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Using trees as tv aerials

Digital stereo television sound

www.americanradiohistory.com f&J Programming Systems from Stock

EP8000 and EP4000 EPROM P8000 Production Accessories for the EP8000 EmulatorlProgrammers EPROM Programmer and EP4000 range

Software personality programming of NMOS, HMOS, CMOS EPROMs, E Programs NMOS, HMOS, CMOS NEW both single Et triple rail up to 16k x 8 EPROMs up to 16k x 8 bytes, both bytes IEP80001. single Er triple rail. BP5 Bipolar PROM Programming PROMs Expandable to program with No personality cards or characterisers Module. BP5 Signetics PROM adaptor. required. Allows the EP8000 and EP4000 to pro- E Emulation of all EPROMs up to 8k x 8 gram, copy, verify a range of 21 bytes with the EP8000 and up to 4k x 8 Up to 8 EPROMs programmed Signetics bipolar PROMS up to 2k x 8 bytes with the EP4000. simultaneously. bytes sizes Ex -stock - £228 + VAT. cards or characterisers SA27128 Adaptor. Allows EP8000 to No personality _l Simple menu driven operation. required. program 27128 EPROM Ex -stock - Use as stand alone programmer, slave Reverse and misplaced insertion £69 + VAT. programmer, or EPROM development checks. Constant power supply UV141 EPROM Eraser. Erases up to 14 system. monitoring and system checks. devices simultaneously - safety in- E Checks for misplaced, reversed inser- terlocked - electronic timer. Ex -stock illegal test, blank tion and shorts on data lines (EP80001. Checksum, bit - £78 + VAT. check, compare and self check cycles. Memory mapped video 0/P, in addi- Prinz Video Monitor. Green phosphor, high resolution video monitor suitable tion to LED display allows full use of E RS232 serial interface as standard. powerful editing facilities, including for EP8000 and EP4000 Ex -stock - block/Byte move, insert, delete, Single key programming operation. £99 + VAT. match, highlight, shift, define, Contact us now for a complete pro- displacement calculation. Ex -stock P8000 - £695 + £12 del + duct data pack. VAT. Comprehensive I/O - RS232 serial port, parallel port. Ex -stock EP8000 - 8k x 8 RAM £695 + £12 del + VAT EP4000 - 4k x 8 RAM £545 + £12 del + VAT.

GP Industrial Electronics Ltd TTeellex::Ply42513mouth (0752) 332961 Unit E, Huxley Close, Newnham Ind. Estate, Plymouth PL7 4JN

CIRCLE 001 FOR FURTHER INFORMATION

www.americanradiohistory.com 41/2 DIGIT AUTORANGING MULTIMETER -THE DM141

109V, 4'/z digits, 28500 counts True r.ms. up to 20kHz Autoranging or manual range selection Big, bright, high efficiency LED display +30 to -60dBm function Up to 2.5kV spike protection Diode test facility B.C.D. version available. IEEE488 compatible with Omnibus 081 option British design and manufacture by Farnell

DETAILS FROM This 4'fi digit autoranging digital muhimeter measures Resolution on volts is 10jV and on current 10A. a.c. and d.c. volts and current, resistance and dBm. Resistance measurements down to 10m11 are

A.C. measurements and dBm are true r.m.s. with a possible. The dynamic range of the decibel function is frequency response of 45Hz to 20kHz. +30 to -60. Overload protection is excellent and includes spike protection to 2.5kV. Basic d.c. accuracy For automatic ranging select the required function, U Farrell connect and read. The DM141 will automatically select is 0.03%. the best range and position the decimal point. The displays are seven segment 0.43" red LEDs of the FARNELL INSTRUMENTS LIMITED Manual range changes can be achieved using the UP high efficiency type with range and decimal point being An is SANDBECK WAY WETHERBY or DOWN range push buttons and the HOLD facility is automatically annunciated. autozero facility sometimes useful to stop automatic range changes provided and autopolarity means no lead switching and WEST YORKSHIRE LS22 4DH around the 19999 count. The manual facility may be positive or negative reading clearly indicated. The TELEPHONE (0937)61961 rate is 3 readings per second. An overrange used to increase resolution as the DM141 provides up sampling TELEX 557294 FARIST G to 28500 counts on overrange. condition is indicated by all displays flashing.

CIRCLE 5 FOR FURTHER DETAILS.

SOLVE RADIOCODE CLOCKS PROBLEMS ATOMIC TIME, FREQUENCY AND SYNCHRONISATION EQUIPMENT ¡NEW PHASE -MODULATION SYSTEMS Until recently, atomic time and date information was only available on v.l.f. transmissions using amplitude modulation. The RCC 8000AM series of equipment uses these transmissions to offer high noise immunity and high accuracy, particularly at very long range. The new RCC 8000PM series of equipment uses, for the first time, phase modulated tranrnissions with massive radiated powers of up to 2 Mega - Watts to offer long range, excellent noise immunity and no scheduled `..maintenance periods.

NEW PRODUCTS The AM and PM series of Radiocode Clock equipment has been further expanded to include seven new models (from top) 8000S - combined clock, frequency standard and optional stopclock. Internal standby power supply - with dual rate constant current charger. Time -event log - prints hours, minutes, seconds, milliseconds and day of year, on receipt of a log pulse. Speaking clock - time announcement or audio recording. Slave controller - total control of single -standard master/slave systems ie one pulse/sec. Dual standard slave controller - total control of two different and independent slave systems, ie. one pulse/sec and one pulse/half min. Slave distribution amplifier - maximum flexibility for the largest master/slave installations requiring dual standard operation, multiple cir- cuits and complete master/slave backup.

NEW OPTIONS A continuously expanding range of fully integrated software and hardware is available for both series of Radiocode Clock equipment. Standard op- tions now include: IRIG B precision serial o/p Time code generators RS232/V24 1 mS resolution Intelligent slave systems General purpose parallel o/p Standard frequency outputs FSK record/replay system Stopclock ... .,.,,,,.,..,,o, 4PAOLO-1111 operation . . .._ , ^-_ . _ Keypad for _. -, -, entry of alarm times Calibrated systems A. f-. Keypad entry of time/date increased accuracy .. 4:4---s,b^.«.Mirtti'trlti f Radiocode Clocks Ltd* ® ego* . Unit 19, Parkengue, Kernick Road Industrial Estate Penryn, Falmouth, Cornwall. Tel: Falmouth (0326i 76007 (*A Circuit Services Associate Co.) 4.CIRCLE 45 FOR FURTHER DETAILS. ELECTRONICS & WIRELESS WORLD JULY 1984 1

www.americanradiohistory.com Wirelésswórld over 70 years in it çlependent electronics publishing

July 1984 Volume 90 number 1582 SEP - 9 1984 FEATURES 17 25 45 Digital stereophony Television reception Multi -standard modem with television with papaya tree by Richard Lambley by E.H. Hartwell antenna Third and final article details the line interface Tests on digital four -phase by S.P. Kosta et al. d.p.s.k. technique of plus software suggestions transmitting additional Novel technique couples r.f. and some telephone energy from vegetation numbers to try sound information for tv canopy to receive tv stereophoney show the signals. system to be more rugged than for either teletext or colour television pictures. 31 55 Fibre SC84 microcomputer optics 22 communications `d.-°:;;,.ün;..: `ow...- .... With its own memory and Music keys for the BBC controller, SC84's v.d.u. by Brett Wilson microcomputer module allows 3000 text This last article looks at the characters, 36 000 picture range of applications in by R.M. Adelson elements, or a mixture of which fibre optic systems Economical polyphonic are being introduced interface drives the both computer's own sound generator an 37 or external 61 unit Improving colour 27 television decoding Micro -controlled by D.C.A. Read cassette recorder-3 Variable -speed video Last of David Read's series by A.J. Ewins by J. R. Watkinson includes Description of f.s.k. John Watkinson continues surface -wave -filter and modulator and his description of the other component details, demodulator for the effects of variable and discusses additional solenoid -operated machine tape/head speed on the picture enhancement for use with video waveform techniques microcomputers REGULARS 7 49 74 Communications Circuit Ideas Letters commentary RS422-to-232 converter, Preferred values A use for BandIII tv isolated video driver, GPIB combiner comments transmitters, diplomatic remote volume control, Is light velocity a constant? radio, telecommunications opto -isolator circuits XY plotter act, moonbounced tv? Technocratic bondage? Relativity 12 67 News Literature received 81 Uosat I1 relocated, joint tv Data collected from a and telephone cable, recent computers in the New products cellular radio start, classroom exhibition Teletext w.p., optical computerized dictionary modem, eprom emulator, satellite weather -map This issue has been affected by the continuing dispute receiver, network between members of the National Union of Journalists and controller Reed International. We apologise to readers and advertisers for its late appearance. The next issue of Electronics and Wireless World, cover dated August/September should be published on 15 August.

www.americanradiohistory.com Front cover pictures Editor David Read's PAL PHILIP DARRINGTON s for the 01-6613128 , R..;nllusinkey puter colour tv microcomputer enhancement board, Deputy Editor BBC uter- the comp ument aá also pictured on page GEOFFREY SHORTER, B.Sc. U sing the economiinuamusica disPla7 generators, analvstsan comprising PAL 01-6618639 ltoolforstor°y;e 37, edterfaceu aàon of music. modifier and comb filter decoder. Technical Editor Oeugn MARTIN ECCLES NEXT MONTH 01-6618638 Laboratory equipment for Projects Editor measurement in linear RICHARD LAMBLEY motion includes a 01-6613039 computer -to -air interface. Kosta Detection of rider position fh N. Sham?nna -_ _- K.Bhawam enables RML computer to News Editor reception S1u+nker carry out experiments and DAVID SCOBIE `ashankara television iree Ila, display results. 01-6618632 aPPa papaya Kud In Stage Lighting System, with \'.RKa Kosta YY. forty 1 kilowatt circuits are Drawing Office Manager o antennalesrf.enet'frjssigna remotely controlled with ROGER GOODMAN nano coup ceive tv Novel one cable linking desk and 01-6618690 vetatiotioncanoPTt°m. dimmers. A Z80 multiplexes data from the controls. Technical Illustrator BETTY PALMER gne tool. Dr Ken Smith of Kent M.0 University contributes a short series on power Advertisement Manager trro BOB NIBBS, A.C.I.I. b. supply design, concentrating on the 01-6613130 J.R..ti.Sckinson. switched -mode variety. by . R \M.bc.. o And John Adam's SC84 switch -regulated power MICHAEL DOWNING Variable -speed supply is suitable for any 01-6618640 playback application requiring an video o.crawide efficient, simple and ASHLEY WALLIS recorders th economical power unit singC-formces 01-6618641 speed range.continuesof the effectthe with either fixed or description waveforms. on video variable output. John also process gives some SC84 Northern Sales

.44 construction tips. HARRY AIKEN 061-872 8861 Current issue price 85p, back issues (if available) £1.06, at Retail and Trade Counter, Units 1 & 2, Bankside Industrial Midland Sales Centre, Hopton Street, London SE1. BASIL McGOWAN Available on microfilm; please contact editor. By post, current issue £ 1.30, back issues 021-356 4838 (if available) £ 1.40, order and payments to EEP Sundry Sales Dept., Quadrant House, The Quadrant, Sutton, Surrey SM2 5AS. Classified Manager Tel.: 01-6613378. BRIAN DURRENT Editorial & Advertising offices: Quadrant House, The Quadrant, Sutton, 01-6613106 Surrey SM2 5AS. Telephones: Editorial 01-661 3614. Advertising 01-6613130. See leader page. IAN FAUX fmt Telex: 892084 BISPRS G (EEP) 01-6613033 Subscription rates: 1 years £15 UK and a £19 outside UK. e Student rates: 1 year £ 10 UK and £ 12.70 Production outside UK. Distribution: Quadrant House, The BRIAN BANNISTER Quadrant, Sutton, SurreySM25AS. (Make-up and copy) Telephone 01-6613248. Subscriptions: Oakfield House, 01-6618648 Perrymount Road, Haywards heath, Sussex RH16 3DH. Telephone: 04444 459188. Please notify a change of address. Publishing Director USA: $49.40 surface mail, $102.60 DAVID MONTGOMERY airmail. Business Press International (USA). Subscriptions Office, 205 E. 42nd 01-6613241 Street, NY 10017. LISA mailing agents: Expediters of the Printed World Ltd, 527 Madison Avenue, International Agents and Suite 1217, New York, NY 10022, 2nd class the Advertisers Index postage paid at New York. ® Business Press International Ltd 1984. appear at the back of this ISBN 0043 6062. issue.

www.americanradiohistory.com 01-4521500 TECHNOMATI(: LTD 01-450 6597

ACCESSORIES Basic II Rom £32.00d Single Disc Cable £6.00d BBC Micro Computer System View Word Processor Rom £52.00c DoubleDisc Cable £8.50d Wordwise W/P Rom £34.00c 3M DISCS with Lifetime Warranty ACORN COMPUTER SYSTEMS BCPLROM+Disc £87.00b OFFICIAL DEALER 40T SS/SD Pkt of 10 £16.00c BBC Model B £348.00a Disc Doctor Utility Rom £28.00d 40T DS/DD Pkt 10 £22.00c availability BBC Model B+Econet £389.00a Termi Emulator Rom £28.00d Please phone for 80T SS/DD Pktbf 10 £26.00c BBC Model B+DFS £429.00a ULTRACALC Rom (BBC Publications) £65.00c BBC Model B+ DFS+Econet 80T DS/DD Pkt of 10 £30.00c £470.00a Gremlin debug Rom £28.00d 3' Double Sided Disc Each £4.50c 65022nd Processor £175b Computer ConceptsGraphics Rom £28.00d FLOPPICLENE Drive Head Cleaning Kit. £14.50c Acorn Electron £169.00b IXMON £20.00d Disc Library Case £1.90d BBC Teletext Receiver £195.00a TOOL KIT £20.00d Disc FileCase30/40 £8.00c Printmaster Rom (FX80) £28.00d Disc Lockable Case 30/40 £15.00c UPGRADE KITS Communicator Rom £59.00c A to B Upgrade Kit £60.00d Disc Lockable Case 60/70 £27.00b DFS Kit £95.00d Installation £15.00 BBC COMPATIBLE 5.25" DISC DRIVES SOFTWARE: Econet Kit £55.00d Installation £25.00 (All include cables, manual + format disc) ACORN/MERLE BUSINESS SOFTWARE Speech Kit £47.00d Installation £10.00 100K (40 Track)Teac £135.00a Invoicing, Stock Control, Accounts Payable, 100K (40 Track) with su Tec £145.00a Accounts receivable, Order processing, ECONET ACCESSORIES 200K (40/80 Track) Teac £175.00a Mailing System Each £22.65d Printer Server Room £41.00b 200K (80 Track) with psuTec £190.00a GEMINI Business- Full Range File Server Level l £86.00b 400K (80 Track DS) Mitsubushi £190.00a ACORNSOFT- Full Range File Server Level 2 £216.00b 400K (80 TOS) with psu Mitsubushi £225.00a ACORN LANGUAGES including BCPL, LISP Clock+2Terminators £92.00b ALL PRICES EXCLUDE VAT. 2x100K (40 Track) with psu Teac £300.00a FORTH with Manuals Econet User Guide £10.00d Full Range Please add carriage 50p unless indicated as follows: 2x200K (40/80 Track) with psu Teac £400.00a BBCSOFT- (a) £8 (b) £2.50 (c) £1.50 (d) £1.00 BBC FIRMWARE 2x400K (80 Track DS) with psu Mitsu £420.00a PRORAM POWER- Full Range 1.2 Operating System £7.50d 3" Hitachi 100K Drive £150.00c BEEBUGSOFT- Full Range

TORCH Z80 DISC PACK ACORN IEEE INTERFACE "TIME -WARP' The proven upgrade for the BBC Micro. Comprising 2 x 400K disc A full implementation of the IEEE -488 standard, provid- REAL-TIME-CLOCK/CALENDAR drive, Z80 processor with 64K of memory, and a CP/M compatible ing computer control of compatible scientific & technical operating system, it opens up the vast range of CP/M software, includ- equipment, at a lower price than other systems. Typical A low cost unit that opens up the total range of ing advance languages, scientific and business applications. The sys- applications are in experimental work in academic and Real -Time applications. With its full battery tem is supplied with the PERFECT software range including PERFECT industrial laboratories. The interface can support a backup, possibilities include an Electronic WRITER, PERFECT SPELLER, PERFECT CALC, and PERFECT network of up to 14 other compatible devices, and would Diary, continuous display of 'on -screen' time typically link items test FILE. Full TORCHNET software is also supplied allowing sophisticated several of equipment allowing and date information automatic document dat- will to information, them to run with the optimum of efficiency. The IEEE Fil- networking between other units. This allow access in applic- and communication, between up to 254 suitably upgraded BBCs. ing System ROM is supplied. £282. ing, precise timing & control scientific ations, recreational use in games etc - its uses NEW TORCH Z80 PACK PRICE £699. BUZZ BOX A full spec pocket size direct connect modem are endless and are simply limited by one's SOFTWARE PACKAGE INCLUDES Z80 BASIC with both Originate and Answer modes. this BT approved imagination. Simply plugs into the user port - modem conforms to CCITT V21 300/300 Baud Standard. no specialist installation required - No ROMS. Phone for details about the 20Mbyte Hard Disc Pack, and the Battery/Mains powered plugs directly into telephone line. Supplied with extensive applications software. 68000 Hard Disc Pack with UNIX Operating System. Modem Z69 head Z3:50 Ext PSU Z8:00 Please phone for details. £29.00 + £2.50 carriage. NOW AVAILABLE - The TORCH Z80 SECOND PROCESSOR CARD - for those who already have suitable disc drives. The card is BOOKS ATTENTION* supplied with all th free perfect software and Z80 basic, as detailed * * * above, presenting a very attractive package. £299. We have a large selection of books on the BBC and other All prices in this double page spread are Torch ZHO 240 Mbyte Hard Disc + 400K Flopy. £1995 (a) titles. Please ask for details. No VAT on boobs. subject to change without notice. PRINTERS ACCESSORIES MONITORS CASSETTE SOFTY II EPSON FX-80 £325.00a Parallel Printer Lead £10.00d Microvitec 1431 14"RGB Std Res £179.00a RECORDERS This low cast intelligent eprom pro- EPSON RX-80FT £250.00a Serial Printer Lead £8.00d Microvitec 1431 PS 14'RGB/PAL+Sound £225.00a grammer can program 2716, 2516, SANYO DR 101 Data Recorder £30.006 EPSON FX-100 £480.00a Epson Serial Interface 2K 8148 £60.00c Microvitec 1451 14'RGBB Med Res. £295.00a an adaptor, 2564 Daten Slim Line £20.00c 2532, 2732, and with EPSON DX -100 £375.00a Epson Serial Interface8143 £50.00c Microvitec 1441 14'RGB Hi Res £420.00a BBC Tape Recorder £28.50b and 2764. Displays 512 byte page on PrirrterSharer+CableSet £88.00c FX80 Dust Cover £4.00d 203120'RGBStd Res £287.00a Cassette Lead £3.00d has a serial and parallel I/O rou- JUKI 6100 Daisy wheel £350.00a Epson Paper Roll Holder £17.00c KAGA Vision Ex 12-RGB £195.00a N - Computer Grade C-12 cassette £0.45d MCP40 Col. Printer/Plotter £110.00a FX-80 Tractor Attachment £37.00c KAGA Vision II Hi Res £260.00u tines. Can be used as an emulator, cas- Computer Grade Cassette 10 off £4.00c Grafpad Graphics Tablet £125.00c PAPER Fanfold 2000 sheets £13.50b KAGA Vision Ill 12-RGB Super Hi sette interface. SoftyII £169 (b) Adap- Phillips Mini data cassette £3.00d Ribbon MX80/RX80/FX80 £6.50c Res £358.00a tor for 2764/25625.00 (c). KAGA 12"Green Hi Res £106.00u SANYO DM8112CX 12"Green Hi Res £99.00a

SMART MOUTH: UV ERASERS PRODUCTION PROGRAMMER: The original 'infinite speech'. Still the best UV1T Eraser with built-in timer and mains P8000 EP 8000 A ready built totally sett contained speech synthesiser unit, attract- indicator. Built-in safety interlock to avoid ively packaged with built-in speaker, AUX output socket etc. no P8000 provides reliable gang pro- This CPU controlled Emulator Pro- - harmful rays. installation problems! It allows the creation of any English word, with accidental exposure to the UV gramming of up to 8 EPROMS simul- grammer is a powerful tool for both both ease and simplicity, while, at the sometime being very econom- It can handle up to 5 eproms at a time with an taneously with device sizes up to 16K Eprom programming and develop- ical in memory usage. You can easily add speech to most existing average erasing time of about 20 mins. £59 x 8 bytes. Devices supported range ment work. EP 8000 can emulate and programs. Due to its remarkable infinite vocabulary, its uses spread + £2 p&p. UV1 as above but without the from 2704 to 27128 in single and three program all eproms up to 8K x 8 bytes, applications these throughout the whole spectrum of computer - timer. £47+£2p&p. For Industrial Users, we rail versions. Simple menu driven can be used as stand-alone unit for include industrial, commercial, educational, scientific, recreational offer UV140 & UV141 erasers with handling editing and duplicating EPROMS, as a etc. No specialist installation no need to open your computer, sim- operation ensure easy eprom selec- - capacity of 14 eproms. UV141 has a built-in in programmer as an eprom ply plugs into the user port - and due to the simple software, no tion and reliable programming mini- slave or ROMS are needed. SMARTMOUTH is supplied with demo and timer. Both offer full built-in safety features mum programming limes. £695 + £6 emulator £695 (a). development programs on cassette, and full software instruction. UV140 £61, UV141 £79, p&p £250. carriage. f37 + £2.50 carriage.

BBC EPROM PROGRAMMER: CONNECTOR SYSTEMS A fully sett -contained mains -powered eprom programmer I.D. CONNECTORS JUMPER LEADS AMPHENOL RIBBON housed in an attractive finished case. It is able to program (Speedblock Type) 24" Ribbon Cable with Headers 2716, 2732/32A, 2764 & 27128's in a single pass. It is sup- No of Header Recep- Edge 14 -pin 16 -pin 24-pin 40 -pin CONNECTORS CABLE plied with vastly superior software when compared to any ways Plug tacle Conn. lend 145p 165p 240p 350p Solder IDC (Grey/meter) 2 ends 210p 230p 345p 540p currently programmer. In addition to normal 10 90p 8p 120p 36 -way plug Centronics available similar 125p programming, you now to load favourite 20 145p 195p £5.25 £5.25 10 -way 40p eprom are able your 26 17Sp 150p 240p 24" Ribbon Cable with Sockets 16 -way 60p basic programs onto eprom. 34 200p 160p 320p 36 -way socket Centronics 20 -way rap 20 -pin 26-pin 34-pin 40-pin £5.50 Menu Driven Software provides user friendly options 40 220p 190p 340p lend 160p 200p 290p 300p £5.50 26 -way 120p for programming the eprom with: 50 235p 200p 390p 2 ends 290p 370p 410p 525p 24-way plug IEEE £5.00 £4.75 34-way 160p a) Basic programs 24-way socket IEEE £5.00 E4.75 00 -way 190p Ribbon Cable with D. Conn. PCB Mtg Skt Ang pin 50-way 200p b) Ram resident programs. D CONNECTORS 64 -way 290p c) Any other program. No of ways 25 -way Male 500p Female 550p 24 -way (6.00.36 -way £6.50 9 15 25 37 'Programmer can read, blank -check, program & verify at MALE any address/addresses on the Eprom. Solder 80p 105p 160p 250p JUMPERS EURO EDGE Personality selection is simplified by a single rotary Angled 150p 210p 250p 365p RS 232 (25 -way DI switch. FEMALE CONNECTORS CONNECTORS 24" Single end Male k5.00 DIN41617 Plug Skt. 0.1" 0:`x Programming voltage selector switch. Solder 105p 160p 200p 335p 24" Single end Female E5.25 21 -way 160p 1650 206 -way (Comma oral - 3000 Angled 165p 215p 290p 440p Full Editor with ASCII Disassembles, allowing direct 24" Female -Female E10.00 31 -way 170p 170p 2x10 -way ICommo- Hoods 90p 85p 90p 100p modification data in HEX or ASCII. 24" Male-Male E9.50 dore) 150 IDC 15 -way plug 340p. Socket 400p DIN 41612 for of pro- 24" Male -Female E9.50 2x32 -way St. Pin 230p 275p 2 x 12 -way Ivic 201 Continuous display of time left completion IDC 25 -way plug 385p. Socket 450p gramming. 2 032 -way Ang. Pin 275p 320p 20 18 -way 1109 300p 1759 220p Continuous display of current addressee as they we 3032 -way St. Pin 260p 2023 -way IZX811 TEXTOOL ZIF DIL HEADERS 3x32 -way Ang. Pin 375p 400p 2025 -way 2209 being programmed. 2 00p 24-pin E5.75 1 DC Skt A+ 8 275p A+ C 350p 2028 -way (Spectrum) SOCKETS Solder Type IOC Type 28 -pin E8.00 40-pin £9.75 For 2 x 32 -way please specify spac- 2x36 -way 250p 14pn 40p 1043 -way leOp The programmer comes complete with cables, software & 110p ing (A+B,A+CI 2x22 way 1909 operating manual. 150p DIL SWITCHES 24Pí1 100p 2043-way 3959 £89 + £2.50 carriage. Software on disc £2 extra 2259 TEST CLIPS 4 -way 70p 8 -way 130p 14 -pin 375p 16 -pin 400p 1.017 -way 5009 6 -way 100p 10 -way 150p 40-pin E10.30 2x50 -way IS100connl 6100900p

4 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com 74278 74LS292 900p 4021 80p MIZEGMB 370p LINEAR ICs MODULATORS 7400 POA100p 74279 1509 74LS293 120p 4022 80p COMPUTER COMPONENTS 74283 170p 74LS295 140p 4023 509 6MHz UHF 375p 7401 60p AD7581 £15 LM386 90p' SFF96364 8009' 8795/6 90p 7402 100p 74285 350p 74LS297 900p 4024 509 CPUs 8288 £11 CRT 8MHz UHF 74290 140p 74LS298 150p 4025 30p ADC0808 1190p LM387 120p $N76477 600p 8755A 1800p 8797/8 90p 450p 7403 BOP 1802CE CONTROLLER 81LS95 220p 74293 140p 74LS299 250p 4026 100p AN103 200p LM389 180p SN76489 400p 650p 9901 £3 7404 POA100p 2650A £12 81LS96 220p 74298 225p 74LS321 300p 4027 SOp AY1-5050 99p LM391 180p SN76495 400p 9902 £3 CRT6545 900p CRYSTALS 7405 60p AY3-127C 750p LM392N 60p SP0256AL2 6502 400p 81LS97 220p 7406 POAp 74351 225p 74LS324/624350p 4028 609 TMS9901 350p CRT5027 £18 74365A 100p 74LS348 250p 4029 90p AY3-1350 350p LM393 100p 800p 6502A 650p TMS9902 350p CRT5037 £18 81LS98 220p 32.760KHr 7407 POAp 150p 6800 290p 88LS120 74366A 100p 74LS352 150p 4030 45p AY3-8910 400p LM394CH 350p TA7120 Z80P1O EF9365 E36 400p 100p 7408 100p 7A7130 160p 6802 300p 300p 74367A 100p 74LS353 150p 4031 160p AV3-8912 500p LM709 50p Z80AP10 350p EF9366 £38 100KHZ 400p 7409 60p TA7204 150p 6809 650p 9637AP 160p 74368A 100p 74LS356 220p 4032 80p LM710 50p Z80CTC 300p MC6845 650p 200KHZ 400p 7410 100p TA7205 90p 68809 £12 ZN425E-8 350p 74376 200p 74LS363 180p 4033 160p CA3019A 100p LM711 70p ZBOACTC 350p MC6845SP Frog in MHz 7411 OOP 7A7222 150p 6809E £12 ZN426E-8 350p 74390 225p 74LS364 180p 4034 200p CA3028A 150p LM725C 300p Z80ADART 750p 1.0 325p 7412 50p CA3046 70p LM733 75p TA7310 150p 68809E £16 ZN427E 600p 7413 75p 74393 225p 74LS365 100p 4035 BOp 850p MC6847 650p 1.8432 300p 74LS366 100p 4036 2709 LM741 20p TBA231 120p 6800L8 E48 P8275 £27 ZN428E-8 450p 7414 90p 74490 3009 Z80ADMA £10 2 00 250p 74LS367 4037 150p CA3059 350p LM747 70p TBA800 80p 8035 550p SFF96364 E8 7416 POA200p 100p Z80SI0/1/2 £9 DISC 2.45760(L) 74LS368 100p 4038 80p CA3060 350p LM748 40p TBA810 100p 8039 550p TMS9918 300p 210p 7417 POA200p CA3080E 80p LM1011 480p TBA820 80p 8080A 350p MEMORIES 7420 7 MU=SOO P041000 74LS373POA300p 4039 250p TMS9927 £16 CONTROL 2.45760151 74LS01 60p 74LS374POA300p 4040 80p CA3086 60p LM1014 1 TBA950 225p 8085A 18000 TMS9928 £20 275p 7421 100p 8086 2102 250p ICs 74LS02 POA100p 74LS375 100p 4041 60p CA3089E 250p LM1801 300p TC9109 500p E22 TMS9929 £16 2.5 250p 7422 60p TCA210 350p 8088 2200p 21078 500p 74LS03 60p 74LS377 180p 4042 75p CA3090AO LM1830 8271 £45 2.662 250p 7423 6705p 8748 3600p 2111A-35 400p INTERFACE 74LSO4 POA100p 74LS378 150p 4043 75p 375p LM1871 300p2 TCA220 350p 7425 p 2114-2L 8272 £20 3.276 150p 74LS05 709 74LS379 140p 4044 75p CA3130E 90p LM1872 300p TCA270 350p 7MS1601 £12 500p 7426 2114-4L ICs FD1771 £20 3.5795 120p 60p 74LS390 140p 4046 90p CA3130T 110p LM1886 500p TCA940 175p TMS99801200p 7427 80p 74LS08 100p 2147 450p FD1791 £22 4.0 150p 74LS09 60p 74LS393 200p 4047 85p CA3140E 60p LM1889 350p TDA1004A 500p TMS9995 £12 AD558CJ 775p 4.194 7428 60P 4027-3 300p FD1793 £23 200p 74LS10 100p 74LS395A 140p 4048 60p CA3140T 110p LM2917 250p TDA1010 250p W055 1450p AD561J £20 4.43 125p 7430 60p 4116-15 200p FD1795 £28 74LS11 70p 74LS399 210p 4049 48p CA3160E 100p LM3302 75p TDA1022 500p Z8 £24 AM25S10 350p 4.608 250p 7432 POAp 4116-20 175p FD1797 E28 74LS12 60p 74LS445 180p 4050 48p CA3161E 150p LM3900 50p 70A1024 120p Z80 300p AM25LS2521 TMS9909 £12 4.9152 250p 7433 TDA1170 4116-3 500p 74LS13 75p 74LS465 220p 4051 80p CA3162E 450p LM3909 120p 300p Z80A 400p WD2793 4200p 5.0 175p 7437 60p TDA2002 4764-2 450p 74LS14 120p 74LS467 220p 4052 ßO9 CA3189E 300p LM3911 160p 325p ZBOB 950p AM26LS31350p WD2797 4200p 6.0 150p 7438 100p 120p TDA2003 325p 4164-15 500p 74LS15 60p 74LS490 170p 4053 BOp CA3240E LM3914 350p 1 WD1691 1500p 6.144 175p 7439 5 TDA2004 SUPPORT 4416-15 500p 74LS20 60p 74LS540 200p 4054 90p CA3280G 225p LM3915 350p 300p AM26LS32 WD2143 600p 70 150p 7440 60p TDA2006 350p 4532-20 250p 74LS21 60p 74LS541 200p 4055 90p D7002 600p LM3916 350p DEVICES 1 7.168 175p 7441 120p TDA2020 4816AP-3 475p CHARACTER 74LS608 700p 4056 100p DAC0800 200p LM13600 110p 320p D7002 600p 8.0 175p 7442A 75p 74LS22 70p TDA2030 250p 2651 £12 5101/5501450p 74LS26 70p 74LS610 1900p 4059 450p DAC0808 200p M51513L 230p DAC80 £28 GENERATORS 8.867 175p 7444 120p TDA2541 400p 3242 800p 5516 1000p 74LS27 70p 74LS612 1900p 4060 90p DG308 300p M51516L 500p 3245 450p DM8131 325p 10.0 175p 7445 160p 190p 200p TDA3560 990p 6116P-3 850p R03-2513 74L628 70p 74LS626 350p 4063 90p HA1366 MB3712 6520 300p DP8304 300p 10.50 250p 7446A 120p 250p 400p TDA7000 3509 6116LP-3 9509 U.C. 7509 74LS30 60p 74LS628 350p 4066 HA1388 MB3730 6522 350p DS3691 350p 10.70 200p 7447A 120p 700p 150p TL061CP 50p 6264-15 3500p L.C. 700p 74LS32 POA100p 74LS629 300p 4067 250p CL7106 MC1310P 6522A 550p D58830 140p 11.0 300p 7448 120p CL7611 95p TL062 75p 6514-45 650p DM86564 £12 74LS33 60p 74LS640 250p 4068 30p MC1413 130p 6532 6500 DS8831 150p 120 150p 7450 CL7650 400p 40p TL064 1109- 680 180p MC66760 750p 74LS37 60p 74LS640 1300p 4069 30p MC1458 6551 650p DS8832 150p 14.0 175p 7451 66Óp CL7660 250p MC1493 100p 7L071 45p 474S189 225p 74LS38 100p 74LS641 250p 4070 30p 6821 200p DS8833 225p 14.318 175p 7453 60p CL8038 300p TL072 600 74S201 350p KEYBOARD 74LS40 130p 74LS642 1300p 4071 30p MC1495L 350p 68821 250p DS8836 150p 14.756 250p 7454 ICM72160 TL074 110p 745289 225p 74LS42 100p 74LS643 250p 4072 30p 24006 MC1496 70p 6829 £12.50 DS8838 225p ENCODER 15.0 200p 7460 765pp CM7217 900p TL081 45p 93415 600p 4073 30p MC3340P 2009 DS8880 170p 16.0 200p 7470 75p 74LS47 140p 74LS643 1300p 100p 6840 375p 93425 600p 4075 309 CM7555 MC3401 50p TL082 55p LF13201 450p AY 523761156p 18.0 200p 7472 75p 74LS48 140p 74LS644 350p 140p 68840 6000 93L422 950p 4076 909 CM7556 MC3403 65p TL083 75p MC1488 1000 74C922 480p 18.432 150p 7473 75p 74LS51 60p 74LS645 350p 300p 6850 200p X2210 TBA 4077 309 LC7120 MF1OCN 360p TL084 100p MC1489 100p 74C923N 500p 19.969 150p 7474 100p 74LS54 ß0p 74LS645 400p LC7130 325p TL094 2009 68850 250250p 74L655 60p 74LS668 120p 4078 309 MK50240 900p 6852 MC3418 950p 20.0 450p 7475 100p LC7137 350p TL170 50p RATE 74LS669 4081 309 MK50398 790p 6854 650p MC3446 250p BAUD 124 0 300p 7476 80p 74LS73A 75p 150p LF347 150p TL430C 120p ROMs 100p 74LS670 225p 4082 30p ML920 500p 68054 MC3459 450p GENERATORS 48.0 175p 7480 74LS74A LF351 60p UA1003-3 12 74LS682 650p 4085 60p MM6221A 935p PROMs MC3470 650p 116 300p 7481 2pp 74LS75 90p LF353 100p UA2240 120p 6875 MC14411 900p 74LS76A 75p 74LS684 650p 4086 70p 300p 950 MC3480 850p PX010001200p 7483A 120p LF355 100p UAA170 200p 745188 180p COM82B116 B7508O 74LS687 4089 125p NE531 150p 8 555 1 OOp MC3486 500p 7484A 250p 74LS83A 120p 550p 100p 74S287 200p 4093 48p LF356F NE544 190p UCN4801 A 350p 8156 750p MC3487 300p 470Op 7485 120p 74LS85 150p 130p 745288 180p EMBEIBil 4094 100p LF357 NE555 22p ULN2001A130p 8205 225p MC4024 325p 7486 70p 74LS86 75p LF13331 350p 745387 225p REAL TIME 74LS90 74500 100p 4095 909 NE556 50p ULN2002A130p 8212 3009 MC4044 325p UARTs 7489 300p 90p LMiOC 325p 745473 475p CLOCK 74LS91 110p 74502 100p 4096 909 NE564 400p ULN2003A130p 8216 200p MC14412 750p 7490A 75p 74504 120p LM301A 25p NE565 150p AV -3-1015P 74LS92 100p 4097 290p ULN2004A130p 8224 200p 75107 90p 300p MC6818P 550p 7491 70p 74505 100p LM307 45p NE566 150p EPROMs 74LS93 90p 4098 90p ULN2068 350p 8226 250p 75110/12 160p AV -5-1013P MM58174AN 74924 970p 74508 100p 4099 909 LM308CN 75p NE567 140p ULN2802 250p 8228 250p 2532 450p 75114/15 160p 7493A 74LS95B 100p LM310 120p 300p 800p 74510 100p 4501 409 NE570 400p ULN2803 250p 8243 1400p 2532-30 700p 75121/22 140p 74LS96 160p 70p COM8017 300p MSM5832RS 7494 150p 74S11 100p 4502 60p LM311 NE571 400p ULN2804 2509 8250 1400p 2564 700p 75150P 120p 74LS107 75p T50p 1M6402 360p 350p 7495A 90p 74S20 100p 4503 60p LM318 NE592 75p UPC575 275p 8251A 16000 2708 400p 75154 140p 74LS109 75p LM319 T60p TR1602 300p 7496 100p 74522 100p 4504 90p NE5532P 200p UPC592H 200p 8253C-5 1800p 2716 350p 75159 220p 74LS112 909 LM324 50p TELETEXT 7497 250p 74530 100p 4505 NE5533 160p UPC1156H £3 8255AC-519009 2732 450p 75365 150p 74LS113 75p 400p 90p ZIF SKIS 74100 2209 74S332 180p 4506 120p LM334Z NE5534P 120p 350p 8256 £36 75451/2 72p DECODER 74LS114 75p LM335Z 140p UPC1185H 2732A-2 900p 74107 75p 74537 180p 4507 45p NE5534AP 200p 400p 8257C-5 750p 75453/4 72p (TEXTOOL) 74LS122 100p LM339 40p XR210 2732A-35 550p SAA5020 600p 74109 75p 74551 150p 4508 160p PLL02A 500p XR2206 400p 8259C-5 750p 2764-25 900p 75491/2 65p 24 pin 575p SAA5030 700p 74110 90pp 74LS123 200p LM348 65p 74S74 120p 4510 759 RC4136 60p XR2211 575p 8279 750p 27128-25 2500p 8726 120p 28 pin 800p SAA5041 £16 74111 74LS124/629300p LM358P 60p 74LS125 90p 74585 450p 4511 75p S5668 300p XR2240 120p 8284 600p 27128-30 2200p 8728 120p 40 pin 975p SAA5050 900p 74116 220p 74586 1809 4512 75p LM377 225p SAA1900 £16 74LS126 90p LM380 75p ZN414 BOp 74118 2009 745112 150p 4513 140p SAD1024A ZN419C 190p 74119 74LS132 90p LM381AN 180p LOW PROFILE TI 300p 745113 120p 4514 130p 1150p 130p SOCKETS BY WIRE WRAP SOCKETS BY TI 74LS133 90p LM382 1800 ZN423E 74120 1809 745114 120p 4515 130p ZN424E 130p 74121 90p 74LS136 75p 8 pin 9p 18 pin 16p 24 pin 24p 8 pin 30p 18 pin 50p 24 pin 75p 74LS138 120p 745124 550p 4516 75p ZN425E 350p 1 14 pin 10p 20 pin 18p 28 pin 26p 14 pm 42p 66p 74122 745132 120p 4517 200p VOLTAGE REGULATORS 300p 20 pin 28 pin 100p 74LS139 1209 ZN426E 16 pin 119 22 pin 22p 40 pin 309 16 45p 75p 74123 150p 745133 100p 4518 759 FIXED PLASTIC ZN427E 600p pin 22 Pin 40 Pin 130. 74125 100p 74LS145 150p 74LS147 220p 74S138 180p 4519 759 lA ZN428E 450p 74126 74S139 180p 4520 75p Ve 74LS148 220p 5V 7805 50p 7906 45p ZN429E 210p BFR80/1 32p TIP31C 45p 2N2906A 30p 3N12ß 200p 74128 12Op TURNED PIN 745140 100p 4521 125p 79067908 45p ZN450E 750p BFR96 180p 74132 100p 74LS151 100p 6V 7806 60p TIP32A 45p 2N29074 30p 3N140 200p 745151 200p 4522 90p 50p ZN459CP 300p 45p LOW PROFILE 74136 90p 74LS153 100p 8V 7808 60p BFX29 T1P32C 40p 2N2926 12p 3N141 2009 74LS154 300p 745153 200p 4526 90p 12V 7812 50p 7912 45p ZN1034E 200p BFX30 45p TIP33A 70p 2N3053 40p 200p SOCKETS 74141 18Qp 74S157 300p 3N201 74LS155 140p 4527 90p 15V 7815 50p 7915 45p ZN1040E 200p BFX84/5 30p TIP33C 80p 2N3054 609 3N204 2009 74142 745158 300p 4528 75p 7918 50p ZNA134J £23 30p 74143 480p 74LS156 125p 18V 7818 60p BFX86/7 TIP34A 90p 2N3055 55p 40290 250p 8 pn 25p 74LS157 100p 745163 400p 4529 90p 24V 7824 809 7924 45p ZNA234E 950p BFX88 40p TIP34C 120p 2N3442 140p 14 pin 40p 74144 4809 745174 3009 4531 75p 45p 74LS158 100p 51./ 100mA 7805 30p 79L05 BFX89 180p TIP35A 120p 2N3553 240p 16 pn 45p 74145 1 745175 320p 4532 800 TRANSISTORS DIODES 74147 225p 74LS160A 140p 6V 100mA 78L06 30p BFV50 30p TIP35C 140p 2N3584 250p 18 pin 50p 74S188 180p 4534 400p 78L08 30p AD161 /2 45p 20 pn 56p 74148 1809 74LS161A 140p 8V 100mA BFY51/2 40p TIP36A 140p 2N3643/4 48p BV127 1 p 745189 225p 4536 220p 78L12 309 79L12 50 BC107/8 189 24 pn 75p 74150 74LS162A 140p 12V 100mA BFY56 33p TIP36C 150p 2N3702/3 lop BYX36300 20p 225p 745194 400p 4538 90p 78L15 309 79L15 5Óp BC109C 20p 28 pin 90p 74151A 100p 74LS163A 140p 15V 100mA BFY90 90p TIP41A 50p 2N3704/5 16p 0647 10p 745195 400p 4539 90p BC169C 16p 40 pn 120p 74153 1009 74LS164 140p OTHER BRV39 45p TI41C 55p 2N3706/7 16p 0490/91 9p 74LS165A 160p 74S196 350p 4541 90p BC172 18p BSX19/20 30p TIP42A 60p 74154 250p 450p REGULATORS 2N3708 16p OA95 9p 74LS166A 2509 740200 4543 100p BC177/8 30p BU104 225p TIP42C 65p 2N3773 200p 0A200 9p 74155 100p 745201 320p 4551 250p TRIACS 74LS168 200p 78P05 900p BC179 30p Bä05 190p TVP54 160p 2N3819 40p 0A202 10p 74156 1108 745225 650p 4553 220p LM309K 1A 5V 140p 74LS169 200p LM317K T03 250p 78H12 850p BC182/3 '15p BU108 250p TIP55 180p 2N3823 30p 1N914 4p PLASTIC 74157 119p 74S240 250p 4555 60p 74LS170 220p LM317T 150p 78HGKC 600p BC184 16p BU109 225p TIP120 75p 2N3866 120p 1N916 7p 74159 320p 745241 300p 4556 70p 74LS173A 120p 225p 78H05KC 650p BC187 30p 8U126 150p TIP121 75p 2N3902 700p 1N4148 4p 400V 60p 74160 120p 745244 400p 4557 250p LM337T 3A 74LS174 120p 5V 450p 78GUIC 225p BC212/3 16p1 BU180A 120p TIP122 80p 2N3904 22P 1N4001/2 5p 400V 741,31 75p 745251 300p 4560 120p LM323K 3A 6A 70p 74LS175 120p 350p79GUIC 250p BC214 189 BU205 200p T1P125 75p 2N3905 22p 1N4003/4 74162 90p 745257 300p 4566 200p LM3507 6A 500V 88p 74LS181 250p LM723N 50p 79HGKC 700p BC237 l6p 8U208 200p 119126 80p 2N3906 24p 1N4005 75p 74163 90p 74S258 300p 4568 300p 8A400V 74LS183 270p BC327 16p BU406 145p TIP142 120p 1N4006/7 7pp 74164 90p 74S260 100p 4569 200p TL494 30091CL7660 250p 2N4036 85p BA 500V 95p 74LS190 130p LM305AH 250p BC337 16p BUX80 600p T1P147 120p 2N4037 65p 1N5401/2 74165 t00p 745261 300p 4572 509 TL497 300p 12A 400V 85p 74LS191 130p 78540 250p SG3524 300p BC338 16p BUV69C 350p TIP2955 90p 2N4123/4 27p 1N5403/4 14p 12A 105p 74166 120p 745262 850p 4583 759 500V 74LS192 130p BC461 40p E310 50p T1P3055 70p 2N4125/6 27p 1N5404/5 14p 16A 400V 110p 74167 400p 745283 300p 4584 OPTO ELECTRONICS 74LS193 130p 48p BC477/8 36p MJ413 250p 11993 30p 19p 74170 250p 74S287 225p 4585 65p 2N4401/3 25p 1N5404/7 16A 500V 130p 74LS194A 130p 2N5777 TIL32 BC516/7 50p MJ802 400p VN10KM 50p 2N4421 120p 15920 9p 74172 750p 745288 180p 4724 150p 48p 55p 728000 130p 74LS195A 130p OCP71 TIL78 56p BC5478 20p MJ2501 225p VN66AF 90p 2N4ß71 50p TIC 206D 60p 74173 180p 745289 225p 14411 900p 74LS196 130p ORP12 120p TIL31A 120p BC548C 12p MJ2955 90p VN88AF 100p 2N50ß7 30p BRIDGE TIC 226D 75p 74174 1 74S299 650p 14412 ß50p 74LS197 130p ORP60 120p 7081 120p BC549C 16p MJ3001 225p ZTX108 16p 2N5089 30p TIC 246D 110p 74175 1 745373 400p 14416 300p RECTIFIERS 74LS221 140p ORP61 120p TIU00 75p BC557B 14p MJ4502 400p ZTX300 18p 2N5172 27p 74176 150p 745374 400p 14419 300p 74LS240 250p BC559C 24p MJE340 60p ZTX452 45p 2N5191 90p 14 50V 19p 74177 1509 745387 225p 14490 550p ISOLATORS 74LS241 250p OPTO BCV70 30p MJE2955 150p ZTX500 20p 2N5245 40p 14 100V 20p 74178 250p 745472 475p 14495 igglaiLa 74LS242 140p 450p TIL111 70p BCV71 36p MJE3055 120p ZTX502 20p 14 400V 25p 74179 250p 745571 300p 14500 700p ILD74. 130p 2N5401 60p 3A 400V 45p 74LS243 140p TIL112 70p BD131 75p MPF102 40p ZTX504 22p 2N5459 30p 14 600V 30p 74180 150p 500p 14599 MCT26 100p BA 600V 18Op 74LS244 300p 745573 350p TIL113 8D132 80p MPF103/4 40p ZTX552 55p 2A 50V 30p 74181 MCS2400 190p 70p 2N5460 80p 12A 400V 160p 74LS245 350p 4000 CMOS 22100 350p 70p BD135/6 40p MPF105 40p ZTX652 60p 2A 100V 35p 74182 200p MOC3020 150p 70116 2N5485 36p 16A 100V 180p 74LS247 120p 22101 700p 6N137 400o BD139 40p MPSA06 30p ZTX752 70p 2A 400V 45p 74184 300p 4000 30p 22102 700p IL074 180p 2N5875 250p 16A 400V 220p 74LS248 120p 4001 30p BD140 40p MPSA12 50p 2N697 35p 2N5883 375p 3A 200V 60p 74185A 300p 40014 48p FN0357 120p BD189 60p C106D 45p 74190 140p 74LS249 120p 4002 30p MECEIM MAN72 140p MPSA13 50p 2N698 45p 2N6027 30p 3A 600V 72p 74LS251 100p 40085 90p 130232 60p MPSA20 50p 4A 100V MCR101 36p 74191 140p 4006 90p MAN74 140p 2N706A 36p 2N6052 300p 95p 130p 74LS253 100p 40097 60p 0.125' 80233 75p MPSA42 50p 2N708 36p 4A 400V 100p 2N3525 74192 140p 4007 30p 40098 60p TIL209 Red 10p MAN4640 200p 2N6059 325p 2N4444 180p 74LS256 2009 4008 90p BD235 85p MPSA43 50p 2N918 45p 2N6107 65p 6A 50V 80p 74193 140p 40100 120p TIL211 Gr 121p MAN8910 250p 2N5060 30p 74LS257A 120p 4009 60p BD241 60p MPSA56 30p 2N930 30p 2N6247 190p 6A 100V 100p 74194 149p 40101 120p TIL212 Tel 1510 TIC729 140p 2N5061 32p 74LS258A 100p BD242 60p MPSA70 50p 2N1131/2 50p 22N6254 6A 400V 120p 74195 100p 4010 60p 40102 140p TIC730 140p 130p 2N5064 35p 74LS259 200p BD379 60p MPSA93 40p 2N1613 36p 2N6290 10A 4000 2009 74196 1408 4011 30p 40103 170p NSB5881 570p 65p 74LS260 90p 4012 30p TIL220 Red 10p BD380 60p MPSUO6 63p 2N1711 36p 2SC1306 100p 25A 400V 400p 74197 140p 40104 1209 TIL311 800p BD677 40p 74198 74LS261 120p 4013 60p T1L222 Gr 12p TIL321/3 130p MPSU07 60p 2N2102 70p 2SC1307 150p 74LS266 100p BF244B 40p MPSU45 90p 74199 25Óp 4014 80p TIL228 Tel 151p TIL330 140p 2N2160 350p 2SC1957 90p DIL MUM 74LS273 240p 4015 80p Rectangular BF256B 50p MPSU65 78p 2N2219A 30p 2SC1969 150p 2.7V -33V 74221 7750/60 200p BF257/8 40p SWITCHES 74251 150p 74LS275 175p 4016 50p 74C92 LEDs IR,G,Y 30p Bargraph 225p TIP29A 35p 2N2222A 30p 2SC2028 80p 400mW 9p 74LS279 120p 4017 75p 74C926 £5 BF337 30p TIP29C 40p 2N2369A 30p 2SC2029 200p 4 -way 90p 1W 15p 74259 250p 8FR39 32p 74265 100p 74LS280 240p 4018 75p 74C928 £6 TIP30A 35p 2N2484 30p 2SC2076 160p 8 -way 120p MUM BFR40/1 32p 74273 270p 74LS283 120p 4019 60p 72168 £22 DL704 140p TIP30C 40p 2N2645 50p 2SC2335 200p 6 -way 105p 74LS290 110p 7020 90p 71,11040 670p 0L707 Red 140p BFR79 32p TIP31A 40p 2N2904/5 30 2SC2612 200p 10 -way 150p WW -5

PLEASE ADD 50p p&p & 15% VAT - TECHI'OMATIC LTD (Export: no VAT, p&p at Cost) MAIL ORDERS TO: 17 BURNLEY ROAD, LONDON N W 101ED Orders from Government Depts. & Colleges etc. welcome. SHOPS AT: 17 BURNLEY ROAD, N W 10 LONDON ®I Detailed Price List on request. (Tel: 01-4521500, 01-450 6597. Telex: 922800) Stock items are normally by return of post. 305 EDGWARE ROAD, LONDON W2 lI

ELECTRONICS & WIRELESS WORLD JULY 1984 5

www.americanradiohistory.com Two new TV books from Newnes Also available SERVICING DIGITAL CIRCUITS IN DOMESTIC VIDEOCASSETTE RECORDERS TV RECEIVERS A Servicing Guide R Fisher S Beeching Specifically for colour television engineers, this book is an This book takes the subject from basics and then shows in-depth guide to digital circuits used in current TV later modifications to the techniques, giving examples of receivers. The early chapters deal with digital techniques various manufacturers' approaches to the subject. Includes and their specific applications like teletext and videotex, VHS, Betamax, Grundig and Philips V2000 systems. their respective decoders being described in detail. Softcover 144 pages £14.95 Remote control systems, digital tuning and other digital circuits are also covered. A glossary of terms is included SERVICING MONOCHROME PORTABLE which will be useful to both engineers and students. TELEVISION Softcover 288 pages £13.95 G R Wilding This dual purpose book explains the circuity of current standard miniature and 'comb' monochrome portables, BEGINNER'S GUIDE TO COLOUR TELEVISION together with typical faults and probable causes, and Third Edition contains full size reprints of British, Japanese and Gordon J King revised E Trundle Continental manufacturers' circuit diagrams and service - information. Colour TV has been greatly developed since it was first introduced. This new edition has been re -written to Softcover 160 pages £13.95 include, as well as the basic introduction to the subject, an up to the minute account of such innovations as satellite COLOUR TELEVISION SERVICING and cable, flat panel receivers, 3-D displays and Second Edition "digitization" of TV signals. Gordon J King Softcover 192 pages £4.50 Softcover 350 pages £11.50

Order now from your Bookseller or direct from

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CIRCLE 37 FOR FURTHER DETAILS.

FED Jackfield Wiring FFD STEREO STABILIZER

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www.americanradiohistory.com COMMUNICATIONS COMMENTARY

and the Bethesda work on helical national security or relations with the loss of a valuable source of Hyperthermia coil applicators appears to be in the government of a country or information. As a result British progress the nature of a breakthrough. territory outside the UK'. Intelligence became very wary A number of British hospitals Sending of false or misleading of passing sigint even to the Much attention in recent years are involved in hyperthermia messages becomes an indictable Cabinet. has been focused on radiation experiments, some making use offence. DTI have the right to Today diplomatic traffic can hazards very close to high -power of obsolete 405 -line v.h.f. prescribe technical requirements be unconditionally secure (truly radio transmitters. Less notice television transmitters which can for services. random : one-time' keys) or more has been taken of the advances be modified for this type of work. It remains to be seen how often -`computationally secure' being made in the medical use of IBA have already donated several strictly the Courts will interpret requiring excessive computer r.f. heating by h.f., v.h.f. and Band III equipments to hospitals the amended Wireless time to crack. Clearly some of microwave transmitters, in Aberdeen, Bristol and Telegraphy Acts and the effort what can be plucked form the air particularly for hyperthermia Cambridge and have earmarked that will be put into enforcing can still be read, if only with treatment of malignant cancer further equipments for this them. On the face of it it would difficulty, or signals intelligence tumours. Although hospitals purpose when Band III seem to be an instrument capable would not have retained its have used heating by r.f. power television is finally phased out in of quickly putting off -air the importance. But the idea that (diathermy) for about 50 years, January 1985. broadcasting 'pirates' and the almost all diplomatic traffic can recent work has concentrated on more numerous pseudo- be read immediately on receipt the development of more Telecommunicati- amateurs such as the can serve only to encourage the effective coupling of the r.f. 'International C.B.' around Libyans (who know whether they power into the affected part of the ons Act 6.6MHz. Less easy to suppress sent such a message) and other body by means of improved will be the unlicensed 'amateurs' countries to change to more 'applicators'. The Telecommunications Act, and 'c.b.' operators who may still secure ciphers. A recent report from the 1984 received Royal Assent on find it possible to pass unnoticed The leak furthermore served Biomedical Engineering and 12 April, 1984 and Part VI - for a time by operating in no useful purpose. WPC Fletcher Instrumentation Branch of the provisions relating to wireless accordance with the licences they was already dead. If NSA or American National Institutes of telegraphy, incuding amendment have omitted to obtain. GCHQ are able to decipher such Health in Bethesda, Maryland, and enforcement of the Wireless It seems likely that con- messages virtually without dealy, notes that while hyperthermia Telegraphy Acts-will shortly cessions will be made soon to it may indeed have been offers promise as an adjuvant to become law. The new Act small-time broadcasters by the blame -worthy that a warning did cancer therapy, so far little appears to provide the DTI with introduction of some form of not reach the Metropolitan Police success has been achieved in the means of stamping out 'community radio' or 'special before the shooting. But finding a heating deep-seated tumours. A unauthorized and illegal use of event' radio licence involving for scapegoat is a doubtful advantage new design of helical coil transmitters of all types, example low -power transmitters if in the process a source is applicator has been developed provided always that sufficient at major outdoor and sports blown. which in tests under simulated effort is put into tracing them. events. This may however be Diplomatic radio conditions of the fat - Manufacturing, selling, deferred until the end of the communications form one of the muscle -bone of a human arm offering for sale or hire of second session of the ITU fixed services not entirely or thigh appears to be both 'restricted' apparatus becomes Regional Administrative transferred to satellite. A stroll practically and theoretically for the first time an offence. Conference at Geneva next though Belgravia or other capable of producing deep Having 'without reasonable October to December, when embassy districts of London heating (IEEE Trans 1984 excuse' such equipment in one's frequency assignments between reveals many h.f. aerials ranging vol.BME-31, pp.98-106, and custody or control, or importing 100-108MHz are expected to be from very large log-periodics to Electronics Letters, 1984, it, will also be an offence. agreed for the European region. the barely visible compact vol.20, April 12, pp.337-8). Manufacturing includes transmitting loop aerial on the Hyperthermia uses r.f. power to assembly of component parts. roof of the US embassy in raise the temperature of tumours Immediate seizure of Vienna Grosvenor Square . Diplomatic to around 43-45°C instead of the equipment under a search communicatons remain an normal body temperature of warrant becomes possible; if Convention important market forh.f. about 37°C. It has been known there is any doubt as to identity equipment. for over a century that some or address not even a warrant is The events during April Foreign embassies, however, malignant tumours respond to necessary. Where such seizure is surrounding the 'siege' of the do not have an automatic right to localized but small elevation of later confirmed by the Court, the Libyan People's Bureau were set up radio links. Paragraph 1 temperature. The difficulty has Secretary of State can, as at calculated to re-inforce the very of Article 27 of the Vienna been to heat the affected organ present, dispose of it as he thinks worst fears of signals intelligence Convention on Diplomatic without overheating other parts fit. people. The American ABS Relations, 1961 reads: 'The of the body. The Bethesda work The Act also makes pro- network started the ball rolling by receiving state shall permit and has used the industrial, scientific vision for payment of the radio claiming that Libyan messages to protect free communication on and medical frequencies of Interference Service from money London had been intercepted, the part of the mission for 13.56, 27.12 and 40.69MHz. provided by Parliament and deciphered but then not passed all official purposes. In Other workers have concentrated operational responsibility for this on to the police in time for them communicating with the on microwave hyperthermia on service will be transferred from to take greater precautions Government and the other 2450 and 915MHz despite its British Telecom to DTI. during the morning of April 17. missions and consulates of the limited depth of penetration of The Act abolishes the Such a 'leak' apparently from sending State, wherever roughly 1cm for loads of high advisory committee of the 1949 American sources, if true, must situated, the mission may water content, such as muscle, Act and strengthens the powers rank alongside the three classic employ all appropriate means, brain and organs. Design of of the licensing authority in a occasions in the 1920s when it including diplomatic couriers and applicators that can improve the number of ways including the was openly revealed in the messages in code or cipher. heating of tumours deep within ability at any time to revoke or British Parliament that Russian However the mission may install layers of fat or bone, with vary the terms of any diplomatic traffic was being read. and use a wireless transmitter minimum absorption of energy broadcasting or communications This led inevitably to the USSR only with the consent of the elsewhere has proved difficult licence 'in the interests of introducing secure ciphers and receiving State.'

