9 4.15 6F12 1.50 12AU6 1.60 DL91 1.50 EF73 1.00 HL92 1.50 ZM1177 5.00 91AG 9.00 6545 8.50 P184 0.78 TDD4 5.50 6AG5 1.50 6F13 3.00 12AU7 0.55 92AG DL92 0.95 EF80 0.56 HL133/DD 3.50 P188 1,00 ZM1202 55.00 19.50 6550A 10.95 DL93 1.10 EF83 3.50 TP25 1.50 ZM1263 4.00 6AG7 1.95 6F14 1.00 12AV6 1.95 92AV 1250 HR2 4.00 PL95 TSP4 6688 6.50 DL94 2.50 EF85 0.50 1.75 7.00 2M1612 3.00 6AH6 2.50 6F17 2.75 12AV7 2.50 95A1 8.50 HY90 1.00 PL302 1.00 TT71 1.50 12AX4GT 6870 /1.50 131.96 2.50 EF86 2.25 1A3 4.50 6AJ4 2.00 6F21 2.50 1.00 HVR2 3.00 PL345 12.50 1715 34.95 6AJ7 124X7 0.65 6887 9.50 DLS10 13.50 EF86 Special IACB 1.20 2.00 6F23 0.60 JP9-74 50.00 PL500 1.10 TT21 45.00 6AK5 1,50 12AX7WA 2.50 68838 9.95 DLS16 10.00 Ouality 3.15 1B3GT 1.95 6F24 1.25 K3118 85.00 PL504 1.15 1122 45.00 6AK6 2.50 6F25 12AY7 3.95 6973 5.95 DM70 1.95 EF89 1.50 KR6/3 45.00 1822 10.00 1.25 108C1 1.50 DM160 PL508 1.75 6AL5 0.50 6F28 12AZ7A 1.95 7025 2.50 2.75 EF91 1.95 KT8C 7.00 11100 57.00 1624 14.95 1.25 15082 6.95 DY51 PL509 4.85 6AM4 3.25 6F32 1.25 121344 3.50 7027A 4.50 1.50 EF92 2.15 KT33C 3.50 TTR-31 MR 1835A 29.50 150C2 1.50 DY86/87 PL519 4.85 6AM5 6.00 6F33 17.00 125A6 1.50 7032 2.00 0.85 EF93 0.85 KT36 2.00 65.00 1BC2A 2.50 15004 2.15 DY802 PL802 5.95 6AM6 1.50 6FG5 128E6 1.95 7059 2.50 0.72 EF94 0.95 KT44 4.00 iCi 2.50 1.95 155ÚG 25.00 1.50 PL802T 3.50 TY2-125A 85.00 6AN5 2.05 6F07 12BH7A 2.50 7167 3.95 EF95 KT45 4.00 1C5GT 2.50 2.96 18581 1.50 PL820 2.95 TY4-400 70.00 6AN8A 2.55 6G6G 12616 1.75 7189 E81L 12.00 EF97 0.90 KT61 4.00 P15557 105 2.50 5.50 274A 15.00 2.35 EF98 0.90 29.50 TYB--600W 6405 1.75 128Y7A 2.75 307 7193 7.50 E82CC 3.50 KT63 2.00 PY32 1FD1 2.50 6GH8A 0.80 5.00 EF183 0.85 0.60 305.00 BAQB 0.85 12CA5 1.85 E83CC 3.50 KT66OSRAM PY33 0.50 1G3GT 2.50 6GK5 1.50 328A 15.00 E83F EF184 0.85 TYS2/250 6AR5 5.95 12CX6 1.20 388A 17.50 7233 5.50 15.00 PY81 1K3GT 6GK6 1.95 7.95 EF730 1.80 0.70 375.00 2.50 BARB 3.85 120068 3.50 425A5 E86C 9.50 KT66 USA 9.95 PY82 6GS7 2.15 8.00 EF731 3.50 0.70 U18-20 2.75 6AS5 1.50 12DW4A 431U E88C 7.95 KT66 GEC 14.95 PY83 1N2 6GV7 2.50 3.50 2.00 7247 2.95 EF732 3.50 0.70 U19 11.95 4.50 6AS6 2.50 E88CC 3.50 KT77 Gold Lion PY88 6GW6 2.50 12DW7 2.50 7360 13.50 E88CCSiemans EF800 11.00 0.65 U24 2.00 1N5GT 2.50 6AS7G 4.50 705A 8.00 10.95 PY500A 1.95 1P28 6141 9.50 12E1 17.95 7462 15.00 Special U25 0.90 25.00 6A16 0.75 7084 5.00 546 KT81 7.00 PY800 0.79 6H3N 1.10 12E14 28.00 7475 5.00 EF8Óe,5S 11.W U26 0.90 11'4 0.70 6418 1.7S 715A 6.00 E9000 7.95. KT88 USA 10.95 PY801 0.79 1115 12GN7 3.95 7486 75.00 EF812 0.85 U37 9.00 1.00 BAU4 2.00 6H6 1.35 715C 45.00 E9OF 7.9! KT88 G Lion 12HG7 4.50 EFL200 1.50 18.95 1)41 8.95 1X26 1.40 6AU6 0.95 6H6GT 1.95 725A 275.00 7551 6.95 E91 H 4.50 1(167 9.00 083-300 54.95 U50 2.00 1Z2 8.95 6HF8 0.951 12HG7A 4.50 7558 9.45 E92CC 3.95 91490 0.72 3.50 6AV6 0.75 803 14.95 K90 0.72 KTW61 2.50 0903.10 U82 3.00 6HS6 4.95 12J7GT 3.50 7586 11.00 E99F 6.99 0E08-200 287 1.50 6AW8A 2.50 805 39.00 EL32 0.95 KTW62 2.50 U191 0.70 6J4 2.15 12K5 1.00 7587 26.95 E1301. 19.95 145.00 2522 69.50 6AZ8 5.95 807 1.95 EL33 4.00 KTW63 2.00 U192 1.00 6J4WA 3.15 12K7GT 0.80 7591A 4.95 E180CC 6.50 OF40 55.00 2C21 1.00 657 2.80 810 45.00 EL34 2.25 KTZ63 2.50 U193 0.85 6.15 2.50 7609 47.00 E182CC 9.00 0P25 1.00 2c394 32.50 6B8G 1.50 811A 12.95 EL34 Mullard/ 163 1.50 U251 1.00 6..56 0.65 12SÁ7GT 1.ÓÓ 7733 5.50 9180F 6.50 1102/2K 00E03-12 6.50 2C398A 39.50 BBA6 0.95 813 18.50 Philips 4.50 6.95 U801 0.75 6JB6A 3.95 12SG7 4.75 813USA 45.00 7788 25.00 E186F 8.50 12.00 00E03-2027.00 2C40 37.00 6BA7 4.50 EL36 1.95 L120/2K UABC80 0.65 6JE6C 4.86 12SH7 1.00 7868 3.95 E188CC 7.50 95.00 00V02.6 19.50 2C42 29.50 68A8A 3.50 8295 14.50 EL37 9.00 L8720 UAF42 1.00 12SK7 1.00 8012 15.00 61T 15.00 LS98 8.95 00V03-10 5.50 2051 0.75 EL38 4.75 UBF80 0.80 2053 32.00 8042 55.00 E280F 19.50 M502A 80.00 O01/03-10 UBC41 EL41 3.50 2.95 2CY5 1.50 8102 3.95 E283CC 10.00 8,,r 00 Millard 15.00 UBC81 1.50 E142 2.00 OOV03-20 2D21 1.50 8106 2.95 E288CC 13.50 M537A 80.60 UBF89 0.60 EL81 6.95 2D21W 2.50 8136 E810F 25.00 M5143 155.00 25.00 UBL21 1.75 CALLERS WELCOME 1.00 E1148 EL83 5.95 M8079 8.00 OQV03-208 2E26 7.95 8156 10.95 1.00 EL84 0.75 UC92 1.20 E1524 8.95 M8082 7.50 32.00 2J42 93.00 ENTRANCE ON A227 8245 107.50 EL85 UCC84 0.70 * EA50 1.00 4.50 M8083 3.25 OQV06-40A 2K25 24.95 a298Á 6.50 EL86 UCC85 0.60 9478 1.95 0.85 M8091 760 27.50 2K25 Raytheon 50 YDS SOUTH OF MEOPHAM 8417 9.00 EL90 1.75 UCF80 1.00 GREEN EA79 1.95 M8096 3.00 QOV07-50 75.00 9001 1.50 EL91 6.00 UCH21 1.20 EABC80 0.70 M8098 5.50 63.50 UCH41 65.00 9006 0.90 EL95 0.70 2.50 2K26 CAR PARKING AVAILABLE EAC91 M8099 5.00 00203-20 18042 10.00 2.50 ELI 53 12.15 UCH42 2.50 3A/1076 12.00 EAF42 1.20 548100 5.50 42.50 Open Mon -Thurs 9am- 5.30pm Fridays 9am- 5.00pm 18045 10.00 EL183E 3.50 UCH81 0.65 3A/108A 9.00 EAF801 2.00 M8136 700 OS75.20 1.50 3A/1096 11.00 EL18P 3.50 UCL82 1.75 5534 1.50 M8137 5.50 0575/40 3.00 3A/1108 12.00 * 24 HOUR ANSWERPHONE SERVICE EL360 6.75 0592/10 5.00 UF41 1.15 * 9841 3.95 M8161 6.50 3Á/141K 11.50 ACCESS AND BARCLAYCARDORDERS WELCOME TRERMISTORS EL500 1.40 M8162 5.50 OS95/10 4.65 UF42 1.15 9891 0.85 EL504 1.40 3A/147J 7.50 MANY OTHER ITEMS AVAILABLE EBC33 2.50 M8163 5.50 05108/45 4.00 UF80 0.50 3A/167M * * VA1040 0.23 EL509 5.25 10.00 EBC41 1.95 M8190 4.50 05150/15 8.95 UF85 1.20 3A2 VA10565 0.23 EL519 3.95 EBC81 1.50 6.95 M8195 6.50 05150/30 1.15 UF89 2.50 3A3A 3.95 UK ORDERS P&P 50p PLEASE ADD V.A.T. AT 15% VA1104 0.70 EL802 EBC90 0.90 3.85 M8196 5.60 06150/45 7.00 UL41 4.50 344 1.10 VA8650 0.45 EL821 EBC91 0.90 9.50 M8204 5.50 Q51200 3.95 UL44 3.50 3AL5 0.95 EXPORT ORDERS WELCOME. CARRIAGE /POST AT COST V41097 0.25

CIRCLE 62 FOR FURTHER DETAILS.

ELECTRONICS & WIRELESS WORLD JUNE 1985 S.3

www.americanradiohistory.com TUTORIAL SERIES by D.M. Taub Sampled data servos -anew analysis This fourth instalment considers the response of a servo system to a sinusoidal signal

If a single frequency wo is applied to a quencies will be quite unrelated to pled -data and continous - signal por- conventional servo loop such as the one another and so one can no longer tions of the loop. one shown in Fig. 1, then provided speak of an 'open -loop gain' in the that the system is linear, this is the same sense as in a continuous sys- Time delay in the sampled -data portion only frequency that exists anywhere tem. In can be a time delay in the system. Weican then'define the There is a way out of the difficulty. practice, there of loop; 'open -loop gain' at this frequency as For the purpose of analysis we can in the sampled -data portion a the ratio of the signal at Y to that at V. replace the single sampler following that is to say its output values can This ratio will of course be a function the subtractor (Fig. 18) by a sampler appear a fraction of a sampling inter - of wo, and the nature of the function in each of its input lines (Fig. 19), the val later than the corresponding input determines whether or not the sys- two operating in synchronism. Thus values, as illustrated in Fig.20. Part of this delay can occur in the sampler, tem is stable and how it will respond instead of doing a subtraction to any input stimulus. between two continuous signals and for instance when sample values are In the case of a sampled -data servo sampling the result, we sample the converted from analogue to digital such as shown in Fig. 18, the situa- signals first, and carry out the sub- form. Another contributor can be the don is more complicated. The import- traction on the sampled versions. compensator. If this uses digital tech- ant point to notice here is that over niques it generally has to carry out at This is not something that would part of the loop the signal exists in least one multiplication and one addi- generally be possible in practice sampled -data form, and over the tion between receiving an input value remainder including the hold circuit because it would entail measuring the and producing the corresponding out- signals to and the plant, it exists as a continuous input and output relative put value, and this takes time. fixed reference, instead of signal. As indicated in the last part some These delays can be allowed -for as (May) compensation may take place merely measuring the difference follows. For the purpose of the analy- But if we could, it in either part or it may be divided between them. sis, assume the samplers and sam- between the two. The last -mentioned would give exactly the same error sig- pled -data compensator to be delay - so is no reason why we is assumed, for generality. nal, and there free, and follow the last-mentioned by should not assume it in the interests When a singlee frequency wo is a pure -delay element representing of analysis. applied to this system, the sampling the the total delay through the sampled - action introduces new frequencies ws The signals at V and Y in Fig. 19 are data section. This element will intro- Fig. 18. Servo loop in which - wo, ws + wo, 2wo - wo, 20 + wo now both of sampled -data form, and duce the same delay whether its input the error signal is sampled. and so on. Within the sampled- data we can define the gain between them, is a continuous or a sampled -data sig- portion there is a simple relationship the open-loop gain, as a function of nal, and so it makes no difference Fig. 19. Sampling the input between the gains at these various frequency. This will be a periodic whether we include it in the continu- and output signals is frequencies as discussed in April but function of frequency (as explained in ous or the sampled -data portion of the equivalent to the this is not so in the continuous - signal April's article) and the objective is to loop. Mathematically, it is easier to arrangement in Fig. 18. portion. Here the gains at these fre- find it in terms of the gains of the sam- do the first which gives the arrange- ment shown in Fig. 21. In terms of gain of the Sampled -data Continuous -signal complex frequency the portion portion time -delay element is -sr HAic(S) = e

Sampler where Ar is the delay introduced. In Continuous - Sampled- data Hold Output terms of w it is signal Plant compensator circuit compensator Hae(jw) ... 4.1 In other words, the gain has a modu- lus of 1 at all values of w, and a phase of -tuba .

data Continuous - signal Sampled - Gain characteristic of sampled -data portion portion portion

The output from a sampled -data Sampler network at any sampling instant n is Continuous - Output Input Sampled -data Hold as a linear func- -11 signal Plant generally expressed circuit compensator compensator tion of the input at that instant and the inputs and outputs at earlier sampling Sampler instants. Referring to Fig. 21, denote the sample values at V and X at o instant n by v(n) and x(n) respect -

34 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com ively, the values one instant earlier by (equations 3.2 and 4.1 respectively). v(n -1) and x(n -1), two instants The gain of any continuous signal Input values earlier by v(n -2) and x(n -2), and so compensation present is HBC(jw) and on. The algorithm of the sampled - that of the plant, HcD(jw). data compensator can then be Multiplying these gains together TIME expressed as gives the gain characteristic HxD(jw) covering the whole of the continuous- Output values x(n)=RIv(n)+RI,I-I v (n-1) + ... signal portion. A possible shape is sketched in Fig. 22(b). For the [ +ßv(n-m) -[7m_,x(n-1)+ assumed signal at X, the signal at D TIME ... +7, x (n - m)] will then be as represented by the line spectrum in Fig. 22(c). The effect of sampling is to cause where ßm, ßm_1 etc and Ym_1, Ym_2 etc Fig. 20. Sampled -data portion are constants. Moving the 'x' terms to each component in this spectrum to of the loop introduces a time the left -hand side, be repeated indefinitely, at intervals delay by of w,. After the sampler, therefore, caused the analogue -to-digital x(n)+7,,_,x(n-1)+...+'%,x(n-m) the total component at w , represent- ing the gain Hxy(jw"), will be the sum conversion process and - ßm v(n)+R",_, vl(n - 1) + ... of the following: digital computation time. Fig. 22. DerivatiOn of the +R (n-m). Hm(jw"), which was already pres- ent before sampling, gain HxY covering the From this expression, known as a Hm[j(ws + w")], repeated from continuous -sginal portion of 'recurrence formula', one can write ws (00, the loop an the output down a corresponding expression HxD[j(2ws + w")], repeated from sampler. relating the z- transforms of the sig- 2 w, + wo, and so on for higher multiples of ws, nals at X and V, X(z) and V(z) (a) Spectrum of signal at X } Magnitude respectively (see ref.5, sections 4.4 HxD[j( -we + w")], repeated from and 9.4). This expression is -ws + w, HxD[ j ( -2w, + w") ], repeated from x(z)[1+y _,Z'+...+7,z-m] -2ws + w", and so on for higher negative multiples =V(z)[ß",+R,,,-,z'+ ...+ßz-"'] I I --wo 0 wo of w,. TTFT1-I,-IE--1I -2ws -ws ws 2 w where z = eTs This sum will also represent the Phase ' gains at ws + w", 2w, + wo etc and at I f 1 Both sides can now be 1 1 multiplied by w", w" etc, ie at all -w, + -2w, + . I . . . . . - I zm and rearranged to give the gain as a values of mws + w", because the I 0 ' function of z: same terms are being summed in each X(z) case. In other words the value of HxY (bIH Magnitude a= xo Hvx(z) v(z) at every one of the frequencies mws + I

,zI- 1 +... w" is the sum of the values of HxD at all 1 ßmzm +13m- +R of them. The corresponding rela- ,zm I ' Z "'+ /n,. - + ...+7 I tionship also exists for the frequen- I ' cies mw, w". HxY, the gain of the 0 - -ails -ws To find the gain as a function of w set z continuous - signal portion followed by f Phase Ws 2ws giving Hvx(jw) = ------rz the sampler is thus Hxy(jw ) _ t 1 ---7.-.. emírw IT,o +... 13"' + 13,1 ' -' e"'-' +13" 4 2 +,01 eimTw +y Hxnlj(mws ... 4.3 1 \ '''._1 --- -L - ~ All the exponential terms repeat their The negative values of m in this \ values whenever Tw increases by 2n, expression can be eliminated by not- ing that the gains at equal positive and and so the function will be periodic as tMagnitude negative values of w are the complex illustrated in the April issue. lc) Spectrum of signal ô _ _ conjugates of one another. This gives 3 ^ ó atD ô3 3° ô ^ 3 ó ¡ 3 ô 3 Gain of continuous -signal portion Hxr(jw ) - Hxu(jw ) + - 3 I + followed by sampler ... 3 i g ,-.4 ' N +E Hx1,[j(mws+w)J ._.ó Ì L--,-' ..^ l I The gain of this section is found by I `-' - I X X X X i assuming a sampled cosine wave at X + conj Hxu j(mws - w )] .t. (Fig. 21), calculating the spectrum of [ -,--.1,--1 -r--.1.-.1 t ...._.- the signal this produces at Y, and tak- In practice the characteristics of the -2ws Phase s 2w s ing the ratio between the spectral plant generally cause HxD to fall to a { '' components of the two as in April's I article. The mathematics can be kept Fig. 21. Time delay (Fig. 20) ó [ H ti I simple by assuming the signal at X to can be allowed -for in the l I be the sampled version of 2 cos w "t, continuous -signal ' . portion of ; so that from the equations for q(t) and , ` ' the loop. v(t), all its spectral components will have unit magnitude and zero phase angle. The spectral components at Y Sampled -data Continuous- signal portion will then be a direct measure of the portion gain at the corresponding frequen- (zero delay) cies. of Sampler The spectrum the signal at X is Continuous - Output Input Sampled -data Hold Time shown in Fig. 22(a), and as it passes signal Plant compensator circuit delay -- from X to D each component is sub- X compensator D jected to a different value of gain. The gain characteristics of the hold cir- Sampler cuit, Hxx,(jw) and of the time delay, H,m(jw), have already been given ELECTRONICS & WIRELESS WORLD JUNE 1985

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60 -120 Phase margin 80 160 ph Phase 40 +180

40

mag. 20 120

o CO Magnitude LO 60 ° 67° -40 10 20 50 100 200 500 1000 2000 5000 Gain margin FREQUENCY (Hz) -20

Fig. 23. Gain characteristic of the plant being controlled: Ha,. Notice the resonance at 2750Hz. -40 -60 10 20 50 100 200 500 1000 FREQUENCY (Hz)

Fig. 25. Open -loop gain characteristic, Hyr. Peaks between 500 and 1000Hz are caused respectively by the peak in the compensator gain characteristic (Fig. 24) and by the effect of aliasing on the 2750Hz plant resonance.

Magnitude

Phase

Fig. 24. Gain characteristic of the compensator, H, up to half the sampling frequency. negligible value beyond two or three times the sampling frequency. There- fore only the terms of the above summations corresponding to low values of m need to be taken into account. Fig. 26. Closed -loop gain characteristic, HDY. Notice that around 170Hz the output is about 2.5 times the input. Open and closed -loop gain and error ratio Plant: Two stages of integration Sampling frequency: fs - 2000Hz The total gain between V and Y in Fig. together with a 30db resonance at 21, i.e. the open -loop gain, is the pro- 2750Hz, as shown by the gain charac- Hold circuit (see May issue): Zero - duct of the gains of the sampled -data teristic in Fig. 23. The gain is order, i.e. a -0 REFERENCES and continuous-signal portions, i.e. Stubberud and -2.137 X 1015 24 shows the characteristic of 1. JJ. Distefano, A.R. IJ. Hc-o(jw) Figure _ Hxy(jw) I... 4.4 Williams. 'Feedback and Control Systems' Hvv(iw) Hvx(jw) -w2(iw + 273 - j 17280) the compensator, computed from (Schaum's Outline Series, McGraw-Hill, equation 4.2. Fig. 25 the open-loop New York, 1976). where Hvx(jw) is given by equations X 1 from equations 4.3 2. M. Healey. 'Principles of automatic con- 4.2 and Hxr(jw) by 4.3. (jw +273 +j17280) gain computed trol', (Hodder and Stoughton, London, and 4.4, and Fig. 26 the closed -loop 1975). The input signal at U is the sum of Sampled -data compensator a digi- gain, computed from the above equa- 3. M.K. Haynes. 'Magnetic recording tech- the signals at V and Y, and so the gain tal compensator is used. Its gain is tions and 4.5. Fig. 25 shows the sta- niques for buried servos'. IEEE Transac- between U and Y, the dosed -loop tions on Magnetics, Vol. MAG 17, 1981 pp given by equation 4.2 the polynomials bility margins to be as follows: 2730 -4. gain, is being of fifth order. The numerator phase margin 24.2° 4. N.H. Hansen. 'Head- positioning system Hvvrw) 4 5 coefficients ßs to ß° are respectively gain margin 6.7dB. using buried servo', ibid pp 2735 -8. Huv(iw) - 1 + Hvy(jw) 1.258 0.03125 -1.711 -0.03516 0.5664 0. in 5. P.A. Lynn. 'Introduction to the analysis These terms are explained Ref.1, and processing of signals' (Macmillan, The gain between U and V, i.e. the The denominator coefficients y5 to Y °, section 10.4. Details of the programs London, 1973). ratio of the error signal to the input, is (y5 being the coefficient of the zs used in the computations are given in 6. B.C. Kuo. 'Analysis and synthesis of term, ie 1) are respectively ref.9. sampled -data control systems (Prentice - 1 Huv(j(o) ° 1 0.7344 -0.2891 -0.9688 -0.4609 -0.01172 Hall, Englewood Cliffs, 1%ff, 1963) 1+ Hvy(jw) 7. A.M. Tropper. 'Matrix theory for electri- in sampled -data sec- cal engineenng students' (Harrap, London, Time delay Appendix 1962). tion: Example µs 8. S. Goldman. Transformation calculus -117 Gain of continuous -signal portion of and electrical transients', (Prentice-Hall, New York, 1949). The results obtained so far will now be Continuous - signal compensation: loop followed by sampler: 9. D.M. Taub. Programs for computing used to compute the open and closed- none, but the gain multiplication con- performance', IBM jmws) sampled -data servo loop response of a position- control stant within this section, KK, is Hxy(s) - ,-1,1 Hxa(s + Technical Report no.12.199, (IBM United of the system are as fol- adjusted to give an open -loop gain of Kingdom Laboratories, Hursley, May servo. Details 1982). lows. unity at 180Hz. Its value is 0.3555. ... U4.3 1985 36 ELECTRONICS & WIRELESS WORLD JUNE

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by R.E. Young, B.Sc (Eng.), F.I.E.E., Managing research M.R.Ae.S. and development

Our series continues with a description of the working of a small integrated team's approach to R & D, in contrast with the hierarchical approach often found. Management of large projects is discussed.

Examples of successful 'small - ence behind them (see Article 1), interview given late in 1984 by team' projects have been given in the group can cut expensive car designer and innovator,Sir earlier articles, notably the development time sufficiently to Alec Issigonis, on the occasion of 'video -on- telephone -cable' sys- hold a project within acceptable the 25th 'birthday' of his world - tem developed by the BBC prior cost limits. By the same token, famous 'Mini'. His success as the to World War II. " This - -- interchange can prevent more originator of the transverse - model of engineering R & D" was than one being altered at a time. engine, front wheel drive layout outstanding in several respects, Violation of this ground rule of - now "the norm for most small especially with regard to the way engineering R & D, i.e. for mem- cars" - is seen, not only in the in which research and develop- bers of a team to make major way the Mini continues (has not ment were made, in effect, an technical changes in isolation, become out-dated, rather the integrated whole, and did not can be one of the biggest threats reverse), but also in the fact that exist in watertight compart- that a project has to face. he is -- -still doing research on ments. This is virtually That this small -team approach small cars. His statement that "It impossible with 'family -tree' - is considered vital at the present is terribly important to have a Fig. 1. An example of a separated level - style manage- time, in the context of advances small team, otherwise communi- `supra- management' project ment which, by its very nature, development engineering, is cation breaks down" takes on a - the Anglo- French almost invariably brings a compa- shown quite specifically in an special significance in the present Concorde. ratively large organisation with it. It should be pointed out that such extensive management organisations have to be set up for large -scale projects; where, as an extreme example, putting men on the moon demands the deployment of immense resources, both technical and human, and which all have to be managed and controlled. Reverting, however, to the BBC case, the integration of research and development also included a user -component with all members of the team having in- the -field experience of the equipment, both in setting -up the complete video links and in their operation for actual programme service. Thus, among the economic advantages which can be claimed for the small -team approach, (and which have been outlined in earlier articles), is the way in which the coordination and inter- change possible with a closely -knit small team enables them to finalize the product as development proceeds. This means that, with suitable experi-

ELECTRONICS & WIRELESS WORLD JUNE 1985 :;9

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connection. although the experienced seen, for example, in the indus- tions for adopting this style of The implications of this state- manager draws the equivalent of trial 'clusters' of Great Britain. management involvement. As ment, together with the spread of these diagrams mentally and These points have made in already indicated, this approach Sir Alec's achievements, will be revises them continuously, this is some detail to show how full 'fam- can be reconciled with family - examined more closely in a later not a complete substitute for ily -tree' management control can tree management principles; but article, which is based to some putting them on paper. Thus, one be exercised over an R & D it does place heavy demands on extent on a current private ven- of the advantages of producing project being run in the much the manager's judgement, not ture R and D programme on a such diagrams is seen with the more open style as described, least with regard to his allocation combined electronics system/ situation in which more and more and without obtruding on it. of time between his overall automobile engineering approach effort is being brought to bear on The name 'Farmer's Foot', responsibility for the project to vehicle design and develop- a particularly intractable problem adopted a number of years ago for itself and the direct contribution ment. Its first part describes without any sign of its being this style of management, has which his range of experience some aspects of early work car- cracked. The accumulation of proved its worth as a self-defining enables him to make to the actual ried out on telemetry (instru- resources can pass almost unno- term with its allusion to the work on it. The spread of this mentation) equipment for tices in the absence of golden days of British agriculture contribution may extend from development testing of motor diagrammatic analysis when when the watchword was 'the giving guidance during the evolu- vehicles; and it is of interest attention is focussed almost farmer's foot is the best ferti- tion of 'sub- inventions' to that, with relevant docu- exclusively on the effective lizer'. This allusion covers an producing the solution to a prob- mentation published in early deployment of the additional individual approach to manage- lem which appears totally 1961, this original work was car- effort. In addition to its 'real - ment just as applicable to modern intractable. The latter, which ried out towards the end of the time' reporting role, the rapidly technology as to those years of may well be the key to the suc- 1950s. rising activity diagram can often advance in agriculture. Thus, cessful continuation of the provide valuable early warning during that period, when enor- project, is perhaps best illus- and enable anticipatory action to mous advances were made in the trated by one of the achievements Activity chart and project be taken. breeding of plants and animals, of Sir Robert Watson -Watt. administration Also among the facilities given British farmers were in effect In his book on the development by the generalized activity chart engaged in an international level - of radar2, A.P. Rowe recalls how project indistinguishable in a critical point had been reached In general, an engineering pro- is the ability to keep a watch on principle from a modern engi- in the original work at Orfordness taken to a successful the manning position, particu- ject neering R & D programme. where aircraft were being 'fol- conclusion has a certain well - larly with regard to peak loading. One aspect of R & D which lowed' by radar with " - -- the This is shown in Two working rules may be quoted defined 'shape'. should be introduced at this point range from the observers being the activity chart of Fig .1, with its here. The immediate one is that is the way in which research and continuously measured " , but no build -up to a pronounced peak peaks in manning on any single applications of it have been trans- method of finding bearing and associated distribution of sub -project or the equivalent ferred from one branch of UK seemed in sight. In other words, effort. Drawn in this instance for should be held to a ratio not technology to another. A general- it was not possible to bring even a a multi -team R & D project, it greatly exceeding 2:1 on the ized illustration of this may be primitive form of single- station may be taken as applying equally initial level of staff allocation for given in terms of biotechnology, radar system into operation until to a single small -team pro- that particular section of the announced publicly in 1980 as a this key problem of obtaining gramme or as an overall criterion work. This corresponds with the potential foundation of a new bearing direction finding for a major new technology ven- other guideline principle that if - - industry; and which obviously had been overcome. (Full opera- ture at national level, or the the chart shows a rise in activity involved a number of earlier tech- tional use of these stations also equivalent. This aspect is continuing much beyond the half- nological developments. Also, demands determination of covered in the next section on way point in the programme time - the technical continuity main- height; but the fundamental Supra- Management particu- scale, serious reassessment cf - tained over the whole field of UK requirement is for range /bearing, larly in terms of the British ability the whole situation is required. advanced engineering, with the and the original CHL stations did to evolve a wide- ranging and yet From the background given in accumulation of experience that work on this 'plan- position' flexible management approach, the introduction and from subse- goes with it, represent a national basis. ) where much of the coordination quent articles, it will be realised asset which should never be and organization appear to that a peak usually represents the The astonishing speed with under -estimated; and which is develop almost automatically, appearance of the unknowns which the problem was solved, particularly significant as being but nevertheless where unobtru- which are inseparable from R & and what may be called the 'pro- one of the main factors giving a sive, but full, control is D, and which because a new field ject stream' restored, is best flying start to any new work. maintained. is being entered, cannot be fore- shown by quoting from Rowe. least not for the The advantage that can be After being presented with an It will be appreciated that, des- seen, at particular combination of circum- taken of this flying start depends explicit statement of the situation pite its apparent simplicity, the flexibility that can be . on the seen operationally, "--Watson - out clearly stances being encountered It is, activity chart brings shown during development, Watt was back with a solution 'project -state' information cru- in fact, the need to cope with the R & especially during the crucial early -- within a few days "; and the R D technical unexpected that singles out cial for & stages; and this, of course, is future of radar [notably in inter- (progress) management and for D [project] administration from all other forms of management. where 'shop -floor' management ception was never again in doubt. control and direction of often makes its greatest contrib- There is no need to stress the resources. These can be, of In the attack on such a peak and turn, the efficacy of this ution. In vital nature and importance of course, 'survival' issues; as for its underlying causes, the project will be determined contribution this high technology break- instance, where the extent of the manager, as a team leader, must to a great extent by the rapport through. Even if not quite so peak in activity has not been rea- plan to 'stretch' his team, and the (the Issigonis 'communicaton') spectacular, similar turning - lised, and the peak has become a test of his leadership will be to do been established that has point successes by individuals are crisis with the future of the pro- this with the full knowledge and and his between the manager on record' extending over the ject possibly in doubt from then cooperation of each individual in team, and between the individu- as one whole spectrum of British radar; on. it. This will be recognized als in it. Obviously, drawing any form of of the elements in the small team while Sir Stanley Hooker's autobiogra- activity diagram does not neces- approach; and it will be realized In fact, as noted earler,it is the recently published sarily guarantee the elimination that this approach has contri- need to deal with the unknowns phy" gives an up -to -date account admittedly of all R & D problems; but, buted to the technical flexibility that is one of the main justifica- of how one individual, & WIRELESS WORLD JUNE 1985 40 ELECTRONICS

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of unquestioned international (Government- level) organisa- standing, provided the crucial tions achieved by the lizard Additional sub -projects direction which "saved" a major Committee. This achievement for investigation of high -technology development was perhaps seen at its height in new problems project - the RB 211 jet engine - the period of 'getting it going'. from the diastrous failure which This colloquialism covers inten- 'Exploratory' sub projects seemed inevitable at the time. sive effort directed over a range Number of sub- As with Sir Robert Watson - extending from gaining technical Basic sub projects, mainly direct evaluation Watt the value of Sir Stanley's support at high level for what was projects work is incalculable. Also, even little more than an unproved idea, before these outstanding to obtaining the necessary Confirmation R & D phase proper Overlap achievements, both men had Cabinet authority for the Project under field" demonstrated their extraordinary unprecedented amount of finance stage conditions capacity to move into any plane of required for carrying out the pro- Investigation, Finalised development engineering, and, gramme which was being put Prototype development Major _project however new, to make a master forward. I---analysis of performance measurement activities unknowns support contribution to it. Hooker had As noted in the first article, the 'sorted -out' a number of aero- magnitude of the technological engines, beginning with the strength that was eventually Time Merlin piston engine and culmi- brought together on a national nating with the RB 211 (the Sta t of scale for this programme has not project names of fifteen are given in his really been approached in the UK Appendix 1); while the degree of since those days. It was sug- Watson -Watt's participation is gested at the same time, sized, with entrance into a Fig. 2. Generalized activity exemplified by his being named however, that the potential for number of technological worlds; chart for multi -team R &D as sole or co- inventor for five undertaking such an extensive but the success of the supra - projects British patents coming from the management is seen in the project still existed (was " - -- not initially perhaps somewhat sur- work alone done in the 1930s and project development times far below the surface "); and prising in this instance associated with the Slough achieved despite the 'design - indeed this can be taken futher Fly -by -wire Actuation for Com- research station. interplay' which compounded all with the recent publication of bat Aircraft. As stated in the the problems as they were 'inside' information on the Con- paper "Many of the system corde uncovered and then attacked. Supra- management and R & D development programme. characteristics of Concorde, such Though not of the same absolute These problems could fairly be as pressures, temperatures and size, the Anglo- French Concorde called high -technology ones performance are typical of those The individual manager is con- was strictly comparable - as a (almost invariably the techniques required for actuation in the field cerned primarily with the supra- management project - with evolved to meet them were of military aircraft ". 'management economics' aspect the UK radar development; and entirely new, and usually had an This information flow had of running a comparatively small thus it can be said that in imple- electronic content). Typical of started with an experimental but carefully selected team; and, menting their share of the this was the means which was Tay-engined Viscount aircraft at the same time, maintaining his programme, the British demon- developed to deal with the very equipped with two electrical con- large variations own technical interest in the pro- strated that the potential was which take place trol systems and one mechanical ject to give it the maximum there and could be activated. in engine airflow with change in standby system with the co -pilot benefit aircraft speed, varying of his background and The main source of informatim from vir- in control of it. This general sys- tually experience. Although basically on the Concorde programme, zero at take -off to the tem philosophy, as developed, for single -project administration supersonic cruise condition at seen as an interlocking 'multi - appears in the Concorde with two and control, this Mach 2. In this instance, general manage- project', is Sir Stanley Hooker's an electrical lanes (channels) in an ment style can be adapted for autobiography`. Already brought engine inlet system was deve- active /standby arrangement with more than one team, loped consisting of very large provided into this article, this book gives a self -monitoring of the operating movable flaps, the limitations of 'spread' are penetrating view of the complex- ramps and doors, lane. Control is automatically the control of which is recognised. ity and difficulty of maintaining scheduled switched to the standby lane in by an automatic electronic 'Supra- Management' men- project flow and cohesion in co- sys- the event of failure on the active - a tem. tioned by name for the first time operative undertaking of this system. As a further safeguard, From experience of compar- at the beginning of this article - size. This is done not only with there is a back -up mechanical has already been introduced indi- regard to the propulsion side with able project work it will be monitoring system which comes rectly in this series, notably in Sir Stanley's involvement with apparent that, with the interac- into operation should a common connection with the unparalleled the application of the Olympus tion with other areas of fault or the equivalent develop on evolution of British radar in engine to the Concorde; but also technology, such a development the electrical side. World War II. In this general con- in terms of the remarkable overall programme would call for a corre- It will be appreciated that there spondingly large amount of time text, A.P. Rowe3 has given management of the development is a certain independent check insight into the workings of "that of this unique airliner. Problems and effort to be expended on it. element in such a main /standby grand body" the Tizard Commit- there were with this 'bi- national' Of even more significance in multiple system; but that near - tee, with its " - -- objectivity and venture, not the least being lan- the present context is a paper by instantaneous decision -taking driving power" which, in effect, guage (with technical inter- Hilton and Steed, published in required in an emergency set in train these "momentous change, this involves 'way of Aerospace for March 19845, demands human intervention for events" . Not only did this mark - thinking' in addition to straight which throws considerable light changeover action. The question as has already been noted - the translation), but with this, as on the Concorde flying control of human intervention - its commencement of the high -tech- with the engineering problems, system and its development. degree and timing - is, of nology era in Great Britain, but it there was managerial anticipa- More than one major aspect is course, common to other com- also represented the emergence tion and - evidently - almost brought in here, outstandingly plex control systems; and of supra- management in the inspired forward planning. that of the spin -off and exchange represents just one element in coordination and direction of the The immensity of the task that achieved as part of management flight trials and in work of a number of independent lay ahead cannot be over -empha- economics . The key is in the title, analysis and assessment which