ELECTRONICS & WIRELESS WORLD JULY 1984 7

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www.americanradiohistory.com COMMUNICATIONS COMMENTARY

signals with a transmitter power systems. A 96 -mile mechanical Syledis-type transmissions in CCD camera of 140 watts during tests between system being developed byJ.A. the 430MHz band is reported old Baird At NAB, RCA introduced a July 9 andJuly 13 when the moon Short uses the from California where pulse solid-state portable broadcast will be low enough on the horizon techniques of obtaining sync transmitters on 433 and 437MHz (20 to 24° at the meridian) to signals by blanking off part of the camera based on charged - have now been turned off. picture no blacker - coupled device sensors allow receiving stations to aim (i.e. aerials the need for than -black pulses) but and a 'frame transfer' process. their without uses a much more sophisticated Priced $37, 000 the camera is an elevation rotor. Further form of sync -separator claimed to provide a signal/noise information on these discriminator. Apparently it In brief ratio of 62dB with high experiments is to be distributed through French stations on works, which is more than could sensitivity and absence of smear A major solar flare, possibly the 144.170MHz 10kHz and 3670 always be said of the Baird on moving objects. C.c.d. ± largest in Solar Cycle 21, was 10kHz. phonic -wheel technique! cameras have been under ± recorded at the end of April .... Wayne Green, W2NSD, editor development for at least ten The RSGB 1984 National of 73 Magazine, in a petition for years, but many difficulties have Convention at NEC Birmingham Here and there rule -making submitted to the had to be overcome for attracted over 6000 people on FCC has proposed that all broadcast -quality units, and The Australian society, WIA, has Saturday 28 April and some 5000 American radio amateurs should studio cameras may still be some succeeded in persuading their on the Sunday. The 1985 be re-examined for morse way off. Largest exhibit at NAB Government to re-establish the Convention is to be held at the proficiency every two years with was mounted by Sony special low import tariff (2%) on National Exhibition Centre on 13 a requirement that they achieve a Corporation at a cost of over amateur transmitters and and 14 April 1985 ... A postage five word -per -minute up -grading $1 -million. They featured their transceivers. This concession stamp featuring the amateur each time, to a final level of 35 z in Betacam integrated was lost in June 1983 when an radio station, H44SI, of the word/min. Failure to improve camera/recorder and a complete Australian manufacturer of Solomon Island amateur radio speed, he suggests, should result high -definition system....NBC marine communications society was issued last December in loss of licence. However it have begun distributing network equipment complained that some as one of a set of three stamps seems highly unlikely that FCC programmes to 22 affiliate imported amateur radio forming a World Communications will impose such a rule. stations via satellite and plan to equipment had been modified Year set ... During earlyJune, increase this to 150 stations by and illegally sold for use in the French amateurs operated a early 1985... About 17 -million maritime service. The low import special station, TK6JUN, at Ste US homes (19% of tv homes) now tariff was granted on the basis Regioni Marie -du -Mont (Utah Beach) to have v.c.r. machines, still that there is no Australian mark the 6 June, 1944 D -Day significantly below UK production of amateur h.f. Conference landings by Allied forces. On this penetration. transceivers. side of the Channel, GB4BLC The Olympic Games torch run At the 1984 IARU Region 1 operated from the Royal British that starts on the East Coast of Conference held at Cefalu, Sicily, Legion centre at Nettley, the USA and will pass through all DrJohn Allaway, G3FKM, was Southampton as part of an Amateur the 48 contiguous States before it elected as secretary of the Region 'Operation Overlord' project Radio ends at the Los Angeles venue on 1 Executive Committee, the post during the D -Day anniversary July 28 is being co-ordinated by held until his death in 1981 by week ... RSGB annual amateur radio communicators Roy Stevens, G2BVN and since subscription is being increased travelling in the fleet of support then by Eric Godsmark, G5CO. by £2 to £ 16.50 from July 1 ... In Moonbounced vehicles, under the aegis of Region 1 conferences are held a recent prosecution for the AT&T. once every three years. At this illegal use of 6.6MHz TV? Several Australian amateurs year's conference,member- transmitter, Robert Burwell was Andrew Emmerson, G8PTH, has have been granted experimental societies were urged to fined £250 with £50 costs. It was passed along news from Maurice permits permitting transmission seek from their national stated that French air traffic Clot, F1FVX, of what promises on 196kHz (1830 meters) on adminstrations a 50MHz control had complained of to be a remarkable and unique condition that only 'backyard' amateur allocation and the interference to its operations experiment aimed at gaining a aerials are used. With output removal of Syledis pulse caused by the transmitter ... July 'world first' in amateur powers of about 100 watts and transmissions from the 430MHz mobile rallies include: Worcester television. French amateurs are fairly short aerials about 10m band. The conference also club at Droitwich High School, to attempt moonbounce of high, resulting in effective recommended that no f.m. Ombersley Road on July 1; West television signals transmitted on radiated powers of less than repeaters should operate Manchester club at Burtonwood 1255MHz using an aerial with a 0.5 -watt, telegraphy contacts are between 144.8 and 145MHz and Motorway Service Area near the calculated gain of the order of being made over distances of rejected proposals to allocate junction of M6 and M62 on 8 90dB! several hundred miles. channels and repeater channels July; Cornish club at Camborne To make this possible, the A successful meeting of Dutch for narrow -band f.m. Technical College, Pool on 15 French electricity authorities amateurs interested in transmissions in the 29MHz July; West Kent Radio and have granted permission for narrow -band mechanical band. It endorsed a provisional Electronics Fair at Royal Victoria F9CH and F6BGR to use the television was held last March in band -plan for 1296MHz and a Hall, Southborough on 21 July; 10,000 square -meter plane metal Eindhoven, attracting 50 to 60 new world-wide locator-squares Anglian rally at Stanway School, reflectors of the French visitors. Historic 30 -line system (fromJanuary 1, 1985). Colchester and McMichael rally experimental solar oven near equipment was displayed by Kees The IARU Medal was awarded to at Bells Hill, Stoke Poges both on Fontromue, East Pyrenees as an Sanders, PAoDXY. A camera the Russian amateur N. July 22; Rolls Royce rally at aerial, with a dipole element monitor by P. Wakker was made Kazansky, UA3AF. The Sports & Social Club, replacing the normal crucible and from small lenses taken from a conference also discussed the Barnoldswick and Scarborough with the computer programmed broken road sign and driven by a proposed new constitution for rally at The Spa, Scarborough to follow the moon instead of the bicyle dynamo. Several British the International Amateur Radio both on July 29 - sun. NBTV enthusiasts have been Union. It is planned to use using silicon solar cells as Rather more success in frequency -modulated vision pick-up devices for low -definition dealing with interference from Pat Hawker G3VA.

ELECTRONICS & WIRELESS WORLD JULY 1984 9

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www.americanradiohistory.com NEWS

well. Camputers, manufacturers Computer crashes of the Lynx computer which never really got off the ground, No less than three different that the bouancy of the home having sold only some 10 000 computer companies ceased computer market has been units, are also looking for a trading in one week: Dragon overestimated and that most buyer. Data, Tycom and Camputers. people who get home The business computer The chief executive of Tycom is computers do it purely and play market is now greatly influenced SirJohn Clark, Conservative games or because they are by the coming of the IBM Members of the European curious about computers. He is personal computer. Such large Parliament. His major customer looking for a buyer, and one may corporations can use their capital has been the Conservative be at hand. Tandy Corporation, and their marketing expertise to party, who have installed the whose Color Computer is very produce a machine that is easy to Microframe computer in a large similar internally to the Dragon mass produce, and can provide number of constituency offices. 32, has expressed an interest, full documentation and support The party is now looking for ways initially in taking over the in both hardware and software. to provide services and hardware servicing and repair of the The smaller companies such as support to those constituences. Dragon but possibly in Tycom find it difficult to compete Brian More of Dragon Data feels continuing the manufacture as with such powers.

system interrogates the key which responds only if the Software Key correct password is used. Any copy of the software will only A fresh attempt to counter home Microdeal will be adding the work on a computer fitted with software piracy has been key to several new programs on the same key and as there are launched by the Cornish their Tom Mix Software label. approximately 100 million company Microdeal, with the They hope to discover whether possible codes, made up out of inclusion of the protection device increased sales to frustrated ASCII control characters, in with one of their latest computer pirates will outweigh those lost to effect this means only one games. schoolchildren who might computer can use it. Each device Buzzard Bait, a game for the otherwise have bought the game is supplied with a randomly Dragon 32, comes with a small by pooling their pocket -money. selected code, together with resin -encapsulated module Also fitting in to the RS232 notes and a flow -chart on how to which plugs into one of the port of a computer is the Sesame incorporate the interrogation computer's joystick ports. This security key from Polytech routine into a program. It has software key, as Microdeal call it, Engineering Services Ltd. been estimated that it would take must be in place to enable the Without inhibiting the use of the a fast computer about 20 years to cassette to load properly. The port, any software used with the 'crack' the code. WW230 company hopes the device will put an end to unauthoried tape -to-tape copying, since without it the cassette is useless. Cell news And Microdeal believe that copying the module itself would Trials for Racal's cellular to be manufactured in Japan by call for resources beyond those of radio -telephone system, to be NEC. After a world-wide search the home user. The key, or dongle, known as Vodafone, are to start for a manufacturer to these was developed to Microdeal's in December 1984, ahead of the products, BT decided that NEC specification by Northern Software original schedule, over a 150 were the only people with the Consultants of Newcastle -upon square -mile area of London. The facilities and expertise to provide -Tyne. It costs about £2, service will also start up before the system. The equipment will its of March 1985, and can be applied to cassette or schedule date include both car -mounted mobile initially covering London, cities disc programs for almost any radiophones and hand-held microcomputer. For business in the south, Wales and the portables. The mobile sets will midlands, and along several be available in computers, a version can be December this motorways. The second phase is made to interface with an year with the portables following P` to be an expansion into the north later in 1985. If the cellular RS232 port. A different ,,R``` of England - plans for Scotland system is as successful and "\ key is required for each and Northern Ireland StG title. are to be popular as both BT and NEC announced later this year. Racal think it will be then there is a have also launched a new chance of manufacturing company, Racal-Vodac, to facilities being transferred to the distribute, install and service UK. The first working pilot subscriber equipment. Another system of Cellnet was to be company was necessary as the demonstrated in London early in licencee for the system is not June to cover 3 000 square miles permitted under the terms of the and give continuous coverage licence from marketing the over central London, extending consumer equipment. to Heathrow and Gatwick Consumer equipment for the Airports. BT/Securicor Cellnet system is ELECTRONICS & WIRELESS WORLD JULY 1984

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Uosat 2 not dead but poorly One network nottwo in UK Uosat-2, the Surrey University Britain is urged not to follow the telephone network is neither should offer a common carrier satellite which ceased to American example and have designed for local transmission of service only and lease capacity transmit beacon signals after the separate telephone and tv high-speed data nor tv pictures; for tv channels or other services first three orbits, has now been networks. In an article in the the other, a cable tv system is not to programming and marketing traced. (Communications Sunday Times of June 4th, designed to provide telephone companies. Control of such Commentary, last month) The Warren Partridge an American services. Both systems suffer entertainment channels could be giant SRI dish in Greenland lawyer and telecommunications from not getting the income that through the proposed cable managed to detect the 1.2GHz business consultant, points out could accrue from the services authority. local oscillator which pin -pointed that with the denationalization of provided by the other. These proposals would the exact orbit of the craft. British Telecom, Britain is Mr Partridge suggests that counter the problems found in Surrey engineers were gratified heading toward the same system Britain's cable tv franchising the US, where it has been found to have confirmed that the that the US has developed in the process could be used as the that cable tv only provides more satellite was where they expected 70s: one that has a private mechanism for privatizing BT. channels and if those channels it to be. They managed to turn on telephone monopoly, Britain could be divided into a are also available over the air the 2MHz beacon to discover that underfunded cable tv and few large combined telephone then the cable systems begin to the satellite was undergoing a unnecessary investment in all and cable services. The condition founder. Only in Washington DC weekly temperature cycle and sorts of services to be carried into attached to awarding a franchise has the telephone company that there were major problems homes on several wires. Now is should be the aquisition of BTs proposed that they provide the with the 2MHz beacon system. the time, he maintains, for all present telephone system assets. cable system to be leased to cable Now they have managed to these services to be combined This would privatize BT tv companies. That should be the bypass the problem by using the into one network. geographically, piece by piece, way forward for Britain, says Mr on -board computer and have The American experience is with the licensee operating a Partridge, if it wants to learn been able to send commands on the development of two separate, single system for telephones and from US mistakes and take its the command uplink. It is still and inadequate, systems. The tv. Those awarded franchises telecoms into the futue. necessary to stabilize the craft to prevent the temperature cycling and to get the main antenna pointing earthwards. Then it will be possible to have a complete Communications in the air system check-out and find out how many of Uosat-2's functions British Telecom persuaded numbers are stored and dialled The system combines are still working. Even if British Caledonian to run part of automatically), and send or 'sophisticated features and high everything else functions its Gatwick operation from receive telexes. The link from reliability, at an extremely propertly, it will not all be able to Birmingham at Communications Gatwick to Birmingham was for competitive price. ADEKS was be used because of the use of the 84. They did this to demonstrate two of the 12 terminals in use at designed specifically for computer to bypass the 2MHz the capabilities of Touchdown, a Gatwick. installations such as this and is problems. communications link between Another communications the result of cooperation between the aircraft, controllers and system, installed by BT at BT and CAA communications groundstaff which allows for the Gatwick, is for the air traffic engineers.' OED on computer arrangement of schedules for controllers. Through ADEKS, ADEKS keyboards are small The compilers of the new edition re -fuelling and repairs, check Advanced Design Electronic Key units incorporated into the air of the Oxford English Dictionary destination and arrival times, System, allows controllers to get traffic controller's desks. At the have decided to commit it to a book crews and aircraft, check in instant touch with other touch of a button users have computer. This will enable the passenger loads and the controllers and with telephone instant access to all kinds of original 13 volumes to be provision of on -flight catering. lines. Mike Morris, a director of internal, public and emergency expanded by the four supplement All this is done from a BT National Networks, telephone lines. Incoming calls volumes and any new words can touch -screen terminal. By expressed his pleasure at are indicated according to their be easily inserted right up to the touching squares on the screen receiving the order from the Civil priority. moment that the edition is operators can answer incoming Aviation Authority. He hoped The control system is prepared for printing. There are calls, call up background that similar organizations in designed to minimize disruptions over half -a-million entries which information, make internal and other countries would follow suit. and uses multiple processors and include over two million external calls (all regular back-up cable routes to ensure illustrative quotations giving a high integrity. Any components total of over 80 million failure can effect a maximum of characters. In addition there is a one console or two lines . variety of typefaces including Expanding American teletext Self -checking routines and Greek, phonetic characters, National Association of submission, the NAB said that battery back-up are also mathematical symbols and Broadcasters has joined the FCC the system was technically provided. Cables are smoke and scientific formulae. in its proposals to authorise sound, promoted competition fire resistant and special The system is to be based American tv stations to provide and conductive to spectrum immunity to radar and radio around an IBM 4341 central paging and a variety of data efficiency. It also said that the interference has been built in. processor with both tape and disc transmission services in the tv services should not be subject to One system can handle up to 116 storage, printers and over 20 signal vertical blanking interval. common carrier regulation. lines to 60 consoles and systems v. d. us. Under IBM's scheme for The services should include Cable services which are obliged may be linked for larger support for academic institutions video games and computer to carry certain network services installations. ADEKS can also be they are sending two programs, and other 'interactive' should not be permitted to 'strip' interfaced to radio circuits. data-processing specialists to the services. The decision to provide the new offerings from the tv ADEKS is installed in the new OUP to assist the dictionary these services should be left to signals. stalk -mounted control tower at editors with the task of updating. the market place. In its Gatwick. 14 ELECTRONICS & WIRELESS WORLD JULY 1984

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6996 1.30 129X7 1.60 6085 14 00 92426 28 50 972 2.50 293375 9.20 2SC1120 12.50 25C2290 27 50 M6F428 57 00 501019 20 10 AH205 708.00 PCL805 1.85 69W99 2.65 12487WÁ 4.80 60949 420.00 263553 2.00 2SC1121 24.00 2SC2347 030 M8F4289 75.00 5010195 2470 442114. 85 00 P1509 5.50 6928 3.80 12644 2.90 6101 2.20 293632 10.00 2501122 18.00 2SC2369 2.00 MRF433 16 21 501020 1 50 911221 48.00 P1519 5.75 8898 1.60 12896 2.00 6130 24.50 2N3733 13.20 26C11628 0.90 25C23709 1800 M11F4494 14.95 501074 16.10 911238 35.00 19.50 66484 2.75 121397 3.00 61469 7.30 00002.6 293886 0.85 2501185 8.95 2SC2379 15 00 190450 11 90 501076 18 50 992511 9000 00003.10 5.50 68E6 190 128E6 190 61468 7.50 293926 11.26 25C1169 4.85 2SC2395 15.00 196F453 .'1400 501077 1 60 *112532 31 50 00007.50 12.00 61306 2.00 126M7Á 2.50 6155 49.00 293927 11.82 2901176 14.00 25C2407 1 00 M6F453* 14.00 501076 26 50 4.50 6SJ6 1.65 12607* 2.65 6156 59.00 4J2256 7.50 0003-12 294416 0.75 2901177 17.25 2SC2420 18.00 19147454 21 00 501080 1.55 68K4C 4.15 126Z6 3.70 61596 '12.50 80512A 31.50 003'65 52.50 294427 0.75 2001179 18.00 2502494 16.00 MRF454* 24 00 501060.6 7 50 6086 90 00 49.00 61316 68.50 12006 1 50 6201 6.50 073-125 295090 13.90 25012090 0.64 2SC2509 6 00 MRF455 16.00 $01080.7 7 50 3.80 12DW7 4.25 12.95 BK448 11000 074250 59.00 66L7019 6227 295109 2.00 2SC1213* 0.40 25C2531 130 19117455* 2100 S01088 2600 66402 485.00 81169 80.00 613L8 1.45 12E1 25.00 6267 7 75 295160 4.80 2SC1213C 040 25C2538 1 10 M6F458 19 95 501089 28 50 93.95 12708 14.00 86484 144 00 RG3-1250 35.00 61346 12.00 6293 295190 1.50 25C1239 2.50 2502539 15.00 1997466 24 50 501098 40 10 613148 1.50 120979 4.00 63609 5.50 86486 375 00 893.2509 15.50 2N5589 6.00 2SC1241 15.00 2SC2540 24 95 MRF472 4 40 $01115.2 7.50 864884 525.00 RG4-1250 48.00 8896 2.45 120791 1.80 6426 1690.00 295590 8.50 2SC1251 10.00 25C25456 0 29 MRF475 200 901115.7 2 10 807703 25000 804.3000 90.00 6805 1.60 125170T 3.95 6442 1600 2N5591 8.90 2SC1260 1.11 87890 1 50 1467475 2 25 $01127 2 50 320 00 114126 1360.00 6698* 2.95 13E1 155.00 42.11 911119 6484 265643 13.00 2SC1303 5.00 137891 200 MRF477 12 50 501131 3 25 BT5 51.50 1913-250 15.00 61306 1.35 21326 3.40 6528 48.00 295913 2.50 2SC1306 1 00 87996 200 MRF492 27 50 501133 9 50 8750 51 50 693.1250 34.50 6526 2.50 30606 5.00 65509 7.25 295945 8.95 2501307 1 50 67790 1 50 1467497 18 50 5131133.1 10 00 8117 15200 5P41 3.80 6C4 1.05 40KG6 5-50 8688 8.50 295946 1563 2501311 040 BLW29 1000 MRF515 390 501134.1 250 8717* 142.00 $56.13 1200 6C94 1.65 *00G6* 5.75 6689 9.25 266080 600 25C1311E 0.32 BLW60C 1500 1467517 350 $011342 1000 3.50 42E04 BT19 38.00 71601 2950 6C97 4.00 6693 90.00 296081 8.75 2SC1314 25.00 BLW60CF 1500 MRF620 1800 501134.8 1000 60889 1.90 75C1 6779 8169 295.00 12889406 589.00 2.80 1950 296082 9.00 2501318 0.40 51W64C3 65 00 M6F644 27 50 501134.5700 760 6CF6 1.90 133Á1 BT95 129.90 1/325/300 112.00 12.00 8856 52.50 296003 1200 25C13686 1.00 1316/70 6180 MRF646 28.00 501135 10.25 6C07 2.25 90C1 131125 72.50 T15-500 225 00 3.50 6857 66.80 296084 13.20 2SC13838 0.50 81W80 10 25 M8F648 33 00 551135.3 1200 131127 95 00 6C66 9.95 90CG 12.00 6858 99.20 UU5 25.00 296094 8.00 25C1424 1 35 6LW01 14.90 MRF750 6 50 $01136 12 50 90CV CIK 20.00 815631 14.50 6CJ3 2.30 14.20 6859 103.50 2N6095 8.50 25C1509 6.00 BLW90 1300 M6F846 4600 $01143 945 22.50 VR75 6CJ6 10.95 150132 8 50 88638 14.20 C3J 5.45 298255 3.45 2501546 0.45 BLW90 110.00 MRF901 2 75 501143.1 10.00 C3JA 28.80 4 95 OCK6 8.00 150C2 3 10 6922 3.90 89150 2SC382 0.65 2SC1568 0.45 91639 13 75 M6F904 2 95 $01144 1 3 50 OGLE. 3.30 150C3 4.95 6939 19.50 C3JL 30.00 6C12 130 2SC458 0 22 25C1589 5 00 81065 2.45 MRF911 2 50 $01158 7 95 C16J 120.00 60M5 2.30 15004 4.50 6973 3.70 001.2500 51 50 2504588 0.36 2SC1622 0.33 BLX67C 9 50 MRF5175 22 50 S01201 7 35 OCHE 4.95 212E 170.00 C61907 17.70 002.500 36.00 6975 66.00 25C450C 022 2SC1623 0.30 BLX67CF 950 MRF5176 30 00 $01202 7 50 C65687W* 4.10 002.6400 152.00 6C06 2.20 290A 7150.00 7014 44.50 25C460 0.25 2SC1688 19.80 6166803 1000 M9F5177 4300 5012174 6D0 6CW4 8.50 3509 50.00 01516 18.00 005'500 24.50 22.50 7015 2SC460B 0 25 2SC1674 0.25 BLX68CF 10 50 M6F8004 700 S017127 0 00 004 31.50 961.18009 29.50 6CW5 1.95 3506 2250 7017 66.50 2SC4618 0.25 2SC1875 0.20 614694 2000 P13134A 1 50 501214 070 062010 4.80 72 6CY8 3.80 4049 1200 7018 78.50 2SC535 891.3200 50 0 36 25C1678 1 25 1316949 36.00 P131348 2 75 $01716 11 00 062100 7.50 861.6400 95.00 8CY7 300 5728 29.50 7022 66.80 25C535Á 0 38 2501729 18.00 91098 132.00 PT3134C 12.00 $01219 16 00 062110 9.00 76026 69 40 6C25 3 15 5754 35.00 7023 103.50 25053513 0.38 25C1 730 0.25 131187C 7 50 P131340 12 501219.4 18 00 2.30 50 0151 1.85 Z803U 19.50 6096 615 18.50 7025 2.50 3SC535C 0.35 25C17400 0.20 61768C 1100 PT3134E 3000 5012201 950 ESSI 44.00 271011 29.50 13006 2.45 710 29.90 7027 4.60 25C540 24.95 2501765 7.75 BLY88CF 11.00 P131619 1 75 5012225 11.00 6DC8 , 150 EBOCC 40.00 20100551 13.50 7401 66.80 7034 42.50 2SC608 075 2SC18157 0.28 BLY89C 1300 P131619 175 5121222'STUO 1100 E80F 13.10 291000 18 15 60J8 1 70 760P 103 50 7056 2.50 2SC6*4 0.25 2SC1908 0.33 BLY90 45 00 P73161C 8 50 5131224.2 13 00 E601 12.95 Z911001 1815 6066 3.95 805 7136 175.00 4200 2SC684 0.28 2501907 0.30 BLY91CF II 00 P131610 14.00 S01229 -F1 1095 2141020 15.65 6015 230 E81CC 3.20 807 2.90 7189A 2.40 250703 36.00 2501945 2.10 131194 45.00 PT3161F 30.00 5131229 -STUD 1095 E88CC 3.90 092 3 10 6136148 2 30 810 7199 4.20 2SC710 50.00 0 45 2501946 19.75 MRF208 1200 P13503 6 95 5017448 12 75 089F 9.25 0*2WÁ 5.50 8E5 4.20 611A 14.90 7203 1941) 39.50 2507100 0 28 25C19469 16 50 MRF212 12 00 P14261* 16.00 5012S6 6 95 093 5.45 6EÁ8 2.45 8129 E90CC 8.50 19.90 7203 1E1911 49.00 2507150 0.40 2501947 6.88 19RF221 12.05 P142618 24 00 S01762 15 00 E92CC 6.50 062 3 95 6E15 1 85 813 7233 6.75 19*11 28,50 2SC715E 0.40 25C1955 7.20 M6F229 3.50 P14261C 60.00 501270 3 75 2.00 01301 23.50 062WÁ 5.95 6E117 813 'RCA) 65.00 7234 7200 2SC717P 0.38 2501966 11.00 MRF231 12.36 PT4316C 12.00 501272 1095 2.00 0180F 8.50 053 2.50 60J7 82913 1720 7247 3.20 25C730 410 25C1967 15.00 MRF232 13.50 P143160 18.00 S01272'2 1095 0C3 2 50 6014* 4 15 8339 SO E168CC 7.50 61 7289 39.00 25C731 3.95 25C1968 17.50 MRF233 14.30 P143160 25.00 $01278 13 75 05070 OD3 4 95 6E58 2 10 843 10.00 27.50 7308 7.50 250732 0.25 25C1988Á 22.00 MRF234 16 00 PT4316F 30.00 501278.1 13 75 18249 100.00 6007 2.85 805 0691 1.95 48.30 7322 604.00 2SC741 2.50 2501969 3.05 1913F237 3.10 PT5681C 14.00 501285 1275 EBC91 1.30 16359 38.00 6E196 1 50 8578 70800 7360 9.00 2$0821 6.60 2501970 1.50 1460238 12.80 P18751 2400 501300 1 25 01F89 150 18639 62 00 6F06 2.00 886A 15 SO 7486AL 80.00 2508289 0.30 25C1971 400 11113F239 20.00 P18620 1570 501303 2 50 EC90 1 BS 113839 Sß.00 0E118 18.50 BBB 24.00 7527 73.30 2508298 0.25 25C1972 11 00 497240 24.50 018631 2 75 501 316 2 10 1P21 ECC32 250 104.50 6707 2.25 872* 19.00 75279 140.00 2SC890 8 S 25C1978 7.50 MRF243 35.00 P18837 10.00 501317 800 11.28 6FS5 922 12.50 ECC40 2.95 3000 225 7534 23.50 250091 18.00 2SC2001 045 416F245 3000 P18638 15.00 501405 2100 ECC70 3 70 2115159 21 10 6095 2.80 927 17.80 7543 2.00 250900 0.18 25C2020 0 75 9119F247 30 10 P188548 18.00 501407 27 50 ECC81 60 2C399 4800 60E5 290 930 14.70 7551 5.50 2SC900F 0.19 2SC2053 0.80 MRF260 5.00 PT8861* 5500 210 15.00 50140719P ECC82 60 2C39169 39.90 60E5 9319 18.50 7558 9.50 2SC908 4.50 2SC2097 36.00 M6F264 1100 P158649 30.00 501410 2106 2021 2.80 60789 1.80 9316 ECC83 60 2500 75819 18.25 250911* 18.00 25C2099 15 00 M6F309 42 00 PTB674 18.00 501410.1 21 00 2E16 7.50 00J5* 3.00 934 16.80 11.50 ECC85 20 7586 2SC945 0.21 2502100 24.00 MRF316 55.00 PT9795 12.50 3014103 21 00 ECC86 70 2242 95 50 60J1 1.85 935 35.80 7587 19.00 2509458 0.21 2502103 18.00 MRF317 73 00 P19797 14 50 501412 36.00 ECC91 00 2255 22500 6066 1 95 10510 110.00 75919 5.00 250952 0.60 25C2105 15.00 MRF321 35.00 P19641 16 00 $01412.3 24 00 2025 11400 6GW6 1.70 10526 77238E ECC169 10 144-00 2065 2SC982 030 25C2116 180 MRF323 35.00 P19847 16.00 501413 1800 ECF80 45 3.400Z 82 00 6006 300 2050 2 85 781541 GE 48.00 25C994 2 50 2502118 9.00 MRF326 63 00 501005 8 20 501414 36 00 ECF86 .50 3'5002 79 50 60713 3 00 20509 2 85 76158 AL 48.00 23C998 3.90 2SC2221 5.50 919F327 70.00 $01008 2 10 $01416 33 00 806 3.00 ECF601 85 3826 1500 4532U 250.00 7868 4.20 250,001 9.90 25C2233 0.90 M8F329 5806 501012-3 1000 $01418 3000 EC681 6098 3.05 48332 7903 115.00 50 38522 300 215.00 2SC1011 15.00 25C2737 16.00 M#F412 18.51 501012.4 10.50 $01421 36 00 EC162 38642 3 00 6066 3 05 48752 7905 13.50 50 215.00 2SC1070 1.15 2502281 13 00 MRF421 36 85 501013 10.00 501428 24 00 00E5 4.00 5517 14.50 13.50 ECL83 50 3C23 2375 7984 2SC10961. 0.90 2502283 900 MRF422 42.00 5010146 1050 $01429 1598 ECIOS 70 3C45 24.50 6HF5 3 85 5544 72.50 8008 10.90 25C109651 0.90 2SC2287 11 00 MRF426 23.00 $01015 17 50 61-1G5 195 EF40 50 3C610095 39.00 5545 95.00 8020 35.00 2SC1117 1.50 2SC2289 1250 MR7427* 2100 5010186 1300 EFBO 35 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www.americanradiohistory.com DIGITAL AUDIO

by E. H. Digital stereophony Hartwell BBC Research with television Department

Tests on digital four -phase d.p.s.k. technique of transmitting additional sound information for tv stereophoney show the system to be more rugged than for either teletext or colour television pictures.

Ted Hartwell joined the BBC A single high -quality broadcast A system has been devised quency which could lead to sim- in 1963 after serving four based audio channel requires a band- on earlier work at the BBC plification of the decoder, and it years as a design and width of at least 15kHz. Simple Research Department' and its provides a few kbit/s spare data development engineer in linear quantization of an audio outline parameters are given in capacity for supplementary pur- industry. Most of his time in signal requires at least 13 bits per Table 1. The proposed system, poses. the BBC has been spent in the sample for acceptable broadcast which is still under development, studio engineering quality. Near -instantaneous digi- was not used in the South Wales department at the Television tal companding*, however, tests, a pseudo -random binary Choice of modulation techniques Centre in West London where enables the number of transmit- sequence generator being used he worked as an engineer and, ted bits per sample to be reduced instead. However, the important The choice of a modulation tech- more recently, as a technical to ten with negligible degradation factor was to test the modulation nique for any digital transmission writer. He became Research in quality. Assuming a 15kHz system employed and this is dis- system results from a compro- Author at the BBC's Research audio bandwidth, a sampling rate cussed next. The proposed sys- mise between the required band- Department last year. of about 32kHz is required to tem employs a bit -rate of width, the signal-to-noise ratio satisfy the Nyquist criterion** 704kbit/s, chosen because it is a required to achieve an acceptably and thus avoid unwanted alias multiple (22) of the sampling fre- low received bit -error rate (this Table 1. Proposed baseband coding effects. The minimum bit -rate for experimental digital stereo sound with terrestrial television. for a single high -quality audio channel is therefore about Audio bandwidth 15kHz 320kbit/s. To this must be added the bit -rate needed to transmit Pre -emphasis CCITT additional data such as framing Audio sampling rate words, parity bits for error detec- 32kHz tion, and the scale factor words Samples per block 32 associated with near -instantane- ous companding. Two such chan- Audio coding 14/10 -bit near -in- nels, therefore require a bit -rate stantane- of something in excess of ous comm- 640kbit/s. panding 640kbit/s *In near -instantaneous digital companding the analogue input signal is sampled and Scale factor bits 3 per block digitally coded to an accuracy of 14 bits per per Chan- sample. Only ten of these 14 bits are actu- nel 6kbit/s ally transmitted, the ten -bit 'window' mov- ing up and down the 14 -bit range according to the peak signal level occurring during a Error protection 32kbit/s block of 32 samples. The receiver decoder for sample words is instructed on the correct placement of the 'window' by a three -bit scale factor Error protection for 4kbit/s word sent with each successive 32 -sample scale factor bits block. By this method, low-level pro- gramme signals are transmitted with 14 -bit Framing accuracy. 1'he accuracy progressively 8kbit/s decreases down to ten bits per sample for the higher signal levels, but the conse- Available for further 14kbit/s quently increased quantization noise is development masked by the higher level of programme. * *The sampling frequency must be at least Receiving, demodulating and measuring equipment inside a Overall bit rate 704kbit/s twice the highest modulating frequency. BBC survey vehicle. ELECTRONICS & WIRELESS WORLD JULY 1984 17

www.americanradiohistory.com DIGITAL AUDIO

already been gained in the use of channel is kept to a minimum. Input Amount by which this method. The frequency bit pair carrier changes phase and level of the Four -phase p.s.k. is a digital second sound carrier must also be

00 0° i e no change modulation technique in which chosen so that the digital system 01 -90° the carrier adopts one of four pos- works reliably throughout the 11 180° sible phase states dependent on service area of normal television 10 -270° the two-bit pattern occurring at reception. A third requirement is any instant, i.e. 00, 01, 11 and that the second sound carrier (a) 10. Carrier amplitude remains must not interfer with transmit- constant except during phase ters operating on adjacent televi- transitions. sion channels. The first and third Simple four -phase p.s.k. requirements have been investi- requires the transmission of an gated in the laboratory, and the additional phase reference signal second during the field tests in for correct decoding and this can South Wales. Inevitably, these only be achieved at the expense of requirements conflict and a com-

4 2 increased carrier power or band- promise has had to be sought. width, neither of which is desir- Theory and laboratory tests able. However, if the p.s.k. sig- indicate that, to avoid interfer- nal is differentially coded ence to or from the main fre- (d.p.s.k.), no additional infor- quency -modulated sound signal, 3 mation is required. Instead, the the additional digitally -modu- Rest states of carrier phase 90°apart transmitted message is coded lated sound carrier woudl need to roi into carrier phase changes be spaces 6.5MHz or more above between one bit pair and the next, the vision carier (i.e. 0.5MHz which the decoder does not need above the rest frequency of the a phase reference to detect, main sound signal), and at an Input bit -stream (bit pairs) 00 10 11 01 Fig.1. Briefly, the modulation amplitude of between 20 to 25dB system works as follows. below it.* This is a larger fre- The changes of carrier phase quency spacing than that used in Transmitted which correspond to the four pos- the earlier BBC tests on the ana- phase -changes 0° -270° 180° -90° sible bit pairs 00, 01, 11 and 10 are logue two -carrier system, where *The carrier phase respectively 0, -90, 180 and a spacing of about 6.3MHz was is assumed to be -270°, Fig.1(a). The carrier best, because of the greater band- Rest states of* initially in rest state 1 carrier phase 4 2-1.3 phase itself can dwell in one of width (about 700kHz) of the dig- (c) four rest states 90° apart, as itally modulated signal compared in (b). An input bit -pair of FIG 1 depicted with that the f.m. signal. shifts the carrier phase into a dif- The upper limit on the spacing Fig.1. In the differential coding usually determines the carrier ferent rest state by the amount of the second camer from the process four bit -pair combin- power required), and cost. The assigned to that particular pair. vision carier was determined by ations which modulate the car- last item is particularly important The transmitted phase changes adjacent -channel interference, rier cause it to change phase by here because it is highly desirable the amount shown in the table and subsequent carrier rest states both from the viewpoint of inter- (a). Carrier has four possible to minimize the cost of the dec- for the input bit -pair sequence ference from the digitally modu- in rests state 90 apart (b). An oder required domestic receiv- 00, 10, 11 and 01 are illustrated in lated signal into the vestigial side - example of carrier rest states ers. (c). band of the upper adjacent chan- adopted for the input bit -pair The broad family of four - nel, and vice versa. sequence 00, 10,11 and 01 is phase -shift keying systems offers Choice of second sound carrier Laboratory tests indicate that shown in (c). the best compromise between with the second sound carrier at a the requirements above, and a The relative levels of the vision level of 20dB below the vision particular variant known as four - and sound carriers, and the fre- camer level, interference from phase differential or quadrature quency -spacing between the the digitally modulated second phase shift keying was chosen for main and second sound carriers, sound carrier into the upper adja- the experimental system. Four - have to be chosen to give good cent channel is not a problem and phase d.p.s.k. had been success- compatibility with existing complies with the CCIR recom- fully used by the BBC in earlier receivers, whereby interference mended protection ratio. In fact contexts' so experience had to the picture or main sound the main sound carrier is the limiting factor for interference Table 2. Modulation system for experimental digital into the upper adjacent channel; stereo sound with terrestrial television. this remains true even when the main sound carrier is reduced by Frequency of second 6.55MHz 3 to 10dB below the vision car- sound carrier above vision carrier rier. Interference from the upper Level of second sound -20dB with respect to peak adjacent channel into the digital carrier vision carrier sound channel seems more likely because the CCIR recommended Modulation of the 4-phased.p.s.k. second sound carrier at704kbit/s protection ratio in this direction is much more tolerant. Overall bandwidth (to -30dB) 700kHz Any interference to the digital of transmitted d.p.s.k. signal sound channel from the vestigal Level of main -10dB with respect to sidebands of the upper adjacent sound carrier peak vision carrier channel vision signal is picture dependent, which meant detailed 18 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com studies of the power -density adequately resistant to impair- Main spectrum with a variety of picture ments to digital sound signal sound cornerier signals. As expected from the reception arising from low field centre frequency Vision carrier vestigial sideband shaping, the strength, multipath propagation, frequency Proposed second power density spectrum falling ignition interference, and distor- sound carrier frequency into the digital channel is triangu- tions in a long chain of transpos- lar, power -density decreasing ers. with increasing spacing from the The results clearly show that interfering vision carrier. This when receiving low field -strength indicates that the frequency of the signals directly from the main carrier should De second sound transmitter (at Wenvoe) the digi- i 3 4 kept as close as possible to that of tal sound signal wilt not, on aver- MHz its parent vision carrier. fail before the picture tef 25tF 6 55 MHz age, MHz These conflicting require- became unacceptably noisy; 8 MHz channel -.a ments lead to a frequency spacing when receiving signals via a red - for the digital sound channel of broadcast relay station (trans- 6.55MHz above the wanted poser) the average failure point confirm that the experimental Fig.2. Frequency bands occup- vision carrier, i.e. 0.55MHz occurring at a field strength well system is compatible with the ied by the colour picture com- above the main f.m. sound car- below the nominal service area widest possible range of domestic ponents and sound signal of rier, Fig.2. limits for Band IV and V transmis- receivers. In May, test transmis- one television channel with the of Parameters the modulation sions. The system is more rugged were made of a television proposed digital sound signal sions added. system adopted fo the experi- than either colour television pic- programme with stereophonic mental equipment are given in tures or teletext with regard to sound using the experimental Table 2. multipath propagation effects system described. The results of (ghosting). both series of tests are very Conclusions In March, with Home Office encouraging; the BBC is pres- agreement, the BBC conducted ently having discussions with the The South Wales tests show that similar tests from the BBC2 IBA and the receiver industry to the experimental digital system is transmitter at Crystal Palace, to establish an agreed UK Standard.

Background to BBC experiments

For many years there has been tibility tests of this variant from ence between the main sound interest in the possibility of add- the BBC transmitter at Crystal carrier and the added digitally- ing stereophonic sound to exist- Palace outside normal broadcast- modulated carrier. Also, because ing television services and the ing hours. The tests indicated of the more noise -like nature of a BBC has investigated a number of that the system was only margi- digital signal, the visibility of any possible methods. In all cases an nally compatible; interference interference patterns is reduced additional sound signal is between the additional sound car- further, which enables the main required to carry the stereo infor- rier and the main sound carrier sound carrier to be maintained at mation and, in some cases, the gave rise to picture patterning, or near its full level, avoiding the additional signal is suitable for which, to avoid, required reduc- increased buzz -on -sound prob- the transmission of two inde- tion of the main sound carrier. lem found with the analogue two - pendent sound signals as may be However, reduction of the main carrier system. required, for example, to provide sound carier to 13d13 below the A thorough investigation of a bilingual service. Methods vision carrier as in Germany the digital option carried out at investigated include the pilot. caused increased buzz -on -sound the Research Department led to tone system as used for stereo in some existing receivers. over-air tests of an experimental radio broadcasting in the UK, the During the period that various system, conducted outside nor- Japanese f.m.-f.m. system and options for analogue stereo sound mal broadcasting hours from the the German two -carrier system, with television were being BBC2 transmitter at Wenvoe in all of which employ an analogue assessed, the status of digital South Wales and its associated second sound signal; and digital techniques in domestic equip- rebroadcast relay stations during sound similar to that proposed for ment had changed considerably the autumn of 1983 [ref .1]. This direct broadcasting by satellite and consumer products, such as particular area was chosen television. the digital audio disc with its because the terrain is hilly and References The first two methods have attendant high quality sound, had multipath propagation of normal 1. S.K. Ely. 1983. Experimental Digital certain limitations in this context become available. Also, the BBC television signals very evident. Stereo Sound with Terrestrial Televison : field-test from Wenvoe, October, 1983. and were not pursued as serious proposes using an internationally The area contains a large concen- BBC Research Department Report contenders. The German agreed system of digitally coded tration of rebroadcast relay RD 1983/ 19. 2. D.F. Reid and N.H.C. Gilchrist. 1977. method, (WW November 1981, sound for d.b.s. These advances stations which enabled assess- Experimental 704kbit/s Multiplex Equip- Page 40) in use on a limited basis led to the consideration of a dig- ment of the digital sound signal ment for two 15kHz Sound Channels. BBC in that country, appeared more itally modulated second sound when subjected to the cumulative Research Department Report RD1977/38. 3. M. J. }Callaway. 1976. Experimental promising and engineers at the carrier to convey the stereo sig- effects of distortions in a long Four -phase Differential -phase -shift - BBC Research Department nal. chain of such stations. keying System to carry two High -quality Digital Sound Signals. BBC Research devised a variant of this method A digitally-coded signal is This article discusses the rea- Department Report RD1976/20. adapted to the PAL System I as more rugged than its analogue sons behind the choice of par- used in the UK. counterpart and may therefore be ameters used for the experimen- *The vision carrier level is taken as the peak vision carrier power at the tips of the Toward the end of 1982, the transmitted at a lower level. This tal systems, together with a sum- sync pulses, and the levels of the main and BBC conducted over -air compa - reduces the level of any interfer- mary of the test results. second sound carriers refer to the respec- tive levels of the unmodulated carriers.

ELECTRONICS & WIRELESS WORLD JULY 1984 19

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ELECTRONICS & WIRELESS WORLD JULY 1984 21

www.americanradiohistory.com INTERFACING by R. M. Adelson Music keys for the BBC microcomputer Using the computer's sound unit or external generators, this economical polyphonic keyboard interface makes a musical instrument and an educational tool for storage, analysis and display Ronald Adelson graduated in engineering from Cambridge of music. University in 1956. After a spell in industrial electronics Potential of the microcomputer as costing around £2 500. The in components and drawing about he entered the field of opera- a tool for teaching, editing and Alpha Syntauri is intended for use 60mA from the computer's 5V tional research which has perhaps even composing music is as a synthesizer but there is now supply, which hasn't caused prob- been his principal occupation great, as the amount of music - some elementary teaching soft- lems even while two disc drives since. However he has kept up related software currently avail- ware available for use with it. are powered from the same an active interest in electron- able will testify. This software Some other (mainly American) source. ics, especially where it impinges on his interests as a however suffers from one serious music teaching systems were musician (actually he plays drawback - the means of enter- recently reviewed by David Design considerations the bassoon - perhaps not ing musical information into the Ellis*. quite the same thing!). He computer. These means include Lancaster University's music Synthesizer applications were got joined the Operational the computer's typewriter -layout department is studying possible considered a prime objective Research Department of Lan- keyboard and sometimes games uses of microcomputers in although the design can be used caster University in 1967. A paddles or joysticks but all are aspects of its work including the to play the computer's own sound recent initiative by the Music clumsy, slow and error prone training of musicians, music edit- generator or external units. No Department at Lancaster is which is a great discouragement ing and research into music anal- attempt was made to make the currently enabling him to spend some of his time putting to the musician (as opposed to the ysis. We felt from the outset that a keyboard touch sensitive to mea- his technical skills to work. computer enthusiast) attempting `musician friendly' input device sure the speed of key depression; to use the computer creatively. was essential for acceptance by simple on/off key switches will Fig. 2. Circuit of the There are systems that potential users and given the cost suffice. Uses envisaged for the music -keyboard interface. include the natural input device of commercial systems - not to interface suggested that it should Whenever strobe voltage goes for a musician - a music key- mention their shortcomings - be fully polyphonic, i.e. should outside the narrow window board - but they are mainly we decided to develop a straight- accept chords and should not be defined by R54.56, dual intended for computer -based forward and cheap keyboard restricted to the one -note -at -a - comparator IC, generates an synthesizer applications. Best interface for the BBC microcom- time characteristic of typewriter - interrupt at CB,. The computer then responds by reading the known of these are probably the puter. The outcome is a keyboard style keyboards designed for inputs of IC,.B, then clocking Fairlight Computer Musical and interface costing around £50 computer input. Finally, rapid them on using CB2 on IC, Instrument costing around response was required and in *David Ellis, CAMI - Some educational until the whole keyboard £20 000 and the Alpha Syntauri music programs. Electronics and Music some circumstances the compu- status has been read. add-on for the Apple computer Maker, Oct. 1983. ter might be processing input

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22 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com te

information in real time, suggest- seemingly effective keyboard is the switch is opened, C. tries to +5V ing that time should not 5e easy to assemble and much discharge through R1,2 and R. and wasted by scanning the keyboard cheaper than using conventional in doing so pulls the strobe line unnecessarily. organ key switches. Some initial above 2.5V by an amount These conditions were met 3y problems were experienced due depending on the values of the making the system interrupt to key bounce caused by spring resistors. The capacitor now dis- driven and bit mapped. TI- is vibration but these were solved charges and recharges to the orig- means that any change in key- by inserting lengths of soft foam inal steady-state voltage through board status due to a key being plastic at the edge of the p.c.b. R, and R, so key status can be pressed or released produces an where the switches are soldered read at point S. the com- to the vibrations. If several keys are connected interrupt signal causing damp 5 puter to read the status of all the The BBC microcomputer user to the strobe rail each with their notes on the keyboard. On read- port is connected to the B lines of own RC networks, their behav- ing the keyboard, the computer a 6522 versatile interface adap- iour will be similar but step mag- o stores a bit -mapped image (zero tor, v.i.a. It carries eight data nitudes and associated time con- r Switch opened -25 for an unpressed key, one for a lines, Do two handshake lines, stants will depend on how many Switch closed pressed key) of the current key- CB, 2, a number of ground lines keys are pressed. For example, if Fig. 1. Outline of the board status for subsequent anal- and the computer 5V supply. 48 keys are pressed - a tricky keyboard's interrupt ysis, display, sound generation, Through programming, the v.i.a. feat even using arms instead of generator. Closing or opening etc. can be made to generate an inter- hands - pressing the 49th key the switch causes the voltage rupt signal when CB, changes places the last C. in parallel with on the strobe rail to act as Hardware from high to low or alternatively the 48 others and limits the step shown. Each pulse causes an low to high - but not both. For size to about 100mV. However, interrupt. A four octave C -C (49 note) key- the keyboard, a response is as long as the system can detect board is used. Initially, the 49th required when any key is pressed, the smallest possible step and note proved a minor nuisance or released, and even if a number react to the minimum time con- since 48 notes can be neatly of other keys are already held stant while the maximum time mapped into six bytes. However, down, so a means producing a constant is short enough to in the final design it turned out b suitable interrupt signal is ensure that recovery occurs be convenient to read the key- needed. before one has a chance to press T board in eight bytes so the system Figure 1 shows basic key con- the next key, all is well. Compo- Any key can accommodate a five -octave nections in which two equal resis- nent values shown allow the key- changes state keyboard. One byte is used to tors, R1,2, establish a steady-state board to respond to chords of any check that spurious noise pulse; voltage of 2.5 on the strobe rail. number of notes that I have have not sent the interface byte Each key switch is conncted to a managed to reach over and to Interrupt generated counter out of step with the read- network made up of R. and C.. trills and glissandi without prob- on C B1 ing software. Initially, C. has a potential differ- lem. Keyboard and key switches ence of 2.5V across it (lower plate Negative-going interrupts can used are those sold by Maplin 5V, upper plate 2.5V). When the be produced by taking the strobe Computer waits Electronic Supplies as the basis o switch is closed, the lower plate line to the non -inverting input of a a few milliseconds their `Spectrum Synthesize? (no potential falls initially by 5V and comparator whose input is biased n.0 connection with the well known. as the capacitor's charge cannot just below 2.5V so that it microcomputer). The key change instantaneously, so does responds only to negative -going switches are unusual in that they the upper plate's potential i.e., pulses, and to the inverting input Computer reads data byte are simply coiled springs soldered the strobe potential drops to -2.5V. of a further comparator, whose 07 DO to a p.c.b. at one end and touch- In due course, C. discharges non -inverting input is at just h ing a bus bar on the p.c.b. at the through R2 then recharges with above 2.5V, which responds only other end when the key is pressed reverse polarity through R, and to positive -going pulses. The Computer sends (the p.c.b. is also supplied). This the strobe returns to 2.5V. When LM393 dual comparator is ideal pulse on CB2 for this purpose since it works to clock ICiO with a 5V supply and has open - collector outputs which can be to produce OR gat- n=n+1 3 Ry, R59 C53 10u wired together 3k9 10k 2% R57 10k ing. f-V111 Figure 2 is the final circuit. Resistors R1,2 provide bias for the 8 ' R3.51 C1_49 are IC9a strobe rail and and 5 3 5 R. and C. for each key, Fig.1. LM 393 Resistors R54 bias for 2 -se provide the comparators, IC9. Resistor R58 10 R55 100 111. A (,593' R59 forms collector load and resis- 1M o8 CB2 2% B tors R57 58 provide some hystere- '-' Terminate c sis usually a good policy when R52 - interrupt comparators to improve ^v^vN_ 10 using D2 10k IC9b noise immunity and switching J, 1 CB1 I 4 times and to reduce tendency to At switch on, the counter is set 1N4148 D1 is CS2"'" spurious oscillations. The input to zero and its synchronism C50..» R56 C54 R60 checked each time the 1N4148 100p 10k 100n 100n voltage on IC9 must not be 2% to fall below ground and it keyboard is read. The delay allowed allows for key bounce and for can be seen from Fig.1 that the the fact that is impossible to z strobe rail can do this - hence play all the notes of a chord Continued on page 29 simultaneously. ELECTRONICS & WIRELESS WORLD JULY 1984 23

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CIRCLE 24 FOR FURTHER DETAILS. Track down SWITCHMODE power supply ...Barlec-Richfield and SGS have the solution L296 SWITCHING REGULATOR Available ex -stock Cost effective Short circuit protected Output over voltage protection Switching frequency to 200kHz 5.1v to 40v output Phone: 0403 51881 Very high efficiency 4A output current Telex: 877222 (up to 90%) 160w output Up to Thermal shutdown power Remote inhibit and Programmable current I3ARLEC sync input limiter Control circuit for crowbar RI FIF Soft start now better served to serve you better SCR Reset output For complementary evalu- Barlec- Richfield Ltd Precise (± 2%) on - ation kit please write to Foundry Lane, Horsham. West Snm,ex RH 13 5PX chip reference Barlec-Richfield on your A member of the IBR Electronics Group 0 Very few components company headed paper. CIRCLE 10 FOR FURTHER DETAILS. 24 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com TREE TV

by S.P. Kosta K.N. Shamanna Television reception R. Bhawani Shanker with papaya tree K.S. Dayashankara B. antenna Rudralingappa V.R. Katti Novel technique couples ri. energy from Y.P. Kosta vegetation canopy to receive tv signals.

Back in 1979 we conceived of We further reported' experi- received signals from the Banga- using green vegetation canopy as mental studies to receive Band 3 lore tv transmitter using a few live an r.f. antenna and conducted television signals from the Banga- papaya trees (one at a time only) feasibility studies with a live cyp- lore transmitter (radiating 1kW) of height around 3 to 5m in length ress plant and freshly cut date by using freshly -cut date palm and located firstly at 12km and palm leaf branch at 1000MHz to and coconut branches, of length later 25km away from the trans- successfully demonstrate it'. 1.5 and 3 metres respectively. mitting tower. Later', we conducted experimen- The vegetation cover with rea- tal studies to use vegetation sonably good signal-to-noise Experimental set up canopy (leaves and branches of ratio. A new simple method to tap gulmohr, canna, bottle brush, the r.f. energy captured by the coconut, date palm, fern, etc) as leaves branch was reported at the In this last experiment a few pap- electromagnetic antennae struc- same time. aya trees (used one at a time), of tures at microwave frequencies. And most recently, we height around 3 to 5m were Dr Shiv Prasad Kosta gradu- These studies reveal that certain ated from Jabalpur University geometrically-shaped vegeta- and took his Ph.D. in Telecom tion, due to water and chlorophyll engineering in 1969 at the content vis-a-vis their dynamic same university. Dr Kosta is a specialist on complex dielectric properties can antenna and transmission line sustain, propagate and radiate systems and has more than electromagnetic waves from their 120 research and technical structure if suitably excited. A papers to his credit. He takes gain varying from 2 to 5dB over an keen interest in basic research exciter probe antenna from problems relating to electrom- selected vegetation canopies at agnetics, antenna and micro- 3000 and 4000MHz has waves and has guided students 1000, for M.Tech and Ph.D. degrees. been achieved with satisfactory Recently, Dr Kosta conceived impedance-matching character- of using trees and salt solu- istics. (The radiation pattern of tions as tv and radio antennas the exciter probe antenna be for very high and microwave shaped with increased its gain frequencies. axially when it excited an e .m. Presently, Dr Kosta is work- wave on vegetation cover struc- ing as head of systems integra- ture.) A range of branches from a tion, at the ground checkout tree branch a bunch a and test division of ISRO Satel- single to of lite Centre, Pennya, Banga- few branches (kept in a plastics lore. cone to maintain a dielectric -rod antenna configuration of the bunch) were used to achieve bet- ter radiation pattern characteris - tics with a gain of around 5dB over that of the exciter probe antenna In all these studies a probe helix at the end of a vegetation branch was used to excite an e.m. wave on the vegetation structure. The radiation characteristics so observed were found to remain so The authors are with ISRO Satellite long as the vegetation structure is Centre, Bangalore, India, except S.P. fresh, and start to deteriorate Kosta who is studying at the National with increase in dryness. Fig.1. Field receiving site College, Jayanagar, Bangalore. ELECTRONICS & WIRELESS WORLD JULY 1984 25

www.americanradiohistory.com TREE TV

Fig.2. Probe coupling need to be studied in depth. configuration Under average conditions (slow breeze and feeble rain) the observed tv picture quality was fairly satisfactory.

Theoretical model

To a first order of approximation one may simulate either - suitable symmetrical and geometrically-shaped freshly - cut or live vegetation branch or a bunch of branches (like fern, date palm, bottle brush) as a standard well-known die- lectric rod antenna configura- tion; or - papaya, coconut, banana - type live branch leaf as a thin dielectric sheet aperture antenna. The exact constitutive par- ameters of a green leaf are not well-known4. Because of the very large static dielectric constant of water one can well expect that the moisture content of the leaf will have a predominating influence. A reasonable estimate of the complex dielectric constant of green foliage (Du and Peake4) can be made from the following equa- tion:

75 g,. -1 - GE (+

where ge the ionic conductivity due to dissolved salts of the fluid in the leaf, G is the fraction of water content, ft, is 16GHz, and ocated to receive line -of -sight economically receive television o have the usual meanings, and signals at a distance varying from signals. the conductivity of the dissolved 12 to 25km from radiating tv salt may vary widely but is tower were used to receive Observations assumed here to be 0.2 to 0.4 X colour, as well as black & white 10-4mho/m. Further, the effec- signals. A flexible coaxial cable tive relative dielectric constant of (RG-58A/U) tapped r.f. energy The signal received with the the medium can also be written as from the appropriately selected probe antenna alone at the height places of the tree. The inner con- of the tapping point was very hazy g, ductor of the BNC connector (unreadable) at 12km distance ,_+-lmu REFERENCES (EMRI-506, projecting by and, practically, identification of 1. S.P. Kosta, et al, Cypress plant as r.f. whereR is the effective dielectric antenna, Frequenz, April 1979, pp.117/8. around 3mm) was pierced the picture wasn't possible, Fig. constant, and gi the effective con- S.Y. Kosta, et al, Date palm tree branches through first into the trunk and 3. Further, no signal was received as antenna structure Nachrichten ductivity. Technische Zeitschrift (NTZ) April 1979, then at the end point of the stem by the probe alone at 25km dis- Du and Peake4 measured p. 236. supporting the green leaf of the tance. values of the relative dielectric (Fig. 1). The signals received from the 2. S.Y. Kosta, et al, Gulmohr vegetation tree constant (tt 1.01 to 1.04) and canopy as antenna structure. The maximum signal tapping papaya tree trunk, its one green effective conductivity (gi 0.2 to Communicated to IEEE Transactions on point was found after many trials, leaf and the dipole antenna at Antennas and Propagation, paper C-013 0.4 X 10-4mho/m) of the green June 1983. from which we found that the 12km and 25km distance, were of leaves with varying percentage of piercing end of the inner conduc- good readable quality. The 50%) the 3. S.P. Kosta, et al, Coconut tree branch water content (10 to and - nature's television antenna. tor should touch the moist/wet v.s.w.r. under best conditions of volume concentration of the Communicated to Proc. IEEE, September portions of the tree (xylem, reception was around 1.5. Only leaves (in the range of 0.0003 to 1983. phloem, chloren chyma, etc). the leaves pointing clearly toward 0.001) at v.h.f. They have also 4. Li-Jen Du and W.H. Peake, Rayleigh The other end of the coaxial cable the tv transmitting tower without found that dielectric constant is scattering from leaves Proc. IEEE, June was connected to a Sony portable obstruction received good televi- 1969, pp. 1227-9. nearly independent of frequency receiver model CVM-111E. The sion pictures. To achieve higher in the v.h.f. band. Spence and 5. J.E. Spence and K.G. HeislerJr., Radio BNC connector is not necessary gain (better s/n ratio of the have reported dielectric propagation loss in a tropical jungle. Heisler' Abstracts of URSI 1967 Fall Meeting, to tap the r.f. energy, Fig. 2. A received tv picture), standard constant of jungle environment University of Michigan, Ann Arbor. bare sharpened inner conductor antenna array techniques using a as êi -1.02 and conductivity gi of RG-58A/U cable itself few suitably located Papaya trees 6. Jasik, H. Antenna Engineering end 10-4mho/m. It is also known that Handbook. McGraw-Hill, New York, 1961. should be used in practice to or a few suitably oriented leaves Continued on page 29 26 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com VARIABLE -SPEED VIDEO

by J. R. Watkinson, Variable -speed M.Sc., B.Sc. video playback Using C -format video recorders over a wide speed range. Discussion continues with a description of the effect of the recording process on video waveforms.

At +2X and at 0, a single- jumped, the machine can always * 1/2 f H track jump is required every drum. know where it is in a field, and I-1 u revolution, whereas at -1X and. generate convincing vertical V u IV +3X, a two -track jump is pulses which it has not played required. At intermediate back. The drum servo will use speeds, a sequence of single and these corrected vertical signals in r two -track jumps is made. A order to maintain correct drum 283f H 284f H in 283h single-track jump will always be phase the presence of head fH made, but if the bimorph dis- jumping. It is important that the placement exceeds one track at off -tape field rate should always to rotate at constant speed with Fig. 10. In PAL, subcarrier the end of a field, a two -track equal reference field rate: the rea- respect to the earth, owing to its must be at odd multiple of one jump is needed. This process can son for this will become clear inertia, and if the v.t.r. is turned quarter line rate for IJ and V be extrapolated up to any speed when the timebase corrector is about the drum axis, the drum spectral peaks to interleave as necessary until the travel of the discussed. phase will change until the drum with luminance (Y). Unlike bimorph cannot cater for com servo can correct it. This is often NTSC, there is no dominant plete tracks. In this extreme case, Effect of the v.t.r. on video erroneously referred to as 'gyros- component at 1/24 points. a maximum size jump will take waveform copic error'. place whenever the travel limit is Video tape is also subject to Fig. 11. Quarter-cycle approached. PAL is playback r.f. subcarrier/H relationship and Mixing and editing in video dropout, where the to give only provided that all level is low to resolve the fre- burst swing combine The head jump must take possible too four -line sequence- normal place during the vertical interval sources are synchronised to quency. Although the mechanism which is in order that it shall not occur in a within about 5 degrees of subcar- of dropout cannot in itself change and inverted pairs visible part of the picture. There rier, which is approximately 3 not absolutely defined. is, however, a further difficulty. nano seconds. A field in PAL has a One cycle In C -interval duration of 20 milliseconds, so -format, vertical sto- H sync of burst rage is optional and vertical the stability demanded is: detection is done by locating the 1-4 bps approx 3x10 equalising pulses which are at the 3 X 100%=©.000015% end of the main field track. These 20X 10- pulses are relatively narrow, and As no mechanism can approach could be missed in the case of such a tolerance, timebase cor- Burst Normalf swing dropout. They are thus predicted rection is mandatory even at nor- + 1c cycle sc lead = no change by mal Yi. cycle and validated counting lines speed. lag along the field track. The 3'/2 line Video tape, like all magnetic timing shift between adjacent tape, has a plastics backing, fields has been mentioned: if a which has a relatively high tem- jump takes place, this shift has to perature -coefficient of linear ti be taken into account in order to expansion, and can also change locate the equalising pulses cor- its dimensions as a function of Burst swing is + 1/4 cycle sc lead = 180° change rectly. ambient humidity. It also flexi- '4 cycle When the tape speed is varied, ble. The length of a field track on lead the head -to-tape speed changes, the tape can be altered by temper- causing the off -tape H sync. ature, humidity or tension pulses to change frequency. As changes, and timing errors will be the tape -head contact is not con- caused. s tinuous, the machine has to When tapes are interchanged Burst maintain sync. from track to track between machines, mechanical swing Inverted + 14 cycle sc lead = no change by counting extrapolated H sync. tolerances on drum diameter and /i, cycle pulses at the same frequency as tape tension will change playback lag they are coming off the tape. A timing. The impact of the rotating circuit is incorporated which heads striking the tape and leav- measures the off -tape line period ing again creates shock waves \f` in cycles of a reference clock, and which travel along the tape, caus- which can generate H pulses sep- ing jitter. Burst swing arated by that period during the Where portable recorders are + '% cycle sc lead = 180°change vertical interval. By counting carried whilst recording, inertial h cycle these H pulses, and modifying the effects can cause timing shifts of Lead count by 31 lines for every track several lines. The drum attempts ELECTRONICS & WIRELESS WORLD JULY 1984 27

www.americanradiohistory.com VARIABLE -SPEED VIDEO

-50X tine period 149 Zpsec L l 0.43V pp fu=1.9MHz Appendix PAL structure I -10X, line period 72.9» sec L 0 88Vpp fsc =3-9MHz The broadcasting of colour consequence of this was the television is done in such a way development of a drop -frame U that the bandwidth of the signal time code to permit Is no greater than that of a synchronisation of this strange monochrome signal of equal frequency with real time. -1X, line period 65.5psec resolution, and that a Experience of broadcasting O'98Vpp fsc =434MHz monochrome receiver can NTSC led the PAL system, whose display a good picture from a well known characteristic of U colour broadcast without reversing the sense of one of the modification. Without these colour -difference signals on constraints, NTSC could never alternate lines had some far Peak 'white X1 line period 64p sec have been introduced, since reaching consequences. The Burst 1Vpp fsc =443MHz every monochrome tv set in the first, and intended, United States would have been consequence is that by line made obsolete overnight by a averaging, hue errors caused by Hsync// non -compatible system. phase errors under difficult The bandwidth constraint reception conditions were was achieved by choosing a converted to saturation errors, +3X, line period 62.6» sec subcarrier whose sidebands much more acceptable

1 02Vpp fsc =4 52MHz interleaved with those of the subjectively, and the hue control monochrome signal, and was eliminated from the receiver. monochrome compatibility was Choice of subcarrier achieved by encoding colour frequency in PAL is, howerver, difference signals into the more complex than in NTSC subcarrier which a colour because of the V switch. the +10X, line period 58.1» sec receiver could use to convert the effect of the V switch is to shift 11Vpp fsc = 4 88MHz monochrome signal into a colour the V spectrum up and down by picture. The subcarrier would be ±1 /2 f at half-line rate. The virtually invisible to a unswitched U signal is at the monochrome receiver. The only centre of the ±1/2f, swing of the problem was that the original V energy. designers of the 525/60 If the subcarrier (U) +50X, line period 41.3» sec monochrome system had very frequency were chosen at an odd 1 55Vpp fsc =6 87MHz wisely placed the sound carrier multiple of half line rate, this at an odd multiple of half line would make V sidebands rate, to give maximum immunity coincide with luminance. To 1 to video sidebands. This interleave Y, U and V, it is became, however, precisely the mandatory that the subcarrier frequency of subcarrier frequency is an odd multiple of Table 1 video timing, the consequence of sidebands. A solution involving one quarter line rate. The odd dropout can. For example, the a change of sound carrier multiple chosen is 1135, but 1133 destruction of a burst by dropout frequency would have meant or 1137 would have worked just renders the following chroma re -aligning the coils in every tv as well. Figure 10 shows that, set in the United States, so the using this frequency, perfect information meaningless, since only alternative was to shift the interleaving of Y, U and V is the timing of the suppressed car- video/subcarrier spectrum by achieved. Note also that there is rier is lost. Dropout compensa- changing the entire picture rate. no spectral component at half tion is thus a major function of NTSC field rate is thus 59.94 Hz, a line frequencies, a fundamental timebase correctors. change of 0.1%. A direct difference from NTSC. If the variable -speed playback is employed, the effect is to change the line period from the standard 64 microseconds. It is will be extended. Owing to the from that. Table 1 shows the possible to calculate the line horizontal alignment condition, effect of applying a variety of period for any speed. As the track this extension will be 32 off -tape speeds to the equation. Interes- lines at +2X as is one- tingly, in reverse, the field tracks angle in C-format is so small, the there a' are stretched in time, the back- error caused by assuming it is track jump at every drum revolu- 3121 wards head jumps lose 3211 for zero is of the order of 0.1%, which tion. There are normally can be neglected. The line period lines in a field, but at +2 X speed, each track jumped and the verti- 31 cal is in inversely proportional to the an extra can be fitted into the interval encroached upon. head/tape speed. At X1 forward, same field period. This holds the The change in head/tape key to a much simpler way of cal- speed also changes the apparent the tape speed is 239. 8mm/s , and the head to tape speed is culating the line period, which is frequency range of the f.m. car- X 312.5 rier, and consequently the levels 21.39m/s. If the tape is run at 64 63.29 µs head/ H 312.5 + 3.5 and amplitude of the playback +2X normal speed, the video. The percentage change now be 21.39 if tape speed will + This can easily be generalised can be derived from the equation 0.2398m/s and the line period the specific speed S is unity at be for change in line rate, since both will normal speed. are controlled by the same pheno- t 64X21.39 µs -63.29µs 64 X 312.5 menon. H 21.39 + 0.2398 tH 312.5 + (S-1) X 3.5 Jumping performed in variable a change of about 1.1%. This equation is to be preferred, speed causes fields to be omitted It is important to remember since no approximation has been or repeated, which destroys the that, although the line period made, and no knowledge of drum eight -field sequence of PAL. The becomes smaller, the field rate dimensions or tape format is recreation of the eight -field sequ- remains constant owing to the needed except the size of the ence, the correction of the time constant drum speed. The visible video offset of 31H. It is very easy compression or expansion of part of the picture is thus time- to arrive at the equation for other fields, and restoration of video compressed into a shorter part of standards. For example, in 525/ levels are the major additional the field period, and the interval 60 NTSC C -format, the video off- actions of a variable speed time - where the head is between tracks set is 21H. The equation follows base corrector. 28 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com Continued from page 23

inclusion of R52,53, D1, 2 forming a clamp at zero volts. Capacitors C50,51 and C52 are bypass capaci- tors to reduce interference from The subcarrier frequency in switching spikes, r.f., etc. PAL is thus fixed at 283; times Switch points at the junc- line rate, but with offset of 25Hz, -sense which causes residual tions of Rx and C, (S in Fig.1) are subcarrier on luminance signals each taken to an input of a group to be out of phase on alternate of eight -to -one -bit multiplexers fields, helping to make the subcarrier invisible to the viewer. (IC1_8) whose inverting outputs Subcarrier frequency is D7.0 provide a byte which can be defined as read by the computer through the v.i.a. Control inputs of the multi- 283;f -!- 2f = 283; X 312zf + = 88672.3754 plexers (A, B and C) are taken to a = 4.43361875 MHz three -bit counter whose clock input is connected to CB2 (pro- The V signal can only be decoded properly if the receiver grammed as an output) of the knows the sense of the switch. v.i.a. Capacitor C53 and R60 pro- This information is conveyed by vide a reset to zero on switch on swinging the burst phase, relative to continuous so that the counter always starts subcarrier, from line to line. A from a known position (see flow well damped phase-locked loop Fig.3A. Received TV picture by probe antenna diagram). in the receiver will run at the Thus the whole keyboard is average phase of successive bursts, but the sense of the read in eight bytes. This gives a phase error in the loop wil follow complete bit -map of the state of the burst swing and will reveal the keyboard, and some redun- the sense of the V switch to the dancy. After receiving eight clock decoder. The swing could not be +90°, because there would be pulses, the counter is back in its ambiguity about the average original state. The delay at the phase. A swing of ±135° third operation in the flow dia- corresponds to 90° between the gram is introduced to allow for lines. Spectrum interleaving any residual key -bounce and for demands a quarter cycle offset the fact that it is impossible to between subcarrier and line play all the notes of a chord simul- frequencies, a direct result of taneously. PAL V switch. Burst swing is another direct result of using V Figure 2 shows that only six of switch. The combination of these the eight inputs of IC1_, are used, two gives some interesting and only seven of IC,. It would be results. possible to fit a 48 -note keyboard The quarter -cycle shift means that subcarrier phase using all the inputs of six multi- advances by 90° from the start of plexers and it would not be neces- one line to the next. Burst swing sary to provide an additional one is also 90°1rom line to line, but for the extra note. However this alternately avanced and retarded. On some lines then, the would lead to reading only six bits 90° advance of the subcarrier per byte, causing either wasted cancels the 90° retarded burst, Fig.3B. Received TV picture by coconut tree branch memory if the inputs are to be giving no change, whereas on stored or a complex software re- others, the 90° subcarrier advance acids to the 90' packing procedure. Further, advanced burst, causing a 180° TREE TV unless complicated wiring was change. The result of this is a used to connect keys to multi- continued from page 26 We concluded that a suitably four -line sequence, containing, plexers (which would not lend relative to H pulses, two the relative permitivity of water located Papaya tree of height 3 to itself well to p.c.b. layout), the identically phased bursts, and alone, which is the dominant con- 5 metres (at 10 to 25km distance) inverted bit -mapping involved would need two identically bursts. tent of the green vegetation fol- has the properties to pick up Band Figure 11 shows these effects. extra software. The small addi- iage, is around 80 at microwave 3 tv signals from the tv tower, The two burst phases, normal tional cost of two extra multiplex- and inverted, are determined by frequencies. which can be easily tapped by a ers used offers two advantages. the state of a squarewave of 1/4 In the literature, low -loss die- suitable feeder line probe to the tv line rate. As 625 will not divide by lectric -loaded aperture antennas set. By taking six keys to each mul- four, it takes four frames before a - given relationship between the and dielectric rod antennas are However, no attempt was tiplexer (seven on the last one) an burst phase control signal and well-known for their directional made to optimize the quality of tv octave of 12 notes fits into two the vertical pulse repeats. The beam -mode antenna radiation picture received by the organic multiplexers. This makes it much 25Hz offset is negligible within the four -line sequence pattern. Low -loss dielectric rods tree antenna structure, either by easier to keep track of which bit described, but it causes the have been used in practice, with developing more efficient represents which note. four -frame sequence to contain Teflon, polystyrene (E--.2.5). antenna probes or by adopting Bit zero (pin four) of all the 2500 unique lines. Thus after carrying out antenna arraying techniques. In- - multiplexers is grounded. Thus This extremely long indepth studies of the dielectric depth studies are called for to sequence must never be broken the first byte read should be FF data cited above, and the works of overcome the effects of hostile if the signal is to be broadcast, (hexadecimal) since the outputs and this adds to the complexity Zucker, King, Ulaby, Anderson, environments (wind, rain, snow) are inverting. of videotape editors and James et al, weconceived, intuit- and to improve the s/n ratio of the timebase correctors. ively, of the idea to use the green received tv signals before any vegetation canopy as an antenna commercial venture can be Keyboard software and control structure. thought of. are outlined in a second article. ELECTRONICS & WIRELESS WORLD JULY 1984 29

www.americanradiohistory.com QUALITY COMPONENTS FROM CRICKLEWOOD! This list contains only a >< 1<.TD>t fraction of our stock, which is constantly being updated. Prices quoted are for >f1 "one-offs" - quantity discounts by negotiation. Official orders from Schools, ELECTRO NICS L D colleges, Goods Dept etc welcomed. WE SPECIALISE IN CREDIT CARD PHONE ORDERS. A quick call will check stock position and current prices. Prices subject I aaarslli to change. Add 60p p&p + 15% VAT to all orders. Catalogue 40p + A4 SAE i 40 CRICKLEWOOD BROADWAY envelope. All in -stock items despatched same day unless notified. LONDON NW2 3ET V/SA 'l .< 01-452 0161/01-450 0995 TIx:914977 70626114 2.50p 7472 49p 74LS 24 1 55p 4047 75p 280ADART 8.39p 256253 1.630 BD138 39p MPSLOI 69p R5U 38p WIRE RESISTORS E LE CTROLY TICS SCR's T1367000 345p Mainly 7473 35p 7415125 55p 4048 54p 280APIO 3.45p 256254 1.77p BD139 42p MPSL51 75p G5U 42p TRIACS 05U 42p TL061 51p CARBON FILM Matsushita 7474 49p 7415126 55p 4049 45p 25425E8 3490 2SC1306 99p 813140 42p MPS405 89p PRICES PER 49p 4050 49p 11.062 77p 5', HI STAB & 7475 49p 7415132 25426E8 3.10p 30201 1 99p BD239A 65p MPSU06 99P DIACS METRE (Panasonic) Rectangular TL064 1.35p LOW NOISE 7476 49p 7415133 390 4051 75p 25427E8 5.99p 40361 7sp BD239C 696 MPSUO7 1 75p Siemens Slackable LEDs 11071 47p Solid connecting 101? TO 8,X18,15 (Wires 7480 59p 7415136 45p 4052 69p 25428E8 4.55p 40362 75p BD240A 68p MPSU51 1.29p wire RSR 18p TL0]2 62p IOW 7481 1.29p 74L5138 89p 4053 59p 40363 3.99P BD240C 79p MPSU56 1.22p THYRISTORS each endl GSR 19p TL074 1.39p MAINS/SPEAKER 7482 99p 7415139 59p 4054 79p 720 MPSU57 1 95p 1 4W E24 2p uFd V 40406 1.75p BD241A 4.8& 12 Amps Twin 1 Amp 14p Y5R 21p TL081 47p 12WE24 3p 47 7483 69p 7415145 95p 4056 99p V 40408 1.75p BD241C 79p TIP29A 35p Texas 10220 Twin 2117 Amp 63 8p REGS TL082 55p 1WE12 60 47 100 7484 99p 7415147 1 35p 4059 4 49p 40410 1.99p BD242A 75p TIP29C 42p Suffix A = 100V 16p 9p TL084 1.20p 2WE12 12p 7485 99p 7415148 1.259 4060 69p -Positive - 40411 3 99p 80242C 79p TIP30A 37p B = 200V 3 Core 2112 Amp 47 350 30p 08,6170 2.49p 7486 7415151 59p 4063 89p 1 BD243A 85p TIP30C 44p METAL FILM 1 63 Bp 39p 100mA 40673 49p C 300V 18u U44.180 2490 ULTRA STABLE 7489 199p 7415153 590 4066 44p 781058, 290 40822 1.99p BD243C 89p TIP31A 39p = 400V 1 100 9p D LIN ICs 3 Core 13 Amp 450 7415154 2.350 4067 2.390 BD244A 88p TIP31C 470 ULN2003 75p 0.4W EXTRA 1 500 40p 7490 781124 29E AC125 99p M = 600V 1360 4068 27p TIP32A 46p UPC575C2 200P LOW NOISE 2 2 25 Bp 7491 59p 7415157 690 78L15Á 29p AC126 35p 802440 1.15p 4A SCREENED UPC1156 2.75p 1011 TO 1MII 12 63 9p 7492 49p 7415158 69p 4069 27p 78LM4 290 AC127 35p 1302459. 1.19p TIP32C 49p TIC106A 49p E24 6p 7493 7415160 75p 4070 27p AC128 39p 8D245C 1.49p TIP33A 69p A015050 990 UPC1156H 2.75P 1'. 2.2 100 I 1 p 39p TIC1068 5I0 Stereoe 17p 74L5161 75p 4071 27p 1.39p TIP33C 83p A038910 3.99p Ú0011132 3]513 LOW OHMIC 2.2 350 300 7494 99p 1 Amp T0202 AC141K 39p 130246A TIC106C 53p Mini Single 12p 6038912 4950 UPC11B5 195p 1 750 4072 27p TIP34A 1.19p GLAZE 2W 3.3 25 10p 7495 49p 7415162 78057 45p AC142K 39p BD246C 1.67p TIC106D 550 Mine Stereo 150 4073 27p 1.26p CA3048 2.15p 0002002 0 721110 8.211 3.3 40 llp 7496 59p 7415163 85p 7812T 45p AC151 77p BD249A 2.30p TIP34C TIC106M 720 4 Core 4 screens 1.260 CA3059 3.290 XR2206 3.35pp E24 1 1 p 7497 1 75p 7415164 Sp 4075 27p 7815T 45p AC152 77p BD249C 2.57p TIP35A 8A 440 33 63 12p 2.250 4076 65p TIP35C 1 39p CA3090AO 3.70p 25409 WIRE WOUND 47 16 9p 74100 139p 7415165 99p 7824T 45p AC153 77p B02504 2.48p TIC116A 69p 4 Core single 1.420 CA3130E 87p 219414 1 00p ON CERAMIC 4.7 25 9p 74104 59p 7415168 1.390 4077 27p AC153K 87p 80250C 2.75p TIP36A TIC116B 72p orean 54p CA3130T 2.35p 201034 74L5169 1 4078 27p 1 75p TIP36C 1.49P E12 SERIES 47 40 tlp 74105 59p 29p - Negative - AC176 39p 813529 TIC116C 75p B Core 61p 4081 27p TIP41A 52p CA3140E 54p 210 3W 0.2211 4 7 63 12p 74107 45p 7415170 99p 100mA 1092 AC176K 49p 130530 1.95p T1C116D 78p 12 Core 600 4085 59p TIP41C 58p CA3140T 1.40p to 33011 28p 4 7 100 14p 74109 45p 7415173 99p 79105 49p AC1B7 39p 130535 99p T1C116M 84p Heavy Duty 4086 69p TIP42A 62p HA1366W 2.409 4 to 7W 0.470 10 25 Bp 74110 69p 7415174 65p 79112 49p AC198 39p BD536 89p 12A TRANS- Mike/Guitar 4089 1 25p TIP42C 65p 861388 2.54p 0 658 33p 10 40 12p 74116 125p 7415175 85p 79115 49p AC187K 49p 130537 97p TIC1266 Lead 250 TIP49 1.29p CL7106 7.500 FORMERS 916 11W 111 10 63 14p 74118 1.25p 7415181 1 O5p 4093 65p AC168K 49p BD538 97p O 01260 750 AERIAL 4094 990 TIP50 1.52p CL7107 9.500 to 33K 37p 10 100 16p 74119 1.25p 7415183 1.45p 1 Amp 70220 80107 16p BD539 1.08p TIC126C 76p 501113058A 25p 4095 89p TIP53 1.58p CL7611 97p 10 350 55p 74120 1 25p 7415190 65p 79057 57p 8C107A 17p 80539C 1.33p TIC126D All 240V Primary 7511 UHF 2911 4096 89p 1.04p TIP54 1.65P CL8038 2.99p POTS & 22 25 ltp 74121 45p 7415191 65p 7912T 57p BC107B 19p BC/540 TIC126M Split Bobbin 7511 VHF 281, 74122 49p 7415192 65p 4098 99p 7915T 57p BC108 16p 80540C 1.39p TIPI 10 79p CM7555 1.10p 100mA PRESETS 22 40 14p 1,49p 30011 Flat 1411 4099 1 09p TIP112 8sp CM7556 1.10p 22 63 16p 74123 79p 7415193 65p 7924T 57p BC108A 17p BDX66B 6.35p TRIACS 6-0.6 RAINBOW 40103 2.590 TIP115 890 LC7120 3.20p 1.20p 22 100 21p 74125 49p 7415194 65p BC1088 1Bp 600618 6.35p Texas 400V 9-0-9 RIBBON ROTARY POTS 4502 59p 1.050 101130 3.40p 47 25 14p 74126 49p 7415195 65p BC108C 20p fiDY54 2.28p TIP117 10220 Case 12.0.12 1.37p Prices per foot LOW NOISE 4503 59p TIP120 79p LC7137 3.95p 47 40 17p 74128 65p 7415196 65p BC109 17p BDv55 2.39p TIC206D14A1 69p 15-0-15 1.45p 10 way 2511 1 4- SPINDLES 1E347 1.50p 47 63 26p 74132 59p 7415197 65p 4605 3.75p TRANS- BC1098 18p BDY56 1.99P TIP122 85p TIC225D16A1 79p 14 as above 16 way 190 E3 SERIES 45p 1E351 59p 47 100 28p 74136 49p 7419221 1150 4507 ISTORS BC109C 21p 811057 591p TIP127 99p TIC226D18A1 92p 2.959 10 way 48p 45710 2M LIN 4508 1 49p 1 LF353 1.05p 100 16 14p 74141 79p 7415240 1.99p BC140 38p BD758 6.33p TIP130 06p TIC236D(12A) 20.020V 24 way 62p 38D 83p 1 1.090 1F 100 25 t6p 74142 199p 7415241 99p 4510 69p 202219 33p BC141 43p 13E194 18p TIP132 1.25p 0.1254 2.959 30 way 750 457 to 2M LOG 1.16p LF335556 99p 100 40 22p 74143 1.99p 7415242 1.99p 4511 690 1N2219A 36p BC147 15p 13E195 18p TIP135 TIC2461)116A1 12.012V 34 way 020 380 4512 69p t 19p LF357 1.30p 100 63 25p 74144 199p 7415243 1.99p 202220 33p BC147A 16p 8E196 18p TIP137 1.35p 50VA 5.950 40 way 680 As above with 74145 89p 7415244 2 4514 1.250 18p TIP140 1.210 1E398 4.62p 12.0 12V 100 100 30p 95 21922214 33p BC147B 17p 86197 TIC253D(20A) 64 way 1 49p DP Mains Switch 4515 1.25p 18p TIP142 1.22p LM3352 1.60p 100VA 9.95p 220 10 t6p 74147 99p 7415245 3.250 2N2222 29p BC147C 77p BF19B 1 99p 88p 4516 89p TIP145 1.21p LM348N 62p 220 16 17p 74148 99p 7415247 1.990 2522224 33p BC148 15p 8E199 18F TIC263D125AI 0+606+9+9 As above stereo 1.220 LM349N 1,09p RECHARGE 220 25 22p 74150 1.39p 7415248 1.99P 4518 69p 202223 5.85P BC148A 17p 8E200 79p TIP147 2.25p 1.254 4.95p 99p LM350K 4,89P 220 40 25P 74151 59pe 7415249 1.990 4519 75p 2522234 6.25p BC148B 19p BF244A 61p TIP162 4.999 These goods are BATTERIES PRESETS PIHER 75p 4520 75p 55p TIP2955 Blp LM3795 5.509 220 63 30p 74153 59p 7415251 202368 33p BC148C 25p BF2448 DIALS heavy send extra IOU STPR00FI 4521 1.050 TIP3055 79p LM380514 1.100 220 100 400 74154 1.99p 7415253 75p 202369 34p BC149 16p BF245A 63p BR100 29p p&p. We will Top quality E3 1001110 10Mí 1 4522 890 61p LM3805B 1.50p 470 16 220 74155 55p 7415257 75p 2523694 35p BC149B 19p 13E2458 66p TIS43 ST2 29p credit any Dont throw Mine Vert 150 Sop 69p LM381AN 2.26p 470 25 28p 74156 55p 7415258 750 4526 2529040 35p BC149C .26p 61E246 77p VN10KM difference. these batteries Mim 11010 15p 1.15p LM381N 1.40p 470 40 330 74157 55p 7415259 1 19p 4527 89p 2N2905 35p BC157 39p BF246A 79p VN46AF way - they Standard Vert 1 LM382N 1.22p 470 63 43p 74159 1.290 74L5261 990 4528 75p 2029054 38p BC157A 410 BF246B 79p VN66AF 09P charge up to 18p ZENER'S LM383T 3.40p 470 100 60p 74160 79p 7415266 55p 4529 89P 252906 35p BC157B 44p BF247A 79p ZTX107 12p VERO 1000 times, Standard 001q 4532 89p 13p LM384N 1.409 1000 16 30p 74161 59p 7415273 pis ask 252907 35p BC158A 37p BF2478 79p ZTX108 HP211.26HI 180 140 LM3865 1.20p 1000 25 38p 74162 59p 7415275 1.750 4534 3.95p 2529074 38p BC1588 3917 0E254 66p ZTX109 many inc 0.1' COPPER 2.39p CERMET 20 2.43p 1000 40 46p 74163 59p 7415279 65p 4536 2.29p 252926 13p BC159 44p 9E255 68p ZTX300 12p specials see our LM3585 TRACKS HP214AHI 4.75p TURN I.M391N60 2.25p 1000 63 65p 74164 75p 7415280 1.75p 4538 89p 253053 35p BC159A 45p BF256A 59p 2TX301 16p CAT 2.5 x 3.75 950 HP7112AH1 991/ PRECISION 7415283 4543 99p 17p 400 to _M391N80 1.65p 2000 16 40p 74165 85p 75p 203054 65p BC159B 46p 8E2568 59y ZTX302 500mW 2.5 x 5 1.O8p HP1111.2AH1 PRESETS 4553 2.19p 25p LM723CH 990 2200 75 63p 74166 99p 7415290 75p 203055 85p BC159C 480 BF256C 69p ZTX303 624 Series 3.75 x 3.75 1.09p 2.290 3 4' E3 SERIES 18p to 47V 7p LM723CN 49p 2200 40 70p 74170 149p 7415293 65p 4555 58p 2N3055H 1.89p BC160 55p 13E257 39p ZTX304 2.4 3.75 x 5 1.23p PP3111 OmAH1 500 to 500K 89p 4556 58p 39p L M725CH 3.40p 2200 63 1.34p 74172 249p 7415295 75p 253439 1.15p 80161 59p 86258 41p Z1X310 2.5 x 17 3.27p 4.951, ZTX311 36p LM725CN 3.190 4700 16 75p 74173 75p 7415298 75p 4560 1 79p 253440 99p BC167 19p 6E259 45p 1.3 Wan 3.75 x 17 4.290 Chargers 4566 1.99p 390 Series LM741CH 96p CAPS 4700 25 89p 74174 89p 7415299 1.75p 253441 149p BC169 19p 13E457 48p 210312 E24 4.79 x 17 5.99p TYPE H 21X313 41p LM74105 190 74175 69p 7416323 2 25p 4569 1.99p 253442 1.59p BC1698 22p BF458 59p 3.3 to 82V 14p VO Board 2.10p Adluºted to 6 of CERAMIC 100V RADIALS LM741CN14 Bop (PCB 69p 7415324 1 75p 4584 49p 23p 9E459 65p ZTX314 279 any HP type DISC IPLATEI 74176 203638 62p BC169C DIP Board 3.95p wires one end) 74177 69p 7415325 1.750 4585 64p 16p BC177 29p 6FR39 32p ZTX320 37p LM747CN 69p Above 15.59u E 12 MICRO MINI 2N3702 Treck Cuiter Matsushita only 2.99p 32p ZT%330 39p LM748CH 1.00p TYPE M. TYPICALLY 74178 99p 7415326 253703 16p BC177A 33p BFR40 1.630 uFd V ZTX341 31p BRIDGE LM748CN 42p 74180 69p 7415327 2.99p 203704 l6p 8C177B 36e BFR41 320 Pin insenor As above but 16 LM1871 3.250 10 6p 74181 159p 7410347 75p LOGIC 253705 16p 80176 29p 8E879 32p ZTX450 41p 721p faster charge for 1 F to lunF 7p 10 22 6p 7415348 1 75p 32p ZTX500 15p (Ph/ shown in LM1872 4.39p POLVCARR 5'e 74182 69p 203706 16p BC178A 33p 8FR80 100 Pins 61p 4ÁH 25.95p 16 70 LM1877 5.95p 11 74184 149p 7415352 85p CPUs 203707 16p BC178B 36p BFR81 32p ZTX501 15p brackets' Verobloc 4.66p TYPE P SIEMENS 7.5mm 10 7p 1117 47 74185 149p 7415353 850 1802 6.49p 16p BC179 31p BFR90 2.25p ZTX502 15p amp type LM1686 7.44p PP3 5.50p MINI BLOC E 12 203709 Vero Wiring 47 16 Op 1Bp W01(1001 26p LM1889 3.77p 74190 69p 7415362 1 99p 6502 3.99p 203709 31p BC1798 39p BF561 99p ZTX503 Pen & Spool TYPE A: 250V 100 10 9p ZTX504 19p W0212001 34p LM29075 2.759 74191 75p 7415365 49p 65024 649p 203710 34p BC179C 410 61E698 99p 3.39p HP7(Up to 4 at a 1 nF to 6n8 7p 16 10p LM290758 2.600 100 74192 85p 7415366 49p 6800 2.75p 203711 37p BC182 15p BFX29 44p 2T%510 28p W04(200) 38p Spare Spool 75p time) 5.85p 802 to 47nF Bp 10 220 1Ip 74193 69p 7415367 49p 2 99p BC182A 17p 46p ZTX531 290 WO8(800) 50F LM2917N 240p 56nF to 150nF 6802 2N3773 209p BFX30 Combs 6P 16 12p L M2917N8 2.40p 210 74194 55p 7415368 49p 6809 9.95p 203819 55p 8C182B 19p BFY53 53p 2TX650 47p 12p 470 10 170 SOLDER 74195 59p 7415373 2800 8035 545p 2N3902 6.88p Bel 821 15p BSX19 290 ZTX651 4Sp 2 amp typa LM3900 62p 100V 1.450 470 16 1130 74196 55p 74L5374 2 80p 8039 5 45p 19p BCIB2LA 17p BSX20 330 21X652 49p Square with hole LM3911 100,0 to 150nF 253903 ANTE% SOLD- 1000 10 20p 74197 89p 7415378 99p 80804 3.55p 19p BC182L8 19p 85X21 49p ZTX653 50P 50111001 46p LM3914 3.25p 30 253904 ERING IRONS 1000 16 24p 150p 7415386 75p BU104 2.32p ZTX750 47p 50212001 50p LM3915 3.25p 180nF to 270nF 74198 8085 9 45p 203905 19p BC183 tap 2200 10 34p ZTX751 48p LM13600 1.15p FERRIC C240115WI 5.20p 74221 1 50p 7415390 75p Z80A CPU 3.590 253906 19p BC183A 16p BU105 1.89p 50414001 550 160 44p 00240(25W) 2200 16 7415393 99p Z80B CPU 945p 204030 88p BC1836 19p BU108 2,49p ZTX152 49p 50818001 660 MF10 3.75p CHLORIDE 330nF 10 390nF 10 5.40p 3300 50p 7415395 99p 82p BC183C 25p BU109 249p ZTX753 50p NE531N 1.36p Quick dissolving 2511 74LS TTL MEMORIES 254031 Iron Stand 1.75p 3300 16 65p 7415396 2.95p BU126 1.55p 6 amp type NE5435 2.500 E oungh to make 470nF Io 5607F 204032 87p BC1B3L 15p 4700 10 65p 2114 pis ask hole 1.95p 001 1 litre 1.696 Elements 741500 750 7415398 1 29p 254036 72p BC183LA 16p 8U204 249p Square with NE5445 32p 4700 16 95p 2532 4.25p NE555 22p o ETCH RESIST (State Iron) 2.059 741501 200 7415399 1 29p 66p BC183L8 l8p BU205 1 99p PW0111001 959 6BOnF 38p 2564 6.95p 154037 C240 Bits 29p 7415445 990 204400 19p BC183LC 23p BU206 2.16p PW0212001 99p NE556 65p TRANSFERS 1,F (1Omml 741502 2708 3 95p DIODES Not (Small) 85p P 1.300 NE558 1.89p 1 Thin lines 741503 29p 7415490 1 15p 254401 33p BC184 16p BU208 1.93p W0414001 POLYESTER 27161501 345p lines No3 (Mid, 85p 7415540 1 19p PWO616001 1.39p NE560 3.25p 1 Thick 250V RADIAL 741904 pia ask 254407 37p BC1848 19p BU226 445p 2764 8.99 1 bends Nob (Micro) 85p 7415541 1.45p 225p BC1B4C 24p BU3265 2.630 0344 52p NE565 180 3 Then 102801 7400 75p 741505 29p 4116 ask 254902 %52401X25 74L5640 2.50p pis N821 70p 25 amp type 5E566 1.49p 4 Thick bends Bits 10nF, 15nF 7401 24p 741508 29p 254903 2.380 BC1B6 290 610406 I 45p 4118 4.39p Metal clad with NE567 1.37p 5 OIL pads No5015ma111 85p 7402 290 741509 290 74L5641 2.50p 254904 246p BC187 29p BU407 1.58p 0823 92p 22n6 337E 4164 4.99p 4.07p pads No511Med1 850 254905 2.990 BC212 1130 BU408 1.49p N914 4p hole NE570 6 Transistor 477F, 68nF 7403 29p 741510 29p 6116 pls ask holes No52ILge1 B5p 1Bp BU409 1.65p N916 Sp 50111001 2.62p NE571 3 99p 7 Dots & 100nF 7p 7404 35p 74L511 35p CMOS 204906 3.090 BC212A 6810 1.950 NE55344 I 75p 801"edge SOLDER 125gms 7405 35p 741512 350 254907 3.42p BC212B 210 80500 3.560 04001 4p 502(7001 2.75p 150nF,200nF 10p RC4194 3.95p 18swg 2.950 MISC LOGIC IC's BC213 17p BU718S 433p 54002 41 20 K041400) 3.250 connectors 330nF,470nF 13p 7406 1 69p 741513 35p 4000 18p 204908 3.58p 22swq 3100 18p 54003 5p 50616001 4.100 RC4195 2.95p 9 Mixture 18p 7407 1 69p 741514 45p 4001 18p ADCOB04 pia ask 254909 315p 8C213A E430 632p 6807F BYW64 RC4558 44p Any sheet of 7408 35p 741520 290 4002 18p ADC0816 pis ask 255089 43p 8C2138 19p 1300 88p 04004 51 20 1,F 22p 0576477 7.95p above 35p 7409 35p 741521 290 4006 69p ADCO817 pis ask 255190 75p BC213C 24p 1310 88p 04005 6p 35A 41:10V 4509 PLUGS & 1.5,F 39p SN76003 345p GRADE ONE 7410 35p 74L522 29p 4007 25p 1001771 pis ask 255191 79p BC213L 15p MJ802 4.250 04006 61 2P 2.2,F 390 SN76013 3.45p GLASS PC8 SOCKETS 7411 350 741527 35p 4008 79p R02513LC 7.50p 255193 99P fiC2131A 16p MJ900 3.21p 54007 7p FEEDTHROUGH SN76023 3.45p SINGLE -SIDED 741528 4009 R02513UC 7.50p 83p BC213L8 19p MJ901 3.390 N4009 20p 1 nF 500V 350 7412 35P 29p 55p 205194 'D' Connectors 3p OPTO 5076033 3 45p 178 x 240mm HIGH VOLTAGE 7413 35p 741530 290 4010 29p SAA5000 4.05p 255245 46p BC213LC 23p MJ1000 2.760 04148 25 Way Solder 7.810 tap MJ1001 3.260 04150 1Bp 147204 1.99p 1.500 7414 55p 741532 pis ask 4011 22p 5A45010 205246 59p 8C214 1 Capacitors 420 x Male 60p 63p BC2148 22p MJ1800 3.79p 644448 22p any inc TA7205 1.20p 195mm enquire 7416 1 49p 74L533 29p 4012 29p SAA5012 7.81p 2N5247 Female 2.09p M12500 2.390 55400 120 specials see our 147222 1.75p 1 gyp 1 741537 29p 4013 SAA5020 5.950 65p BC714C 27p manyan Y types in 7417 49p 49p 205248 PCB Wire-Wrap 19p M12501 2.63p 55401 13p CAT TA7227 5.82p 420 x 245mm stock 7420 35p 741538 59p 4015 65p SAA5030 6.99p 255249 67p BC214L Male 1.60p 14p LED LAMPS TBA500 2.97p 2950 7421 35p 741540 390 4016 45p SAA5040 15.95p 205266 3.25p BC214LB 210 MJ2955 99p 55402 Female 2.090 R = Red TBA500(] 3.11p DALO ETCH TANT BEADS 7422 35p 741542 459 4017 69p SAA5041 15.95p 255401 57p 8C214LC 760 MJ3000 2.39p 55404 169 Covers 1,000 G - Green TBA510 RESIST PEN 741542 750 4018 SAA5050 895p 255415 1.36p BC300 59p MJ3001 2.63p N5406 113p 2.95p 1 35V 14p 7423 35p 69p Phono plugs 59p 19p Y = Yellow TBA5100 3.050 +spare nib 1.20p 12 35V top 7425 35p 741551 29p 4018 55p SAA5070 18.950 255416 1.73p 80301 MJ4502 4.25p 05407 51k. Red, Grn. 20p T34520 2.57p PHOTO 1 75p 05408 1 3035V 14p 7426 35p 741554 29p 4020 89p 8T26 19p 255447 29p BC302 59p MJE340 Large diffused Wt or Yell 15P 1.49p 4911 TBA5200 275p SENSITIVE PCB 47 35V 14p 7427 35p 741555 35p 4021 69p BT2B 1.190 255448 31p 8C303 59p MJE350 84102 R5D 9p Line Skts 150 8T95 99p 256449 2]p BC327 16p MJE2955 1.99p 04115 29p 16p TBA530 2.55p 1st Class Epoxy 6835V 14p 7428 35p 741573 45p 4022 69p G5D Chas Skt 1 160 51p T8A5300 2.760 Glass for better 1035V 14p 7430 35p 741574 59p 4023 39p 8197 990 255450 63p BC327A 19p MJE2955T 95p BÁ133 Y50 150 Dual Skt 0p 1.59p 360 TBA54O 2.72p results than 7432 95p 741575 45p 4024 69p 811595 2.27p 205451 BC327B 23p MJE3055 BA138 CluedQ Ski 400 2.2 35V 14p Small diffused TBA5400 2.74p spraying expose 4026 89p 811596 2.27p 255457 390 BC327C 25p MJE3055T 69p 136142 25p 3 3 35V 18p 7433 35p 741576 390 R3D 8p 2.27p 39p BC440 35p MPSA05 29p BÁ155 180 TBA550 3.25p to UV 4 7 16V 18p 7437 350 741578 45p 4027 45p 811597 255493 41 G3D 12p TBA5500 3.27p Single sided 4.7 35V 20p 7438 95p 741583 55p 4028 53p 811598 2.27p 255459 31p BC441 37p MPSA06 33p 84156 ZIF SOCKET V3D 12p TBA560C 2.87p 100 x 160 2 10p 7440 29p 741585 59p 4029 69p 6522 3.69p 205460 B3p BC460 38p MPSA10 59p 134157 28pP 6.525V 20p TBA570 2.37p 100 o 220 2.50P 4030 3911 65224 5.55p 255551 41p BC461 42p MPSA12 49p BA158 34P 24 pin 4 35p 6.635V 21p 7441 69p 741586 390 Micro(' l' x 114 91p MPSA13 49p BA159 38p TBA5700 2.48P 203 2.409 28 5.00p 1016V 18p 7442 58F 741590 35p 4031 1 35p 6532 6.45p 2N6121 BC547 le RIM 27p pin 49p 49p TDA1002 3.39p 233 x 220 5.20p 40 635p 1035V 27p 7444 65p 741592 45p 4032 89p 6821 1.99p 206122 93p BC550C 29p MPSA14 84182 GIM 29p 49p 84201 23p TDA1003 4.35p Double sided 15'10V 22P 7445 75p 741593 35p 4034 1.99P 6840 3.75p 2N6123 99P BC560C 29p MPSA20 VIM 29p 49p 29p TDA1004 P.01. 100 x 160 2.20P 1516V 30p 7446 75p 741595 55P 4035 69p 6845 649p 206124 1,01p BC070 31p MPSA42 134202 SWITCHES 1.030 MPSA43 48p BÁ316 27p Large clear TDA1004A 5.45p 100 a 200 2.80p 15.25V 32p 7447 65p 741996 75p 4036 2.69p 6847 6.49p 2N6125 BCY71 33p R5C 12p TDA1005 4.35p 203 x 114 2.200 1.09p 25p MPSA55 - 29p BA311 28p 22 6.3V 26p 7448 75p 7415107 asp 4038 1 19p 8154 plº ask 256126 BCY72 33p 31p G5C l7p T0A1010A 2.25+ 233' 220 590P TOGGLE (MIN) 7450 29p 7415109 45p 4040 59p 8155 pis ask 256129 99p 00124 299p MPSA56 BA318 22 16V 29p Y5C 17p TD41022 4950 Developer for SPST 59p 7451 290 7415112 a5p 4041 59p 8212 pis ask 2616130 050 130131 63p MPSA65 62p 56X13 21p 33 10V 30p Super bright TDA2002 3.25p above (do not SPDT 65p 7415113 390 4042 59p 8216 PIS ask 256131 1 23p 130132 630 MPSA66 65p 88105 65p 47'3V 14p 7453 29p TDA2003 3.25p use Sodium DPOT 74p 7415114 390 4044 59p 8224 pis ask 256132 1.090 BD135 380 MPSA70 49p BR109G 69p high efficiency 47 6.3V 340 7454 29p TDA2020 Hydroxide) DPOTC.OFF 90p 1 150 MPSA92 49p BY126 120 large (100 times 3.15p 7415122 59p 4045 1 19p 8226 pIs esk 2N6133 BD136 38p 47 16V 39p 7460 29p 2 4PDT 3 250 1.33p BD137 39p MPSA93 480 137127 14p brighter) TDA2030 2.85p 500m1 95p 100 3V 32p 7470 49p 74L5123 1 19p 4046 75p 280ACTC 3490 206134 CIRCLE 69 FOR FURTHER DETAILS.

30 ELECTRONICS & WIRELESS WORLD JULY 1984

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SC84 Micro computer The third module of John Adams' disc -based professional microcomputer for engineers and enthusiasts provides a c.r.t. display of more than 3000 text characters, 36000 picture elements, or a mixture of text and graphics.

A visual -display unit, v.d.u., memory doesn't appear to take up to the v.d.u. during flyback peri- passes information from a com- any space in the main memory ods - i.e. when the video is nat- by J. H. Adams puter to its operator. It consists of map, with the proviso that soft- urally suppressed. Unless done a display device -a monitor or a ware that sends information to carefully, selective blacking can tv - and digital circuits to con- the v.d.u. mustn't be in the mem- noticeably reduce display intens- trol an area of memory holding a ory segment switched out when ity; the second solution reduces representation of the image to be the v.d.u. is switched in, and the the rate at which characters can displayed. Data written into this penalty that v.d.u. access is be passed to the screen. memory from the computer is slowed down by extra switching Terminal -type or i/o -mapped read out for processing and com- software. Other problems with v.d.us appear to the c.p.u. as bination with control signals to memory -mapped v.d.us are the input/output channels, so their produce the necessary monitor extra circuits required to switch advantage is in not occupying any input signals. This being a vital address lines to the v. d. u. mem- system memory. Their disadvan- part of a computer, large-scale ory, the arbitration needed and tage is in circuit complexity. Cir- integrated circuits of varying the screen disturbance which can cuits must be provided for receiv- John Adams, with a B.Scand complexity have been produced occur when the c.p.u. accesses ing and interpreting commands M.Sc. from University College to simplify the design of v.d. u the memory. The problem of arbi- as well as data. For example the of North Wales, is head of the digital circuits. There are two tration is most relevant when i/o -mapped v.d.u. must recog- microprocessor division off fundamental types of v. d. u. cir- dynamic memory, with its need nize a request for the character at Graseby Dynamics Ltd. Prior cuit, memory -mapped and i/o - for orderly memory access, is a particular screen location (in- to working in industry he held mapped. used. As dynamic memory is cluding transfer of the screen various educational posts In a memory -mapped system, cheaper and as higher resolution coordinates - information im- during which he initiated the memory storing characters to be requires more and more memory, plicit in a memory -mapped teaching package `Starting displayed on the screen is part of this can lead to extra complexity access), or the need to clear the microelectronics'. This, his the system's addressable mem- or expense. With static memory it rest of the current display line and second series of articles for ory. The advantage of memory is simply a matter of giving the return the cursor or next -screen - Electronics and Wireless mapping is that the processor can c.p.u., which will after all control location pointer to the left-hand World, combines his interests make rapid transfers to and from the arbitration process, priority margin on receiving the carriage in education and engineering. the v.d.u. - as fast as its own in addressing and accessing return control character. It is In his spare time, John is a memory cycle - which for a v.d.u. memory. The disturbance common practice to pass data to keen classical organist. Z8OB means 300 000 characters occurs when the c.p.u. gains con- per second. Also, as the memory trol during an active -display is under processor control, it is period. The v.d.u. control cir- relatively easy to implement cuits take bytes from memory in unusual screen features such as an orderly manner and pass them scrolling the display left or down. on for processing into video infor- The main disadvantage is that the mation. When a c.p.u. cycle v. d. u. memory takes up memory occurs this is interrupted, the available for programs unless location addressed and the data paging is used and, as the screen on the bus lines being different resolution and hence the amount from that planned by the v.d.u. of memory required for a display controller. The result is speckling increases, less and less of the on the screen which, particularly addressable memory remains for during scrolling can almost obli- the program. terate the wanted information. Paging is a technique where a Common solutions to this are to block of memory can be tempor- force the video output to the arily switched in place of another. `black' state during c.p.u. Use of paging means that v.d.u. accesses or to only allow access

ELECTRONICS & WIRELESS WORLD JULY 1984 31

www.americanradiohistory.com SPECIAL FEATURE

A13 A15 MREQVDUSEL

VDU decoder CPU address Ca bus T4,- 0V WR Address Internal 'A' bus multiplexer

(Internal address W M' bus

6Kbyte video Device Select 0 SEL CRT controller read /write ;$elect 1-3 decoder memory

Character row address

HSYNC daPtlusfh Data bus Buffer VSYNC

RD

Parallel Dot data Display Data Character Video to VIDEO blanking latch generator control serial

Character clock :6

Dot clock Controller clock

Designed chiefly for fast clear an i/o mapped v.d.u. in serial monochrome one for dense char- dot patterns corresponding to high -density text display, the form, which restricts the charac- acter display, where typically characters placed in the v.d.u. monochrome v.d.u. section of ter rate to about 1000/s. Proces- close-up use renders a colour memory), and skewed video con- SC84 is memory mapped and sor i/o operations are not so var- monitor tiresome to read unless trol lines, i.e. signals which can uses the pipelining technique. ious or fast as memory ones, perfectly adjusted, and a full be delayed internally by one or video making something of a bottle- colour output with the option of Output is separete and two characters periods to allow a sync. signals in either polarity. neck of the i/o channel, however character formation. the possible division of process- technique called 'pipelining' to be ing between the main c.p.u. and Controllers used. Pipelining' is a technique the v.d.u. circuits can lead to a used in complex v. d. us whereby reasonably fast system. Also, as The Hitatchi HD6845S used in v. d. u. memory and character gene- v.d.u. memory only has one con- this design (until recently num- rator outputs are latched in sync- troller it can be dynamic without bered HD46505S) is a developed hronism with the character display 6845 any problems arising. form of the popular v.d.u. rate. Whatever the speed of It should now be apparent that controller. Its advantage to the there are pros and con's to both memory accesses, providing they computer designer is flexibility, are each shorter than one charac- methods. There are further rea- virtually all design parameters sons affecting the choice. Word - ter display period (500ns in this (e.g. characters per line, lines per system), data passes, or is star, a popular word-processing etc.) program, is an example of soft- screen, sync. pulse length 'piped' synchronously through Fig.1. SC84's monochrome ware which can work well with being stored in registers loaded the v.d.u. Being able to skew the v.d.u. circuit, right, uses an either system but which shows off by the c.p.u. rather than being display and cursor enabling sys- enhanced version of the 6845 its best features when modified fixed. In the Hitatchi version tems means that it is easier to c.r.t. controller with light -pen for use with a memory -mapped capabilities of these registers are ensure that control and data v.d .u. My solution is to use both register and interlaced video extended; these capabilities are information appear together at facility to give 32 lines of 96 systems - a memory -mapped used in this design so it is import- characters and up to 192 by display for monochrome charac- the end of the 'pipeline' (see the ant to use the specified device. timing diagram). The controller 192 pixels for graphics. Using ters and medium resolution gra- While it can be used for graphic phics and an i/o system for high - provides a register for positioning an eprom character generator displays, its primary intent is as a is cheaper than using a resolution colour graphics*. This a cursor which can be made to -display controller and proprietary rom and allows prompts use of two monitors -a character flash, a register for use with a it has control lines reprogramming. Switching is to this end light pen and a facility for inter- * John Adams is currently working on the which can be fed to a character included to relocate the v.d.u. high -resolution colour system which we laced video. Together with multi - section for experimentation. plan to describe in a future article - Ed. generator (a rom which produces 32 ELECTRONICS & WIRELESS WORLD JULY 1984

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ELECTRONICS & WIRELESS WORLD JULY 1984 33

www.americanradiohistory.com SPECIAL FEATURE

plexers selecting memory, c.p.u. for use in raster -scanning sys- the space (two dot rows) between or controller lines, some high- tems, i.e. with a normal, televi- adjacent display lines. The two - speed logic too fast to build into sion -like display where the dot horizontal space is used by the nmos controller, and memory cathode-ray tube spot writes lines lower-case letters with descen- it forms the character v.d.u. across the screen from left to ders (g, p, q, etc.). The fastest The NEC µPD7220 is one of a right while being progressively event in the v.d.u. is sending of a new generation of graphics con- swept down the screen. This pixel to the display and a signal at troller designed for i/o mapping means that one character is not this frequency is generated by the but offering a degree of internal completely drawn on the screen 12MHz dot-clock oscillator, complexity which overcomes before the next. As the spot (IC319). This signal is divided by many of the objections to i/o moves across the screen, succes- six in a programmable divider to mapping. Designed to control up sive character codes are taken give a signal running at the char- to 256K words (1 word -16 bits ) from v.d.u. memory and just one acter -display frequency, the char- of dynamic memory, it appears to row of dots from each of the acter clock. This division, and all the c.p.u. as two i/o ports and corresponding character pattern operations at the dot frequency, is optionally a d.m.a. channel. is taken from the character gener- done outside the controller as the Using i/o ports for commands and ator rom and displayed on the frequencies involved are too high d.m.a. for data, rapid access to v.d.u. At the start of the next for most technology used in the v.d.u. memory is possible. For c. r. t. line the v. d. u. memory add- HD6845S. Note that the charac- graphic functions such as shape ress reverts to the same value as ter generator is an eprom. Not drawing or filling areas, the 7220 that of the start of the line but a only are they cheaper than pro- can be given parameters and then different row of dots is selected prietary character generator roms commanded to draw - which it can from the character generator. but they allow you to change the do at over one million picture ele- Only when the last dot row has character set to suit your own ments (pixels) per second with- been drawn is the memory add- requirements. Even the number out further c.p.u. involvement. ress allowed to step to the next of dots making up a character can Other internal features are full area of v.d.u. memory. The num- be altered, up to an eight -by -16 refresh, zooming (expansion of ber of characters on line and the matrix, but this is rather adv- one part of the display to fill the number of dot rows, or rasters, is anced work. entire screen) and the option of set by loading values into the con- Circuit IC319 is a four -bit pro- flash -free memory update (i.e. troller when the Z80 is initializing grammable counter. It provides a memory access during flyback the system. These factors control 'carry' pulse at pin 15 as it passes period only). Details of the gra- v.d.u. memory address lines through its maximum count value phics display and of programming M0_1, and row-address lines R. - binary 1111 - and this signal techniques for both controllers In this system displayed char- loads the binary value on pins six VDU timing. Synchronization will appear in a later article. acters are six dots wide by nine in this v.d.u. using `pipelining' to three instead of allowing the (see text) is critical and Figure 1 shows the character dots high; this pattern includes counter to count on to zero on the depends on two signals - v.d.u. circuit. As most c.r.t. con- the space (one dot column) next dot clock pulse. This value is NOT CARRY and the dot clock. trollers, the HD6845S is designed between adjacent characters and binary 1010 - denary 10 - so the counter counts through six states, binary 1010 to 1111, before Dot clock ((1C307pin 6 ) repeating. Divider output C pro- LJ L U vides the character clock signal - u fed to the controller. An inverted Character clock ( IC318,pin12) ) carry pulse is used to provide a clocking and/or loading signal

I throughout the logic outside the CARRY (IC318, pin 7) controller. Synchronization is extremely important. As one can see from } Display cycle begins Load shift reo. with char. Of Load shift reg.with char 1,4 the timing diagram there are Character 0 latched character 1 latched character 2 latched many delays between the rising 'M' address lines HD6845 edge of the character clock initiat- Address 0 Address 1 Address 2 ing the addressing sequence and the production of a dot pattern at R/WM outputs the output of the character gener- VDU R/WM data 0 VDU R/M dotal VDU ator, and between this point and the coming of those dots and con- 1[315 matched data) outputs trol signals for display blanking, VDU R/WM data O VDU R/WM data 1 etc. , from the controller. The timing diagram is to scale and Character generator outputs incorporates the worst -case

Char gen. data O delays specified for the i.cs. Two signals used to synchronize the Shift register cutput (1Cj07,pin 13) system are rising edges of dot clock and carry signal. To cope 04000 x Obi i011iDO ' ' DCIPDOD with delays between the con- X '- don't care 0/0'- character zero / etc troller generating an M -line add- Display enable timing 11C3J7, pin 9) bit zero ress and the output of v.d.u. V memory settling - a process Skewed DISPTMG signal Display enabled which might take up to two-thirds becomes active of a character period - memory Continued on page 64 34 ELECTRONICS & WIRELESS WORLD JULY 1984

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

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by D.C.A. Read, Improving colour B.Sc. (Eng), M.I.E.E. television decoding Viewing tv pictures at work and at home over several years using various decoding methods, David Read found the comb filter method an undoubted improvement with a 26in screen. But inprovements to other video processing blocks are needed to fully appreciate the picture. This postscript recommends an acoustic surface wave filter for i.f. use and discusses other picture enhancement techniques. Most of the signal -processing sion carrier minus subcarrier, low noise, high dynamic range improvements that the home 35.07mHz), only 0.5 to 2dB mosfet stages and include the first viewer can make - to PAL down. These will provide the best i.f. bandpass coupling stage and decoding, RGB drive, and wide - overall performance with modi- driver amplifier for the s.a.w. fil- band comb filtering - have been fied LC filters used before the ter. The tuner i.f. board then covered in this series of articles. chroma decoder. However, the need only comprise a front-end One remaining area for investiga- performance is not good enough tuner, s.a.w. filter and the inte- tion is the tuner/i.f. strip. to justify the Fig.34 comb filter grated i.f. amplifier demodulator Although the ten -years old design circuit approach although a much TDA3541 together with a few dis- originally described in these improved picture can be obtained crete components (ref .11). pages (1975, Oct -Dec) is still in with the alternative LC networks use and gives good results, parti- shown last month. This is Design of high-grade receiver cularly with extended comb filter achieved by using the Fig.77 cir Fig.90. Board contains PAL methods of PAL decoding, it is cuit for the luminance path (Figs For really high quality sound and modifier and comb luminance felt that the design and circuit 74 and 76 show amplitude and vision to feed into a comb -type filter of Fig.34 together with board cannot be recommended group -delay performance) and decode, the B.B.C. have the optional sync separator for building today - with dis- the Fig.81 circuit for the chroma designed a u.h.f. tv receiver type sandcastle pulse generator crete inductors providing all the path (Figs 79 and 80 give ampli- RCI/511, being manufactured and extra field blanking of i.f. bandwidth shaping and post - tude and delay performance).The under licence by SPT Video Fig.36. demodulator group-delay equali- chroma circuit can be modified to zation. It has been remarked that advantage as shown in Fig.93 the board looks more like a Man- (See Figs 94 and 95 for amplitude hattan sky line! There is also a and delay performance). The daunting setting -up procedure. modified chroma filter will offer a Recently, both Signal Tech- better chroma bandwidth and nology and Mullard have been reduced 7.8kHz twitter at the manufacturing some excellent chroma transitions if it is adjusted surface acoustic wave i.f. filters. to match the s .a.w. filter The SD155 from signal Technol- response (chroma sideband ogy is flat at frequencies above fs, symmetry optimized), as was and has a sound shelf of -16dB similarly indicated in Fig.82. though probably not sufficiently When the s.a.w. filter with the down for a single -chip demodula- performance of Fig. 96 is in use, tor e.g. TDA 3541, though an LC e.g. the SD155, the best chroma trap to provide an extra 10dB filter is the gaussian band-pass could readily be added. Over the filter of Fig.34. For this Fig.52 retailers' counter this could cost shows the amplitude response £40 to £50 currently, but it is and Fig.53 the group delay per- hoped that cable -head companies formance, with Fig.52(b) indicat- and set manufacturers will start ing the clean chroma transitions to use these better quality filters that can be obtained. and the price will reduce. Mullard are expected to intro- Some of the better filters, for duce two new tuners .later this example Signal Technology's year, the U343 for potentiometer SY155 and RW153P have the sub - tuning and the U344 for use with a carrier equivalent frequency (vi- frequency synthesizer. These use ELECTRONICS & WIRELESS WORLD JULY 1984 37

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Sound From fsc carrier sound trap see Fig 81 22p 1 Chroma out 10 Ro_ 10n to e.g. Pin 3 1k TDA3561A 150p

-20 820 ç 42y22

OV 30 - Fig.93. Circuit of modified chroma -path filter when using -40 4 6 8 10 the betteri.f. s.a.w. filter. FREQUENCY (MHz) Subcarrier (equivalent frequency 35.067MHz) is only 300 0.5 to 2dB down. Using preferred values 10

.200 Scale up fron 200 ns 1111/FAM á g 100 2 á BIM á 0 0 4 6 8 10 30 3111111111 FREQUENCY (MHz) Fig .100. Resulting picture improvement with scan -velocity off Errors caused by rounding and on (screen photographs taken from a Mullard report). components of Fig.87 (bottom 4 tsc 8 10 circuit) to preferred values are FREQUENCY (MHz) switches which control a synthe- 300 shown by the group delay Fig.94. Amplitude performance siser; a rear D -plug enables Ro 75n response above (Fig.88). of the chroma path filter. remote control. Details of the } 200 internal operation are shown in a Ro = 75n Limited. This unit has a perform- ance specification of Fig.97; the notes on this block - Two video outputs at 75Q: diagram explain the functions. á100 amplitude response ±1dB to 5.5MHz. Other methods of picture enchance- balanced and unbalanced ment 4 tsc 6 8 10 - FREQUENCY sound outputs: harmonic dis (MHz) l tortion 0.5% MAX. There are excellent picture Fig.95. Group delay response Input step rise Half amplitude duration u.h.f. coverage: channels 20- enhancers that rely on picture of the high-pass chromafilter. time 200ns of input pulse 200ns - overshoot 0.6% overshoot 1.1 70 storage and can provide both hori- Group delay ripple and other - differential phase and gain: 4° zontal and vertical aperture cor- techniques are needed to stop losses in performance caused and 4% max, 2° and 2% typi rection. By recycling the informa- cumulative recycling and thus by using preferred capicitor cally. tion taken from the picture store prevent excessive blur. values are shown in these Physically, it is a 2U high, full bay with new pictures as they arrive, For the domestic receiver, a pulse -and -step test results width unit. Channel setting (tun- noise reduction is achieved. But simple enhancement technique is (Fig.89). ing) is by front-panel thumbwheel on movement, zonal adaptive to modulate the line scan velocity Fig.91. Alternative self-contained decoder board (Fig. 34 & 36 Fig. 92. Component location for PAL modifier comb filter board. It circuits not used) incorporates TDA3561A with the luminance is useful to check the coil bases with the board before winding notch filter of Fig.77 and the chroma high-pass filter of Fig.81, any coils, particularly the center -tapped ones. Chip provides hard -wired at the p.c. board edges. Board also has copper tracks additionally the 2fec feed required by the PAL modifier in Fig.34. laid out for RGB output stages, if needed for video processing The sandcastle pulse to the TDA3561A can be supplied from the improvement, similar to that in the TX10 receiver (Fig. 41, May TDA2591/2/3. These two signals may already be available in issue). Boards available from? existing receiver designs, but check that it is a 2f,c locked oscillator if this signal is to be extracted.