ELECTRONICS & WIRELESS WORLD JUNE 1985 41

www.americanradiohistory.com INVENTION & ELECTRONICS

can rarely be carried out concur- this era, it is only possible to career, the mix of Cockcroft's rently. With the multiple- include a fraction of the names of deliberately acquired and programme character of the Con- those who were responsible for immense technical experience, corde project in mind, it will be advances in this area of British combined with his world -level realised how remarkable was the radar; but, in the present con- research, may be said to repre- text, it is imperative to list the sent, within the technological following, not necessarily in climate of Great Britain, the chronological order. ultimate, and ideal, career train- The national `mix' and the J. Sayers in Birmingham intro- ing course for the engineering universities duced strapping between cavity student. segments to obviate mode jump- Two examples will be taken During the earlier part of 1984, ing on the generated radio from Egon Larson's book 'The to give an advertisement appeared in the frequency. Cavendish Laboratory's British Press for "real engineers" A team at Leeds under Prof. some indication of Cockcroft's working in collabor- of penetration into most - all rounders with manage- E.C. Stoner, depth experience in more ation with one at Manchester branches of engineering practice. References ment -grade than one field of engineering. The under Prof. D.R. Hartree, The first shows Cockcroft determined a full 1. Langley, J. Small Car with big pros and cons of bringing non- explained and winding armatures, assembling Reputation, The Daily Telegraph 29th physical picture of the complex switchgear, and testing electrical August 1984 specialists into innovative work have already been discussed at path distribution of electrons machines at Metropolitan-Vick- 2. Young R.E.; 'Vehicle Instrumentation several points in this series; and inside the magnetron when oscil- ers in Manchester. He had joined and Development,' article (This series lating. a college in Wireless World.To be published) it does seem possible to state that the firm as apprentice provided the necessary flexibility A new technique to overcome 1920, following the interruption 3. Rowe E, A.P.; One story of Radar, the difficulty of making the reflex to his studies with his three year The University Press, Cambridge 1948 and adaptability are there the more broadly based engineer can klystron (used as a local oscilla- service in the Army in the 1914- & Whiddington, P.: 4. Crowther, J.G. contribute to the practical deve- tor) was developed in the 18 War. Larson quotes Science at War; His Majesty's Stationery of Bristol under he Office, London, 1947 lopment of an idea, which after all University Cockcroft's recalling that R.W.Sutton, "with close contact found that his mathematics ' - -- is specialized in itself . 5. Hooker, S.G.; Not Much of an with the G.E.C.,and in came back with surprising com- Engineer, Air Life Publishing Limited, Now it is one of the main sub- - -- Shrewsbury, England 1984 particular, with E.M.I." pleteness" on his return to the of the series that these missions In addition, a paragraph in'Sci- (then) Manchester College of 6. Hilton, R.G. and Steed, D.I. Fly - by - and adapta- qualities of flexibility ence at War' gives "Prof. J.D. Technology. Wire Actuation for Combat Aircraft bility to the new and untried are Aerospace, Vol.11 No.3 March 1985 Cockcroft, Prof. M.L.E. Oli- The second example speaks for found in Great Britain, almost as phant, Lewis and others" as the itself. During his construction of 7. Larsen, E.; The Cavendish a national characteristic. It has Laboratory, Edmund Ward, London team brought in from funda- the first particle accelerator at the also been made clear that of the 1962. mental research in atomic (significantly in the many factors that have contri- Cavendish physics to look into the need for period 1929 -32), the workshop - buted to this result, education in very short waves . The contribu- trained Cockcroft built his its widest sense is of crucial tion that was made by this team is machine, in effect, round two dis- importance; and it is in this con- stated to have been a most used petrol-pump cyclinders. He nection that the invention of the important factor in the success had to overcome formidable high - cavity magnetron3 can be used to achieved in this national pro- problems, while it is illustrate how the 'British' appr- vacuum gramme. worthy of note that the machine works in practice and, at the oach volts. same time, to show how this Professor J.D. Cockcroft, who worked at 300,000 remarkable advance was made by became Sir John Cockcroft, The second of these two issues a university. O.M.,F.R.S., represents is firmly on the national scale. In The cavity magnetron of J.T. another golden age in Britain. the present context it concerns Randall and H.A.H. Boot, with This is essentially associated the mix within each university its initial basic development in with that great institution the (including the apportioning of the physics laboratory at Birm- Cavendish Laboratory at Cam- resources and effort generally), various universities ingham University, " - --on the bridge and the nuclear research between the second design, worked - and carried on there. Apart from his and between them and the out- worked so well that it is literally pre -eminence as a research phy- side world, e.g. their true to say that for years no sub- sicist, Cockcroft was an Government -type sponsoring/ stantial variation from the outstanding development engi- directing authorities. original main lines was an neer possessing all the talents of The structure and existence of improvement " . Anyone who has the ideal 'participation' R & D this mix will have already been Articles in this series been engaged in R & D at a com- manager. Also, as with Sir Stan- gathered from the accounts given parable level will realise the full ley Hooker, he was a brilliant earlier in this series and more British invention, innovation import of this quotation from 'Sci- mathematician. particularly from this article. and electronics (March) ence at War', not least the In rounding off this section, the There is perhaps one aspect Radar and television - soundness of the way of thinking word 'mix' has been chosen to which might be elaborated - rel- interchange and spin -off (April) it represents. cover two specific and interlinked ations with the local industry- The post war stride into The account that follows of the issues in the conduct of technol- based cluster. This has already aerospace (May) work on the ten - centimetre front ogy in the UK. Both of these been mentioned with the refer- R & D management and continues to show the same pat- issues will be considered from the ence to the Manchester economics tern of high- technology national point of view, and in the University contribution to corn - Big system automation and achievement, and specifically the case of the first largely from that puters; and, in line with the telemetry transfer to manufacture by GEC of the 'total' education of the indi- preceding treatment it seems Vehicle instrumentation with " --no inconsiderable part" vidual. Thus, as an illustration, appropriate to couple the name Human communications played by B.T.H. and by virtue of the dovu- Ferranti with the Manchester The future As found by all who write on mentation that exists on his computer mix. & WORLD JUNE 1985 42 ELECTRONICS WIRELESS

www.americanradiohistory.com by James Miller B.Sc. Helical antennas for G3RUH 435MHz An easy -to- construct design offering true circular polarization

This antenna design was pro- of reasonable size (Fig. 1). These is not critical and 500mm square duced for satellite working with gains are typically 3dB lower than could be used if windage is a prob- Oscar -10, but it has also proved Kraus gives, but seem to be re- lem. Take especial care to cut the excellent for ordinary local and presentative of actual practice. Expamet sheet without leaving long-distance operation. It has jagged edges. eliminated at a stroke the frustra- The mesh must be stiffened, or tion of accurately matching and Materials it will bend easily in a light breeze phasing crossed Yagis to true cir- and may quickly break. In one cular polarization and obtaining In choosing materials I was prototype the support/stiffening guided by the need to make an an acceptable s.w.r. throughout was fabricated from a 100 x antenna that could survive the band. 100mm 16 s.w.g. (1.6mm) cen- several years' weathering with Compared with other antennas tre plate and some 10 x 10mm 18 only minor attention; and it has a very wide bandwidth - a that for s.w.g. (1.2mm) aluminium the most part used low Q - which makes it forgiving common angle, and was quite satisfactor- material and needed of dimensional inaccuracies. It is simple ily strong and lightweight. workshop practice. I did not con- therefore easy to construct suc- For the final version model I sider timber stable enough - but cessfully. tried a simpler you could try it. design, bent up This article describes 9 and 16- entirely from 18 s.w.g. sheet The reflector and boom are alu- turn helices for the 430- 440MHz metal (Fig. 2, 3). The stiffening minium and the helix copper. The is amateur band. The nine -turn bolted through the mesh with M3 feed -strap is brass and the screws version simply has fewer turns X 10 screws and stiffnuts, using are zinc -plated. The spacers are and spacers, but it is short 16mm diameter washers on the of black Delrin. A waterproof enough to permit end -mounting. front face, cut from waste metal. N -type connector is used for the Gain figures of the two versions To keep the reflector r.f. connection. For protection, all- alumi- are 12.8 and 15.2dB respect- nium, 3mm (e ") pop rivets could ively. You can use more turns, the completed antenna should be varnished. be used instead of screws. but the mechanical penalties Once the stiffening is fixed, To ensure success, it is increase rapidly at this wave- mesh can be snipped away to Fig. 1. Gain important to do things in the right versus number of length, whilst the extra gain per allow the boom and N -type con- for order: for example, the length to turns helical antennas turn is marginal. nector through. The connector is which the spacers must be cut having a pitch angle of 12.8° For many years Kraus' has a single - hole -fixing type and can and circumference depends on the final diameter of of 1.08 been a central figure in promoting be fitted either way the helix. Handling the helix itself round (based on curves in reference helix antennas, and a little detec- depending on whether the feed is 2). The calls for a boom through its mid- 9 and 16 -turn tive work reveals dimensions to be from the rear or along dle and so it is easier to the designs described here have identical to his figures in almost do drilling boom from front. first. So: the gains of 12.8dB and 15.2dB every design guide (for example Aluminium tube 19mm square respectively. At 435MHz, obtain all materials see the R. S. G. B . VHF /UHF Manual, - and of 16 s.w.g. wall is obtainable table 3; longer antennas would need ITT Reference Data for Radio from most ironmongers or non- a stronger boom. Engineers etc.). build up the reflector assem- bly; More recently, King and Wong 18 in their brief summary papera drill the boom; presented performance charac- wind the helix and stretch teristics based on a large number along the boom; of gain and pattern measure- make and fit spacers; ments of helices of 5 to 35 turns, fix the copper spiral to spac- with various pitch angles and ers; other parameters. The paper fix reflector to boom; augments and expands Kraus's install feed strap; 14 theories. adjust s.w.r. //"V°.°*'=1-0 The design of this antenna is a=12.8° based on that work. A pitch angle Reflector 12 of 12.8° with a circumference of about 1.08 wavelengths are The reflector is a nominally used. From King and Wong's 600mm square piece of expanded curves this yields a maximum aluminium fret, obtainable as 10 15 20 25 30 gain (allowing for mechanical tol- Expamet 351A, which is widely NUMBER OF TURNS erances) at 435MHz, for aerials used as a grille material. The size

ELECTRONICS & WIRELESS WORLD JUNE 1985 43

www.americanradiohistory.com HELICAL ANTENNAS

318

308

10 39

72 35 REFLECTOR SUPPORT 90 2 REQUIRED

89

447 BRACKET

467 2 REQUIRED

Material - Aluminium sheet 18 swg All unmarked holes are 4 dia All dimensions are millimetres

is ferrous metal suppliers. You will spacer is a quarter -turn into the Fig.2. Reflector support Helix fabricated from 18 s.w.g. need two or three metres, which helix; the last supports the end of aluminium sheet; two of each will allow you a little surplus at the final turn. part are needed. Assemble as each end to clamp the boom for First drill the spacer holes. The helix is made from 10mm shown in Fig.3. The parts are support during construction. Position the reflector mounting diameter copper central- heating fixed through the reflector Drill holes of 4.3mm diameter holes so as to locate the front face pipe, which is readily available, mesh with twelve 1Omm M3 for the spacers and to secure the of the reflector 53mm from the easy to bend by hand and quite screws and stiff-nuts, backed relector (see Fig.4). Spacers are first spacer hole. This will ensure cheap. It usually comes in 10 or with 16mm diameter used every 1.75 turns: the holes an adjustment gap of about 5mm 20m coils. Each turn takes 0.7m, washers cut from waste must therefore be alternately between the reflector and the so you can get up to 13 turns out aluminium. vertical and horizontal on a 3.5 start of the helix. of a 10m length; 20m will make turn (595mm) pitch. The first two antennas, one of nine turns and one of 16. If you can obtain odd lengths from a plumber then the pieces can be soldered Particular thanks to Francis Pullen together. Do not uncoil the raw for machining services dur- G4XXX tubing before winding. ing the development of this You will need a mandrel around antenna, and to Cambridge Con- which to wind the helix. It should sultants Limited for the free use of have a diameter of 229mm and, facilities. for comfort, a length of at least 180mm. A search around your attic, scrapyard or the shops may well produce a suitable object. I Fig.3. Rear view of the found a nine -inch cake tin exactly reflector showing assembly the right diameter though a little of support parts. Rear feed short, and I was able to wind the may be obtained by reversing first prototype, somewhat the N -type connector and unevenly, using two pairs of omitting the feedthrough hands and a lot of patience. For insulator. Anti -static subsequent models this experi- protection (not shown) can be ence prompted me to make up a effected with a small inductor proper drum of the correct size from connector pip to a out of two plywood discs and solder tag on the boom. some slats.

44 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com Table 1: measured performance data Table 3: materials

Quantities for a 16 -turn helix [figures Size 9 16 turns in brackets are for nine turns]: Sain 12.8 15.2dB Reflector: 3dB beamwidth 311° Expamet 351A expanded aluminium mesh, about 600 x 600mm First nulls *23° Support /stiffeners fabricated from 500 x 250mm 18 s.w.g. aluminium sheet Typ. sidelobe -18dB 12 M3 x 10 pan -head screws and stiffnuts, plated 12 16mm diameter washers F/b ratio 14dB drilled 3.3mm, cut from aluminium waste 2 M4 x 30 pan -head screws and stiffnuts (typ.) S.w.r. less than 1.1:1 1 N -type socket e.g. Cirkit (formerly Ambit) part no. 10 -01301 Overall length 1.59 2.78m 1 feedthrough insulator, 4mm dia. x 13.7mm e.g. Sealectro type FT31OP51 Weight incl. 2.7 4.0kg clamp Booms 3 [1.8] metres aluminium tube, 19 x 19mm section, 16 s.w.g. wall thickness 2 19mm square plastic end plugs - e.g. Dexion finishers 1 antenna clamp, double U -bolt type, e.g. Jaybeam type 9891 or similar Table 2: electrical and mechanical design Helix: 13 C7] metres 1Omm diameter copper micro -bore central heating tube Frequency 430- 440MHz 1 lOmm end cap, e.g. Yorkshire type 61 Wavelength = 690mm nominal Spacers: Fitch angle p = 12.8 °, circumference C = l. 08T 1.2 10.77 metres 16mm diameter black Delrin rod 10 [6] M4 x 30 screws, pan -head, plated

Feed strap: 100 x 7mm 16 s.w.g. brass strip symbol wavelengths size, mm The following parts may be obtained from the author:

1. Pre- formed Circumference C 1.08 745 reflector support /stiffeners, screws, nuts, and washers: £15 per set. Diameter = D C/,r 0.344 237 2. Machined spacers with screw: £2.30 each. Turn length Lt = C/cos(p) 1.108 764 Turn spacing S = C tan(p) 0.245 170 Complete antennas and kits are also available to special order. Prices Tube diameter d 0.014 10 include carriage to U.K. addresses only. For more details, please send a Reflector stamped, self- addressed envelope to J.R. Miller, 3 Benny's Way, Coton, 0.87 600 x 600 Cambridge, CB3 7PS.

There is no need to worry if the stop and inspect your work. down firmly mandrel is not exactly 229mm in Make absolutely sure you are Support the boom at each end. diameter, but be sure to err on winding a right -hand or left -hand Mark the location of the first and the small side, since the design is spiral as you really want. If in last turns on the boom (1.53 or already close to the maximum doubt, compare it with a normal 2.27m apart) boldly, with black size for 440MHz. If your helix woodscrew. Most people tape. diameter ends up N mm less than instinctively wind left- handed Now slip the coiled helix over nominal, then simply make the spirals. the boom. With an assistant hold- spacers (N /2)mm shorter. Continue to close wind the cop- ing one end, draw the other, Start winding about half a per until you have 9 or 16 tightly gently stretching the coils apart, metre into coil. Holding the short coiled turns. The helix will spring keeping the top markers vertical end tight against the mandrel, out naturally to the desired until the full extent is reached. pointing away from you, pull the (coiled) diameter of about Take care to avoid distorting the long end down on to the mandrel 253mm outside. first and last turns through rough into a curve. Slip the helix back an handling. eighth of a turn and bend again. In Stretching You should now have a fairly Fig.4. Boom drilling. Material this way a whole turn can be built even helix with the correct aver- is 19X19mm aluminium up smoothly and will start gripp- First mark the top of each turn: age spacing of 170mm and nomi- tube. The reflector is secured ing the mandrel as soon as ten- stick black tape along the outside nal o.d. of 247mm. via two vertical holes to sion is applied. of the coil, slit the tape between prevent twisting; spacers are After winding the first turn, turns and smooth each marker used every 1.75 turns.

16turn aerial 2784, [9t 15941

95.5 9pitches of 2975 (16t) [5pitches of 297.5 (9f)]

BOOM: 1 REQUIRED 11

TOP

t....--Reflector °)S1 Spacer i etc. S2 S4 S5 S6,[9turn] 53 S10, 16 turn

1

SIDE r -_f -

All holes - 4'3 di a. Material - Aluminium hollow section All dimensions are millimetres 19x19 with 16swg walls

ELECTRONICS & WIRELESS WORLD JUNE 1985 45

www.americanradiohistory.com HELICAL ANTENNAS

the start of the helix down direct The nine-turn antenna can be ' sot to the connector (for rear feed). fixed in the same way, or end - is mounted with a counterbalance 10.1 dia. The spacers are made from For front feed, the strap about 16mm extruded black Delrin rod, 85mm long and runs to a feed - weight of moment 1.7kg.m which can be obtained from plas- through insulator mounted on the referred to the clamp. (Front -end tics suppliers listed in the classi- reflector support. It is linked by sag will be 20mm again). fied telephone directory; but any an 18 s.w.g. insulated copper Using a metal mast through the ultra -violet and weather=resis- wire across to the connector pip. helix seems to produce no ill tant loss -free material could be Carefully squash flat about effect. Glass -fibre masts are used instead. Cross sections of 10mm of the start of the helix so becoming more common, but the spacers are shown in Fig.5. that the strap can be soldered unfortunately are still expensive. They can be made by hand using a flat, close and parallel to the ref- The antenna's finish can be 109 117 saw and drill, though a lot of care lector. The tube can be sealed up preserved with a coat of yacht will be needed; I used a lathe. You at the same time. varnish. This will flake off if the will needs six or ten spacers. If a large soldering iron or metalwork in not first degreased The slot in the top is wide blowtorch is available, a 10mm using hot soapy water, blue Ajax enough to allow the copper tube copper end -cap makes a neat fin- or Inhibisol. to be snapped into place. Other ish for the front end of the helix; This type of antenna inevitably S' methods of mounting may be just but while fitting it, temporarily picks up a static charge which will $11-1 as effective, though. One possib- remove the leading spacer from damage pre -amplifiers or receiv- ility is a V- notch, with the tube the heat. ers that do not have a low input Tap M4 x 12 deep secured by a couple of turns of 18 resistance to d.c. Check your s.w.g. copper wire (as used in Tuning system! A simple protector would be a 4.7kS2 1W resistor 16 dia. mains power wiring) via a small hole drilled beneath the notch. First make sure that all screws from connector pip to boom, are tight. Using an s.w.r. bridge, I have tried, or Dims. are mm Whichever method is used, the which not small tube centre must be supported adjust the spacing between strap inductor in the same place, (say Material - Delrin rod 109mm above the boom surface, and reflector, gently bending the 300nH, a few turns), which I first quarter turn as needed. The SPACER allowing for any error in the have. You are warned! gap should be about 3mm. [6] or 10 READ. dimensions of the spiral. Fix the spacers loosely to the Relieve any stress at the connec- tor or feed -through by re- melting Performance Fig.5. Spacers are machined boom in such a way that the start turn will be uppermost. Lift the the solder. from 16mm black Delrin rod Tuning can be done at ground I would have welcomed an oppor- helix on to the top spacers at 2,9 tunity to evaluate the antenna on and are fitted at 11/4 - turn level, with the antenna on a two - and 16 turns, guided by the mark- lacking intervals. The helix structure In fact, after the a proper test range, but ers, and secure it. Next, fix the metre pole. snaps into the slot. A vee- indoors, little both of these I had to devise spiral at the bottom, and then at initial adjustments notch may be used as an further tuning seems to be another method. My local u.h.f. alternative to the slot and the sides. repeater is fortunately only 1km Fine adjustment of spacing needed when the aerial is taken hole illustrated here: the outside. distant and it provides a strong, may be needed to correct any dis- line -of signal. I copper is then secured by Use no more then 5W when steady -sight tortion. Make up a 160mm -long in wire passed through a small experimenting, and remember rotated the antenna small gauge from a strip of metal: it hole beneath the notch. the e.i.r.p. at the sharp end is increments and measured the should just slip between the response using a calibrated 1GHz turns. high: avoid prolonged exposure. With care a virtually perfect variable attenuator. Now bolt on the reflector from 430 With this test I was able to Fig.6. The feed strap: an assembly. match can be achieved to 440MHz. assess the nulls and sidelobes, accurate match is found by and by graphically integrating the adjusting the spacing Feed strap polar plot3I arrived at an estimate Installation between strap and reflector. of the gain achieved (table 1). An s.w.r. of better than 1.1:1 This consists of a strip of 16 can be obtained easily over s.w.g. brass, 7mm wide and In a gale the force acting on the In actual practice, perform- 430-440MHz. about 100mm long running from reflector is very high, and results ance has surpassed my expecta- in a considerable torque at the tion. Oscar -10 working has been clamp. Therefore pay special transformed since my crossed attention to this fixing point. Use Yagis were replaced. Terrestrial a double U -bolt design and install working is excellent, the circular with care. If in doubt run an M8 polarization eliminating the need bolt right through clamp and for dual feeds, changeover relays mast. There is just room. and the like. Of course there is a Consider also the parking posi- 3dB penalty for using circular tion when the aerial is not in use. instead of linear, but does anyone Small rotators such as the Hirsch - actually notice? The polarization mann 250 are not really suitable from mobile signals constantly for the 16 -turn antenna. Windage changes, and circular polariza- can be reduced by cutting the re- tion should actually be better flector to a 500 X 500mm square than vertical alone. or to a circular pattern. The prototype has been in use The centre of gravity of the 16- since December 1983, and apart turn antenna is about 6.7 turns from the redesigned reflector stif- along the boom, and at this point fening has needed no attention. the bending moment of 1.6kg.m Without doubt it has been one of results in a 20mm sag at each the easiest antennas of all to end, which is quite acceptable. design and build. 46 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com LANGREX SUPPLIES LTD Climax House, Fallsbrook Rd., Streatham, London SW 16 6ED RST Tel:01 -677 2424 Telex: 946708 RST JC1vIll.V1111JVl.r I Li 11a 0E257 11.27 GEX541 5.N UAZ207 LSO OC205 2.75 Z11(504 021 2N1671 300 1N3819 030 AA119 0.10 BD132 0.4 0F258 0.27 GJ3M 1.50 0C16 2.50 0C2% 2.75 ZTX531 0.24 2N1893 9.32 2N3820 0.39 AS Y27 0.90 BC173 O.tl BDI35 MY30 0.17 AS215 1.20 0.40 0E259 0.28 GM0378A 1.75 OC20 2.50 OC207 2.50 ZTX550 0.25 2N2147 4.00 2N3823 O.N MY30 0.17 BC177 0.2[ BD136 1.10 0.40 BF336 0.54 KS180A 0.45 0C22 2.59 OCP71 2.10 IN911 O.OS 2N214 3.75 1N3866 AAZ13 0.15 16 BD137 1.N 0.40 0E337 0.33 M E340 0.N 0C23 4.90 ORP12 I.N 1N916 OM 2N2218 0.32 2N3904 0.17 AAZIS 0.15 BC9 C.3218 BDI38 0.48 0F338 0.36 ASZ20 2.30 BC182 M E370 0.73 0C24 3.90 R200813 2.00 1N4001 0.N 2N2219 0.32 2N3905 0.17 M217 0.15 0.11 9D139 0.49 8E521 4.00 ASZ21 2.0 BC183 0.11 M E371 0.71 0C25 1.N 92009 2.25 1N4002 0.N 2N2220 0.20 2N3906 0.17 AUYIO 3.00 BC184 O.11 9.20100 2N4058 0.20 AC125 0.25 BD244 2.00 13F561 0.20 M E52Ì 0.73 OC28 2.N C44 2N2222 9.20 AC126 027 1N4004 0.07 0.25 BDI81 1.20 0E598 0.21 M E2955 1.00 0C29 2.00 T1C226D 1.20 INI005 0.09 2N2223 4.25 jpNj ÿ, AC127 0.25 gA148 0.15 BC213 0.11 BD183 0.99 BFWIO 0.97 BAI54 0.10 BC211 0.11 M E3055 1.10 0C35 1.50 TIL209 1.16 1N4006 0.11 2N2368 0.25 2N4061 9.14 AC128 0.30 BD2137 0.54 BFW11 0.96 F102 0.35 BAI55 0.11 BC237 0.11 .0C36 1.50 T1P294 0.43 1N4007 0.12 2N2369A 0.25 2N1062 9.16 AC141 0.21 BD238 0.54 BFX84 0.30 MPF103 0.35 BAI56 0.10 BC238 0.11 0C41 0.% TIP30A 0.45 1N4009 0.07 2N2484 0.25 2144121 0.16 AC141K 0.35 BDX10 0.91 BFX85 030 0.35 BAW62 0.15 BC301 0.33 MPFI04 0C42 0.90 T1P3IA 033 1N4148 0.04 2N2646 0.50 2N4126 9.16 AC142 0.28 BDX32 2.00 BFX87 0.30 MPF105 0.35 0C43 1.50 T1P32A 0.36 2N540 0.13 2N2904 1.32 ACI42K 0.35 BAX13 0.06 BC303 0.31 BDY20 1.S0 2N4286 1.15 BFX88 0.30 MPSA06 0.26 0C44 0.85 T1P33A 1.51 1145401 1.13 2N2905 0.32 2N4288 9.18 AC176 0.30 BAX16 0.06 9C307 0.11 BDY60 2.75 BFY50 0.25 BC107 0.16 BC308 0.11 MPSA56 0.28 0C45 0.65 T1P344 0.67 1S44 6.N 2N2906 021 2N4289 0.18 ACI87 0.21 0F115 0.35 BFY51 0.25 0.53 BC108 0.16 BC327 0.12 MPSU01 0071 0.55 T1P414 044 1S920 0.99 2N2907 9.11 2N4400 0.11 AC188 0.28 0F152 0.16 BFY52 0.25 0.65 OCIOS 0.16 BC328 0.12 MPSU06 0072 1.0 T1P42A 0.42 15921 0.09 2N2924 0.26 2N4401 0.11 ACY17 1.30 0F153 0.16 BFY64 030 MPSU56 0.69 0073 1.00 T1P2955 0.70 2N2925 0.22 ACY18 BC113 0.15 BC337 0.12 2G301 1.N 2N4402 9.11 1.15 11E154 0.17 BFY90 0.95 NE555 0.45 0074 0.70 T1P3055 0.56 2G302 1.00 2N2926 0.15 ACY19 1.10 BC114 0.15 BC338 0.12 0F159 0.17 BSX19 0.27 2N5457 032 BCIIS NKT401 3.50 0075 0.6S 25140 0.25 2G306 1.90 2N3053 0.26 2N5458 0.32 ACY20 1.10 0.18 BCY30 1.25 BF160 0.17 BSX20 027 BC116 0.19 BCY31 1.50 NKT403 2.50 0076 1.10 25170 0.21 2N404 1.30 2N3054 055 2N5459 0.32 ACY21 1.15 0F167 0.24 BSX21 0.29 NKT404 BC117 0.13 BCY32 1.50 2.20 0077 1.00 25178 0.54 2N696 032 2N3055 0.65 25017 10.90 ACY39 2.50 0F173 0.30 BT106 1.20 0A5 1.20 0081 0.65 0.32 2N3440 0.71 AD149 25271 0.23 2N697 2019 12.N 075 0F177 0.35 BTY79/4OR 0A7 OCBIZ 1.10 2N698 0.32 2N3441 1.85 AD161 BC125 0.18 BCY34 1.00 040 ZS278 0.57 25024 35.00 035 0F178 0.35 2.00 0A10 0.55 0082 9.90 ZTX107 2N705 1.25 2N3442 1.25 25025 35.00 AD162 0.35 BC126 0.18 BCY39 3.40 0F179 0.35 0.12 BU205 1.30 0A47 0.12 0083 1.14 ZTX108 1.12 214706 0.25 2N3614 2.20 25026 35.00 ADZ11 12.50 BC135 0.15 BCY40 2.80 BEIM 0.28 BU206 1.50 0A70 90:136 0.19 8CY42 0.30 0.25 OC/4 0.00 ZTX109 9.12 2N708 0.25 2N3702 0.11 25103 1.50 ADZ12 12.50 BF181 0.28 0U208 200 0A79 0.12 0C122 2.7S ZTX300 013 2N930 0.25 2N3703 031 25302 3.50 AF106 9.35 BC137 0.19 BCY,3 0.30 0F182 0.30 BY100 0.40 BC147 OAS 0.17 0C123 2.99 ZTX301 0.14 2N1131 0.30 2N3704 011 25303 1.50 AF114 3.50 012 OCY58 0.19 0E183 0.28 BY126 0.13 0.17 BC] 48 BCY70 0A85 0C139 310 ZTX302 0.18 2N1132 0.30 2N3705 0.11 25322 3.50 AFII5 3.50 0.12 0.17 0F184 0.28 9Y127 0.14 0A90 0.90 BC149 9.13 BCY71 0.18 OC140 4.00 2TX303 1.18 2N1302 1.20 2N3706 0.11 25324 3.50 AF116 3.50 0F285 030 82X61 0.17 0.99 0C141 BCI57 1.13 9CY72 0.17 OAS 4.25 ZTX301 0.20 2N1303 0.90 2N3707 011 25701 3.50 AF117 3.50 0F194 0.11 Series 0A95 0.99 0C170 BC158 0.13 1.75 4.50 ZTX311 0.13 2N1304 1.20 2N3708 010 25745A 0.95 AF139 033 BCZII 8E195 0.12 BZY88 0.10 0.15 OC171 BC159 0.13 BD115 0.42 0A20 4.50 21X314 025 2N1305 116 2N3709 0.11 25716A 0.95 AF156 1.00 8F196 0.13 Series 0A202 0.15 OC20 1.50 2N3710 0.10 BC167 0.11 BD121 1.70 ZTXSN 0.14 2N1306 1.0 CV Devices AF239 0.39 OF197 0.14 CRS1/40 0.60 0A211 1.50 0C201 3.75 2N3711 8C170 0.11 BD123 1.80 ZTX501 0.14 2N1307 1.10 010 Large stocks AFZII 4.00 BF200 0.40 CR53/40 0.75 0A2200 1.S0 00202 2.75 2N3771 1.40 8C171 0.11 BD124 2.00 ZTX502 0.18 2N1308 1.75 Prices on AFZ12 4.00 BF221 0.25 CRS3/60 0.90 0A2201 1.50 0C203 3.00 2N3772 1.60 0.11 0.44 217t503 0.39 2N1309 1.20 app0után i.,.ASY26_ LN_ BC172 BD131 BF244 35p GEX66 3.00 OAZ206 1.50 OC204 3.00 2N1613 032 2N3773 I.N GXUI 15.35 OD3 2.50 QY3-65 63.24 UF41 2.90 4-250A N.N 6CG7 2.51 12AX7 1.75 5642 9.14 VALVES EIBOCC 10.50 EF89 2.50 GXU2 30.00 0..1 3.50 QY3-125 68.64 UF42 2.14 4-40A 17.N 6CH6 13.M 124Y7A 4.99 5654 3.N A1834 9.10 E180F 10.20 EF91 2.95 GXU3 25.40 PC86 2.50 OYa-2511 70.14 VFW 1.75 4032 20.00 60L0 3.75 12B4A 3.50 5651 4.45 A2087 13.50 E182CC 13.25 EF92 6.37 GXU4 44.50 P(-00 2-91 QY4-4181 76.20 UF85 1.75 4C35 120.00 6CW4 0.09 12BA6 2.50 5670 4.51 A2134 17.50 E186F 11.50 EF93 1.50 GXU50 20.00 PC95 1.75 01,5-510 190.00 11E89 2.00 4CX25013 58.00 6D2 1.51 1213E6 2.50 5675 21.90 A2293 16.00 E188CC 8.91 EF94 2.50 GY501 3.00 PC97 1.75 QY5-300A UL41 5.00 4CX350A 128H7 2.75 105.00 I 6DK6 3.90 5687 6.90 E280F 22.51 EF95 5.99 A2426 27.50 GZ32 1.00 PC900 1.75 450.00 0L84 1.75 1X 150A 66.60 6 I%J6B 4.75 12817 3.90 5696 4.51 A2521 25.00 E283CC 12.00 EF98 2.90 GZ33 4.75 PCC84 1.50 QZa-20 32.70 UM80 2.90 /X150D K.00 6EA8 1.90 12EI 20.00 5718 7.51 A2900 15.10 E288CC 17.50 EF183 2.N GZ31 3.0 PCC85 1.50 RIO 6.00 UY41 2.25 5B254M 35.00 6E130 2.50 12E1 ITT 21.10 5725 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2.50 518142 TT 100 60.00 ZM1041 16.66 6AN8A 3.50 6P25 1.N 85A2 6.45 60979 Nam 0F96 1.75 ECC84 1.75 EM80 2.50 8.75 PL36 2,50 7y2.125 M8144 7.50 65.00 ZM1042 17.77 6AQ5 2.25 1.75 ECC85 1.75 EMS 2.50 PLBI 1.75 DK91 TY4-400 80.00 193GT 3.99 6AS6 8.66 6R7 3.25 90AV. 20.00 . 6146B 12.00 13092 2.00 ECC86 2.50 MN 2.99 M81,9 6.50 PL81A 2.00 M8161 9.35 TY4-500 105.00 11324 25.90 6AS7G 1.75 6SA7 3.01 90CI 600 61598 19.90 0K% 1.75 ECU!' 3.50 EM85 2.75 PL82 1.50 M8162 10.40 TY5-500 214.00 1835A 4.90 6AT6 1.25 6SC7 2.75 9000 14.54 6189 9.50 DL92 200 ECC89 2.99 EM87 2.50 PL83 2.50 TY6-800210.00 1963 61.90 6AUSGT 5.90 6SF7 2.50 90CV 15.45 6201 11.40 ECC91 8.93 EN32 17.46 M816J 8.25 PL84 2.00 92AG DL94 1.75 M8190 5.00 TY6-5000A 195 1.75 6AU6 2.50 65147 3.09 20.00 6442 21.99 DL96 1.75 ECC189 2.10 ENSI 6.50 PL504,5 2.50 190.00 155 1.75 6AV5GA 4.50 6917 3.25 92AV 21 .10 65830 0.25 14.00 ECCB07 1.75 01492 6.96 M8195 10.05 PL508 2.50 DLSIO M81% 7.50 TY6-5000B 174 1.75 6AV6 1.50 6.51(7 3.50 95A1 8.45 6973 4.50 DLSIS 12.59 ECC808 1.00 EY51 2.75 PL5U9 6.00 M8204 7.05 395.00 2ASI5 11.50 6AICSGT 3.90 6SK7GT 310 15082 8. S9 7025 3.N DLS16 12.50 ECM 1.50 EY81 2.50 PLS19 6.00 TY6-5000W M8212 11.37 2C39A N.M 697 3.25 6SN7GT 3.N 150B3 6.15 7551 8.21 DL519 12.50 ECF82 1.50 EY83 2.10 PL8O1 1.50 115.00 2041 70.00 688 1.25 6SQ7 3.40 150C2 3.25 7586 15.00 DM70 2.00 ECF86 2.50 EY84 9.24 M8223 6.N PL802 6.00 M8224 6.30 TY7-6000A 21321 3.15 60A6 1.51 6SR7 4.90 150C1 6.90 7587 23.04 DM71 2.00 ECH35 3.00 EY06 1.75 PY33 2.50 525.00 M8225 1.50 2E26 0.25 6BA7 5.1111 6SS7 2.75 211 35.90 7609 56.90 DM160 4.75 ECH42 3.50 EY88 1.75 PY81 1.50 348244 14.03 TY7-6000W 2 I2 98.00 613A84 4.90 6USG 3.54 723AB 125.99 7100 6.00 1.50 ECH81 3.4111 EY500A 3.90 PY82 15e DY87 115.00 525.00 2J55 175.1141 NCI 4.90 6UOA 2.25 803 25.15 7895 12.90 DY802 1.50 ECH83 2.50 EY802 1.75 PY83 1.25 MUl210I TZ40 25.00 2J70A 363,99 6006 1.54 6V66T 2.25 805 45.M 8005 114.40 ESSL 45.00 ECH84 2.50 FZ35 1.75 PYBB 2.00 U18-ZO 3.50 34X119 55.10 2J700 336.00 613H6 2.59 6X4 2.14 007 375 9068 14.34 E80CC 8.81 ECM/ 1.51 F240 2.51 PYSOA 4.00 Ut9 13.75 2K25 125.00 6826 2.25 6XSGT 1.75 811A 1833 8122 100.00 11.27 ECUI 1.75 EZ41 2.51 ".`,,,,..1.1j 76.09 PY80 1.50 E80CF 56.70 U25 2.50 3-400Z 113.00 69K4 4.59 797 2.50 012A 29.50 8136 2.50 E80F 14.19 ECU2 1.51 EZ80 1.50 PY801 1.50 U26 2.50 17.25 3.500Z 100.00 66U tS.M 7C5 4.99 813 valve 65.00 8417 6.01 E80L 13.73 ECUl 3.« EZ81 MXISI QF451 82.50 1.51 34X152 131.25 U37 12.00 3A5 3.09 69L7GT 1.59 7C6 2.56 833A 193.16 18042 11.53 E81CC 8.00 ECL84 1.31 U90 2.00 OQV02-6 31.80 1.51 3.51 34X161 152.25 UABC80 1.25 3024 11.10 613346 115.99 7347 1.99 8664 21.03 10045 19.49 EBIL 13.27 FxUS FW4500 QQV03-1023.50 UAF42 2.50 3028 15.35 613N6 2.90 757 4.25 872A 21.99 EöIOF J5.4 ECU6 1.75 FW410 3.51 MX163 20.25 lJQV03-20A MX164 25.52 UBII 3.10 3829 21.05 6BQ7A 3.11 7S7 3.50 922 6.99 Tested E82CC 8.10 EF37A 5.10 G1371K 35.M 438 UBC41 2.25 V.50 931A 18.50 MX166 147.00 3B240M 6BR7 f.N 7Y1 2.25 Ex-Fqui p n[ E83CC 8.40 EF39 2.75 G551K I2.00 QQV06-40A UBF89 1.50 39241M 17.50 6BR8A 3.50 7Z4 3.« 1624 4.90 4CX250B 6.54 E86C 8.25 EF40 5.99 0180.2M 17.50 MXI68 '75.00 UCC84 1.75 N78 IS.N 3C23 25.81 6957 6.99 11E3 55.90 1625 3.50 CV Devices E88C 8.25 EF4I 3.50 G240.2D 12.00 WVO7-50 69.74 UCC85 1.85 3C45 21.50 69W6 f.90 12AH8 1.90 2050 7.50 OA2 3.25 11QZU6-WA Large stocks E88CC 042 EF42 4.50 G400.IK 17.56 UCF80 2.00 30XI00A5i47.N 69W7 LSO 12AT6 1.51 4212E 1M.M Rues on E90CC 9.47 EF50 2.50 GN4 9.09 62.20 UCH42 2.50 OA4 6.14 3E29 45.00 68X7GT S.M 12AT7 1.75 4212H MEN application E9OF 9.90 EF54 5.90 GN4A 9.90 QU37 12.50 UCH81 2.50 354 2.00 68Z6 5544 81.97 OB2 4.31 QV03-12 2.75 12AU6 2.50 E91H 6.25 EF55 3.50 GSI6 16.00 6.99 UCL82 1.75 3V4 1.75 6C4 1.25 12AU7 1.75 5545 165.99 E92CC 8.75 EFN 1.75 GT1C 25.00 2.50 QV0F7 3.50 UCL83 2.75 0C2 465A 00.M 6C86A 2.50 12AV6 2.50 5551A 114.90 E99F 9.10 EF33 4.00 GU50 20.00 OV08.10 171.20 4-125A N.90 6C060A 5.M 12AV7 3.50 EF85 1.75 3 5552A 155.35 GU51 20.00 INTEGRATED CIRCUITS 7495 0.73 74136 /51 74175 112 TBA520Q 2.39 74% 1.82 74141 1.N 74176 I.I6 T8A530 1.10 7400 1.16 7423 0.33 7460 0.10 7497 3.15 74142 2.30 74178 1.36 SADPI 55.00 VCRSI7B 10.00 7401 TBA540Q 2.30 BASES 0.17 7425 0.30 7470 1.30 74100 1.54 74143 2.61 74179 1.36 TOA550Q 3.22 CRTs SCPI 10.00 VCR517C U« 7402 0.17 7427 0.30 74107 0.45 74144 2AP1 6.59 SCPIA 40.00 7472 6.33 2.N 74180 1.20 TBA56000 3.22 7403 9.17 7128 0.13 7473 038 74109 9.73 74145 LIN B7G untamed 0.25 28P1 9.00 5FPI5A 15.90 71100 1.90 TBA673 2.20 87G skirted 1.35 3BP1 11.N 7404 0.18 7430 0.17 7474 0.30 74110 0.51 74147 2.N 74191 1.96 TBA70 1.52 5UP7 25.00 7405 7432 0.30 74111 9.71 7414 1.76 89A unskined 0.25 3DP1 0.11 7475 0.54 74192 1.90 TBA720Q 2.311 5.« DG7-5 63.32 74116 1.85 74150 B9Askined 3EG1 10.00 CRT sockets 7406 9.43 7433 0.40 7476 0.42 1.19 74193 1.90 TBA750Q 2.07 035 DG7-31 St.07 74118 74151 lot Octal 0.35 3FP7 6.00 5t,07 7407 9.43 7437 0.32 7490 0.56 1.N 0.10 74194 1.25 TBA880 1.21 DG7- 7408 0.20 7438 0.32 742 9.75 74119 1.54 74154 1.90 74195 I-ocW 0.55 3GPl 6.00 65.00 p 1.21 TBA920 2.N DG7-36 Opkutàn 0.32 74120 0.83 74155 Nuvista W>< 2.00 3JP1 8.00 7409 9.26 7440 743 1.00 9.99 74196 1.35 TBA920Q 2.99 DH3-92 56.03 74121 Valve screening 3JP2 8.00 I/Csockets 7410 0.17 7441 0.90 7484 1.15 0.43 74156 1.9O 74197 1.35 TBA990Q 2.90 DH7-11 113.12 7412 9.29 7442 0.72 7486 0.39 74121 1.62 74157 0.75 71198 canseOsius 0.40 3LP7 10.0 VCR97 12.00 Texas 2.79 7'CA270Q 2.96 7413 0.32 7447AN 1.17 7490 0.60 71123 1.18 74159 2.211 74199 3 P1 15.00 VCR138 12.90 low profile 2.31 TCA760A 1.31 7416 1.32 7450 9.16 7491 0.92 74125 0.58 74170 2.N TM570 2.39 3RP1 35.00 12.50 8 pin 1 VCRI38A 7417 0.32 7451 1.18 7492 0.60 74116 0.51 74172 4.N TM630S 3WP1 20.00 VCR139A 8.00 14 3.51 PinP lÓp 7420 0.18 7453 6.18 7493 9.60 74128 9.63 74173 1.42 TAA700 3.90 16 pin 10p 7422 0.20 7454 0.10 7494 0.82 74132 9.72 74174 1N TBA4110Q 1.04 Terms of business: CWO. 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by K.L. Smith, D.c. supplies from Ph.D.* a.c. sources -5 * University of Kent at Canterbury Switched -mode supply design