Set for max chroma at TP, and min 78k at transitions Field (ITS) blanking e, JJ Dr Space far on -hoard Modifier gmn .0n-81 rd regulator T/

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2fscphase -- -

Set f1 15-625kHz

2 links for 180° 2fs, phase

Carrier balance y on MC1596

Set 4433MHz Adaptive notch Link for isolating Link for isolating with fet on threshold lam fitter output lum. filter input

38 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com 10 Input

- fSC -200

--10 - -100 Balanced c Balanced 50n output, 50 n input e.g when usina Jc if used Mk. 541 -0 O oa- O

S0155 --100 Ou put Loss = 22.5dB/ on leads sample 1 View

FREQUENCY I Hz) Fig.96. Amplitude and group -601 200 delay performance of s.a.w. 28 30 32 34 36 38 40 42 46 filter recently introduced by Fig. 97. Block diagram of the 335MHz e fsc 39.5MHz BBC u.h.f. tv sound carrier vision carrier Signal Technology. -designed receiver, RC1/511, giving outputs of 1 volt composite video and good quality sound.

100kHz-N, 1dB 1dB -6MHz- 25dBr 1 34.75MHz sound ^ min. T 6dB 40dB gain 40.75MHz vision (a.g.c. with / 35.35 42 /(to suit synth.) long-tailed uhf. \pair Corner i f input ) U321 tuner I re. f. test O ( Mullard ) i.f.bandpass Sound saw. Low Z output trap

Channel 2 3 r.f. a.g.c. f ag select Phase b .d. shift/set humbwheel a.f.c. switches synth- Mix esizer To remove Remote select channel offsets Headphone (Vc.o. pulling Sound carrier output 34 75MHz ± 50kHz max.) 40.75MHz O vision 6MHz Phase (low phase carrier (true intercarrier) shift/set shift) C W Sound r demod Carrier Low Z line f B.W. 1h MHz L i miter 6MHz balanced centred on output vision carrier Det intercarrier

(allows 0 noise through 1

6MHz trap -25dB

Video Signal i.f Vision Group delay demodulator equalizer, operating between 4.5 & 5.5MHz Gated a g.c

( black level sync 4 sampled sep Back porch -I I-- 4066 f.e.t gates L -> Carrieri.f. *I-

Wideband a.g.c. (peak det) Active filters optimized for aircraft flutter or aerial signal flutter due to movement of narrow beam high gain aerials

ELECTRONICS & WIRELESS WORLD JULY 1984 39

www.americanradiohistory.com TELEVISION

Readers of this series puzzled by Parts list for Fig.34,36 22k 84,45,80 Potentiometers (Cermet) the numbering of component one -line comb filter circuits. 12k 41, 49, 69 Value Circuit reference 20k 43(use 2 x 10k or 18k if 50052 24 references on page 33 of the May Capacitors. Polystyrene ±2 % 125V necessary) 1k 32 installment may be reassured to (Suflex, Salford, Lemco) 15k 44 5k 42,89 know that it originated from the 2.7k 48 10k 87 maker's service sheet and were 2.2k 50, 61, 62 100k 76 Value (F)Circuit reference 1.5k 52 50k 71 not shown on the circuit diagram. 220p 13, 7, 24, 36 2.2M' 60 Eire carbon ±5 % 0.33W The BC337s of Fig.41 are 39p 5 1.8M' 59 Eire carbon ±5% 0.33W transistors 653, 652 & 651 in the 56p 6 1.2k 67 620p 18 68,55 & 82k Values determined by DL1 text, the BF392s are 659, 658 100p 51,39 120k' 70 Mullard MR30 metal film or Impedance 657, and resistors 665, 664 & 663 680p 19 equivalent ±5 % 0.25W are the 22k pull-up components at 150p 20 22052 53,56 Zo 752 800 -1 kQ using LC the BF392 bases. Also on that 82p 26, 23 47k 58, 78 network 270p 25 2202 72 2202 page, the resistor referred to in 27p 34,35 47 51 line three, column three, should 62p 37 1.6k to pin 5 MC796 (Fig.34) from R6 150Q 1.6k2 4404 (2X 220) be 2.7k and not 2.74 In Fig.42, 4.2n 46 ± 12V rail (component ref. R7 15052 1.6k42 4402(2x220) omitted from circuit) R9 1202 the annotation `Fig.34' should R2andR can besetasa RD R11 22052 82052 2202 have read Fig.41. The author also Disc ceramic or red/blue cap. potential divider to suit higher R,7 6852 1502 682 asks us to point out that in Fig.40 10n 4,8,12,16,21,45,48 video input levels. If high Z in R19 1kQ 2.7k2 1kQ the chroma input burst should be 1n 28,29,33 required omit R2 and set R0 to R20 51052 1.5kQ 5102 100n 32 4702 (parasitic oscillation C9 1mF 150mV rather than the 250mV stopper) shown at pin3 of the i.e. The right-hand ordinate on Polyester metallized ± 10% 100 or Fig.86 62, was 250V (Mullard type 344) (page June) 6.8n 40 inadvertently cropped, and should Circuit reference Turns 470n 42 Value Neosid Toko of course be labelled with 270n 53 E2 attenuation in dB. Observant 1 334 Set for max, chroma & 37 55 readers will have noticed that 2 234 min.7.8kHzattransitions 34 42 Tantalum ±20% (Union Carbide or 3 5.44 15 18 Fig.60 was a repeat of Fig.69; the RE components) 4 10.5µ Set for max. chroma, not critical 21 27 correct figure appears in this 30µ10V 1,2 5 104 PaintonorSigmachoke 224 15V 3,17,31,30,22,47,55 article. In Fig.24 (page 56 6 613 Set tonotchfsc. 16 21 22µ10V 10 7 9.7 or January) please substitute 200ns 4.7µ25V 44 104 Painton or for the 2001.ts shown. Sigma choke 20; 26 8' 14.34 resonate topL9to4.07MHzone 13TBIFILOR 16TBIFILOR Electrolytic (Eire, Mullard or 9' 2u4µ end of C18 removed. Resonate (13.0.13) (16.0.16) equivalent) L9 with C,8 connected & short 10 13 1m6.3V 27 the outer pins of L8 together. 10' 16.64 Disconnect output end of L10, 14BIFILOR 18TBIFILOR series resonate the remaining (14.0.14) (17.0.17) Transistors half -coil with the 680pF at Type Circuit reference 2.93MHz (or use wider signal- 2N3904 BG239 1,3,8,9,10,11,12 bar corner on i.t.s.). 2N3906 2, 4, 6, 18, 5, 18 11 3.84 not 341 -las shown in circuit. 13; 16 or BC309 (reference missing from Resonate at 2f,0. the circuit: transistor 12 5µ1µ Set for filter cut-off. - Not critical. 15 18 with R36, 38), 13, 14, 15, 13,14 224 PaintonorSigmachoke 16,17 15 150µ 154 Painton or Sigma choke orVN0616L, or VN2222L, TR 19 (f.e.t.) or M991 BD/C, or 1167BD 'It is best to setup A and B group -delay equalizer sections in isolation, i.e. no other equalizer or filter component in the circuit; thus check each stage of the f liter and equalizer one section at a time. Integrated circuits L9 and measured across outer pin i.e. total inductance. MC796, MC1496 or MC1596 IC2 L10 TDA2590/1 /2/3 200 IC, TDA2593 in the current I.C. 180 Toko 10k -series coil assembly Neosid E2 coil assembly If used+12V regulator µA7812 160

Diodes 140 Component suppliers BZY88C6V2 D D4 BZY88 C4V3 D5 ._120 1N916 D, a.100 sc¢ i 1. Surface wave filters ().§r.e Signal Technology Ltd, Crompton Delay lines 80 DL, Best to make the descrete LC 4Qci- Road, Groundwell Industrial Qe r network Z022052 or see text for 60 Estate, Swindon. Wilts. alterations. Tel: 0793-726666 ex. 230. DL2 DL60 or DL700 not critical. Observe 40 R,9 and R28 suit Z0 of line. See table 20 Mullard Ltd, - Use 4Ca415.g 7 r.-6125mO,mm.we , Resistors. Mullard MR25 metal film 0- Torrington Place, London WC2. T 0.4W or metal film ±5% ±2% equivalent 70 90 10 30 50 70 90 Tel: 580-6633. 0.2W. 10 30 50 TURNS 30 Delay lines. Value( Q) Circuit reference Manor Supplies, 172 West End 4.7k 1, 3, 57 Toko Lane, London NW3. 47052 12,16,31,33,81 24 Tel: 794-8751. 13k52 10 10kQ 13,15,47,63,74 ,18 5602 21,18,28 Future Films 15052 23,37 Leamington Street, London W 1. 1k 22,4,5,46 12 6802 8,73,36 Tel: 437-1892. 27k 14, 85 10052 83,34,64,65 6 Coil formers 3.3k 82, 38, 86,88, 90, 66, 79 Cirkit (Ambit), 200 N.Service 100k 26,40 o 33k 29, 30, 54, 75 (note R20 was 5 15 25 35 45 0 10 20 30 40 Road, Brentwood, Essex. 22k, R30 was 18k using 33k Tel: 0277 231616. improves modifier balance) TURNS TURNS

40 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com in relation to transitions in the Fig. 98. Block diagram Timing delay adjustments ensure increasing video signal. A pair of video transition corresponds with describing a method of scan velocity modulation four -turn coils built into the scan -velocity modulation to scanning yoke and placed in the Chroma improve picture sharpness. high pass line -scan coil plane provides line or band pass aperture modulation of the Decoder filter videoRG dBrove (a) Luminance scanning field. A restricted spec- I transition trum of the luminance signal (in / A el,m Luminance I the range 2 to 3.5MHz) is ampli- notch ce __ High pass / fied, amplitude -limited and used low pass Coil Composite differenhator hDer Limiter drive to drive the extra coils in the scan deo or (b) entering band pass filter amplifier Signal yoke. The block diagram is shown limiter in Fig.98. The additional circuit feeding these coils need only con- sist of a simple CR differentiator, Fig.102. Deflection field Picture enhancement tech- 3. Fischer, T. Digital v.l.s.i breeds next in tube neck back-to-back diode limiter and generation tv receivers. Electronics 11 class B output amplifying transis- niques and various methods of Aug. 1981 aperture correction can have 4. Reitmeier, G.A. "The Effects of analog I Resulting tors. The waveforms of the sys- filtering on the picture quality of compo- transition tem are as shown in Fig.99 and adverse effects - multiple images nent digital television systems. SMP1'E B enhancement the display picture shown in and movement blur - viewers Journal Oct. 1981. (- at picture tube have said picture appears 5. Auty, Read & Roe, Colour picture face Fig.100 illustrates `before and that the improvement using simple analogue comb as if looked at through speckled filters. BBC Engineering Dec.1977 no.108 after' the application (screen 5 5MHz glass. Also if the noise spectrum pp.28-33. Also SMPTE Journal Oct.1978 photograph taken from a Mullard vol.87. w Spectral energy publication). lies in the 2-3MHz region, noise 6. Clarke, C.K.P. Digital standards conver- in the transition on the final picture can be sion: Comparison of colour methods. BBC E butdue to band- Picture enhancement with colour - After viewing many Research Department Report 1972/6. o_ width and RGB increased. 7. J. Sabatier and F. Kretz. Sampling the drive stew rate transient improvement circuit live programmes it was concluded components of 625 -Line television signals. limitations this that it is better to get back more of EBU Review, no.171 Oct.1978. 2 to 3.5 does not reach It is possible to improve the R G B 8. G.D. Roe and D.C. Read Patent 2256/77 the tube face the signal as originally generated Comb Filters for PAL Coders and Decod- MHO signal where the chroma band- at source. ers. Nov.1977, UK patent 2256/77. Suitable section width has been restricted to supp- 9. C.K.Y. Clarke, 1982. High Quality of spectrum Decoding for PAL inputs to digital YUV stu- to operate ress crosscolour, resulting in dios. BBC Research Department Report scan velocity mod. risetimes in excess of 500ms. On 1982/12. 10. P.G.J. Barten and J. Kaashoek. 30AX improving (speeding up) the rise - REFERENCES Self -aligning 110° In -line Colour TV Fig.99. Example of waveforms times, care has to be taken not to Display. Mullard Technical Note 119. occurring in a scan -velocity exaggerate the crosstalk (e.g. 1. Drewery, J.O. Filtering of Luminance 11. PJ.M. Sijbers and J. Zeelen (Philips modulation circuit. and Chrominance Signals to Avoid Cross - Technical). One i.c. and a SAW -filter in a increased UN 12.5Hz flicker). colour in PAL Colour System. BBC high-performance vision i.f. channel. Elec- Fig.101. Functional block By using a switched equalizer Research Department Report 975/36. See tronic Components and Applications. also BBC Engineering 1976. vol.5, no.1. Nov.1982. diagram of an available i.c. for under the control of the differen- 2. Mullard Limited, Mullard House, Tor- 12. A. Oliphant, 1982. Weston Clean PAL colour transient improvement tiated luminance signal (to mini- rington Place, London WC1E 7HD. Scan BBC Research Department Report. (taken from the data sheets for Velocity Modulation for the 30AX Tube. 1980/ 1. mize cross -colour increase), the the TDA456O). U and V i.e. B -Y and R -Y chrominance steps can be improved. This is possible Fine adjustment because of the good correlation Switching voltage

led = 0, 90, 180, 270nst I l ed =45ns) ' between the luminance and S1 Vp 1+12V1 chrominance picture informa- 15 13 14 10 tion. An i.c. to improve colour transients is the Mullard TDA4560 Threshold TDA4560, shown in Fig.101. switch This uses the differentiated input R -Y and B -Y chroma to con- trol and chroma delay switching. Clamping 7 ogons j.90ns 45ns 12 td =90ns Y output Luminance input signal -i I circuit effect of using such tech- Gyrator delay cells The (Y) 33(ín tdl niques is for a chroma positive - going transition as seen in -II Velocity modulation output Itd-90051 Switching LDifferenhating 8 stage .0+ and storage R Y output stage Input Colour difference Integrator input signals stage

Chroma transition 1 pulsefarmer) Differentiating stage OF Switching Subjectively and storage B Y output improved time stage rise B Output Y l Typical 6 9 output transitions 1 470p 470p 330p . 150ns

Fig.102. Waveforms showing chroma edge enhancement by delay switching. ELECTRONICS & WIRELESS WORLD JULY 1984 41

www.americanradiohistory.com INVERTERS EX STOCK TRANSFORMERS 100W £59.27 MAINS ISOLATORS 5025V or 25-0-25V 30/15V or 15-0-15V 250W £154.93 Pri/Sec 120Vx2 2x25V Tap Seca. 5, 7, 8, 2.15V Tap Sec. Volts 500W £239.50 VA Price P&P 10, 13, 15, 17, 20, 25, 30, 3. 4, 5, 6, 8, 9, 10, 12, 15, 1000W £350.00 20 5.82 1.60 33, 40 20-0-20 or 25 0-25V 18, 20, 24. 30 or 15-0-15V 2000W £709.00 60 9.49 1.80 50V 25V Price P&P 30V 15V Price P&P CONSTANT VOLTAGE 100 11.08 2.00 0. 1 4.13 1.40 0.5A 1 3.19 1.20 TRANSFORMER 1% 200 15.89 2.25 2 5.03 1.50 1 2 4.32 1.40 Spike -tree stable mains 250 18.97 2.64 4 8.69 1.84 2 A 4 6.99 1.60 A 250VÁ £172.40 350 23.47 2.10 6 10.36 1.90 3 M 6 8.10 1.85 M 500VA 500 2913 2.95 8 14.10 2.12 4 P 8 9.67 1.90 £196.69 P 1KVA 750 4128 3.70 12 18.01 2.20 5 S 10 11.95 2.00 £338.40 S 2KVA 1000 53.00 4.00 16 24.52 2.70 6 12 13.52 2.00 £594.50 3KVA £957.73 1500 60.37 4.70 1 20 3023 3.00 8 16 18.10 2.26 10 4KVA £1266.00 2000 6217 5.10 1 24 36.18 3.20 20 20.58 2.26 3000 115.35 OA 12 24 2320 2.50 5KVA £1531.00 6000 203.65 OA 15 30 26.60 3.00 6KVA £1743.00 6010V 115 or 240V sec only. or 30-0-30V 20 40 35.64 4.83 7.5KVA £2073.00 Pri 2x1211N. 2x30V Tap AUTOS 10KVA £3347.00 400/440V ISOLATORS Secs 6, 8, 12, 10, 16, 18, 105, 115, 220, 230, 240V AVOs & MEGGERs 400/440 to 200240V CT 20, 24, 30. 36, 40, 48, 60, For step-up or down 8Mk5(latest) £140.70 VA Price P&P 24-0-24 or 30-0-30V. VA Price P&P 73 £78.90 60 950 1 80 60V 30V Price P&P 80 4.84 1.40 MMS Minor £52.00 10 11.08 2.00 0.5 1 4.70 1.50 150 6.48 1.60 DA212 LCD £98.60 200 15.68 225 1 2 7.15 1.50 350 11.84 2.00 DA116 LCD £154.50 250 18.97 2.40 2 A 4 920 1.90 500 13.30 2.24 DA117 Autorange 350 23.41 2.70 3 M 6 13.31 2.00 1000 2414 2.80 LCD £157.00 500 2913 2.95 4 p 8 15.15 2.20 1500 28.17 3.20 Meggger Gen £116.40 1000 52.98 4.00 5 10 19.16 2.20 s 2000 42.14 4.00 Batt Megger £85.50 2000 8217 5.00 6 12 21.86 2.65 3000 71.64 4.80 AVO 2001 £91.60 3000 115.31 OA 8 16 30.12 300 5000 108.30 OA P&P £2 VAT 15% 6000 228.75 OA 10 20 35.76 3.30 CASED AUTOS 12 24 4122 3.50 BURGLAR ALARM 24í12V or 12-0-12V 240V to 115V USA skts. Ultrasonic, looks like a x MINIATURES VA Price P&P 2 12V Secs. Pri. 240V speaker, £99.00 +VAT tri 24V Price P&P 20 721 1.50 The Microvalue Group dealers shown 80 9.35 1.60 0.3A 15 2.41 90 Sec V A Pri P&P ELECTROSIL TM 5% 150 12.10 1.90 below represent part of the Gemini network. 5 3.19 1.20 3-0-3 2A 3.11 .90 RESISTORS £1/100 250 14.73 2.00 1 6x2 1Ax2 3.45 1.20 425 1.20 12, 20, 33, 47, 75, 390, 430, For expert advice and full details on the 9-0-9 .1 2.59 90 500 24.14 2.20 2 4.91 1.60 510f/, 560, 1k, 1k1, 1k3, 2.41 90 1000 33.74 2.80 3 7.69 1.60 9x2 33x2 1k6, 1k8, 2k, 3k, 3k9, 15k, Gemini System, contact your nearest dealer 2000 60.47 4.50 A 4 8.98 1.60 8,9x2 .5x2 3.361.20 16k, 24k, 27k, 39k, 56k, 1.40 today. 1 M 5 9.82 1.80 8,9x2 1Ax2 421 SPECIAL OFFERS 82k, 100k, 110k, 120k,

1 15x2 2.41 .90 p 6 10.89 1.90 2Ax2 Price P&P 130k, 150k, 200k, 220k, 1 12-0-12 .05 3.11 90 S 8 12.97 2.12 1000 line to 270k, 300k. P&P 20p. AMERSHAM COMPUTER CENTRE LTD 2 10 20x2 3x2 3.39120 17.46 2.44 4Q 10W 3.00 90 18 Woodside Road, Amersham, Bucks HP7 OBH 30 15 21.69 2.64 20x2 .15x2 1.50 .50 25-0-25V BRIDGE RECTIFIERS 60 30 44.45 OA 20,12,0 93Aor50V6A 7.001.50 400V1A .32 Tel: 02403 22307 Telex: 837788 83 41 12,20 .9 4.13 1.30 5110 4.50 PLEASE ADD 15% 200V2A .45 15,20-2 1Ax2 560 1.60 VAT ALLPAPITEMS TOAFT 100V35A £2.60 BUSINESS & LEISURE LTD 96/48V. Pri 2 x 120V 15,27x2.5x2 4.83140 ER 500V 12.5A £3.40 Seca 2 x 36/48V 15,27x2.1A3(2 7.30 1.60 16 The Square, Kenilworth, Warwickshire CV8 1 EC 7216- V MAW Price P&P Tel: 0926 512127 TOROIDALS ARRIE ELECTRONICS 0.5A 1 5.31 1.20 LTD 2 A 4 14.69 2.20 Wound to spec. it 211, Stratford Workshops CENTIFLEX MICROSYSTEMS LTD 3 M 6 17.79 2.40 3OVA to 5KVA rford Unit 6, Perry Road, Staple Tye, Harlow, 5 P 10 3223 3.20 Road, London E15 2SP 6 S 12 40.36 3.50 EXPORT ENQUIRIES el: 01-555 0228 (3 lines) Essex CM18 7NW 8 16 44.03 3.75 WELCOMED wwi Tel: 0279 442233

CIRCLE 59 FOR FURTHER DETAILS. ELECTROVALUE LTD 28 St. Judes Road, Englefield Green, Egham, Surrey TW20 OHB DEC WRITER 11 (LA36). Very Good Condition £225 MULTIMETER 04324 Tel: 07843 3603 Telex: 264475 GETERMINET 300 with keyboard £125 33 SWITCHED RANGES. 20KOhms per VOLT. Complete with Leads 8 Batteries. BRAND NEW. 1 YEAR Upper/Lower Case E.V. TRANSTEL DOT MATRIX PRINTER. Compact Serial GUARANTEE. £18 each P&P £3 COMPUTING Interlace MN. With ado...... _..._ E6 ea 32 MARCONI WIDE RANGE OSC TF1370A 10Hr10MH: 700 Burnage Lane, Manchester M19 1 NA TELETYPE ASR33 - DATA DYNAMIC 390 (Pmter. Key- Sine; I0H2-100kliz square ...... _.., _ ,...... 135 board, Punch Reader) Tel: 6 RS232 £75 36 MARCONI AF POWER METER TF893A 10H1-35kHz_._.115 061-431 4866 9" MONITOR. Cased. Non-standard; with into .....510 ea 38 MARCONI SENSITIVE WM TF2600 I0Hz-10MHz lmV. 12" MONITOR. Cased. Non-standard, with info EIS ea 3oov...... _ ..í79 HENRYS RADIO 41 HP PULSE GEN 222A. Repetition rate to 10MHz.__._.1150 AZTEC 20" Black and while MONITOR. Video In fS8 ea 42 HP PULSE GEN 21M 200 wan pulse power _...... 4150 404 Edgware Road, London W2 TV Style 20" MONITOR. Black and white. 51 56K LEVEL RECORDER 2305, solid state... .14t4 Video In._...... _ ...... _DO ea 52 BBK LEVEL RECORDER 2305, valve __...... _.1700 Tel: 01-402 6822 53 BBK MICROPHONE AMPLIFIER 2603.. .__...iß00 51 88K RANDON JUSTIN NOISE GEN 1402...... 1125 56 88K RMS AUDIO VOLTMETER 2410...... _.140 LEEDS COMPUTER CENTRE POIARAD SPECTRUM ANALYSER 10MHZ C2008 59 86K MICROPHONE 1111 with stand and cable _....._.255 55 Wade Lane, Merrion Centre, Leeds LS2 TELEOUIPMENTCT7I CURVE RACER £405 65 WAYNE KERR UNIVERSAL BRIDGE 8221 Mk 3 (meter 8NG OSCILLOSCOPES indicator) with low imp adaptor 0221 Mk 3...... _1175 Tel: 0532 458877 TEK 434 STORAGE Dual trace 25MHZ tí80 68 WAYNE KERR COMPONENT BRIDGE 8521 _._. _E45 69 WAYNE KERR VHF ADMITTANCE TEK 453 Dual Trace 50MHZ Delay Sweep £375 BRIDGE 8801 1125 70 WAYNE KERR AF SIG GEN 5121 10Hz-120kHz E40 OFF RECORDS LTD COSSOR 4000 Dual Trace 50MHZ Delay Sweep £250 74 ADVANCE DUAL STAB DC PS P. P.3 0-30ß0-1A tw¢e COSSORCDU150 Dual Trace 35MHZ Delay Sweep 1205 Metered...... _...... _...._... _._.130 Computer House, 58 Battersea Rise, ADVANCE 0S25 Dual Trace 5MHZ £70 79 AYO MULTIMETER 7X...... _. _.E25 H.P. POWER AMPLIFIER 230810-500MHZ £400 80 AVO MULTIMETER Its hont __._145 Clapham Junction, London SW11 1HH 81 AVO TRANSISTOR TESTER AIRMEC FM/AM MOD METER type 409 TTI69 with leads As new (P&Pí21 ...... ___.__...... _._...... _.....__. _._110 Tel: 01-223 7730 3-1200MHZ 1375 88 AIRMEC MODULATION METER 210 3-300MHz AM/.FM BONTOON FM/AM SIG GEN 202H 54-218MHZ £250 . _...... __.196 PARKSTONE ELECTRONICS LTD RAS MICROWAVE POWER METER NRD BN2412 90 BRANDENBURG POWER SUPPLY 314SEL 0-1000V. _..175 0-3.2GHZ 1250 91 BRANDENBURG POWER SUPPLY PM2500/R O-2.5kv1125 18 Station Road, Lower Parkstone, Poole, H.P. UHF SIG GEN 812A. 450-1230MHZ 02011 97 GREEN SYNTHESISED DIGITAL SIGNAL GENERATOR ADVANCE AUDIO SIG GEN J3810HZ-100KHZ £176 0X15601 Hz-9.9MHz Sine/Square ...... _._ _..1500 Dorset BH14 8UB MARCONI IN -SITU UNIVERSAL BRIDGE TF2701 £310 410 MARCONI FM/AM SIG GEN TF2002B 10KHZ-88MHZ Tel: 0202 746555 with 0600 tam SYNCHRONIZER No OSCILLOSCOPES 411 MARCONI SIG GEN TF2012. 400-520MHz. FM... [300 412 MARCONI MOD METER TF23005 2-1000MHi AM. SKYTRONICS LTD 406 TEK465 Dual Trace 100MHe Delay Sweep £960 FM 0375 407 GOULD/ADVANCE 0533008. Dual Trace 50MHz Dual 413 S.E. LABS STROBESM8 0125 357 Derby Road, Nottingham NG7 2DZ Time Base 1468 414 RACAL/AIRMEC SIG GEN 365A 1-320MHz AM/FM 0325 Tel: 0602 781742 408 TELEOUIPMENT D83 Dual Trace 50MHz. delay Sweep 375 B TAPE RECORDER type 7001 1600 LarpeScreen í1B6 383 H.P. RF MILLIVOLTMETER 411A 500KHz-1GH, /0mv- 109 TELEOUIPMENT D75 Dual Trace 50MHz Delay 10V 0150 TARGET ELECTRONICS LTD Swap W50 387 MARCONI DIFF DCVOLTMETERTF26060-1100V [275 11 S.E.LABS SM111 Dual Trace20MHz £200 390 GR FRED METER 8 DISCRIMINATOR1142-A 3200 16 Cherry Lane, Bristol BS1 3BG 5 SOLARTRON/SCHLUMBERGER C81710 dual trace 391 G.R TUNED AMPLIFIERANULLDETECTOR1232-A. £150 50MHz dual TB delay sweep_...... _...... £308 392 CLAUDE LYONS VOLTAGE STABTS2. AC 240V 12A. £100 Tel: 0272 421196

14 SOLARTRON C131100 dual beam 15MHz . ....ISO 398 KINGSHILL STAB POWER SUPPLY 500. Metered 0-60V 15 TELEOUIPMENT D43 duel beam 15MHz _...... I9e 0-0.5A(P&P£4) £40 NEWBURN ELECTRONICS LTD STORABE OSCILLOSCOPES TELEPHONE 19 TELEOUIPMENT 08161 dual trace 1044H2 £375 LOUD SPEAKING EXECUTIVE -PUSHBUTTON 58 Manse Road, Ballycarry, Carrickfergus, 20 TEK 519 with 1A1 plug -m, duel trace 30MHz dual TB Many functions including 10 number memory; repeat delay sweep..__..._..._...... _...... _...._.._._____._.1458 dialling, etc. Will connect to GPO System. Brand New. N. Ireland BT38 9LF 22 HP SIGNAL ANALYSER 54805 memory display with £25 each. P&P E4. 78330 54168 and 5485A Plug -Ins. _RS Tel: 09603 28 MARCONI UNIVERSAL BRIDGE TF1313.0.25% £225 29 MARCONI UHF SIG GEN TF1060/2. 050-1200MHz late MIME OF STOCK - SAE er IaksNMls M IKLS style .... _..1150 lease check availability before ortlermg. Carriage all units 31 MARCONI UNIVERSAL BRIDGF TFR68 ranoe fio £7; VAT to be added to total of Goods and Carriage. It e'er' STEWART OF READING v Gemini Microcomputers ® 110 WYKEHAM ROAD, READING, BERKS RG61 PL Telephone: 0734 68041 a.m. to 5.30 p.m. Monday to Callers welcome 9 Saturday inclusive CIRCLE 50 FOR FURTHER DETAILS. CIRCLE 22 FOR FURTHER DETAILS. 42 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com Every card's a winner. The versatile 8C -Bus system can be ised for a ho;t of applications: Process Control Ba -ch Counting, Robotics, Colour Graphic Displays, CAC/CAM, CNC; In /Aanufaduring, Telecommunications, Instrumentation, Laboratory Testing, Security Systems, Plant Control, Data Coiection and Distribuion. Also, in smaller conpanies it can handle Accounts, Payroll, Wardprocessing, Stock Control, Program Compilation and Data Base Management ... whilst still being able to run specialist applications. And because there is no wasted capacity with a Gemini, a system can cost a good deal leas than you might thine. With Gemini you cc n buy a complete sys+em, upgrade your existing 80 -Bus system, or build your own. So when you've had a look at the pack of cards below, plug yourself into our dealer network -o discover hov opening a new pack of cards with Gemini will help you pick a winner. These represent just a small selection from the range of over 25 cards.

GM813 CPU/64K RAM BOARD - This card provides system 4 GM837 COLOUR GRAPHICS BOARD - 256 x 256 sixteen MHz, Z80 CPU, 64K user RAM and both serial and parallel I/O. colour graphics display. Output to either PAL UHF or RGB. GM811 CPU BOARD - An industrial standard 4 MHz, Z80 GM816 MULTI I/O BOARD - Provides three Z80A PIO devices controller board with parallel and serial I/O together with a plus CTC and battery backed Real Time Clock. variable Bytewide memory capacity. GM848 SERIAL I/O BOARD - Utilises two Z80A SIO chips GM888 CPU BOARD -A new card featuring the Intel 8088 providing four synchronous/asynchronous serial channels with prccessor to provide a dual processor system. software selectable baud rates. Gí41832 SVC BOARD - Provides conventional 80 x 25 or 40 x 25 GM836 NETWORK INTERFACE BOARD - Provides RS422 screen format together with graphics capability. Includes full communication protocol for networking CPU boards. keyboard support and overr.eas character sets. GM862 256K RAM BOARD - Supports both page mode and extended addressing facilities and can be used with all of the MWHQ4RD COMPUTERS Gemini CPU cards. GM833 512K RAM-DISK BOARD - Provides 'psuedo disk' facility in a MultiBoard system.

GM829 FDC/SASI BOARD - Combines floppy disk controller and SASI board supports up to four floppy disk drives plus Winchester controller cards. The dealer's choice

Gemini Microcomputers Ltd., 18 Woodside Road, Amersham, Bucks, England HP6 OBH. Tel: (02403) 28321. Telex: 837788

ELECTRONICS & WIRELESS WORLD JULY 1984 43

www.americanradiohistory.com 1.5GHz testing problems? Multi -Standard MODEM A 7910 WORLD CHIP' Use a TECHTEST Model 260 The chip at the heart 1.5GHz Up -Converter - it works with any 240-350 MHz generator of Richard Lambley's The Model 260 has been designed to provide a very economical signal source for testing 1.5 GHz communication Multi-Standard equipment. It is a linear heterodyne up -converter that employs advanced techniques to generate very clean and stable signals in the 1440-1550 MHz band from signal generator inputs 1200 Modem project. MHz lower. Since it has zero insertion loss the input signal generator controls are used directly to set the output signal level and all modulation conditions. Full accuracy and stability is ensured by phase -locking the internal 1200 MHz local Order now and ask oscillator to the signal generator standard. Find out more from: Techtest Ltd, Street Court, Kingsland, Leominister, for your free Herefordshire HR6 9QA England. Telephone: KINGSLAND (056881) 744 Telex 837264.

data sheet. CIRCLE 70 FOR FURTHER DETAILS.

SATELLITE RECEIVING EQUIPMENT DEVICES IN STOCK AT HAWKS. Prime Source for AMD AM 7910 01-979 1799

1.9M, 2.5M and 5M Harrison Dishes. Sat-Tec R5000 ELECTRONICS 4GHz Receivers. Avcom COM-2B 4GHz Receivers. California Amplifier 4GHz LNAs. Chaparral AHEAD OF THE FUTURE. Horns. Harrison Feed Horns. Road, Hawke Electronics Limited, Amotex House, 45 Hanworth Demonstrations by appointment only. Sunbury-on -Thames, Middlesex Tel: 01-979 7799 Telex: 923592 Dealer enquiries welcome * WORLD CHIP' Is a TradeMark of AMD For further details contact: Harrison Electronics, 22 Milton Road, Westcliff-on-Sea, Essex SSO 7JX. Telephone: Southend (0702) 332338.

CIRCLE 52 FOR FURTHER DETAILS. CIRCLE 6 FOR FURTHER DETAILS. 44 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com MULTI -STANDARD MODEM

by Richard Multi -standard Lambley modem Details of the line interface and software requirements, plus some telephone numbers to dial

-answer circuit is iso- of the IC12 position to ensure that The line interface follows the pat- The auto KRIEStß8E8 F6R YOII - KEY 1 1 is tied high. tern shown in Fig.3 of the article lated from the line by an opto - pin of the Am7910 F P E in the May issue. In the direct - coupler ICII. The zener diodes are Note also that the dotted links F I EETIL to against damage by LK10 and LK12 in last month's cir- connect version of the modem, protect IC E TELT L L L op -amp IC10 duplexes the trans- over -voltages and to define a cuit diagram are shown reversed: mitted and received carriers. threshold level below which it will if a full RS232 interface is f'4IfiÌ`ocomputinq Resistor R44 is the terminating not respond. An a. c. ringing vol- required, the RTS input of IC8 resistor for the telephone line. A tage causes the level on pin 3 of should be linked to pin 11 of ICS Incorporating MICROHET 800 OLL PLEASE KEY 9 BRTS input to pin 8 of ICS. fOO MMEl ASS cmos analogue switch IC9 pro- the inverter (IC,$) to fall, trigger- and the EEPREESTEIILK(sg vides loopback of the transmitted ing the monostable. The tele- LastOusedgNED 167 Yn23,42% signal to the receiver input when phone will continue to ring for a Components IHE BRITISH LIBRARY 50514104c ('p S2 is in test position; but in a few seconds until the second HOW >0 I.OB IN 10 BLAISE -LINE i.c. monostable is triggered by the To log to by direct d:41: direct -connect modem, this The Am7910 integrated circuit is (a)01al the computer on 0279 35411 or rising edge at ICIs pin 4. one o4 the nodes (see below) and its associated components stocked by AMD distributors, (b)When a whistling tone is heard At pin 1 of the engage the modem or coupler. (Tr, and Tr3 etc.) should be omit- this point, including Quarndon Electronics (c)Wait 5 seconds and then type the letter O (upper case). ted, since there will be sufficient Am7910 is pulled low, causing it (d)When you recve the message: and Hawke Electronics; the unit 'PLEASE ENTER /LOGIN' type /LOGIN. coupling around the duplexer. If to begin its answering sequence, (e)When prompted: price is £32.80 excluding v.a.t. PLEASE ENTER USERID/PASSWORD, wart IC9 is not fitted, a link must be and the line -seize relay RI., for three lines of masking to This and other semiconductor print and then enter your USERID pins 8 and 9 of its closes. The time constant of the and password. wired between devices for the project together (f)You will then be connected to the second monostable is about 30 the UI.CMARC file. location on p.c.b. with the crystal, the relays and Key N for direct -dial node numbers is in the seconds, which should allow 1 Address for information When a call progress, the connectors are available from 2 BLAISE -LINE 9 BSD index modem holds the telephone line enough time for the calling Technomatic Ltd (see address by means of the gyrator network modem to establish communica- is also stocked Logging on, or in: like Prestel list). The Am7910 data- around Trs and Trs. This arrange- tion. Control of RL1 then passes by Maplin Electronics. and many commercial ment is taken from a Mullard cir- to the CD or BCD outputs of IC8: if bases, the British Library's The two transformers can be for cuit* widely used in commercial the incoming carrier is lost the BLAISE system asks pas- supplied for £5.70 the pair, swords. modems. No heat -sink is relay will be released and the call including inland postage and required for Trs. The capacitors in terminated. v.a.t., by Barrie Electronics. it the line interface may have to To enable auto -answering, A printed circuit measuring withstand ringing voltages and is necessary to disable RTS until 160 by 200mm will be available IC8 is transients on the line, and so it is the answer sequence of from July 10 from Combe Martin important to fit suitably rated complete. For this reason the Electronics, for £16 inclusive. types: for the prototypes, 250V amendments shown in Fig.3 The board, a prototype of which metallized film capacitors were should be made to the computer was shown in last month's article, of the modem. chosen. interface section is double sided with plated - If the constructor does not The additional connection to pin through holes. intend to add an auto -dialler, 16 of IC8 is to ensure that the DTR The start of a program in Apple there is no need for RL2, RL3 or signal is removed briefly between Basic, in Prestel telesoftware Software their associated components R49, auto -answered calls. Without format. With the help of and C2; but a wire link should this, the modem will not generate suitable communications R51 program in place of the contacts its burst of answer tone. To control the modem, a suitable software, a complete be added can be down loaded of RL2. However, a problem may arise communications program is needed. In its simplest form, this automatically in about the The spark gap across the tele- if a large transient occurs on the time it would take to load from phone line is included for safety, line as S3 is moved. The first mon- would configure the serial port to tape. although some commercial ostable in IC12 may be triggered, transmit and receive at the Aladdin's Cave 7002149d Op do without. It should be removing DTR temporarily. If required rate. It would then route IIAIILO'4'F'Ok.E'G16TOULS'4'4TEXT+nIL10=4'GOiU'460 modems 000nL100=CH=F'fi/.(GL):CT''4f%(T%(GL) I: 'GO able to withstand the voltages this happens, a way of dealing data arriving from the modem to SUB'43000: EV=4==4CR':'RETURN'41I L 150=EV'F'4i% ( H % (GL )):'RETURN'nIL20O'EV''4T%(H%(GL)):'RE monostable the screen, and direct data from TURN'4lIL'250'4I'F =Ali '4='FI% (H% (GL ) ) :'1GUTU=4627 developed during ringing without with it is to inhibit the IIL260'4'RETURN'4I1L300'41'F=R7. (GL1'F=4H% down. Suitable types except when auto -answering is the keyboard to the modem. LI):'GO 10=4627 u L 350'E V'F=Ii'/. ( GL 1 : =RE TURNLII breaking L 400=C+4='GL 11 L 4 I 0=4'4I F=C=F'44L=4THEN'4.FR IN TN C40 R58, but In a practical program there "LUND: =FAILURE=4iARN iNG": EV'F'NL:'RETURN=4 are available from Electrovalue enabled. Omit and IIL420'FM'F'1-1% (H% (C) I : ST=4='C:'GOSUB'44000: also be facilities for select- 2,4OSUB'f/000: =GOSUB+ti000: C'4='40T: =4I F'EV'4=L Ltd. connect pin 6 of IC,s to pins 3 and would NL'4THEN'C'F=4r% (C) : =GOTO'441OIIL43O'FM'P'4f% 17. (H% (C) ) / :'GOSUB'A000:'RETURNLIIL450'IJX word length, parity T 11 of IC12. ing the data (H% ( GL ) > : NY'F'4T % ( GL ) :'GOSUB'414000: ï (H% (GL) )''RX:EVL=N% (GL) :'RETURN'411L60U If the components of the auto- and stop bits, for controlling the -GN'4='4A1'H'4A211L605'4'4GOSUB'45500:EV'4=a4I X: =4 *LSI circuits for teletext and view- RETURN'4IIL610'GN'F'4A1=4º=a42: =4GOTO=46O511L615 answer section are ommitted display format and for transfer- 'W 1'4/'4A2: 'GO T 0'460511 L 62o'GNL'4.11'4-'ii data: the Lucy generation. Mullard ,: 'GO 1O'460511 L 625'41'4==A 1 '4-F'4A2:'GOTO'462 entirely, a 47k52 resistor must be ring disc or cassette files to and 7 L627=EV'F'lD ( I ) :'RETURN'411L630'4I=4='4A1'Y. Technical Publication M81-0001, -IF'4A2: 'GO TO'462 / II L 6'.5'41'F'ïi 1'4.'4' 4?412:'GO June 1981. inserted between pins 12 and 16 from the modem. 10'4S 2711 L640'41'4='441'4 II Z 076M I CROSOURCE ELECTRONICS & WIRELESS WORLD JULY 1984 45

www.americanradiohistory.com MULTI -STANDARD MODEM

Fig.1. Line interface, and auto - Other useful options include board. In particular, the effect of ling. This protocol allows virtu- answer section. Isolation from the ability to send Xon and Xoff the delete key seems to vary from ally error -free transfer of Ascii the line is via a transformer commands to halt temporarily the one computer to another. For text or program files over event and, for the ring detection cir- output from the distant compu- Viewdata systems such as Prestel the poorest lines. The file to be cuit, - an opto -coupler. An auto ter, and echo incoming dialler could be added by the to charac- it is convenient to have the return sent is transmitted in 128 -byte user if required. ters back to it: this allows the key send a # character. blocks, with error -checking on other operator to see what he is Some of the bulletin board each block. If an error arises, the typing. There may be some systems listed here have adopted receiving computer asks for the advantage too in redefining the the so-called Christensen or block to be sent once more. output of certain keys on the key- Xmodem protocol for file hand - Error -checking is used also in viewdata terminal programs for telesoftware file downloading. +5V Viewdata software for a var- iety of home and business compu-

R47 ters is available from Micronet 800. For the 300 baud 2 modes, Maplin Voo +12V Electronics can provide Cl2 R44 620 modem interfaces and software 7 for the ZX81, Spectrum, Dragon, IC10 R43 100 2y2 R45 Oric, VIC 20 and Commodore 64. 6 5 13 741 CAP2, 4 For the BBC Microcomputer - 22k 1_6_1C30 1n there is a wide choice of software, Cap, +5V -12V H 4 IC9 013 including packages in eprom. ln Computer Concepts' 2 14 R46 Z 22k communica- `-1C31 i -- 4066 tor (16Kbyte) provides emulation see tex 8 of a DEC VT100 terminal. It gives R61 1314 very extensive control of trans- C 9 11 mission mode and display format 10k includes R67 15k 10 1 and such features as sto- -5V rage of telephone numbers for an 9 AGND auto -dialler. Communicator costs Analogue ground £59. A rom of especial interest to Connected to p s u smoothing capacitors bulletin -board users is Pace Sof- SK2 ç . tware's Commstar (8Kbyte). This L _ _ Telephone socket Ö06000000`- (Line) provides software handshaking, file transfer facilities using the RL1a ICß C36 22 / 250V Christensen Xmodem protocols V C34 1249 Am7910 Handset and numerous other features. disconnect o A 42 82 Current versions have a Prestel RL2 mode which supports colour Seize -line O-y Viewdata graphics (including A RL1b IMP 39 double -height characters) and 0 5W can download telesoftware. The price is £34 including v.a.t. c33 ...10n Tr6 Software for the TRS-80 is 250V 017 D19 BC183L available from Molimerx Ltd, so R54 82k who offer two communications 2 R51 packages: Smart Terminal at 2R2 018 020 BFY50 £25.30 and Modem 80 at B1C R53 021-1 150 R48 15V £30.48. 400 150 82k C36- A communications program to R52 47 10/ mW RL3 (DON 0 5W 10V run under CP/M-80 is available to members of the CP/M User's Group. Details, in return for a F +5V stamped addressed envelope,

1 0 R60 from the group at 72 Mill Road, BL GN W R 100k 16 100k R5100k Hawley, Dartford, Kent . Individ- 15 To telephone line ual membership costs £7.50 per R56 560k 3 year. C41, 14 11 -C37 47/16 IC12 2»2 /250V C40 100/ gig V8ß C38 263V Logging on 7if 2 4 R55 2 2k2 If p 10 6 022y, 100n IC16 741S221 First select the appropriate sig- -- R57 82k 026 027 R65 óN139 nalling - 5V 6 standard and mode using S1 S3 1k 7 220/16 and Sz. At this stage should 9 3 x 5V6 1 be in the centre off-line position. 400mW C43 T1n Dial up the computer of interest; To DY81Fig3) and when its answering tone is 13 e1 heard move S3 to the on-line posi- 12 tion. This will establish commu- nication, disconnecting the tele -

46 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com phone handset at the same time. t12V With some of the bulletin board systems listed in the box, it may In then be necessary to type a few T1 E2" out carriage returns to start things C9 +5V 9 7805 off. 1000/25 220n r-1 F1 corn At of call, S3 should L the end the C13 220n be moved back to the centre posi- 250mA tion to break the connection. In o the Viewdata mode, disconnec- 0V tion occurs automatically when corn C14 220n the Prestel computer drops its OU N IC carrier. This may happen prema- c11 C12 5V 79105 turely if the RTS signal is 1000/ 220n n removed: as this may occur 25 momentarily while files are being 12V E saved to cassette or disc, it may AGND be best to fix RTS permanently on in the modem. This can be done ----_ Fig .2. Space for this power by linking pins 13 and 14 of ICS; it Fig.3. Disabling RTS and DTR supply is provided on the p.c.b. may then be wise to cut the track during the auto -answer sequ- R66 16 áä To collector between pin 13 and the 25 -way ence. This addition has been 2k2 of Tr4 socket to avoid contention when incorporated in the p.c.b. for D28i ice the full RS232 interface is used. this project. To 1112 The third position of S3 allows Ar17910 p in 13 the modem to auto -answer calls from other computers. This facil- ity is allowed only in the 300 baud 'answer' modes and in V.23 mode with S2 set to 'reverse'. Acquisition of a carrier in the +5V back channel is indicated by L LED and in the main channel by R62 1M [4210 t- LED,. LED, lights when the cir- To IC5 pin 11 12 tañr2 cuit is powered and flickers dur- 1118 4071 13 ing transmission of outgoing 5 R63 data. When a call is auto - 6 answered, LED, lights; and LED, IC16 10M D24 025 R64 7 comes on when the modem is Viewdata holding a line. 470k To test the modem off-line, Prestel Microcomputing: details To IC14 pin 9 To 1C14 pinti set S2 to the test position. The from Micronet 800, Scriptor Court, 155 Farringdon Road, London EC1R modem should then echo charac- 3AD. Enquiries, 01-278 3143. The ters typed at the keyboard back to 2200h daily. V.21, Bell 103 and 1200/ 01.00-09.00h with Bell 103 tones. quarterly subscription of £ 13 (for the screen. Note that this test 75 baud V.23. TBBS Southampton: 0703- domestic users) gives access to Mic- may not work in the V.23 mode, CBBS Southwest: 0626-890014, 24 437200, 17.00-08.00h weekdays, all ronet 800, Viewfax 258 and all sec- tions of Prestel not restricted to other since the Viewdata terminal soft- hours, V.21 and 1200/75 baud V.23. day at weekends. CBBS Surrey (Woking): 04862- North Birmingham BBS: 0827 closed user groups. ware will set the RS232 driver and. 25174, 24 hours. 288810*, 24 hours. Prestel: for information ask the oper- receiver to different data rates. MG -NET CBBS (London): 01-399 Blandford Board: 0258-54494, 24 ator for Freefone 2296. 2136, Sunday only, 17.00-22.00h. hours. *'Ring back' systems: dial the num- CABB, Computer Answers bulletin 24 ber, let it ring once, replace the hand- Some databases to try Stoke ITEC BB: 0728-265078, board (London): 01-6313076, 24 hours. set and then dial again. hours. Also weekdays on 1200/75 Southern Bulletin Board: 0243- The following 'bulletin board'sys- baud V.23. 511077, 24 hours. Addresses tems are run by private individ- Forum -80 (Hull): 0482-859169. BASUG (British Apple Systems User Barrie Electronics Ltd, Unit 211, on a voluntary basis. No Tuesday and Thursday, 19.00- Group board): 0742-667983, 24 uals 22.00h; Saturday and Sunday, 13.00- hours. Stratford Workshops, Burford Road, charges are made for use of their 22.00h. Night-time service for London E15 2SP; 01-555 0228. facilities, which include message U.S.A. using Bell 103 tones, 00.00- The following commercial sys- Combe Martin Electronics, King handling, software downloading 08.00h. tems, operated by electronic Street, Combe Martin, Devon EX34 Forum -80 (London): 01-902 2546, component suppliers make no OAD. and news. Forum -80 systems use Computer Concepts, 16 Wayside, evenings and weekends. charge to users except where a seven -bit word with even parity Mailbox -80 (Liverpool): 051-428 Chipperfield, Hertfordshire WD4 9.11; and one stop bit; others have an 8924, 24 hours. shown: 09277-69727. eight -bit word with one stop bit Mailbox -83 (West Midlands): 0384- Distel (Display Electronics Ltd, Lon- Electrovalue Ltd, 28 St Judé s Road, and all SE19): 01-679 1888 (V.21). A Englefield Green, Egham, Surrey no bit. 635336*, 17.30-08.30h daily don and parity day Sunday. 1200/75 baud service is to be added: TW20 OI-IB; 0784-33603. Beware of 1200/75 systems: Manchester BB: 061-427 3711, test port on 01-679 6183. Maplin Electronic Supplies Ltd, P.O. some use the same data format as Sunday -Thursday 22.30-00.0h, Fri- Estelle (STC Electronic Services, Box 3, Rayleigh, Essex SS6 8LR; on their 300 baud modems, and day 13.30-02.00h, Saturday 22.30- Harlow, Essex): 0279-443511 0702-554155. 02.00h. (V.21), 0279-442288 (V.23), busi- Molimerx Ltd, 1 Buckhurst Road, may not be compatible with Pres- Microweb (Stockport): 061-456 ness hours. Town Hall Square, Bexhill -on -Sea, tel terminal software. 4157, 24 hours. For users of the BBC Rewtel (Cirkit, formerly Ambit East Sussex; 0424-220391. Micro. International, Brentwood, Essex): Pace Software Supplies Ltd, 92 New CBBS Chiltern: 07073-28723, TBBS City (London): 01-606 4194, 0277-232628. Some facilities are Cross Street, Bardford BD5 8BS; 07073-39241, 18.30-22.30h, Mon- 24 hours. 1200/75 on Wednesdays. available only to subscribers. 0274-729306. day and Wednesday. TBBS London: 01-348 9400, 09.00- Maptel (Maplin Electronics Ltd, Technomatic Ltd, 17 Burnley Road, CBBS Cumbria: 069-92314*, 1800- 01.00h with CCITT V.21 tones, Southend-on-Sea): 0702-552941. London NW 10 lED; 01-4521500.

ELECTRONICS & WIRELESS WORLD JULY 1984 47

www.americanradiohistory.com STEEL DISHED TOROIDALS WASHER OUTER INSULATION The toroidal transformer is now accepted as the standard in industry, overtaking the obsolete laminated type. Industry has been quick to recognise the advantages toroidals offer in size, weight, lower radiated NEOPRENE SECONDARY WASHERS field and, thanks to I.L.P., PRICE. WINDING

Our large standard range is complemented by our SPECIAL DESIGN INSULATION section which can offer a prototype service within14 DAYS together CORE with a short lead time on quantity orders which can be programmed PRIMARY WINDING to your requirements with no price penalty. END CAPS

15 VA 50 VA 120 VA 225 VA 500 VA 62 x 34mm 0.35Kg 80 x 35mm 0.9Kg 90 x 40mm 1.2Kg 110 x 45mm 2.2Kg 140 x 60mm 4Kg Regulation 19% Regulation 13% Regulation 11% Regulation 7% Regulation 4% Why a Toroid? Smaller size & weight to meet SERIES SECONDARY MIS 2.010 6.6 4 16 4.010 6+6 1000 6.012 12+12 9 38 9.016 25+25 1000 No Volts Current 2.011 9+9 2 77 4,011 9.9 6 66 6.013 15+15 7 50 8.017 30+30 833 modern 'slimline' requirements. 2.012 12+12 2 08 4.012 12+12 500 6.014 18+18 6 25 8.018 35+35 7 14 11 Low electrically induced 0.010 6.6 '25 2.013 15+15 1 66 4.013 15.15 400 6.015 22+22 5 8.026 40+40 6 25 0.011 9+9 0 83 2.014 18+18 1 38 4,0.14 18.18 333 6016 25+25 450 9.025 45.45 5 55 noise demanded by compact 0.012 12+12 0 63 2.015 22+22 1 13 4.015 22+22 2 72 6.017 30+30 375 8.033 50+50 500 15.15 050 equipment. 0.013 2,016 25.25 1 00 4.016 25.25 2 40 6.018 35+35 321 8.042 55.55 4 54 42 High 0.014 18+18 0 2.017 30+30 0 83 4.017 30+30 2 00 6.026 40+40 2 81 8.028 110 4 54 efficiency enabling 0.015 22.22 0 34 2 2.028 170 0 45 4.018 35.35 1 71 6.025 45,45 50 8.029 220 2 27 conservative rating whilst main- 0.016 25+25 030 2.029 220 0 22 4.028 110 1 09 6.033 50.50 225 8.030 240 2 08 taining size advantages. 0,017 30+30 025 240 0 20 4.029 6,028 110 2 04 2.030 220 0 54 VA 1 625 (encased in ABS plastic) 4.030 240 050 6x029 220 02 Lower operating temperature. RO VA 6.030 240 0 93 140 x 75mm 5Kg 160 VA 30 VA 90 x 30mm 1 Kg Regulation 4% 110 x 40mm 1.8Kg 300 VA Why ILP? 70 x 30mm 0.45Kg Regulation 12% Regulation 110 x 50mm 2.6Kg 9.017 30.30 10 41 Regulation 18% 8% Ex -stock delivery for small Regulation 6% 9.018 35.35 8 92 3.010 6.6 6 64 5.011 6 89 9.9 40.40 7 3.011 9.9 4 44 9.026 81 quantities. 1.010 6.6 2 50 5.012 12+12 6 66 7x013 15.15 10 00 12.12 3 9.025 45.45 6 94 1 3.012 33 available. 21 1.011 9.9 66 5.013 15.15 5 33 7.014 18+18 833 Gold service days 3.013 15.15 2 66 9.033 50+50 625 1.012 12+12 1 25 5.014 18.18 4 44 7.015 22+22 6 82 18.18 2 22 9.042 55.55 5 68 manufacture for urgent deliveries. 1.013 15.15 100 3,014 5 015 22.02 363 7.016 25+25 6 00 9.028 110 5 68 1.014 18+18 0 83 3.015 22.22 1 81 25+25 320 5 5.0,6 7.017 30+30 500 9.029 220 2 84 year no quibble guarantee. 1.015 22+22 0 68 3,016 25.25 1 60 5.017 30.30 266 7.018 3.017 30.30 133 35.35 4 28 9.030 240 2 60 Realistic delivery for volume 1.016 25.25 0 60 5.018 35.35 228 7.026 40+40 3 75 3.028 110 0 72 1x017 30.30 0 50 5.026 40.40 200 7.025 45+45 333 orders. 3.029 220 0 36 5.028 110 1 45 7.033 50+50 3 00 No price penalty 3.030 240 0 33 for call off 5.029 220 0 72 7x028 110 2 72 0 orders. 5.030 240 66 1.029 220 1 36

7+030 240 1 25

Prices including P&P and VAT Mail Order - Plea a make your crossed Post to: ILP Electronics Dept. 3 VA Size VA Size cheques or postal orders payable to ILP Ltd., 15 0 7.43 160 5 12.90 Electronics Ltd. Graham Bell House, Roper Close, 30 1 8.08 225 6 16.30 Trade - We will open your credit account Canterbury, Kent. CT2 7EP 50 2 10.10 300 7 18.55 immediately upon receipt of your first 80 3 10.81 500 8 25.73 Tel: (0227) 54778 Telex: 965780 120 4 11.73 625 9 31.63 order.