The brief excursion into s.m.p.s. The inductor acts as a true trans- ally works as two 'chokes' principles in Part 1 pointed to the former and a high throughput can because only one winding con- tantalisingly high efficiencies in be obtained with a relatively ducts at any given time. It oper- power conversion they promise. small cross section of core. The ates on a 'bucket- brigade' princi- This means small sizes and mass circuit is suitable for medium and ple: the primary choke stores the in the equipment for a given high powers at low output vol- energy, some of which is throughput, but at the cost of a tages. One disadvantage is the extracted later by the secondary higher component count and requirement for a second induc- at a different pressure and quant- r. f . i . problems . Control and drive tor to store the energy over the ity level, according to the turns circuit complications can be over- 'off' period - tending to put up ratio. The other quantity which come to some extent by means of the cost. But this is compensated adjusts the relative levels is the circuit integration, together with by the resulting low ripple com- duty cycle S, of the switching good filtering, screening and cir- ponent in the output, which waveform, the amount of energy cuit layout to reduce harmonic requires a less stringent filter. stored during the 'on' time vary- interference. Another slight disadvantage is ing with S. The rest of the period the need to recover the magneti- is available to abstract this var- Circuit development zation current (or rather, energy) iable amount of stored energy. in the transformer core during the The third winding on L with D3 The three broad categories of 'off' period. Unlike in the flyback is the one that returns any stored s.m.p.s. circuits are often deve- circuit, the magnetizing current energy with nowhere else to go, loped further than the simple out- does not form part of the output. back to the primary source. This line I discussed before. You will In practice, a similar recovery cir- limits the voltage peaks across find multiple windings on chokes cuit is also used in a flyback the transistor. and transformers, with the mains s.m.p.s. for safety, to limit A simple analysis of how the isolation these provide. Consider spikes and return the magnetiza- circuit operates clarifies the pic- the flyback converter, which tion energy if the load is removed. ture and yields design informa- includes a limiting case, the The inductance of the main tion. To start, there are a few ringing choke converter. Fly - transformer in a forward conver- assumptions to simplify things. backs find the greatest use in low ter is kept high to minimize the One is that the inductance of the and medium level power supplies magnetizing current. A rule of windings on L is large enough to and work well for relatively high thumb is to aim for Im to be about prevent current falling to zero voltage outputs. Figure 1 offers a 10% of the load current. during the 'off period. (It falls to rough breakdown of the useful The third circuit technique zero in the ringing choke conver- power and voltage ranges obtain- uses push -pull or bridge connec- ter). Given L, you will find there able from the various types. tions in the switching stage. is a certain minimum current, Fig.l. Voltage and power One advantage of the flyback There is a number of versions of Io(m,n) to satisfy this requirement. output obtainable from the circuit is the ease of obtaining these, including half bridge or full As we saw in article 2, designers three main classes of multiple outputs (the rectifica- bridge designs. The switch drive write down a quantity called 1I for switched -mode supply. tion is simpler). Disadvantages circuits are necessarily more include the high ripple compo- complex to cope with all the tran- 1e nent in the output and the larger sistors going on and off in the choke required for a given right sequence, but you can 4 throughput. This is because all obtain high and very high the energy has to be stored by the throughput powers, (Fig.1.) The 2 magnetization current flowing in transformers are magnetized in the winding round the core. Of both directions, since the push - 4 interest is that in the ringing pull action reverses the current, choke case, choke utilization is which means that a maximum >4 best. flux swing can be obtained for a >o Double The semiconductor switch and given core. 2 Flyback Flyback Forward and forward_ converter and push -pul - and rectifier diodes have to withstand forward converter push-pull high peak voltages ' converter converter" and currents. Flyback converter Because of these high switching levels, transients and interfer- Figure 2(a) is a two- winding 4 to be larger in ence tend flyback choke version of the circuit. 2 designs. Figure 2(b) shows the waveforms

In comparison, the forward when operating. You might think 1 converter delivers power to the that L looks like a transformer, 1 2 4 10 2 4 102 2 4 1O 2 4 104 output while the switch is 'on'. but in the flyback circuit it actu- Po 1W)

ELECTRONICS & WIRELESS WORLD JUNE 1985 49

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if L is its inductance. The linear from Equation 1. current ramps in L's windings V; .'.1 S mean constant di /dt's. I have V; + n V. defined all the quantities 'by implication' in Fig. 2. So from Also, In = P.V. where P. is the Lp these we can write: - output power. Together with vo this, of course, aá di Dio = Aio dt TS (1 -6)T P (min) VTS Iamin) Aic- Vo Lo and Inserting these quantities and solving for L9(..) gives: NP Vo(1- NT n Ail) Ci N s VZ(I -5)2T L5(min) LS(nun) 2 Referring everything to the input Pa min) side by using Ai, = rlOiC and Ls = ( V le T Lp /n° enables us to eliminate T, -Vo \V; +nVo/ 2 Po(min) the inductances and Dic, Ai, from This Or in terms of Lp(min), VCE the previous two equations. yields, ( VnVP 12 T I ,(min)- V, + n Vn/ 2 Pamin) (2) Vo-n: áS (1) You can see that there is a defi- Equation 1. shows that the volt - nite Io(m ;n) for constant V. given seconds product in the choke Slow -rise sums to zero over one cycle. In LP(min)' network semiconductor switches particular, it also shows that V. Your must withstand peak values Îc depends on the duty cycle para- and VCE in this application. Find- meter S as well as on the usual 'transformer' turns ratio n:1. ing ÎC is fairly simple: VFaO As you can see from v = Ldi/ Di Î = I1P(ao)+ Po=loVoIiVi dt, to keep v constant over the 2 'off' period, L must be sufficiently LP= 1.4 Ls vi large. This is to make di /dt slow By reflecting through the n:1 î=1D keep the diode current transformer ratio again, this can nVo- enough to going throughout the period. As I be written: =Vi (on) P mentioned, if iD does fall to zero, '14 IC = 'WAVE.) + =nVo ) choke condi- p (off we have the ringing n 2n vo tion. _ Io Vo(I-S)nT Vs = Voioff) Again working in terms of n(I-5) 2 LP 1ís vi con) quantities from Fig. 2 reflected T V;nVo 1Ls(onr) into the primary circuit, you can _PoV+nVQ+ V; nVo 2 LP V; + n Vo (3) 1Lp(av) -n find LP();.) to avoid the ringing choke condition. By equating areas on the iD graph, Finally, for the peak collector

1 to emitter voltage: D D -I n 1 -S VcE V n Vo - TÖ--1--T11-6 1 s + (4) ; Now from this result, if the out- T put current just reaches zero, These equations express gen- then the peak value, ÎD, will just or operation. It is reach, eral, average Fig.2. Two -winding choke a choke or transformer, such that the worst case conditions that Io type of flyback converter at I«M¢N) 2 would see off your devices. 1 (a). Operating waveforms are - MAXIMUM Io -S will occur if shown at (b). As an aside, this gives a useful The worst case Another assumption made is is being drawn when V; is linear growth and decay of cur- result for the peak current in the Po(min) For example if S equal to V;(max) rents in the windings on L. As you rectifier diode. = 0.5 the worst case ÎD = 4I0. In know, switching transistors take n Vo(max) the repetitive peak y CE(max)_ VI(.. )+ a finite time to operate, but other words, IFRM rating of the assume they are very fast for the forward current, and the constraint on LP is: moment. More detailed investi- diode must be equal to or greater than Co. VdmarJ n V le T gation of the current commuta- L 3 1 2I0/(1- S) P(min) n V 2 Poo tion effects and to rise and fall Vi(max) + Pan) (2a) times at the switching edges is a will also be the change Ai, under little complex and will stretch the conditions of minimum On the other hand, Îc(max) will your reasoning. Designers have inductance. occur when Po is running at the consider these effects for peak 2I maximum demand, coincident to Vo(0 0 cal- .'. Olnó with the lowest V. and average switching loss Ls(m)n) 1- S culations. Io be writ- (where should strictly V1(min) +nVo )+ The voltage across any winding Îcimax) =P n ten In(m ;n) here.) We know V o carrying a current i is T di S nVo (V(m)nVol v -L-dt V; +nVo +2 LP \V;(,,,,o) + n Vo/ (3a) 1985 50 ELECTRONICS & WIRELESS WORLD JUNE

www.americanradiohistory.com In order to keep V° constant with varying V;, S will have to T change. A, D V° am.° n V;),,,,,) + n V° V° amer n Vam°) + n V° The 'd.c.' value V; will be at maxi- mum when the mains supply is high and the peak of the 100Hz 4 ripple from the primary full -wave rectification. Conversely, V;(min) ) will occur with a low mains input C NP together with the trough of the = Tr; 100Hz ripple. If the maximum mains r. m. s. voltage is 265 volts, I the V max) might reach 375 volts d.c. If the ripple amplitude is, say, 25 volts peak to peak, then T VCE when the mains is low at 190 volts will be about 244 volts.

Slow -rise Forward converter network

The circuit and waveforms given in Fig.3. enable you to under- stand the operation in a similar way to the flyback converter. I won't go through the analysis, as space hardly permits such a Vi duplication, but to quote a cliché 'it is left as an exercise for the stu- .:.Flux in dent'. A brief note of a few details about the circuit operation and a L quotation of the results for com- Demagnetising parison should help anyone to )D3 Fig.3. Forward converter derive the formulae. Po Vi tY._j-1 - looIíi circuit, with waveforms

The magnetic component T, 7ls = TV,1 (on) at (b). operates as a true transformer. 7),i With Tr 'on', D1 is on and energy (n.tc )l-t 'D1= c is passed through from the input. by Some is stored in L, some flows on to the output load. When T turns off, primary and secondary 1b :IL Ali. (= dlcap) currents, is and iD1 cease. The voltage vL across the choke

reverses, diode DI goes off and 1 'flywheel diode' D2 comes on. -TB----T11 6)-1 The current in choke L 'com- -T mutes' from DI to D2. The mag- netizing current in the transfor- next cycle with a clean slate, as it Îc is also found in a similar way: mer would also stop flowing, - were. The choke L should be (5) since no path now exists V° for it in large enough to keep the current the primary or secondary cir- / nV° (7) going during the 'off' period, for a The criterion for the design of T cuits. An extremely high voltage similar reason to that given for is to make its winding inductance Finally D33 clamps to 2V;, inductive 'kick' occur VCE would' the flyback converter. As you can large enough to keep the magne- across üc -2V; (8) T. Therefore the energy see, current flows through a suffi- tizing current small compared to recovery winding with D3 is ciently large L all the time. In fact the load currents. The energy Precisely similar arguments as essential in this form of conver- it ramps gently (and linearly... ) storage inductor L has a certain before will give you the 'worst - ter. D3 limits vcE to 2V; by up and down. This means the rip- minimum value Lm;n, which will returning the stored magnetic case' magnitudes the devices ple duty for Co is much less strin- keep the current going, down to a would have to handle in practice. energy to the source. gent than the corresponding filter stipulated minimum current out, in flyback Io(m;n). With a to The designer must consider component the circuit, similar approach Will the transformer handle the of Equation 2. for the flyback cir- two limiting requirements. The where bursts current arrive fol- power? transformer core should reach lowed by nothing for a while. cuit: zero magnetization in less time In a similar argument for Equa- Always central to power supply : than the 'off' period of the switch- tion 1. you can show V° and V; rel- V T r design is the question of whether Lm ° Ì l - 2 ing, so that the circuit starts the ate as: Po(min) nn Vl ° / (6) your transformer will burst into ELECTRONICS & WIRELESS WORLD JUNE 1985 51

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VA - ampere -turns X volts per minimizes B and so we have the turn smallest numerator divided by The true transformer action in the largest denominator in Equa- the forward converter means that tion 13. Hence the throughput magnetizing currents can be conditions are explained. ignored for the moment. They Design note. In practice, you can be checked at a later stage in would calculate the windings the design. The d. c. pulse drive is from the minimum supply voltage illustrated in Fig.4, from which, and maximum S( =0.5) condi- the peak primary current is: tions. The volts per turn for the three types of converter work out as: Y° -á (9) R.m.s. current lc is given by: forward converter N- 2 f Fig.4. D.c. drive in a flames. The inductors in z pulse V 4 f cp n no excep- k =fTaTf dtI -Yc flyback converter forward- converter s.m.p.s. systems are N 1 +n transformer. tion. We hope their power to LL weight ratio will be very good, but or in terms of I,: J push -pull circuit -v f cID N -4 they must still handle the VA. L Because forward converters and I Some d.c. flux will occur in a for- flyback circuits deal with the ` (10) ward converter transformer core throughput in different ways, we The transformer efficiency is high - and might occur in an unbal- must consider the inductors (about 96 %) which means: anced push -pull circuit. A slight accordingly. Designing flyback reduction in your chosen can VA rn) -VAtou chokes is quite involved and I be made to take this into account. of have relegated the discussion Equations A5 in Part 2 give the Chokes carrying d.c. such as these to an appendix, (always resistance of the windings. Equa- those in the flyback converter and assuming the Editor can find tions A6 built up a picture of cur- the smoothing chokes in forward room for it...) (next article - Ed.) rent density in the copper and converter and push -pull circuits, The throughput performance power dissipation. We can quote require some thought. The d.c. of a forward converter transfor- via Equation A6(a): component biases the flux in one mer is reasonably simple to ana- direction and the relatively small lyse; you can try your hand with Pw - 2P, m 1a2AwFIw (11) alternating swings go round and the flyback choke later. How- round a minor hysteresis loop. The rate of change of magnetic away with The incremental permeability ever, we cannot get flux gives the volts per turn: only the simple forward conver- might very well be much less than ter or push -pull transformer V dtp the amplitude permeability we design. Both of these circuits NP dt have assumed to apply. The require energy storage chokes in inductance is optimized by using linear of change of Fig.5. Calculating losses due addition to the transformers. The where the rate an air gap in these cases, since a to finite switching times. choke design requires the full 'fly- flux dcp /dt is simply /TS from gap in the magnetic circuit can back -type' analysis - complete Fig. 4. increase the incremental permea- with the appropriate parameter, bility. The best approach would V f be for you to use the appropriate fl. NP 5 (12) Hanna curves for the chosen And from Equations 10 and 12 we core. Forward converter transformer. obtain: áf Switching to new endeavours I will draw on the discussion we VA - VI, - IIAWF,x Fig. 6. Modified waveforms had in Part 2, especially details The efficiency of conversion will where lc has been replaced by the caused by reactances in a given in the appendix there. In only remain high if you endeavour current density Id times the effec- practical circuit. particular, it all starts with: to keep down the dissipation in tive copper area, of the AwFw 2 the switches as well as the trans- primary winding, the number of formers. The primary switch has NP, cancelling. Now turns, sub- been bipolar transistors, but stitute for Id from Equation 11: power fets are challenging this position. We can look upon the VA- (PwAwFw\2 $Aco,ef `\ P,mlw JJ 2,/á (13) steering and rectifier diodes as secondary switches. In all of Or writing in terms of the cooling them, time is required to turn on surface, Ac, and the heat trans- and off. Especially in the diodes, fer, Ph (see Part 2) Equation 13 charge storage can cause trouble becomes: at turn -off.

Fw Aw Ac Ph \ z $ Aco,e f While the current rises through VA -(2 \ 3Pcmlw J 2 f$ the switches at turn-on, the pre- viously high voltage across the Looking at this result, you can devices has to fall rapidly. The see that the throughput VA is a power dissipation is high during minimum (or temperature rise is the rise and fall times but, aver- maximum for a given VA) when S aged over a whole period, the is at its maximum value, 0.5 - fractional energy lost can be quite together with minimum V. V,(mm) small.

ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com There is always an offset, or forward saturation voltage across semiconductor devices. The 'on' IC period dissipation arises through the product of this voltage with the saturation current. The time taken by the switching edges is so short that they are a tiny fraction of of the cycle. Reverse recovery the steady periods of base - collector ' fs The fraction of time a particular diode device is 'on' and dissipating tt~ steadily changes with b. You can see that operating at higher fre- quencies increases the switching y E edge average losses, as there are R moreof them per second, but the V. 'on' dissipation remains steady. If Emitter - base f reverse you consider a simplified set of breakdown switching waveforms, for exam- eI voltage .1' p ple those shown in Figure 5, a f(opt) loss estimate is straightforward. The 'on' dissipation is the average t on by current, multiplied VcE(su (a) P b) over period nT, averaged over (opt) < the whole period T:

Pon_bIq+Lz to minimize tr and t¡, and a low trol. If this happens, the charge Fig.7. Minimizing loss of 2 VCE (sat) (14) saturation voltage VcE(s,). storage in the base -collector power during transistor turn- P is optimistic junction causes energy dissipa- off. Rapid -off of collector The approximately linear rise The estimate for turn and applies best to switching in tion over a long time with high current at (b) produces and fall ramps on the switching resistive circuits. S.m.p.s. cir- loss. The trajectory of the operat- optimum result. edges makes for a simple integral cuits are anything but resistive: ing point at turn off must be of the following form. At switch are additional effects from arranged to avoid the dangerous on: there leakage inductance, charge stor- second breakdown region of the age in the diodes and capacit- devices. The slow rise network uE=-t, t+V, ances charing and discharging. ensures this, see Fig. 3. The transient losses are likely to Stored charge must be taken and be worse than the simple analysis out via the base- emitter circuit. L1t shows. Typical waveforms in The current i. remains constant ,. s.m.p.s circuits are shown in during the time this occurs in a Fig.6. correctly designed circuit, then The energy dissipated and aver- snaps off quickly. The VCE edge aged over the period T is: Optimising t, and t, has begun to rise, but overall the power lost, P1, is minimized. /4 The problems of getting the Figure 7 shows the two possibilit- Fig.8. Optimum turn -on Pr'TJ UCE4dt= switching transistor to turn off ies: the required base drive wave- waveforms at (b), while (a) include the need to prevent the forms to achieve the desired shows result without extra ib A f v Ir)(I-t) t dt emitter -base junction losing con- result are shown. series induc- pulse. -T 4 4

V; lof tr 6T (15)

Similarly at turn off:

V,1 4 6T (16)

The sum of these powers gives c the total dissipation in the switch:

P= P, +P, +P)

L1 + 1c2 B 2 VCE,.a + B t p I r + 6' (Lit, +Lzt,) fti (17) - , where I have written f, the Pt (opt) : switching frequency, for 1 /T. You can see from this that the power lost is proportional to the fs. fall < P frequency Fast rise and Pr (opt) times are required in the devices ELECTRONICS & WIRELESS WORLD JUNE 1985 5:i

www.americanradiohistory.com D.C. SUPPLIES

4Ons for tf, with the `off storage The reverse current pulse has time ts, less than 3µs, (Figs 7 and ramifications elsewhere. The 8). You would have to exercise transformer winding is effectively some caution because, as I have short circuited by the diode in the shown, the switching times can first part of t1: the current pulse is be very circuit dependent. reflected through to the main To achieve circuit optimization switch (see Fig. 6) and increases of the switching characteristics, the dissipation there. All in all, you will come across base drive very fast recovery epitaxial arrangements such as that shown diodes should be chosen for this in Fig.9 which also illustrates the duty. For example, a BYW30 has desired base current waveform it a to less than 35 ns and a stored provides. charge, Qs, less than 15nC. Figure 11 compares an ordinary diode with one from the BYW Rectifiers series. As a bonus, these diodes also tend to have a lower forward There was a hint earlier that voltage drop, VF. unless you choose carefully, diodes can cause trouble in high - Output filtering: just a capacitor? speed ,switching circuits. At turn- on, the depletion layer in a p -n There is further trouble if we take junction has to be flooded with the well known smoothing capa- Fig.9. One type of base drive tor is used to store energy to form charge. This is called forward citor techniques from 50Hz linear to obtain optimum switching. the waveshapes at switch off. recovery and lifts the voltage supplies and apply them to During switch on, the base cur- drop (and therefore the power s.m.p.s. systems without rent drive must rise above the dissipation) slightly. Things are thought. Figure 12 illustrates a IB(sat) level in order to flood the worse at turn -off: charge storage straightforward s.m.p.s. output base -collector region with can cause a big increase in power circuit, with the real equivalent injected charge. This produces a loss and transients. Typical circuit of the filter capacitor. At fast rise in is and minimizes tr. waveforms for an ordinary dou- 100Hz say, the e.s.l. has neglig- The extra pulse of base current at ble- diffused diode are shown in ible effect, but consider turn on is usually obtained from a Fig. 10. The diode cannot support 50kHz...? Also, very high peak capacitor. Figure 8 shows the ris- any reverse voltage until the currents can occur in an s.m.p.s. ing edge of current at switch on reverse current reaches its peak. and the e.s.r. becomes signifi- for two conditions. The kind of Then reverse voltage increase cant. The upshot of all this is that results that can be achieved in rapidly while the remaining it is difficult to get ripple compo- practice are impressive: for reverse current sweeps out the nents down in switching sys- instance, special s.m.p.s. tran- remnants of stored charge Qs. tems . The capacitors have to be sistor type BUS13 switching This accounts for the pulse of carefully designed for this ser- directly rectified and smoothed energy dissipation shown in (b). vice. They tend to be expensive 230 volt mains in a forward con- The usual forward VF times IF dis- - and any old electrolytic won't verter, can handle a maximum sipation is also occurring and by do. throughput of 1000 watts at adding up the total over one The forward converter shown Fig.10. Waveforms in the 20kHz switching rate. The cycle, you can calculate the heat in Fig. 12 supplies a sawtooth diodes. Power pulse at (b) is BUS13 has an Ic(sat) of 10 and a sinking requirement for the current wave whose mean value caused by stored charge Vac, of 400 V. Its makers state diode, if any, to remove the waste is The variable component remaining I. after peak of that test results gave <1µs for watts in your particular applica- flows through the capacitor and reverse voltage. the turn-on time and typically tion. its parasitic series components. If we know the value of this ripple current, then the ripple voltage di amplitude is easily calculated. io ndD IF Fig. 13 shows the current wave- form ica , and the resultant peak to peak voltages across the trr e.s.r., e.s.l. and capacitor itself. io r These voltages are found as fol- D as lows. A glance at Fig. 3 with linear current ramps IVF lb p again, enables you to write down the peak to peak ripple current as: - P 0 (on) -Lo)To VF VR AIL -AI

But from Equation 5: p (a) D

( off) vo -oñ' pD D D (V;- nVo) AI, V ° IL V, Continued on page 79 ELECTRONICS & WIRELESS WORLD JUNE 1985

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www.americanradiohistory.com MOBILE RADIO Reactivating Band III Trunked repeater networks and worsening interference problems were among the topics discussed by mobile radio users at their annual conference

These are exciting times for the authority from which the industry ference- causing potential being mobile radio industry: in January, had suffered. greatest around the vision carrier cellular radio opened for business For example, Band III had been frequencies. For this reason, the on 900MHz while at the same given to the land mobile service in new mobile band had been split time tv broadcasting ended in the early 1950s because the BBC into six sub -bands with interven- Band III leaving the way clear for did not require it for television; ing gaps centred on those fre- a big expansion in private mobile yet on the opening day of one of quencies. With this arrangement radio. So there was no shortage the largest mobile radio schemes the Department hoped to be able of subjects for consideration outside the US, a 1000 -unit to provide up to 1200 interfer- when members of the Mobile radio -taxi network in London, ence -free channel pairs, with Radio Users' Association met at the Government changed its scope for trunked systems where Wadham College, Oxford in mind and handed over the band to needed. March. the new commercial tv service. Answering questions after- Opening the conference, Lord The same had happened to Band wards, Mr Stewart said that there Lloyd of Kilgerran said that the II, where the presence of public were no plans to use the gaps for emergence of cellular radio would service transmissions continued mobile radio, although they act as a prod to the entire mobile to restrict the expansion of might be assigned later to low - industry . He emphasized its broadcasting. power services in the cities. value to the small businessman: Smarting, perhaps, under this Another questioner raised the for a large company, cellular onslaught there came next Rod issue of delays by the department could mean better service and Stewart of the Radio Regulatory in granting allocations: he was improved efficiency, but to a self - Department of the DTI, one of a told that the cause was a serious employed plumber it could be the strong contingent from that unit, manpower shortage. difference between profits and whose involvement in the confer- Also from the DTI came Les bankruptcy. ence was warmly welcomed by Barclay, who described his Speaking of his own role in several speakers. department's activities in moni- Westminster, Lord Lloyd said toring interference and spectrum that five years ago no -one in Parl- Allocating band III usage. iament had been interested in The Monitoring Section's main information technology; but now Mr Stewart spoke about the tech- centre of activity is at Baldock in things were different. And he nical problems of frequency Hertfordshire, where it can moni- called on the industry to give assignment, especially those of tor frequencies ranging from presentations to Pitcom, the Par- Band III. This band is still in use 10kHz to 12.75GHz. This sta- liamentary Information Technol- by television broadcasters in con- tion, recognised by the ITU, con- ogy Committee, so that MPs tinental Europe and in Ireland; centrates on the h.f. band, where could be better informed. and Britain, through bilateral it is mainly concerned with pro- One of the more provocative agreements, has a duty to mini- tecting British services against speakers at the conference was mise interference caused there by interference from abroad. Bal- Walter Stevenson of Air Call, a mobile services. dock now has two 12m satellite founder -member of the The most serious source of dif- dishes, covering 4GHz and MRUA He criticized the "unhelp- ficulty for British users, he 12GHz. ful" regulatory attitude in Britian, explained, would be the new For investigating mobile ser- which he said had fallen behind French 625 -line service Canal vices, the department has a van the United States in mobile radio. Plus. Strong signals from this newly equipped with automatic And he reminded his audience of service were often present over and manually - controlled equip- the about -turns by the regulating wide areas of Britain, their inter- ment covering the spectrum up to

FREQUENCY (MHz) System 180 190 200 110 110 230

V C S V C S V C S V C S V C S V C S France Fig. 1. Band plan for the new 625 lines U.K. land mobile allocation /100.1110OAMM1MIIIMEMIIIILIIKENIIIMMIIIMI in band III. The gaps are to avoid interference caused by U.K. strong signals around the Land mobile Tx Base To 1 !Mobile Tx 11 'Mobile Tx Z' lBase Tx 2' 'Base Tx 3' 'Mobile 31 vision carrier frequencies of the French Canal Plus network. ELECTRONICS & WIRELESS WORLD JUNE 1985 57

www.americanradiohistory.com MOBILE RADIO

Table 1: post- WARC '79 allocations to the mobile charge was £1000 per national Spectrum pricing service in Britain (Walter Stevenson) channel (for 160 channels) plus The final DTI speaker was the £8 per mobile user, which he felt Band Name MHz Total r.f. head of the Licensing Branch, Ian was quite a good start to spec- trum pricing. v.h.f. tow band 30 -88 (F,B) 57.9MHz Jones, who was introduced light- 2 v.h.f. mid band 97 -102 (B) 4.5MHz heartedly as the man delegates (until 1989) would most like to stick pins into. Trunked systems 3 v.h.f. high band 104 -108 4.0MHz Mr Jones discussed, among (until 1995) other matters, the issue of 'spec- The theme of trunked networks, 4 v.h.f. high band 138 -235 (F) 94.85MHz trum pricing', an approach to fre- or community repeater systems, 5 v.h.f.- u.h.f. 235 -399 (F) 168.1 MHz quency allocation by which chan- was taken up by Norman Croft of 6 u.h.f. 401 -470 (F) band 58.9MHz nels might be let to the highest Motorola, a company which has 7 u.h.f. band 862 -960 (F) 98.0MHz played a large part in introducing total, all bands 30- 960MHz, 486.25MHz bidders . His department had decided to investigate the feasib- such systems in North America. ility of spectrum pricing, though Trunked systems can provide a (F) shared with fixed services - he stressed that there was no big increase in the efficiency of (B) shared with broadcasting - commitment to implement it. channel usage. Users, instead of having their own private frequen- 2: in The first study would take six Table mobile radio users Britain, 1985 (Walter cies, share between them a much Stevenson) months and would deal with fixed services; the second, covering smaller number of pooled chan- private mobile radio, broadcast- nels. Each user has access to all of them, and on initiating a call is 400 000 despatch -type radio -telephone, including police, ing, the amateur and emergency fire, prisons and civil defence services and others, was unlikely switched automatically (via a 220 000 radio message and signalling pagers, including to be completed before late 1986. separate control channel) to a wide -area, national and on -site pagers If adopted, spectrum pricing vacant communications path as 35 000 public mobile radio telephones, including message- might enable R.R.D. to drop its soon as one is free. When the call handling and cellular existing spectrum -loading crite- is over, the channels are released 100 000 vehicle and portable telemetry and radio -control ria in deciding whether to assign for other users. devices further channels: the user's will- Such a system, according to 30 000 amateur radio, mobile and portable ingness to pay would become the Mr Croft, had many advantages. 200 000 citizen's band radio including unlicensed users main factor. At present, he said, It was simple to use, offered priv- 100 000 cordless telephones licensing costs were "quite acy (though not secrecy), relia- incredibly low" in relation to the bility (failure of an individual other costs of running a mobile channel did not mean total loss of communication) and easy expan- 1300MHz. The automatic sys- system, and some operators made excessive demands for fre- sion to accommodate new users. tem scans 300 channels per sec- Since costs were shared it was ond and measures the signal level quencies. Spectrum pricing might sharpen their appreciation especially attractive to the small on each. Data is stored on a Win- user. As a bonus, trunked repea- Fig. 2. Typical noise output chester disc and then transferred of a valuable resource. "Why must the Government decide ter systems offered reliable of a high -band solid -state to magnetic tape for off -line com- mobile -to- mobile contact. transmitter. Even at puter analysis later on. Up to 10 what is a frivolous use of radio ? ", he Even greater traffic densities frequencies several hours of data can be held on a asked; "shouldn't the market decide ? ". could be achieved by grouping the megahertz away from the single tape. mobiles under network controll- carrier, the noise is still With this information, opera- Mr Jones spoke also about the announcement in January by the ers or 'dispatchers', such as were strong enough to open the tors can list channels in order of used by taxi firms. muting of other receivers on their traffic congestion. And they industry minister, Geoffrey Pat- tie, of the Government's initial Cellular radio was itself a the same site Ferrite can study in detail any channels trunked system, though the isolators and careful filtering with anomalous traffic loadings. decision on the uses to which Bands I and III would be put. The networks now envisaged would can provide a cure. (Gerald A second van is to go into service not permit hand -off from one David) later this year. minister was considering the pos- sibility of one or more large base -station to another as the national mobile radio networks; mobile roamed about. To cover these would not however be adequately a large region such as allowed to interconnect with the the London area, trunked sys- public telephone system, except tems would probably have to possibly on a very limited basis. transmit simultaneously from Applications would probably be multiple sites and incorporate invited for up to five trunked radio voting techniques on the receive systems in major conurbations, side: using the common signalling standard now being drawn up. Cellular radio The government also wanted to hear from companies interested The first three months' experi- in setting up two -way mobile data ence with Cellnet, one of Britain's transmission systems. two new cellular radio systems Mr Jones promised further was the subject of a presentation Typí'n!'-eleìv-- threshold ministerial announcements by by Bernard Mallinder, formerly early summer. the consortium's technical direc- A questioner asked why the tor and now general manager. Fo +1 .2 SEPARATION FROM CARRIER (MHz) 900MHz band had been given so (No representatives of the rival cheaply to the cellular radio oper- Racal -Vodafone system were ators. Mr Jones said that the present at the conference.)

ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com MOBILE RADIO

At the end of March, Cellnet unit is rarely better than 130dB A folded dipole mounted on the conditions of telecommunica- had just over 4000 subscribers. below, which is much worse than side of a steel mast was usually tions operators and to investigate Areas covered now include Birm- with earlier thermionic designs. not good enough, since the mast complaints within the industry. ingham, Manchester and Liver- Thus, at a multi - channel trans- created unwanted lobes which Speaking of Bands I and III, pool, and the system is expected mitting site, the accumulated would confound the intentions of Prof. Carsberg said the Govern- to cover 80% of the population by noise can be sufficient to open the the planners. Attempting to deal ment had asked his advice on the middle of next year. muting of all the receivers. with this by mounting a dipole on their allocation, and that he The busiest times for callers The cure, said Mr David, was each side of the mast produced would be reporting shortly. The are just before noon and just to add cavity and bandpass filters even worse results: a radiation interests of the consumer would after. Four-fifths of all traffic throughout and to insert ferrite pattern with deep nulls. A better be paramount, he said. "We wel- occurs between 0800 and 2000; isolators in each transmitter's approach was to use dipole or come the opportunity to have 70% of it is originated by mobiles output to prevent unwanted mix- slot -fed panels on each face of the contacts with organisations on and the average call duration is ing. tower, driving them in phase: matters which are important. about 93s. Calls cost 25p per this would be more expensive, They should not wait to be minute at peak times but fall to 8p A switch to s.s.b.? but the antenna would have a invited." per minute in the evenings and broadband characteristic and so weekends. The prospect of novel modulation could be shared by several ser- Cellnet is now working on pro- modes was looked at by Prof. vices. tocols to permit data communica- J.D. Parsons of the University of Typical aerials used by cellular tion with mobiles: at present Liverpool in a paper which was systems consisted of ten -tier there are difficulties because of published at the conference, but panels, which gave high gain in the momentary interruptions as which he was unable to present in the horizontal direction, but the mobile passes from one call to person. could have sharp nulls at other another. The Government, he wrote, angles. This could give rise to was under pressure to allocate a poor coverage in areas close to substantial part of Band III to sys- the base-station, especially Tackling interference tems using amplitude -com- where the station was at a high panded single - sideband trans- site above a town. In this case, With the rapid growth in mobile mission. This would greatly Mr Collins said, mobile operators radio during the last few years, increase the traffic capacity of the could borrow an idea from broad- there has been a marked increase band by making possible a reduc- casters, who phased the ele- in the number of radio stations tion in channel spacing to 5kHz. ments of such arrays so as to pro- sharing a common site. Co- siting But its cost in receiver complex- duce a slight downward tilt. A tilt can result in severe mutual inter- ity would be significant. How- of about 2.5° to 3° was common in ference; and the mechanisms by ever, some of pilot tv practice: it directed the main which this occurs were described sort -tone would need to be added to the beam more accurately at the Fig. 3. Polar diagram of a by Gerald David of Aerial Facilit- to provide boundary of the service area and vertical high -band folded ies Ltd. transmission a.g.c. and a.f.c. filled in the nulls close to the sta- dipole stood off a 2m -square One problem results from the Further investigation of tion. solid on a 1.5m boom fact that the transmit -receive fre- mast a. c. s . s. b. was needed to evaluate Another idea worth borrowing (left): a common quency spacing is generally con- its susceptibility to interference, from broadcasters was to avoid arrangement in mobile radio stant within a given band. An particularly on the signalling hilltop sites where possible: it practise, but one which gives incoming signal from a mobile channel; however, in the mean- could help reduce co- channel disappointing coverage. will mix at the base station's time it looked as though the first interference. Adding dipoles on the other transmitter output to produce a systems to be licensed would Mr. Collins added that cover- faces of the mast (right) difference frequency. Any other employ conventional f.m. age with mobile systems was makes matters even worse: transmitter in that base station often restricted by multi -path eight deep nulls appear and can now mix with that difference reception: the use of polarization the strong lobes between frequency to produce its own Improving coverage diversity at the receiving site them frustrate the efforts of receive frequency, which will be A common source of complaint could bring about worthwhile frequency planners. Much treated as a valid input on that among mobile radio operators is performance improvements. more even coverage (centre) channel. With lmV of received failure to achieve adequate cover- Guest speaker at the confer- results from phased array of signal coming in, up to 5011V of age of a system's service area. ence dinner was Professor Brian dipole or slot -fed the transmit -receive difference Brian Collins of C & S Antennas Carsberg, director -general of panels mounted around the frequency could be floating about said that many of these problems Oftel since its inception last year. mast. This arrangement in the installation. could be avoided at the planning Prof. Carsberg outlined the func- costs more, but has broad- Interference problems at stage by a better choice of site for tions of Oftel, which by next year band characteristics can shared base stations could be and the base station and by better will have a staff of up to 110, with be shared between several very hard to solve. Mr David aerials. powers to enforce the licence (C&S Antennas) mentioned one case of intermod- users. ulation interference at a site equipped with 35 transmitters, where it had taken four hours of mainframe computer time to track the fifth -order intermodula- tion products. The signal being looked for turned out to be an 11th order product. A further source of interfer- ence was the noise generated by modern solid -state transmitters. The spurious noise 2 -3% away from the carrier in a typical 25W ELECTRONICS & WIRELESS WORLD JUNE 1985 5E

www.americanradiohistory.com by Rod Cooper Avoiding failure of sealed NiCd cells Nickel - cadmium cells are expensive to buy, yet are often thrown away for lack of a few drops of water! More attention is needed in their day -to -day use to achieve their full lifespan, argues Rod Cooper - the use of cheap chargers that do not do their job properly is a completely false economy. Failure mode no .1 (May issue) temperature, all other factors recombination process to place at dealt with the importance of being equal. For standard cells so- called `safe' rates. For stand- water to cell operation, and how the designed rate is C/10 where C ard cells a temperature of 20° to loss of even a small amount is the capacity in amp- hours, the 30° is suitable. Even charging at caused by reverse- charging could cell being able to tolerate this rate 10C can result in a doubling of the result in a drastic shortening of at 20 °C without immediate prob- usual overcharge pressure, a cell life. The article continues lems (but see failure mode 3). point worth remembering if with loss of water as the theme. During normal overcharge attempting to charge standard (i.e. C /10 at 20 °C) the internal cells at fast rates at low tempera- Failure mode 2: loss of electrolyte pressure will rise slightly due to tures, for example out of doors on water due to incorrect charging the presence of oxygen and the a cold day. small increase in temperature. A common practice is to Oxygen is absorbed in a recombi- Neither of these effects present a recharge NiCd cells overnight, nation process with cadmium problem until the C /10 rate is which usually means that the during normal overcharge. The exceeded, when the internal charger is unattended, so for rate at which this reaction can pressure will rise rapidly until the safety's sake many people choose proceed is determined by how safety vent opens , due to an accu- to do this in an outbuilding where much extra active material is pro- mulation of unrecombined oxy- a malfunction can do little Construction of typical sealed vided by the manufacturer at the gen . This condition is often exac- damage. More often than not nickel -cadmium cell. negative plate and by the ambient erbated by a rise in temperature if such an outbuilding is unheated, the charge current is uncon- and in winter it is quite easy to trolled because this lowers the damage cells at a supposedly safe Rubber Vent hole Spring valve face internal resistance and increases rate of charging. the current further i.e. thermal - Rubber gasket runaway, Fig. 6. The end result Avoidance tactics of exceeding C /10 is loss of capacity, and often an abused cell Both of the above effects are Positive tab Swaged seal will show one or two other symp- more likely to happen during fast - toms; a bulge in the bottom of the charging so for standard cells it is Separator steel case as shown in Fig. 7 and best to adhere to the recom- Positive plate Negative plate splitting of the plastic sleeve, mended rate of C /10 and ensure (spiral wound (spiral wound ) both due to the high internal pres- an ambient temperature of 20 °C. sures that are generated before Some fast -chargers have a tem- the safety vent opens. Opening perature cut -out which operates pressures in excess of 140 p.s.i. when overcharge has been are quoted. reached, so it might be thought There is another way that elec- that this neatly avoids such prob- trolyte can be lost via the safety lems with standard cells. How- vent which is often overlooked. ever, some excessive overcharg- At low temperatures, like most ing has already taken place by the chemical reactions, the oxygen time a temperature cut -out can recombination process becomes operate, because of the time -lag much slower. If charging is main- between the rise in internal pres- tained at C /10 the pressure will sure and the rise in temperature build up due to excess oxygen in which follows it. just the same way as during over- If fast charging is required it is Negative tab charge with excessive current. far better to adopt special fast - Indeed a reasonably high temper- charge cells which have a greater ature is needed for the oxygen oxygen recombination capacity. 60 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com The penalty paid is a reduction in 2Ni0OH + Cd + H2O -.2Ni(OH)2 + through itself so that the cell 25 Ah capacity - generally about Cd(OH)2 never becomes fully charged. 10% - but such cells can with- The electrochemical equivalent When put into service, any 4 stand typically a charge of C/3 and atomic weight of cadmium charge already in the cell rapidly Ambient temp =2ft during overcharge at 20 °C. An can be looked up in any reference leaks away through the dendrite, Charge rate .0 /10 example of this type of cell is the book on and perhaps in only a few hours. The Celt size 'C` electrochemistry, 15 3 Cadnica N -500 AAF. The capac- these are 2.097g/Ah and 112.4 short time needed for a healthy PRESSURE ity of this cell is 450mAh com- respectively for cadmium. cell to become 'dud' must provide TEMP t °C) lkgkm2) a of surprise, puzzlement pared to 500mAh for the standard A D -cell has 4Ah capacity and source 10 2 cell, but it can be recharged in 4 to thus 8.388g of active cadmium. and possibly indignation to the 6 hours instead of the usual 14 to From the above equation, 112.4g user, who may well have followed

16 hours. The size and weight are of cadmium reacts with 18g of instructions to the letter and who 5 about the same and the price only water. Thus 8.388g of cadmium cannot see that he has done any- slightly more. will react with 1.342 g water. thing wrong to the cell to cause it Of course, this may not be the to malfunction. amount put into a cell but it shows The charging conditions that 0 8 9 10 11 12 13 14 15 16 HOURS Experimental cure the order of magnitude of the favour dendritic growth, on the quantities used, which is very evidence available, appear to be Correlation between rise in Several D and C-size cells in my low current over extended peri- pressure on reaching had useful when refilling a dead cell. own collection of NiCd cells ods. The Cadnica handbook for overcharge phase and rise in over- been subjected to severe Failure mode 3: degradation of plates example warns of 'continuous temperature that follows one charge, reverse -charge and low - and seperator charge over a long period' and the or two hours after (from the to acci- temperature abuse, due article by K.C. Johnson on NiCd Cadnica Engineering in faulty charging equip- Due to the dangers of loss of elec- dents cells (WW Feb. 1977) suggests Handbook). experi- trolyte already detailed, it is ment and also deliberate that 'gentle cycles of charging and have tempting to think that a low rate ment, and were known to discharging are likely to acceler- of charge spread over a long little or no capacity. Some of ate the process'. My own experi- of their period was the best solution. these cells were stripped ence confirms this. (this was done pre- However, this would be a mistake steel casing Apart from this problem, the cisely by machine -tool and so did because low rates of charge over plates of a NiCd cell are both phy- contents it is extended periods appear to cause not damage the - sically and chemically robust and not recommended due to the another type of failure. This is cause few problems. The same highly hazardous nature of the referred to obliquely in manufac- cannot be said of the separator, electrolyte and the turers data sheets as 'crystal KOH /LiOH usually polypropylene or nylon in possibility of internal pressure) deformation' of the plates, but fibrous form. During normal the electrodes removed and what it means in practice is that over - charge the separator mate- wound with nylon cord to prevent the cell develops an internal rial is subjected to attack by the disintegration. Immersion in short- circuit which renders it oxygen which must diffuse from fresh electrolyte and subsequent useless long before the expected positive to negative plate for recharging showed that much of life -span is reached. recombination. This attack is Do's Don'ts the capacity had returned, indi- The trouble is caused by the and made worse by the high pres- cating that the active materials of pronounced crystalline nature of Recharging sures and temperatures encoun- plates were relatively unda- cadmium, which is of the hexa- Don't recharge cells connected the tered during excessive over- maged. gonal- pyramid type, and also the in batteries if at all possible. charge. A cell temperature of Following this successful very slight solubility of cadmium Recharge cells singly instead. 50 °C is often quoted as being the experiment, a small hole was in the electrolyte. During the Avoid temperatures above 50 maximum permissible to avoid drilled and then tapped in the charging process, if conditions and below 5 °C. failure. nylon top of another 'dead' cell. A are right, cadmium can be depo- Don't persistently overcharge The more usual form of deteri- matching nylon screw and neo- sited in the form of dendrites, cells - use an end -of- charge oration is a slow process and fai- prene washer resealed the hole, which are miniature tree -like cut -out. lure occurs due to accumulated Fig. 8. Small quantities of dis- growths with spiky branches Recharge standard cells at effects over a long period. Manu- tilled water were gradually intro- sprouting from a central trunk C/10 - invest in fast -charge facturers state in their data duced via the hole with a hypod- and standing clear of the elec- cells if you want faster sheets that prolonged or repeated ermic syringe during a succession trode. There is also a sub -species recharge. overcharge even at safe rates has of recharge/discharge cycles, of dendrite, the whisker; these Discharging a deleterious effect on cell life, until most (but not all) of the are single filament or rod -like Where possible, don't use cells yet it is still common proceedure capacity had returned. This cell structures 1 21.tm in diameter connected in batteries. Use a - to leave cells on charge for hours was eventually returned to ser- which stand out like stubble on an d.c. /d.c. converter to step the after full charge has been vice. unshaven chin. Cadmium has the voltage up whenever such a reached. This is bad practice. The only cells that refused to dubious distinction of being the technique is suitable or rede- Unfortunately there is an almost respond to this treatment were first metal in which whiskers sign circuit around a working universal belief that an indefinite those that had been subjected to were observed. There are some voltage of 1.25V. amount of overcharge at C/ 10 is high temperatures, the inference good photomicrographs of den - If batteries are essential to the perfectly alright. being that high temperatures dritic growth in ref.2. application, make use of pro- To assure full life expectancy a cause more damage of an irrever- The dendrite can grow through tection diodes or low voltage NiCd cell should have its recharge than does excessive the seperator and eventually cut -out. sible nature period terminated shortly after overcharging or reverse- charg- bridge the very small gap General the oxygen recombination pro- ing. between the plates, providing an Avoid encapsulated batteries cess has set in, preferably by It is easy to calculate the mini- internal short- circuit. This often like PP9 automatic means. mum theoretical amount of water happens to an apparently healthy Don't replace dead cells in a brand -new cells, needed in any particular type of cell; during the charging process Avoidance tactics battery with cell from the basic reaction a dendrite will bridge the gap and and do not add partly -used shown on page 61, May Issue. divert further charging current A cycle life of 500 times and up to cells onto a new battery. ELECTRONICS & WIRELESS WORLD JUNE 1985 61

www.americanradiohistory.com NICAD CELLS

Fig. 11. Localised pin -hole corrosion caused in this instance by contact with sea Fig. 6. An overcharged water for a short time. This cell, sectioned to show the also could have been pre- collapsed base. This cell vented by grease or paint. was overcharged due to a Fig. 7. An overcharged cell showing a bulge in the base fault in the charger, but caused by high internal pressure prior to the safety vent 2000 times has been claimed by shows what can happen opening. A normal cell is shown for comparison. A condition the manufacturers at charge rates when any cell is charged like this is a sure sign of abuse, whether due to charging at of C /10. It would seem from this for longer than is too low a temperature, reverse charging or to charging in that charging at this rate does not necessary at a rate which excess of C /10. lead to dendrite problems, at is too high. The contents of least in laboratory tests. My own this cell were expelled experience is that, in practice, when the cell became hot, charging at C/10 does lead to den- and on cooling the case drite problems in some cells but collapsed inward. not in others, although they may be in the same battery. There seems to be no hard and fast rules about predicting which cells are prone to form dendrites. I have experimented with a promising technique for supress- ing the initial formation of den- drites, and this will be described as a practical construction project in a later article. To avoid material degradation it is safe to assume that a stand- ard cell should be charged at C/10 provided that the overcharge period is detected and curtailed.

Fig. 9. The effects of electrolyte creepage on two types of Experimental cure cell. The deposit has started to corrode the cell on the left. There is no cure for a damaged Fig. 8. A cell which has Fig. 10. Generalised seperator, but an interesting cure . "dried out ", modified by corrosion caused by for dendrites was put forward in putting a filler hole in the water being trapped K.C. Johnson's article. Essen- top so that water can be between the plastic tially this consists of a charge and introduced in controlled sleeve and the side discharge programme at con- quantities. The filler hole of the cell. Plastic trolled but very high rates, to in this particular cell is sleeves are best melt the dendrites and reform the sealed with a nickel- plated removed and cadmium on the negative plate. A steel pan -head M2.5 replaced if necessary period of normal overcharge is screw, which does not with full-width recommended to oxidize remain- interfere with normal use adhesive tape. ing dendrite material, the theory of the cell. A small Exposed parts can being that the dendrites are in a neoprene washer be coated with relatively prone position for oxi- completes the seal. "Komoline" grease dation compared to the rest of the or painted with electrode. There must be a com- "Celvar" to prevent promise between controlling this type of dendrites and degradation of the corrosion. separator with the oxygen of the overcharge mechanism. Temperature must be carefully

;2 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com controlled during the above treat- and nitrile rubbers, epoxy resin Unfortunately there is no effec- in a battery compartment, but is ment or more problems will be and also thermal sealing with var- tive cure for pinholes or remedy ruled out if the cells are spot - created than solved. I recom- ious thermoplastics. All attempts for advanced corrosion as shown welded together or are encased in mend looking at this article in failed, although sealing with ure- Figs 10 and 11. a container like the PP9 or PP3. detail. I have tried it and it works, thane solution (used for making These batteries are best avoided Multiple failure modes but I have reservations about the the seams in neoprene wet -suits) for this reason. separator failing, as nylon melts did last several months before the Damaged cells are less amenable Conclusion re- appeared. I at around 220 °C and polypropy- signs of creepage to diagnosis, and corrective lene at 170 °C so localized melting concluded that there is no really action more difficult to imple- NiCd cells are expensive to buy, satisfactory cure and that it is bet- may occur in the areas around ment, if more than one failure they use up the relatively scarce to throw away a faulty cell dendrites which will lead to prem- ter mode is present. For example, a and finite resources of nickel and damage to ature failure anyway. Also, I have than risk corrosion cell may be suffering simultane- cadmium, and consume large found that cells treated with this surrounding equipment. ously from being over -charged amounts of energy and industrial method rapidly reform their den- capacity in their production, yet Failure mode 5: and reverse- charged, or may be drites. dendrited and have separator fai- they are often thrown away for The external case material is lure. lack of a few drops of water! Failure mode 4: electrolyte creepage commonly thin- walled steel. Recharging and discharging More attention is needed in the practical day-to -day usage of Electrolyte creepage manifests Rusting is prevented by nickel - cells in series tends to promote NiCd cells so that the full lifespan itself as a furry white deposit, plating, which is adequate for the disparities between cells and of 500 to 2000 cycles can be often confined to the top of the most purposes but not entirely increase the number of defects. achieved, present practice being cell but sometimes spreading to satisfactory. The case is usually This is explained as follows. Sup- more akin to that associated with sides and onto surrounding com- covered by a plastics sleeve, and pose a battery has seven cells; a throw -away product. ponents such as circuit boards this can assist corrosion by trapp- after a period in service perhaps In particular, because NiCd and wiring where it wreaks havoc ing moisture between sleeve and four of these cells have full capac- cells are expensive, the use of due to corrosion, particularly of case. Fig. 10 shows an example of ity, two slightly less capacity and cheap charging equipment that copper, zinc and tin parts. The such corrosion, which was com- one cell is in the early stages of does not do the job properly is a cause of this phenomenon lies in pletely hidden despite its adv- dendrite formation. Cells are completely false economy. the penetrating nature of the anced state until the sleeve was never exactly equal to start with are the ones that charge potassium hydroxide solution removed. The cause was mois- and diverge in their performance (These cells in series, have no over- used as the electrolyte, which ture from a damp atmosphere in service even if they are of the charge limiting device and no seems able to get past seals which assisted by slight electrolyte same type and same manufac low- temperature control.) on the face of it appear to be well creepage. ture, so this is a realistic assump- Also, it would be useful if the designed. After creeping past the Fig. 11 shows another cell tion. makers provided some means of seal the hydroxide is converted to which was exposed for a short If this battery is recharged so - cells are fully giving the electrolyte a partial carbonate by reacting with CO2 in time to a small amount of sea that the four healthy - service; a re- sealable valve simi- the atmosphere. Potassium car- spray, again trapped by the charged, then the two reduced lar to that already provided for bonate is less hazardous that the sleeve despite washing down in capacity cells will be over- excess pressure so that a hydroxide (which can remove fresh water. This rapid corrosion charged. The dendrited cell may venting When this measured quantity of water could skin with rapidity) but still pres- resulted in a pin -hole and a ruined not reach full charge. battery is fully discharged, the be injected for example. This is ents a corrosion problem for cell. and not a suggestion that diverges too metal parts particularly in damp In another instance of corro- two cells of reduced capacity - far from the sealed -cell concept. conditions. sion, a zinc -plated screw was left the dendrited cell will be reverse It would be expensive and could Loss of electrolyte leads to loss on top of a NiCd cell and this charged. The two cells of reduced will also eventually be made quite safe. The other of capacity but experience sug- caused a pin -hole with surprising capacity from deteriation item that manufacturers could gests that this is a lengthy pro- rapidity, probably assisted again suffer separator being over- assist with is the provision of cess. In the battery of cells in the by slight electrolyte creepage. by persistantly One cycle of the charge/ more comprehensive information photograph (Fig. 9) the cells that charged. Avoidance tactics discharge described may not on fault- finding than in presently showed the most efflorescence make much difference but 20 or available. also showed the largest drop in It is metals best to keep dissimilar 50 cycles certainly will, and two An article dealing solely with capacity, as one would expect, and zinc away from like copper failure modes will have been failure modes naturally gives a but it took 12 months to get to the Where a damp the steel case. introduced simply by cycling the false impression of the technical stage shown. is likely, it is a good environment cells in series. integrity of the subject under dis off the plastic sleeve plan to strip Even if the charging process is cussion. Given a proper system more trouble Avoidance tactics altogether - it is modified so that the two cells with of management, it must be said than it is worth, especially if the fully Some manufacturers' products reduced capacity are that nickel -cadmium cells can cell is subject to electrolyte cree- charged, leaving the healthy cells give superb performance, paying tend to suffer more than others page. If insulation is required from this defect. The only avoid- undercharged, the dendrited back many times over the invest- then the cell can be wrapped in still not ance tactic one can practice is cells will in all probability ment in recharging gear, the 50mm wide adesive fabric - will be of the cells them- based on experience simply be fully charged and higher cost - backed tape (RS Components reverse -charged when the bat- selves over other types of cell, avoid those manufacturers whose metal can be 512 -058). Exposed tery is discharged. Further modi- and the extra equipment needed cells give creepage. I have tried painted with Celvar cell paint or four different makes of cell and fying charging so that this den- to prevent accidental abuse in smeared with Komoline grease, extra only one the nylon -topped var- drited cell receives an service. - both these products being made charge leads to overcharging of iety made by Saft has shown nickel- - by Chloride -Alcad* for the other six cells. Further reading freedom from this trouble. I have tried all cadmium cells. The correct way to charge cells three techniques and they are Alkaline storage batteries, by Falk & is to charge them individually Salkind. Wiley, 1969. Experimental cures effective in avoiding corrosion. needs. Cadmium, by D.M. Chizhikov. each according to their Pergamon, 1966. I have tried re- sealing cells suf- * Celvar is an alkali-resistant paint for steel This is not a difficult requirement Nickel -Cadmium Battery, by Grant. cell containers, Komoline is a special min- if the battery is made up of cells General Electric, 1975. fering from effloresence with eral jelly for greasing steel cell tops, both Nickel cadmium cells, by K.C. Johnson, neoprene compounds, urethane available from J. Biles Engineering. like the AA, C, D and F types held Wireless World, February 1977,'PP 47,48. ELECTRONICS & WIRELESS WORLD JUNE 1985 63

www.americanradiohistory.com by David Stonebanks Cassette recording with the BBC micro Improved performance with conventional recorders and an alternative digital method

The cassette port of the BBC Mic- the read waveform somewhat to reversals on the tape; rocomputer encodes logic 0 as overcome this uncertainty, but elimination of the need for a 1k To computer cassette i/p one cycle of 1200Hz tone and a not always enough. A simple replay volume control (there is cassette T47Ó recorder logic 1 as two cycles of 2400Hz. integrating circuit (Fig .1) can nothing to set incorrectly); earpiece socket 0V These tones are synthesized sine often improve reliability. It reliability. waves, the frequency changes causes some attenuation and In the circuit of Fig.2, amplifier occurring at the zero -crossing reduces the amplitude of the Al limits the writing (record) sig- Fig. 1. This simple point (trace 1). 2400Hz waves to half that of the nal from the computer to square - integrating network can help When such a waveform is 1200Hz waves; but the BBC off the waveform. The input cap- reduce uncertainty at data replayed from tape, the read head Micro includes a limiting ampli- acitor is not really necessary, but transitions. differentiates it, giving an output fier and is quite tolerant of ampli- I am happier with the input iso- proportional to the rate of change tude variations provided that the lated. of flux (trace 2). signal is correctly phased. Amplifier A2 provides a ±6V After amplification and limit- If the frequency change could square wave drive to the write ing, the waveform is as shown in be made at the peak of the head via a 4.7kS2 current- limiting trace 3. Continuous logic zeros recorded waveform (trace 4) the resistor. If the power supply used correctly produce 1200Hz square differentiated waveform would be is itself ±6V then the zener waves (417µs for each half -cycle) as required (trace 5). When diodes are not required. and continuous logic ones pro- amplified and limited, this pro- To ensure fast current rever- duce 2400Hz square waves duces the easily - interpreted sals the head must be driven from (208µs for each half-cycle). But waveform of trace 6. a high impedance. Head current where the logic value changes for must be enough to saturate the consecutive bits, the result is a Digital recording tape fully, but not so great as to Fig. 2. Replacing the cassette pulse of intermediate length The advantages of digital record- leave the head magnetized, eras- recorder's electronics with (314s), which is impossible to ing over analogue (audio) meth- ing the signal instead of reading this digital read -write chain interpret correctly. No wonder ods are it. With the recorders I have mod- gives high reliability cassettes are so unreliable! a high output from the head ified, 4.7k52 was suitable, but it at low cost. Tape recorders do integrate when reading because of full flux cont. on page 20

WRITE Fig. 3. Data recording on cassette: the problem and the AMPLIFIER R To give solution (see text). 10mA through From A, 1eds cassette port Logic value()

IRECORD1 1 1 /\ 0 I 0 1 'Trace 1

4k7 OV

Trace 2 He od Iiii004 -I Trace 3 READ AMPLIFIER 1-_-. Il E I4 0----AA/ -+ \ 1M Troce 4 3k9 ' 1111 114V w 4, 70 A4 To BBC mic, 100k 2k2 cassette poi Trace 5 100 k \-/ 3k9 r n r Troce IC LM 348 or equivalent Ir ! D lodes 1t14148 Power u 6 to 15V

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recognised the significance of negatively charged sphere are I2 q2 No the article's subject. (Spec. Sci. FUNDAMENTALS shown in Fig 1. F- 2na 2n eoa Tech. 5, pp. 421 -431, 1982). The forces on the spheres in OF Eastwood's article deals with ENERGY Fig. 2 are the same in which is exactly the same force experiments (actual, not magnitude and sign. However, TRANSFER as we derived using magnetic thought) performed to in the situation of Fig. 3 where theory. determine the peculiar or we have superposed the charges Mr Catt evidently assumes that This is a general result absolute velocity of our galaxy on the spheres from Figs 1 and the often- repeated statement embodied in the relativistic relative to the 3K cosmic 2, we find that the forces invariance of Maxwell's microwave background that the field round a disappear. line if TEM has equations and may be radiation. As velocities are transmission If Mr Catt is searching for been proved. But has it ?. If considered to be the unification calculated relative to a point in unification of electric and of electromagnetic and to be at rest, there is a proof that the electric magnetic forces, he may be space assumed electrostatic field theory. radiation is field is everywhere strictly interested to consider the the 3K microwave N.C. Hawkes assumed to be at rest, i.e. transverse then, please believe following. I be glad to Abingdon standing waves caused by the me. would really In the double beam c.r.o. Oxfordshire constructive interference of see it. mentioned in Chris Parton's The proof would have to deal letter (December, 1984), the crests and troughs of waves relative to Newton's with the following point. As a force per unit length on each moving RELATIVITY absolute space at rest. step wave passes down the line beam of electrons can be In of Eastwood's it sets in motion the electrons written as the sum of the Recent articles and letters on the part headed of in the conductors. That is, the electrostatic repulsion and relativity and the speed of light article 'Anisotropy background' electrons are given (kinetic) magnetic attraction make me consider the greatest microwave energy by the field. Hence, observable experiment, the "red Eastwood gives the true or somewhere, energy passes Roy q2 shift" of distant astronomical absolute velocity of the earth through the surface of each F objects. The faster the object relative to the 3K background conductor, that is, somewhere 2na 2n 0a recedes, the slower the peaks assumed to be at rest as about there is a component of the arrive so the redder they 390 km /sec. This velocity Poynting vectro into the where a is the separation of the appear. Now suppose the object vector is the Newtonian vector conductor. So somewhere, two beams. recedes at light speed: then no sum of three other velocity there is a component of electric But, if you transform to the energy is arriving, no phase is vectors assigned to empty space field along the conductor. rest frame of the electrons, changing, in fact nothing is filled with 3K electromagnetic P.L. Taylor travelling at speed v, the happening, yet according to radiation by cranks and Marple magnetic field disappears since standard theory the light - at crackpots. ( "...nor assign a Cheshire the charges are now at rest. infinitesimal energy - is still velocity vector to a point in Now, if q is the charge per unit arriving at c. In what sense can the empty space in which length in the beams in the take I believe Mr Catt (Letters, anything be said to be travelling electromagnetic processes laboratory frame, then the February 1985) has made an past an observer's position if it place." - the introduction to length part of q must be error. is impossible even in principle Einstein's 1905 paper). Lorentz transformed to q' giving He seems to be saying that to observe it? We cannot escape The other three velocity the principle of superposition this by claiming that it is vectors are: - should apply to the situation he q' = q/Y impossible for even (1) The orbital velocity of the case of astronomical objects to travel at earth relative to the sun describes - the the where -y - (1 - v2/c2)-1 forces between conductors light speed away from us, since assumed to be at rest - 30 carrying overlapping pulses. It there is no evidence of their km /sec. is, of course, wrong to try to behaving with any such (2) The orbital velocity of the apply superposition here, since Thus the electrostatic repulsive limiation. The only sensible way sun relative to our galaxy's the equations he has written force can be rewritten to iinterpret it is that we cannot centre of gravity assumed to be down for his forces F1 and F2 observe a velocity greater then c, at rest - about 300 km /sec. which may well be in most (3) The absolute linear ( ?) are not linear (as superposition q2 true q'2 q2v2 velocity of our galaxy's centre demands), but quadratic. F = cases. 2n eoa 2n eoa c2 2n eoa R.A. Rees of gravity relative of the 3K The equations Kirkland background assumed to be at WA rest - about 600km/sec. F1- iB and F2 -qE USA The earth's absolute velocity Finally, substituting vector of 390 km /sec. relative appear at first sight to be linear, May I draw your readers' to the stationary 3K but since B is itself proportional 1 attention to the implications of background is constantly to i, and E to q E. 'Radio directed from Aquarius to Leo lloeo Eastwood's article and the birth of the universe' but continuously variable in F1 - k1i2 and F2 - k2g2 where the current in the beams (Wireless World, August 1981). direction relative to a point on is I-q.v, we have H. Aspden has already the earth's surface. In the Thus the forces are quadratic northern hemisphere Aquarius functions of the current and is an autumn constellation and charge on the conductors and Leo a spring constellation. linear superposition is invalid. Lorentz used the earth's We should therefore not be orbital velocity vector of 30 km/ surprised by the appearance of sec. to calculate the earth's these 'strange' forces. constant equatorial contraction This is perhaps more clearly of "about 6.5 cm." due to the illustrated by the corresponding constant pressure exerted by problem in electrostatics. The the ether wind. (The Principle forces on a positively and of Relativity, Dover. p.6.) The ELECTRONICS & WIRELESS WORLD JUNE 1985 69