For 110V primary insert "0" in place of "X" in type number. For 220V primary (Europe) insert "1" in place of "X" in type number. For 240V primary (UK) insert "2" in place of "X" in type number. VISA IMPORTANT: Regulation . All voltages quoted are FULL LOAD. Please add regulation figure to secondary voltage to obtain off load voltage. IC1)1 IL. IF' ELECTRONICS LTD. CIRCLE 09 FOR FURTHER DETAILS. HIGH PERFORMANCE HIGH RELIABILITY FREQUENCY COUNTERS LOW COST The brand new Meteor series of 8 -digit Frequency Counters offer the lowest cost professional performance available anywhere. * Measuring typically 2Hz - 1.2GHz * Low Pass Filter * Sensitivity <50mV at 1GHz * Battery or Mains * Setability 0.5ppm * Factory Calibrated

* High Accuracy * 1 -Year Guarantee * 3 Gate Times * 0.5" easy to read L.E.D. Display e PRICES (Inc. adaptor/charger, P Et P and VATI METEOR 100 I100MHz) £104.36 Illustrated colour brochure &c.414.... METEOR 600 1600MHzl £134.26 with technical specification METEOR 1000 11GHzl £ 184.36 and prices available on request. 10 // Designed and BLACK STAR LTD, Dept. WW, 9A Crown Street, St Ives manufactured Black*Star Huntingdon, Cambs PE17 4EB, England 1//Ee in Britain Tel" 10480) 62440 Telex: 32339 CIRCLE 14 FOR FURTHER DETAILS. AMBISONIC SURROUND SOUND DECODERS ANTENNA TUNER Ambisonic surround sound gives a realism in the reproduction of music that is hard to describe without using hackneyed expressions NEW! 0.1-30MHZ, IMPROVES RECEPTION, switched series/para- like 'natural' and 'being there'. Positioning of the performer becomes llel bandpass, adapts to absorption wavemeter, field strength obvious and the acoustic of the original environment comes through to the listening room. The Minim decoders also provide enhanced meter, modulation monitor, £25-20. results from conventional stereo material. We can now supply UHJ TIME WRONG? MSF CLOCK is ALWAYS CORRECT - never gains or encoded records, tapes and compact discs. loses, SELF SETTING at switch -on, 8 digits show Date, Hours, And don't forget our other products: Minutes and Seconds, auto GMT/BST and leap year, can PROGRAMMABLE WEEKLY TIME SWITCHES expand to Years, Months, Weekday and Milliseconds, parallel TELEVISION SOUND TUNERS BCD output for computer, audio to record and show time on playback, receives Rugby 60KHz atomic time signals, only Please send me information on Timeswitches/Television Tuners/Ambisonics 15X15X8 cm, built-in antenna, 1000Km range, GET the TIME RIGHT,£72-70. Name Each fun -to -build kit (ready made to order) includes all parts, case, Address by -return postage etc and list of other kits.

Minim Electronics Limited, Lent Rise Road CAMBRIDGE KITS Burnham, Slough SL1 7NY. Tel. Burnham 63724 WW 7 45 (WG) Old School Lane, Mitton, Cambridge. Tel. 860150 CIRCLE 68 FOR FURTHER DETAILS. 48 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com CIRCUIT IDEAS

DON'T WASTE GOOD IDEAS RS422/RS232 ideas with RS422 in/out We prefer circuit neat drawings and converter widely -spaced typescripts, but RS422 is a half -duplex data -link we would rather have scribbles standard and, being balanced, on "the back of an envelope" allows greater distances to be than let good ideas be wasted. covered and higher data rates Submissions are judged on than are possible using RS232. It originality or usefulness - can also be used with one not excluding imaginative transmitter and several receivers modifications to existing (`multi -drop'). This circuit circuits so these points should provides RS422 and line be brought to the fore, monitoring using an RS232 flout Bout Ain Bout preferably in the first v.d.u. or computer. sentence. Minimum payment Normally, the circuit is in of £30 is made for published receive mode and the v. d. u. circuits, normally early in the monitors the line. When a key is month following publication. pressed, line four on the RS232 interface is inverted and the 2 75176 transmits the character. is 3 5

Receive mode is resumed on key RS232 (to v du. l release. Line five provides 75176, 1489 require only +5V, Gnd, information on the direction of 1488 also requires + 12V, -12V. the line and may be omitted. Essentially, the circuit is a level converter and therefore independent of data rates. Note which can lead to apparent loss of should be taken with layout. that direction reversal time on an characters. A twisted pair should L. Smith RS422 line can be far shorter be used for the 422 line as the Blackford than that of a simple v. d. u. , 75176 is very sensitive, and care Perthshire

Isolated video driver so that the transistors can tracks should be separated from Designed for connecting fet drain/source resistors and operate at maximum speed. the grounded side by at least computer video output to a supply voltage, keeps the Direct -current supply for this 4mm for insulation, and signal non -isolated domestic tv, this optical -coupler transfer stage may come from the tv; in paths should have minimum circuit uses a readily available characteristic in its linear region. valve sets, the sound stray capacitance. Video signal 6N139 optical coupler (RS Capacitor C3 negates the effect of output -valve cathode might be from 75Q coaxial cable is Components) operating at 1:1 Miller capacitance in the driver used. terminated and should be about current -transfer ratio. Positive transistor and C4 extends The prototype gave rise and 1V pk at the input and large for video modulation is assumed frequency response to above fall times of 200ns corresponding values of Cl. 2 are required and, for the UK, a composite about 800kHz by quickly to a bandwidth of 5MHz which faithful reproduction of video -signal bandwidth removing stored charge in the should be sufficient for most frame -sync. pulses. Output is requirement of 6MHz. transistor emitter during voltage home computers. Bandwidth is about 4V pk and may need to be Voltage gain of the fet stage is transitions. Resistor R7 is set for mainly limited by the divided for some sets. about four. The source is directly optimum rise and fall times. opto -coupler and faster devices coupled to the next stage which Collector current in the should work with only minor J. A. McLay approximates a current drive for opto -coupler is about 7mA, modifications since the driver Ballincollig the coupler led. Bias current of allowing low resistor values to be bandwidth is about 20MHz. Co. Cork around 9mA, determined by the used to shunt Miller capacitance Layout is critical - all tv circuit Ireland

12

11 723, 2.\1/ 1 8 to 12V 6 10

10k 4. '100n 100n 390 13 Cl 3p3 390 +0V 150p '0V Video (22k 1- out BC 1831. 100n OV VV` 10k VC

10p It" 'I"' Vidneoy 2N3819 --,e I I - 4700 22n 25V RS 6N139

68 1M 180C21.1303 470 44. . tv chassis

ELECTRONICS & WIRELESS WORLD JULY 1984 49

www.americanradiohistory.com CIRCUIT IDEAS

+5V Microprocessor 1 7476 teaching aid Using the WAIT command, the Z80 microprocessor can be made to execute one instruction at a time under control of a manual switch. If all the address, data and control lines are monitored, the processor can be seen fetching/storing information and Next carrying out commands. il instruction While the switch is open, 04 WAIT is low. When the switch is closed, the upper bistable device is clocked and WAIT goes high. Simple clipping +5V Simultaneously, pulses from the detector áti processor clock feed the lower 1/67406 bistable i. c. and after two rising No 100 setting up is required on this edges, the output of the lower simple clipping detector for audio device goes low and resets the power amplifiers. When positive upper one. Thus WAIT returns output swing exceeds T OV low after one or two clock cycles Vb 1+Veb l be2+VD 1 Repeat for D1 to D7, AO to A15 c.p.a. and memory control Ones and sets the lower bistable i.c. +Vlad+V Note that dynamic memory the led lights. Values shown are content will be lost since the for a 34-0-34V supply and switch memory -refresh circuit cannot the led on at 64V pk-pk, but they operate. The circuit has been may be altered to suit any single Accentuated metronome used with a ZX81 (no ram or dual -rail power amplifier. expansion), connected through Tolerance on the switching point Loud regular pips - clearly cause Tr3_6 to be driven in the 23 -row connector to make is about 0.5V due to junction audible even above my attempts opposition to Tr12 on the first internal soldering unnecessary. effects. Resistor RI and the diode to master the guitar - are beat of each bar to give an A binary -to -hexadecimal protect Tr2 during negative generated by this metronome. accentuated pip. Time signatures converter and display on the data swing. Each pulse from ICIa triggers a of 2/4, 3/4 or 4/4 are selected by lines is a useful addition. M.J. Conduit fixed-duration pulse from ICIb a switch. Supplies of between 5 Peter Hall Farnham which drives the loudspeaker and 18V may be used. I used two University College London Surrey through Tr1 2. Normally, PP3 batteries to give 18V in the common collectors of Tr3_6 are prototype. approximately at ground Steve Kirby potential but counting and East Molesey decoding circuits around IC2 Surrey

5to16V 10k 2k2 Pulse rate 1n 100k .l4 14 6 10 r1 f/4 BC 214 5i 10 3 5 S 13 Tr CK CK Q A 1k IC1a 470 1 IC2a f/2 IC2b 12 IC1b 9 2 i 556 4013 4013 2k2 v2 556

6 5 2 8 11 D D a 220p tin R Tr, 3}3 7 4 10 470 BC 184 T 680n Ton 11 th 10k 18 9

12 13 14 15 10 12

13

12

eg.4/4 A

1/44011 tic 4081 1/64069 B 10k V- -Do-

50 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com °cnRcurr IDEAS

Artificial daylight

For applications including bye tropical fish -tank lighting, this o t changes lamp circuit gradually 39 brightness from off to full -on in 25 minutes, or vice versa 2N3B19 >150 depending on the switch 47 1m 100k position. A bridge rectifier and shunt zener diode provide mains synchronized d.c. pulses. Triac 100k 100n firing, through an opto -coupler, 2M 2N2646 400V is from a unijunction transistor MOC 302) SA whose time constant is 100n 400V determined by a fet acting as a 100 variable resistor. The capacitor which biases the fet, is charged or <<°150 discharged depending on the 1N4.007 x 2 O switch position. If R, is disconnected, brightness Load remains constant for at least 24h Neutral O O through charge in C1. All resistors except R2 are 1'2W J. Clegg Doncaster Yorkshire

Accurate switched -gain for op -amps Using a cheap array of seven equal resistors provides accurate switched op -amp gains of one, two, five and ten times. Resistance ratios for these gains in a non -inverting amplifier are 02. 12, 22 and 32 respectively so the input resistor may be made from zero, one, two or three resistors in parallel, and the feedback resistor form the same number of resistors in series. B. P. Cowan Bedford College University of London

Current limiting for 317 regulators Addition of an opto -isolator to a 317 -based variable -voltage power supply allows precise current limiting. I have used this circuit to protect transistors during development of r. f. output stages of uncertain behaviour and it should be possible to apply this Combination lock idea to simpler power supplies using power-transistor/zener- with deterrent diode combinations. When voltage across the In this idea in the May issue, IC, series -pass resistor exceeds should have been a 74148, E0 of around 1V the isolator 1.5V above control voltage to be able to carry more than the IC2 is not connected to E, of IC photodiode starts to emit, limit output current under a dead current limit value. the transistor shown should have turning on the phototransistor short. Power and resistance Lionel Sear a base resistor and IC17a is the and reducing control voltage to ratings of the series resistor are Truro left-hand section. On IC6, Q and the regulator. Output diodes chosen to suit the required Cornwall Q should be transposed. We keep regulator output voltage at current limit and the diodes must apologise for these errors. ELECTRONICS & WIRELESS WORLD JULY 1984 51

www.americanradiohistory.com Remote volume

+12v control 10

Heart of this circuit, which 7 100n requires only contact closures for 4069 1M5 12 volume increase/decrease, is a 16 15 14 13 12 11 10 9 4051 eight -channel multiplexer CK C PC PB B U!D BIN operating in analogue mode. The BCD setting of this variable attenuator 4029 depends on output states of a LD 0 PD PA LIN 4029 up/down counter which is 2 3 4 5 6 stepped through on contact +12V 110k +12V 4 8 closures under control of a 1M buffered clock signal from pin eight of the 4069 inverter. Lf Stop 555 +12V Frequency of the clock is RC/2.2 8 14 and a 555 timer ensures that the Down' 100n volume level is low when the 1/64069 circuit is switched on. +12V 10k +12V One 4051 is required for each 14 11 14 further audio channel, A 10 the 12 2k2 maximum number of channels 13 only being limited by 4029 drive 4025 capability. B +5V DennisJ. Eichenberg 1k 560 4k3 Ohio USA C 10 16 15 141 131 12 11 10 9

2 1 0 3 A B Dut 4051 7 6 5 INH

71 61 8

-5V 43k 20k 10k Out In Amplifier

Three -channel light dimmer Using a non-linear ramp to linearize power output, this light 150k dimmer with three channels 1N4D04 requires few components and 1N 4148 allows triacs to be fired remotely through non -mains carrying Muffì -core cable. Remote firing also means cable < 3k that the triacs can be mounted next Mains to the load which simplifies f (filtered) mains filtering. Channels may be added by using further Sk comparators, isolators and 100k Bark Bright triacs . Advantage is As above taken of the LM339 open -collector outputs to 100y ed\tl_e< eliminate series resistors at the 100n 10V LM339 three phase -control sections and 4k7 As above directly discharge the ramp 11k capacitor. Transformer output 22;\,,\A5/ k should not exceed about 6V to Gnd. prevent excessive dissipation in the LM339. Tim Williams Tunbridge Wells Kent

52 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com Cool and calculating. og's fast CMOS digital multipliers.

It takes the leader in real -world overheated "multifriers" that are signal processing to come up with a plugged into your sockets right now. family of fast, digital multipliers as In addition we are proud to cool and calculating as CMOS. announce our proprietary single port No more power-hungry ECL, NMOS, 6 x 16 multiplier accumulator and bipolar multipliers encumbered with (ADSP 1110) for new low-cost designs heft/ power supplies, heat sinks and and 24 x 24 multiplier (ADSP 1024) cooling fans. for high accuracy applications. No more power-related design In the coming months, Analog headaches, reliability problems or costs Devices will be moving its entire DSP that make your temperature soar. product line into a new two -micron CMOS digital multipliers keep a cool CMOS process. This process enables head whether your application calls for the cycle times for all parts to improve digital filters, FFTs, matrix operations or by roughly a factor of 2.5 to one. For ¡iP acceleration. example, we will be offering a 16 x 16 Ir DIPs, flatpacks, LCCs and space multiplier with a 60nS multiply time - saving pin grid arrays, our improved in a low-power CMOS technology. In second source products offer addition to major speed break-throughs comparable speed at less Than 1/20th on industry standard parts, watch for the power. All at competitive prices. us to announce a broad line of Pin--or-pin, they'll replace the proprietary DSP devices during 1984.

POWER SPEED (nS) PART DESCRIPTION REPLACES (W) 25°C AMB 70°C AMB 125°C AMB' ADSP 1080 8 x 8 MULTIPLIER MPY 08HJ 0.09 85 100 115 ADSP 1008 8 x 8 MULT/ACC TDC 1008J 0.1 105 120 140 ADSP 1081 8 x 8 UNSIGNED MULL MPY 8HUJ 0.1 75 90 105 ADSP 1012 12 x 12 MULTIPLIER MPY 12HJ 0.15 110 130 150 ADSP 1009 12 x 12 MULT/ACC TDC1009J 0.15 130 155 180 ADSP 1016 16 x 16 MULTIPLIER MPY 16HJ 0.15 145 170 200 ADSP 1010 16 x 16 MULT/ACC TDC 1010) 0.15 165 190 220

ADSP 1 1 10 16 x 16 SINGLE PORT MAC PROPRIETARY 0.15 165 190 220 ADSP 1024 24 x 24 MULTIPLIER PROPRIETARY 0.25 200 235 275 * Contemporary ECL and Bipolar parts are spec'd for a maximum CASE temperature of 125°C. Due to their high dissipation this :orresponds to an ambient of about 95°C. Analog Devices Military. CMOS parts are spec'd at an AMBIENT of 125°C.

For further information, contact: ANALOG Analog Devices Limited, Central Avenue, East Molesey, Surrey KT8 OSN. DEVICES Tel: 01-941 0466. Telex: 929962. CIRCLE 35 FOR FURTHER DETAILS. LECTRONICS & WIRELESS WORLD JULY 1984 53

www.americanradiohistory.com GENERATORS

NEW TG501 FUNCTION GENERATOR .005Hz to 5MHz; sine, square, triangle, ramp, pulse and haverwave waveforms; free -run, triggered or gated modes; variable start/stop phase, 19:1 symmetry range; variable DC offset; variable 5052 output; HL output; external sweep mode. NEW TG502 SWEEP/FUNCTION GENERATOR Main generator features as TG501 plus internal sweep generator; 1000:1 linear or 10,000:1 log sweep range; precise dial -and -enter setting of sweep limits; marker with variable duration and out -of-range indicator; variable sweep rate; single sweep mode; sweep reset and hold; sweep and pen -lift outputs. NEW TG503 PULSE/FUNCTION GENERATOR Main generator features as TG501 plus normal, double and delayed pulse modes; pulse width variable from 5Ons to 50ms; delay variable from 100ns to 50ms; 10MHz capability in double pulse mode; complement mode; symmetrical, positive-going or negative -going outputs with adjustable baseline. For further information contact: Thandar Electronics Ltd, London Road, St Ives, Huntingdon, Cambridgeshire PE17 4HJ Telephone: (0480) 64646 Telex: 32250. thondoi ELECTRONICS LIMITED CIRCLE 21 FOR FURTHER DETAILS.

NEW from Kontakt The capability and effect of compressed air in a handy can. g TENSION 67 efficiently removes ( E.M.S. POWER KONTAKT dust and deposits from electronic components, electronic and electrical appara- tus, microscopes, medical SYSTEMS equipment, cabinets, etc. Abso- '} lutely no spray residues. No compressed airline needed. -. With plug-in nozzle even blows miliiisem,` around corners. Ready for use `asr,. in the service kit. Kontakt 60 Dissolves oxides and sulphides, re- moves dirt, oil, resin and traces of metal abrasion. Protects against erosion. En- sures perfect contacts. Kontakt 61 Special cleaning, lubricating and anti- corrosion fluid for NEW (non oxidised) and specially sensitive contacts. An ex- cellent lubricant for all electrical and electro -mechanical systems. Solve all your Power Problems by contacting Spray Wash WL E.M.S. A rapid cleaner for reliable washing and degreasing of electrical equipment and E.M.S. in components. For removal of dirt, grease, specialise systems to eliminate your oil, soldering residues and other impuri- power problems. ties.

Products range from 35VA switched square wave ALSO AVAILABLE: Power Packs to 1KVA fully uninterruptible sine wave systems. A COMPLETE RANGE OF INDUSTRIAL AEROSOL SPRAYS SK10 Soldering Lacquer, K75 Cold Spray, K70 Plastic Spray, K88 Oil Spray, K701 E.M.S. also manufacture chargers which range up Vaseline Spray, K90 Video Spray, K33 Graphite Spray, K100 Antistatic Spray, K101 Fluid Spray and, of course, Positiv 20 positive photo resist for printed to 60 amps. circuits.

For further details please contact: Details from: E.M.S. Manufacturing Limited Chairborough Road Special Products Distributors Ltd. 81 Piccadilly, London W1V OHL High Wycombe Tel: 01-629 9556. Telex: 26500 (answerback RACEN) Bucks Cables: Speciprod, London W1 Tel: (0494) 448484

CIRCLE 11 FOR FURTHER DETAILS. CIRCLE 32 FOR FURTHER DETAILS. 54 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com OPTICAL FIBRES Fibre optics by Brett Wilson communications

Part 3 - Systems and applications. This last article in this three-part series looks at the range of applications in which fibre optic sys- tems are being introduced.

In view of the very low energy tector receivers, Fig.2. Where levels involved in fibre optic Public telephone network the main consideration was not transmission they are best suited maximum repeater spacing to the transfer of information Because of the very low band- I.e.ds have normally been used rather than power. It is in this area width required for each telephone because of their lower cost, that they are making a major handset, it is doubtful if there will resulting in repeater separations impact, even at this relatively ever be an economic need to of around 6km in the 30-45Mbit/s early stage of their development. replace the usual copper wire and 7km in the 100-140Mbit/s Indeed, British Telecom has pairs with an optical fibre. (This range'. The latest phase of the recently announced that it will be position changes of course when first generation systems has seen ordering no more coaxial cable considering an integrated data the use of the dispersion null at after 1985 for the telephone network including telephony, 1.3µm with low attenuation fibres network, due to their growing television and data link). The resulting in even greater spacings commitment to fibre optics. It major fibre application is in the for medium data rates. has been predicted that over half area of junction and trunk tele- An additional advantage aris- of all trunk telephone traffic will phone transmission where the ing from the increased repeater be carried on optical fibres by traffic has been concentrated and spacings is that well over 50% of After a post doctoral fellowship 1991. multiplexed to a much higher data the connections between major at Manchester University, and There is no difficulty in princi- rate. Here experience has shown switching centres within cities a year teaching in Baghdad, ple in substituting optical fibres that the first generation systems can now be made repeaterless, Brett Wilson returned to for copper cables in the majority have fallen into several broad per- with an increase in reliability and Manchester to work on optical of data transmission applic- formance areas, as we would decrease in cost. This has also position detectors and been the pattern of experience in sensitive non -contact current ations. After multiplexing the expect from the previous look at measurement. He then data in the normal manner the fibres, sources and detectors. N. America, Europe and Japan. lectured at Nottingham electronic modulator drives a The majority of installations Optical fibres are not usually University, where he's been light emitting or laser diode have operated at a wavelength of laid as a single fibre. Instead a concerned with novel uses of rather than a coaxial line ampli- around 0.85pm using medium number of them, eight being op -amps in addition to fibre fier, Fig.1. At the receiving end performance graded index fibre common, are made up into a cable optics, and is now back in the signal can be treated again in with silicon avalanche photode- around a steel strength member. Manchester, this time at the conventional manner once it UMIST. His Ph.D. was on a is beyond the detector preampli- Information high-speed laser stroboscope Output Information for magnetic bubble research. fier. In small systems the addi- O Encode - amplifier tional complexity is minimal, whilst complex data systems such i as telephone trunk routes can actually be simplified by adopting Modulator I Decoder optical fibres as the transmission driver medium. The range of telecommunic- i ations applications for fibre optics Modulator Preamplifier can be conveniently divided into Electronic three areas systems -public telephone network -broadband entertainment Optical systems Transmission and information services Source Detector Fig.l. Principal components of -computer local area medium an optical communications networks. system.

ELECTRONICS & WIRELESS WORLD JULY 1984 55

www.americanradiohistory.com OPTICAL FIBRES

Most of the cables are installed in elastomer and an external pol- ideally suited to the characteris- existing ducts where their small yethylene coating. Water resist- tics of optical fibre technology. size is a great advantage in an ance and electrical power in the Most of the field trials that already crowded environment. form of a constant current for the have been conducted around the Lengths of around lkm of optical repeater electronics is obtained world (UK, USA, Canada, Ger- cable are usually pulled through via a continuously welded copper many and Japan) to assess the the ducts before being jointed cylinder jacket. The overall potential of fibre optic transmis- 0 85u led. }140 I Mbit/s using V -groove or arc -fusion diameter of the completed cable sion links have relied on some form of analogue intensity modu- 1000 techniques. will be just over 20mm; under 10 100 lation of thelight source. The rea- BIT RATE (Mbitsl For second generation sys- half the diameter of the previous tems effort is being concentrated copper coaxial TAT 7 cable. son is simply that frequency divi- Fig.2. Longer wavelength on long -haul high-speed commu- The underwater repeaters, sion multiplexing onto ever laser systems offer the best where the cost is which have not yet been finalised, higher frequency carriers has combination of repeater nications affected strongly by repeater will probably use up to four laser been the traditional manner in spacing and data rate, but which to multiplex telephone, spacings. Hence it is natural to transmitters, one actively shorter wavelength l.e.d. and by extension, television use laser driven monomode fibres employed and the other three as systems are less costly. channels. Analogue intensity in their minimum dispersion standby units. This is thought to modulation performs satisfactor- region at 1.311m. Repeater spac- be necessary because of the ily with coaxial cable techniques ings of 20km are typical with data limited lifetimes so far achieved but does not ideally suit rates of 400Mbit/s being with i.l.ds coupled with the enor- optical sources since in general they are employed (NTT, Japan) over mous cost of underwater repairs. routes ultimately several thou- Optical detection is performed by non-linear unless pre -biasing techniques are employed. sand kilometres in length2. Most an InGaAs p -i -n diode rather than Even then circuit complexities arise field trials, however, have been an a. p. d. because of the complex- conducted with shorter routes of ity of providing a high voltage because the lasing threshold of a semiconductor injection laser is around 1001än. supply to an a . p. d. A silicon bipo- temperature sensitive. The best The promise of low -loss trans- lar transimpedance preamplifier properties of the optical trans- mission with high data rates is is used in preference to a GaAs obviously of great importance in unit because as yet silicon fabri- mission systems discussed in the previous articles are brought out the area of underwater telephone cation technology is more proven by binary intensity modulation, cables. In addition, the lower than that required for GaAs. i.e. off. For a inte- weight and smaller size of optical Active waveform retiming is car- on or fully grated network this is fibres compared to copper coaxial ried out at each repeater by clock data obvi- ously the best form of modulation cables is of great economic and extraction circuitry. Various handling importance considering monitoring circuits transmit as it renders unnecessary any form of modulation change long lengths of cabling, operational information back to the between the computing section 6500km, involved the shore based stations. approximately and the distribution section. in a transatlantic crossing. The However, there are certain various agencies concerned have Broadband information services bandwidth penalties to be paid mapped out the nature of the first when attempting to encode tv optical fibre transatlantic tele- The use of optical fibre technol- channels in a completely digital 8, to phone cable, TAT be ogy has been much discussed format. in an analogue format a installed in 1988. with respect to the 're -cabling of PAL colour signal will occupy a multi- It is intended to operate Britain', where a single unit on bandwidth of 6MHz, but with ple optical fibre pairs at 280Mbit/ the customer's premises would eight -bit p.c.m. digital encoding s, 35,000 two-way equivalent to provide access to a wide range of this increases dramatically to voice channels, with repeater Fig.3. Tree and branch tv channels and interactive infor- around 120MHz to satisfy sampl- topology is best suited to spacings of more than 35km. mation service. Connections ing requirements at an appropri- broadband broadcast Monomode fibre will be used between the customer's unit and ate multiple of the colour subcar- distribution in contrast to the excited by 1.3pm injection laser the distribution centre can obvi- rier. In other words a single digi- star configuration which diodes. Strength is provided by ously be of the ordinary copper tal tv channel would occupy the permits much easier the usual arrangement of central coaxial cable type or by optical equivalent of a 140MHz optical installation of up -stream and . peripheral steel elements fibre telephone trunk selection signalling. fibres, either of which could be circuit! with cushioning from interstatial arranged as a tree and branch, or Even with bandwidth compres- Distribution switched star topology, both of sion techniques this figure is 2 centre which are shown in Fig.3. The only reduced to approximately switched star system is currently 70MHz. Clearly there is a prob- favoured as offering the greatest lem in providing every user in a future potential for system tree and branch network with an expansion. In contrast, over 80% optical fibre and receiver elec- of all American coaxial cable sys- tronics with sufficient bandwidth 4 user tems use a tree and branch topol- at an affordable price, capable of bringing in perhaps 10 or 20 ogyOwing to the inherent diffi- simultaneous tv channels and culties and signal losses involved ancillary services.

2 in splitting the signal in an optical A switched star network over- fibre, it is likely that its use in a comes many of these problems by 5 4 6 tree and branch network would be employing upstream low speed restricted to the main trunk. In a signalling, so that customers may switched star network, however, indicate to the star switching cen- Star user topology Tree and branch the signal paths are a series of tre which service or channel they point to point transmissions want at any given time. The 56 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com switching centre then routes the Where a super primary link to required signal down the cus- the super head end is relatively tomer's line, which obviously short it is intended to utilise only need sufficient bandwidth 50µm graded index fibre driven Super for one service at a time. The pri- by a 0.85µm semiconductor head end mary routes from the main con- laser. On the longer super pri- trol centre to each of the switched mary links it may be necessary to star centres must of course be use 1.3µm monomode fibre. <20km Super primary links able to carry the full range of ser- Each link will be composed of ten w.s.p.-wideband switching point w s.P) vices simultaneously. fibres. There will be five fibres for ( up to 300 users per British Telecom has gained a full range of off -air and subscrip- Maximum valuable experience in this field tion television, with each fibre of Hub site with their Milton Keynes 'Fibrevi- carrying four frequency multi- 120 w s p s Users sion experiment in which 18 plexed frequency modulated tv houses received a full range of channels, resulting in a total of 20 Primary links services via optical fibres3. Based broadcast channels. <5km on this experience, BT are pro- Of the remaining five optical posing a 'Multi -star Wideband fibres constituting the 10 fibre Secondary links <500m Network' offering link, three will be for dedicated tv bandwidth channels such as on - - broadcast tv, d.b.s. tv, demand video library and video- subscription tv, pay per view tex, again multiplexed four per -videotex; alphanumeric fibre. Each fibre will be optically Users and photographic modulated by analogue intensity Users -individual video, e.g. library modulation. The remaining two fibres will carry switching and discs control signals one upstream users within a local geographical Fig.4. British Telecom's data services. - wideband -home and one downstream. area to shared computing proposed multi -star resources. The two most com- network will use fibre optics in The proposed topology of the At a hub site the optical signals short final link to mon topologies have been the all but the network is shown in Fig.4. The are simply regenerated and rel- the customer. contended bus with collision originating site, or super head - ayed out to the wideband switch- detection (Ethernet) and the ring end, would house the data library ing points. A firm decision does structure, as in the Cambridge as well as the off-air tv and video not seem to have been taken ring, Fig.5. Many of the features equipment. This site would be whether to use an injection laser of optical fibres make them connected by optical fibre 'super diode along with an avalanche attractive for use in lans but primary links' up to approxi- photo detector at 0.85 pm on a usually only after some modifica- mately 20km in length with no graded index fibre for the primary tion from a coaxial cable design repeaters, to a number of hub links, or whether to upgrade an has been implemented. sites. Each of these hub sites i.l.d. or 1.e.d. at 1.3prn with a In the Ethernet system each would simply regenerate and dis- p -i -n fet receiver, again using station is connected to the coaxial tribute the information over 'pri- graded -index fibre. What is cer- bus via a bidirectional passive mary links' to a maximum of 120 tain is that in the primary links the tap, making insertion of a new wideband switching points where five fibres containing the 20 work station a relatively simple the real intelligence and flexibility broadcast tv channels will be opti- matter. Each station attempts to The full cally tapped to serve several of the system resides. transmit its message when the range of services is available to all switching points. The primary bus is quiet. If a message collision the switching points, but pro- links between hub sites and is detected transmission is grammes are only transmitted switching points will be less than stopped and retried a short time down the 'secondary links' to each 5km in length. later. With fibre optic technology customer when they demand a Within each wideband switch- it is relatively difficult to make service. ing point a microprocessor -con- specific tv channel or passive couplers without an It is envisaged that each wide- trolled matrix type of routing unnacceptably high loss, thus be switch will route the 20 broadcast band switching point will able restricting severely the number of customers tv channels as demanded by each Fig.5. Ethernet -style local to service up to 300 users that may be attached to the with cable runs up to 500m. Even of up to 300 customers. Each cus- area network uses a tomer will be able to receive bus. To overcome this, Fibernet, bi-directional data highway though the Fibrevision trial used the optical version of Ethernet, approach compared to the optical fibres for these secondary two channels simultaneously. uses a central passive star cou- enclosed path of a Cambridge links it is considered that cost still Requests for individual video pro- pler to enable 16 users to com- ring lan. favours small bore coaxial cables, grammes in the form of discs will at least for the next few years. be relayed up through the system Eventually the secondary links to the super head end, which will will also be optical fibres. Each then replay on one of the dedi- customer will be able to receive cated channels back down two simultaneous tv channels and through the hub site and the cus- a range of f.m. stereo sound tomer's own switching point and encoded by frequency division out on to the customer's own sec- multiplex on their 120MHz band- ondary link. width secondary link. A customer termination unit, a small set -top Local area networks u.h.f. converter and a remote control handset completes the A Ian is a communications information/control chain. network connecting a number of ELECTRONICS & WIRELESS WORLD JULY 1984 57

www.americanradiohistory.com OPTICAL FIBRES

At each station a message packet Such sensors would exhibit many may be attached to the appropri- potential advantages, usually for Star ately numbered 'wagon' slot after the same reasons as in commu- conn- the locomotive has passed. ector nications, namely; electrical iso- Locomotive Because the locomotive is a syn- lation, freedom from electromag- generator and chronized event, re -triggered by netic interference and lack of synchronizer the reception of a previous locomo- fire risk in sensitive areas. tive back at the terminus R, the \!R Stations The range of parameters that message delay through the sys- can be measured can conveni- tem is tightly bound. ently be classified into At the far end of the highway, T the star coupler distributes the Outwa d bound optical highway - mechanical (force, pres- trains of information back to the sure, deformation) R - Receive S - Sense T- Transmit receive terminals of all the -electrical (field strength, stations. Just as there can be polarization, current) Fig.6. D -Net optical lan municate with each other. more than one train on the line - magnetic (field strength, combines a data highway and At higher data rates, such as between Manchester and Lon- polarization) a star return, making it more can be supported on fibre optics, don, so will D -Net support more -temperature. like an open ring. the efficiency of a message con- than one train at a time, given a tention scheme starts to fall detailed knowledge of the maxi- In most cases these measurands rapidly. The transmission delay is mum propagation time, bit slot produce changes in the refractive not deterministic and the network lengths and number of stations. index or in the absorption of the cannot guarantee to support real This configuration seems fibre, but some of them will time transmission such as tele- extremely attractive at very high modulate luminescence effects. phony. speeds beyond 100Mbit/s The table presents information The alternative is a ring because it retains a higher effi- on the categories of modulation network. This structure suits the ciency than a passive bus and detection that may be used nature of fibre optics better arrangement. with each of the five different opti- because it is essentially a series of cal parameters. point to point transmissions. Fibre Some of the most sensitive References the signal is regenerated at -optic sensors 1. J. E. Midwinter, First generation trunk Since fibre sensors constructed use an transmission systems: capabilities and each station there is little trouble interferometric technique in limitations. IEEEJournal on selected areas with power levels. To increase One of the aims research in Communications, vol.SAC-1, 1983, of work- which the optical phase shift pro- pp.381-6. the reliability of communications ers in the field of fibre optics has duced in a fibre by interaction 2. E. Iwahashi, Trends in long wavelength with respect to fibre failure for been to stabilize the transmission single -mode transmission systems and with the measurand is compared demonstrations in Japan. IEEE Journal of example, a double ring may be of information along an optical to the phase of a reference arm. Quantum Electronics, vol.QE-17, 1980, easily employed. fibre against commonly encoun- pp.890-6. Rotation sensors (gyroscopes) 3. J. R. Fox, D. I. Fordham, R. Wood and While commercial versions of tered environmental changes, for with sensitivities around 10-2 D. J. Ahern, Initial experience with the Mil- optical ring lans are available, example; pressure, temperature, degrees per hour are currently ton Keynes optical fibre cable tv trial. IEEE is focus- Transactions on Communications, development attention strain, etc. they have succeeded operating. Similar techniques can vol.COM-30, 1982, pp.2155-62. ing more on structures such as to an extent where, in many be applied to phase shifts pro- 4. C. W. Tsend and B. U. Chen, D -Net, A D -Net where high data rates and applications, fibre optics is, or new scheme for high data rate optical duced by pressure changes on the low Fig. 6 LANs. IEEE Journal on selected areas in delays are obtainable'. will soon be, the preferred trans- fibre, resulting in acoustic hydro - Communications, vol.SAC-1, 1983, shows an outline of D -Net in its mission medium. In contrast, at pp.493-9. phone sensors with higher sensi- 5. A. L. Harmer, Review of optical fibre star coupled form with a single the opposite end of the applic- tivities than piezoelectric types. sensors. IEE Colloquium on Optical Fibre star connector at the far end of the ations spectrum, there have been Sensors, digest 1982/60, paper 1/1, Lon- Magnetic fields can also be don, 1982. outward bound bus. The trans- efforts to exploit variations in the detected by phase techniques if mitter T sends regular 'locomo- same transmission parameters the optical fibre is coated with a tive' header signals out along the with respect to environmental magneto restrictive material. highway which are detected by all disturbances in order to produce Mechanical displacement can stations at their S -terminal. a range of fibre optic sensors. be measured by several arrange- Optical modulation and detection schemes, as classified in an informative survey of fibre -optic ments of intensity sensing transducers (ref.5). between movable fibre ends, either with an orthogonal or a Parameter Mechanism Detection Examples slant cut. Vibration detection of a movable membrane from ref- Coherence Interference between signal Fringe counting or phase shift Fibre gyroscope, hydrophone and reference fibre, or different detection. muitimode gauge for dynamic lected light is also popular. One of propagation modes in multi - strain measurement. the most widespread uses of mode fibres. amplitude detection is the sens- Amplitude Modulation of transmitted light Analogue or digital. Strain/pressure gauge using ing of a Gray code from an by absorption, emission or modulated micro -bending loss. encoded disc or shutter, with res- refractive index change. Optical encoders. olutions available down to 101un. Wavelength Spectral dependent variations Amplitude comparison at two Temp. measurement by Finally, modulated microbending of absorption, emission and fixed wavelengths, or analogue variable Fabry -Perot cavity refractive index. signal for scanned wavelength. birefringent crystal loss can be used by clamping a semiconductor bandgap shift fibre between two plates with a periodic mechanical grating. In Time Transient absorption or Time -delay pulse analysis. Temperature gauge by time decay Resolved emission behaviour. of rare earth ion fluorescence. general amplitude detection Transit time of closed fibre loop Nuclear radiation diagnostics methods are less sensitive than with feedback. using Cerenekov light. phase modulated sensors and in Polarization Changes in the gyratory Polarization analyser and Faraday rotation magneticfield addition suffer from unwanted optical tensor. amplitude comparison. transducer for non -contact current measurements. and variable signal attenuation and temperature problems. 58 ELECTRONICS & WIRELESS WORLD JULY 1984

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Speaker outlets for 4, 8 or BSR 12 Volt P267 Belt Ceramic 24 GOODMANS HPO/DISCO 12in 120 8/15 £29.50 £2 16 ohms. Four inputs, 20 mv, 50K ohm. Individual volume controls 1 1 ir1 GOODMANS HP/BASS 15ín 250 £72 £4 "Four channel" mixing. Slave output. 16"x8"x51/". Wt - BSR Budget Rim Ceramic E18 GOODMANS HPD/BASS 18in 230 £84 £4 14lb: Master volume control. 240V A.C. Post £2. BSR Deluxe Rim Ceramic £20 100 Volt Line Model, 150 watt £114. MONO SLAVE, 150 watt £80. RCS STEREO PRE -AMP KIT. To Inputs for BSR Deluxe Rim Magnetic £26 build. Baker Stereo Slave 150 + 150 watt 300 watt Mono £125. Post £4. high, medium or low imp volume GARRARD 6200 Rim Ceramic £22 control £3.50 and PC Board. Can be ganged for multi -channel Post 65p BAKER MOBILE PA AMPLIFIER. All transistor, 60 watt RMS, 12v THE "INSTANT' BULK TAPE ERASER £11.50 Post 95p DC & 240v AC, 4 inputs 50k. Aux + 2 mics for sizes of tape reels. AC mains. Suitable cassettes and all MAINS TRANSFORMERS Post + 1 phono. 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Tapped outputs available Price Post PA CABINET SPEAKERS, Complete. 8 ohm 60 watt 17x 15x9in. ALUMINIUM BOXES. 4x4x11/2 £120. 4x21/x2 £1.20. 3x2x1 £120. 2 amp. 3. 4, 5, 6, 8, 9, 10, 12, 15, 18, 25 and 30V £8.00 £2 £27. Post £4. 4 or 8 or 16 ohm 75 23x 15 x 11 in. £52. 90 watt 1 amp. 6, 8, 10, 12, 16, 18, 20, 24, 30, 36, 40, 48, 60 £6.00 £2 watt 6 x4x 2 £1.90. 7x 5x 3 £2.90. 8 x 6 x 3 £3. 10x7x303.50. 12x5x3E310. 2 amp. 6, 8, 10, 12, 16, 18, 20, 24, 30, 36, 40, 48, 60 £10.50 £2 32 x 15 x 11 in. £71. 150 watt £80. Carr. £10. Black vinyl covered. 12 8 x 304.30: 9 4 x x x 4 £3. 3 amp. 6, 8, 10, 12, 16, 18, 20, 24, 30, 36, 40, 48, 60 £12.50 f2 POTENTIOMETERS 5k/2meg. LOG or LIN. L/S 50p. DP 90p. Stereo US 5-8-10-16V. 1/2 amp £2.50 £1 0-8-12V. 5 amp £5.00 £1 Post £2 each. 1R BAKER LOUDSPEAKERS 6V. amp £2.00 £1 15-0-15V. 1 amp £4.00 £1 £1.10. DP £1.30. Edge Pot 5L SP 45p. MODEL INCHES OHMS WATTS TYPE PRICE 6-0.6V. 11/2 amp £3.50 £1 15-0-15V. 2 amp £5.00 £1 DISCO/GROUP 10 8-16 50 PA £18 MINI -MULTI TESTER £7.50 Post 50p 9V. 400ma £1.50 £1 20V, 1 amp £4.00 £1 9V. 3 amp £4.00 £1 20-0-20V. 1 amp £3.50 £1 MIDRANGE 10 8 100 MID £25 4000 o.p.v. 11 Pocket size moving coil instrument. 9-0-9V. 50ma £1.50 £1 0.12-27V. 2 amp £4.00 £1 MAJOR 12 4-8-16 30 HI-FI £16 25, 250, AC volts 10, 50, 500, 9-0-9V. 1 amp £3.50 £1 1 ranges: DC volts 5, 500. 20-40-60V. amp £3.50 £2 SUPERB 12 8-16 HI-FI f26 600K. 10-0-10V. 2 amp £4.00 Ei 25-0-25V. 2 amp 6.50 £1 1000. DC amps 0-250µA, 0-250mA. Ohms WOOFER 12 e 80 HI-FI £25 10.30-40V. 2 amp £5.50 £1 24V. 5 amp Twice £12.00 £2 AUDITORIUM 15 8-16 60 Woofer De Luxe Range Doubler MULTI -METER 12V. 100ma £1.50 £1 30V. 11/2 amp £5.00 £1 £37 12V. 750 ma £2.50 £1 30V. 5 amp and DISCO/GROUP 12 4-8-16 45 PA £16 50,000 o.p.v. 7 x 5 x 2 i n. 50 Micro Amp £ 21 12V. 3 amp £4.50 £1 17-0.17 2a £4.50 £2 DISCO/GROUP 12 4-8-16 75 PA £20 43 Ranges, 1,000V, AC -DC, 20 MEG 10 amp DC Post £1 12-0-12V. 2 amp £4.50 £1 35V. 2 amp £4.00 f1 DISCO/GROUP 12 8-16 100 PA £26 DISCO/GROUP 15 8-16 100 PANEL METERS 50µa, 100µa, 500µa, 1ma, LOW VOLTAGE ELECTROLYTICS PA £35 500mi- 12V 15p; 25V 20p; 50V 30p. 1200mF 76V 80p. REPAIR service to most Baker loudspeakers. SPEAKER COVERING. 5ma, 50ma, l00ma, 500ma, 1 amp, 2 amp, 5 amp, 25 volt, 1000mF 12V 20p; 25V 35p; 50V 50p; 100V £1.20. Samples S.A.E. CABINET WADDING 18in wide 35p ft. VU59X53X34mm. Stereo VU 82X41x25mm £5.p.p.50p 2000mF 30V 42p; 40V 60p; 100V £1.40; 1500mF 100V £1.20. 2500mF 50V 70p. 3000mF 50V 65p; 4700mF 40V £1. MOTOROLA PIEZO ELECTRIC HORN TWEETER, 33gin. square £5 RCS SOUND TO LIGHT CONTROL BOX CAPACITORS WIRE END High Voltage 100 watts. No crossover required. 4-8-16 ohm, 73 x31,Éin. £10 Complete ready to use with cabinet size 9x3x5in. .001, .002, .003, .005, .01, .02, .03, .05 mid 400V 10p. HORN BOXES, complete 200 watt £30. 300 watt £35. Size 3 channel, 1000 watt each. For home hi-fi or disco L£ 1 MF 400V 14p. 600V 15p. 1000V 25p. 16x6x6in. Black vinyl covered with handle Post f4. OR KIT OF PARTS £19.50 Post £1 .22MF 350V 12p. 600V 20p. 1000V 30p. 1750V 60p. .47MF 150V 10p. 400V 25p. 630V 30p. CROSSOVERS. TWO-WAY 3000 c/s 30 watt £3. 60W £3.50. 100W £4. THREE-WAY 950 cps/3000 cps. 40 watt rating. £10 BATTERY ELIMINATOR Mains to 9 volt D.C. 400MA. HIGH VOLTAGE ELECTROLYTICS £4.60 watt £6. 100W LOUDSPEAKER BARGAINS. Please enquire, many others in Stabilised, safety cutout, 5 x 31/4x 21/2in. £5. Post £1. 2/500V 45p 32+32+16/350V 90p 8+16/450V 95p stock. 4 ohm, 5in, 7 x 4in, x 16/450V Sop 100+100/275V 50p 16+16/350V 80p £2.50; 61/in, 8 5in, £3; 8in, £3.50.61hin 70W, £16. DISCO GRAPHIC MIXER EQUALISER £112. Post £2. 150+200/275V 50p 32+32/350V 85p 8 ohm, Altin, 3in, £2; 5x3in, 6x4in, 7x4in, 5in, £2.50; 3in, 10W E4 20/500V 75p x 4 channel stereo, 5 band graphic, red + green LED. VU 32/350V 45p 32+32+32/450V 95p 20+20/350V 75p 8 5in, £3; 8in, £4.50; 10in, £5; 12in, £6. Bin 25W £6.50. 60W £13.50 display, headphone monitor. 32/500V 95p 47/350V 75p 50+50/300V 50p 15 ohm, 21/4in, 3192in, 5 x 3in, 6 x 4in, E2.50.61hin 10W £5. 8in £4. 10in £7. Deluxe Model, 5 channel 7 band graphic. £128. 125/500V E2 8+B/500V £1 50+50/350V B0p 25 ohm, 3in, £2; 5 x 3in, 6 x 4in, 7 x 4in, £2.50. 120 ohm, 31/4in dia. £1. EMI 131hx8in. Bass & Tweeter 4 or 8 ohm 10 watt El op fl Dept 1, 337 WHITEHORSE ROAD, CROYDON RADIO COMPONI NT SPECIALISTS Open 9-6. Closed all day Wed. Open Sat. 9-5. Books and Components Lists 32p stamps. (Minimum post/packing charge 65p.) Access or Barclaycard Visa. Tel: 01-684 1665 for SAME DAY DESPATCH. Cash prices include VAT. WW -7 CIRCLE 44 FOR FURTHER DETAILS. B. BAMBER ELECTRONICS Marconi Modulation Meter Type TF2301 A £330. Pye Base Station Type F30 AM High Band 8 Low Band from .....£220. Airmec Modulation Meier Type 409. £120. Marconi RMS AC/DC Voltmeter Type TF2607 £185. Pye Base Station Type F401 AM High Band £250. Servomex AC Voltage Stabiliser Type AC2240 vac 9amp £45. Marconi RF Power Meter Type OA 7024/4 £195. Pye Base Station Type F17 FM High Band £250. Servomes AC Voltage Stabiliser Type AC7240 vac 40amp £95. Marconi UHFAttenuator Type TF 2168 £100. Pye RepoderType MF6 AM High Band 8 Low Band £90. Hewlett Packard SweepGenerator Type 692D1.8 -4.2Ghz £300. 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Instrument Fans 41 /2"x 41 l2" 240vac £3 each,110vac £1.50 each. TF8014/1 Electrohome Video metal £85 9' Monitor case £50. Garrard Car Cassette Player Mechanisms, Stereo Head £2.50. Aztec 20' Video Monitor metal case Marconi Standard Signal Generator 15Khz - 440Mhz £40. Tektronix Oscilloscope Probes £10 each. Marconi UHF SIgnalOeneratorType TF1060/2450 to 1200MHz Type TF867 £85. £150. Pye Pocketphone Re Ni -Cad Batteries Mr £1.00. Marconi VHF Alignment TF1104/1 Marconi RC Oscillator 20Hz- 200Khz Type TF 1101 £85. OsdlloseopeType ...... £150. Mullard Van -cap TV Tuners Type ELC 2003 Ex. Brand New Sets £3.50. Sander Oscillator Marconi AM/FM Signal Generator Type TF 995A/5 £230. Type CLC2-4. 2 to 4.56Hz £95. Pye Cambridge/Vanguard 18 Way Control Leads £4.00. Marconi 100 Marconi VHF Signal Generator Type TF 10648/5M £125 Wan Tate AnauatoeTypeTM5280.150 to 185MHz £40, Sony 1/2" Video Tape 5" Reels £2.00. Kleer Vibration MeterType Marconi Tx & Ra Output Test Set Type TF 1065 £85. amel 2502 £50. BNC Plugs 75 ohm 50p. each. Pye Aerial Tuner Type Pye Modulation Meter 68-510Mhz Type MM1 £60. Unit ATU 4.2 to9MHz. Pre-set £15. IC Test Clips 28 pin 840 pin £2.00 each. Airmec Sweep - A.I.M. Electronics PulseGeseratorwith Clock Generator, £65. Signal Generator 20Hz 200Khz Circulators 590 - 720 Mhz' N' sockets £25. Type Ronde 8 Z -g Diagraph Type BN to 352 £45. Schwan 3562300 240MHz £85. Transistors Type 2N3055 4 for £1.00. Marconi Universal Bridge Type TF 8688 £110. Telequlpment000l11oacopeTypeS32A, DC to 3MHz £65. Transformers 30 volt 41 amp £1.00. EMI Wide Band Amplifier Plug-in Type 7/1 £25. Alrmec Millivolt Meter Type 301A. £75. Transformers 36 volt 431.5 amp Advance Audio Generator Type Hl, Advenu Oscilloscope Type 0S15A LP Tube 3Mhz £85. £20. Transformers 600-0-600 00 250mA plus 460-0-460 0 230mA.. £10.00. BruelO Kloer Microphone Amplifier Type 2604. Advance Oscilloscope Type 0S25ATwin Beam 3Mhz £125. £50. 'Variacs' 2 amp, 5 amp. 8 amp. 15 amp, 20 amp, 25 amp. Airmec Sweep Signal Generator Type 352.20 Hz to 200 KHz,. General Radio Microwave Oscillator Type 136061.7-4.1Ghz £125. £65. Loudspeakers Richard Allan Type CP12, 12' 15 ohm ...... £6.00. Bells Variable Power Unl10 to 50V at 2 amp, £40. Wayne Kerr Component Bridge Type 8521 £45. Semiconductors at 5p each: BTRSllrenown Antl-SlaticendCoedudjve MarcontOacillator Type TF 124640Khz -50Mhz £95. Footwear Tester, £25. AC128, BCV65E. BC173C, BC328, BC149, BC113, NKT12, ZTK213, 82517, Dawetrue RMS Valve Voltmaler Type 612A, £20. Wendel & Go0ermann Level Meter Type TFPM 4310Khz-14Mhz . £60. 184007. Tektronix Time Mark Generator Type 180A £ 125.

P. & P. or Carriage and V.A.T. at PYE POCKETFONE PF1 EDDYSTONE RECEIVERS RADIOSONDE RS21 15% on total must be added to all orders. METEOROLOGICAL BALLOON UHF RECEIVER Model 770R £120 each. Callers very welcome, 440-470 MHz, Single Channel, int. strictly be- TRANSMITTER tween 9 a.m. and 1 p.m and 2 and speaker and aerial. Supplied complete with Water Activated Battery, contains and service GEC RECEIVERS 5 p.m. Monday to Friday inc. with rechargeable battery all-weather sensors, fully solid state, £5 manual, £8 each plus E1 p.p. plus V.A.T. Barclaycard and Access taken Model BRT 400 each. each plus £1 p.p. plus V.A.T. 0120 Official orders welcome ww27 BARCLAYCARD 5 STATION ROAD, LITTLEPORT, CAMBS CB6 10E PHONE: ELY (0353) 860185 CIRCLE 65 FOR FURTHER DETAILS.

60 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com CASSETTE RECORDER Micro -controlled by A.J. Ewins cassette recorder -2 Description of cassette recorder for use with microcomputer continues with description of f.s.k. modulator and demodulator.

The main criteria for choosing a using complex, but well known, mum rate at which the switching suitable encoding technique for techniques called Miller or delay between the two frequencies can recording serial data from the modulation. However, all these take place; somewhere between a output of a microcomputer very high speed designs, includ- fifth and a tenth of the mean of the (RS232 or t.t.l. levels) are, in my ing my own, rely on the ability to two frequencies is a good rule -of- opinion, reliability, circuit sim- record single high/low or low/ thumb. Using a good set of plicity and, perhaps most import- high signal transitions. The suc- record/playback electronics I set antly, the ability to be used with cess or otherwise of the technique my sights cautiously on a mean any good set of recording/play- depends not only on getting the frequency of 10kHz, i.e. 9kHz back electronics. The microcom- `electronics' right but also on tape and 11kHz for the `low' and 'high' puter user is primarily concerned quality and the mechanical opera- frequencies. A bit rate of 2400 with reliability and ease of use of tion of the cassette deck. It is very has a highest frequency content any encoding technique. He is not sensitive to imperfections in the of 1200Hz when a train of succes- interested in very high speed tape quality, dirty tape -heads and sive ones and zeros are being techniques if half the time the indifferent transport of the tape transmitted. Thus this figure was data is recorded or played back across the head. In my opinion taken as the highest rate that incorrectly; or if the tape -recor- the techniques are unlikely to be could be easily be transmitted der settings need constant successful unless only the best using the two nominal frequen- adjustment. tapes are used, the cassette deck cies of 9kHz and 11kHz. (Actu- There have been a number of is of the highest quality, and the ally, by pushing the mean f.s.k. designs in various electronic tape -heads are regularly cleaned. frequency up to 12kHz and careful magazines for 'high' speed A technique that is far less design of the demodulator stage, recording techniques. The fastest sensitive to these three sources of it should be possible to record at of these, of which I am aware, was error is frequency shift keying. 4800 baud. Alternatively, it for 4800 baud. I also have had Using a few modern i.cs, a vol- should be possible to drop the some experience of designing tage -controlled oscillator and a mean frequency to 6kHz and still suitable encoding techniques for phase -locked loop, a modulator be able to record at 2400 baud. ) high speed serial data recording and demodulator are easily and am therefore very aware of designed that are easy to set up F.s.k. modulator & demodulator the problems. Readers may recall and reliable in use. In f.s.k., the circuits Fig.6. F.s.k. modulator, based the series of articles, in this mag- output of an oscillator is simply on Signetics circuits but with azine, on a digital multichannel switched between two frequen- The circuits of the f.s.k. modula- triangle to sine converter for tape recorder. In this design I cies; to represent the low and tor and demodulator are shown in greater flexibility in choice of achieved a rate of 22,000 baud high logic states. There is a maxi- Figs 6 and 7. I claim no originality record/playback circuitry.