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model of the relative motions 0.9c. It has thus been shown the flashes at different times; and Causation. Let Max Planck of the heavenly bodies used by that the physical velocity limit he begs the question by sit on top of it as an abstract Lorentz in his calculations is of c is a reality when the transferring Ms definition of quantum of energy positively one step removed from the flat E =Mc2 equation is used. If one simultaneity to the world of M'. glowing with absolution. Let a earth theory and just as assumes that mass is constant, An incident recently brought special relation in the shape of a dangerous. as Dr Murray presumably does, to my attention is a good creative ape called Roy Hodges Michelson, Morley, Lorentz then where does the illustration of the problem. My MIEE run down and up the and Einstein assumed the exponential increase in energy friend Tom was sitting in his pyramid, translating the velocity vector of Stoke's input arise? signal box, watching the up and abstraction of method into hypothetical ether wind was Thirdly, in his argument on down trains rattling past, when material means and vice versa, equal in magnitude but opposite the train experiment it would he noticed two flashes of so demonstrating the creative in direction to the earth's appear that a subtle change lightning at different points of and analytical process of orbital velocity vector relative takes place between the the track. His portable visualisation so abhorred by to the sun, which they believed disproving of Einstein Lightning Detector informed digital theoreticists who use to be stationary at the centre of assumptions and its him that the flashes had arrived computers when they run out of the universe. They believed the paraphrasing on the following at precisely the same instant. fingers, so to get it as orbital directions of the vectors page. Dick on the up -train and Harry declinatory as the average were absolute and constant In Einstein's argument the on the down -train happened to monetarist. relative to the supposedly flash at A and B take place at be opposite the signal box then, One might now be deboggled stationary sun, and that both the moment M and M' coincide, and got similar results from as Mr A.H. Winterflood was vectors were directed parallel to hence it is to the observers their instruments. when he grasped that energy is the plane of Michelson and future positions that the light Tom subsequently discovered and mass becomes - between Morley; s apparatus. will arrive. that the scorch marks on the them lies a Constant Time They were unaware of the However, in Dr Murray's track were precisely equidistant Function, the fastest thing on real experimental fact that the analysis he maintains that the from his box. Dick and Harry wheels, which also has a direction of the earth's absolute light will travel the distance A- found that the scorch marks on reverse gear so allowing Mr velocity vector is a continuous M and A- M' in the same time, their respective trains were not Hodges to run up as well as variable relative to the plane of hence reaching both observers equidistant from their seats; down. (Wheels are frictional - Michelson and Morley's simultaneously. In other words the differences were several when energy is in abstraction it apparatus, and that Stokes's he has their future positions thousand nanometres. has none, so it can go as fast as ether wind blows seasonally and coinciding, not their present When the three of them it is pushed). daily at continuously varying ones. compared notes that evening in Special Relativity applies angles through the ceiling of But in the paraphrasing of the the taproom of the Monkey's when correcting the error of Michelson and Morley's above paragraph this has been Nest, there was some initial scale seen in our tiny laboratory. changed back in order to refute disagreement, not only over the Cyclopsian local frame after Any theory based on a false the Einsteinian argument, simultaneity of the flashes but leaping from it either to a model of the universe is false. which naturally will not agree also which came first. However, microcosm (an abstraction) or The stationary sun and stars with the author's assumptions. when Dick and Harry made to the macrocosm (another model is as false as the flat I must point out that I neither allowance for the velocity of abstraction). For those bogged earth model in explaining the agree or disagree with light and of their respective down in the mud of our local Doppler shift of receding Einsteinian Relativity, but trains, all agreed that the frame the golden oldies are galaxies. Hence Einstein's self - surely a principle that can be flashes had been truly quite accurate enough for contradictory assumption that demonstrated to work would simultaneous in their present everyday use - may they rest as his `fixed stars' were require a very strong argument frame of reference. Old Lorentz in their wellies. stationary in Newton's to topple. in the corner muttered A pleasantly harmonic stationary space, the magnitude comparing G.R. Moore something about the orchestration of an original of a star's red -shift is a function sums of pairs of Braintree the theme, Mr Hodges! Let us of the intensity of the star's measurements, as well as the Essex rename it the Planck- Hodges gravitational field. Proved differences, but a game of Constant, whose dimensions mathematically, of course. dominoes was now in progress I have been following the are Md2 /t, or in this context M.G. Wellard and this was not taken up. arguments about Einstein's Mdc, where d is the single Kenley Harry remained train hypothesis with Had Dick and directional dimension of linear Surrey on their trains for ever, each amazement and incredulity. movement of a quantum of would have been confident that There have been so many energy towards a mass M: the the lightning strikes had NOT RELATIVITY assertions and counterclaims change occurs at c (regardless been simultaneous. Both would In Dr W.A. Murrays' article on that now we cannot see the of the speed of approach) and have been correct, even though Relativity (WW May, 84) some wood for the trains. represents the change of state the order of occurrence was not assumptions were made that I In the February 1985 issue, of mass from which we deduce the same. feel were not quite as cut and Messrs Marquis and Scott the existence of energy, even in I trust that this incident dried as he made them seem. Murray fall into opposite ends the case of human receptors explains the Firstly, Time Dilation has of the same trap, in describing adequately (for those who possess them). situation, and will terminate been experimentally apparently similar but actually The photon leaving an atom this particular dispute. demonstrated with the aid of different cases. is a little more tired than the R. Priestley the atomic clocks on board the In Mr Marquis's case, M' and one arriving, having wound it Southsea later Apollo space missions. M perceive the flashes up a bit during its brief stay. Hants These results agreed closely simultaneously, but will It's that entropy thing. with those predicted by Special measure different diptances. Now, gentlefolk, what Relativity. The error here is to transfer Let there be a pyramid upon an happens to the energy radiated Secondly, relativistic measurements from one world ever - changing foundation of by an atom which is moving at principles have been shown to to the other. Scott Murray's information, its four courses the speed of light? Seemingly it affect sub - atomic particles observers would measure being (upwards) systems, is caught in the act of being travelling at speeds in excess of identical distances, but perceive scientific laws, abstract laws, radiated, so what happens to 70 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com the atom? And what happens to different coordinates with very close to the speed of light, Z80 machine and the 'Turbo an atom rushing at the speed of respect to two sets of spatial so that the time dilatation factor Pascal' compiler. light towards a source of axes which are rotated with was not just marginally larger Professor P.F. Ridler energy? It can only translate the respect to one another; special than one, but over 2.5. The University of Zimbabwe energy (or whatever it does to relativity says that something measurements (see refs) agreed Harare it) at the speed of light: one rather similar occurs with mixed with the special relativity likes to imagine that there is a time and space axes. predictions to better than 0.5%. limit for relativistic mass just as If his Fig. 5 had really been a C.F. Coleman ELECTRO- there is for everything else. Minkowski diagram he would Wantage Might the four horsemen of have shown the t -axis along the Oxon REDUCTIONISM quadrature have a little line labelled M, and the x-axis Thank you, Wireless World, for something to say upon the along the line between the References coining the useful term: electro- matter? Or the mass-energy points labelled Ayres, D.S, Cormack, A.M, (wrongly) reductionism, to describe the dualism? Or are we coming to A' and B'. With respect to those Greenberg, A.J Kenney, R.W, fashionable variety of the monistic conclusion that two sets of axes the lightning Caldwell, D.O, Elings, V.B, Hesse, W.P, and Morrison, R.J, Phys Rev intellectual suicide. But anyone there is no such thing as strike at A at time zero in the Lett 21(1968)261. can disprove it; we do not need energy, that all mass is embankment frame would be Greenberg, A.J, Ayres, D.S, an irrational leap of faith. inherently static, all movement represented by the point Cormack, A.M, Kenney, R.W, The failure of rationalism being imaginary and causation labelled A', which has the Caldwell, D.O, Elings, V.B, to account for your own non -existent? coordinates Dr Murray Hesse, W.P, and Morrison, Rj, consciousness means that it is Thank you for your calculates with respect to these Phys Rev Lett 23(1969)1267. a rotten theory. So its failure to revelation, Mr Hodges: wellies two sets of axes, the address values, human nature rot eventually. But do tell us; in embankment axes being and ultimate questions is only considering the photon, who are oblique. Similarly the strike at to be expected. they that play pass -the- parcel? B would be respresented by the We cannot answer whether a J.A. MacHarg point labelled B'. The sloping machine could have a conscious Wooler lines through the points labelled mind until we have a model that Northumberland A' and B' would then represent D.C. SUPPLIES predicts the know fact of human the world lines of A and B, awareness. while vertical lines through It may be helpful to Dr Smith In the February Letters Dr It is the reductionist who is those points would represent to have two additional Scott Murray once again quotes forced to a leap of faith that the world lines of the observers references brought to his - Einstein with the provisos (as science will one -day be able to on the train who are present at attention. These are: judged from the embankment) tackle consciousness. What is the lightning strikes, A' and B'. 1. Walz, F.C. and Burkhard and (considered with reference consciousness? What is colour? The points labelled (wrongly) Analysis of Capacitive to the embankment) faithfully We divide colour into the A and B represent nothing in filtering of full wave included, and once again objective wavelength and particular, but the cuts of the rectification' International proceeds to argue as if he were physiology model, and the line through them with the J. Elect Engng 1967 5 pp blind to their presence in the sensation. We divide morality text, as I previously pointed out world lines for A and B would 563 -572. represent the positions relative 2. Ridler P.F. 'Analysis of into behaviour, absolute moral in the December 84 letters, and imperatives, and subjective to the train of those observers single phase capacitor input AJ. Clayton in the January conscience. Science refuses to at the train time of the rectifier circuits' Proc. IEEE letters. touch the absolutes or the encounter between M and M', 1712 December 1970 pp However the real crunch subjectives. And consciousness represented by the intersection 2261 2266. comes with the second half of - is both indisputably factual, and of the t' and x' axes. An his letter, and with his Schade's original work was subjective. important feature is that the description of Figs 5 and 6 as extremely good for the full and Which leaves a fact hanging. lines labelled 'c', which Minkowski diagrams. A basic half -wave rectifiers, but for the Which destroys the garbage. represent light rays, bisect both feature of a Minkowski diagram voltage doubler circuits waas makes monkeys of them the angle between the x' and t' Which is that any event or encounter seriously in error due to a false all, as, no doubt, they would axes, and the angle between the which is represented at all is assumption. Also his work was agree. x and t axes, which means that represented by one point and clone at a time when the low D.H. Potter one point only. Thus Dr both the train and the values of load resistance embankment observers Axminster Murray's figures and the imposed by solid -state circuits Devon discussion in which he talks imterpret the light flashes as were unusual and it did not about a single event being travelling at the speed 'c'. predict the instantaneous represented by two distinct Almost any question one can minimum voltage which is RAILROADING points show not only that he ask about the interpretation of needed to ensure that doesn't understand Minkowski events by the train and regulators do not 'drop -out'. RELATIVITY diagrams, but also that he embankment observers can be The writer can supply, for doesn't even understand the read off this diagram. non -commercial users, a listing Over the last year Dr Murray physical interpretation of Dr murray asserts that direct of a Pascal program which will has used a lot of your column Lorentz transformations. In fact demonstrations of any produce instantaneous inches attacking Einstein and they relate the coordinations correspondence between the minimum output voltage, peak - his theories. I have no attributed to a given event predictions of special relativity peak ripple voltage, peak particular objection to this as a relative to the two and the workings of the world rectifier current and r.m.s. sport, but in his case both of noncoincident sets of time and as it is are 'conspicuously non- rectifier current, given the the main lines of his arguments position axes which according existent'. The prediction of time values of WC'RL and r/R where are based on easily to special relativity are used by dilatation was verified over C is the filter capacitance RL - demonstrable fallacies. any two observers such as M fifteen years ago by load resistance and r is the With regard to Einstein's and M' who are at rest in two measurements of the lifetime of equivalent source resistance. "rare but crucial conceptual distinct inertial frames. No one pi mesos travelling with respect The calculations take about error", Dr Murray asks us to worries about a point having to the laboratory at a speed eight seconds using a 4MHz believe that Einstein tells us ELECTRONICS & WIRELESS WORLD JUNE 1985 71

www.americanradiohistory.com FEEDBACK

that when the train is moving, ideas in the form that in the Newtonian theory. By the end both the light flashes reach M' absence of matter, light travels of the 19th century the cracks NEXT MONTH together. Since he twice quotes with a definite speed c that does were beginning to show: by for us the passage where not depend on the motion of its now the evidence against it is Among the features in the Einstein says precisely the source. It is worth our while to overwhelming. Fortunately July issue is a Z80 -based opposite, it is hard to see the take a further look at this Einstein realised that the basic telephone call- charge justification for such an assumption. inconsistency in Newtonian indicator which, among allegation. Einstein says quite Suppose for a moment that theory that was causing all the other facilities, provides a clearly that M' will see one flash we invert these characteristics, trouble was that the existence running total cost. It is so that the light does not travel of absolute space and absolute usable anywhere in the before the other, and this is world. based on the argument that M with constant speed, and that time was not compatible with sees them arrive together. speed is dependent on the Newton's principles. John Linsley Hood Since at that moment M and M' source's motion. In the first Fortunately for us, too, he describes a mains power do not coincide, it is a physical case, the speed would have to produced in 1915 the necessary controller intended mainly impossibility for the flashes to depend upon some function of correction, otherwise the "baby for use with a photographic reach M' together, and we time /distance. The alternative with the bathwater" brigade enlarger to ensure stability hardly need to invoke that it might be totally random would long ago have been of light output, but useful for other application as well. It Minkowski to tell us this. Now belongs, I screaming for us to abandon think; to the realm of uses triacs to control the what is a those principles, too. Of course physical impossibility science fiction, and it could amount of a mains cycle in one frame of reference is still hardly depend on the value of it is a profound emotional shock passed to the load. a physical impossibility in any some local field, because there to find that all those terrible other, so the statement that M' is no matter to anchor it to. consequences are only the Ken Smith writes of his work sees one flash before the other The consequence of time/ logical outcome of Newton's with young people and is an absolute statement for this distance dependence is that any principles, and I don't blame electronics. His views are experiment. Of course, there is change in the position of the anyone for hoping they will go provocative and may raise a no denying that if the conditions source would result in a change away if we pretend they are not few hackles amongst those there. It is interesting that of a more conservative for simultaneity had been met of the "local" value at every disposition. in the frame of reference of the other point in space. No matter many scientists are just as train, those flashes much whether the observer's motion irrational as the rest of us. indeed arrive at M' together. enters into the final equation or Finally, Dr Murray is highly The impossibility of this is proof not, this change in value would dogmatic about the non- that the events were not be detected by that observer, existence of direct simultaneous in the train's who would thus be able to demonstations of the frame of reference. Which is detect any motion of the correspondence between the precisely what Einstein said. source. The same thing "workings of the world as it is" The other argument concerns happens if the value is altered and the predictions of the the constancy of the speed of by the source's motion. The theory. I would refer him to the light. Dr Murray is one of the "local" value will change, and experiments of Hafele and very numerous band who tell us though the observer would Keating in 1971, who set out to that Einstein's "second again be able to detect the see if the predictions of theory postulate" says that the velocity source's motion. But to detect about clocks could be Correction of light is the same for all such motion is a violation of confirmed. They were. Ivor Catt has asked me to point out observers despite their mutual Newton's principle that no (SCIENCE vol. 177, 1972, an error in his letter on The Catt experiment is relative motions. It doesn't. exists that p.68ff). Anomaly in the May issue. On page This is a paraphrase of the capable of detecting absolute Alan Watson 18, the penultimate line of the conclusions reached from the rest or uniform motion. This Pollensa second paragraph should refer to experiment of the two similar must be applied equally to the Mallorca the conductor, not the dielectric. laboratories passing in space light and its source as it is to and the light at the centre of everything else. The conclusion Amorphous metals, previously only possible to produce in each flashing as they draw is clear. The requirement that strips on 0.05mm thick, have now been made 1mm thick level. This makes it a little light travels at constant speed using a technique known as rapid diffusion. The picture difficult to support the and that the speed is shows X -ray diffraction photographs of a nickel- zirconium contention that this is an independent of the source's sample. In A, typical X -ray reflexes of crystaline metals "irrational assumption ", or that motion comes directly from can be seen from an NiZr sample before annealing. After Einstein "accepted it without Newton's principles, and in annealing, B, the sample is amorphous and causes evidence ". We need to go introducing his "second diffusion. rather further back in the postulate" Einstein introduced argument to find what the no new information not already "second postulate" really does implicit in those principles. This say. puts the mathematical When he set out to save arguments into their correct Maxwellian theory, Einstein perspective. As Dr Murray encountered therein the concept says, they are circular and do of the aether. The not constitute a proof of any characteristics of this where assumption at all, only being a that light would be propagated demonstration that the through it at constant speed, conclusions can be handled and that any motion of the mathematically. I suggest that source through the aether that is all they were ever would not alter this speed. The intended to be. analogy of sound through air is In saving Maxwellian theory, apt. Einstein adopted these Einstein found the way to save

72 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com Disc preamplifier by Richard Brice This valve design with no overall feedback uses passive equalization and a cascode input stage. I designed this disc preamplifier reduce the effect of noise in the conductance of Via. the upper diagram. A complete working on three assumptions. following RC network. Equalization components are valve is used for V1. Of the The first is that good valve For a high -gain stage, the shown boxed. You may want to remaining three valves, one half amplifiers sound better than obvious choice of valve is a pen- calculate values for the network is used for one channel, the good solid -state ones. Secon- tode but these valves generate more accurately than I have. At other half for the other channel. dly, records sound better when more shot noise than triodes the expense of the convenience Total gain is around 40dB and passive equalization is used and because the cathode current of using easily obtainable high distortion is calculated as well lastly, amplifiers sound better splits between the anode and accuracy capacitors, the below 0.1% for 10mV r.m.s. when loop feedback is not used screen. The amount of shot network could operate at a input a 1kHz. Distortion is and linearity is an inherent part noise depends on valve con- lower overall impedance which mainly produced by the triode of the gain block. struction. Good low -noise pen- would thus reduce the noise directly following the equalizing The only problem with pas- todes are expensive so I chose contribution of R. network. sive equalization is overloading a cascode circuit. Current consumption is low, It's all too easy to jump to of the first stage due to high - The second valve, Vib contri- at around 11mA for both chan- conclusions but I, together with level treble signals. A valve with butes little to noise; total stage nels, so a very smooth h.t. sup- interested friends and musi- a high- voltage supply handles noise is substantially that of Via. ply can be obtained using simple cians, consider this circuit to be high -level signals and provides Gain obtainable is approx imat- RC filtering. To keep hum to a as good as or better than my good linearity but the first stage ely the product of the anode minimum, a 6V d.c. supply previous design using a fre- must also have high gain to VII, and the working mutual feeds the heaters as shown in quency- dependent shunt 5532 op -amp. In turn, this circuit had

MJ15015 proved better than any series (on heatsink) feedback equalization circuit and better than shunt - feedback circuits using simple transistor triples. 2200p Set 6V d.c 25V voltage to all 2N697 A d.c. regulated supply 470» heaters 2200» 10k 25v feeds the valve heaters to reduce hum, top. The T47» o cascode input circuit feeds a passive equalization Note Supply eft fully floating. Frame onnection only at network, tinted area, whose VI valve base. component values are a compromise, bottom.

To other B9A channel 11mA both channels h h n +350V k° g' 1M 18k .1.47y 2W 9Z kt 100k aZ E- htap 100k 1On' & ECC83 V1b DISC EQUALIZATION ECC83 r------250k V1 a - .(12AX7 (I log _ ECC83 ECC82 R e N1(12AX7) (12AU7) 250k

C1 < 1M -01 CZ ** ll 36k > 100» 1k 330p 1k 330p 47k 1k2 tt tt 1M 1k8 100n 8n2 500k 22k 400V 22k Op

I Oov t Adjust to suit cartridge I-----

* With R1, this forms IEC -3dB All resistors except* *are 1/2W metal oxide, 2% at 20Hz ** 04W metal oxide, 1% tt Suflex types, 2%

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www.americanradiohistory.com by R.N. Gorgui- Naguib, K.M. Henein and 2 -D digital filter R.A. King design techniques A comparison of different techniques for designing two- dimensional digital filters.

Two -dimensional digital signal pro- - frequency sampling technique cessing is a relatively new field. - window method Frequency sampling technique Almost all of the work reported in this optimal design methods. - This method is based on the principle area has occured during the last 15 Another, different, technique is used that any 2 -D finite duration sequence R.N. Gorgui -Naguib and K.M. years. In spite of its recent origin, in the design of 2 -D f.i.r. filters and is can be represented by its 2 -D discrete Henein obtained their M.Sc. with significant progress has been made in distinction in digital compared to the previous ones. This Fourier transform F(k k2). This is an the analysis, design and imple- communications from the is approximation of the analogue fre- mentation of two -dimensional digital department of electrical frequency transformation. quency response at the appropriate signal processors. This article - engineering, Imperial College, samples, and so h(n,,n2) can be in 1983. focuses particularly on the design In the design of 2 -D i.i.r. filters, on University of London, obtained via the inverse discrete Fou- R.N. Gorgui -Naguib is currently techniques of two -dimensional finite the other hand, 1 -D techniques are rier transform given by h(n n2) _ a research student in that impulse response (f.i.r.) filters and not carried directly to the two- dimen- N -1 N -1 department. infinite impulse response (i.i.r. ) fil- sional case. This is due to the fact that 1 1 +bl R.A. King, who obtained his F(k1,k2) e'2nla ters. in two dimensions the 2 -D z- trans- N, N2 Ph.D. from the University of be factored London in 1978, is a reader in In the case of f.i.r. filters, most of forms cannot generally where the digital communications the methods used for the design of into lower order systems. This leads one - dimensional (1 -D) filters can be to many design problems, such as the a -kin, bk,n2 section of the department of N, N2 electrical engineering, Imperial extended to the two -dimensional (2- difficulty in determining the stability College. D) case: as well as in finding an efficient reali- And, since for the designed filter,

zation where the coefficients of the N; -1 N 1 _ transfer function may be truncated to H(zl,z2) I : h(n1,n2) . z1"'. z2` a reasonable number of bits. Because n; -0 N,-o of the these difficulties very little then the frequency response may be work has been done on designing 2 -D calculated by substituting the value of i.i.r. filters. h(nl,n2), obtained from the inverse Consequently, we concentrate discrete transform, in the z- trans- more on the design techniques of 2 -D form equation given above and by e;w, f.i.r. filters and give a brief survey of putting zl = and 22 = e,w =. This some design principles for 2 -D i.i.r. gives filters.

Two -dimensional f.i.r. filter design

F(kl,k2) +w;.w,.k,.k, (a) (b) If h(nl,n2) is the impulse response of EE 2 -D filter where n1 and n2 are finite Fig. 1. (a) Linear and (b) log magnitude spatial frequency and defined over the range where response of a 2 -D frequency sampling digital low -pass filter

for the case where N1 =N2 =25 and for a specified set of OSn,SNI-1 1 . exp(1). exp(2) frequency bands. N,N2 and

1 iwN, and exp(i) -e On25N2-1 eli(2xk,/N,-001 1 - then the system function of a 2 -D f.i.r. filter can be expressed as As in the 1 -D case, the above relation is called the frequency interpolating N¡1 Na-1 function and it forms the basis for the H(z1,z2) - E E h(nl,n2) . zl"' z2 "` design of 2 -D f.i.r. digital filters using n;-a n,-o the frequency sampling technique. where H(z1, z2) is the 2 -D z- transform This function expresses the interpo- of the finite length sequence h(n1 , n2). lated frequency response as a linear The convergence of the z- trans- combination of its frequency sam- (a) (b) form is guaranteed because the above ples, and Fig. 1 shows the frequency equation has finite limits on all the response of a low -pass filter designed 2 -D Kaiser Fig. 2. Type and frequency responses of a summations and as h(n1,n2) is through this method. window defined as bounded, soish(n1,n2).zi Again, as in 1 -D case, the interpo- w(nl,n2)- Io,a1- /nl2 +n2`) /14 /Io(a) bounded for finite values of z1 and z2. lation effect may be highly reflected in where a =5.0 and io(x) is the modified zero-order Bessel As the z- transform converges every- the oscillations that occur in the function. (a) is a perspective plot of the window and (b) the where in the z1 and z2 planes for finite transition region since peak in -band that fil- and out -of-band ripples may develop 2 -D amplitude response. sequences, this guarantees ters designed from finite sequences at the edges of the passband and stop- will be stable. band respectively.

76 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com computationally intractable because Two-dimensional i.i.r. filter design The Window method of the extremely high number of var- iables involved in the computations Although much research has recently The window method can be directly and because of the number of con- been done on half -plane filters, extended to 2 -D f.i.r. filters where straints that have to be set to solve the almost all of the work reported in this the 2 -D impulse response sequence problem. area is concerned with the design of h(n1, n2) is multiplied by a 2 -D window causal, quarter -plane stable filters function, w(n1,n2), defined equal to from two different approaches: the zero outside a certain region of inter- Frequency transformation method est. frequency and the spatial domain This is an efficient technique deve- This results in truncating the approaches. Fig. 3. Spatial frequency loped by McClellan for the design of In the frequency domain case, most impulse response to obtain a finite response of a digital filter 2 -D f.i.r. filters consisting of mapping of efforts can be grouped matrix of finite dimensions and is the design designed by means of the an optimal 1 -D f.i.r. filter into its 2 -D into two categories: those involving expressed as follows h'(n n2) - McClellan transformation counterpart. spectral transformations and those method for Nt = NZ = 27. 0 tended to x ing to the rectangular window in the are obtained by rotating the 1 -D fil- the 2 -D case, amongst them, the win- case of one dimensional design) is ters and then converting them into dow method proves to yield good 2 -D defined as Then multplying both sides of the their digital two -dimensional equiva- +w,n.) non -recursive ideal low -pass filters. O4n1áN, -1; equation by e+)(w,n, a real function lent via a 2 -D bilinear transformation w(n n2) - 1 The other two techniques dis- 1 HR(eiw,, e).0 may be defined as O cos n,w1 cos n2w2 , transform coefficients are allowed to n, -0 n,-0 terion to reach a best approximation Digital Filters by Spectral Transforma- of the spatial response. Unfortu- tions, Ph.D. Thesis, Imperial Collge, Uni - vary and are solved by an optimization versity of London, 1978. routine. which corresponds with HR(eiw,, e1 ) nately, as with other 2 -D i.i.r. design 5. J.H. McClellan: Design of two dimen- However, a direct multiple techniques, this approach does not sional digital filters by transformations. exchange algorithm such as the An example of spatial frequency lead to stable filters. Furthermore, it Proc. 7th Princeton Conference on Infor- a mation Sciences and Systems, 1973, pp Remez exchange algorithm devised response of a digital filter designed by may lead to filter whose impulse 247 -51. for 1 -D f.i.r. filter design cannot be this technique is shown in Fig.3. response does not adequately meet 6. S.K. Mitra and M.P. Ekstrom (Editors): directly extended to the 2 -D case. This design method appears to be the prescribed specifications. Two -Dimensional Signa] Processing, for many filters However, a technique has been Benchmark Papers in Electrical Engineer- This is because of the alternation the most efficient and ing and Computer Science, vol.20, 1978. problem which is not directly general- of practical interest the resulting 2 -D developed which relies on the fact 7. B. Nowrouzian: Space Domain Design izable in the 2 -D case. approximation is nearly optimal in the that, by using an infante sequence and Stability of N- Dimensional Recursive On the other hand, although theor- Tchebycheff sense. rather than of finite length, the least Digital Filters, M.Sc. Thesis, Imperial Col- mean square solution would then lege, University of London, 1976. etically the problem is in principle Moreover, higher order transfor- 8. L.R. Rabiner and B. Gold: Theory and solvable by means of linear pro- mations may be developed to give a necessarily lead to a stable filter. But Applications of Digital Signal Processing, gramming, practically it becomes better approximation. the main disadvantage of using such a Prentice Hall, 1975. ELECTRONICS & WIRELESS WORLD JUNE 1985 77

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so that the peak value of the cur- rent through the capacitor is given by: (V; n V°) P 2fLV; (18) Because the ripple current has a triangular waveshape, the r.m.s. value is: --- Now using these results, we can proceed to get: a) the ripple voltage across the e.s.r., which is simply: Fig. 11. Ordinary diode Fig. 12 S.m.p.s. output circuit, compared with fast -recovery showing `invisible' (V t V°) V, X ESR AVM - type. components of Co. f L V, (20) AQ ó b) the peak to peak voltage across AV"D di - Co 8 fz Co dt the e.s.l. by means of: ó ( UL (ESL) d 8fzCo L which on the positive ramp gives: again, v_;_Vo ó- n Vo - V, and on the negative ramp: from 5.

i° (ESL) (V; -n Vo) Vo Fast edges far - AV°D (produces 8f2LC0V; "glitches ") The peak to peak voltage across the e.s.l. is the sum of these: - Thus the output ripple is the sum AVa,, - XESL of all these and it can be a compli- (21) cated, noisy residue. c) finally the ripple across the Commutation effects in the fly- actual capacitor. back circuit impose considerably worse constraints on the per- of the filter. In particu- The charge going on and off the formance lar, the flyback choke leakage capacitor AQ, is represented by inductance significantly affects the shaded area on Fig. 13. the performance, particularly the effect of the e.s.l. The analysis is &e - AREA = ¡base X height involved.

1 TadiTó 2 2 dt 2 Fig.13. Output ripple is sum and: of all these components. BOOKS

Designing Microprocessor- basic concepts of reliability, types International Electrotechnical 0 8359 2125 5. A -level style based Instrumentation by of faults in digital circuits and how Vocabulary, chapter 521: textbook covering basic theory, Joseph J. Carr: Prentice -Hall to model them, test generation, Semiconductors and Integrated units, resistive and reactive International, 323 pages, hard fault -tolerant design of l.s.i. and Circuits. International circuits, phasors and complex covers, ISBN 0 8359 1270 1. v.l.s.i. chips, self -checking and Electrotechnical Commission (3 numbers, resonance, transformers, Practical guide to microprocessors fail-safe logic and design for rue de Varembé, Geneva), 90 a.c. systems and non -sinusoidal (the Z80 in particular) and their testability. pages, soft covers, Sw.Fr.103. waveforms. Rather expensive. support chips, and how to How to render `reverse recovery interface them to the outside Going Online 1984, ed. Jacky time' and several hundred other world. Later chapters deal with Deunette: Online Information phrases into German, Spanish, Microprocessors: Hardware, basics of data conversion, Centre (Aslib, 26 -27 Boswell Italian, Dutch, Polish and Danish. Software and Design Applications, transducers, sample- and -hold Street, London WC1N 3JZ), 60 A4 Translations and fuller by Wunnava V. Subbarao: Prentice - circuits and interfacing keyboards, pages, soft covers, £5. What explanations are given in French, Hall International, 364 pages, hard switches and displays. services are available, how to use English and Russian. covers, £30.85, ISBN 0 8359 4394 them and how much they cost. An 1. A self -teaching book for the Fault Tolerant Hardware extensive list of addresses covers Fundamentals of Electric engineer or student. Describes Design by Parag K. Lala: UK user groups and system Circuits by David A. Bell (of eight -bit processors in general and Prentice-Hall International, 263 operators on both sides of the Ontario, Canada): third edition, 8085, 6800, 6502, Z80 and 1802 in pages, hard covers, £24.95, ISBN Atlantic; there is also a useful Prentice -Hall International, 847 particular. Numerous design 0 13 308248 2. Chapters cover bibliography. pages, hard covers, £32.90, ISBN examples. ELECTRONICS & WIRELESS WORLD JUNE 1985 79

www.americanradiohistory.com COMPACT EOM DIGITAL AUDIO Channel code and By J.R. Watkinson disc format -2 How information is organized on the disc surface

The last article in this series time display in the player. If the several adjacent symbols des- discussed channel code and block rate is multiplied by 588, troyed by an error burst become showed how binary data is the number of T periods in a single- symbol errors spread adapted to a form which suits block, the master clock rate of more widely. the characteristics of the 4.3218MHz results. From this There are a number of inter- medium. This part explains the maximum and minimum fre- leaves used in CD each with a how information is organized on quencies of e.f.m. , 720kHz and specific purpose; the full struc- the disc surface. 196kHz, can be obtained using ture is shown in Fig. 7(a). The Fig. 6 reveals the timing rela- the run -length limits. first stage of interleave is to intro- tionships of the CD format. The Each data block contains 24 duce a delay between odd and sampling rate of 44.1kHz with non -contiguous audio bytes. even samples. The effect is that 16 -bit words in left and right Their sequence and their rela- uncorrectable errors cause odd channels results in an audio data tionship to the redundancy bytes and even samples to be destroyed rate of 196.4kbyte /s (k s 1000). is discussed next. at different times and interpola- There are 24 audio bytes in a data The error correction system tion can then be used to conceal block, so the block rate will be has to deal with large burst errors the errors, with a reduction in resulting from surface contami- audio bandwidth. The odd /even 196.4 nation and the technique of inter- interleave is performed first in kHz = 7350Hz. leaving reduces the amount of the encoder, as de- interleave in 24 redundancy necessary'. The the player will be the reverse If this block rate is divided by 98, principle is that by storing data in order, and interpolation is the the subcode block rate of 75Hz a non -contiguous fashion, last process. An odd /even delay results. This frequency will be 5. Error Correction Techniques in Digital of two blocks permits interpola- Fig. 7(a). CD interleave divided down to provide running Audio, John Watkinson. Ibid. tion in the case where two uncor- structure.