4-15V

Sk6 1k5 9k1

ttt i/p 1i 1N4148 1n RS232 type i/p 47k 50k 566 1k5 1y 10k 07 Sine-wave 220 220 o/p 3k3 39k 39k

1M 2N3820 1N4148 BC107 BC 107 3n3

Attenuated 15k 12k 1M 1N4148 o/p 1N 10 4168

-15V

ELECTRONICS & WIRELESS WORLD JULY 1984 61

www.americanradiohistory.com CASSETTE RECORDER

Fig.8. Internal layout of for these, being but a variation of 565 p.1.1. circuits published by Signetics in +v their book on the 566 (v. c. o.) and 565 (p.1.1.) integrated circuits. lo To the circuit of the modulator I added a triangular -to -sine wave- o Demod. form converter. This makes the Phase ---v\A. O o/p Amplrfier 3k6 circuit capable of being used with o detector O Ref. a much wider range of cassette Inputs o/p deck recorder/playback electron- o ics, overcoming some of the problems associated with the high -frequency pre -emphasis cir- cuitry. The triangle -to-sine wave V C 0 converter is also a variation of a circuit to be found in the Signetics book. It is possible to adjust the sine wave, total harmonic distor- cl tion, to less than 1% by setting the amplitude of the triangular wave- form correctly. uses the non-linear IDs - VDs transfer characteristic of a p-channel j-fet to shape the trian- gular waveform: The output from it is a little less 1V, r.m.s. with a distortion factor of less than 1% when the input amplitude is cor- rectly adjusted. A distortion meter is the only proper way of achieving the minimum distortion figure, but visual inspection using an oscilloscope can produce a good enough result. A variable or fixed attenuator is used to reduce the sinewave output voltage to a level suitable for recording on the cassette deck's record/playback electronics. The circuit of the f.s.k. Fig. 7. F.s.k. demodulator, The heart of the f.s.k. modu- levels (between 0 and 5V) or demodulator is shown in Fig .7, using Signetics 565 lator (Fig.5) is the voltage con- RS232 type signals (±3 to ± 15V). the heart of which is the 565 phase -locked loop. trolled oscillator i.c. the 566. If both types of input are required phase -locked loop. There is noth- These i.cs are designed to oper- there is no reason why two tran- ing unusual about its design but a ate with a nominal voltage on their sistors should not be used with few comments will be made so modulation input, pin 5, of V5/8 their collectors sharing a common that its operation may be under- below the positive supply rail, i.e. 39k± resistor. It is, of course, stood. The phase -locked loop 7V5/8. A modulation of this vol- important that the transistor of consists of a voltage -controlled tage by ±10% produces a modula- the unused input be in its off - oscillator (an identical v.c.o. to tion of the frequency output by state, i.e. non -conducting. that used in the 566 i.c.), a the same amount. For a V5, of phase -sensitive detector and an Apart from the voltage on pin 15V, Vs/8 is 1.875V. Plus and amplifier with a single stage of 5, the frequency -determining minus 10% of this value gives vol- low-pass filtering. The intercon- components of the 566 i.c. are tages of approximately 1.69 and nection between the various ele- the 9.1k ohm resistor on pin 6 and 2.06V below the positive supply ments of the p.1.1. is shown in the 3. 3nF capacitor on pin 7. rail, i.e. actual voltages on pin 5 Fig.8. When the frequency of the With these chosen values, the of 13.31 and 12.94V. the 1.5kS2 v.c.o. is locked to that of the output frequency for a voltage of 7 and 12162 resistors produce a incoming signal, the output from Vs/8 on pin 5 is f=1.2/(4RC), i.e. nominal voltage on pin 5 of phase 9990Hz. Thus, when the logic the detector (amplified and 13.33V. When the transistor is filtered) applied the input level on the input varies between to of the conducting the 39kS2 resistor is is voltage which low and high, the frequency out v.c.o. that the effectively in parallel with the requires to put of the 566 i.c. varies between v.c.o. produce the 12162, . reducing the effective particular frequency. The voltage about 9 and 11kHz. resistance to about 9.2kohms. applied to the input of the v. c. o. is The voltage on pin 5, when the The output from pin 4 of the also the demodulated output sig- transistor is conducting, is thus 566 i.c. is a symmetrical triangu- nal that we require. For the v. c. o. reduced to a nominal value of lar waveform of about 3V pk-pk to produce a different frequency 12.90V. Thus by switching the with a positive d.c. bias voltage. output, the voltage on its input transistor on and off the voltage The triangle -to -sine wave con- will have to change. This is on pin 5 is modulated by ±10% verter needs quite a large voltage exactly what the p.1.1. achieves; about its centre value of 13.125V. drive and the variable gain stage is when a signal of a different fre- The input stage to the transistor included for this purpose. The tri- quency is applied to the input of has been designed for either t. t.l. angle -to -sine wave converter Continued on page 67 62 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com HIGH RESOLUTION THAT COMES HIGHLY RECOMMENDED. "There is no doubt that theJVC range of ECM And naturally there's a year's full guarantee. colour monitors is excellent value for money .. . If you order your monitor by post, you'll receive it there is no loss in quality of picture after long within ten days by courier service. periods ... and remember, as more and more Simply post the coupon below to: Opus Supplies Ltd., resolution is available with new micros, the need 158 Camberwell Road, London SE5 OEE. Or telephone for a better display will be that much greater." 01-701 8668 quoting your credit card number. Or, of course, High recommendation indeed from Personal you can buy at our showroom between 9.00-6.00pm, Computer News. Meanwhile Acorn User said: Monday -Friday. 9.00-1.30pm, Saturday. "It seems that all `normal' and `medium' 'Microvitec Cub 14" monitor. resolution monitors, including the Sanyo, are To: Opus Supplies Ltd., 158 Camberwell Road, London SE5 OEE. simply inadequate to deal with the Beeb's graphics Please send me: and text output ... TheJVC was excellent, giving High Resolution Colour Monitor(s) at clear, legible results ... Was the JVC better than the £229.95 each (ex. VAT). Microvitec? Would I buy one? Yes to both Connection lead(s) at £6.00 each. questions." I understand carriage per monitor will cost an extra £7.00. Our RGB high resolution colour monitor (580 x (N.B. A High Resolution Monitor including VAT, lead and carriage costs £279.39). 470 pixels) sells for £229.95 (excluding VAT) - that's a I enclose a cheque for £ Or please debit my credit card saving of over £,100 compared with other leading monitors account with the amount of£ My Access/Barclaycard of similar specifications. The unit has a 14" screen and is suitable for the Iplease tick) no is BBC Micro, Electron, Sinclair QL, Lynx, Oric, Apple, IBM Please state the make of your computer and most other leading micros. Name MODEL REFERENCE 1302-2 High Resolution RESOLUTION 580 x 4-0 Pixels C.R.T. 14" Address SUPPLY 220'240v 50/60Hz. E.H.T. Minimum 19.5kv Maximum 22.5kv VIDEO BAND WIDTH 10MHz. DISPLAY 80 characters by 25 lines SLOT PITCH 0.41 m m Opus. INPUT: VIDEO R.G.E. Analogue/rIL Input Telephone us Supplies Ltd. SYNC Separate Sync on R.G.B. Positive or Negative WW 16 EXTERNAL CONTROLS On/off switch and brightness control CIRCLE 34 FOR FURTHER DETAILS. www.americanradiohistory.com SPECIAL FEATURE

SC84 microcomputer play of one dot -row of the charac- continued from page 34 ter generator corresponding to code 000 - which happens to be blank. The latch is reset by the character clock. This latch sup- presses the speckling effect men- tioned earlier, the algorithm being 'any c.p.u. access during output is captured in an eight -bit signals, one to enable the display the fetching of a character code to latch, IC305, by the trailing edge of (so that the screen may be the character latch forces charac- the next carry pulse and held dur- blanked during non -display peri- ter code to zero'. While it might ing the next memory cycle. This ods such as during flyback) and a seem simpler to gate SEL directly allows the eprom to produce the second to indicate when the char- with the video output to produce dot pattern for character zero acter position being accessed blanking, due to the pipelining while character one is being corresponds to the setting of the technique SEL would blank the brought from memory. The trail- controller cursor register. As with display between one and two ing edge of the next carry pulse M lines, these signals will be del- characters too early. occuring 500ns later allows ayed and, taking the example of The v.d.u. memory consists plenty of time for the eprom to the display -enabling signal, they of 6Kbytes of static memory. submit a dot pattern. This pulse must be delayed by one and a bit Address and data lines to the enables parallel loading of the character periods if they are to v.d.u. memory i.cs do not corre- shift register IC307 used to convert become active just as pixels for spond to their specified 'A' or 'D' the dot pattern from eprom into a the first character on the line are numbers but this doesn't matter. serial stream of pixels. Being syn- clocked out of the shift register. The order used was chosen to chronous, the shift register does One enhancement made to the ease p.c.b. layout. After all, if a not load the dot pattern until the Hitachi 6845 is that it is possible data byte is written into memory rising edge of the dot clock, which to delay the output of these two with a particular addressing pat- occurs while the load input is low. control signals by one or two tern, that same byte will be This edge occurs just before the character periods, which saves on accessed when the same address end of the carry pulse and might i.cs. These signals are given a one is applied. The lower 11 bits of the not, at first, appear to be consist- character-period delay and syn- address supplied by the multi- ent with the synchronous philos- chronized by a two-bit latch, plexers are fed to all three memo- ophy propounded earlier as there IC315, which is also clocked by the ries in parallel. The next two is an undefined delay between carry signal. most -significant bits of the add- this clock edge and ending of the At the other end of the system, ress feed a decoder which acti- carry pulse. Note though that it is the 74LS85 four -bit comparator vates one of four output lines. this same clocking edge which produces a signal at pin 6 when The four lines pass to the memory advances the synchronous coun- A13,14 and VDUSEL are low and i.c. enable inputs and the 6845 so ter and thus ends the carry pulse, A15 is high, i.e. an address on the that within the addressing range which must therefore change address bus is in the range 08000 08000 to 09FFF for which SEL is after the rising edge of the clock. to 09FFF and the v.d.u. memory active, the memory is mapped at Also, the required holding time is switched into the memory. addresses 08800 to 09FFF and for the loading signal after shift Note that the four matching com- the 6845 control registers from Fig .2 . A monitor is best for register clocking is zero and the high density text display but a parator inputs are switched so it is 08000 to 087FF. Effectively, the monochrome tv set with minor clocking signal is from a Schottky possible to relocate the area in 6845 only needs two locations, alterations can give gate with a very fast rise time, so memory at which the v.d.u. one to receive the number of the satisfactory results. This the loading of data is assured. appears (switch on=low). The internal register that the c.p.u. modification for With this data stored in the shift address is set up before MREQ by wants to access and one which Ferguson/Ultra 3840, 3845, register the trailing edge of the the Z80 so the comparator signal appears as that register. The fact 3847, 3848, 6840 and 6845 carry pulse loads a new value can activate MEMDIS to inhibit a that it has been allocated another tvs allows the set to be from v.d.u. memory into IC305 system -memory cycle. Further 2046 in the rather coarse decod- switched between computer and the cycle repeats. This means decoding is necessary though to ing is not a loss though, and it input or broadcasts. Numbers that pixel output begins two char- in circles refer to pinson the ensure that this is a memory simplifies both hardware and sof- cathode-ray -tube controller acter periods after the start of a cycle; MREQ is gated so that tware. The standard rom sup- socket. The tv circuits must be scanning period. As mentioned v.d.u. signal SEL only goes low plied programs the system for isolated from the mains (see earlier, the controller also sup- during a true v.d.u. memory standard timing signals and a dis- text). plies some direct video -control access. Select signal SEL does play consisting of 32 rows of 96 several things. It switches the characters each. This means that four 74LS157 multiplexers so only 32 by 96, or 3Kbytes, of that they direct bus address lines v.d.u. memory is required and, 560 Junction of into the v.d.u. memory and con- for the basic system IC304 may be v d u. q o--y\Me.- R 127g R128 nect the system WR signal to the omitted. 6Kbytes of memory is 270k on tv p.c.b. 220n memory and HD6845S. The needed though to work with the VI 2N2369A v.d.u. memory and the 6845 are higher resolution graph plotting always selected so they would be mode provided in Basic which incorrectly written to if WR reprograms the 6845 to scan HSYN C - - wasn't gated. It also enables the twice as much memory and pro- /-lk I vdu. data -bus buffer and clocks a set/ duce a display of 64 rows of 96 VSYNC From end of ik reset latch made from half of an characters. In graph plotting with To pad on tv p.c.ti R72 in tv from which R72 was lifted tv 74LS00. When set, this latch the character v.d.u., the split- clears the 74LS273, forcing a dis- screen plotting area is 192 by 180. 64 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com SPECIAL FEATURE

modifications. Following details From the circuits in the tv set, Connecting a monitor show how to adapt a Ferguson Fig.2, find where the sync. signal SC84 3845, which is the type used by is separated from the video, the A 30cm-screen monitor is about most of the present Scientific polarity of the sync. signal, the Processor optimum. Synchronizing and Computer group, and give guid- cathode and grid pins of the c.r.t. 4/6MHz Z80 processor. may be to for modifying socket, which of the two is driven Maximum 64K -byte ram. video signals inverted ance other models. 58K -byte ram available using suit your requirements. For the Make sure that the set you choose with video, and the potential on SciDOS. switches controlling the sync. is one with an isolated supply, i.e. the other. In the case of the 3845 signals, 5305 and S308, on provides that there is no electrical connec- these points are the end of R72 Display -going syncs, whereas tion between the mains and inter- nearest the back of the set, nega- Up to 32 lines of 96 characters full negative programmable. Scrolling window switch sections S306 and 5307 nal tv circuits, or use an external tive sync., pins two and one determined by software. select either positive or negative- isolation transformer. The Fer- respectively, the cathode and Graphics mode 0 gives 192 by 96 going video; note that these two guson set has a double -wound zero volts. Modifications pixels, mode 1 gives 192 by 192 switches must not be on at the mains transformer as do many required are to break the sync. resolution. Characters and gra- - phics may be displayed simultane- signal within in same time. The dense display portable tvs nowadays - but path the set, this ously. makes a stringent requirement on check to make sure if you use a set case by unsoldering and lifting the monitor but standard types other than the 38.45. Apart from away the end of R72, and remaking Input/output with of 15MHz or the risk to yourself if you use a the path with one half of a two Up to four single or double -sided 8, bandwidths 5.25, 3.5 or 3in disc drives may.be more should be satisfactory. As a live -chassis set, you stand a good pole change -over switch, the used, either single or double dens - cheaper alternative, a television chance of permanently repro- other input of which is a combina- may be modified. This does not cessing large amounts of expen- tion of the two sync. signals. The 5232 serial i/o data rates range being used as a tv but should something other half of the switch is used to from 1 to 38400baud with separate stop the set sive circuitry transmit/receive clocks. Synchro- does require some simple internal untoward occur. connect a decoupling capacitor to nous serial i/o format is 5 to 8 -bit auto -search and sync. or asynch- ronous 5 to 8 -bit with 1, 1.5 or 2 stop bits. RTS and CTR signals conrol serial data flow. Eight -bit parallel data input is buf- fered by schmitt i.cs. Eight -bit par- allel output drives five t.t.l. loads. The mos i/o lins operate event counters, pulse timers and Z80 interrupts. Four mos timer lines are available for timing and sound gen- eration.

A set of three Eurocard - format plated -through-hole boards for SC84 is available from Combe Martin Electron- ics, King Street, Combe Mar- tin, Devon EX4 OAD. Price is £39 for the set including v.a.t. and inland or overseas post- age. John Hodson - secre- tary of the Scientific Compu- ter User Group - is organiz- n ker : sr:. wi erses, sign s an. ing the SC84 user group. For and, taking the ekompe of the display enabling signal, it an be seen the it must be further information, send an delayed by one and a bit character periods if it is to cane active just os the p xels 12 Broughton for the first character on the line ore clocked out of the shift register. s.a.e. to him at Road, Basford, Newcastle- under-Lyme (new address). A listing of SC84's machine - code operating system - At the other end of the system, the 741585 4 bit corporator produces a signet on MCOS - can be obtained by pin 6 when A13 Ado, A15 and ore low low, high end low respectively, i.e. on sending an s.a.e. to Electron- address on the airless bus is in the range 08004H to 07FFFH and the VDU has Room 'paged' into the 'emery. Mote that a switch is connected to the matching 4s to ics and Wireless World, the corporator so that .t is possible to 'rump' i.e. re -allocate the area in memory L303, Quadrant House, The et which the VDU appears. The sense of these switches is that OM on a switch means Quadrant, Sutton, Surrey 'low' on that line. The address is set up ahead of the MREQ see'. by the Z80 so this signal is able to activate MEMDIS and thus prevent a system memory cycle before it even SM2 SAS. is though to enure that this is a memory cycle and starts. Fhrther decoding necessary 65 this is done by gate .n MREQ so that the VDU s.gnal SEL only low during a true SE does several It the 3 e5 multiplexers o

intccess. WR7 signal that they feed bus address lines o thee VW mmaorymid angs. system to the memory and 468455 (This last point is necessary as the VDU memory and 6845 are www.americanradiohistory.com SPECIAL FEATURE

Keyboard and parallel Table 1. Nominal allocations of Z80 i/o ports. i/o interfacing Port address (hex.) Allocaton OE0-3 Keyboard input and control port output 0E4-7 General purpose parallel i/o 0E8 Disc controller command and status port 0E9 Disc controller track register OEA Disc controller sector register OEB Disc controller data register Keyboard requirement is for a mately 20Hz. Overall speed of the OEC-F Not used OFO STI indirect register source of seven -bit ascii code repeat system may be adjusted by OF1 STI parallel i/o port with a positive -going level strobe, changing the 1 pF capacitor value, OF2 STI interrupt pending register B i.e. one which stays high as long the 0.5s hold -off only may be OF3 STI interrupt pending register A as a particular key is pressed (cir- adjusted by altering the 390kS2 OF4 STI interrupt inservice register B OF5 STI interrupt inservice register A cuit shown last month). As ascii resistor and the repeat frequency OF6 STI interrupt mask register B is a seven -bit code, the eighth by altering the 1.8k52 resistor. In OF7 STI interrupt mask register A input bit is not wasted but used as all cases, reducing the value OF8 STI pointer/vector register a flag that the RS232C port is to increases the speed of operation. OF9 STI timers A and B control register OFA STI timer B data register v. d. u . output when The i.c. used for keyboard echo program OFB STI timer A data register using MCOS. Not all keyboards repeat, IC209, also supplies the OFC STI usart control register have an auto -repeat function so it 2.4576MHz signal for bit rate OFD STI receiver status register is provided on the board; an inter- generation. I recommend that OFE STI transmitter status register usart data register is at the you avoid a National Semiconduc- OFF STI rupt pulse sent to the STI 000 STI sync. character register start of the strobe pulse and after tor part for this i.c., CD4093BE 001 STI timer D data register a pause of approximately 0.5s (RCA) or MC14093BCP (Motor- 002 STI timer C data register further pulses occur at approxi- ola) being suitable. 003 STI active edge register 004 STI interrupt enable register B 005 STI interrupt enable register A 006 STI data direction register Table 2. Interrupt vectors in memory. 007 STI timers C and D control register

Address Service routine Wire links from ground pin port which is automatically TP201 to TP202-4 select addresses cleared on RESET, or use a OFFOO I/O line 0 (keyboard interrupt) of the i/o ports. The i/o allocation 74LS373 and make link 201 for a OFF02 I/O line 1 used in the system software is tri -state port enabled by applying OFF04 I/O line 2 OFF06 I/O line 3 (pulse width/event B) given in Table 1. Links need only a low level to pin one of the port OFF08 Timer D be included should these be connector. The latter option OFFOA Timer C changed for experimental pur- means that this port may then be OFFOC I/O line 4 (pulse width/event A) poses. If this is not envisaged, connected in parallel with the OFFOE I/O line 5 OFF10 Timer B they may be left out altogether. eight -bit input port to form a bidi- OFF12 Transmit error rectional i/o port. Spare I lines on OFF14 Transmit buffer empty Parallel i/o is catered for by the STI, pins 11 to 13, are also OFF16 Receive error eight -bit input and available from pads adjacent to OFF18 Receive buffer full uncommitted OFF1A Timer A eight -bit output ports, a control the i.c. pins as are the outputs OFF1C I/O line 6 (disc controller INTRO) port used for keyboard input, and from the four frequency genera- OFF1E I/O line 7 (disc controller DRQ) output to the disc drives and sys- tors. Link 203 should be wired in tem. There is an option for the on the basic system but may be These are addresses of the two consecutive locations in memory at which the eight -bit parallel output port, removed to free pin 16 of the STI interrupt controller will expect to find the starting address of the service routine IC206. Use a 74LS273 and make for use in an interrupt daisy - for that particular interrupt. link 202 for a standard eight -bit chain, Table 2.

the driven pin, the cathode in this mounted directly on the back of of set considered. and £21 respectively for non- case, to suppress the tv video sig- the tube socket. This is the Normal settings for 5301.4 are commercial users and further nal in computer monitor mode. In recommended position as long off -off -on -on, mapping the v. d. u. discounts are available for the 3845, a resistor is also con- wires will ruin the video quality. at hexadecimal addresses 0800- those buying more than one nected to this switch and to the When making this interface, 09FFF, switched in by VDUSEL software package at once. remove the tube socket from the being permutations John Adams is considering junction of R127, the height con- high. Other producing a kit of i.cs for SC84. trol, and R128 which, looking at tube while soldering and use stiff are possible for experimentation. For details of these items send the back of the set, is the leftmost wire to mount the interface board an s.a.e. to him at 5 The Close, terminal of the height control. onto the socket and flexible wire Radlett, Herts. This allows automatic adjust- (including the screened wire) to ment of picture height to the opti- link from it to the switch, etc., in mum for tv and computer. order not to put strain on the SC84's disc -operating system, The video signal is brought in socket and c.r.t. neck. Most port- SciDOS, with utility software on a short length of screened able sets have the 3845 type of costs £36 extended Basic with cable and buffered by a 2N2369A circuit where the cathode is graphics is £22.50 and Basic before being applied to driven and the grid is at zero with enhanced file manipula- transistor tion, i/o control, numeric/con- the tube grid. All connections are volts. If neither the grid nor stant string handling and 12 - A switch -regulated power sup- made through the tube socket, cathode is at a low potential then digit precision is £31.50. ply and further constructor's the prototypes being about lin some form of level -shifting must These prices include v.a.t. and notes are subjects of a future square pieces of Veroboard be used or, better, a different type postage and become £24, £15 article. 66 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com CASSETTE RECORDER

Continued from page 62 the p.s.d. the output voltage 100mV r.m.s. ideal. not tried them out on my own changes to drive the v.c.o. to the The expected direct voltage computer, preferring to use t.t.l. new frequency. variation on the output of pin 7 for levels. It is my understanding Operation of the phase -locked an input signal with frequency that RS232 type inputs and out- loop is exactly analogous to a deviation of ±10% is, as men- puts normally invert the t.t.l. servo -loop; it has a natural fre- tioned earlier, about 430mV. logic levels. In so far as I have quency, damping factor and a This can be adjusted to ±215mV shown the RS232 type inputs and bandwidth with a second order, about the reference voltage level outputs being used, this should low-pass filter characteristic. on pin 6 by adjusting the value of not matter since, if the modulator Effectively what the p.1.1. does is the 5k52 variable resistor. This is is connected to the demodulator to recover, from the frequency of most easily achieved by connect- then a 'high' input on the modula- the input signals, the original ing the output of the modulator to tor will produce a 'high' output changes in voltage that drove the the input of the demodulator and from the demodulator. However, v.c.o. in the modulator. As the applying logic low and high levels in the absence of an audio signal v.c.o. of the p.1.1. is identical to to the modulator input. input to the demodulator the t.t.1. that of the 566, it is not surprising The output from the demodu- output should be high. If the that the changes in voltage levels lator, pin 7, which is applied (in- RS232 -type connection is used at the output of pin 7 are similar to ternally) to the input of the v.c.o. on the output of the demodulator, those applied to the input of the needs to be filtered for the p.l.l. to this will also be high. A subse- v.c.o. of Fig.6. The voltage operate satisfactorily. This is quent RS232 input on the micro- change applied to the v.c.o. of the achieved in this circuit by the computer may invert this to a modulator was 430mV (13.33- 27nF capacitor connected logic low on its t.t.l-type output. 12.9); the voltage output from the between pin 7 and the +15V sup- To invert this logic, the 1MS2 565 (pin 7) is thus of the same ply rail. For the chosen v.c.o. resistor connected between the order. operating frequency of 10kHz and negative input of the op -amp vol- The maximum operating a rate of 2400 baud this value has comparator and the -15 volt sup- tage of the 565 i.c. is 26 volts. It been found to be satisfactory. It is ply rail should be connected to the cannot therefore operate from the also satisfactory for lower rates, +15 volt supply rail instead. A con- ±15 volt supply rails and was but possibly not for a higher rate final article will describe the up/ to from sequently chosen operate of 4800 baud. (Unfortunately I down tape counter and record/ rail and the +15 volt supply have not been able to try this out.) playback electronics. ground. (±15 volt supply rails To provide a and RS232 were chosen because of the large t.t.l. type output level, the output from voltage drive required by the tri- the demodulator, on pin 7, needs _LTTERATURE RECEIVED _ angle -to -sine wave converter of to be amplified. This is achieved Fig.6; it will not operate satisfac- A neat modern design is carried The functions of many different using an op -amp, as a comparator through the S Range of meters and instruments are combined into one torily from ± 12 volt supplies. ) and the output from pin 6 as the instruments from Philip Harris. They unit in the Griffin programmable The two inputs of the 565 i.c. pins level. The output from are designed with particular attention scientific instrument, or GiPSI. 2&3, require an identical d.c. reference pin 7 is further filtered by the sim- to reliability, ease of servicing and Starting from a single or dual -input bias that is slightly less than the ple two -stage ladder filter com- user safety and feature ease of multimeter it may be converted into a half-supply voltage. The poten- storage and are clearly marked for by the posed of 5.6k52 resistors and variety of other instruments tial divider consisting of the identification. The range includes a of modules and 4.7nF capacitors. The band -edge addition plug-in 4.7k52 resistor and 3.3k52 resis- dual -trace oscilloscope adaptor, overlays to show the functions of the of the ladder filter is chosen to be tors produces the required d.c. various power supply and amplifiers, touch -sensitive membrane keyboard. approximately half way between bias on pins 2 & 3 via 3.3k52 meters for joules, conductivity, pH, Among the modules are a pH meter, the maximum keying rate (2400 series resistors. The audio input counters, timers and an electrical measurements of pressure, magnetic baud or 1200Hz) and twice the safety tester. Philip Harris Ltd, flux, timing and counting, and many may be to either of these two input frequency (about 20kHz). Lynne Lane, Shenstone, Staffs WS14 more. The meter can also be inputs, via a suitable decoupling OEE. WW270 interfaced with a computer as part of capacitor. As the lowest audio The 1nF capacitor connected a data acquisition system. Full details A CNC lathe which can be controlled signal frequency is not less than between pins 7 & 8 acts in the in a brochure from Griffin & George, from a BBC micro is produced by 9kHz, the decoupling capacitor same way as that between pins 6 285 Ealing Road, Wembley, Colne Robotics and described in a & 5 of the 566 i.c.; i.e. to Middlesex HAO 1HJ. WW273 may have a conveniently low leaflet. Included is the basic software value of 22nF. improve high -frequency stability. which provides a comprehensive Similarly, the 1nF capacitor The components that deter- range of control codes to program and A number of programs for biological mine the free -running frequency across the inputs of the op -amp retain complex cutting sequences. experiments are included in Micros in of the v. c. o. of the 565 i.c. (which comparator does the same thing. Safety measures are provided by the Lab. Designed for use with the ZX should be the centre frequency of The 1M52 resistor connected hardware safety cut-out switches and Spectrum computer, full software and 10kHz) are the resistor on pin 8 (a from the inverting input of the op - from within the software. Colne hardware details are given in this 6.8k52 resistor in series with a amp to the -15 volt rail ensures Robotics Co. Ltd, Beaufort Road, off duplicated booklet. The centre that Richmond Road, Twickenham, 5k52 and the capacitor that a logic high level is output publishes it can also supply a number variable) Middlesex, TW1 2PQ. WW271 on pin 9. The values chosen are from the op -amp when no audio of components to ILEA schools. ILEA South London Science Centre, for the v.c.o. of signal is present on the input to the same as those A range of small p. c. bs, each with Wilson Road, London SE5 8PD. Fig.6, except that the resistor is the demodulator. Two outputs elements of a circuit can be linked Telephone: 01-7012224. made adjustable. For a ± 10% fre- are provided from the op -amp, together to make up more complex quency deviation, the amplitude one at t.t.l. levels suitable for circuits. This is the Alpha system of the audio input signal can vary coupling directly to t.t.l. i.c. from Unilab. It is designed to be a ILEA publish two magazines for 'low-cost, radical approach to the school micro from 10mV to 1V r.m.s., and still inputs, and one at an RS232 type users -Computers in effective teaching and learning of Primary Schools newsletter for of level. maintain good tracking the basic electronics, initially for the 13+ primary schools and Educational I must confess, at this point, input frequency. The volume age range.' There is also a range for Computing for secondary setting of the record/playback that although I have shown the more advanced work. Details schools. Both come from the Inner electronics on playback of the modulator and demodulator cir- supplied in a leaflet from Unilab, London Educational Computer recorded signal is thus non -criti- cuits of Fig .6 and 8 with RS232 Clarendon Road, Blackburn, Lancs Centre, John Ruskin Street, London cal and a mid -way setting of type inputs and outputs, I have BB1 9TA. WW272 SE5 OPQ. WW275 ELECTRONICS & WIRELESS WORLD JULY 1984 67

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These memories can also GM833 RAM-DISK 512K £450.00 ICI Copyright Cubegete Ltd - all rights reserved. to retailers end distributors be used in conjunction with the IUK C/P & expert extra at cost) All above available - priority channel mode. ALSO IN STOCK- MOTHER BOARDS. FRAMES. contact Computer Oept. for details. For those intrepid explorers CABLES. POWER SUPPLIES. KEYBOARDS, SOFTWARE etc. POWER SUPPLY the Atlantic COMPUTER who venture across FULL LEAFLETS/DETAILS OF SUITABLE this Switched mode. Stabilised. Self protecting. you will be pleased to hear PERMUTATIONS - SEND LARGE SAE S/C protected. etc. 220/240V AC. *5V 3.3A, 12V handheld also copes with all 0.5A. 0.5A. Suitable We can advise also with terminals and complete 2.4A 40% cycle. -5V -I2V the US channels including the Galaxy computers with monitors and Disks reedy Apple replacement £50.00 weather channels! to use. IUK C/P C1-501 COMPUTER FANS NASCOM -2 CU7983 115V 50/60Hz Available in both kit and built form. Featuring NOW AVAILABLE AT £245+ VAT (inc. nicads and wall charger) 12/13W Impedance protected Microsoft Basic. NAS-SYS monitor, full QWERTY (6 channel handheld) (use 21e series for 2300) DON'T FORGET THE SMC104M keyboard of the highest quality. 4MHz Z8OA x I IS STILL AVAILABLE AT £160= VAT (inc. nicads and charger) processor. full RS232 I/O and parallel I/O. One of 43/4" Two for £8.70 C/P 70o1 the most flexible computer cards around, IUK 220/2408 'as new' only £4.78 ( U K UP 50p) each SOUTH MIDLANDS COMMUNICATIONS LTO1 expansion cababilities are Impressive using the NASBUS and compatible BO-BUS expansion OSBORNE ROAD. TOTTON. SOUTHAMPTON cards. Expansion includes hi -res colour graphics THERMAL Tel: (0703)86733371x: 477351 SMCOMM G lull CP/M disk system and much mom. Send SAE WWII leaflets. NASCOM 2 kit £225.00 Ith NASCOM 2built £265.87 CIRCLE 56 FOR FURTHER DETAILS. ITT 2020 CABINET Professional computer case COMPLETE WITH FULL A x t5g" x 4'{2" (Front slopes) ] 18" HANDBOOK.3 ROLLS PAPER £43a Yaz As previously advertised £23.91 IUK C/P £2.101 MITSUBISHI IUK c/P CI OUI TOROIDAL TRANSFORMER SUITABLE FOR: TANDY BBC ORIC NASCOM GEMINI ACORN NEW BRAIN DRAGON ETC. 100 isolations MG F-1400 watts ETC. (Interface unit with leads£13 - state model) GaAs FETs 230/2408 AC plut 8 -O -8V 4A (your enquiries invited) MG F-1402 15-0-15V 0.645A 30V 0.16A size approx 41// dia x 13/4" KEY PAD FROM STOCK £6.81 (UK C/P 75p) CHERRY MG F-1412 16 button key pad non encoded PRESTEL KIT £5.17 IUK C/P 30p1 Complete set of PRESTEL adaptor cards. Con- CARDS/ Aspen Electronics Limited sisting of main processor card with battery MODEM backed RAM. modem card. direct line coupler and COUPLER UK representative for Mitsubishi Electric keypad. Outputs are composite monochrome and Brand new. tested. answer and originate 300 separate RGB. Suitable for use with colour BAUD uncased acoustic modem card by famous monitors or suitable TVs. IPS */-12V and *5V1 manulacturer. RS232 input/output. Power supply 2/3 Kildare Close, Eastcote, Ruislip £80.83 */- 12V at 180mA. Requires 2 magnetic earpieces. 2 switches. 2 LEDs and connectors to Middlesex HA4 9UR ASCII complete. Circuits and connection data supplied. 01-868 1188 Tlx: 8812727 Card only £26.04 Tel: KEYBOARDS Card and remainder of small components £29.09 keyboards. Computer Telephone Direct Une coupler type LTU 11 MKII. All models brand new Suitable for direct coupling PRESTEL adaptors QWERTY IUK C/P £1.001 and the above acoustic modems. Integral Line All and -I2V 1 Amp P/S £7.78 CIRCLE 28 FOR FURTHER DETAILS. models *5V select and autodial relays requiring TTL inputs. Circuits and connection data supplied. 69SD5 Exclusive Special Purchase. Compact LTU 11 Coupler £13.00 64 key (hall effect( *5 function keys -ve/*ve 1200 BAUD receive 75 BAUD send direct coupled strobe. Normal ASCII but all definable. Steel frame. modem for PRESTEL. Requires *5V supply with All facilities complete with plugs £26.04 TTL Inputs for data. line select and autodial. SMK 60 Key general purpose. steel plate. LTU 11 direct coupler required. See above. IN VIEW OF THE EXTREMELY RAPID CHANGE TAKING Redelinable output. Neg strobe pulse. 4 user Connection data supplied. definable keys. shift and control keys etc. PRESTEL modem card £ 13.00 With connector £37.35 PLACE IN THE ELECTRONICS INDUSTRY, LARGE QUANTI- Discounts for quantities - please enquire STOCKISTS FOR Printers: Paper. Thermal. Daisy- Computer/talc.. etc. keyboard bargains for callers wheel Disk Drives Boxed. Chassis also Winchester TIES OF COMPONENTS BECOME REDUNDANT. WE ARE Monitors: Green. Orange.White. Colour Micro's BBC. ALWAYS KEYBOARD BARGAINS Electron. Nascom. Galaxy. Plus others. Cables. MS FOR CALLERS plugs. blank disks & tapes. software. books. etc. CASH PURCHASERS OF SUCH MATERIALS AND WOULD Official orders welcome. to confirmation APPRECIATE A TELEPHONE CALL OR A LIST IF AVAILABLE. (Subject Please add 15% VAT WE PAY TOP PRICES AND COLLECT. (UK only) HEflRYS Export orders allow SHOP adequate CIF COMPUTER Details available R. Henson Ltd. 404-406 Edgware Road. London W2 most models send SAE 01.402 6822 21 Lodge Lane, N. Finchley, London, N.12. 5 minn. from Tally Ho corner ORDER BY POST OR PHONE Telephone 445 2713/0749

('IRCd,E 29 FOR FURTHER DETAILS. ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com HEflRYS AUDIO ELECTROflI(STE ON TEST EQUIPMENT COMPONENTS COMMUNICATIONS COMPUTERS {ALL MODELS Ä WEEK DISPLAY ,, FREQUENCY COUNTERS SIGNAL GENERATORS OSCILLOSCOPES O Full specification any model ea Send SAE UK C/P- & ins Single trace trace All models BNC sockets 220/2409 AC IUK C/P & Ins £1.001 Oual carrier Bench portables IUK C/ £1.811 Bench portable all slne/square/trlangle/TTL/etc. £2.60 carrier £3.50 DIGITAL TNT £5.20 TNT £7.00 IPFM200A pocket counte IC/P650 External sweep mode. FUNCTION Securicor £10.45 Securicor £13.00 MULTIMETERS METEOR SERIES £1.00. mandar T6101* 0-.02HZ to 208KHZ various IUK C/P 8 ins Bench type UK made. 0.1 HZ resolutio .8 digit. LED display. HAMEG 2years warranty Hand held 65p) facilities £105.00 mains operated 220/2408 AC. swilchable gate times. Single trace. IOMHZ. ooK---;49 Thandar T6102* 0.2HZ to 2MHZ various HM103 MET1000 2 range 5HZ t 100MHZ II 20MHZ " PROFESSIONAL STRIES facilities £155,00 2mV. 6 x 7cm display plus Portables typical) £89.00 Thandar Bench Jupiter 5000.1 Hz - 500 KHZ £110.00 component tester £158.00 TM355* 31/2 digit LED 29 ranges 10A AC/OC MET600 3 range 5HZ TO 600M HZ 1700M HZ Dual trace 20MHZ 2mV. Thandar Pulse Bench portable HM203 20 Meg ohm - 0.25% basic £85.00 typical) £115.00 Algebraic add. 'Z' Mod. plus T6105* 5HZ to 5M HZ Various facilities £105.00 TM356* 31h digit LCD 27 ranges 10A AC/DC MET1000 3 range 5HZ to I GHZ )1.2GHZ tester )Optional * Optional carry case £5.95 component carry 20 Meg ohm - 0.25% basic £95.00 typical) £159.00 case £21.501 £264.00 AUDIO TM351 * 41/2 digit LCD 29 ranges 10A AC/OC (Optional 6 x nicads £9.951 HM204 Dual trace 20MHZ. Leader LA6275 bind sloe/square 0/P 0/59 RMS 20 Meg ohm - 0.1% basic £ 115.00 SABTRONICS sweep delay. 2mV. plus Dlat 005e!,10HZ to I MHZ (*Optional carry case £5.951 New models. LED display. switchable gate times. £93210 component lester 'optional carry Leader LA8120A 5 band 10HZ to (MHZ to 03V Thurlby Bench Portables 8110A 8 digit 20HZ to 100MFZ £79.00 case £21.501 £365.00 RMS Into 600 ohm 0.05%diet :Ina/quire £145.00 l * Opllonal carry case £ 18.001 861OB9digit 10HZto600MHZ £109.00 HM605 Dual trace 60MHZ. LCD Leader LA6125 5 bind 10HZ to I MHZ to 0311 1503* 43 digit 0.05% basic IOuA resolution 80006 9 digit 10HZ to I GHZ £149.00 delay line. I mV, 1MHZ CALGEN ANS Into 800 ohm sine/square/burst plus frequency measurement up to 4MHZ AC/DC 85009 9 digit up to 11/20HZ £239.00 optional carry case £21.501 10 Amps £159.00 THANDAR 0.03% diet £330.00 £487.00 TRIO A6202A 4 bind 20HZ to I OV RMS 1503H5* 43/, digit LCD as above but 0.03°'. UK made LCO displays with batteries. 200KHL O/P HITACHI basic £175.00 0.5°/. diel CR OSC 0/109 pp 0/P £99.00 TF040 8 digit 10HZ to 40MHZ LCD, I HZ resolution All models 5mV IImV using x5 TRIO A6203 5 bind 10HZ to 0.1% diet 1054* 43/, digit LCD True RMS version £185.00 40mV sensitivity. 2 gate times with batteries £120.00 Mill magnifier) 51/2 IuA 0/711 RMS 0/P £139.00 1905e digit Intelligent mulllmeter TF200 8digit 200MHZ LCD. granges resolution Ippm. All models complete with RF resolution D015%basic £325.00 IOmV RHS sensitivity. 5 gate tomes with batteries 2 probes. PORTABLES TRIO 68402 8 range 100KHZ to 30MHZ RF 0.1V RMS METRIX HAND/BENCH (ITT) £ 165.00 2 years warranty. 188 x 88 s 50mm Rotary controls) Im/tot mod £72.00 'Size Optional carry case £5.95. AC mains adaptor £6.95. V212 Dual 20MHZ. bench MX52231 digit LCD 21 ranges 10A AC/DC Leader L8917 6 band 100KHZ to 1500142196H PFm200A Pocket 8 digit 20HZ to 200MHZ. 2 band portable 6' CRT CHI 0/P 2 Meg ohm Basic 0.5% 450MHZ on Harmonics) RF 0.111 RM8, IM/tot Mad. £67.00 LEO display with battery 0.1Hí resolution. I OmV £335.00 digit LCD 29 ranges IDA AC/DC AF I KHZ 1 volt 1 MHZ Oal optional £380) £96.00 MX56231 sensitivity with battery £69.50 V222 Dual 20MHZ. portable 20 Meg ohm Basic 0.2% Plus continuity tester £95.00 PRESCALERS with DC offset and alternate MX563 True RMS 31/2 digit, 30 ranges 10A AC/DC. Suitable for most types al counters to extend range. DIGITAL CAPACITANCE magnifier £375.00 20 Meg ohm. 20HZ to 30KHZ 0.1% basic £155.00 )Thandar) BNC sockets. METERS 0203F Dual trace 20 MHZ lab MX575 41/2 digit unie RMS. 21 ranges 10A AC/ DC. HZ.10mV RMS. TP600 40MHZ to 600M direct port. with sweep delay.51/2" CRT up to 50KHZ. 0.05% basic £175.00 powered by counter £45.00 £375.00 HAND HELD MODELS TPI000 100 to 1000MHZ complete with AC V422 Dual 40MHZ. portable adaptor P/S. 25m8 RMS sensitivity Controls: S = Slide R = Rotary PB = Push button £65.00 with OC offset and alternate probe kits - for all models AO feature AC/DC volts. DC amps )many with AC amps) Optional suitable amplifier £580.00 X1 £6.90 X10 £8.26 ohms etc. (UK C/P 65p) 0353F 35 MHZ dual trace lab port. with sweep ALL MODELS WITH CARRY CASE Direct reading LED meters delay. 51/2" CRT. £580.00 ISI K025C 12 range 0.2A OC 2 Meg ohm £24.43 VARIABLE POWER SUPPLIES DM6013 Pocket/bench 8 range 0.1pí to 2000mId 0650F Dual 60MHZ lab portable with dual lime base K0305 14 range 10A DC 2 Meg ohm IS) £24.30 3° digit 0.5% with battery ¡UK C/P 65p) £52.13 £850.00 KD30C 26 range IA AC/DC 20 Meg ohm IR) £29.13 CM200 Bench model 4l¢ digit 0.2% let to Also in stock VI34 storage.VC6015 digital storage scopes. METEX 300030 range 10A AC/OC 20 Meg ohm 2500mfd 6 ranges 'UK C/P 85p)£89.00 Battery/Mains Scopes. Vector 8 TV monitor available IR( £33.00 a 6010 28 range IDA AC/DC 20 Meg ohm ¡POI £33.00 DIGITAL THERMOMETERS CROTECH KD55C 28 range IDA AC/DC 20 Meg ohm (311 £34.74 a^jr. a 3030 Single (race 15MHZ. SmV. Pocket size LCO thermometers complete with KD615 18 range IDA DC 2 Meg ohm plus We 220/2408 AC inpul 95mm CRT plus component battery Accept any type K probe IUK C/P 65p) tester [Hi £34.74 PP241 single meter. A/V switch. 0/308 I amp £30.43 tester TH301 LCD -50-'0 to 750'C. I C resolution £1.00 7030 As 6010 but 0.1°, basic IPB) £41.30 PP243 3 amp version £52.13 3132 Dual 20MHZ. 2mV. 5" with thermocouple £59.50 CRT DM3350 Autorange plus cont. tester 18 range 230N Twin meter 0/3081 A £91.00 Algebraic /-.'t mod. plus TH302 LCD -40 C to 1100' C Cent/Fahrenheit IDA AC/OC 2 Meg ohm IR) £43.44 330N 3 amp version £164.00 component comparator and OC 0.1' and 1 resolution with thermocouple £79.50 DM2350 Minl autorange plus cont. tester 19 range IUK C/P above models £1.00) source outputs £283.00 Range of various probes in stock£17.50 to £25.00 10A AC/OC 120A Max) 2 Meg ohm 1PB) £54.73 PL Laboratory series LED readout ' (IMO versions 3035 Single Ince 10 MHZ amp. 3100 Pen type auto ranging AC/DC Y 20 Meg ohm series/parallel etc. tester. 5" CRT £189.00 buzzer.. £39.00 P1310309IA £118.00 PL31013140 £249.00 COMPONENTS ACCESSORIES TRIO 2 years warranty PL320 30V 2A £145.00 P11.320 MO £315.00 TOOLS Single trace 10 MHZ LOGIC PROBES IUK C/P above models £2.501 Large range In stock semiconductors, relays. tools. GOS3310 5mV. 75mm display. Plus millions of capacitors. resistors. presets. controls. Mains port. £139.00 TTL. OTL etc. plugs/sockets etc. etc. For bulk export users. LPIOIOMHZ £19.96 ANALOGUE MULTIMETERS CS1562A Dual trace 10MHZ. Tel: 01-723 1008 with enquiries. OLP5050MHZ £43.44 range 130mm CAT, 10mV. 1 microsec. General I*mirrcrscale) with 2 probes £260.83 IUK C/P either model 65p1 (UK C/P 65p1 OTHER EQUIPMENT IN STOCK CS 1566A Dual 20M HZ. 140mm HC6015 15 range pocket 10Kí Voll Send SAE for full specifications CRT. 5m V, 0.5 micros«. with ANALOGUE I meg ohm £7.39 ---W (*UK C/P £1.50 UK C/P £1.00) 2 probes £326.00 M200 30 range 20K/Volt 20K11Z MULTIMETERS LH C909 video head each Special purchase £8.65 list price £19.00) VHS/BETA tester £45.00 THANDAR 9e, Metrix (ITT) 0M358 Scope multiplexer. 35MHZ, expands any 2 years warranty HM102BZ* 22 range 20K/ Volt 10A DC plus cont. scope to eight channels £169.00 SC11011 IOMHZ battery bench portable. 10mi 32 x Professional range Buzzer, 10 Meg ohm £11.74 LTC905* Scope add.on semicon curve 28mm display IUK C/P 65p1 Size 110 x 45 x 185mm TMK500* 23 range bench. 30K/Volt 12A DC Plus tracer £99.00 Size 255 x 150 x MX 130 25 ranges 5000 ohms per volt cont. buzzer. 20 Meg ohm £20.83 LCT906A Transistor tester pli types) £ 109.00 50mm £165.00 7OCA0.1to10005ACV10Vto1000.UDCAmps NH56R* 22 range 10K/Volt 6 Meg ohm £10.39 LTC907 Transistor tester, signal Infector case AC 830A* 26 range 30K/ Volt IOAC/OC: 'Optional carry £5.95. I00uAto33A.5AC Amps 3uA to30A2ohms traer £178.00 Rach Nlcad £11.00 10 Meg ohm £20.83 adaptor/charge £6.95) 1 K to l0K £65.00 LYT72= FET/YOM/transistor lester £143.00 360TR* 23 range bench. 1000/Volt, large scale, MX230 29 ranges 20K/Volt 100mV to 113031.1 OC. 3V LCR740* LCR bridge:cap. Inductance and 10A tester. 10 Meg to I000V AC 50uA to 10A DC. 3uA to 10A AC AC/DC plus life ohm £34.74 resistance £195.00 EDUCATIONAL; olscouAlrs AT2100* 31 range de luxe 100K/Volt 1K to 10 Meg ohm £59.00 LDM170* Distortion meter 20 HZ to 20KHZ £310.00 MIXED QUANTITY 10A AC/DC; 100 Meg ohm £29.13 MX430 32 ranges 40K/Volt DC 4K/V AC 1F61300* Sweep 0.3% function generator AT1020* 18 range de luxe 201(/Volt plus Hie 10m1/ to 15008 DC. 5V to 15008 AC 25uA to 15A DC. 0 002HZ to 2MHZ £395.00 & EXPORT DISCOUNTS tester. 5 Meg ohm £18.26 l'-,uA to 15A AC 50 ohm and 500 ohm (linear sale) TC40* VHF/UHF FM and TV field strength meter We would be pleased to quote. Contact sales odice at 406. YN360TR* 19 range 20K/Veit plus Hfe tester 2000K ohm and 20 Meg ohm £89.00 Battery operated with carry case £177.00 1 Meg ohm £12.13 11117321 UK PAL TV colour pattern generator TRANSISTOR TESTER KRT5001 * Range doubler 35 range total HIGH VOLTAGE METERS £222.60 Direct reading PNP/NPN and diodes. 50K/Volt 10A DC 20 Meg ohm £17.35 MC328 As above but PAL 8-69 £222.80 We. leakage etc. General purpose ICI Olrect meter reading ST303TR * 22 range 20K/Volt plus Me tester meter C/P 65p) LKH P3OA O/30KV0/ 1391801- 700KHZ to 250MHZ Dlp inductive/ £23.43 IUK £34.74 12A OC 1 Meg ohm £15.61 KHP30M0/300/45KV £34.74 cap res. 'rep measurement etc. £62.00 I00mV 12mA) mount (UK C/P either model £1.00) CHART RECORDER Panel PROBE KITS ELECTRONIC 240V AC £ 149.00 In wallets with adaptors etc. BNC fitting; AC CLAMPMETER INSULATION TESTER LFM39 A-0* Wow and flutter meter. Jis. CCIR. for scopes/counters/generators etc. " Din. £445.00 01 £6.90 XI/X10Swltchabie £10.00 0/300A. 0/6008 AC ohm 0/1K 5000/0.100 Meg ohm with carry casa. 14Z15- Scope add on component tester £24.00 XIO £8.26 Demodulator £16.00 Total 9 rangea with carry case and leads etc. LTC91 OA* CRT tester/re)uvenator for b/w X100 £16.00 leads ST300 £26.04 C/P 65p) (UK 71,501 £59.13 (UK C/P 6p) and colour £175.00 IUK C/P tree with other Item or 6p per Ito 3 kits) RETAIL MAIL ORDER Official orders welcome. Please add I5°o VAT (UK only) EXPORT. INDUSTRIAL EDUCATIONAL (Subject le confirmation) Export allow adequate CIF PRICES EXCLUDE VAT

ORDER BY PHONE OR BY POST OR CATALOGUES Shop I'IEI IR T'S 404-406 Edgware Road. London, W2 CALL IN ANO SEE FOR YOURSELF Send large Computers 01-402 6822 Equipment 01-724 0323 Components 01-7231008 SAE )20p UK) visa Specification sheets Sur« al, Anal Any model Shop AUDIO ELECTRO(1IC8 301 Edgware Road, London, W2 Order by Pott Mte CHEQUES/ACCESS/ (State which) VISA or you an 1N.pbono your order.. Test Equipment, Audio. 01-724 3564 Send SAE Communications Up to £1000 instant credit Schools. colleges. companies All mail to Cubegate Ltd,1st Floor, 406 Edgware Road, London W2 1 ED Available through Lombard Tricity Finance Export iree on written request

CIRCLE 4 FOR FURTHER DETAILS. ELECTRONICS & WIRELESS WORLD JULY 1984 69

www.americanradiohistory.com This little RSGB devil can BOORS talk ba , !

AMATEUR RADIO CALL BOOK 1984 edition

Published annually, this comprehensive directory of amateur radio stations in the UK & Republic of Ireland, incorp- orates over 18,000 new callsigns This must be the smallest, 2M, FM mobile available measuring H x 144mm W and over 10,000 amendments. All today, only 38mm x 177mm D. It has all the features that you probably require notified by the Department of Trade included in this microprocessor controlled unit. In addition, if you feel lonely and Industry between August 1982 and can't find anybody on the band, just press "speech" and the optional built in and February 1984. It also includes speech synthesizer will tell you the frequency you are tuned to. This is a boon to the bli-rd lists of RSGB affiliated societies, operator or to those that tuck their rigs out of sight. groups and special callsigns. Brief features:- 25/1 Watt output, green LED readout, For most entries, the address scanning (memories and programmable limit band scan), published is the station location. This gives the priority scan, programmable duplex splits, 25 and 5 Khz ICOM VHF/UHF enthusiast an easy reference for beam directing purposes. tuning steps, 10 memory channels with lithium back up cell, This new edition is available now from the RSGB sales counter price £5.89, normal and reverse repeater switch, dual VFO, internal the World System or by post price £7.14. speaker and optional speech synthesizer. Just ask for a leaflet and we'll be glad to send you one. THE MICROWAVE NEWSLETTER TECHNICAL Thanet Electronics Limited COLLECTION 143 Reculver Road, Herne Bay, Kent, England. Tel:(02273) 63859/63850. Telex. 965179. Compiled by J N Gannaway, G3YGF CIRCLE 38 FOR FURTHER DETAILS. S J Davies, G4KNZ

This new book comprises a collection of technical material published in the Microwave Newsletter from April 1980 to May 1983. The material is WirelessELECTRONwICS & copied directly from typewritten originals and is compiled in sections covering: 1.3GHz, 2.3GHz, 3.4GHz, 5.7GHz, 10GHz (general) (wideband) or (narrowband), 24GHz, Millimetric Bands, Oscillator Sources, Filter Design, Antennas, Calculating Bearings, Radiation Hazards, Test Equipment. Size M. 140 pages. Price £6.00 from RSGB sales counter or £6.83 including P&P. EDITORIAL FEATURES

OTHER RSGB PUBLICATIONS A Guide to Amateur Radio (19th edn) £3.44 1984 Amateur Radio Awards (2ndedn) £3.41 Amateur Radio Operating Manual (2ndedn) £5.22 HF Antennas for All Locations £6.91 ISSUE PUBLICATION Radio Amateurs Examination Manual (10th edn) £3.42 DATE DATE FEATURE Radio Communication Handbook (paperback) £ 10.91 Teleprinter Handbook (2nd edn) £13.84 Sep. 1984 Aug. 15th Digital Multi- Television Interference Manual (2nd edn) £2.13 meters VHF/UHF Manual (4thedn) £10.31 Dec. 1984 Nov. 21 st Components The RSGB is the national society representing all UK radio amateurs. Buyers Guide Membership is open to all interested in the hobby, including listeners. The Jan. 1985 Dec. 19th Society publishes a range of books, log books and maps for the radio ama- Single Board teur. A large selection of other radio and electronics books are also Computers stocked, a full list is available on request. Contact the membership ser- Mar. 1985 Feb. 16th IEEE vices section for more information about amateur radio, the RSGB and its Instruments publications. All publications sold by the RSGB are available at dis- May. 1985 April. 19th Power Supplies counted prices to members. July. 1985 June. 21st VDU's Sept. 1985 Aug. 16th Communication RSGB Publications Receivers Potters Bar, Cranborne Road, For more details regarding Hertfordshire EN6 3JW advertising Contact Bob Nibbs CIRCLE 39 FOR FURTHER DETAILS. 01-661 3130