A L6n 12n-36AL - -72BL L6n+2 -128AL - -164BL L6n+4 - R6n - 35ç3ÁgRR

R6n+2 - 415AR - -451BR R6n+4 507AR - 12n -543BR u v 1 IN r O symbols OUT-0- A - L6n+1 - 12n -778AL - 814BL L6n+3 -870AL -906BL L6n+5 - 962 AL -998 BL R6n+1 - 1065AR -1101 BR R6n +3 I -1157AR A -1193BR R6n+5 -1249AR 12n -1285BR

P symbols

Delay Unequal delays Invert redundancy even samples from m ( gives non -zero P/0 two blocks to 108 blocks with zero data) Calculate 4 bytes - 0 reduncancy Delay every other from 24 data bytes symbol 1 block Re -order incoming samples 16 bit samples Calculate 4 bytes to seperate become 8 bit P. redundancy odd and even symbols A, B from 28 data + 0 bytes

80 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com DIGITAL AUDIO -11011111

Audio 441kHz

Left right 16 bits 16 bits

Audio Subcode e.f.m. data rate byte rate symbol rote 196.4k byte is 72 kHz 254k Hz (1.5712M 157.6k (2M bit /s 1 bits /s I bits /s)

96

Maximum Master Data Subcode 1Hz =6 recorded T rate clock block rate block rate playing time frequency 4.3218 MHz 7350 Hz 75 Hz display 720kHz Fig. 6. The frequencies of

=22 x72 the various events in 11 compact disc timing are 11 intimately connected - as Sub ode the diagram shows - and Min'mum be recorded Obit rate the relationship cannot frequency 54k bit /s broken. It should be self - in Mure 196 kHz I Detoiled frame part of series) evident that the drop time code should not be fed into a CD cutter. rectable blocks leave the error correction system, Fig. 7(b). Fig. 7(b). Odd /even Left and right samples at the L6 interleave permits the use same instant form a sample set. of interpolation to conceal As the samples are of 16 bits, uncorrectable errors. each sample set will be of four L7 L9 L11 R7 R9 R11 L10 L12 R8 R10 R12 Odd /even re-order bytes, AL, BL, AR, BR. Six sam- IL8 116 ple sets form a 24 -byte parallel L13 L15 L17 R13 R15 R17 L14 L78 R14 R16 R18 word, and the C2 encoder pro- R20 R24 duces four bytes of redundancy L19 L21 L23 R19 R21 R23 L20 L22 L24 R22 etc. Q. By placing the Q symbols in No I Delay blocks the centre of the block, the odd/ LS RR1 174 R,RR1 R, even distance is increased, per- á L1 L3 R3 R5 L16 L18 4 1 16 R18 mitting interpolation over the lar- ó L7 R7 R9 L22 L24 R20 Rn R24 gest possible error burst. The 28 rn L9 L11 R11 L20 Interleaved c blocks bytes are now subject to differing Q

L17 R13 R15 R17 L26 L28 L30 ' 26 R28 R30 delays, which are integer multi- á° L13 L15 R ples of four blocks. This produces 121 L19 L23 R19 R21 R23 L32 L34 L36 R32 34 R36 a convolutional interleave, where one C2 code word is stored in 28

different blocks, spread over a R.lit RI Ñ 11 G5 R1 43 g5 114 116 ld& R16 distance of 109 blocks. a At one 17 19' R7' R9 R11, Gross error, instant, the Cl encoder á 4 126 122,,124»RYt1 Rn 424, will be presented with 28 bytes - two blocks destroyed which have come from 28 differ- S L13 L15 L17 R13 R15 R17 L26 L28 L30 R16 R28 R30 ent C2 code words. The Cl a R32 encoder produces a further four L19 L21 L23 R19 R21 R23 L32 L34 L36 R34 R36 bytes of redundancy P. Thus the Delay 2 blocks I delay Cl and C2 code words are pro- No Following an M.Sc. course at duced by crossing a data array in L3 R5 Southampton's Institute of Li Ls R1' R3 R4 R6 two directions (`cross interleav- Sound and Vibration, John ing'). Watkinson worked in L11 R7 R9 a11 L8 L10 L,2 R8 R10 R12 De-inter- research before joining The final interleave is an odd/ leave even symbol L,ß L15 Digital Equipment output delay which L17 R13 15 R17 .14 116 i tie ï4 16 causes P code words to be spread Corporation, first as a field over two data blocks on the disc, 119 L21 L23 19 '11 R23 LZO 172 L24 1120 R22 R24' engineer, later as an as shown in Fig. 7(c). This instructor, specializing in mechanism prevents small ran- L2-A L3 L4 LS L6-+ L7.1 RZ R3 R¿ RS R6 R7« Interpolate mass storage devices. He dom errors destroying more than eddsfram joined Sony Broadcast in [L-+L -+L IRR +R I 1982 specialising in one symbol in a P code word. The 8 9 L10 11 L12 8 9 R10 11 R12 choice of eight -bit symbols in the professional digital audio and e.f.m. channel code assists this L13 L14 L15 L1 L17 Lt 'l3 i R15 R16 R17 R181í Interpolate timebase corrector training, strategy. evens from and is currently training R R21 R23 odds The expressions in Fig. 7(a) L19 2Ó L21 La L23 LR19 R2Ó manager at Ampex determine how the interleave is International. ELECTRONICS & WIRELESS WORLD JUNE 1985 81

www.americanradiohistory.com DIGITAL AUDIO

calculated. Fig. 7(d) shows an to provide error flags for the Q encoder produces a 14T pattern example of the use of these system. The P system can how- for every 8 -bit symbol, and sync. expressions to calculate the con- ever correct single symbol patterns and merging patterns tents of a block and to demonstr- errors. This mechanism will be are multiplexed in. ate the cross interleave. described in greater detail in a The next article in the series The calculation of the P and Q later part. assembles the disc, optics, ser- Fig. 7(c) The final interleave redundancy symbols is made Fig. 8 the encoder modulates vos and error correction system of the CD format spreads P using Reed-Solomon cyclic poly- the cutting laser. Audio and sub - to form a CD player. code words over two blocks. nomial division. The P redun- code data streams are supplied, Thus any small random error dancy symbols are primarily for and the cross interleaved block can only destroy one symbol the purpose of detecting errors, structure created. The e.f.m. in one code word, even if two adjacent symbols in one block are destroyed. Since the P code is optimized for single symbol error corrections, random errors will always be corrected by the CI process, maximizing the burst correcting power of the C2 process after de- interleave

Constraint length of 109 blocks 3 blocks 5 blocks

Fig. 7(d) Because of cross - interleave, the 28 symbols from the Q encode process Q code word (C2) are spread over 109 i Symbols blocks, shown hatched. The Disc blocks i final interleave of P code of words, as in Fig. 7(c), is 32 symbols 41 C shown shaded. Result of the each latter is that Q code word has 5,3,5,3 spacing rather than 4,4. 111174 al 4P symbols 1 NE

P interleave

Fig. 8. CD encoder modulates cutting Laser. Audio samples 32 bytes 33 14T symbols 14 e.f. m. 588T blocks are cross -interleaved and per block per block symbols G.) 7350Hz combined with subcode data. These 8 -bit symbols are Symbol delay encoded into 14T e.f.m. Left Cross interleaved efm. symbols. The packing Audio 3T packing Reed - Solomon encoder generator prevents run - Right encoder length violations and - i. Packing To laser generator modulator provides d.c. content control via 3T packing symbols. The Subcode Subcode - Sync pattern e.f.m. symbol delay allows encoder the packing generator to look generator ahead. Two of the many functions of the timing 1 byte 24T sync generator are to switch in per block pattern subcode bytes (left) and to Timing assemble blocks by selecting Subcode /audio generator Sync/packing/data syne patterns, data and packing (right). 82 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com CABLE T.V. HEAD END AND REPEATER AMPLIFIERS

SINGLE CHANNEL AUTOMATIC GAIN CONTROL AMPLIFIERS TAG4863 Gain 48dB, maximum output 63dBnV. Regulator + or - 6dB. Power requirement 14V 210mA. TAG4063 Gain 40dB, maximum output 64dBmV. Regulator + or - 16dB. Power requirement 14V 210mA.

SINGLE CHANNEL AMPLIFIERS TSS4663 Gain 28 -46dB adjustable. Maximum output 63dBmV. Power requirement 14V 170mA. TSS3062 Gain 12 -30dB adjustable. Maximum output 62dBmV. Power requirement 14V 26mA.

DRIVER AMPLIFIERS TS1030FM FM driver amplifier. 100 Gain. Maximum output 30dBmV. Power require- ment 14V 10mA. TS103083 Band Ill driver amplfier. 10dB gain. Maximum output 30dBmV. Power requirement 14V 10mA. TS1030UHF UHF driver amplifier. 10dB gain. Maximum output 30dBmV. Power require- ment 14V 10mA. TS1040S Single channel UHF driver amplifier. 10dB gain. Maximum output 40dBmV. Power requirement 14V 10mA. (Quote channel required).

DISTRIBUTION AMPLIFIERS 7E2042 Domestic distribution amplifier. 1 input, 1 output. Gain 20dB. Maximum output 42dBmV. TE1638 Domestic distribution amplifier. 1 input, 2 outputs. Gain 16dB. Maximum output: 2 at 38dBmV. TS2046 40- 860MHz. Gain 20dB UHF. 18dB VHF. Maximum output 46dBmV. TS2846 40- 860MHz. Gain 28dB UHF, 22dB VHF. Maximum output 46dBmV. TS2845 Separate UHF /UHF inputs, Gain 28dB UHF, 22dB VHF. Maximum output 46dBmV. TS2054 40- 860MHz. Gain 20dB UHF, 18dB VHF. Maximum output 54dBmV. TS2060 40- 860MHz. Gain 20dB UHF, 18dB VHF. Maximum output 60dBmV. TS5565 Gain 55dB UHF, 55dB VHF, 42dB FM. Maximum output 65dBmV. CHANNEL CONVERTERS TCUU UHF -UHF Single channel converter. Gain adjustable +2dB -16dB. Maxi- mum output +26dBmV. Crystal controlled oscillator. Power requirement REPEATER AMPLIFIERS 14V 25mA. (Quote Channels required). TSC3660 Repeater. Gain 16 -36dB UHF, 10 -30dB VHF. Maximum output 60dBmV. TCUV As TCUU except UHF to VHF converter. (Quote Channels required). TSC3665 Repeater. Gain 16 -36dB UHF, 10 -30dB VHF. Maximum output 65d8mV. TCVU As TCUU except VHF to UHF converter. (Quote Channels required). TSC3060 Repeater. Gain 10 -30dB VHF. Maximum output 60dBmV. QUALITY AT LOW COST TAYLOR BROS (OLDHAM) LTD LEE STREET, OLDHAM - TEL. 061 -652 3221 - TELEX 669911

CIRCLE 18 FOR FURTHER DETAILS. IDS900 F O R T H C O M P U T E R ewra Build the TDS 900 into your products, program it NEWRAD INSTRUMENT CASES LTD with a VDU and your Unit 19, Industrial Estate, Gore Road forecasts become fact. New Milton, Hants BH25 6SJ Tel: New Milton 0425 621195 NOW FROM WE HAVE INCREASED THE RANGE £99 OF OUR SUCCESSFUL NM40 ENCLOSURES

I Single board computer. 12k RAM and 8k ROM (expandable). * All C -MOS for lower power. FORTH language. Compiled and fast. On -board screen -editor, compiler and debug facilities. * Easy connection with serial Beautifully made 19 inch Rack HEIGHT DEPTH PRICE and parallel channels, A /D, D/A Mounting enclosures complete with 2U 150 £16.50 converters, triacs, printers, heavy gauge chassis and top and 2U 250 18.60 keyboards and displays. bottom covers. Front, Side and Rear 2U 300 18.50 panels are aluminium and flat for easy 3U 150 18.00 machining. These panels are located 3U 250 20.00 with heavy duty aluminium extrusions. 3U 300 22.00 4U 150 20.30 Front and Rear panels are satin 4U 250 24.50 anodised. Covers are finished in 4U 300 27.40 Triangle Digital Services Limited cream. 100a Wood St_ Waltharnstow, London E17 England 6U 150 25.00 Telephone. 01- 520 0442. Telex 262284 (Rel 7751 6U 250 29.00 6U 300 35.00 Agents in USA. France. Switzerland. Netherlands. S. Africa, Australia

PRICES ARE EXCLUSIVE OF VAT. P &P £3.00 Vi CIRCLE 29 FOR FURTHER DETAILS. CIRCLE 21 FOR FURTHER DETAILS.

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Transportable Unix

Trumpeted as the world's first a 9in diagonal. There is an HP- transportable, fully integrated lB ( =GPIB) interface, an input Unix-based computer the port for a mouse, and 512K of Hewlett -Packard Integral PC, ram with expansion slots for Incorporates multi- tasking, more (up to 1.5MByte) and /or Multi- window facilities and for a V23 modem. By using bus combines processor, display, expanders, memory can be printer and disc drive all in one increased to 5.5MBytes. 11.2Kg (251b) package. The Eventually the computer will be Unix operating system is on a able to address up to 8MB of 256K rom, the computer is built user ram. An additional 32K around the Motorola 68000 ram is used for the screen processor, uses the fast H -P memory. For software thinkjet printer and has a 3.3in development, C and Technical double- sided, double- density Basic are available, as is a wide disc drive. range of applications software. The computer operates from Stocked by Rapid Recall a.c. mains supply. Display is Ltd. ,Denmark Street, High provided by an amber Wycombe, Bucks. HP11 2ER electroluminescent screen with EWW205

Mobile tv aerial Patents have been applied for looking at the polar field the design of a u.h.f. tv strength diagrams; it is not receiveing aerial for use on worth reproducing them as they vehicles. It is an adaptation the are just circles! Suggested quad configuration. The applications are for use in objective behind the design was coaches, cars, caravans and on to evolve an aerial that would water craft. Because vehicles provide an omnidirectional field often operate in areas of low pattern where the direction of signal strength, the aerial is the wanted transmission station provided with a broadband changes as the vehicle moves amplifier giving a 22dB gain from one location to another. Of over the whole u.h.f. band. The r course it is possible to redirect UK price of the Omnimax I_1 j 1 # f 1' # a Yagi -type aerial but this Aerial, including the amplifier ! 4 . 4' 1 i re14 requires physical movement of and 5m coaxial cable is £39.50 tr1fr®-.141're the aerial and the new design inclusive. Maxview Aerials Ltd. t; eliminates this. The success of Setchey, King's Lynn, Norfolk. the design can be judged by PE33 OAT. EWW213

low contact resistance ensures Tiny trimmer low r.f. loss and high Q. The Another world's first is claimed capacitior has been vibration for this device. The smallest tested to 40G with no variation ever precision trimmer in the set capacitance value. capacitor. Designed to provide The use of the CP series of screwdriver adjustable tuning of trimmers eliminates the cost of high frequency circuits (up to wirebonding small capacitance 5GHz), The Voltronics CPA10 elements, allows the rough achieves it small size by tuning of several stages before eliminating the outer case and final tuning, eliminates the cost internal screw mechanism. of matching and tuning Extreme precision is used to integrated circuits and the r.f. manufacture the parts and the loss is lower than for ceramic Teflon dielectric is fused to the elements.Pascall Electronics stainless steel moveable Ltd, Hawke House, Green shuttle. Both the contact clamp Street, Sunbury-on- Thames, and the shuttle clamp are gold - Middlesex. TW16 6RA. plated beryllium copper. Very EWW211

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OSCILLOSCOPES NEW EQUIPMENT TEKTRONIX 465 Dual Trace 100MHZ Delay HAMEG OSCILLOSCOPE 605. Dual Trace 60MHZ Sweep now Delay Sweep. Component Tester £515 GOULD 054000 DIGITAL STORAGE Dual HAMEG OSCILLOSCOPE 203.5. Dual Trace20MHZ Trace £550 Component Tester £264 Happy Memories TELEQUIPMENT 075 Dual Trace 50MHZ Delay Sweep £350 BLACK STAR FREQUENCY COUNTERS. P &P £4 COSSOR CDU150 Dual Trace 35MHZ Delay Meteor 100 100 MHZ £99 - Part type 1 off 25 -99 100 up Sweep £200 Meteor600- 600MHZ £126 S.E. LABS SM111 Dual Trace 18MHZ AC or external Meteor 1000 -1GHZ £175 4116 200ns 125 1.15 1.10 DC operation £175 BLACK STAR JUPITOR 500 FUNCTION 4164 150ns Not Texas 2.10 1.90 1.80 TELEQUIPMENT S54A. Single Trace 10MHZ GENERATOR Sine /Square /Triangle 0.1HZ - State Sold SOOKHZ. P&P £4. £110 2114 200ns Low Power 1 75 1.60 1.55 TELEQUIPMENT D43. Dual Trace 25MHZ ... £110 2016 15Ons 2.75 2.50 2.30 TELEQUIPMENTS43.SingleTrace25MHZ ....£75 HUNG CHANG DMM 6010. 3; digit. Hand held 28 6116 200ns Low power 7.75 Call Call ranges including 10 Amp AC /DC. Complete with 6264 150ns Low power 9 80 8.75 8.40 batteries 8leads. P &P£4 £16 2716 450ns 5 volt 3.85 3.45 3.30 SIGNAL GENERATORS 2732 450ns Intel type 4 75 4.25 4.10 OSCILLOSCOPES PROBES. X1: X10 P&P MARCONITF995A /2 AM /FM 1.5- 220MHZ. £200 Switched 2732A 350ns 5.25 4.69 4.50 MARCONI TF144H/410KHZ -72MHZ £65 £2 £11 ADVANCE type SG63EAM/FM 4- 230MHZ ..£150 2532 450ns Texas type 3.85 3.45 3.30 ADVANCE type SG63A AM/FM 7.5 - 230M HZ. £75 5t4" FLOPPY DISK DRIVES 2764 300ns Suit BBC 4.20 3.80 3.60 ADVANCE type SG62B AM 150KHHZ - TANDON; Height. Brand New 27128 300ns Suit BBC 5.60 5.00 4.80 220M HZ Double ADVANCE type 62 AM 150KHZ - 220M HZ £35 Double Sid d Density £100 Low profile IC sockets: Pins 814 16 18 20242840 SHUGART type SA460 Double Sided Double Density. 80 Track. Ex -eq £75 P &P all drives Pence 12 13 14 16 18 242738 MULTIMETERS £5. Available now - The ROAM BOARD for the BBC Micro. Reads Mk V. Complete with Roms via a Low Insertion Force Socket and saves their batteriesesandleadsforonl STEPPER MOTORS contents as files, then reloads a file into its sideways Ram as PHILIPS DMM 2517. 4 digit. Auto ranging. Type 1.200 Steps 4 Phase (5 wire) 12/24V 25oz required. Full details on request. Complete with Batteries, Leads (Un-used) P&P £95 yp p inch. 2/ "dia £15 AVO TEST SET No 1. (Similar to AVO 8X). Complete Type 2.6/12 Steps 3 0 hase12 /24V.l /. " dia. £2ea5 with Batteries, leads& carrying case. £80 TTL, wide stocks at low prices with DIY discounts for £7.50 74LS series AVO Model 73. Pocket Multimeter (Analogue) 30 Type 3. 24 Steps 4 wire 5V 3.3A 0- 250rpm 0- starting at a mix of just 25 pieces. Write or 'phone for list. ranges. Complete with batteries A leads £25 20OPPs21 dia £10 ea AVO 72 -Similar toabovebut no AC Current range Typee 4. 200 Steps 120V (3 wire) 25oz inch. with Batteries & Leads £18 2£4 P&P and VAT extra Please add 50p post & packing to orders under £15 and VAT to total. NOW ONLY £12 p &p £3 Access orders by 'phone or mail welcome. AVO TRANSISTOR TESTER TT169 This IS A VERY SMALL SAMPLE OF STOCK, Non -Military Government & Educational orders welcome., £15 minimum. Handheld. GO /NO GO for In -situ Testing. SAE Or Telephone for LISTS Complete with batteries, leads 8 instructions. Please check availability before ordering. Carriage all units £12 VAT to be added to Total of Goods 8 All above Instruments in Working Order and Carriage Supplied with Manual HAPPY MEMORIES (WW), STEWART OF READING Newchurch, Kington, _. 110 WYKEHAM ROAD, READING, BERKS RG6 1 PL Herefordshire HR5 3QR. Telephone: 0734 68041 Tel: (054 422) 618 Callers welcome 9 a.m. to 5.30 p.m. Monday to Saturday inclusive CIRCLE 84 FOR FURTHER DETAILS. CIRCLE 81 FOR FURTHER DETAILS.

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Circuit diagrams 1oI24576Ci H2 on a micro Using a light pen directly on the package and it is also easy to 470 470 screen and a library of pre- create further symbols with the programmed images it is light pen, on a magnified scale, possible to draw circuit even when drawing is in diagrams, with a BBC Micro, progress. very quickly and obtain a high - Printout is obtained from any quality printout from a low -cost dot matrix printer that can dot matrix printer. The provide dual -density graphics. 5 Cirkwick kit consists of The printout is produced in one software on a disc and a continuous action using a 2 6 lightpen which incorporates a screen dump routine that 74 L3393 switch. The graphics image of manipulates the drawing file so the circuit is displayed on the that the correct portion of the 11 screen which acts as a window diagram is on the screen while 10 on a much larger 'virtual' being printed. The drawing is 9 screen; eight times the size of stored in memory as a file of the screen in use. Although the symbols and co- ordinates and 12 system has been designed for may be manipulated by other 2 i 15 14 1r12 electronic diagrams it may also programs if desired. The be used for flow charts, power software costs £ 19.95 and the systems, pipework diagrams, lightpen £25.00 (inclusive). 74L5151 fluid logic diagrams and many Datapen Microtechnology Ltd., EXAMPLE ONLY other engineering applications. Kingsclere Road, Overton, 11 10l 91 5 61i¡ A large number of electronic Hants. RG25 3JB. EWW203 symbols are included in the

Fast tape storage A new wafer tape drive is load the full 64K capacity of the available for the Comodore 64 computer takes 30s, compared computer which loads faster with 2min for a Commodore than cassette and is claimed to dics drive and 23min for a be more reliable and, because Commodore tape. The drive of the slow serial interface with complete with the operating Commodore discs, is even system, one blank cartridge and faster than disc. The medium is one game cartridge costs just a continuous loop of 1.6mm under £ 100. A wide range of magnetic tape in a tiny software is already available on cartridge, somewhat similar, Wafadrive cartridges including though a little larger and more many games, a word processor robust, to the Sinclair and a spreadsheet program. Microdrive. The interface Other versions are planned for software for the Quick Data the BBC micro. The Rotronics Drive includes an audio Wafadrive for the Sinclair simulation which makes the Spectrum uses the same Commodore think that it is mechanism. Dean Electronics communicating with a normal Ltd, Glendale Park, Fernbank cassette and this routine takes Road, Ascot, Berks. SL5 8JB up as much time as the actual Solid -state disc EWW 201 Based around the Fujutsu double density disc. Full transferring of the program. To 1Mbit bubble memory, the emulation is included in the SSD1 has been designed to internal electronics so that the emulate a 5.25in floppy disc in unit may be plugged into the applications where extra disc drive port of most reliability and ruggedness are microcomputers. It operates required. With no moving parts from a single 5V supply. Track it has none of the potential access time is about 150ms and mechanical problems of disc data transfer rate is 125KByte /s. drives and offers a high Bubble memory has an error immunity to the effects of rate of 1 in 1016 and a calcu- temperature, humidity, dust, lated m.t.b.f. of 400 000h. shock or vibration. The units cost £960 including The unit can take two 1Mbit two cassettes and each cassettes offering 125KBytes additional cassette is £260. each, or the equivalent of two Tempatron Ltd. , 6 Portman single- sided, single -density disc Road, Battle Farm Estate, drives. The two cassettes can Reading, Berks. RG3 IJQ. be combined to offer the EWW216 equivalent of a single -sided ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com NEW PRODUCTS

Pascal on the QL STE -Bus to Micro interface The USCD p- system has been microcomputers. The system is translated into a format usable very fast; 700 lines of Pascal When an STE -bus system is moves. The BBC can be used on the Sinclair QL computer. can be compiled in a minute on connected to a BBC Micro using as the only processor in the This includes compilers for the QL, twice as fast as a Arcom's Beebop interface system or as one processor in a Pascal, Fortran -77 and USCD similar operation on the IBM board, both systems benefit. multiprocessor system. It is Basic, a screen editor, filer, PC. Standard benchmark tests The BBC can have access to possible to use an STE utilities, print formatting and show that the system takes the STE's data acquisition and processor board for applications the Advanced Development QL from its current position of control features, such as while the BBC provides colour Toolkit. USCD Pascal is widely 31st in the league table to 6th 1MByte addressing range and graphics. STE, which is used in as a teaching tool in place,much faster than the IBM 4Kbyte of input /output space; reaching the final stages of universities and colleges and PC and close to the speed of the and the STE system gains a fast standardization by the IEEE in was chosen, for example, by IBM AT. Pascal or Fortran -77, and easy means of developing the USA, offers a variety of the Open University for their together with a full set of Basic programs, and the BBC's expansion boards including course on structured development utilities, is colour display facilities. digital and analogue interfaces programming in Pascal. available for £99.95, The The interface is a single and real-time clocks. The The P- system also provides a Advanced Development Toolkit Eurocard which sits in an STE interface includes two v.i.a. useful software development costs £49.95. TDI Software card frame and is connected to chips which send and receive environment with its integrated Ltd, 29 Alma Vale Road, the BBC through the 1MHz bus data between the BBC and STE editor and compilers. Programs Bristol BS8 2HL EWW208 port. A `filing system' eprom is buses with the necessary logic so compiled are highly portable installed in a BBC sideways rom to set up the required bus and may be used on a variety of socket and provides the cycles and an arbiter circuit for computer with an additional set use when the BBC is part of a of STE- oriented commands to multi- processor system. The ranges and accuracies for the Basic interpreter. These Beebop costs about £120. each range are: alternating include dedicated facilities for a- Arcom Control Systems Ltd., voltages, 0- 200 -500V (1.2%); to-d conversions, reading or Unit 8, Clifton Road, Multitester Cambridge. CB1 4BW. A miniature hand -held mult- direct voltages 0 -20- 200 -1000V writing to memory or i/o EEW218 meter includes a socket for (0.8%); d.c. 0- 2 -20 -mA (1.2%); locations, and performing block transistor testing. It is housed Resistance 0- 2- 20- 200kohms in a book - hinged box with a (1%). Transistors up to 1000 manual, battery, leads and a may be tested. Available spare fuse. The instrument through Semiconductor Supplies features a 12mm high 3'/2 -digit International Ltd, Dawson 1.c.d. It has an overload House, Carshalton Road, protection circuit and automatic Sutton, Surrey. SM1 4RS. polarity and zero adjustment. EWW219

Temperature controlled iron

Compact and light the miniature the use of a 50W element and a soldering iron from Oryx has a thermostat. The Oryx 50 iron is preset control adjusted by a fitted with an iron coated, screw which may be between chrome plated screw-on tip 200 and 400 °C. The operating there is a wide range of tips - Coy DIGITAL temperature is reached within available. The bench stand is an MULTITESTER 9v MA 45s from cold and is then optional extra. Greenwood maintained to within ±2%. This Electronics Ltd. , Portman rapid heating and accurate heat Road, Reading, Berks. RG3 control are made possible by 1NE. EWW204

ELECTRONICS & WIRELESS WORLD JUNE 1985 87

www.americanradiohistory.com Now Thurlby makes logic analysis affordable ! from the new Thurlby LA -160 £395 +vat 16 channels, expands to 32 2K word acquisition memory Clock rates up to 20MHz Non -volatile reference memory State and timing displays Search and compare facilities Selectable display formats Hard -copy data print -out An oscilloscope and logic probe are not enough to unravel the complexities of today's electronic equipment. A logic analyser is as essential for observing digital signals as an oscilloscope is for observing analogue signals, and now Thurlby puts one within every engineer's reach. Contact us now and get the full technical data. Thurlby Electronics Ltd III Thurlby New Road, St.lves, Huntingdon, designed and built in Britain Cambs. PE17 4BG, England. Tel: (0480) 63570

t 114 1.E :31 FOR FURTHER DETAILS. The world's most advanced low-cost bench multimeter! Thurlby 1905a £325 ± VAT A complete high performance bench DMM

5 /t z digits; 0.015% acc; 1 0V, 1 m 2 1 nA. Full ac and current functions as standard A sophisticated computing and logging DMM Linear scaling with offset; null /relative Percentage deviation; running average s dBV, dBm general logarithmic calculations Limits comparison; min and max storage 100 reading timed data logging RS232 and IEEE -488 interface options Thurlby Electronics Ltd New Road, St.lves, Cambs. PE174BG III Thurlby CIRCLE 32 FOR FURTHER DETAILS. Tel: (0480) 63570 designed and built in Britain Add 8 channels to your 'scope New Thurlby 0M358 multiplexer £169 +vat The Thurlby 0M358 gives any oscilloscope an 8 channel display. Observing many waveforms simultaneously can be essential when analysing sophisti- cated equipment. Application areas include microprocessor based products, data transmission systems, A to D converters, frequency synthesizers etc. The 0M358 is ideal for digital equipment (it can often solve problems that would otherwise need a fast logic analyser) but, unlike dedicated logic test instruments, it is equally suited to analogue waveforms. The 0M358 has a bandwidth of 35MHz and 3% calibration accuracy. Each input has an impedance of 1MS2 - 20pF and accepts signals up to ± 6V. An 8 channel, 4 channel, or single channel display can be selected with triggering from any channel. Colour data sheet with full specifications available. Electronics Ltd 0M358 with two BNC III Thurlb y I /\ New RoadThurlby , St.lves, Cambs. cables £197.80 designed and built in Britain PE1 7 4BG Tel: (0480) 63570 (inc P & P and VAT) CIRCLE 33 FOR FURTHER DETAILS. Hitachi Oscilloscopes performance, reliability, value and immediate delivery! Hitachi Oscilloscopes provide the quality and performance that you'd expect from such a famous name, with a newly- extended 14 model range that represents the best value for money available anywhere. V-212/222 20MHz Dual Trace V -650 60MHz Dual Timebase V-223 20MHz Sweep Delay V -1050 100MHz Quad Trace (illustrated) V -1070 100MHz Four Channel V-209 20MHz Mini -Portable V -1100 100MHz DMM /Counter V-422 40MHz Dual Trace V -134 10MHz Tube Storage V-423 40MHz Sweep Delay VC -6015 10MHz Digital Storage V-509 50MHz Mini- Portable VC -6041 40MHz Digital Storage Prices start at just over £300 plus vat and that includes a full 2 year warranty. We hold the range in stock for immediate delivery. For colour brochure giving specifications and prices ring (0480) 63570 Thurlby- Reltech, 46 High Street, Solihull, W.Midlands, B91 3TB. CIRCLE 34 FOR FURTHER DETAILS.

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CIRCLE 12 FOR FURTHER DETAILS. CHIP SALE U.S. supplier of RF POWER DEVICES. RF LOWER than domestic prices. Prices current 4164 64K DRAM 150 NS 41256 265K RAM 150 NS POWER Query us for immediate needs. £1.99 each £6.50 each (Upgrade IBM PC + (Upgrade Olivetti M24, A quality source for a complete range of RF POWER devices From 2- - Compaq deskpro etc.) 30MHz, SSB 12.5V 7 28V transistors - 14 -30 MHz CB /AMATEUR 27 -50 Compatables) MHz, low band FM - 66 - 88MHz, mid band FM - 66 - 88MHz, mid band 42128 128K RAM 150 NS Any quantity up to 1,000 FM -156 - 162MHz VHF MARINE RADIO FM -130 - 175MHz HI -BAND £6.50 each pieces. Bulk discounts VHF FM - 108- 152MHz VHF AIRCRAFT AM - 225 40MHZ UHF 28V - (Upgrade IBM PC / -AT) available. 407 - 512 UHF CATV /MATV CLASS A linear transistors -A SMALL indication of types are listed below. SEND FOR OUR FREE BROCHURE AND /OR CONTACT FOR IMMEDIATE QUOTES. MRF450 MRF453 MRF646 BLY88A BLY90 BLY93A .2N3553 .2N4933 .2N5109 .2N3375 .2N5016 .2N5589 .2N4128 .2N5070 .2N5591 .2N6080 .2N4427 .2N5090 .2N5634 .2N6083 .2N4431 .2N5102 2N5918 .2N6084 a TIC Semiconductor Inc. BUSINESS SYSTEMS LTD MAPLE DRIVE, EAST GRINSTEAD, WEST SUSSEX, RH19 3UR 18 WEST 21st STREET NEW YORK, N.Y. 10010 U.S.A. 56, TEL: (212) - 675 - 6722 TELEX: 968003 NYK Tel: 0342 313427 24631/2 CIRCLE 88 FOR FURTHER DETAILS. CIRCLE 42 FOR FURTHER DETAILS.