70 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com TRANSCEIVER SURVEYS Two -metre transceivers A survey of amateur radio equipment for the popular 144-146MHz band For most newly -licensed radio inferior to those of larger units. tune in steps governed in the first amateurs, the two -metre band is Most hand-helds offer f.m. only, instance by the frequency of the a natural starting point. It is the though there is at present one synthesizer's v.c.o. With f.m. lowest band available to those s.s.b. model. equipment for the European mar- without proficiency in morse The third main transceiver ket, the step size is often 12.5 or code. It is also the most popu- type is the basestation. This is 25kHz. This gives easy tuning of lous: there are no worries about typically quite a large and com- the numbered f.m. channels on fording other stations to talk to. plex unit, normally mains -pow- 2m, which are spaced 25kHz Most equipment now in use on ered but often with a d.c. supply apart. So an f.m.-only set which 2m is factory -built, almost invar- option for use with a car battery. scans in smaller steps may be iably in the Far East; and a wide Most ready -built basestation awkward to handle when rapid choice is available with prices units are multi -mode sets, pro- retuning is called for. However, in starting at a little over £100. But viding all three of the common many synthesized sets the chan- it is still possible for the construc- amateur radio transmission nel spacing can be programmed tor to get on the air with a home - modes: narrow -band f.m., s.s.b. by the user. built rig at a cost of perhaps a few and (for morse code) c.w. Ampli- On s.s.b., tuning steps as tens of pounds*. tude modulation is more or less small as 100Hz are the norm. But The average newcomer's dead on v. h . f . , despite one or two s.s.b. sets also have a clarifier or choice is likely to be a narrow - attempts to revive it: the few receiver incremental tuning con- band f.m. set, for use mainly in stations still using a.m. are trol (r.i.t.), which allows the the channelized region above equipped mostly with second- receive frequency to be offset 145MHz. This type of rig closely hand commercial radiotele- slightly from the transmit fre- resembles the sort of c.b. set phones. quency: this is to help resolve off - from which many new licensees The multi -mode set also channel transmissions. On the have recently graduated: the con- makes a useful building block for more expensive multi -mode sets trols are few and simple, and forays into the higher bands by there may also be a control to pull operation involves little more providing a stable frequency the transmitter frequency than pushing the button and talk- source for multiplying up through slightly, for satellite working. ing. devices such as varactor tripiers. With this, the operator can comp- For this reason, experienced ensator for Doppler shift as the operators often prefer single- Technical features spacecraft approaches and sideband operation, where the Commercial amateur radio equip- recedes. technical demands are greater ment has changed considerably In some of the cheapest sets, and the rewards higher. With during the last few years. Perhaps the hand-held portables, fre- weak signals, s. s. b. has a consid- the most conspicuous develop- quency selection is by means of a erable advantage over f.m. and is ment, in v.h.f. transceivers at bank of thumbwheel switches. essential for serious long-dis- least, is that digital frequency This method works well enough if tance working. synthesizers have almost entirely the switches are reliable, though Nevertheless, many old hands displaced switched crystal oscil- some users may prefer to pay a bit do use f.m. A chat on two metres, lators and free -running variable more to have a digital display giv- possibly through the local repea- frequency oscillators. ing positive indication of the ter, can be a pleasant enough way True continuous tuning has tuned frequency. Many recent of whiling away the traffic jams on become virtually a thing of the portables have a low -power liquid the way to work. past in 2m equipment. Most sets crystal display, with a calculator - A type of set which has grown rapidly in popularity in recent times is the hand-held portable transceiver. Small enough to fit into the pocket, it can be taken anywhere; and for those with something grander at home, it makes a convenient second rig. The latest models offer perform- ance figures and features scarcely *For a more complex transceiver suitable for home construction, see T.D. Forrester's design in Wireless World, November 1982 to April 1983, with a postscript in August 1983. ELECTRONICS & WIRELESS WORLD JULY 1984 71

www.americanradiohistory.com TRANSCEIVER SURVEYS

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72 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com style keypad for rapid frequency certain other sets, r.f. modules Amateur Electronics UK receiver selection. The display may incor- The giving coverage of additional 504-516 Alum Rock Road porate extra features such as a share of bands are available as an acces- Birmingham 8 Receivers too have their sory. bar-graph meter to indicate trans- design improvements. Ceramic Tel. 021-3271497/6313 Tx power the transmitter power mitted power and received signal excellent filtering at Yaesu filters offer quoted by the manufacturer, nor- strength. In mains -powered sets, low cost, and new low -noise r.f. mally for the f.m. mode. Two Arrow Electronics Ltd or mobile equipment designed to are bringing enhanced devices figures separated by an oblique 5 The Street run from a car battery, a fluores- in front-end. performance the stroke indicate high and low Hatfield Peverel cent display is sometimes fitted: Beginning to make an appearance power settings. The separator Essex this may give better readibility equip- in commercial two -metre indicates that the power is Tel. 0245-381626 under unfavourable lighting con- arsenide fet. '>' ment is the gallium continuously variable between NDi ditions. in mind But it is worth bearing the limits shown. that fashionable components do Lee Electronics Ltd Syn/xtal: 's' denotes frequency - make a set bet- 400 Edgware Road not automatically synthesiser tuning, 'x' denotes a The transmitter ter. London W2 crystal oscillator providing only Tel. 01-723 5521 Receiver sensitivity usually those channels for which suitable The maximum power level per- prominently in radio Standard features crystals have been fitted. mitted to British amateurs on the promotional manufacturers' Em. step: the normal minimum Lowe Electronics Ltd 2m band (other than those with the figures material, though tuning step in n.b.f.m. use. Some Chesterfield Road special dispensation from the are not always expessed in quoted multi -mode sets are capable of Matlock, Derbyshire DE4 5LE licensing authority) is a carrier the same units and it can be diffi- much smaller steps even on f.m. Tel. 0629-2817/2430/4057 power supplied to the aerial of cult to raw meaningful comparis- In many cases, the size of the step Trio, Belcom 20dBW, or in the s.s.b. mode a ons. However, the 'goodness' of a is programmable: for example, peak envelope power (p.e.p.) of is affected by many other Microwave Modules Ltd receiver 12.5 and 25kHz can be selected 26dBW. These figures corre- factors, including resistance to Brookfield Drive to 100W and 400W instead of 5 and 10kHz if the user spond resistance to out -of - Aintree, Liverpool L9 7AN overloading, wishes. respectively. band signals and the quality of the Tel. 051-523 4011 Tuning method: 'd' indicates a The power output of the aver- filters. The sensitivity figures Numerous preamplifiers, power conventional knob or dial, age 2m mobile f.m. transceiver is not therefore be taken on amplifiers, converters and should `thumbw' indicates thumbwheel in the region of 10W. Since this their own as an index of the transverters switches and `u -d' indicates up - type of set is probably the most receiver's overall merit. common, there is little point down buttons. Modular Electronics Ltd As it is with cars, so with transc 95 High Street choosing something more power- cheapest will Memories: most present-day -eivers: even the Selsey, Chichester, Sussex ful unless the performance of its get you from A to B if the road is sets permit storage and instant of Tel. 0243-602916 receiver is better than average. open. So what are the advantages selection of a number the user's Preamplifiers, linear amplifiers There is no virtue in being able to of buying one of the more expen- favourite frequencies. Certain andr.f. components shout at other stations if their sive models? With radios, even models also have one or more replies are going to be lost in the costliest cannot offer extra variable -frequency oscillators Mutek Ltd noise. speed. But it can provide a range which can be used as additional Bradworthy With portable and hand-held of features designed to make a memories. Holsworthy transceivers, transmit power is session at the microphone more Scan modes: some sets allow Devon EX22 7TU usually restricted to a watt or two interesting and less tiring. scanning of frequencies stored in Tel. 0409 24 543 for reasons of battery life; but Among these are extra memo- memory ('m'), others provide Preamplifiers etc. often the power can be switched for storing commonly used scanning of the entire band ('b') ries Thanet Electronics Ltd to a still lower level for contacts frequencies; additional scanning or programmable sectors of it. 143 Reculver Road under good signal conditions, modes; accessories such as a S -meter most sets include a Beltinge, Herne Bay with a dramatic reduction in bat- voice synthesiser to supplement received signal -strength meter of Kent CT6 6PD tery drain. Under typical condi- the front panel display; plug-in some sort. Often this doubles as a Tel. 02273-63859/63850 tions, with one -minute transmis- radio -frequency modules for power level indicator. The entry Icom sion periods alternating with other bands; an interface unit 'bar' indicates a bar-graph indica- three minutes of listening, the life enabling the transceiver to be tor as distinct from a moving -coil South Midlands Communications expectancy of a battery pack is controlled automatically by the meter, 'mc'. Rumbridge Street likely to be in the region of two user's computer; and of course Receiver sensitivitr the figure Totton, Southampton SO4 4DP and a half hours. more transmitter power and a shown is, where possible, for the Tel. 0703 867333 The current drain in the stand- better receiver. f.m. mode. Yaesu, KDK by condition is a detail worth Power needs: some hand-held seeking out on the manufac- Notes on the table sets tolerate a wide range of sup- Waters and Stanton Electronics turer's data sheet. Some of the ply voltages, while mobile sets 18-20 Main Road early portables had led displays Price: the distributor's UK price, work best on the 13.8v provided Hockley, Essex which were so heavy on current including v.a.t. by a reasonably healthy car bat- Tel. 0702-206835/204965 that they had to be blanked for Style: entry indicates whether the tery. Figures for current indicate FDK, Trio much of the time. But if the user set is intended for portable, the consumption on standby and Wood and Douglas Ltd anticipates long periods of inten- mobile or base -station use. How- while transmitting on high power. Unit 13, Youngs Industrial Estate sive operation, it is worth looking ever, for many mobile units it is Battery, mA -hour storage capac- Aldermaston, Reading RG7 4PQ for a model with a quick -change possible to buy desk -top consoles ity of the standard battery. Most Tel. 0736-5324 battery pack so that a spare can be with mains power units; and for portable sets are supplied with 2m transceiver modules. slipped in when the output starts some portables, car fixing kits are nickel -cadmium rechargeable to droop. With certain sets, the available. batteries. Batteries of other sizes WPO Communications manufacturers offer a choice of Modes: 'f' indicates narrow -band may be available as an accessory. 20 Farnham Avenue packs in different sizes, some of f.m.; 's' indicates s.s.b.; `c' indi- many sets, portable and other- Hassocks them having a higher -than -usual cates c.w. wise, have a smaller battery (not West Sussex, BN6 8NS nominal voltage to give increased Other bands: this survey includes indicated here) for memory ret- Transceiver kits transmit power. one or two dual -band models. For ention. ELECTRONICS & WIRELESS WORLD JULY 1984 73

www.americanradiohistory.com FEEDBACK

10. We will now have a value 6.7 statement. Also, several unambiguous interpretation of PREFERRED (although it could be more). So commercial l.s.i. devices are (2) because velocity exists VALUES there are four possible values available which implement this between two physical entities available all of which would meet GPIB feature. As recently as and is not something that resides It is not unusual for the engineer the `no holes' criterion. 6.8 is the February 1984 your magazine independently within frames of to be condemned for only one to appear in the 5% described an interface module reference. incompetence when his strictly range, or in the 10% range for that available for the BBC Implicit in the theory as practical camel fails to look like matter. microcomputer using an I. s. i. developed from (1) and (2) are the mathematician's image of an Mr Scott tells my namesake device which includes bus control two generally unstated elegant but non-existent breed of that he will find the 'same transfer. propositions: horse. Preferred values are standard of arithmetic' in all More than one controller may selected not by rigid arithmetic, three ranges. Precisely so. have access to peripherals on a 3. Electromagnet radiations but as the result of some very However we have one more single GPIB through the existing impinge upon the surfaces of all clear and simple thinking about obstacle to overcome. Calculate standard using software. It is not materials conglomorates, from tolerances and their application the 5% range and you will get two necessary to spend time unoccupied space with the same to the real world. Since the 20% values (1.4 and 1.7) which do not designing a hardware multiplexer velocity c. range has produced the most appear in the standard, for GPIB controllers. The user glaring 'anomaly', let us use it as transgressing the 'no -holes' rule. who finds that he needs to attach 4. Unoccupied space has no our example. With them in there was a great several controllers to his bus will characteristic which regulates the To produce a series of figures deal of overlap, while without find a neater and quicker solution propagation of radiations such that any value will fall into them the holes are only very by selecting his bus controllers crossing it, except to guide it in a the tolerance band of one of small. The need to keep the with this capability built-in. straight path. them, they must be related so number of values to the There are several well known that the top end of the lower band minimum was presumably international manufacturers of To render (3) and (4) some coincides with the lower end of judged to be the over-riding GPIB instrumention, and several appearance of plausibility the higher one. In our case this is factor. less -well-known national ones, Einstein made the suggestion to say that 120% of the lower Even if the poor beast does who can supply GPIB controllers that 'The relations between should be 80% of the higher, so have bad breath, it is still not a with pass -control as a standard co-ordinates of two systems in they should stand in the ratio of 1 bad camel in a hard world! feature. uniform motion relative to each : 1.5 . In practice the 'Two -digit' Alan Watson J. Summers other cannot be indentical with rule will prevent this from always Pollense Application Manager those of Newtonian physics in being met, and rounding of a Mallorca Fairchild Camera and Instrument which simultaneity is absolute'. calculated value will be required. (UK) Ltd. The problem of interpretation This must always be in the sense of this assertion in terms of to close the gap between the two GPIB COMBINER experience is the real values, since the other way will IS LIGHT stumbling -block for relativity produce a 'hole' into which COMMENTS theory; the late Professor components could fall and so be I refer to the article in the April VELOCITY A Herbert Dingle strongly lost. This consideration also 1984 issue of Wireless World by suggested that no meaningful leads to the conclusion that when CONSTANT? interpretation is possible. Some D.J. Greaves. , the `GPIB rounding has taken place, the combiner'. The questions about relativity further propositions which next value must be based on that Mr Greaves' design, though theory will not go away; Michael readers may like to comtemplate rounded value and not the ingenious, is a complex hardware M. Albahari ("Is light velocity a are: calculated one. This destroys solution to a problem imposed by constant?" February letters) is once and for all any elegant his coice of GPIB controller. The mistaken if he considers that the 5. A unique universal medium (or arithmetic relation. Lastly, in particular machine he employs issue could be resolved by aether) propagates radiations at order to keep the total number of (the CBM Pet) does not accurate measurement of time the velocity c. values down as far as possible, it implement the full GPIB standard and distance; the real conflict is is sensible to select the 10% and lacks the ability to pass between incompatible 6. Material conglomerates values from those already control. The concept of the philosophical hypotheses. moving through the aether of (5) existing in the 5% range (if design is based on a fallacy The complex of notions suffer spatial contractions along possible) and the 20% from the brought about by the author's embodied into the Special Theory the axis of motion in proportion 10%. reliance on a particular of Relativity (and from which the to its rate and concomitantly We can now see where this manufacturer's interpretation the General Theory was developed their internal processes are reasoning gets us. Starting function of a GPIB controller. Mr by processes of logic) is based on retarded. initially from the lowest value: Greaves states 'The main two propositions selected from In his 1905 paper Einstein previous disadvantage of the [GPIB] bus is several alternatives: recognised the selected value selected that only one controller may be Lorentz -Fitzgerald contraction X 1.5 value connected to the string of 1. All inertial frames of reference time -dilation effects as peripherals at one time.' That are equivalent in their physical consequences of (2), the former 1 statement is incorrect. characteristics. effect being considered as 1.5 1.5 The IEEE -488 Standard 'apparent' and the latter as real, 2.25 2.2 specifically allows for multiple 2. Light travels in any fixed which was a blatant 3.3 3.3 bus controllers. A GPIB direction with the same velocity c inconsistency. 4.75 4.7 controller which implements the in all inertial reference systems. The development of the full IEEE -488 standard includes General Theory requires the Now the problem. On this basis the capability to pass control to Professor Albert Einstein Lorentz -Fitzgerald effects to be the next value should be 7.0 another controller connected to stated (2) as a corollary to (1) in physical; it is not generally stated (although it could be less) and the same bus. Most GPIB his 1905 paper 'Electrodynamics that this in turn produces the next is over 10 by quite a bit. controllers commercially of Moving Bodies', but difficulties with the Let us therefore consider what available include this capability, notwithstanding the validity of dynamics -energy possessed by happens if we calculate back from typically as a high-level language (1), it is impossible to give an rotating entities, and the 74 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com development of the theory to by finger and thumb and generate one and simple. I have used a require an increase of mass with XY PLOTTER about 50 volts or so in one system of crossed ball races with increase in velocity through the lam prompted to write to you winding by running it as a silver steel rods and this has ether violates the principle of because of the very interesting dynamo.Also, I have some proved quite good. See sketch. energy -mass conservation. XY plotter by P.N.C. Hill. I am motors from the States, including A further article dealing in Some further propositions retired now, from running a a Rapid Syn with four coils which much more detail, with the are: plastics injection factory, but has a magnetic hold so strong electronics of the plotter would have long been keen on that it is hard to turn by hand. be welcome to me and I suspect 7. Electromagnetic radiation electronics, photography, This performs very well as it has many others. emanates from every emitter astronomy. 12 volt coils and better torque A.J. Quinton with a velocity relative to that For a number of years, I have than the Slo Syn. Thorpe Bay emitter and remains directly been experimenting with a Despite this one seeming Essex. related to that emitter method of printing colour error, the article is most indefinitely (i.e. each emitter is photographs direct on to paper by interesting as I have made up a embedded in its own individual scanning as in the facsimile plotter in the past, using ordinary TECHNOCRATIC medium) . process. This started with EF5Os motors and a potentiometer BONDAGE? and multiplier cells and balance circuit to do transistor 8. All radiating media have progressed to transistors and has curve tracing. It was not very Your April leading article put the similar characteristics, and as a involved many different models good and needed to be refined so blame for restrictive aspects of corollary exist 'within or using ballpens and also carbon it was scrapped. our society on 'technocrats'. But 'throughout' each other, and have paper for the image. I even tried a Your write-up leaves out some government ministers rely on the a general propagational velocity mixture of metal indicators important details for me since it advice from their ministers, i.e. of c where remote from matter. soaked into paper with glycerine would be nice to make up a from civil servants, and it has and electrodes of copper, nickel stepper plotter controlled by long been notorious that few 9. The characteristics of media in and molybdenum to mark the Basic and digital -to -analogue graduates in science subjects (8) may be modified in the paper. So far, the carbon paper output from the computer with a make their way to the higher proximity of considerable has seemed the best to manage potentiometer to compare ranks of the civil service. (I guess conglomerates of dense matter. with limited funds to spend on positions. that in addition to the fact that Proposition (7) was originally research. The ball bearing idea is a good few of those who apply are stated by Michael Faraday (Phil. In the course of these Mag Vol.28, No.188, May 1846), experiments I have used various and as misinterpreted by Clerk steppers including the Clo-Syn Maxwell to have the meaning of motors from Stewart. Not being (5) and thus taken as providing good enough with logic circuits the basis for his equations of the have had to use simple chips like electromagnetic field. When (5) the 4017BE which give a decade View on end of rod appeared to have been rendered count from simple pulsing and showing ball races untenable by some rather inept can be made to count lesser steps exercises in research, Einstein by reset from one of the outputs. raised his 1905 paper in an The 4017 is used for 400 steps by attempt to show that we can have the circuit shown in my sketch. as many ethers as we like; he A useful chip is the SAA1027 made the mistake of implying which will drive a Slo-Syn motor that all receivers of radiation and reverse in an easy manner, must be embedded in their own but my circuits have been mainly individual ethers, this being the for unidirectional running... interpretation he gave of (2). I think by the way that Mr Hill Faraday's proposition (7) is wrong to state the rotor is not a amounts to the complement of permanent magnet. You can feel this, and avoids the complication the holding force if you turn this of (2). Although (1) maybe out .12v invalid if the physical universe 8V has a centre -point about which it is in rotation, and (2) cannot be 1k tested unless its ambiguity is Position of I e.ds resolved, (3), (5), (7), (8) and if required (9) can be subjected to physical investigation to varying degrees 5 of determination. It is doubtful that the Reset 1 3 members of professional bodies o are as yet prepared to embark on 100k 4 such work, since it would be o inexpedient to demonstrate that 100k 555 4017 their uncritical commitment to 100k relativity theory may have been 4 0'I 3 2 mistaken . 01 BM C. B. V. Francksen /10 Farnborough h f noise All TIP29 Hants stopper I 1F.AlI 1N4007

ELECTRONICS & WIRELESS WORLD JULY 1984 75

www.americanradiohistory.com accepted, it is probable that few system of which it is a part is in survive Occam's razor) and it the contrary it continues to apply.) So far from our troubles relative motion?. How is the must be refutable by established devise procedures for obviating being due to 'technocrats', many special theory related physically facts. them while at the same time are due to the fact that few of to quantum mechanics? Does the Now the special and general looking for more fundamental those in a position to influence paradox of the twins that age at theories of relativity, wave changes which would remove policy have what might be called different rates depend more on mechanics, gauge theories and so them altogether. A consensus is an 'engineering' outlook, a relative acceleration than on on are all fundamental in this beginning now to emerge on what knowledge of scientific fact and relative velocity? Is the special sense. All that their advocates the basis of a new theory might method plus some appreciation theory valid for systems in claim for them is that if you be. As usual in these matters the of the human side of instantaneous velocity rather assume them to be true, you can roots of the new theory go back a 'management'. than constant relative velocity? explain a wider range of facts long way - originally to On the narrow issue of GCHQ Einstein's early success (1911) in than you can if you assume them Hamilton's quaternions but more I can only say that those who go deriving the red shift formula for to be false. It is not a valid significantly to the work of Eli to work in such an establishment a gravitational field could only be objection to a fundamental Cartan at the beginning of the should be forewarned of the explained by assuming he used theory to say that it embraces a century. Cartan showed that a burden which 'security' will place relative instantaneous velocity. concept which clashes with your geometrical space could be on them. From the little which I Finally, does the wavelength old preconceived ideas, or that it discribed not only by vectors and have seen from the outside, I change under conditions of cannot be derived from tensors but also by more would regard this burden of relative motion between a light something else. elemental entities variously knowing things which must on no source and observer while the Science has always had called half -vectors or spinors. account be disclosed as the most velocity of the light is constant? trouble getting people to modify These entities were first used in serious factor associated with The constancy of wave length their tenaciously held ideas: the physics by Pauli and slightly later such work. (and associated wave number) is sun revolves around the earth, by Dirac who in 1930 constucted D. A. Bell an unwarranted carryover from action at a distance is a relativistically covariant wave North Humberside classical physics, and even conceptually impossible, and so equation in which electron spin is Einstein himself showed his on. Even today people get stuck inherent. What is now becoming RELATIVITY conservative nature is making with wrong ideas through failing apparent is that the spinor this latter assumption. to look at all the evidence; a formulation may also be required Much discussion concerning the G. Blondeau, clockmaker would say that the to remove the difficulties of Special Theory of Relativity has CANMET, Dept of Energy, great property of a pendulum is macro -theory. appeared of late both in your Mines & Resources, that its period is constant but a Dr Murray may denounce letter columns and in other Ottawa, Ont., church bellringer would say that these developments as even publications, even to the CANADA the one thing which makes more counter to common sense extremes of scrapping the theory change ringing possible is the fact than Minkowsky space but then altogether and returning to the I am beginning to get the hang of that a small change in the common sense has never been of day of classical mechanics and much that you have recently amplitude makes a big difference much help in theoretical physics. the aether. On the other hand, printed; in spite of the titles, it to the period! The nub of the matter is however some have raised more fruitful has had nothing to do with J. G. D. Pratt. easily explained to any suggestions concerning the relativity! West Horsley reasonably competent physical basis of the relativistic Science comprises a Leatherhead mathematician. Spinors are a (or e-m) Doppler shift. considerable body of facts and Surrey sort of complex number, Surely at this stage in the theories which support one distinguished from ordinary career of that theory it should be another and which are widely You do your journal no service by complex numbers by the fact that evident that the theory suffers considered to be true. This body continuing to publish these their law of multiplication is not from a number of definite can grow in two very different embarrassing articles by Dr in general commutative, that is, shortcomings: (a) it is physically ways. We may wake up to new Murray. It is true that there are AXB is not necessarily equal to incomplete, i.e., certainly implications of what is already serious imperfections in both B XA. In a group of spinors there questions of physics are still left accepted -'new', that is, in the Relativity and Quantum is usually a sub -group whose open by the theory itself; and (b) sense that no one had got round Mechanics and if Dr Murray multiplication law is as basically a correction factor to to digging them out before - or confined himself to explaining commutative and whose classical electrodynamics it we may add new facts which fit in them to your readers one could properties palely reflect those of suffers from a instrumentalist to the old body and so consolidate not object, even if one had the full group; in the present case interpretation that prevents it. That is, we may build on the doubts whether he was the man this sub -group is the complex these fruitful physical questions old structure. best qualified to do so. But it is numbers. What physics in from being asked, i.e. , the But we can also work on the really too much when, although general has been doing up to now theory concerns rigid rods and foundations. Some of the apparently not able to offer any is to use complex numbers when clocks, but does not directly have theories in science are constructive comment himself, they should have been using the a microbasis. fundamental, which means that he jeers at those men who have, full group. Thus they have been Assuming that there is some their truth cannot be inferred over the years, painstakingly put in much the same situation as validity in these observations on from other accepted facts or these theories together. Newton electrical engineers trying to the theory the following theories- their sole purpose is to is supposed to have said tht he make do with real numbers, questions seem to be quite open. provide explanations of other saw so far because he stood on knowing nothing about complex What is the physical basis for the theories and facts. Science likes a the shoulders of giants. No such ones. constancy of light's velocity if fundamental theory if it is felt on humility from Dr Murray who can If a new theory along these there is relative motion between balance inexplicable things apparently see nothing from an lines is ever formulated and source and the observer, outweigh the unsatisfactory even better vantage point. accepted it will be because it especially since the classical aspect of introducing a new The community of theoretical works better than the one it physics requires that velocity to inexplicable idea, and provided scientists - Dr Murray's replaces. vary? that it does not lead to inferences despised establishment - is well What is the physical basis for which conflict with observations. aware of the imperfections of E. R. R. Holmberg clocks (or any natural process) In other words a fundamental fundamental theory but is far Barnes running v . slower n the inertial theory has to be useful (it must from complacent about them. On London SW13 76 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com The heavy duty versions of the Avo 1000 Series have to pass a lot of tests that aren't electrical. Under normal operating conditions, you can depend on the Avo 1000 Series to give long and reliable performance. However, we appreciate that a lot of users subject their test instruments to treatment that is far from normal. They drop them into their toolkits, throw pliers onto them or take them into hot and sticky boiler rooms. So to make a tough range of instruments even tougher, we have developed a special rubberised coating which is moulded directly onto the casing. We put all our instruments through a series of tests that make normal rough treatment look like delicate handling. We flash test them, we subject them to intense vibration, bump them up and down for hours, make them sit in difficult climatic conditions and drop a heavy metal rod on them from a substantial height. All this apart from the routine electrical tests they have to pass! So if you want quality analogue multimeters that can take a lot of stick and continue to give e., accurate performance, ask about the HD versions of the Avo 1000 Series at your usual distributor.

L THORN EMI Instruments Limited Archci ffe Road. Dover. Kent CT17 9EN Telephone 0304 202620 Telex 96283

CIRCLE 76 FOR FURTHER DETAILS. www.americanradiohistory.com PHONE P. M. COMPONENTS LTD TELEX 0474 813225 SELECTRON HOUSE, WROTHAM ROAD 966371 3 LINES MEOPHAM GREEN, MEOPHAM, KENT DAI3OQY PM COMP

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3.50 MSM5807 6.75 TA7222AP 1.80 TDA2680A 2.75 DN13.78 35.00 M38 -142LÁ 65.00 TBA8200 1.45 TDA2690 2.45 CME822GH 25.00 HA1156W 1.50 PLLO2A 5.75 TA7227P 4.25 F15.101 LC 49.00 M38 -340P31 65.00 TBA890 2.50 TDA3560 5.50 CME1428GH 45.00 HA1339A 2.95 SAA500A 3.50 TA7310P 1.80 CME1428W 39.00 F16-101GM 55.00 M38.341GR 65.00 HA1551 2.95 SAA1025 7.25 TA7313AP 2.95 TBA920 1.85 UPC566H 2.95 TBA950/2X2.35 CME1523GA 39.00 F16-101 LD 55.00 M38 -341P31 65.00 LA1230 1.15 SAA5010 6.35 TA7321P 2.25 UPC575C2 2.75 F21-130GR 55.00 M38 -344P39 65.00 TBA970 2.95 UPC1025H 1.95 CME1523W 39.00 LA4102 2.95 SAS560S 1.75 TA7609P 3.15 F21-130LC 55.00 M40 -120W 59.00 TBA990 1.49 1.95 CME1431GH 39.00 LA4250 2.95 SAS570S 1.75 TA7611AP 2.95 UPC1028H F21-131GR 79.00 M43-12GM/01 65.00 TBA1441 2.15 UPC1032H 1.50 CME1431W 39.00 LA4400 4.15 SAS580 2.85 TAA550 0.25 F22-11LD 53.00 M43-12LG/01 65.00 TCA270 1.10 CME202GH 45.00 LA4420 1.95 SL901B 4.85 TAA570 1.95 UPC1156H 2.75 F31-10GM 65.00 TCA270SQ 1.10 CME2024W 45.00 M44-120LC 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SN76115N 1.25 TBA395 1.50 TDA1035 2.50 UPC2002H 1.95 TDA1037 1.95 CV1526 19.00 F41-141LG 160.00 SE4/D/P7 45.00 M51515L 2.95 SN76131N 1.30 TBA396 0.75 555 0.35 F41-142LC 185.00 55.00 TDA1170 1.95 CV2185 15.00 SE428P31AL M51521L 1.50 SN76226DN 2.95 TBA440N 2.55 556 0.42 55.00 TDA1190 2.15 CV2191 19.00 M7 -120W 19.00 SE42BP31 MB3712 2.00 SN76227N 1.05 TBA4800 1.25 723 0.50 M14-100GM 45.00 SE52AP31AL 55.00 1.65 TDA12700 3.95 CV2193 15.00 MC1307P 1.00 SN76533N TBA510 2.50 741 0.35 M14-100KA 55.00 SE5FP31 55.00 1.50 1.95 TDA1327 1.70 747 0.50 CV2328 85.00 MC1310P SN76544N TBA5100 2.50 85.00 M14-100LC 45.00 T937 65.00 MC1327 0.95 SN76570N 1.00 TDA2002 1.95 748 0.35 CV5119 TBA520 1.10 CV5320 85.00 M17-151GVR 175.00 T948N 65.00 MC1327Q 0.95 SN76650N 1.15 TDA2020 2.95 7805 0.65 TBA5200 1.10 CVX389 55.00 M17-151GR 175.00 7948H 65.00 MC1330P 1.10 SN76660N 0.80 TBA530 1.10 TDA2030 2.80 7808 0.60 D9-110GH 39.50 M19-100GY 55.00 V3191 59.00 MC1349P 1.20 S -i K014 7.95 TDA2522 1.95 7815 0.65 TBA530Q 1.10 D9-120 45.00 M19 -100W 45.00 V4150LC 55.00 MC1350P 1.95 STK015 7.95 TDA2523 2.95 TBA540 125 D10-210GH 45.00 M19-101GR 55.00 V4254B 65.00 M19 -103W 55.00 V4274GH 65.00 BFR40 023 TIP29 0.40 D10-210GH68B 65.00 I M23-110GH 55.00 V4283W 65.00 SEMICONDUCTORS BD225 0.48 BFR41 028 TIP29C 0.42 D10-210GH72 65.00 35.00 M23-111W 55.00 V5002LD 65.00 AAY12 0.25 0.09 BC232 0.35 TIP30C 0.43 D10-230GH BC174A BFR81 0.25 35.00 M23-111GH 55.00 V5004GR 59.00 AC126 0.45 BC177 0.15 BD233 0.35 TIP31C 0.42 D10 -2300M BFR88 0.30 D10-293GY/90 55.00 M23-111LD 55.00 V5004LD 59.00 AC127 0.20 BC178 0.15 BD234 0.35 BFR90 1.50 TIP32C 0.42 TIP33B 0.75 D13-27GH 49.50 M23-112GM 55.00 V6001GH 65.00 AC128 0.28 8C182 0.10 BD236 0.45 BFR91 1.75 V6006GH 65.00 TIP3413 0.75 D13-30GH 49.50 M23-112GV 55.00 AC128K 0.32 5C182L8 0.10 8D237 0.40 8E742 0.28 M23-112GW 55.00 V6007DP31 59.00 AC141 0.28 BD238 0.40 TIP41A 0.45 013-33GM 49.00 BC183 0.10 8E743 0.28 M23-112KA 55.00 V6007GW 65.00 AC141K 0.34 TIP41C 0.45 D13-47GH/26 55.00 BC183L 0.09 BD241 0.40 BFW92 0.85 M23-112LD 55.00 V6008GW 59.00 AC142K 0.30 BC184LB 0.09 BD242 0.50 TIP42C 0.47 D13-47GH/34 55.00 BFX29 0.30 D13-47GH 55.00 M23-112W 55.00 V6008W 65.00 AC176 0.22 8C204 0.10 BD246 0.80 BFX84 0.26 TIP47 0.65 TIP120 D13-51GH/34 85.00 M24-120GM 59.00 V6034WA 59.00 AC176K 0.31 BC207B 0.13 BD376 0.32 BFX85 0.32 0.60 M24-120GR 59.00 V6048CLA 59.00 TIP125 013-51GL/26 85.00 AC187 0.25 8C2088 0.13 BD410 0.55 BFX86 0.30 0.65 M24-120LC 59.00 V6048F 65.00 AC187K 0.28 0.09 BD434 0.55 TIP142 1.75 013-51GM/26 85.00 BC212 8FX88 0.25 55.00 M24-120WAR 59.00 V6048J 49.00 AC188 0.25 BC212L 0.09 BD437 0.50 TIP146 2.75 013-4500H/01 BFY50 0.21 D13-471GH/26 55.00 M24-121GH 55.00 V6052GH 65.00 AC188K 0.37 BC212LA 0.08 BD438 0.80 BFY51 0.21 TIP161 2.95 59.00 TIP2955 D13-550GH 65.00 M24-121LC V6052GR 65.00 AD142 0.79 BC213 0.09 80520 0.65 BFV52 0.25 0.80 M24-121 WA V60648LA AD143 TIP3055 0.55 D13 -6000M 59.00 59.00 65.00 0.82 BC213L 0.09 BD538 0.65 BFY90 0.77 M28-11LA 49.00 V6064BP31 55.00 AD149 0.70 BC214 0.09 BD597 0.75 TIS91 0.20 013-610GH 59.00 D13-610GM 59.00 M28-12GH 55.00 V6064CLA 55.00 AD161 0.39 BC214C 0.09 BD701 1.25 89100 026 TV106/2 1.50 V6069GH 55.00 282110 4.50 D13-611GH 59.00 M28-12LC 55.00 A0162 0.39 BC214L 0.09 80702 1.25 BR101 0.49 V6070P31 49.00 282219 0.28 D13-611GM 59.00 M28-13LC 49.00 AD161/2 0.90 BC237B 0.09 BD707 0.80 BR103 0.55 M28-13LG 49.00 V7016A 65.00 AF106 0.50 BC238 0.09 80X32 1.50 282905 0.40 D13-630GH 59.00 BRC4443 0.85 65.00 M28-13GR 49.00 V7030 59.00 AF114 1.95 BC239 0.12 BDY57 1.65 2N3053 0.40 D14-120GH08 BT100A/02 0.75 65.00 M28-13WA 49.00 V7031GH 59.00 AF121 0.60 BC251A 0.12 8F115 0.35 2N3054 0.59 014-121GH09 8T106 1.49 D14-150GH 75.00 M28 -131Gß 55.00 V7031 /67A 59.00 AF124 0.85 BC252A 0.15 8E119 0.65 BT116 1.20 2N3055 0.52 2N3702 D14-150GM 75.00 M28-132GM 55.00 V7035A 49.00 AF125 0.35 BC258 0.25 8F127 0.24 BT119 2.35 0.12 M28-133GH 55.00 V7037GH 45.00 2N3703 0.12 D14-172GH/84 59.00 AF126 0.32 BC258A 0.39 8F154 0.12 BT120 1.65 -1000H 55.00 V8004GR 65.00 5C264 D14-172GR 55.00 M31 AF127 0.40 0.30 8F158 0.22 130105 122 283704 0.12 55.00 V8006GH 65.00 0.30 014-172GV 55.00 M31-101GH AF139 0.40 BC300 6F160 027 BU108 1.89 2N3075 0.12 M31-182GR 55.00 V8010A 65.00 AF178 0.30 283706 0.12 014-173GH 55.00 1.95 8C301 8F167 024 BU124 125 M31-182GV 53.00 1CP1 15.00 0.12 014-173GM 53.00 AF239 0.42 BC303 0.26 8F173 0.22 BU125 125 2M3708 M31 -183W 55.00 1CPB1 15.00 AU107 BC307B 0.09 BF177 0.38 283773 D14-173GR 55.00 3.50 BU126 1.60 2.75 M31 -184W 85.00 2BP1 9.00 AU106 3.25 BC327 0.10 13F178 0.26 283792 1.35 1314-181GH/62 65.00 8U204 1.55 M31-184GH 65.00 3BP7 13.50 AU110 2.00 8C328 0.10 8F179 0.34 284280 3.50 D14-181GH/98 65.00 BU205 1.30 55.00 M31 -184P31 65.00 4EP1 30.00 BC107A BC337 0.10 13F180 0.29 2N4427 1.50 D14-181GJ 0.11 BU208 1.39 53.00 M31-185GH/VR 69.00 3H/0BM 55.00 BC107B 0.11 BC338 0.09 13F181 0.29 284444 1.15 D14-181GM BU208A 1.52 D14-181GM50 59.00 M31 -186W 69.00 5BP1 9.00 BC108 0.10 BC347A 0.13 8E182 0.29 BU208D 1.85 285294 0.42 58HP1 30.00 BC461 0.35 8F183 0.29 285296 0.48 D14 -181W 55.00 M31-19005 55.00 BC1084 0.11 BU326 1.20 M31-190GR 55.00 5BHP1 FF 30.00 BC478 8F184 0.28 D14-182GH 59.00 BC108B 0.12 020 BU407 124 285298 0.60 M31-190LA 55.00 5BHP31 30.00 BC527 020 8F185 0.28 D14-182GM/98 65.00 BC109 0.10 BU500 2.25 285496 0.65 5CP1 10.00 . M31 -190W 59.00 13C547 0.10 8E194 0.11 2SA715 0.60 O 14-2008E 89.00 BC109/3 0.12 BU526 1.90 M31-191GH 59.00 6EP7/S 39.00 BC109C BC548 0.10 8F195 0.11 D14-200GA/50 85.00 0.12 8080V 225 2SC495 0.80 M31-191GR 59.00 13BP1 13.50 BC549A 0.08 8F196 0.11 014-2000M 75.00 BC114 0.11 BUV6913 1.70 2SC496 0.80 M31-191GV 55.00 13BP4 17.50 BC550 0.08 8F197 0.11 D14-210GH 75.00 BC116A 0.15 MJ3000 1.98 2SC1096 0.80 M31 -191W 59.00 17DWP4 25.00 BC557 0.08 13F198 0.16 D14-270GH/50 75.00 BC117 0.19 MJE340 0.40 2SC1106 2.50 -192W BC119 BC5578 0.08 8F199 0.14 014-310W 110.00 M31 59.00 32J/1085 69.00 024 MJE520 0.48 2SC1172Y 2.20 M31-195GH 59.00 880 15.00 BC125 0.25 BC558 0.10 8F200 0.40 2SC1173 D14-320GH 85.00 MPSA13 0.29 1.15 D14-320GH/82 85.00 M31-210GH 59.00 89B 15.00 8C139 020 BCY33A 1.60 ' 13F241 0.15 2SC1306 1.00 MPSA92 0.30 M31 -220W 59.00 89D 15.00 8C140 0.31 BD115 0.30 BF245 0.30 2SC1307 1.50 O 14-340GH/KM 45.00 MRF237 3.45 M31-270GV 65.00 89L 15.00 BC141 025 80116 0.80 BF256/LC 028 2SC1364 0.50 D14-340KA 45.00 MRF450A 12.50 M31-271 P31 65.00 1273 39.00 BC142 021 D16-100GH 65.00 BD124P 0.59 8F257 0.28 MRF453 17.50 2SC1449 0.80 M31-271GW 65.00 1564 39.00 BC143 024 BD131 0.42 BF258 2SC1678 1.25 D16-100GH/65 69.00 0.28 MRF454 23.50 M31 -271W 65.00 1844 45.00 BC147 0.09 BD132 0.42 8F259 2SC1909 1.45 D16-100GH/67 65.00 0.28 MRF475 2.50 75.00 M36 -12W 75.00 55451GM 75.00 BC147B 0.09 BD133 0.40 BF271 0.26 2SC1945 2.65 D16-100GH67A MRF477 10.00 69.00 M36-141LA 75.00 9442E1 80.00 BC148A 0.09 BD135 0.30 BF273 0.13 2SC1953 0.95 D16-100GH/79 OC16W 2.50 75.00 M36-141LG 75.00 95447GM 75.00 BC1488 0.09 50136 0.30 8F336 0.34 2SC1957 0.80 D16-100GH/79A 0C23 1.50 65.00 M36-141W 75.00 95449GM 75.00 BC149 0.09 BD137 0.32 BF337 0.29 2SC1969 1.95 D16-100GH97 0C42 0.55 D18-130GH 65.00 M36 -1701G 75.00 7709631 78.50 BC157 0.12 130138 0.30 6F338 0.32 0C44 0.75 2SC2028 1.15 M38-100GR 65.00 BC158 0.09 BD139 0.32 8F355 0.37 2SC2029 1.95 D18-1300GH/70 69.00 0C45 0.55 69.00 M38-101GH 65.00 8C159 0.09 BDD140 0.30 9F362 0.38 2SC2078 1.45 D18-160GH OC70 0.45 D21-10GH 65.00 M38-103GR 65.00 BC160 0.28 BD144 1.10 8F363 0.38 2SC2091 0.85 OC71 0.55 69.00 M38-113GH 85.00 BC161 028 60159 0.85 8F371 020 2SC2098 2.50 D21-10GJ 0081 0.50 021-1010 69.00 M38.120W 65.00 8C1700 0.15 BD160 1.50 8F394 0.19 R2008B 1.70 2SC2166 1.95 BF422 D21-102GH 65.00 M38-120WA 65.00 BC171 0.09 BD166 0.55 0.32 920105 1.70 2SC2314 0.80 M38-121GR 0.72 8E457 0.32 2SC2371 0.36 DB7.6 35.00 65.00 BC171A 0.10 BD179 R2322 0.58 M38.121GHR BC171B 0.10 BD182 0.70 13F458 0.38 2SD234 0.50 DG7.32 45.00 65.00 R2323 0.66 DG13.2 45.00 M38-121 LA 65.00 BC172 0.10 BD201 0.83 BF459 0.38 R2540 2.48 3N211 1.95 BC172B 0.10 00202 0.65 8F467 0.68 3SK45 0.70 DH3.91 45.00 M38-121 WA 65.00 RCA16334 0.90 DH7.11 95.00 M38-122GH 65.00 BC172C 0.10 BD203 0.78 8F595 0.23 RCA16335 0.80 3SK88 0.55 BC173B 0.10 B0204 0.70 BF597 0.25 SKE5F 1.45 BC174 0.09 130777 0.48 BFR39 023 BY206 0.14 N23WE 2.95 LI NE OUTPUT TRANSFORMERS E H T MULTIPLIERS VARICAPTUNERS PUSH BUTTON UNITS DIODES BV208-800 0.33 N4001 0.04 BY210-800 0.33 N4003 0.04 DECCA 100 7.95 ITT CVC20 8.35 ELC1043/05 MULLARD 8.85 DECCA, ITT, CVC206WAY 7.95 6.35 ELC1043/06 MULLARD 8.85 AA119 0.08 BV223 0.90 N4004 0.05 DECCA 1700 MONO 9.95 ITT CVC30 ITT CVCS 7 WAY 10.19 6.96 U321 8.25 BA115 0.13 BY298-400 0.22 N4005 0.05 DECCA 1730 8.95 PHILIPS G8550 PHILIPS G8 (55016 WAY 14.49 BA145 0.16 BV299-800 0.22 N4007 0.06 DECCA 2230 8.25 RANK T20A 6.91 U322 8.25 BA148 0.17 BVX10 0.20 N4148 0.02 GEC 2040 8.95 THORN 3000/3500 7.57 BA154 0.06 BYX36-1509 0.20 N4448 0.10 GRUNDIG 1500 15.45 THORN 8500 5.80 POTENTIOMETERS 20MM QUICK BLOW FUSES 8.00 BA156 0.15 BVX38-600R 0.60 N5401 0.12 GRUNDIG 5010-6010. 2222.5011-601113.45 THORN 9000 STANDARD VERTICAL POTS 0.12 5.45 100MA tip each BA157 0.30 BVX55-6000.30 N5402 0.14 ITT CVC20 8.20 UNIVERSAL TRIPLER MIN. VERTICAL POTS 0.12 200MA - 5AMP 5p each BAX13 0.04 BYX71-600 1.10 N5403 0.12 ITT CVC30 8.25 SANDARD 16 0.06 PHILIPS G8 8.50 BAX BZY95C30 0.35 N5406 0.13 REPLACEMENT HORIZONTAL POTS 0.12 BB105B 0.30 C54B 4.50 N5407 0.16 PHILIPS G9 8.99 MIN. HORIZONTAL POTS 0.12 20MM ANTI SURGE FUSES BT151 0.79 CS10B 8.45 N5408 0.18 PHILIPS G11 13.39 ELECTROLYTIC CAPACITORS CONVERGENCE PRE-SETS 0.30 BV126 0.10 0A47 0.09 TT44 0.04 PYE 725 10.95 SLIDERS LOG 0.48 100MA - 800MA 15p each DECCA BY127 0.11 OA90 0.05 TT923 0.15 R8M T20A 12.40 30(400-400/350V ) 2.85 SLIDERS LINEAR 0.48 1A - 5AMP 12p each BV133 0.15 0A91 0.06 TT2002 0.10 TANDBERGE90" 11.15 DECCA 80/1001400/350V) 2.99 BV164 0.45 OA95 0.06 TELEFUNKEN711A 11.15 DECCA 1700 SPARES & AIDS BV176 1.20 OA202 0.10 THORN 1590 9.50 (200-200-400-350V) 3.55 BV179 0.63 1821 DR 2.95 THORN 8000 9.20 GEC 2110 (600/300V) 2.25 FOAM CLEANSER 0.79 PUSH PULL MAINS SWITCH 74LS SERIES THORN BT182 0.55 IN23B 2.95 Prices 9000 9.95 ITT CVC20 (200/400V) 1.80 FREEZE IT 0.82 (DECCA, GFC, RANK, THORN BV184 0.35 IN23C 2.95 available THORN 9800 22.40 PHILIPS 08 (600/300V) 2.25 SOLDA MOP 0.64 ETC.) 1.02 THORN IF BV199 0.40 IN23ER 2.95 on request MAIN TRANSFORMER PHILIPS G9 (2200/63V) 1.19 SWITCH CLEANER 0.79 PVE GAIN MODULE 6.99 3000/3500 9.70 PHILIPS G11 (470/250V) 2.35 W D40 1.25 ANODE CAP (27kV) 0.69

78 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com PHONE P. M. COMPONENTS LTD TELEX 0474 813225 SELECTRON HOUSE, WROTHAM ROAD 966371 3 LINES MEOPHAM GREEN, MEOPHAM, KENT DAI3OQY PM COMP l®1

141 3.50 RG3.250A 3.50 VII IUI [.W 3C45 24.00 0.72 7A7 PCL82 0.85 6B07A 2.00 85A2 1.50 L42DD 3.50 RG3-1250A VR105/30 1.50 3CN3A 2.50 6BL7GTA 3.95 7AD7 1.75 90AV 10.00 . FROM PCL83 2.50 A SELECTION OUR 190 0.70 35.00 VR150/30 1.15 3CS6 0.95 6818 0.85 767 2.50 PCL85 0.80 90C1 2.70 192 1.50 RK2K25 62.50 VT52 2.50 6885 0.70 7C6 2.50 90CG 13.50 STOCK OF BRANDED VALVES PCL86 0.85 3CX3 2.50 L133/DD 3.50 1304-1000 10.00 6887 4.95 7E7 2.50 91AG 9.00 PCL200 1.60 VU29 4.50 3CY5 1.50 R2 4.00 RK -20A 12.00 68R8 2.15 7Y4 92AG A1714 18.50 E1524 8.95 EF732 3.50 PCL800 0.80 VU39 1.50 306 4.50 1.95 19.50 Y90 1.00 6116 1.50 W77 5.00 3D21A 29.50 6BR8A 2.15 888 2.50 92AV 12.50 A1998 11.50 EA50 1.00 ' EF800 11.00 PCL805 0.90 VR2 3.00 RPL16 12.00 3022 19.50 6857 5.50 8FQ7 1.95 A2087 11.50 EA76 1.95 EF805S 13.50 PD500 3.50 W729 1.00 95A1 8.50 60.00 RPY13 2.50 6858 2.50 1002 1.25 A2134 14.95 EA79 1.95 EF806S 14.50 J -7A P0510 3.65 W739 1.50 3W4GT 2.50 108C1 1.50 391A 95.00 RPY43 2.50 X24 1.00 41355113 115.00 66W4 1.50 10F1 0.75 15082 6.95 A2293 6.50 EABC80 0.70 EF812 0.85 PEN4DD 2.00 3118 85.00 RPY82 2.50 X66/X65 4.95 4-65A 59.00 6BW6 5.35 100(6 1.95 A2599 37.50 EAC91 2.50 EFL200 1.50 PEN25 2.00 150C2 1.50 46/3 45.00 RR3-250 15.00 X76M 1.95 4-250A 65.00 6BW7 1.50 10P14 2.50 A2900 11.50 EAF42 1.20 0.72 PEN40DD 2.50 150C4 2.15 TBC 7.00 RR3-1250 33.50 4632 19.50 68W8 4.00 10P18 0.78 A3042 24.00 EAF801 350. EK9Ó 0.72 PEN45 3.00 XC24 1.50 155UG 25.00 T33C 3.50 R5613 45.00 XC25 0.50 4B07A 1.75 68X6 0.48 101011 1.00 A3283 24.00 EB34 150 EL32 0.95 PEN45DD 3.00 1858T 1.50 4.00 T36 2.00 RS685 54.95 XFW47 1.50 4C27 25.00 6BX7GT 3.50 101012 0.65 274A 15.00 AC/HL/DD 4.00 E 04 3.95 EL33 PEN46 2.00 T44 4.00 RS688 52.15 XFW50 1.50 4C28 25.00 6826 2.50 11E2 16.50 AC/THI 4.00 EB91 0.6 0 EL34 2.25 PFL200 0.95 307 5.00 145 4.00 S6F17 5.95 XG2 -6400 4CX250BI.T.T. ' 6827 2.95 11E3 55.00 328A 15.00 ACT22 59.75 EBC33 2.50 EL34 Philipspe PL21 2.50 T61 4.00 S6F33 28.95 35.00 37.50 6C4 1.10 12AD6 1.50 ACNP2 4.00 EBC41 1.95 9 PL36 0.95 388A 17.50 T63 2.00 S11E12 38.00 XG5-500 22.50 4CX2508 6C5 1.95 12AG8 1.50 425A5 AC/S2PEN8.50 EBC81 150 EL36 1.50 PL38 1.50 8.00 166 OSRAM S30/2K 12.00 XL1-5V 1.50 EIMAC 49.00 6C6 2.50 12AL5 1.00 AH221 39.00 EBC90 0.90 EL37 9.00 PL81 0.72 4310 2.00 10.50 5104/1K 10.00 XL628FT 7.50 4C X25013 6C8G 1.50 12AT6 0.95 AH238 39.00 EBC91 0.90 EL38 4.75 PL81A 0.72 572B 35.00 6C11 2.50 12AT7 1.15 AL60 6.00 EL41 3.50 T66 USA 6.90 PL82 0.80 5109/1K 15.00 XNP12 2.50 surplus ex- 705A 8.00 EBF33 2.50 6C15 2.50 12AT7WA 2.50 ANI 14.00 EL42 2.00 T66 GEC 14.95 PL83 0.52 S130 5.95 XP1002 29.00 government 708A 8.00 EBF80 0.65 S130P 5.95 6C18 2.50 12AU6 1.50 ARP12 0.70 EL81 6.95 177 Gold Lion PL84 XR1-1600A 12.50 715A 6.00 E13F83 0.65 0.78 SC1/800 5.00 6CA4 0.60 12AU7 0.55 ARP34 1.25 EL82 0.58 9.50 PL88 1.00 49.50 4CX2506 715C 45.00 EBF85 0.95 6CA7 3.50 12AV6 0.80 ARP35 2.00 EL82 0.75 181 7.00 PL95 1.75 SC1/1200 5.00 XR1-3200A tested ex- 725A 275.00 EBF89 0.70 SC1/2000 9.00 equipment 6C86 1.95 12AX4GT 1.00 0L63 2.00 0.95 EL85 4.50 188 USA 9.00 PL302 1.00 79.50 803 14.95 EBF93 SD6000M 6CD6GA 4.50 12AX7 0.85 65450 67.00 EBL1 2.50 EL85 0.85 T88 Gold Lion PL345 12.50 XR1-6400A 6.00 805 39.00 15.95 45.00 4CX2508M 6CF6 1.50 12AX7WA 2.50 BS810 55.00 EBL21 2.00 1.50 PL500 1.10 99.50 807 1.60 SP2 1.50 EIMAC 75.00 6CH6 6.95 12AY7 3.95 BS814 55.00 EC52 0.75 EL99 T67 9.00 P1504 1.15 Y63 1.50 810 45.00 SP41 5.00 6CL6 3.25 12AZ7A 1.95 CIK 19.00 EC70 1.75 EL95 0.70 TW61 2.50 PL508 1.75 Y65 8.95 4CX250K 811A 12.95 SP42 3.00 EIMAC 95.00 6CL8A 2.00 12B4A 3.50 C3JA 21.00 EC80 9.50 EL153 12.15 TW62 2.50 PL509 4.85 Y602 12.00 813 18.50 SS501 35.00 YD7100 4CX350A 71.50 6CM5 1.60 12BA6 1.50 C1108 54.95 EC81 7.95 EL183E 3.50 TW63 2.00 PL519 4.95 75.00 813USA 45.00 ST11 1.50 6CS6 0.75 120E6 1.05 C112G 70.00 EL18P 3.50 TZ63 2.50 131802 5.95 VJ1060 265.00 4026 75.00 8296 14.50 EC86 1.00 6CW4 6.50 129H7A 2.50 C1134 32.00 EC88 1.00 E1360 6.75 63 1.50 P18021 3.50 STV280/40 YL1020 29.00 4GS7 2.25 833A 60.00 11.95 4GV7 2.25 6CY5 1.00 12616 1.75 C1148A 115.00 EC90 1.10 E1500 1.40 102/2K 6.95 PL820 2.95 YL1070 115.00 866A 3.50 STV280/80 4.152 75.00 6DC6 2.35 12BY7A 2.75 C1149/1 130.00 EC91 5.50 EL504 1.40 120/2K 12.00 PL5557 29.50 YL1071 109.00 872A 19.00 4JC6A 6DK6 1.15 12CX6 1.20 C1150/1 135.00 EC92 1.25 EL509 5.25 87-20 95.00 PY32 0.60 19.95 Z77 1.20 2.95 873 60.00 4.95 4X150A 6005 3.35 12E1 17.95 C1534 32.00 EC93 1.50 EL519 6.95 S9B 6.95 PY33 0.50 SU42 Z302C 12.00 25.00 884 5.50 TB2.5/3000 5A/102D 9.50 600613 2.50 12E14 28.00 CCA 2.80 EC95 7.00 EL802 3.65 502A 60.00 PY81 0.70 Z359 9.00 930 9.95 65.00 6EA8 2.50 12GN7 3.95 CC3L 0.90 EC97 1.10 EL821 8.50 PY82 0.70 85.00 Z505S 15.00 5A152M 9.00 931 A 13.95 6E88 1.75 12HG7 4.50 CL33 2.00 EC8010 12.00 EL822 12.95 537A 80.00 PY83 0.70 TB2-300 45.00 2520M 4.00 5A163K 10.00 954 1.00 TBL-2-300 6EU8 1.75 12HG7A 4.50 CVNosPrices ECC32 3.50 EMI 9.00 5143 155.00 PY88 0.85 2521 M 8.00 5A170K 6.25 955 1.00 6EW6 1.50 12J7GT 0.70 on request ECC33 3.50 EM4 9.00 8079 6.00 PY500A 1.95 275.00 Z7000 3.00 5A -180M 9.00 958A 1.00 6F1 2.00 12K5 D63 1.20 ECC35 3.50 EM80 0.70 8082 7.50 PY800 0.79 TD1-100A Z749 0.60 5A -206K 10.00 1.00 1299A 0.60 2.15 6F6G 2.00 12K7GT 0.60 DA4I 22.50 ECC81 1.15 E4181 0.70 8083 3.25 PY801 0.79 25.00 Z759 19.85 5AM8 1619 2.50 EM84 1.65 8091 7.50 TD03-10D 28000 3.00 5AN8 1.20 6F12 1.50 12K8 1.10 1625 3.00 DA42 17.50 ECC82 0.55 0113-1108A DA100 125.00 ECC82 Philips EM85 3.95 8096 3.00 35.00 2803U 18.95 5AR4 2.00 6F13 3.00 120701 0.50 1626 3.00 EM87 2.50 8098 5.50 47.50 TD03-10F ZA1000 12.50 5AU4 1.50 6F14 1.00 12SA7GT 1.00 2050W 4.50 DAF91 0.70 1.50 083-300 30.50 DAF96 0.65 ECC83 0.65 ENIO 8.00 8099 5.00 28.00 ZA1001 1.50 56.110M 10.00 6F17 2.75 12SG7 4.75 2050 2.75 0603-10 3.50 2.50 DC70 1.75 ECC83 Brimar/ EN32 13.50 8100 5.50 TD3-12 4.00 ZA1002 1.50 5B -254M 14.50 6F21 12547 1.00 3545 4.00 7.00 0E08-200 19.50 6F22 0.70 12SK7 1.00 DC90 1.20 Mullard 1.35 EN91 1.10 8136 TP25 1.50 ZC1040 8.00 56-255M 4313C 4.00 8137 145.00 6F23 0.60 12SJ7 0.60 DCX4-1000 ECC83 Philips EN92 4.50 5.50 TSP4 7.00 ZM1005 8.00 56-256M 9.00 4328D 9.00 0F40 85.00 6F24 1.25 12SN7GT 12.00 1.95 ESU572 25.00 8161 6.50 TT71 1.50 ZM1020 8.95 56-257M 9.00 1.85 5642 9.50 0.80EY81 8162 5.50 42P25 1.00 6F25 1.25 12S07GT 1.50 DCX4-5000 ECC84 0.50 EY51 TT15 34.95 ZM1021 6.00 58-258M 14.50 5651 2.50 00E03-12 6.50 1.25 1303 25.00 ECC85 0.60 1.50 8163 5.50 TY2-125A 60.00 ZM1023 7.95 5C22 69.00 6F25 3.20 5654 1.95 4.50 00E03-20 6F32 1.25 1307 3.20 DET16 28.50 ECC86 2.75 EY83 1.50 8190 TY4-400 70.00 ZM1041 14.00 5R4GB 2.80 5663 1.95 8195 6.50 27.00 6F33 17.00 13087 DET18 28.50 ECC88 0.85 EY84 5.95 TY7-6000A ZM1082 9.00 5R4GY 2.80 2.95 5670 3.25 EY86/87 0.50 8196 5.50 00E06-40 365.00 ZM1084 10.00 514 5.95 6FG5 1.95 13E1 115.00 5672 4.50 DET23 35.00 ECC91 2.00 39.50 DET24 39.00 ECC180 0.72 EY88 0.55 8204 5.50 TY8-.600W ZM1177 9.00 5U4G 1.95 6GH8A 0.80 14S7 1.00 5687 4.50 EY91 5.50 8223 4.50 00V02-6 16.50 385.00 ZM1202 55.00 5U4GB 2.50 6GK5 1.50 17EW8 0.95 5692 3.50 DET25 22.00 ECC189 0.78 00V03-105.50 DET29 ECC801S 3.50 EY500A 1.50 8224 2.00 TYS2/250 ZM1263 4.00 5V4G 1.25 6DK6 1.95 17JZ8 2.75 5696 2.75 8225 00V03-10 DF91 0.70 ECC803S 3.50 EY802 0.70 3.50 375.00 ZM1612 3.00 5Y3GT 1.95 6GV7 2.50 1803 1.80 5704 3.50 E1401 29.50 Mullard 9.50 6GW6 2.50 1963 DF92 0.60 ECC804 0.60 E235 0.75 U18-20 2.75 1 AC6 1.20 524GT 0.85 17.00 5718 6.15 2.75 E1402 29.50 00V03-20 1.10 19H4 0F96 0.65 ECC807 2.50 EZ40 U19 11.95 1 B3GT 1.95 6/3012 0.70 643N 23.95 5725 2.50 18.50 DF97 1.00 ECC2000 12.00 EZ41 2.75 E1501 14.00 U24 2.00 1622 10.00 6A/203K 9.00 646 1.35 19H5 33.50 5726 2.50 H4 DH63 1.20 ECF80 0.85 EZ80 0.75 3.50 00V03-208 U25 0.90 1624 14.95 6A8G 1.50 6H6GT 1.95 19426 9.00 5727 2.50 HL D6 4.00 32.00 DH77 0.90 ECF82 0.85 EZ81 0.75 U26 0.90 1B35A 29.50 6AB8 0.88 6.14 1.10 20A2 10.50 5749 2.50 0479 0.56 ECF86 1.70 EZ90 1.50 14 4.50 QQV06-40A U37 9.00 1C7 2.50 6AC7 2.00 6J4WA 3.15 2001 0.70 5750 1.85 04149 2.00 ECF200 1.85 Fô064 2 95 S4B 5.50 19.50 U41 6.95 1C5GT 2.50 6AF4A 2.50 6.15 2.50 201E6 3.50 5751 2.95 FW4/800 U14 1.50 DK91 0.90 ECF202 1.85 2.95 00V07-50 U50 2.00 105 2.50 6AF9 4.15 6.16 0.65 2011 0.95 5763 4.95 37 12.50 01(92 1.20 ECF801 0.85 G7 /371K 30.00 63.50 U82 3.00 1FDi 2.50 6AG5 1.50 6JB6A 3.95 20P1 0.55 5814A 3.25 78 0K96 2.50 ECF804 6.00 G55/1K 9.00 9.85 Q0Z03-20 U191 0.70 1G3GT 2.50 6AG7 1.95 6JE6C 4.95 20P3 0.60 5840 3.50 0135 2.50 ECF805 2.50 G180/2M 9.00 A2 0.85 42.50 U192 1.00 114 0.80 6AH6 1.50 6JS6C 4.95 20P4 1.95 5842 11.00 A2WA 1.50 0163 1.00 ECF806 10.25 G240/20 9.00 00Z06 -40A U193 0.65 116 1.50 6AJ4 2.00 6J7 4.15 20P5 1.15 5894 39.50 14.00 A3 2.50 45.25 DL70 2.50 ECH3 2.50 G400/1K U251 1.00 1 LA6 1.00 6AJ7 2.00 6K7G 0.70 21LU8 2.50 5899 4.50 0L73 ECH4 3.00 GC10B 17.50 B2 0.85 QS72/20 1.50 U801 0.75 1N5GT 2.50 6AK5 1.00 6K8Y 3.95 2461 39.50 5963 1.75 2.50 1.25 0191 1.50 ECH35 2.15 GC100 17.50 82WA OS75/40 3.00 UABC80 0.85 1S2 0.55 6AK6 2.00 6K06 5.50 25160T 1.75 5965 2.25 C2 2.50 DL92 0.95 ECH42 1.00 GC10/4817.50 OS92/10 5.00 UAF42 1.00 iT4 0.70 6AL5 0.80 611 2.50 25B06 1.75 6005 1.85 C3 1.50 4.85 DL93 1.10 ECH81 0.65 GC10/4E 17.50 0595/10 UBF80 0.80 1U5 1.00 6AM4 3.25 6119 3.95 29C1 19.50 6012 18.00 GC12/4B 17.50 D3 1.70 QS108/45 4.00 DL94 2.50 ECH83 0.78 UBC41 2.95 1 X28 1.40 6AM5 8.00 6L6GC 2.95 30C17 0.40 6021 3.65 ECH84 0.69 GD86W 6.00 M4 1.00 05150/15 8.95 UBC81 1.50 287 1.50 6AM6 1.50 6L6GCIGE)3.95 30018 1.48 6057 2.50 DL96 2.50 M5B 3.00 DLS10 13.50 ECH2000 1.50 GDT120M 5.00 05150/30 1.15 UBF89 0.60 2C21 1.00 6AN5 2.85 616GT 1.15 30F5 0.95 6059 3.75 ECL80 0.60 GEM 9.00 M6 1.75 0S150/45 7.00 UBL21 1.75 2C39A 23.50 6AN8A 2.65 6L7G 0.75 30FL1 1.00 6060 2.25 DLS16 10.00 RP43 2.50 OS1200 3.95 DM70 1.95 ECL82 0.65 GN4 6.00 UC92 1.20 2C39BA 39.50 6A05 1.50 61020 0.60 30F L2 1.35 6062 4.50 RP50 3.95 DM160 2.75 ECL83 2.50 GN10 15.00 QS1202 3.95 UCC84 0.70 2C40 37.00 6A08 0,85 61E6 4.50 30FL12 0.95 6063 2.00 4.00 51 2.50 0S1203 4.15 DY51 1.50 ECL84 0.74 GR10G UCC85 0.60 2C40A 55.00 6AR8 3.95 6106 4.95 30F113 1.10 6064 3.25 GR10J 4.00 41 2.50 OS1205 3.95 UCF80 1.00 6AS5 6N7 2.50 30F114 125 . ECL85 0.89 2C42 29.50 1.50 6067 1.95 DY86/87 0.65 BC80 050 DV802 0.72 ECL86 0.80 GS10C 16.50 051206 1.05 UCH21 1.20 2C51 0.75 6AS6 1.50 6N7GT 2.50 30L1 0.45 6072 4.20 GS1OH 1t.50 86 0.75 QS1207 0.90 EBOCC 9.95 ECL805 0.69 UCH41 1.20 2C53 32.00 6AS7G 4.50 6P15 1.50 30115 0.60 6080 4.75 88 0.75 17.00 EF37A GS12D 12.00 OS1208 0.90 UCH42 1.35 2CY5 1.50 6AT6 0.75 6P25 4.00 30117 0.60 6080WA 8.50 E80CF 2.00 92 3.50 QS1209 2.00 E80F 13.50 EF39 1.10 GT1C 14.00 UCH81 0.85 2D21 0.95 6AT8 1.75 6P28 2.00 30P4MR 1.00 6096 2.85 1 10 EF41 3.50 GT1CS/513.00 97 0S1210 1.50 UF85 1.20 2021W 2.50 6AU4 2.00 607 1.20 30P12 1.00 6132 10.00 E801 11.50 800 EF42 3.50 GTE175M 8.00 1.10 QS1211 1.50 UF41 1.15 2E26 7.95 6AU6 0.95 60707 1.20 30P18 0.80 6136 2.50 E81CC 3.15 900 1.25 12.00 EF50 2.50 GTR170W 1.00 QS1212 3.20 UF42 1.15 2J42 93.00 6AV6 0.75 6S4A 1.50 30P19 1.00 6146B 7.50 E811 CM 0.40 3.50 EF55 GU20 35.00 QS1213 5.00 UF80 0.80 2K25 24.95 6AW8A 2.50 657 1.10 30PL1 2.50 6157 2.50 E82CC 4.95 GXU1 13.50 C85 0.54 OS1215 2.10 E83CC 3.50 EF71 1.50 UF89 2.50 2K25 Raytheon 668G 1.50 6SA7GT 1.00 30PL13 0.60 6201 6.45 GXU3 24.00 C88 0.70 0S1218 5.00 6SC7 1.50 5.50 EF72 120. UL41 3.50 75.00 6BA6 0.95 30P114 1.75 6211 2.50 E83F C89 0.70 9.50 EF73 1.00 GXU505S 0U37 9.50 ULM 0.85 2K26 95.00 66A7 4.50 6SG7 1.20 31JS6A 5.50 6267 1.50 E86C C189 0.70 7.95 EF80 0.55 14.50 0V03-12 4.95 UU5 3.50 3A/1078 12.00 6BA8A 3.50 6547 1.20 33A/158M 6350 2.00 E88C 1.20 C805 0.70 E88CC 3.50 EF83 3.50 GV501 0V05-25 1.75 UU7 8.00 3A/108A 9.00 6BC8 1.00 6SJ7GT 1.20 19.50 6360 4.50 GY802 1.00 C806 0.80 0V06-20 29.50 E9OCC 7.95 EF85 0.50 UU8 9.00 3A/1098 11.00 6604 1.50 6SK7 0.80 35A5 4.50 6386 14.50 EF86 1.25 G230 1.00 E82 0.80 oV08-100 UV41 3.50 3A/110B 12.00 6606 1.00 6SK7GT 1.20 35160T 2.00 6545 8.50 E90F 7.95 F80 0.65 E91H 4.50 EF86 Special GZ31 1.00 145.00 UY85 0.70 3A/141K 11.50 6BE6 0.72 6SL7GT 0.85 35W4 0.70 6550A 8.00 GZ32 1.00 F82 0.60 E92CC 3.95 quality 2.50 0V2-250045.00 V235A/1K 3A/147J 7.50 6BF5 1.60 6SN7GT 0.95 35Z3 1.85 6870 11.50 GZ33 4.50 F84 0.65 E99F 6.99 EF89 0.85 0Y3-125 49.50 250.00 3A/167M 10.00 6BG6G 3.00 6507 0.80 384E7 4.50 688313 9.95 2.15 F86 1 20 0Y4-250 E1301 19.95 EF91 1.50 GZ34 65.00 V240C/2K 3A2 3.95 6646 1.95 6557 1.95 40(06 5.50 '6973 3.65 GZ37 4.50 F87 0.40 QV4-000 71.95 E180CC 6.50 EF92 2.15 225.00 3A3A 3.95 6648 1.50 6U4GT 1.75 47 6.00 7025 2.50 HAA91 1.00 F200 1.80 R10 4.00 E182CC 9.00 EF93 0.95 V241C/1K 3A4 1.10 6816 1.20 6U5G 1.50 5005 0.95 7027A 4.50 F201 1.80 R16 12.00 E180F 6,50 EF94 0.95 HABC80 0.90 195.00 3AL5 0.95 6BK4 4.00 6U8 0.85 50C 06G 1.15 7032 2.00 HBC90 F800 0.40 R17 1.50 E186F 8.50 EF95 1.00 0.75 V2464A/2K 3AT2 3.35 6BK7A 1.95 6Ú8A 1.50 50JY6 2.95 7059 2.50 HBC91 0.80 F801 1.35 R18 2.50 6V6GT 0.85 E188CC EF97 0.90 315.00 3AW2 3.35 68M8 0.58 52KU 2.00 7189 2.50 7.50 F802 0.60 R19 2.50 E280F 19.50 EF98 0.90 HF93 0.75 V339 3.50 362 3.00 6844 1.65 6X2N 1.00 61SPT 4.50 7189. 2.35 F805 1.25 R20 1.20 E283CC 10.00 EF183 0.65 HF93 1.50 VLS631 10.95 387 4.50 6BN6 1.85 6X4 1.50 7581 2.50 7193 7.50 F806 1 00 R1169 55.00 E288CC 13.50 EF184 0.65 HK90 1.05 VP48 4.50 3826 24.00 6BN7 4.50 6X5GT 0.55 75C1 2.50 7199 4.95 HL2K 3.50 F808 1 RG1-125 E810F 18.50 EF730 1.80 25 4.95 VP133 2.00 3828 12.00 68N8 2.35 6X5GTY 1.00 84 3.00 7247 2.00 1.50 RG1-240A14.50 E1148 1.00 EF731 3.50 HL23DD 4.00 4200 VR75/30 3.00 3C4 100 6805 0.75 6X8A 2.25 85A1 6.50 7360 8.95 7475 5.00 7551 5.45 WIREWOUND RESISTORS BASES ETC. ZENER DIODES 7558 9.45 7586 11.00 07G 0.15 CALLERS WELCOME PREFERRED VALUES BZX61 0.15 7587 26.95 4137.1K8 0.15 B7G Skirted 7591A 4.95 0.30 6V2 7V5 8V2 9V1 10V 11V 12V 13V 2K2 6K8 0.18 * ENTRANCE ON A227 7609 47.00 0.70 15V 16V 18V 20V 22V 24V 27V 30V 98G 7868 3.95 BOA 0.20 33V 36V 39V 47V 51V 56V 68V 75V 50 YDS SOUTH OF 4 Watt 10K 0.24 MEOPHAM GREEN 8012 15.00 B9A Skirted 8042 R47 4K7 0.18 0.30 BZY88 0.07 CAR PARKING 45.00 5K612K 0.19 8108 0.16 2V7 3V 3V3 3V6 3V9 4V3 4V7 5V1 AVAILABLE 8136 1.00 0138 0.50 5V6 6V2 6V8 7V5 8V2 9V1 10V 11V 8245 107.50 OPEN MONDAY TO FRIDAY 9a.m.-5.30p.m. 8298A 6.50 7 Watt 15K -22K 0.20 8 Pm DIL 0.14 12V 13V 15V 18V 20V 24V 27V 30V 8417 5.95 14 Pm DIL 0.15 24 HOUR ANSWERPHONE SERVICE 1R -10K 0.20 * * 9001 1.50 14 Pin DIL/0 ACCESS AND BARCLAYCARD ORDERS WELCOME 0.30 TRERMISTORS BATTERIES 9006 0.90 11 15K -22K 0.24 MANY OTHER ITEMS AVAILABLE 18042 Watt 16 Pin DIL 0.17 * * 10.00 VA1040 0.23 7V Power Mike 18045 10.00 18.1OK 0.26 OCTAL 0.35 VA1056S 0.23 batteries CANS 0.27 VA1104 0.70 TR 175 61.40 se UK ORDERS P&P 50p PLEASE ADD V.A.T. AT 15% 17 Watt 15K -22K 028 B9A PCB 0.15 VA8650 0.45 other prices on B5 0.75 VA1097 0.25 request EXPORT ORDERS WELCOME. CARRIAGE/POST AT COST 09G 0.38 CIRCLE 40 FOR FURTHER DETAILS. 79