DGS001 2- MOTOR, HIGH QUALITY REPLACEMENT LINSLEY -HOOD SOLENOID CONTROLLED CASSETTE DRIVE. CASSETTE HEADS 300 SERIES AMPLIFIERS Fully solenoid controlled cassette mechanism suitable for Hi -Fi or digital use. With a logic control board the deck i can be operated by lightweight touch controls or output from micro. Ideal for a. Do your tapes lack treble? A worn heed could be the problem. applications under automatic control T-"sAka replacement heeds could restore performance machines, data Fining one of our such as telephone answering to better than newt Standard mountings make fitting easy and remote control loggers, automatic background music systems. our TC1 Test Cassette helps you set the azimuth spot -on. We are recorders and microcomputer program and data storage. Two the actual importers which means you get the benefit of lower motors and three solenoids control all functions including prices for prime parts. Compere us with other suppliers and seal search in fast forward and rewind. The following is a list of our most popular heads, all are suitable 35 Watt Complete Kit. MosFet 0/P £79.50 Standard fittings include reed switch for auto off. 3 digit counter. for use on Dolby machines end are se- stock. 45 Watt Complete Kit. MosFet 0/P £83.50 stereo R/P and erase Head. HC20 Permalloy Stereo Head. This is the standard head fitted as Reprints of Original Articles from 'Hi-Fi News' £1 no VAT. Overall size 176mm x 130mm x 75mm. original equipment on most decks £5.11 DGS001 Cassette Mechanism. C37.23 Quantity prices on HM90 High Beta Permalloy Head. A hard- wearing, higher per- request. INF140. Full technical specification and drawings Cl. formance head with metal capability £8.06 LINSLEY -HOOD 100 -WATT MOSFET HS16 Sendust Alloy Super Head. the best head we can find. AM VARICAP DIODE BARGAIN Super wide range SMV2012 Longer life than Permalloy, higher output than Ferrite, fantastic POWER AMPLIFIER varicap diodes in matched sets to eliminate tracking errors! frequency response £9.91 Matched 4 only 60p. I only 25p. The very latest ampltier dos et 1 i s.-ed n -Wireless World' Matched pair HOS61 4-Track Head for auto-reverse or quadrophonic use. Full by the renowned John Linsley-Hood. This may now betaken as SET OF 4 COILS to use with above to make long, medium and specification record and playback head , £9.73 the standard by which the rest are judged! Our kit, approved by short wave AM tuner. Normally 30p each. OUR PRICE FOR THE Please consult our list for technical data on these and other the designer, has massive heat sinks and power supply and SET ONLY 55p Special Purpose Heads. 412mm includes all components needed to build. Case size Application circuit using coils and matched pair of Double Mono (2/2) Record /Play head. wide, 254mm deep and 145mm high. Automatic switched INF10 MA481 Latest version SMV2012 varicaps. 35p £8.90 speaker protection is included as standard. Cost of all parts is Replaces R484 168A IF Transformer 30p over 020. Our complete stereo kit price £105.50. SM166 Standard Mounting 2/2 Erase head. Compatible with CFU455F2 IF Filter 50p H0551 4 Track head. 05.90 Suitable PC Board £1.50 above or high LINSLEY -HOOD CASSETTE RECORDER Push Button PC Mounting Wavechange Switch £1.60 H524 Standard Erase Heed. Semi double gap. effi- ciency C1.50 CIRCUITS COMPLETE STEREO TUNER MODULE 11561 Metal Tape Erase Head. Full double gap £4.90 Complete record and replay circuits for very high quality low Three band LW /MW/FM Stereo Tuner fully assembled on PCB noise stereo cassette recorder. Circuits are optimised for our 165 x 85mm. Supplied with Ferrite rod aerial and band switch HS16 Super Quality Sendust Alloy Head. Switched bias and fully wired. Facility provided to drive tuning meter and stereo HART TRIPLE -PURPOSE TEST equalisation to cater for chrome and feric tapes. Very easy to LED. Only needs 12v DC supply. FM sensitivity. 2.5uV. Arks assemble on plug-in PCBs. Complete with full instructions. only £7.99 Inc. Vat and Post. Tuning Scale and accessories CASSETTE TC1 Complete Stereo Record /Play Kit £25.26 £2.99 One inexpensive test cassette enaoies you to set up VU level, VU Meters to suit £2.30 each Special Price for both items bought together £9.70 inc Vat & Post. head azimuth and tape speed. Invaluable when fitting new Reprints of original Articles 75p. No VAT. heads. Only E4.66 plus VAT and 50p postage. CLOCK/TIMER /FREQUENCY METER PARTS frequency Special offer of the fabulous MSM5524 clock. timer and Tape Head De- magnetiser. Handy size mains operated unit STUART TAPE RECORDER CIRCUITS meter chip. MSL2318 prescaler chip and 6LT09 5 -Digit fluores- prevents build up of residual head magnetisation causing noise cent display. These are the 3 primary components for a complete on playback fa. 54. Studio quality record /Play electronics to timing and frequency display system covering the long. medium, Complete Type inaccessible heads _. _ fa 85 bring that old valve machine back to life. Full details short and FM wavebands. Total cost of these parts is normally Curved Pole for £1.30 (No VAT). over C25. OUR SPECIAL OFFER PRICE ONLY C11.90 in our REPRINT INF230 Data on MSM5524 and MSL2318 70p Send for your free copy of our LISTS. Overseas please send 2 INF260 Application Circuit 20p IRCs to cover surface Post or 5 IRCs for Airmail PW WINTON STEREO AMP Crystal 3276.8 KHz [1.90 Please add part cast of post, pa2Ì,ring aria insuranceas hollows: HiFi MosFet Amplifier Kit giving 50 Watts per VIDEO HEADS INLAND OVERSEAS Super video cassette recor- .014% distortion, housed in attractive Heads to suit all VHS, BETA and PHILIPS Orders up to E10 - 50p Please send sufficient to cover channel at Do not take chances with 'near equivalents' there are nine ders. Orders E10 to E49 E1 wood veneered cabinet. Full Kit is normally £109. Write or ring with the - Surface or Air Post as different VHS heads and seven BETAMAX. Orders over £50 -£1.50 keilSPECIAL OFFER, NOW ONLY £89. Reprint of make and model number of your recorder for quotation. Prices required descriptive articles 85p (No VAT) start at [47.25 for VHS and 057.75 for Beta

Personal callers are always very welcome but 24hr SALES LINE I ALL PRICES EXCLUDE VAT please note that we are closed all day Saturday (0691) 652894 UNLESS STATED

ELECTRONICS & WIRELESS WORLD JUNE 1985

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Output power Single -rail quad op -amp for mobile High stability, fast slew rate capacitive drive capability of and wide banwidth are claimed 10000pF. Its high stability radio for the Motorola MC3074 results in a settling time of op.amp, comparable to those l.lus. Suitable for use in For operation between 140 and characteristic associated with battery- operated equipment, 175MHz, the BLV45 /12 power bi.fet devices whilst offering automotive systems and in transistors are intended for use single supply operation with switch -mode power supplies, with v.h.f. mobile radio input common mode range the op.amp can be operated transmitters. They are designed gold metallization. They can down to ground (VEE). In from split supplies as well as for optimun performance under deliver 45 and 74W output addition the NPN output stage single raile if required. Stocked adverse conditions and can power respectively in amplifiers provides a minimum output by Celdis Ltd., 37 Loverock withstand a 20 -to -1 v.s.w.r. powered from a 12V battery. swing 36% greater than other Road, Reading Berks. RG3 under severe output mis -match They offer a gain of 6.5dB at standard op.amps and a lED. EWW221 conditions. They feature 175MHz. Mullard Ltd., internal matching, diffused Torrington Place, London. emitter balancing resistors and WC1E 7DH. EWW220

Alternative disc for Electron

Unlike the disc interface for the real time clock so that file may BBC micro, Acorn's Electron be `date stamped' when saved. has a double density drive and Software included with the would seem to provide all that package includes the ability to may be required. Except that it copy to and from Acorn DFS exclusively uses a 3in drive. discs that can be used with a Cumana have come up with an BBC micro. It is also possible alternative that may be used to format single- density discs with 3.5 or 5.25in drives, for the Acorn DFS. Cumana double or single density, up to Ltd, Pines Trading Estate, 89 file names and an interface Broad Street, Guildford, Surrey. that includes a battery- backed GU3 3BH EWW202

Solid -state relays The chassis mounted versions have three current ratings 10, 25 Designed and manufactured in and 45A r.m.s. for mains power the UK by Allen -Bradley, relays switching. They all offer zero - are available in three formats, crossing switching to reduce two for p.c.b. and on for r.f.i. to negligible levels. chassis mounting. The p.c.b. Applications include switching relays differ in their shapes one a.c. motors, burst fire regulation being flat to allow rackmounting of electric heating elements and the other being mounted with capacitive input power vertically for higher population supplies where the zero voltage density on each board. They are both rated at 3A r.m.s. at 240V a.c. load switching. Dry lubricant in a can

A special anti -stick and mould as video recorders, tape release agent is provided by recorders, typewriters and Electrolube's Dry Film printers. Lubricant. It is designed for use The material is based on where mineral oils or silicones p.t.f.e. It is clean and non -oily, are not appropriate. Especially water repellant, fast drying, suitable for electronics non -flammable and chemically applications, DFL assists in the inert. This enables it to be used insertion of p.c.bs into edge on most materials, including connectors, stops squeaks in leather, wood synthetic or disc drives caused by friction natural fibres, glass, metals and between metal and plastics and most plastics. It is available in improves the action of keys in aerosol cans and in bulk keyboards. It may also be used containers. Electrolube Ltd, for any plastic or plastic /metal Blakes Road, Wargrave, Berks. connectors in such equipment RG10 8AW. EEW207 90

www.americanradiohistory.com of only 10uA. The hybrid is 256K S.RAM mounted in a standard 28 -pin d.i.l. package and there are By combining memory chips standard and military onto a hybrid substrate, it is temperature tolerance versions possible to make up larger available. Manufactured by memories. The C.mos 256 -03 Intergrated Circuits Inc. and combines four ram chip and a available from Pascall decorder to give a 32Kbyte Electronics, Hawke House, static ram, with an access time Green Street, Sunbury-on- of 100ns, an operating current thames, Middlesex. TW16 6RA of 40mA and a standby current EWW222

driven by a 4-pole brushless D.C. fans d.c. motor which features The shapes of the blades and polarity protection and the airflow venturi have been automatic restart. The use of a designed by computer in the p.t.c. thermistor in the drive latest range of 80 and 92mm electronics allows the fan to fans from papst. The fans in start with a very slow ramp -up this range have a depth of only voltage. Papst Motors Ltd., 32mm but may move air up to East Portway, Andover, Hants. 803 /h. The series III Multifan is SP10 3RT. EWW210

The unit has an input for a switching limits inrush current. Computer -video synch 1Vp -p composite video signal. They may be used as A device to allow the as offered by a tv camera, video The 15 -way output is connected and transformer tap changers of computer disc or time -base corrected to the computer which needs to The superimposition for primary disconnect. text subtitles and graphics onto v.t.r. It can also synchronize be slightly modified. It is suitable for driving by relays are an incoming video signal has with lower quality video powered either from auxilliary Bradley logic circuitry. Allen- been developed by CCI recorders such as VHS or power output of the computer Ennia House, High Electronics, Associates under licence from Betamax when it can cope with or can have a built in mains Kent TN8 Street, Edenbridge, the BBC. Having been such errors as a line frequency power supply. The price of the 5LY.EWW217 successfully prototyped the difference of 2 %, 7us line timing basic unit will be £199 without Super Genlock unit will be variation relative to a stable or £249 with a power supply. available very soon. It is reference over one second, and CCL Associates Ltd., capable of synchronising the it will correct a quarter line Beechwood House, Depot RGB and video outputs of a period timing error following Road, Newmarket, Suffolk. BBC Micro to a stable reference head switching in about 15 lines. CB8 OHA. EWW214 Motion sensor

A ultra- miniature precision linear motion potentiometer may be used in short- travel position sensing, in confined places and for linear movement voltage adjustment. The body is 31.75mm long with screwholes for mounting at 25.4mm centres. The shaft, 3.2mm thick has 16.6mm travel. A range of resistances from 1K to 10ohms are offered and independant linearity is specified as 1 %. Spectrol Reliance Ltd., Drakes Way, Swindon, Wilts. SN3 3HY.EWW215 ELECTRONICS & WIRELESS WORLD JUNE 1985 91

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Timing and signature analysis

Standard operating modes of other 8 -bit processors. this 40- channel instrument Additional options include include the ability to save and direct processor access for 6502 recall blocks of data on disk, processors and cross - screen dumps of timing assemblers for 8088 and 68008 diagrams, signatures and the without the need to get printing of data listings and expensive personality modules. dissasembled code. Timing Data may be transmitted waveforms may be labelled to emote stations through a automatically and software modem. enables the user to create a The system is based around a label file or enter labels re- packaged BBC micro with a directly. The instrument has a detachable keyboard. The 24 -bit trigger and area trace housing includes two disc drives with trigger and clock qualifiers and space for such expansions operating up to 10MHz. Each of as a hard disc drive, modem the 40 channels can have up to and a second processor. Lawrie 1K memory allotted to it. T &M Ltd., Mercury House, Standard operations include the Mercury Row, Otley, W Yorks dissassembly of 6502, Z80, LS21 3HE. 6800, 6809, 8080, 8085 and EWW209 Low -cost 8048 development system Writing software for the popular disc or cassette. The unit can 8048 family of single -chip program, read and verify the microcomputers normally 8748, 8748H and 8749H eprom entails the use of an expensive versions and it can act as an microprocessor development 8048 hardware emulator. system. But a low -cost Saldep -48, which costs £925, alternative is now available in was developed in co- operation the form of the Saldep -48, with the Department of development system based on Electrical and Electronic the BBC microcomputer. Engineering at the University of The unit, which is self- Salford. Similar systems are in powered, plugs into the preparation for other single -chip computer's 1MHz bus. The microcomputers, such as the software, provided in eprom, 8051 and 6800, and the IBM includes a text editor for personal computer. entering programs, a symbolic Volex Electronics Ltd., Volex two -pass 8048 assembler and House, Lissadel Street, Salford interactive de- bugging tools. M6 6AP. User programs can be stored on EWW212 8088 educational system The latest in the series of a two -line l.c. display which is cards to be used. This allows programmer, routines to Microprofessor single -board actually a window onto a 20 for memory expansion, RS232c interface with any standard computers is the MPF1 /88 column by 24 lines virtual communications, colour video ASCII terminal, printer driver, which is built around the 16 -bit screen. A full -sized qwerty output and many other facilities and asynchronous Intel 8088 processor. It is keyboard is provided, together in common with the IBM PC. communications routines. Also designed to teach the with a Centronics parallel Standard features include an provided are a cassette fundamentals of 8088 -based interface and a 64 -pin edge on -board monitor with many interface, a power adaptor and a hardware and may also, at connector which allows any interactive sub -routines to aid built in loudspeaker. £325, be used as a low cost IBM -PC compatible expansion the assembly -language Documentation includes a development system. It allows User's manual, monitor source designers to prototype control listing, and a software reference devices for robotics and other guide which introduces 8088 servo -systems and unlike many assembly- language instructions `packaged' computers allows and explains the internal direct access to the processor. working of the monitor system Included in the standard software. Future options software are instructions on include a two -pass assembler writing and debugging with editor, a rom -based Basic programs, and introduction to interpreter and Forth. A low - assembly language and the cost 20- column thermal printer fundamentals of i/o interfacing. is available and an eprom Included on the board is 4K of programmer. Flight Electronics ram (expandable to 24K) and a ltd., Quayside Road, Bitterne 16K rom which may be added Manor, Southampton SO2 4AD. to up to a total of 48K. There is EWW206

92 ELECTRONICS & WIRELESS WORLD JUNE 1985

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BIRD TERMALINE Dummy loads 500 watt cost 50 ohm N connec DC to L Gz £85, X.BAND W M. 9170/9470 Mc /s with meter ind & var I/P atten cased. £23. PULSE GEN Services type CT500 mains 100c /s to 60Kc 3 ranges, delay. var 0 /Ptransis unit in neat case tested. £45. DOSE RATE METERS hand held as 4 ranges 4 to 4000 Mill /Rnht meter indication, reqs 4. HP2 to operate. sensor 4' approx ext size 10%7x8' Beta /Gamma responce. Tested. £75. HEAT DETECTORS for ceiling mounting (not smoke) as N.O. contact protects approx area of 20ft sq, new Chloride with base. £12.50 new 24v Bells for these. £6.50. PARAMETRIC AMP UNITS by Mullard tunable S band self contained unit with N connec, mains operated, with I/P circulator power supply & small blower, in case 9.10x10', tuning by Micrometer head, complete but classed asfaulty by M.O.D. £75. METER IND special purpose with meter 5 -0 -5 Ua 3' dia in neat case. £14.50. BENCH P.U. 240v I/P provides DC smoothed & semi reg 0/P of 28v DC at 15 amps with volt meter, approx size 7.7.16" tested. £38. AVO TYPE CT446 Transis Anylizers provides wide range of tests uses int dry batteries in neat case. £23. MAST ARMY telescopic manual approx 27ft open 5ft closed. £28 guy kit. £8. ELEC CONDS HD type 2700uí at 250v size 5;x3" insul case new. £3.50 ea. ADVANCE A.F. Osc gen purpose, mains, 15c/s to 50Kc 5 & 600 ohm 0/P var tested £29. TERMINAL panel mt insul H.D. type in black. 2 for £2 or 4 for £3.50. SIG GENS Marconi type TF995.A3 CT4201.5/220Mc/s AM /FM tested. £100. MOTOR with gearbox 24v DC We're not kidding. 60RPM approx size 2;x1;1,'. £4.50 V.H.F. AMP /SIG GEN R &S Model ASV 30 /300Mc /s new with book. £95. The following items for callers, Collins R389/URR VLF Rx 15/1500Kc £175. Closed Circ TV system with Cam, lesse, viewfinder. £125, WWV HFStandards Rx all HF chan to25Mc /s 115v. £85. REDIFON G479 This board offers all you need to HF Station 100 watt CW /SSB mains 24v 2 /12Mc /s decade tuned. £345. Amer G.E. 5 circ Nic Chargers 240v a simple controller. And new. £29. L.T. Trans 230v to 20v at 170 amps cont. £55. Mil CT336 Trig Mon Scopes 3" £15 Var res 1 ohm 27 implement amps new. £18 & .72 ohm 50 amps fixed new. £11.50. C.V.T. 230v out 150/250 watt £32. can develop your application on it Above prices inc Carr /VAT. goods ex equipment unless stated new. you List 36 available on request. as well. All you need is access to a VDU since the board comes with its A.H. Supplies. 122, Handsworth Rd, SHEFFIELD. S9 4AE own BASIC interpreter and PROM Ph. 444278 (0742). programmer. On -board is a Z8, 4k of CMOS RAM (expandable to 16k), one ROM socket, 40 lines of parallel I/O and a serial interface. For £169! Keep tabs on those For this and our large range of I/O valuable back issues the boards, give us a call. BIND easy way with purpose - designed binders. They're sturdily made in a black finish with gold blocked title IT.. on spine. Each one holds six efteLT1 issues of Electronics and Wireless World. Arcom Control Systems Unit 8, Clifton Road, Cambridge CB1 4BW £3.45 each (including Telephone: (0223) 242224 FIND postage) from Sundry Sales, Room 303, Arcom products are distributed by Quadrant Blouse, The Crellon: (06286) 4300, Dage: (0296) 33200, Quadrant, Sutton, HI -Tek: (0223) 213333 IT! Surrey SIA2 5AS. CIRCLE 65 FOR FURTHER DETAILS. ELECTRONICS & WIRELESS WORLD JUNE 1985 93

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DISPLAYED APPOINTMENTS VACANT: £19 per single col. centimetre (min. 3cm). Advertisements accepted LINE advertisements (run on): £4.00 per line, minimum £25 (prepayable). BOX NUMBERS: £5 extra. (Replies should be addressed to the Box in the up to 12 noon June 5 for Number advertisement, c/o Quadrant House, The Quadrant. Sutton, Surrey SM2 4AS). July issue PHONE: IAN FAUX, 01 661 3033 (DIRECT LINE) 15% VALUE ADDED TAX NOT INCLUDED Cheques and Postal Orders payable to BUSINESS PRESSINTERNATIONALLTD. and crossed.

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£7,000- £30,000 + CAR * Where does your interest lie: Graphics; CAD; Robotics; Simulation; Image and Signal Processing; Medical; Automation; Avionics; Acoustics; Weapons; Comms; Radar; Opto and Laser? * Experienced in: VLSI; Microprocessor Hardware or Software: Digital and Analogue circuitry; RF and Microwave techniques? * There are hundreds of opportunities in: Design; Test; Sales and Service for Engineers and Managers * For free professional guidance: Call: 0638 742244 (till 8pm most evenings) or write (no stamp needed) to ELECTRONIC COMPUTER AND MANAGEMENT APPOINTMENTS LIMITED FREEPOST, The Maltings, Burwell, Cambridge, CB5 OHB. (1926)

cottget f for your classified adverts (::e Nt ring Ian Faux 01 661 3033

IMPERIAL COLLEGE l'NIVERSITI OF ST ANDREWS Inner London Education Authority Learning Resources Branch, Department of Electrical Engineering S.E.R.C. CASE STUDENTSHIP Television & Publishing Centre, Thackeray Road, London SW8. Appkal ions are invited for a CASE studentship ELECTRONICS TECHNICIAN in .ollahoratinn with the National Physical (£7831 to £8934 inc. under review) I.thura1 n Thr successtul applicant will become Involved In the design and development of detectors. Television Engineer Interferometers and other Corms of quasi-optical Required in the Microprocessor instrumentation for use in the far -infrared Salary range £7836 to £9906 plus £1419 London Weighting Teaching Unit. Duties will include the !millimetre-wove) spectral region. The .student Allowance and an irregular hours allowance of would £228. construction of digital and analogue then become involved in using the new instrumentation at the NI'I. as part of a The Mobile Videorecordin9 Section, which is circuits the repair and modification of programme aimed at providing ways of gaining equipped to broadcast electronic equipment and general a Netter understanding of the behaviour of standard, makes observational classroom recordings for teacher technician support to the teaching fusion research plasmas. It is anticipated that the project would he host education. A Television Engineer is required to join a technical team and research programmes of the suited to a student with a practical outlook who of 8 for operational and maintenance work involving rigging and unit. has an interest in developing his or her skills in the areas nt microwaves. optics and electronic driving duties. Applicants must hold an ONC or full engineering. C & G it certificate, and is essential Applicants should possess for expect to ohtain t Further details, including full job description and application forms that they have substantial experience a good degree in science or engineering OR he of from EO/Estab 1B, Room The London 7PB. of modern electronic circuits. able to a sound hackground of relevant 366, County Hall, SE1 equivalent experience (Please enclose SAE.). The dosing date for completed application Applications giving details of The award is for a period of three years from education, training and experience iistuher 1985 and the successful candidate will forms is 5th Juy 1985. he espec led to register fora higher degree should be sent to:- Departmental futurs at rusts which should include a Ch and Superintendent, Department of the names of two reterces, should he sent to tir This past is suitable for Job -share. Electrical Engineering, Imperial 1. I.esurf. Physics Department h niversity of St College, London SW7 2BT. Tel: 01- ,lndresos. Plic KYt i 9SS. as soon as possible. LEA IS AN EQUAL OPPORTUNMEEEFFS EMPLOYER. 115831 589 5111 Ext. 5105. (2586) (2585)

94 ELECTRONICS & WIRELESS WORLD JUNE 1985

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Professional Career Opportunities The Easy Way to look for your new job from the comfort of your own armchair. Our well qualified consultants will carefully match your requirements against ó appropriate vacancies. TAME (Mr/Miss/Mrs) We have many clients seeking Engineers and Technicians at all levels and we are particularly interested in hearing from you if you have experience in the following:- ADDRESS Signal Processing Technical Sales ATE Programming Radar Systems RF Development Real Time Software POST CODE Your next step is to complete and return the attached coupon or telephone John Prodger on 0442 47311 or one of our duty consultants on 0442 212650 during evenings or weekends. TEL NO

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THE INTERNATIONAL SPECIALISTS IN RECRUITMENT FOR THE ELECTRONICS. COMPUTING AND DEFENCE INDUSTRIES I_

25 -33 Bridge Street, Hemd I It mpstead, Herts., I-11'I IF( NONE CG /HNC DEGREE OTHER

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0 -£6000 £6 -10000 £10 -15000 £15000+

A, ., , - JAI JOB i6s -:- (2584)

The Queen's University of Belfast The Computer Centre If you are a 28 to 38 year old RF design engineer with a desire to learn the HEAD OF HARDWARE SUPPORT Scandinavian way of life - this ad might be the turning point of your profes- AND COMMUNICATIONS DIVISION £14,136 £17,706 sional career. (under review) FINDIT is a small electronics Hi -Tech company closely associated with one of Norways As part of the Senior Management most profitable electronics industries. team reporting to the Director of the Computer Centre, the successful Located in the picturesque city of Trondheim, we are developing sophisticated RF applicant will lead a group of seven staff responsible for the Centre's based mobile systems for relocation of moving objects. hardware data -communications, R & D is the ideal place for elec- development and equipment main- Trondheim, being the number one centre of Norway, tenance programme. The post offers tronics industries. We have a good network if suppliers and necessary services as well an invigorating opportunity to take over a senior managerial, technical as excellent communications. and motivational role in a very active and stimulating University environ- As a result of continued expansion of our development program we need to streng- ment. design team. Applicants, male or female, should then our engineering preferably be university graduates or The candidate should be a graduate electronics engineer. 5 years with the industry is equivalent in electrical or electronic engineering; demonstrating a com- preferable and experience within VHF /UHF circuit design a must. prehensive, in -depth knowledge and practical experience of data- commu- We can offer a starting salary of £18,000- £24,000 according to qualifications and nications, state -of- the-art hardware, a pension scheme. Fees for students at active managerial and technical experience, good fringe benefits and generous expertise and a thorough knowledge Trondheim British School will be paid by us. of the general field of computing. Salary scale (Universities Other You will find an open, young and creative environment where you can see your ideas Related Staff Grade Ill)'. C14,137 - construction, test and evaluation to £17,706 (under review from 1.4.85), progress from initial concepts through prototype initial placing according to age, the pre -production stage. experience and qualifications. Assist- (2576) ance with relocation. Applications, including a full curricu- lum vitae and the names and FOR MORE INFORMATION addresses of three referees should be interested? ASK FOR NJAARD sent to the Personnel Officer, The Still 010.47.7.525872 Queen's University of Belfast, Nor- HESTNES OR EIGIL SOERLI. THEY ARE thern Ireland, BT7 INN, from whom Why hesitate? Call EAGER TO ANSWER YOUR QUES- further particulars may be obtained. (2536) TIONS. collect right away, FINDIT P.O. BOX 2845 today, now! N -7001 TRONDHEIM FINDIT TEL (07) 525872 TLX 55086 FOUND

ELECTRONICS & WIRELESS WORLD JUNE 1985 95

www.americanradiohistory.com Appointments THE START OF CUT THIS OUT! SOMETHING Clip this advert and you can stop hunting for your next appointment. We have a wide selection of the best NEW appointments in Digital, Analogue, RE Microwave, Micro- If you are leaving College and planning a career in modern processor, Computer, Data Comms and Medical Elec- communications or if your present job lacks interest and tronics and we're here to serve your interests. challenge why not join us in GCHQ? Call us now for posts in Design, Test, Sales or Field We are recruiting Service, at all levels from £6,000- £16,000. RADIO OFFICERS TTechnomar& who are after initial training will become members of an l:nt inrrruit l- 1;11m(al Recruitment organisation that is in the forefront of communications 11 Westbourne Grove, London W2, Tel 01-229 9239. technology. Government Communications Headquarters (19351 can offer you a satisfying and rewarding career in the wide field of communications. Training involves a 32 week course (38 weeks if you come straight from Nautical -----xi------x, College) which will fit you for appointment to RADIO r OFFICER. 1 CAPITAL APPOINTMENTS LTD 1 Not only will you find the work as an R O extremely I interesting but there are also good prospects for THE UK's No.1 ELECTRONICS AGENCY I promotion opportunities for overseas travel and a good salary. Add to this the security 1 If you have HNC /TEC or higher qualifications and are I of working for an important looking for ajob in design, test, customer service, technical Government Department and you could really have the I sales or similar fields: start of something new. The basic requirement for the is 2 1 Telephone now for our free )ohs list I job years radio operating experience or hold a PMG, MPT or MRGC or be about to We have vacancies In all areas of the UK 1 obtain a MRGC. Registered disabled people are welcome to Salaries to £15,000 pa apply. 1 Salaries start at £4,762 at age 19 to £5,755 at age 25 and 01 808 3050 1 over during training and then £6,399 at 19 to £8,510 at 25 (24hours) and over as a Radio Officer. Increments then follow I annually to £11,741 inclusive of shift and weekend working allowances. CAPITAL APPOINTMENTS LTD 76 WILLOUGHBY LANE, LONDON N17 OSF I For full details and application form phone 0242 32912/3 (291) or write to: The Recruitment Office A/1108 Bin Priors Road ------J CHELTENHAM (2806) Glos GL52 5AJ

CLIYEDEN TEST ENGINEERS Electronic Engineers - Fbr full systems test on datacommunications networks. Whatyou want, where you want! £8,000 + Wokingham FIELD SERVICE ENGINEERS USA training on ATE systems. TJB Electrotechnical Personnel Services is a specialised appointments Suit experienced repair service for electrical and electronic engineers. We have clients throughout technician. £10,000 + car Woking the UK who urgently need technical staff at all levels from Junior Technician TECHNICIAN ENGINEER to To maintain VAX PDP11 & flight Senior Management. Vacancies exist in all branches of electronics and simulation systems. allied disciplines - right through from design to marketing - at salary to £11,000 Middlesex. TEST ENGINEER levels from around £6,000 - £20,000. Fault -find data -processing equipment to component level. If you wish to make the most of your qualifications and experience and Some systems involvement. move another rung or two up the ladder we will be pleased to help you. c£10,500 Herts SERVICE ENGINEER All applications are treated in strict confidence and there is no danger of Mobile radiocommunications equipment. your present employer (or other companies you specify) being made aware £8,000 + car Hants & Central of your application. London. TEST /SERVICE ENGINEER Repair & fault -find microprocessor based broadcast systems. TJB ELECTROTECHNICAL Please send me a TJB Appointments Registration form: £9,000 + Reading PERSONNEL SERVICES, Phone/write /call Roger Howard C.Eng Name MIEE, Cliveden Technical Recruitment 12 Mount Ephraim, Consultants, 92 The Broadway, Tunbridge Wells, Bracknell, Berks RG12 1AR. Tel: Kent. TN4 8AS. Address Bracknell (0355) 489489 (six lines) (1640) Tel: 0892 39388 (861) (24 Hour Answering Service)

96 ELECTRONICS & WIRELESS WORLD JUNE 1985

www.americanradiohistory.com BroadcasfSystems Engineering Turning top products into total Systems. Established in 1978, to specialise in the high technology field of professional broadcast television equipment, Sony broadcast now has 10 overseas branches providing sales and other specialist engineering support to our customers, in a marketing area that covers Europe. the Middle East and Africa. We now employ 400 staff and enjoy a prominent position as a market leader with a wide range of state -of- the -art broadcast video and audio products. The Systems Engineering Division plays a key role in the success of the Company, designing and equipping complete sound and vision broadcast and recording facilities. These facilities may comprise an entire television studio complex or a single mobile outside broadcast unit, often forming part of an existing, highly sophisticated national broadcast network: or representing a pioneering thrust into one of the world's remoter areas. Applications are now invited for the following challenging opportunities in the Systems Group: Project Engineer Marketing Engineer You will be expected to make a significant As a member of a Specialist Systems Marketing Team, contribution to a project team which will turn a you will be engaged in the conceptual design and design concept into reality. This will involve the costing of broadcast Systems. You must have an ability in -depth design, building and commissioning of to analyse operational and technical requirements and facilities that will satisfy our customers' diverse turn them into practical solutions. needs. To assist. you will be supported by a You can expect to meet a wide range of customers Systems Production Department comprising from Professional Broadcasters and Production Materials Acquisition. Mechanical Engineering. Companies through to National Government Officials Installation and Drawing Office skills. Project in order to discuss their project and offer expert advice. time -scales of 4 -12 months will offer you a To assist in the preparation of detailed proposals you stimulating challenge, and the satisfaction of seeing will have the use of modern computer based graphic your contributions in action fast. design and information processing equipment. Applicants should possess a formal electronics /electrical engineering qualification (a minimum of a Higher TEC) together with experience gained in the electronic manufacturing industry. A television broadcast background would be particularly relevant. The ability to interface confidently with technical customers is essential. Both positions will involve some overseas travel, and full product training will be provided. First class conditions of employment are offered, and generous relocation assistance will be given where appropriate. Our salaries reflect the importance we place upon attracting the best highly skilled engineering staff and keeping them. Please apply in the first instance to David Parry, Personnel Officer with details of your career to date. Sony Broadcast Ltd. City Wall House Basing View, Basingstoke Hampshire RG21 2LA SONY® United Kingdom Broadcast Telephone (0256) 59 5 83 (2590)

ELECTRONICS & WIRELESS WORLD JUNE 1985 97

www.americanradiohistory.com Appointments Philip Drake Electronics is a successful and growing company that has now established itself as the leading U.K. supplier of studio communications equipment and programme quality sound distribution modules to the Broadcasting industry. An increasing workload has lead to a requirement for the following personnel; More PROJECT AND TEST ENGINEERS Project and test engineers are required to work in the Systems Engineering Group which primarily deals with the custom design, Hi-Tech Jobs manufacture and test of studio talkback and intercom systems. Project Engineers should have a suitable engineering qualification and at least two years experience of system /project engineering with £8000 - £20,000 professional analogue equipment. The work includes detailed system As a leading recruitment consultancy we have a wide design, liaison with customers, and technical support for production selection of opportunities for high calibre Design, Development, and test. Systems and supporting staff throughout the UK. Test Engineers should have analogue experience but have the ability If you have experience in any of the following then you should to adapt to digital technology. The job entails testing custom built be talking to us for your next career move. equipment from prototype circuit boards to complete systems ARTIFICIAL INTELLIGENCE IMAGE PROCESSING studio and providing after sales and is MICRO HARDWARE & SOFTWARE GUIDED WEAPONS service support. The post one which OPERATIONAL RESEARCH RF a MICROWAVE OPTICS provides excellent opportunities for advancement within the systems MATHEMATICAL MODELLING SIMULATION C group. HIGH LEVEL PROGRAMMING SYSTEMS ENGINEERING ACOUSTICS & SONAR FLUID DYNAMICS RADAR SATELLITES AVIONICS CONTROL ANTENNA Opportunities exist with National, international and consultancy companies offering excellent salaries and career TECHNICIAN /JUNIOR ENGINEER advancement. An opportunity exists for a Technician /Junior Engineer to join our For Free and Confidential career guidance call John Spencer product development team. The successful candidate will be involved or send a detailed C V.. Please quote in all aspects of design from concept to production. He /she will work reference WW /3. primarily with analogue circuits although there will be involvement Skyquip Technical Services with digital circuits. An ability to work with minimum supervision is 85 High Street, Winchester, Hampshire. S023 9AP essential and it is expected that the successful candidate will be Tel: Winchester 10962169478 124 hours) (2579) qualified to TEC or degree level although ability is more important. Experience of the professional audio industry would be an advantage. ti) x ,dnt rec rwtrnent for Aerosire. Defence & Communications Industries

TVS, the ITV programme company serving the South SOFTWARE ENGINEER and South -East of England, requires an We are currently looking for two suitably qualified software engineers to strengthen our development team. The successful candidates would be required to write software in PASCAL and ASSEMBLER for the MC68000 family and must be able to work on Engineer their own initiative with minimal supervision. The ability to - communicate ideas clearly is essential.

In addition to attractive salaries, the company offers a non- contributory pension scheme, BUPA membership and a pleasant vision Line Up working environment in newly constructed premises in Welwyn Garden City.

Central Technical Area If any of the above positions appeal to you please apply in A vacancy has arisen within the Engineering Division writing including your current CV or phone Jenni McCoy on Welwyn Garden City (0707) 333866 for an application form. for a Vision Line Up Engineer to be based at the TVS Studio Centre in Maidstone. Philip Drake Electronics Ltd., Applications are invited from qualified engineers who 37 Broadwater Road, Welwyn Garden City, have preferably worked in a Central Technical Area Herts AL7 3AX. within a broadcast television company; however, candidates from related engineering backgrounds will (2589) be considered. We will also consider the possibility of a trainee to fill this position. In this instance, applicants should have dmke `A' level qualifications in both mathematics and physics. If you think that you fit the bill, please apply in writing giving full details of your qualifications and ELECTRONICS experience, and quoting ref no. 15/SE/85, to: Personnel Manager ENGINEER Required by fast growing company. An electronics engineer, competant in digital and analogue systems. Must be capable NV TVS of working without supervision in the production, testing and Vinters Park, Maidstone, trouble shooting of our range of instruments. While, a Kent ME14 5NZ practical approach is essential, the successful candidate will TVS is an equal opportunities employer. be qualified to at least HNC standard. Salary level will not be a problem for the suitable candidate. Write in the first instance detailing age, qualifications and salary expected to: Mr. B.E. Stevens, Managing Director, Hounsfield Test Equipment, 37 Fulleton Road, Croydon, Surrey. CRO 6OR (2575)

ITV for the South & South - East (2581)

98 ELECTRONICS & WIRELESS WORLD JUNE 1985

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LEWISHAM AND NORTH SOUTHWARK HEALTH AUTHORITY SOUND ENGINEER Applications are invited for the newly- created post of GUY'S HOSPITAL TECHNICAL ASSISTANT to the studio's HEAD OF TECHNICAL SERVICES. DEPARTMENT OF CLINICAL PHYSICS AND BIOENGINEERING

The successful candidate will work in the field of SOUND ENGINEERING for film post -production, and must have a ELECTRONICS TECHNICIAN - thorough theoretical background in electronics and light MEDICAL PHYSICS TECHNICIAN III electrical engineering. Ability in project management is a priority, involving audio and control systems, planning, specification and installation, with skills at the drawing board This active, well established and well equipped Department and development bench. A working understanding of provides a physical sciences service for a number of clinical is departments in the Hospital. We require a technician to join our remedial and routine maintenance required, and electronics servicing group. This work includes the maintenance experience with video systems would be an advantage. and servicing of a varied range of medical electronic equipment The prospects for advancement would be best for an and covers all aspects of patient orientated equipment from fixed applicant having a good manner and appearance, an even installations to small portable instruments. temperament, and the ability to deal with clients, to handle Experience in this type of work would be an advantage, but administrative duties and to write clear English. The candidates with HM Forces experience or having a good suggested age range is 28 to 40 years. background of TV servicing are encouraged to apply. In conformity with studio practice, membership of ACTT (the An ONC /HNC or equivalent qualification, followed by at least three Association of Cinematograph, Television and allied are required. years technical experience, Technicians) would be expected, and due weight would be Day release is available for approved studies for higher given to applications from present members. Non -members qualifications. should be willing to apply for acceptance by this union. Please forward a full c.v. (quoting ref: ACN /GFL /A) to:- Salary: £7,492 p.a. rising to £9,367 p.a. inc. Personnel Dept., Pinewood Studios, Pinewood Road, Iver, Bucks SLO ONH. Mr. F. Trowell For further information contact Tel:lver (0753) 651700 Tel: 01 -407 7600 Ext: 2574 (2535)

Application forms are available from the Personnel Department Guy's Hospital, St Thomas Street, London SW1 9RT. Tel: 01 -407 7600 Ext: 3471 quoting Ref. No: P/153. Closing date for completed applications: 31st May 1985. (2588) YOU ARE UNDER RECORDING STARTERS ORDERS STUDIO MAINTENANCE For the biggest Mobile Rally in the South Of England on July 14th 10 MANAGER a.m. to 5 p.m. at the Brighton Race Ground. Huge "Bring & Buy UNIVERSITY OF LEICESTER Required for major North London Studio CHARING CROSS complex. Applicants should have a Stall ", 20,000 sq.ft under cover DEPARTMENT OF minimum of 3 years experience in this exhibition area, plus attractions for COMPUTING STUDIES HOSPITAL field. Knowledge of Studer tape the XYL and children, restaurant machines, SSL desks an advantage. facilities. The Rally which caters Post of Experimental Officer ELECTRONICS for the whole family. Talk In S22 Applications are invited for a post of TECHNICIAN Phone: Chris Dunn and 3.5 Mhz. Admission £1 in the Department of children free if accompanied by an Experimental Officer (MPT IV) Computing Studies, available from 1st July 01 -459 8899 adult. For further details ring 1985. Technician required to work 07918 -5103. (2595) Applicants will be expected to have with a team engaged on the (2593) some hardware design experience and it maintenance of a wide range would be an advantage to have a suitable of electro- medical equipment. postgraduate or industrial background. The successful applicant will The Queen's University of Belfast The post will involve working with mem- The Computer Centre bers of staff to develop both hardware and largely be involved with repair, College of Technology, COMPUTER DEVELOPMENT ENGINEER software for research and teaching, and will calibration and safety checking. Yarmouk University, Jordan. also involve some supervision of labora- £11,676 - £14,925 (under review) ONC or equivalent is essential Faculty and technical staff positions in Engineer tory classes and student projects. The The computer development and a mechanical aptitude EE Technology available Sep 85 and be a senior member of the Hardware Department uses mostly 16 -bit and 8 -bit will would be an advantage. Feb 86. Relevant educational Division, microcomputers and experience of this Support and Communications qualifications and demonstrated type machine would Salary: £6488 p.a. £8188 which is responsible for the Centre's data - of be an advantage. - teaching /industrial abilities required. Initial salary will depend on qualifica- p.a. inclusive. communications, hardware development Areas of interest include, but are not maintenance programme. tions and and will be on the and equipment experience For further details please contact the restricted to Power & Machines, scale £6,600 to £10,330. The post offers an invigorating opportunity Unit Personnel Department, Communications, Electronics, to take a technical role in a very particulars may be over senior Further obtained Riverside Health Authority, Parsons Computers, Controls, from the Registrar. University of Leicester. active and stimulating University environ- House, Charing Cross Hospital, Instrumentation, and Manufacturing. ment. University Road, Leicester LE1 7RH, to Fulham Palace Road, Hammersmith Responsibilities include teaching and Applicants, male or female, should whom applications should be sent on the W6. Tel. 01 -748 2040 extn 2992. advisory duties in a quality preferably be university graduates or equiv- form provided by 31st May 1985. (2580) undergraduate EE Technology (2577) alent in electrical or electronic engineering: program, as well as assisting in the demonstrating an in -depth knowledge and overall development of the College. practical experience of data- communica- Rank and Salary commensurate with tions, state -of- the -art hardware and active AUCTION NOTICE ELECTRONICS qualifications and experience. An technical expertise. excellent benefits package. Positions Salary scale (Universities Other open until filled. Letters of Held Every Other Friday Lots Include: Related Staff Grade II): £11,676- £14,925 Auctions application, detailed resumes, copies (under review from 1.4.85), initial placing Electronic and Electrical Equipment, Components, Test Gear, of official transcripts, and at least according to age, experience and qualifica- Radiotelephones, Computors, Photographic and Video Equipment, three professional letters of reference tions. Assistance with relocation. also Manufacturers Plant and General Works Effect. should be sent to Faculty Affairs Further particulars and an application Catalogues Available, Subscription £10 per year, Post Paid. Division, Yarmouk University, Irbid, form are available from the Personnel Offi- ANGLIA INDUSTRIAL AUCTIONS Jordan. cer, The Queen's University of Belfast, Nor- (2574) 1 NN. 5 Station Road, Littleport, Cambs. CB6 1 QE. Phone. 0353 860185. thern Ireland, BT7 (2573) (2578)

ELECTRONICS & WIRELESS WORLD JUNE 1985 99

www.americanradiohistory.com MEDICAL RESEARCH COUNCIL INSTITUTE OF HEARING RESEARCH SOUTHAMPTON CLINICAL OUTSTATION LINK RESEARCH OFFICER IN ELECTRONICS ELECTRONIC (RO /SRO) A vacancy exists for a research officer with ENGINEERS experience in electronics at IHR Southampton. The post will be based at the Institute of Sound and Vibration We are in the forefront of providing state -of- the -art Research at the University, but will also relate to the other broadcast tv equipment to the BBC and independent half of the team's activities, at the Royal South Hants companies in this country and similar organisations Hospital. throughout the world. Our new type 130 micro- The research is on clinically applicable aspects of processor based colour camera is in production in hearing and deafness, advanced testing techniques, and the addition to which we have a world -wide market for use of signal averaging equipment by computer for which a very high outside broadcast and studio installations. level of technical support is required. The appointee will be required, with minimal supervision to design and construct new equipment involving To help us broaden our product range and continue our transducers and interfaces. There will also be a little success we urgently need to recruit well qualified general technical support for the research team including electronic engineers (some at senior level) who are calibration, repair and servicing work. A general looking for the opportunity to develop their talents in a electronics background is needed and a knowledge of Z80 close knit team. Current requirements include: CP /M systems and of digital interface techniques would be advantageous. For further information about the post please contact Dr. A.R.D. Thornton (Tel: 0703 37946). DESIGN AND DEVELOPMENT - The appointment will be made on the Research Officer grade (£6483 -8492) or Senior Research Officer HARDWARE/SOFTWARE grade (£8574 -10,938). The MRC has a pension scheme and generous leave allowances. ENGINEERS (2566) SALES ENGINEERS CALIBRATION/ TEST ENGINEERS SERVICE ENGINEERS c £8,250 + Overtime + July Review Salaries offered will reflect the high standard of engineer Bradley Electronics is one of the leading organisations in we are looking for and are accompanied by 25 days the electronics industry. We provide a range of advanced holiday per year, free health and life assurance. A electronic equipment and engineering services to MoD, pension scheme and, where appropriate, generous Industry and the Health Care market. assistance in relocating to this pleasant part of Our Repair and Calibration laboratory, the largest of its type in the UK, provides a comprehensive service for Hampshire. commercial and military organisations, with its full facilities for maintaining and calibrating all types of electronic equipment. Opportunities exist for Engineers to work with a wide Please phone Jean Smith on Andover (0264) 61345 for an variety of equipment, including Multimeters, Oscilloscopes, application form or further details of the vacancies. Navigation Systems and Electronic Counter Measure Alternatively you might like to let us have a full cv with Systems. Ability to trace, diagnose and rectify faults in these details of your background and experience. complex equipments is essential. Education to a minimum (2597) of C&G /TEC or equivalent is required, together with considerable practical knowledge and experience in electronic testing, servicing of radar, and telecommunications equipment. Experience of this nature gained in the Services will be of particular value. The Company is located close to the underground, bus routes and the North Circular Road /M1. The salary and conditions package available is consistent with the LINK Company's membership ofa large, successful Group with considerable resources. ELECTRONICS For full details please call our Personnel Manager, Roger Loughney, on 01 -450 7811. Or write to him at Walworth Industrial Estate, Andover Hampshire, England Bradley Electronics Limited, Electra) House, Telephone: Andover (0264) 61345 Neasden Lane, London NWIO IRR. Bradley Electronics (2560)

100 ELECTRONICS & WIRELESS WORLD JUNE 1985

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BORED ? Telecommunications Then change your job! Engineering 1) TEST CALIBRATION ENGINEERS To work on a variety of micro based instruments and A.T.E. Windsor Technicians £12,000+ 2) REMOTE CAMERA EQUIPMENT Test engineers to work on high speed digital systems to £10,000. Surrey. Openings in Servicing and Maintenance 3) TECHNICIAN ENGINEER For maintenance of VAX pdpll and flight Up to £8,873 simulation systems. Middx. To £11,000. is to 4) DATA PROCESSING EQUIPMENT Our business install and Customer service engineer to work on maintain the communications - PDP8 and PDP11's, printers and equipment used by the Police graphics displays. £12,000 + car. Berks /Bucks. and Fire Brigades in England 5) MARINE SERVICE ENGINEER To and Wales - some of the latest maintain a variety of marine communications and navigation you will find in operation systems. Surrey. To £10,000. anywhere. travelling 6) DEVELOPMENT/TEST ENGINEER We have a number of vacan- will norm- To design and support a variety of medical systems. £10,000. Berks/ cies at our Service Centres in various ally be in- Middx. parts of the country, for Telecommuni- volved. Reg- Hundreds of other Electronic cations Engineering Technicians with istered disabled and Computer vacancies to £12,500 practical skills in locating and diagnos- persons can of Phone or writs: M.I.E.E., N I.E.R.E. ing faults in a wide range of equipment course apply. Roger Howard, C.Eng., CLIVEDEN CONSULTANTS frorg computer-based data transmission The Home Office is an equal 92 The Broadway, Bracknell, Berkshire to FM and AM radio systems. opportunities employer. Tel: 0314 089489 (1640) The work provides excellent Salary will be on a scale £6501 opportunities for extending your techni- to £8873 a year with generous leave CLIVEDEN cal expertise, with specialised courses allowance and pension scheme. and training to keep you up to date on Good prospects for promotion. DESIGN AND developments and new equipment. If you are interested in working There are also opportunities for day with us, please write for further DEVELOPMENT release to gain higher qualifications. details and an application form, ENGINEER Applicants, male or female, quoting reference WW /3 to: Experienced engineer required to join small electronics company involved in must be qualified to at least City & Miss M Andrews, Home Office, design and manufacture of telecomms Guilds Intermediate Telecommuni- Directorate of Telecommunica- products for BT and other PeT authorities. cations standard and possess a tions, House, Dean Horseferry Applicants should have experience In line current driving licence. Some Ryle Street, London SW1 P 2AW. equalisation equipment, filters, SMPS (2557) and automatic testing using microprocessor techniques. . ok Directorate of Qualifications to degree or HNC with suitable experience. Attractive salary + Home Office ; Telecommunications usual benefits to right person. Application to include current c.v. to: Kenton Research Ltd. Europe Trading Estate, Erith, Kent DAB SQL. Telephone: (032 24) 419 33 (2519)

pleasant, the surroundings are attractive, and the career COMMUNICATIONS prospects are excellent. Ideally were looking for men and women who DESIGN have studied electronics or electronics related subjects to degree level or equivalent and have had some experience FROM START ... of design, whether obtained at work or through hobby activities. Appointments will be made as Higher Scientific ( )Hìcer (£7,435 -£10,039) or Scientific Officer (£5,909 - £8, I53) according to qualifications and experience. For further details please write to the address given At H.M. Government Communications Centre below. It would be particularly helpful Wan outline of we're using the vela latest ideas in electronics technology' your personal interests and practical experience could to design and develop sophisticated communications be included. systems and installations for special Government needs The Recruitment Officer, H MGCC, Hanslope Park, at home and overseas. Bucking-hams!' in' Mf:I)7BI I. With full technical support fàcilities on hand, it's an environment where you can see your ideas progress from initial concepts through prototype construction, test and evaluation, to the pre -production phase, with a ... TO FINISH chance to influence every stage. Working conditions are (2523)

ELECTRONICS & WIRELESS WORLD JUNE 1985 jOI

www.americanradiohistory.com SMALL SELECTION ONLY LISTED RING US FOR YOUR REQUIREMENTS WHICH MAY BE IN STOCK ARTICLES FOR SALE SERVICES

MORSE READING PROGS. Work on FREE P.T.H. PROTOTYPE of the finest quality clean signals without hardware interface. with EVERY P.C.B. artwork designed by us. Com- ZX81 1K UNEXPANDED MEMORY. petitive hourly rates, and high standard of work. Translated code with word and line spaces Halstead Designs Limited, 34, High St., Halstead, for easy reading Automatic scroll action. Essex. Tel. (0787) 477408/474554. (2126) £7 incl. (2532) WAVEGUIDE, Flanges and dishes. All standard SHEETMETAL FOLDERS vice or bench sizes and alloys (new material only) from stock. model. 24' X 16G £45. Leaflet 01 -890 Special Portable Battery or Mains Oscilloscope. SE Laborato- sizes to order. Earth Stations, 01 -228 7838 anytime (2558) 7876, 22 Howie Street, London ries 111 Oscilloscope - Solid State - General pur- SW 114AR. (2099) WIIliemeP.C.B.Artwork, 49IWeetbourne, pose - Bandwidth DC to 18/2OMC /S at 20MV /CM - QUARTZ Evewhem, Woreerew Dual Channel CRYSTALS OSCILLATORS AND - APPOINTMENTS FILTERS of all types. Large stocks of standard Rise time IONS - Calibrated Sweep - Calibrator - Display 10CMSxBCMS Power AC -95 Volts to 100- items. Specials supplied to order. Personal and - export orders welcomed SAE 190 Volts to 260 or 24 Volt DC battery - Size. Do you regard yourself as an electronics - for lists please. SMALL BATCH PCBs, produced from W.25.5.CM H25.5CCMS 56CMS Deep OEM support thru:- design advice, prototype - - - whizz kid. Then I would like to hear your artwork, also DIALS, PANELS, LAB- WT11.4KGS- Carrying handle - Tested in faircondi- from quantities, production schedules. tion with operating instructions £120.00. you. Formal qualifications may not be Golledge Electronics. Merriott, Somerset TA16 ELS. Camera work undertaken. FAST necessary; Age not important. Interested? 5NS. Tel: 0460 73718 (2472) TURNAROUND. Details: Winston Promo- Then telephone 01 941 2225 and ask for Mr tions, 9 Hatton Place, London EC1N 8RU. Tel. 01 -405 4127/0960. (9794) Lawrence. 2596 DESIGN AND DEVELOPMENT SER- BUSINESS OPPORTUNITY VICE. RF transmitters and receivers. T.I. DATA BOOKS Telemetery U.H.F. V.H.F. Anologue and digital circuits, control systems. Full Opto Electronics £5.00 manufacturing facilities. RCS Electronics. Due to very strong demand, ILP Wolsey Road, Ashford, Middx. Phone Electronics Limited Linear Circuits £9.00 Dr. - UK Eric Falkner on 53661. (2637) manufacturer of audio modules and TTL (7th Ed.) Vol.1. £9.00 related products - urgently seek TTL (7th Ed.) Vol.2. £8.00 DESIGN AND MANUFACTURE. ANA- Yugoslavian based representative/ 'Understanding' LOGUE, DIGITAL, RF AND MICRO- Latest Bulk Government Release - Cossor Oscillo- distributor to market their range. series £4.50 WAVE CIRCUIT AND SYSTEM DESIGN. scope COU150 (CT531/3) £150 only. Solid state general Reply Also PCB design, mechanical design and to to: Post free CWO. SAE for lull list purpose bandwidth DC 35MHz at 5MV /CM - Dual prototype /small batch production. Channel - High brightness display (8x10cm) Full ILP - delayed time base with gated mode - Risetime IONS Electronics Limited MG Books, 24A Newgate, Adenmore Limited, 27 Longshot Estate, - Illuminated graticule - Beam tinder - Calibrator Graham Bell House, Roper Bracknell, Berks. Tel: Bracknell (0344) 1KHz squarewave Power 100 120V.200V 250 Barnard Castle, Co. - - - Close, Canterbury, 52023. (656) volts AC - Size W 26CM - 41 CM deep - WT 12.5 K.G. Durham DL12 carrying handle - colour blue - protection cover front Kent. Telephone: 0227- 8NG. containing polarized viewer and camera adaptor plate Tel: (0833) 31130 The Publishers take all - probe Ill - Mains lead. Tested in Fair condition with 454778 ( 2540 ) reasonable care to ensure operating instructions - £150.00. (2591) that classified advertisements are Communication Recievers. Racal 500KC/S to 30MC/S genuine, but readers must satisfy ill 30 bands 1MC /SWIDE - RA17 MK11 £125. RA17L C150. RA117E £200. New Metal Louvred Cases for themselves that they will be above £25. All receivers are air tested and calibrated in obtaining what they require our workshop - supplied with dust cover - operation instructions - circuit - in fair used condition. Racal before entering into transactions, Synthesisers (Decade frequency generators) MA350B EAST STREET, FARNHAM, SURREY. particularly if they involve large Solid Stale for use with - MA79 - RA217 - RA1218 Etc £100 lo £150. MA250 - 1.6MC /S to 31.6 MC /S sums of money. 2519) £100. MA1350 for use with RA17 receiver 2100. TEL: 0252 722666 MA259G Precision frequency standard 5MC /S - 1MC/S - 100KHz £100 to £150. Panoramic Adaptor CONTACT: G.P. SKINNER DOLCH LOGIC ANALYZER LAM3250, RA66 £150. RA137 and RA37 t40 to £75 LF convertors 50MHz, 48 channel; 32 data, 2 external io to 980KC/S. RA218 Independent SSB unit £50 RA98 A SELECTION OF TELEVISION AND clocks, 6 clock qualifiers and 8 trigger qual- SSB-ISM Covertor £50. RA121 558 -ISB convertor £75. ifiers. TTL & ECL thresholds. 5ns Glitch EC964/7K Solid state - single channel - SBB - ELECTRONIC COMPONENTS FOR DISPOSAL mains or battery - 1.6 to 27.5 MC /S and 400 to 535KHz capture. Including 6ALP88 active logic £100 with manual Plessey PR155G Solid Slate 60KC /S 68 PF Ceramic Cap TEC 1 500 Earth Strip UHG Tuner pods. £2,500 Tel: Bordon (04203) 30MC /S £400. Creed 75 Teleprinters Fitted tape - - 470 PF Pulse Ceramic 12K PHIL G8 Focus Control 7194. (2582) punch and gearbox for 50 and 75 bauds - 110volts AC supply - in original transport tray sealed in polythene PYE 731/728 - Mains Switch PHIL G8 UHG Tuner QUANTUM & SHUGART 8 inch winch - Ilk new C15EA. Redifon TT11 Audio Teleprinter con- TEC 8000 /8500 Therm Cut Out VRRistur E299/DC/p348 drives & 8 inch floppy drives, 10.66 meg & vertor receiver solid slate - supply 110 or 240AC - - - Made for use with above teleprinter enabling print -out GEC - 1040 /Therm Cut Out TEC 1400 Mains Dropper 400K. QZO10, 801 available new. Full of messages recieved from audio input of communica- IN4002 PHIL 210 Frame Out Put Transformer manual. Phone Steve 0462 711815. tion receiver £15 with circuit tested. Redifon TT1O Con- (2594) vertor as above but includes transmit facilities £20. BC308B PHIL G8 AFC Assembly Oscilloscopes - stocks always changing Tektronix BD137 PHIL G8 - Vision Selectivity Assembly 485 100MC /S £750. FM Recorder Sanghmd Sabre - BC307 PHIL G8 Vsion Gain Assembly 111 14 channels £350. Transtel Matrix printers - - HALF PRICE ENCLOSURES AF11R- 5level Baudot Code - up to 300 Bauds -lot BAX 13 PHIL G8 - Sound Selectivity Assembly Manufacturers Brand New Surplus and print out on plain teleprinter paper £50 to £100. Trans - TAA661 PCF80 Seconds at almost Half Price. 19' Rack IelAH11R- As above but also 8 level ASCII (CCITT No Mounting and smaller Free Standing 2 and CCITT No. 5) Like new £100. Army field tele- PHIL 210 - Brightness Knob PL36 phone sets. Type F -L and J - Large quantity in stock Enclosures. No damage and only PHIL 210 Volume Knob EF 1 84 £6 to £15 depending on type and quantity P.O.R. Don - blemishes on the finish at the very worst. 10 Telephone Cable half mile canvas containers TEC 1500 Brill /on -off Knob - - Send S.A.E. for List. C. Phillips 'The £20. Night viewing Infra -red AFV periscopes - Twin Eyepiece - 24 volt dc supply £100ea. Original cost to CATHODE RAY TUBES COLOUR Laurels' Tiptoe Road, Wooton, New government over £11,000ea. Static inverters - 12 or A51 - 110X /A51 - 220X A67 - 120X A56 - 120X Milton, Hants BH25 5SJ. Mail Order Only. 24 volt input - 240 volt AC si newave output - various (2592) wattages P.O.R. KY Ploters and pen recorders various - P.O.R. Ferrograph sedes 7 Tape recorders mono ALL AT KNOCK DOWN PRICES £100, stereo £150. Signal Generators various - FOR A DETAILED LIST PLEASE APPLY TO TF995/A3 £60. TF801 D/& - 10MC /S to 485MC /S £90 - TF144H/A4 £90. TF1080/2 £60. HP606A - £90 £140 Apollo Sciibemaster X -Y, micrometer HP608 C50 HP614A £100 HP6180 C100 HP620A £100. 0252- 722666 calibrated, table £89. Metals Research Marconi TF1064B/5 £100 11791 Deviation meter £100 (2533) Macrotome, diamond cutters, accessories TF893A Power meter £50 Aerial mast assembly 30ft etc., £275. Stanton Electronic Balance high complete with 16ft whip aerial to mount on top - single pan £150. Advance Twin Stabilised guyropes - insulators - Base and Spikes etc., in heavy Power Supplies £59. Wayne -Kerr Universal duty carrying bag - new £30. Racal frequency counter TO MANUFACTURERS, WHOLESALERS Bridge £98. Ignition Analyser Unit/ Type 836 £50 Tektronix plugs -Ina -1 Al £50, 1 A2 £40, Diagnostic manual £39. Low -voltage 1A4 £100 M£50. All items are bought direct from H.M. BULK BUYERS. ETC. Electroplater for rust prevention/ Government being surplus equipment: Price is Ex rectification £39. Microscope with works. S.A.E. for enquiries. Phone for appointment micrometer table £89. Miscellaneous for demonstration of any items. Also availability or LARGE QUANTITIES OF RADIO. TV AND stabilised power supplies £18 -£45. Avo In- price change. V.A.T. and carriage extra. Circuit transistor, diode, thyristor tester ELECTRONIC FOR £25. Philips RM /AM /Sweep generator £89. COMPONENTS DISPOSAL Creed Teleprinter £75. High Intensity Fibre - EXPORT TRADE AND QUANTITY SEMICONDUCTORS, all types, INTEGRATED CIRCUITS, TRANSISTORS, Optic Light Supply, twin lamps, twin DISCOUNTS GIVEN DIODES, RECTIFIERS, THYRISTORS, etc. RESISTORS, C /F, M /F, W /W, etc. outputs each £35. Hughes Micro -Spot JOHNS RADIO (0274) 684007 Welding Head £69, ditto -Sippicam £35. WHITEHALL WORKS, CAPACITORS, SILVER MICA, POLYSTYRENE, C280, C296, DISC Chart Recorders. Audio Generator Audio 84 WHITEHALL ROAD, CERAMICS, PLATE CERAMICS, etc. Analyser. Wow /Flutter Meter. Digital Calibration Voltmeter, five digits, DC /AC EAST BIRKENSHAW, BRADFORD ELECTROLYTIC CONDENSERS, SPEAKERS, CONNECTING WIRE, CABLES, plug -ins £85. Infra -Red Analyser Heads BD11 2ER SCREENED WIRE, SCREWS, NUTS, CHOKES, TRANSFORMERS, etc. £30. Four -Phase Signal Generator £85. Sweep Generators., etc. ALL AT KNOCKOUT PRICES Come and pay us a visit ALADDIN'S CAVE Pulse generators. - etc. WANTED: REDUNDANT TEST EQUIPMENT - RECEIVING AND TRANSMITTING EQUIPMENT - TELEPHONE: 445 0749/445 2713 (20161 VALVES - PLUGS - SOCKETS SYNCHROS R. HENSON LTD. ETC. (2734) 21 Lodge Lane, North Finchley, London, N.12 (1613) 040 376236 (5 minutes from Tally Ho Corner)

102 ELECTRONICS & WIRELESS WORLD JUNE 1985

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WANTED WANTED E C COMPONENTS All types of surplus electronic WANTED We buy large and small parcels SURPLUS ELECTRONIC components and equipment. AND Test equipment, receivers, I /C, COMPONENTS We specialise in factory clearance. of surplus transistors, capa- citors and related electronic EQUIPMENT valves, transmitters, com- SGS Electronics, stock. Immediate settlement. We also welcome the opportunity to quote for ponents, cable and The Vineyard, Bowley Lane, complete factory clearance Tel: 01 -208 0766 electronic scrap and quan- Boddenham, Herefordshire B. BAMBER ELECTRONICS Telex: 8814998 5 STATION ROAD, LITTLEPORT, CAMBS. tity. Prompt service and HR1 3LF. Tel (056) 884 532 (2491) Phone: Ely (0353) 860185 cash. Member of A.R.R.A. (2541) 12483) M & B RADIO TURN YOUR SURPLUS i.cs transistors 86 Bishopsgate Street SURPLUS When replying to classified etc. into cash, immediate settlement. We also welcome the opportunity to quote for Leeds LS1 4BB We offer good prices for test equipment, advertisements, readersare 0532 435649 redundant computers, complete factory clearance. Contact components, South PCB's connectors. Immediate settle- recommended to take steps COLES-HARDING & CO, 103 19956) ment. Brink, Wisbech, Cambs. 0945 TIMEBASE to protect their interests 584188. (9509 1 94 Alfriston Gardens before sending money Sholling, Southampton SO2 BFU OF READING Telephone: 107031431323 (2519) STEWART * MICROCOMPUTERS 11832) 110 WYKEHAM ROAD READING RG6 1PL * PERIPHERALS * INSTRUMENTATION ARTICLES FOR SALE CAPACITY AVAILABLE TEL NO: 0734 68041 For fastest, best CASH offer, phone, TOP PRICES PAID FOR FOR THE BEST PCB SERVICE ALL TYPES OF SURPLUS COMPUTER APPRECIATION FM BROADCAST EQUIPMENT AVAILABLE TEST EQUIPMENT, Oxford (0865) 55163 A special range of high quality COMPUTER EQUIPMENT, Telex 838750 *Circuit Deign & Development COMPONENTS etc. transmitters, power amplifiers, Digital and Analogue (2492) UHF repeater ANY QUANTITY. (26161 stereo encoders, *Artwork Layout links, compressors, antennas PCB artwork layout and mechanical detailing. P.O. etc. approved standard. at an *Board Manufacture CIRCOLEC Built to high specifications Prototype to semi- production, excellent rates. economic price. VHF /UHF data THE COMPLETE ELECTRONIC SERVICE *Wiring & Assembly and telemetry systems (MPT PCB assembly, wiring and cable forming. Flow solder- Artwork, Circuit Design, PCB Assembly, Test & Repair Service, Q.A. 1309) available ex- stock. ing facilities available. Consultancy, Prototypes, Final Assembly. Full PCB Flow Soldering Service. Full catalogue available. *Test Full test facilities available. Quality workmanship by professionals at economic prices. Cyberscan International, 3 Eastcote One or all services available. Please telephone 01 -646 5686 for advice or further details. View, Pinner, Middx HA5 1AT. Please telephone Chelmsford 102451 357935, or write to HCR TAMWORTH MANOR 01 -866 3300 Electronics, The Industrial Unit, 302 -310 COMMONSIDE EAST, MITCHAM (2542) Parker Road, Chelmsford. (30mins from Liverpool Street St.) (1169) 113911

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www.americanradiohistory.com f11E1w II STRVlEf1TS FROM STOCK 1 A BETTER CHOICE IIII 'SCOPES POWER SUPPLIES COUNTERS HITACHIHAMEG THURLBY PLUS LOW COST RANGE THANDAA BLACK STAR muwIhilli0161Min e eaIÌI '_® = =r CROTECH SCOPEX RANGE OF 'Mann EQUIPMENT INCLUDES y_ _ -- GENERATORS TV TESTING: DIGITAL ANO ANALOGUE MULTIMETERS: -- ì`ae; SCOPES: CLAMPMETERS: INSULATION TESTERS: I!InIIIIIIIIIIIII vp BLACK STAR THANOAR 9: iÌe V y WOW /FLUTTER LEADERTRIOSALDETA METERS: DISTORTION METERS: FUNCTION. PULSE ANO R -C GENERATORS: LCR BRIDGE: DIGITAL CAPACITANCE: MULTIPLEXERS: LOGIC ANALYSER: LOGIC MULTIMETERS PROBES: COUNTERS: POWER SUPPLIES: TRANSISTOR METEX SOAR METRIX CHECKERS, ETC. 11111161111111H1IIIIIIIIIIIIIIIIIIIIII THURLBY THANDAR PLUS COMPONENTS: TOOLS: COMPUTER SOFTWARE PLUS LOW I11111111111111111111111111111111111111111111111 COST RANGE AND ACCESSORIES: SEMICONDUCTORS: EXPORT SUPPLIED - OFFICIAL ORDERS (SUBJECT TO APPROVAL) WELCOMED EDUCATIONAL DISCOUNTS AVAILABLE 301 Edgware Road, London W2 01 -724 3564 dlII / /AI 404 Edgware Road, London W2 01 -724 0323 IIII I LETUSOUOTEFOR EE1.ROf11CS Illyy¡¡ ACCOUNT AND EXPORT ENQUIRIES 01- 2581831 YOUR REQUIREMENTS ES I )IIIIIIIIII1II111111IIIIIIII CIRCLE 35 FOR FURTHER DETAILS.

ADVERTISERS Appointments Vacant Advertisements appear on pages 95 - 103 PAGE PAGE PAGE AH Supplies 93 Electrovalue 28 Newrad Instrument Cases 83 AM Electronics 74 Electronics & Wireless World 78 North East Satelitte Systems 15 AWR Technology 74 Electronics & Wireless World Binders 93 Number One Systems 16 Advertising Standards Authority 14 Ellmax Electronics 66 Air Link Trans 16 Ervine Business Systems 9 P.F. Ralfe 4 Antex (Electrical) Outside back cover European Electronic Systemslnside back cover PM Components 32/33 Arcom 93 Pantechnic 25 Armon Products Ltd 65 Field Electric 4 Pye Unicam 67 Aspen Electronics 2 Audio Electronics 104 Gemini Microcomputer 38 R. Henson Ltd 65 Automation & Control Technolog 28 Greenwood Electronics 48 Radford 2 Radio Code Clocks 68 B Bamber Electronics 14 Happy Memorie 85 Research Communications 13 Beckenham Peripherals 15 Harris Electronics 65 Black Star Ltd 48 Harrison Bros. 22,74 Samsons Electronics 13 Bytron Ltd 48 Hart Electronic 89 Sarel Electric Ltd 74 Henry's Audio Electronics 25 Satellite Technology 4 Cambridge Microprocessor 16 Hilomast Ltd 56 Sherwood Data Systems 22 Cavendish Automation 66 Stewart of Reading 85 Colomar Electronics 56 ILP Electronics 65 Surrey Electronics 48 Computer Appreciation 2 Integrex 3 Conquin Software Inside front cover TIC Semicond 89 Crash Barrier 2 J. Bull 16 TK Electronics Cricklewood Electronics 68 JDR Metal 22 12 Tape Automation Crotech Instruments 89 JPR 93 85 Taylor Bros Cybernetics Application 15 83 Technomatic L.J. Electronics 5 26/27 Tektronix Ltd 37 Dataman Design 55 Lanco Ltd 15 Thandar Electronics Digitask 89 Langrex Supplies 47 28 Thanet Electronics Digitask Business System 12 Levell Electronics 3 25 Thurlby Display Electronics 10/11 Electronics 88 Maplin Electronic Supplies 22 Triangle Digital Services 83 E.A. Sowter 5 Measurement Devices 68 EG & G Reticon 9 Micro Processing Engineering 4 Warwick Design 12 EMS Mfg 56 Midwich Computer Co 66 Weyrad Instruments 21

OVERSEAS ADVERTISEMENT AGENTS Japan: Mr Inatsuki, Trade Media - IBPA (Japan), B.212. Azabu Jack Mantel, The Farley Co., Suite 650, Ranna Building, France and Belgium: Heights, Pierre Mussard, 18 - 20 Place de la 1.5.10 Roppongi, Minato -ku 106. Cleveland, Ohio 4415 - Telephone (216) 621 1919. Madelaine, Paris 75008. Telephone: (03) 585 0581. Ray Rickles, Ray Rickles & Co., P.O. Box 2028, Miami Beach, Florida 33140 Telephone (305) 532 7301. Hungary: Ms Edit, Bajusz, Hungexpo - Advertising Agency, United States of America: Jay Feinnan, Business Press Tim Parks, Ray Rickles & Co., 3116 Maple Drive N.E., Atlanta, Budapest XIV, Varosliget. International Ltd, 205 East 42nd Street, New York, NY 10017 Georgia 30305. Telephone (404) 237 7432. Telephone: 225 008 Telex: - - Budapest 22 -4525 Telephone (212) 867 -2080 Telex: 23827. Mike Loughlin Business Press International, 15055, memorial INTFOIRE - Jack Farley Jnr., The Farley Coi. Suite 1584, 35 East Walker Ste 119, Houston, Texas - Telephone (713) 783 8673. Drive, Chicago, Illonois 60601 - Telephone (312) 63074. Canada: Colin H. MacCulloch, International Advertising Italy: Sig C. Epis, Etas -Kompass, S.p.a. Servizio Estero, Via Victor A. Jauch, Elmatex - International, P.O. Box 34607, Los Consultants Ltd., 915 Carlton Tower, 2 Carlton Mantegna 6, 20154 Milan. Street, Toronto 2 Angeles, Calif. 90034, LISA - Telephone (213) 821 -8581 Telephone (416) 364 2269. Telephone: 347051 - - - Telex: 37342 Kompass. Telex: 18-1059. Also subscription agents.

Printed in Great by Britain Index Printers Ltd., Oldhill, Dunstable, and typeset by Legendary Characters, South Street, Lancing, for the proprietors, Business Press International. Quadrant House, The Quadrant. Sutton. Surrey SM2 SAS. O Business Press International 1984. Wireless World can be obtained abroad from the following: AUSTRALIA and NEW ZEALAND: Gordon & Gntch Ltd. INDIA: A. H. Wheeler & Co. CANADA: The Wm. Dawson Subscription Service Ltd., Gordon & Gotch Ltd. SOUTH AFRICA: Central News Agency Ltd: Willian Dawson & Sons (S.A.) Ltd. UNITED STATES: Eastern News Distribution Inc., 14th Floor, 111 Eighth Avenue, New York. N.Y. 10011.

104 ELECTRONICS & WIRELESS WORLD JUNE 1985

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