www.americanradiohistory.com MICROBOX II A NEW MICRO CONCEPT Do you remember the days when people built their own computers? Well they are back with a vengeance. MICROBOX, the most advanced design ever offered as a build -it -yourself system, offers every facility imaginable to the home constructor. Just look at the amazing specification of this easy -to -build project: * MC68B09E 8 -/16 -bit microprocessor Floppy disc controller for two 5.25 -inch 40- or 80 -track * 64K main system ram + 128K alpha/graphic/simulated drives disc ram Battery backed realtime clock/calendar * Alpha display of 108 colums by 24 rows of 128 columns by Battery backed ram for storing system startup parameters 72 rows Two serial RS232 I/O ports. 50-19200 baud under software * True high -resolution graphics with 768 x 576 resolution control High-speed hardware vector generation using NEC 7220 Centronics compatible printer output port graphics controller. Point, line, rectangle, circle, arc and Parallel keyboard input port area fill facilities. Composite video and separate video/sync outputs * High-speed ram disc for fast data access Buffered expansion buss for user added enhancements * Up to 256K silicon disc eprom on plug-in eprom carrier Auto configuring 'FLEX' disc operating system boot monitor plus added utility and boot program in monitor * 8K system I/O support eprom commands * 12x9.5in. through hole plated main PCB; 3x4in. * Integral eprom programmer board. 'FLEX', which is supported by MICROBOX, is a well -proven, industry standard, disc operating system with a wealth of available software packages. Basic, Forth, Pascal, PL9 and C high-level languages as well as assemblers, word processors and electronic spreadsheet are currently available. Clever programming techniques have permitted the inclusion in the system monitor of a boot program that automatically loads and configures the operating system to the MICROBOX hardware requirements. The on -board ram and eprom discs are seen by the operating system as conventional disc drives. The ram disc has the capacity by a of a 40 -track single -density disc but with an access time 10 times that of a floppy disc. Eprom discs are supported way of plug-in eprom carrier which has provision for four 8, 16, 32 or 64K eproms into which can be programmed the operating system and any other often used programs by way of the built-in programmer. 'FLEX' supports up to four disc drives which in MICROBOX can each be allocated as floppy, ram or eprom types so providing, if required, a completely silicon configuration. A startup kit for the advanced MICROBOX system is available and consists of: Bare PCBs, 8K system support monitor, 'FLEX' system support disc, constructional notes, system documentation, component supplier list. PRICE: £95 + V.A.T. 'FLEX' disc operating system for MICROBOX, including editor and assembler: £75 + V.A.T. Send cheque to: 8 SKILLICORNE MEWS - QUEENS ROAD CHELTENHAM - GLOUCESTERSHIRE GL50 2NJ Micro Concepts Telephone: Cheltenham (0242) 510525

CIRCLE 30 FOR FURTHER DETAILS.

PAF4 EL ECTRÓVALLE "'%%:..:: :"..:...` The Wings Appeal o,,,, Fund helps to maintain Your Sr the RAF Association UPPLIERS Home for Disabled Give CIS SPECIALIST and Chronic Sick. Care is essential for they Out of a very wide range of types, we show some of the more popularly demanded ones. those who have served The full range currently stocked will be found 61/ Gave in our latest free A-2 price & products list. Please mention this journal when contacting 111111 their country and who are Electrovalue. in need. So please help by PUSH BUTTON Miniature giving all you can for an MINIATURE TOGGLES, 7000 Series Single and Double Pole Changeover 250V/2A, 120 V/5A. Single, double, Standard three and four pole configurations Latching and momentary emblem in WINGS WEEK inc. Centre Off/On and biased. in September or send a SLIDERS CK WAVECHANGE with adjustable Miniature & Standard. SP and DP in donation to show that stops. 1P/12 way, 2P/6W, 3P/4W, 1,2 or 3 positions. 4P/3W, 6P/2W. Many other types such as for timing you care. and other special applications. SWITCH KITS RA Shaft Assemblies up to 6 wafers.

To : Royal Air Forces Association, DP Mains switch. Screens; Spacers. Appeals Dept., (DS) Portland Rd. Malvern, Worcs. WR14 2TA.

I enclose a donation of BRITAINS LEADING QUALITY COMPONENT for the Wings Appeal Fund. SUPPLIERS -SEND FOR FREE 32 PAGE A -Z LIST Name ATTRACTIVE DISCOUNTS -FREE POSTAGE -600D SERVICE & DELIVERY Address 28 St. Jude's Road ELECTRO ALUS LTD Englefield Green WO Egham, Surrey ARD TW20 OHB `ÌI10.14eOrders Please tick if receipt required Tel: (07841 33603. Telex: 264475. North: 680 Burnage Lane, Phoned or information on RAFA Manchester (061-432 4945). EV Computing Shop, 700 Welcome Space donated by Burnage Lane, Manchester (061-431 48661. LAWÉS C ORLD CIRCLE 25 FOR FURTHER DETAILS.

80 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com NEW PRODUCTS

Communications84, HAND-HELD TERMINALS/ TESTERS A number of hand-held terminals facilities are offered by the 42B Birmingham may also be used as support and 42C terminals which have devices for communications 40-character displays, battery Business communications station with optional extension equipment. Such devices made operation with memory seemed to be the central theme of for a secretary which offerred by G. R. Electronics have been protection, signalling up to 9600 the exhibition held at the NEC in most of the same facilities and a used to test p.a.b.xs, baud and from 8K to 64K of ram. Birmingham. The integration of built-in intercom. multiplexers and other Different protocols are optional communications services usually If you believe that electronics processor -based systems for and the units can store diagnostic thought of as separate entities is communications, then the commissioning and installation routines for on -site testing and was emphasized by several exhibition has something to offer of such systems in the field. The can capture data for later exhibitors - the office computer to anyone interested in 14B, for example has a 14 -digit analysis. The company also terminal can also be a telex and electronics. This is certainly display, 92 -character memory offers an acoustic coupler and a teletex terminal and an autodial confirmed by the variety of the and RS232 and/or 20mA loop data recorder to complete a telephone as well as offering local products on show: anything from interfaces as standard. Options battery -operated system for the computing, word processing, a complete satellite receiver include a rechargeable battery collection and transmission of calendar and diary, calculator station to a single transistor and pack making it completely data. G. R. Electronics Ltd, and directory. One such device almost anything that can be independent of outside power Fairoak House, Church Road, launched by STC thought of that includes the sources, and RS422/432 Newport, Gwent NPT 7FJ. Telecommunications was prefixes tele or trans. interface for longer -cable signals. EWW 215 Executel, a multipurpose work Larger memories and more

from fumes or acid spillage. VOICE Under normal operating conditions there is no loss of FIBRE -OPTIC MODEM RECOGNITION water and so it is possible to High data rates, low A fibre splicing technique has dispense with normal vents transmission line costs and been incorporated into the SYSTEM though there is a small safety freedom from electromagnetic system and this is claimed to take The facility for someone to speak vent in case of accidental interference are three of the one third of the time needed to a computer and get it to obey over-changing. The Powersafe several benefits claimed for normally to make splices and yet has been appealing to the range includes 2V cells of 48 and Easydata's Raycom 2000 offers a high-fidelity connection imagination for some time and 110Ah capacities and a 6V block fibre -optic modem. A dual RS232 into each modem. The modems systems are available but still in of 80Ah. Another range, interface allows two separate are priced at £250 each and the process of development. Pye Powerstore, is available in 12 peripherals to have access to the saving is claimed from the use of Telecommunications proudly different sizes with capacities full duplex data channel single strand fibres, lower in cost demonstarted their system at ranging from 3 to 240Ah, in 2, 4, operating at 100Kbit/s over a than the equivalent twin strand or Comm 84 which they claim is 6 and 12V configurations. range of one km. Interconnection screened twisted pair cables both complex and reliable. It may Chloride Power Storage, PO Box of RS232 interface between normally used. Easdata Ltd, 7 be used remotely by two-way 5, Clifton Junction, Swinton, adjacent remote sites permits Charleton Rise, Welwyn, Herts radio or telephone and has been Manchester M27 2LR. cascading and allows the system AL6 9RP. found to work in up to 100dB EWW 216 to be extended for up to 10km. EWW 217 helicopter noise when test established that only one error resulted amongst 3200 recognitions.(Some of the techniques used in voice recognition systems were described by Tom Ivall in our last issue.) Pye Telecommunications Ltd, St. Andrews Road, Cambridge CB4 1DW. EWW 218

SOLID-STATE BATTERIES Batteries do not often hit the headlines but some new offerings from Chloride are interesting. Solid-state lead -acid batteries use highly absorbent, porous separators made from microscopically thin glass fibres, that take up the liquid electrolyte within their pores. Consequently, there is no free acid, and no risk of corrosion ELECTRONICS & WIRELESS WORLD JULY 1984 81

www.americanradiohistory.com s MARCONI SIGNAL s ' P. F. RALFE ELECTRONICS * COMPUTER PERIPHERALS * GENERATORS * 10 CHAPEL STREET, LONDON, NW1 TEL: 01-723 8753 *, w _ TFZOO2AIS (illustrated) 10kHz- y FLOPPY DRIVES 4 72MHz. AM/FM. £750 1.8818 8" DISC TF2002. As above but AM only. New Stock MARCONI TF1066B. AM/FM Generator. 10- 470MHz. 0.2uV-200mV output. FM Deviation up to After our recent sell-out of the DRE7100 FDDs, ±100kHz. we are pleased to offer another bargain package MARCONI TF99SA/5. AM/FM Generator. Narrow deviation model 995 covering 1.5-220MHz. £460. as follows: BRAND NEW American 'MFE Corp' TF2015. 10-520MHz. AM/FM. TF144H. AM 10kHz- model M-700 DOUBLE -SIDED 8'Disc Drives. 72MHz £265. to 1.6MBytes. Full MARCONI TF1004BI5. AM/FM Signal generator Massive storage capability up covering in three ranges 68-108, 118-185 and 450- IBM compatability. External power requirements PLEASE PHONE FOR CURRENT STOCK 470MHz. FM fixed deviations of 3.5 & 10kHz. AM are ±5V at 1.2A and +24V at 1.1 A. Full spares/ fixed 30%. £225 TEKTRONIX 453. Dual -trace 50MHz. back-up available U.K. (Elcomatic's). Current list TELEOUIPMENT D75 Dual -trace 50MHz is over £315. 'DOLBY' NOISE . * WEIGHTING FILTERS * portable £450 NOW LOWEST PRICE EVER Cat. No. 98A. Noise weighting filters for CCIR/ARM HEWLETT-PACKARD 1707A Dual -trace 75MHz. £180 - INCLUDING MANUAL signal-to-noise ratio measurements. As new units. INC CARRIAGE 8 INC VAT £40 each (+f1 p&p). TRIO CS1575 5MHz Dual -trace £250 " ** TEST EQUIPMENT ** BECKMAN TURNS COUNTER DIALS MEGAPHONES -'EAGLE' MV8SN. New. £40. ORE 4000 - SERIES DRIVES Miniature type (22mm diem.). Counting up to 15 BEAVER Model E57500 Automatic test equipment. turn "Helipots". Brand new with mounting instruc- MARCONI TF888 LCR Bridge Data Recording Equipment 5+5MB exchangeable disc drives tions. Only £2.50 each. MARCONI TF2604 Electronic Multi model 4000A. Brand new units for £275- inlcuding power unit MARCONI TF893A Power-Meter Meters and full technical manual. Audio 1000 WATT AUDIO AMPLIFIER' £85. - for inter factory/office communication comprising MARCONI TF2502 RF Power Meters. DC- DISK CARTRIDGES two racks containing ten 100W Grampian audio amplifi- * * 1GHz. 10w fsd f350. Surplus BASF 12 -Sector RK05 cartridges available ers and receiver for background music, microphone MARCONI TF2701 In -Situ Universal Com- quantity only remaining at £15 each. Car- and pre -amp controller. COMPLETE SYSTEM £550. .. small ponent Bridge 1250. riage each £1.50. HEWLETT-PACKARD 3450A Multi -Function Digital Multi -Meter. OPTICALISOIATORS ROHDE & SCHWARZ 'SDR' AM Signal Generator 0.3-1GHz. SPERRY UNIVAC M4000 opto-isolator units providing 2KV of TEKTRONIX 2901 Time -mark Generator. * SWITCHING POWER SUPPLIES * insulation between Modems and Terminals. 25 way 'D' connec- ROHDE & SCHWARZ Resonance Frequency Meter 470MHz-2.5GHz. The following DC power supplies are available now tors (RS232C Interface) in and out. Measures 9x5x7'. Corn - ROHDE á SCHWARZ Polyscop SWOB I). from stock in limited quantities. All fully tested and plate with handbook £25- pp£2. METROHM 500V Insulation Testers Transistorised f40 pp £1.50. guaranteed. BRUEL& KJAER Heterodyne Voltmeter 0.5-240MHz. 3.5V (á, 10 Amps £15 15V16A (110V IN) ... £20 ** STEPPER MOTORS ** AIRMEC Display Oscilloscope 279, 4-trace, 14x10" CRT £195. 5V (d 20 Amps £20 5V (a 40 Amps £30 5V (a- 60 19V 30 Amps Brand new stock of 'ASTROSYN' Type 20PM- RIKADENKI 3 -channel Chart Recorde , Model B-341. Amps £40 (ry £40 A055 stepper motors. 28V DC. 24 steps per rev. +15V, -12V & +5V (if 11A,4A and 40A £50 15 oz -in torque @ 100PPS. Body length 21/2", 8" WINCHESTER 8" SHUGART DRIVES ALL PRICES NOW INCLUDE VAT. CARRIAGE +£2 EACH. model 3100 Mini - diameter 2", shaft 1/4" diam x 41/4' UNITED PERIPHERALS spirally 8' Shugart type SA800 Floppy disc drives. threaded. Weight 16oz. Price disc drives (3 x 8' sealed plattens) cap- each £15 )p&p Small quantity available, single -sided up CENTRIFUGAL BLOWERS * able of over 19MBytes storage. External * 50p). Connections supplied. INC. VAT. power supply requirements are 24V a 3A to 800KBytes of storage. Power require- 'TORIN' Type U62B1. 230V Cap'Start (supplied), and 5V C 4A. Little used condition, ments, 5V e 1.3A. Little used, excellent very powerful (200W. 3,000rpm) centrifugal fans 'TELEVISION SERVICE KIT' believed OK but at the unbelievable price condition. PRICE £90- inclusive VAT and for large rack cooling or enclosure extraction appli- 20x12 We have managed to obtain a stock of Labgear T.V. Service of just £125 are sold without guarantee. carriage and copy of user -handbook. cations. Overall dimensions cros, outlet 6x4 equipment affording vast savings on new price. All items are Price inclusive of VAT and carriage and cros. BRAND NEW. Surplus stock. £15 each inc. sold In full working condition and guaranteed. copy of user -handbook. VAT, pp £1.50. LABGEAR CM5037/DB. UHFNHF PAL COLOUR BAR GEN- * TEKTRONIX * ERATORS Colour bars/cross-hatch/dot/blank raster/centre * SWEEPERS * FILE MANAGER SYSTEM MODEL * ROTRON INSTRUMENT location. £80. TaOMC 2003 System. 800-1500MHz £325 4907 Option 31 (Third disc drive). LABGEAR C916004 -PG. Monochrome UHF PATTERN GEN- FARS 1a0NC 3142600 with 500-900MHz plug-in £175 4051 Graphic System compatible. 000UNG ERATORS. Grey Scale/variable level cross -hatch 8 Dot pat- Supplied in fully tested excellent condi- ' KNIGHT KG -687 3-220MHz. £150 GPIB (IEEE 488-1975) compatible. terns. £40. tion, as follows: 'U UHF SIGNAL STRENGTH LABGEAR CMe016/SM. PLEASE NOTE. All the pre -owned equipment shown has been carefully 115V, 41 x41 x11/" £5. 230V same size METERS. Variable tuning Channels 25-65. Calibrated 'U tested in our workshop and recondi toned where necessary. It is sold in £5.50. 115V £4. 230V size, 4 -range moving-coilmeter, 30pV-3mV. Battery powered. 3x3x11 " 3" £45. first-class operational condition and most items carry a three months' brand new f8. Also small quantity 115V Please note all these prices INCLUDE VAT. Carriage + £2 guarantee. For our mail order customers we have a money -back scheme. 41/2" size, brand new £6. Postage each + each item and to all uipment at very reasonable rates. PLEASE 50p please. wwto RRep irss%VATTOcingg ALLPRICE S CIRCLE 55 FOR FURTHER DETAILS.

THE POWERFET (pantechnic) SPECIALISTS M & B RADIO (LEEDS)

THE NORTHS LEADING USED TEST-EQUIPMENT DEALER OEM USERS OSCILLOSCOPES. Fluke RMS Differential Voltmeter Tektronix 465 100MHZ Dual-Trace Delay 931 B 450.00 Pantechnic present the most adaptable high-powered amplifier ever. Sweep 900.00 Tektronix 7403N Main -Frame 750.00 HEWLETT-PACKARD. FET SYSTEM AMP Hewlett-Packard 182A Main-Frame550.00 4318 Power Meter 75 Hewlett-Packard 182C Main-Frame395.00 8052A Impulse Sound Level Meter200.00 Features: Broadband Sampling HIGH POWER up to 1.2kW (single ended) Hewlett-Packard 182A 4 Channel Plug -In 3406A and 1825A Time -Base and Delay Voltmeter 250.00 LOW VOLUME. 1/s Cubic foot inc. Heatsink Generator 1000.00 3480A Digital Voltmeter 135.00 VERSATILE. Delivers more than 1kW into 1/2 to 8 ohms Telequipment D83 50MHZ 1900A Pulse Generator 1925A Word OR2x600W into 2to811 Dual-Trace 450.00 Generator POA OR 4 x 300W into 2 to 412 (200W into 812) Marconi TF144H/4 Standard ANALYSERS Generator 150.00 ¡1 x 600W into 2 to 80 Hewlett-Packard Fourier Analyser 5451B Marconi 8010 Signal-Generator 100.00 OR j 1 x 300W into 2 to 412 with 7900A Disk-Drive and Low -Pass Radiometer SMG1 Stereo 1 x 150W into 4 to 812 Filters A to D Converters Etc 2,500.00 Generator 250.00 Etc., etc. RHODE -SCHWARZ Racal 9908 Counter Timer 1.1GHZ 500.00 Racal Universal Counter 9835 100.00 Having been closely involved in a wide variety SHF Signal -Generator 1.7 to 5.0 of OEM applications of their amp Wayne Kerr Logarithmic LCR Bridge boards. Pantechnic GHZ 850.00 became aware of numerous implementation problems often B500 ge left untackled by other amp board manufacturers. These problems specifically of VHF Signal -Generator 25 to 480MHZ Voltmeter size and thermal 185.00 Marconi Electronic efficiencybecame particularly aggravated at high powers and SLSV 125.00 considerably lengthened product development Signal -Generator 400 to 1200 MHZ TF2604 OM time. Sweep Marconi X -Y Displays TF 2212 100.00 By including in the board design it 225.00 thermal design totality of has been possible to SWU Marconi X -Y Displays TF2213/1 250.00 reduce the size of the electronics, and increase the efficiency of the transistor to UHF Signal -Generator 300 to 1,000 MHZ heatsink thermal circuit. The combined effect of this has been to dramatically SDR 145.00 HEWLETT-PACKARD PSU. increase the volumetric efficiency of the amplifier/heatsink assembly. The SYSTEM UHF Test Receivers 280 to 4600 MHZ 64338 Power Supply 0-36v 10A 195.00 Amp offers 1.2kW of power in a space of 180mm x 102mm x 77mm, excluding PSU USVD 175.00 6448B Power Supply 0-600v 1.5 195.00 and Fan. Selentomat Type USW V 225.00 6453A Power Supply O.15v 200A 275.00 The basis of this considerable advance is the PANTECH 74 Heat Exchanger, Stereodecoder Standard MSDC 225.00 Bradley Pulse Generator 176B 195.00 designed and manufactured by us. By eliminating the laminar air flow found in UHF Power Signal -Generator SCRD 275 to CCTV Video Cameras 2/3 Vidicon 75.00 conventional, extruded heatsinks, heat transfer to the environment is greatly 2750 MHZ .05 to 50 watts 400.00 Hewlett-Packard Time Interval Probes enhanced. Frequency Synthesiser XUA 30 HZ to 30 5363A 400 The flexibility of the 1.2kW amp stems from its division into 4 potentially separate MHZ 400.00 amplifiers of 300W each (downrateable with cost savings to 150W). These can be Transmission Measuring Line 75 to RECEIVERS paralleled, increasing current capability or seriesed (bridged in pairs) doubling 305MHZ 400.00 Eddystone 830/7 300Kcs to 30Mhz250.00 voltage capability. In consequence a large variety of amplifier/load strategies can be Ref lektometer 300 to 4200MHZ Racal RA17L Communications implemented ZDB 150.00 Receivers 300.00 As ever Pantechnic offer a full range of customising options including DC coupling, Unbalanced Standard Attenuator DPU Mercer 155 Electronic/Pneumatic ultra -high slew, etc. Contact Phil Rimmer on 01-361 8715 with your particular 0-1500 MHZ 50ohms 50.00 Gauging System 175.00 application problem. General Radio Capacitane Bridge P.S. Specs, as ever, are exemplary. MISCELLANEOUS 1617A 350.00 Avo RM215F/3 Ac Breakdown All Prices plus V.A.T. SAE Enquiries. A wide range of other amplifiers and other modules available. Tester 195.00 Avo Universal Bridge B150 MK2 95.00 WANTED Price and Delivery Advance X -Y Recorder HR96 65.00 Test Equipment, Receivers, Valves, Technical Enquiries Clare Multiple Earth Loop -Tester Components, Cable, PCB's Etc Top PANTECHNIC (Dept. WM) contact V144 75.00 Prices Paid. 132 HIGH ROAD Phil Rimmer on NEW SOUTHGATE, 01-381 8715 86 Bishopgate Street, LEEDS LS1 4BB. 0532-435649 LONDON NI11 PG CIRCLE 71 FOR FURTHER DETAILS. CIRCLE 67 FOR FURTHER DETAILS. 82 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com NEW PRODUCTS

of a back-up or archival tape can AWARD -WINNING overcome the vulnerability of TAPE STREAMER such a system. Datatech recognised a need for a Using standard 0.5in computer high-speed, high -capacity tape the 9800 tape streamer from desk -top tape store which was Thorn EMI Datatech may be comparatively low in cost, hence used as archival back-up for hard the development of the 9800. disc data and for transferring Compatible with any computer data from mini to mainframe system, the machine can computers. The 9800, while automatically lace the tape taking a standard reel of tape through the tape path and onto NUJ/Reed International dispute is amazingly small and the the take-up hub. The tape cannot This space is one result of the continuing dispute between combination of electronic, be put in the wrong way round, members of the National Union of Journalists and Reed mechanical, and software the machine will refuse to accept International subsidiaries Business Press International, design, combined with its it and signal an error. Internally, Butterworths, Hamlyn Books and IPC Magazines. ergonomic and aesthetic appeal all circuits are on plug-in cards has won for it a Design Council and there are self -diagnostic award. testing routines built in for fault The combination of hard disc findings. As a trump card Thorn and tape has become established EMI are hasty to point out that in main frame computer usage the system is compatible with the for some time. With many IBM PC and expect to find a large peripherals and minicomputers market for the device amongst however there has been a lot of micro users. Thorn EMI reliance on floppy or hard discs Datatech Ltd, The Mill, Wookey and a system failure can lead to Hole, Wells, Somerset BA5 1BB . the loss of valuable data. The use EWW 210 ADAPTIVE H.F. RADIO A radio system which improves station, taking into account the frequency management for existing h. f. propagation communication networks that conditions. have several transceivers is Sets of the transceivers DATA MULTIPLEXER announced by Racal Messenger. can have a different selection The VRM455OFS combines a of channel frequencies so that The Polynet local -area network host computer. Each multiplexer frequency -scanning receiver with networks can interlace or overlap from Logica has been enhanced can support up to eight a selective call transmitter. It while being secure from each by the introduction of a highly asynchronous channels which monitors up to ten pre -selected other. With a transmitting power flexible multiplexer, Polyline, to operate full duplex and support frequency channels, locks of 100 or 120W the synthesized interface computers with the communications over the automatically onto a received frequency transceivers operate network. The device may be used network for six signal lines. signal and decides if it is the between 1.6 and 30MHz. A small with any computer or peripheral Control of the network can be station being addressed before display indicates the selected device with an RS232 port to give undertaken by a Terminal warning the operator of an channel while an audible tone and it access to the network which Manager software package. The incoming message. This facility a flashing light warn the operator may also be used with high-speed Polynet/Polyline combination enables the optimum receiver of an incoming call. Racal computer -to -computer traffic. can be used to provide frequency to be selected, from Messenger Ltd, 5 Bennett Road, Polyline may be used to connect high-speed links between a the ten pre-programmed Reading, Berks RG 131I.J. normally incompatible number of otherwise channels, by the transmitter EWW 211 networked or stand-alone incompatible mini and devices. In addition the microcomputers from different multiplexer may be used to manufacturers. Logica VTS Ltd, WORD -PROCESSED TELETEX interface a terminal with external 84 Newman Street, An adaptor has been devised by providing teletex protocol, the services, such as electronic mail, London W1A 4SE. BT to provide the Merlin word system offers auto dialling, auto which may be available to the EWW 213 processor with the facility to answer for unattended operation, connect to teletex services. This, store and forward operation claims Merlin, the business allowing messages to be VOICE -OPERATED SWITCH machine branch of British transmitted at times when the Telecom, "provides the ability to charges are lower, automatic A microphone/switch respond in 8ms when used by exchange text information in a logging of all documents sent and combination that allows firemen with breathing aparatus, rapid error -free and cost effective received and a full character set hand -free operation of a or in fully enclosed anti -radiation manner". Using the de -facto ensuring that the copy is received transceiver has many uses. The or laboratory suits. It has also standard for electronic mail, the exactly as sent. Future Sonic Tornado voice -operated been tested successfully by RAF system will communicate with expansion will include switch is such a device and uses a search and rescue helicopter any other teletex terminals, of inter -working with telex and inertial throat microphone or crews and by free -fall any manufacture. The system packet switched services. Merlin noise cancelling microphone. parachutists. Sonic Helmets Ltd, has been developed by BT don't provide an address: all you The unit can be used with Communications Centre, research engineers and has need do is pick up a telephone, ear -hanger headsets, or be fitted 202 Bradford Road, undergone a series of dial 100 and ask for Freephone into breathing masks and Castle Bromwich, network -user trials prior to its Merlin. helmets. Field trials have Birmingham B36 9AA. public launch. As well as EWW 212 established that the sets will EWW 214 ELECTRONICS & WIRELESS WORLD JULY 1984 83

www.americanradiohistory.com Sowter Transformers With 42 years' experience in the design and manufacture of several hundred thousand transfcrmers 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 more. transformers, Direct Injection transformers for Gui- We can design for RECORDING QUALITY, STUDIO tars, Multi -Secondary output transformers, Bridging QUALITY, HI-FI 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 ANC 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 aid 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 STUDIOS, HI-FI 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, Eigland Phone: 0473 52794 & 0473 219390 : Telex: 987703G SOWTER

CIRCLE 47 FOR FURTHER DETAILS.

MIII 019 60510 016 BU III 1.40 164530 0.75 2N 3111 0.0 JAP11NE5E PCCOS 0.42 1ED 44119 0.09 807871 016 BU126 0.70 1B4540 0.75 24 3712 0.90 TRANSIST0R5 P C180 0.50 LED 371171 44532 0.09 010172 016 BÚ204 0.15 184560 0.70 15 3773 100 25413 0.30 PCE200 1.35 RED 005 AC101 0 77 BO ,5 0.21 811205 0.70 184800 .35 25 4031 0.25 254104 0.32 PC1B01 110 AC126 077 13012487 0.50 BU20B 0.15 1646105 .50 25 4036 8.25 254198 0.22 PC1802 0.57 LED 3mm AC127 015 80124 1.10 BU208A 0.10 184820 0.75 29 4031 0.25 254203 0.30 PC1606 115 YELLOW 0.10 AC128 0E5 BD128 0.35 BEMBO 1.20 786910 .80 284 4443 1.10 PCN200 1:00 254473 0.37 1E03mm AC128x 013 80131 0.25 8U316 045 1BA950 .N 21 4444 PCL81 0.54 016 15854 8.20 GREEN 0.10 ACMIA 80132 184990 21 5061 0.20 PL519 4.50 023 1.25 80406 815 .N 26011 0.32 AC112A 80135 104800 0.81 25 5294 0.30 ÌWMttOLTNJT 023 1.21 80401 0.75 250337 8.20 PCL82 0.83 180 Sean AC153A 80136 80408 106940 .85 2N 5296 0.30 PCL64 023 0.0 1N 258405 0.22 0.50 REO 0.44 ACI76 a 10 80131 BU500 110 1047710 6106 PCL85 0.20 /10 2N 0.4/ 2SC460 021 0.55 6C1/6A O 20 80138 /21 BU516 010 11141482 .N 287 6101 0.40 250495 044 PCL86 0.55 1ED5mm AC181 01S 80139 1.21 61126 O0 1061002 N 2N 6109 0.40 PCL805 EL LOW 010 25C733 0.40 0.5$ AC1818 017 80140 6.21 85727 O0 7062003 1.0 P11200 0.45 35 128 005 2501161 110 AC180 Al? 80144 86133 ON 1062020 1.40 P136 LED 5mm 9O 1.44 0.0 36 143 0,65 25C1172T GREEN 010 ACIBOA 0.23 B0150 0 30 BY164 022 1042030 140 71.504 0.44 LES 2SC1119 0.21 (WILAY ACY16 0.48 BD157 0 38 61116 055 1062527 0.N P 1508 144 N 914 002 2001306 144 ACY19 0.4! 80156 036 85179 035 1062530 010 P Y81 0.70 N 4001 0.04 2001307 1.00 AD142 00 60166 0 30 81182 032 1062532 .75 PY88 0.48 N 4002 0.04 2501510 0.25 40149 045 001:5 0 30 BY184 9.12 IOA2540 _70 P85004 4003 2501969 030 1.60 A0161 022 BDI7: 0 30 66187 0.32 7042560 0.70 N 0.04 BRIDGE N 4004 1002029 1.44 AD162 012 00119 032 BY 196 011 1042593 0.0 0.0 0601018600 N 4005 2502078 1.44 A1724 025 BD181 0.45 61206 011 0.44 141506 0.16 N 4006 2501121/ 20 48125 033 136201 012 1062690 104 2E11E85 111100V 0.18 025 132201 0.10 1502952 027 41126 025 80202 0.3/ 136123 0.11 11829 015 N 4001 0.0 400MX 1602000 0.19 N 4148 0.02 250234 037 Ranga 61121 0.25 80203 042 BX%10 015 IIP29A .22 62188 1414006 0.21 N 5400 0.N 254135 4.0 ro 0139 0.22 80204 0.42 IIP29C 0.25 207 3990 060 14760V 8.23 N 5401 0.10 083112 1.0 73W A1239 0.22 60122 031 CÁ210 0.44 TIP30 0.10 211115 147806 0.21 N 5101 0.10 TÁ7205 1.0 Bange A1112 070 80225 031 043006 0.25 1IP31A 0.24 BZx61 1A11009 0.35 N 5403 0.11 UPC575 1.0 21/' to 3960120 AL113 0.44 80232 831 C63069 144 10832 0.24 2472009 0.34 N 5404 0.11 45215 1.00 80231 0.21 CA3140 0.44 710326 0.24 247409 0.42 ASZ17 1.0 0238 0.24 01060 0.23 11833 000 N 5405 0.12 2476009 4.54 N 5406 0.13 130433 021 11834 0.50 ICS 24,8009 0.50 N 5407 013 MEM011ES AUI10 110 80437 0.21 MC1321 8.70 118410 0.22 5005ET5 3Á120V 0.0 N 5408 0.13 2114 2.03 46102 80 80535 0.30 17.11500 100 IIP41C 0.25 8077 0.44 3Á140V 0.0 2116 3.0 46106 170 BD536 030 022501 110 TIP42A 14 711 3476009 0.71 0.22 0.0 2532 4.N 60531 040 8622955 0.05 TIP42C 16 0.0 647206 1.0 0.25 pm 2732 4.10 84145 0.10 60538 0.40 MJ300 1.15 11847 901760E 18 0.12 6474004 5.44 0.40 pm e64 7.44 BA148 010 BDx32 110 6143001 1.15 71848 0.40 0604191085 20 0.74 25A7,0V pin 6 0.75 BA154 0.0 BOBOS 044 44JE296 0.30 111349 0.40 7803 0.35 2284 0.16 I.50 6116 6.N 84157 012 68180 016 'AJENA 1.31 1113110 041 7812 055 2487 088 MJE340 1.06324 0.30 BB101 013 81181 011 8.25 118112 0.54 7815 0.35 0.20 28 en 31380 0.50 ELE0TROLttIC 88103 016 81183 MJ[350 11.85 1IP115 1018 0.35 0.20 0.45 40 pA 0.25 31381 10 470001.160 661050 018 B1184 020 1417520 0.30 58117 0.56 1004 0.35 15109 0.10.30 CAN 8.20 selechny trima lalige sil modules for 882058 024 81185 oso M,E2955. 0 N 98120 0.43 7905 0.35 31723 BCI07 001 B119A 0.44 11P121 0.32 micri music preampllhcabon 0.46 7912 0.40 0n015 80108 007 61195 006 7887112 441600 LM141 uId tone. chime generators etc 0.0 0447 041 7915 0.40 BC109 0 07 58125 DX81 0.53 1M141 01796 00 0697 0 04 011 7918 Cnher leal tires sil Series 8000 otro lude 0.40 75802 8.15 Met 0.15 BCI15 010 81799 044 0491 0 04 11P126 0.0 7924 0 40 313900 0.25 70411101 tompre,mon lu g r I us BC118 011 8120 016 D420(' 0 01 118127 5.0 00132 0.40 NE555 0.15 80140 019 81251 0.11 04202 0 07 1882955 .31 78105 0.28 ECC83 043 101PLE85 slundard un all p ,enngrldiers NE556 0.40 80141 019 B 258 Ila 0028 100 11P3054 .3e 18212 021 ECC83 040 LP1195 Squelrh s6.slem Ira rnu-sic preernps BC142 019 6 259 0.11 0029 080 1103055 .34 78115 0.21 ECC85 0.44 61855, 000510, 2.25 for tupe dos,- noue reduction

1 7408 350 0.30 BC143 019 B 336 023 0035 0 11061 0.15 0.21 ECSn 8.48 No -In, use 74124 BY'x551 signal switch "dirks n/ BC141 005 61337 020 0045 O N 71590 0.35 ECN84 0.52 N'hitelel''.5 new Series 9111111 range of 0./5 a unique /sill up dowel .IsIent BCI4B 005 B 330 020 0071 030 71091 074 ECt80 0.57 600 1ou1111 breado-ast equipment gives LM3091 1.0 _-Inge BC149 0.05 B 362 030 OCI1 050 ECL82 0.25 851155707B Snphesln riled nullchil8 26 .20 0513116 2.28 u all the power ymo Want al 0C157 005 81422 0.21 00200 IDO 204 00084 0.57 600 0.30 777741411 Nvot with ea,NII, progre'"? 1N 1905 20 LM3111 1.02 extremely compeldive paces, and BC159 0.19 OCIOS 0.57 BY> 551 0.0 81058 OCP77 100 151323Á 4.20 ntatril 88459 0.19 26 2906 0.14 ECL 86 6.49 00 032 Includes several sophlsticaled BC182 0.0 06812 1.00 108123 012 ' tloin/rnnu s'vsrtmu nluc he 88829 020 (180 011 BYx10 facilities not normally offered as BC182L 006 06860 1.44 7887GAC 5.70 coscaded to promde lar u vers 81984 020 2N 2926 _0 E185 0.34 500 0.29 BC183 0.0 06861 1.44 18870560 5.21 standard 81985 25 3019 n E189 0.45 BY4107 large number of input surines. BCIB3L 0.0 0.20 18GU1C 1.0 210 3063 0.18 E1183 500 O.J1 1'ou can choose Iron a Inge of hick PrìnriN fire? fient sen ed BC184 0.0 81x8/ 0.15 620088 0.44 79GUIC 0.40 - Anne. 26 3054 .35 2.15 886101 technology, high 801841. /.N B1980 015 020106 t.0 F1164 0.53 reliability ampllflers Itllltll411111qD10uu -rrlixed source swi7chn?g. 2N 3055 32 195GAC 6.70 80112 0.0 B1Y50 014 EL34 1.0 80 0.38 " 7741774 Irom 20 watts to 51101 walls 26 30555 0.31 870,717 Fur performance, versabinv and 6C2121 0.11 81951 0.14 SÁ5560 1.11 EY86 0.31 The 20 watt (1111014r D. a compacI 2N 3440 .58 60 0.80 economy, the message os loud and E80213 8.11 61052 0.44 SA5570 1.11 EY87 0.38 low cost stand alone unit with main 81Y56 0.25 26 3442 .85 PC91 1.0 clear Series 80011 Irom Whllelev 802131 4.111 551600344 110 desirable leamres includisigg e BC214 0.0 65157 015 98164834 8.40 Electronics. the Drilish company wnh 807141 0.0 81X64 0.25 9170234 1e Please add 50p P&P and VAT at 15%. Govt. Colleges, etc. Integral elecirel ndcrophone. The over 50 years of sound experience. BC231 0.17 8810 014 mainframe .11npllher range of 60. 1211 58703380 1.54 orders accepted Send for derailed literature lirday. 80238 4.77 BSxl9 0.15 55161105 1.70 Quotations given for Large Quantities and 2511 walls allows you to march BC30 114 85x20 015 9476115 9.70 sir specihc retanremeias by BC301 0.14 15820 1216 5176116 1.44 Please allow 7 days for delivery 80302 0.10 85826 0.16 0676211 ON All brand-new Components. All valves are new and boxed 0.11 BS629 111 Ring for items not listed. We stock 3,000 items 710327 7.0 81616 0.10 128000 0.52 BC382 0.0 8110 7.44 160060 042 Whiteley' 60337 0.0 BT10 0.0 146831 200 172 AUDIO SYSTEMS 60318 1.0 BT116 0.00 14G4443 0.16 G RAN BC551 4.0 81119 1.00 1604444 0.16 DATA LTD. Over half a century of sound experience 80532 1.50 131720 1.00 71871550 0.10 9 & 12 THE BROADWAY, PRESTON ROAD \SLiedrt In _ ..diel T, wphlnle 119,2.71'21;1.2 'le lex 11 026 BCY33 1.54 BU104 1.44 3661205 0.45 WEMBLEY, MIDDLESEX, ENGLAND BCY34 1.44 887106 ee0 186395 11.60 i 8041 120 8U100 1.114 196396 0.0 Telephone: 01-904 2093 & 9041115/6 60156 1.16 BunD 1.11 169520 0.75 Telex: 932885 Sunmit CIRCLE 13 FOR FURTHER DETAILS. CIRCLE 73 FOR FURTHER DETAILS. 84 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com NEW PRODUCTS

PCB TOOLS SERIAL COMMUNICATIONS Repair and reworking of printed circuit boards is claimed to be Much more than a dumb buffer is simple and economical with the serial communications card miniature power tools from which includes an on -board Foredom. Based on a motor unit M68000 processor running at and a flexible shaft drive the tools 8MHz. The SCC-01 can also have can be used to clean, alter and up to 32Kbytes of local program modify boards with a variety of stored in eprom or fusible -link attachments including buffs, prom, and 128Kbytes of dynamic brushes, sanding discs, abrasive ram. The unit communicates wheels, ball cutters, burrs, drills with a host processor through a and saws. Power is supplied by a VME bus by means of interrupt 0.lhp electric motor through the generation and 4Kbytes of dual flexible shaft at speeds from zero port ram. There are twelve to 14 krev/min. Speed may be u. a. r. is on the card, eight of varied by a foot control. Hirsh which are used for several Jacobson Merchandising Co. peripherals while the other four Ltd, 91 Marylebone High Street, are available for monitoring in London W 1. receive -only mode. The u.a.r.ts have programmable data rate EWW 219 generation and can detect breaks in a data stream. Four of the u. a. r. is have been designated as fast channel devices and, if selected all four can be operated in synchronization at up to 1Mbaud. Plug-in daughter boards provide conversion from t.t.l. level to RS232, RS422 or REEL TAPE RECORDERS 20mA level. The double Eurocard with the system on board has of 40 Analogue sound recorders Tascam see the use the been designed for use in designed for audio and video series to be in smaller studios, industrial environments and can dubbing, production work have been video post -production, operate within a temperature education. In manufactured by Tascam. The and in training and range of 0 to 70°C, and a relative the 40 series comprises three contrast they have taken humidity of up to 9%. All to upgrade the two different machines; the 42 with opportunity boards undergo a 48h two tracks for stereo and 7.5 or series 50 machines which they temperature/power cycling PROM REMOVER 15 in/s tape speed; the 44 with claim to be in the full professional programme. Manufactured by four tracks and the same two league. The 50 series now Wormald Data Systems, they New from Sweden are these i.c. speeds, and the 48 with eight includes the -10dBv phono may be obtained from Unit -C removers which can pluck a rom tracks on 0.5in tape and a single outputs and balanced +4dB Ltd, Dominion Way West, from its socket without damage speed of 15in/s. The machines balanced connections. The Broadwater, Worthing, West to the p.c.b. or to the circuit. For can all use the SMPTE time two -track 52 now has Sussex. to once the model numbers seem codes and may be locked on to front -mounted input and output EWW 222 make some sense; 2428 is for 24 time code synchronizers, and level controls with pre and post and 28-pin devices while 3640 is search and cue facilities are fader switching. The 50 series for 36 and 40 pins. Called available using the real-time also offers remote control FORTH EPROM Prom -outs they are available counters. The machines use facilities for the transport and for from Welwyn Tool Co. Ltd, 4 ceramic capstans to improve selection of channels. All PROGRAMMER Black Fan Road, Welwyn Garden performance and minimize wear. switching and preset controls are A single Eurocard accommodates City, Herts AL71EH. Three heads are used and flux available on the front panel. a circuit which can be used to EWW 220 levels of 250nWb/m or 320 may Model 58 offers eight tracks on program, read, verify, and copy be accommodated. NAB or 0.5intape. Boththe52and58 eproms. The TDS960 card is IEC/DIN equalization may be machines have their bias and used in conjunction with the used. The tape transport is equalization set for use with high single -board TDS 900 Forth heavy-duty, servo controlled output/low noise tapes such as computer and the programmer with claimed low wow and flutter Scotch 226 or Ampex 456, and software is provided on rom as figures. Optional plug -ins may be easily adjusted to the well as a listing. The Forth listing provide synchronization with correct parameters for such enables the user to add any automated broadcast equipment tapes. If a particular low -bias particular programming needs as or remote transport control. tape is to be used, a small may be required. The Each machine has both XLR modification is needed to adjust programmer card is the same (balanced 600Q connections with the preset's range. Distributor: cost as the TDS 900 c.mos a recording -level headroom of Harman (Audio) UK Ltd, computer; both are £ 179.95. +28dBm) and phono Professional Products, Triangle Digital Services Ltd, (unbalanced 10kQ) connections. Mill Street, 100A Wood Street, Internal switching enables a Slough, Bucks SL2 5DD. London E17 311X. +8dBm operating level. EWW221 EWW 223

ELECTRONICS & WIRELESS WORLD JULY 1984 85

www.americanradiohistory.com LINSLEY-HOOD CASSETTE RECORDER CIRCUITS HIGH QUALITY REPLACEMENT 11.11.1.1.1.:SLEY-HOOD for very high quality low Complete record and replay circuits HEADS 1/300 noise stereo cassette recorder. Circuits are optimised for our CASSETTE SERIES AMPLIFIERS HS16 Super Quality Sendust Alloy Head. Switched bias and equalisation to cater for chrome and tarit tapes. Very easy to assemble on plug-in PCBs. Complete with full instructions. Complete Stereo Record/Play Kit £25.20 l .. VU Meters to suit £2.30 each Reprints of original Articles 75p. No VAT.

Do your tapes lack treble? A worn head could be the problem. STUART TAPE RECORDER CIRCUITS Fitting one of our replacement heads could restore performance Complete stereo record, replay and bias system for reel-to- to better than newl Standard mountings make fitting easy and spot-on. We are reel recorders. These circuits will give studio quality with e our TC1 Test Cassette helps you set the azimuth good tape deck. Separate sections for record and replay give the actual importers which means you get the benefit of lower and see! optimum performance and allow a third head monitoring sys- prices for prime parts. Compare us with other suppliers are suitable tem to be used where the deck has this fitted. Standard 250mV The following is a list of our most popular heads, all for use on Dolby machines and are ex -stock. 35 Watt Complete Kit. MosFet 0/P £79.50 input and output levels. Full details are in our lists. 45 Watt Complete Kit. MosFet 0/P .. £83.50 Reprint of Original Articles £1.30. No VAT. HC20 Permalloy Stereo Head. This is the standard head fitted as Reprints of Original Articles from 'Hi-Fi News' f1 no VAT. original equipment on most decks £5.11 HM90 High Beta Permalloy Head. A hard-wearing, higher per- formance head with metal capability £8.06 ALPS FF317U FM FRONT END HS16 Sendust Alloy Super Head. the best head we can find Beautiful, precision made High Quality variable capacitor Longer life than Permalloy, higher output than Ferrite, fantastic LINSLEY-HOOD 100 -WATT MOSFET tuned FM Front End with Dual -gate MosFet. The tuning capaci- frequency response £9.91 has 2 -AM Gangs and built in 3:1 reduction gear. tor also 140.561 4 -Track Heed for auto-reverse or quadrophonic use. Full POWER AMPLIFIER full FM range of 87 to 109MHz. Supply needed is 12V at Covers specification record and playback heed E9.73 The very latest amplifier design, published in' Wireless World' only 30mA Max. Inputs are provided for AGC and AFC signals. renowned Linsley -Hood. This may now be taken as offer from another sup- Please consult our list for technical data on these and other by the John These have recently been on special Special Purpose Heads. the standard by which the rest are judged! Our kit, approved by plier £4 plus VAT. OUR PRICE IS ONLY £3.99 INCLUDING at Record/Play head. the designer, has massive heat sinks and power supply and VAT AND POSTAGE! Circuit if required 35p. MA481 Latest version Double Mono (2/2) includes all components needed to build. Case size 412mm Replaces R484 £8.90 wide, 254mm deep and 145mm high. Automatic switched SM106 Standard Mounting 2/2 Erase head. Compatible with is included as standard. Cost of all parts is speaker protection COMPLETE STEREO TUNER MODULE above or H0551 4 Track head. £5.90 over E120. Our complete stereo kit price £105.50. on PCB Three band LW/MW/FM Stereo Tuner fully assembled Non Standard Mounting 2/2 Erase head £4.25 Ferrite rod aerial and band switch ME151 165 x 85mm. Supplied with Erase Head. Semi double gap, high effi- fully wired. Facility provided to drive tuning meter and stereo H524 Standard £1.50 LED. Only needs 12v DC supply. FM sensitivity. 2.5uV. Price ciency HART TRIPLE -PURPOSE TEST only £7.99 Inc. VAT and post. H561 Metal Tape Erase Head. Full double gap £4.90 CASSETTE TC1 RS7106 Audio Visual Head. (1/2 plus top 1 /4).. £10.82 One inexpensive test cassette enables you to set up VU level. HIGH-SPEED DIGITAL CASSETTE RECORDER head tape speed. Invaluable when fitting new azimuth and A really super buy for the computer enthusiast. These decks, heads. Only E4.66 plus VAT and 50p postage. made by Burroughs, use a capstanless cassette mechanism to record and replay data at 10 and 30 inches per second. The read Head De-magnetiser. Handy size mains operated unit alter write head uses an NRZ system with separate tracks for Tape 'STEREO AMPLIFIER MODULE' prevents build up of residual head magnetisation causing noise clock and data. power supplies of 5v, -12v and +12v are E4.54. Ready built and tested quality power amplifier module complete on playback required. Front panel is 137mm square and the unit is 200mm and ready to use. Mains input 220/240v with power to spare for Curved Pole Type for inaccessible heads E4 85 deep including rear connector. Offered in good ex -equipment tuner and tape deck. Size 190 x 110 x 65mm. condition at a fraction of origini cost, ONLY C44.50 inc. VAT and postage. Data inc. circuits and layouts of PCBs £3.50. TUNER AND PRE -AMP MODULE Please add part cost of post, packing and insurance as follows: Matching unit to above. Contains Long, medium and shortwave inputs for AM tuner. Stereo FM tuner and pre -amp with switched COMPONENTS INLAND OVERSEAS flywheel drive and cord Orders up to E10 - 50p Please send sufficient to cover tuners, tape and pickup. Complete with We now list a wide range of individual components many of which Orders £10 to £49 E1 Size 400 x 220 x 63mm. are not available elsewhere. Send for your copy of our latest list - Surface or Air Post as reouired. assembly. Orders over £50 - E1.50 Special offer for both items only £16.90. which also gives further information on our Kits. ALL PRICES EXCLUDE VAT UNLESS STATED very welcome but please note that we 1, always Personal callers are !aQNMp5H1aE are closed all day Saturday (0691) 652894 1íNylpSNpo át Sy,Oypf 0 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 1M2 - 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. Thurlby ElectronicsSt.lves LtdCombs. 0M358 with two BNC lliTh.ribyip NewRoad , , cables £197.80 designed and built in Britain PE17 4 BG Tel: (0480) 63570 (inc P & P and VAT) CIRCLE31 FOR FURTHER DETAILS.

VIDEO TERMINAL BOARD ASIBIN ' ERS Quick, neat and easy!

It's so easy and tidy with the Easibind binder to file your copies away. Each binder is designed X * 80 characters 24 lines * to hold six issues and is attractively bound and blocked with the WIRELESS WORLD logo. Price U.K. £4.30 including postage, packing and V.A.T. Requires ASCII encoded keyboard and monitor to Overseas orders add 35p per binder. Nat. Giro No. 5157552. make fully configurable intelligent terminal. Uses 6802 Please allow 3/4 weeks for fulfilment of order. and character Payment by ACCESS/BARCLAYCARONISA. Send coupon below detailing credit card no. and micro and 6845 controller. Program signature. generator (7 X 9 matrix with descenders) in two 2716 Why not place your order now? Send the completed coupon below with remittance payable to: EPROMs. Full scrolling at 9600 baud with 8 switch Easibind, 42 Heston Square, London N1 6NS selectable rates. RS232 interface. ------liiil/ Order Form WIRELESS WORLD Bare board with 2 EPROMS and program listing - e enclose P.O./cheque value for binders t plus VAT. Send for details or CWO to: Years required £48 IBLOCK LETTERS PLEASE Name A M Electronics aAddress Wood Farm, Leiston, Suffolk IP16 4HT AM No. 735718 ELECTRONICS Tel: 0728 831131 Date Registration ©' - Man» - fííí1 - !íííl - CIRCLE 17 FOR FURTHER DE'T'AILS. 86 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com NEW PRODUCTS

Amstrad sounds off

On paper, Amstrad's CPC464 parallel i/o device. Screen who promote products using additions of dissimilar equipment microcomputer scheduled for memory is 16K. There is a predictions made by design to the network can be June introduction seems an ideal Centronics parallel printer output engineers, Amstrad would be accommodated by upgrades to all rounder - cheap, fast, 64K and an expansion port but risking too much to promise all the disc -held software. ram, high -resolution graphics regr'ttably the connectors are this but to present only part of it, Netway has multiple and with a colour or monochrome the edge of the p.c.b. and not especially when one takes into distributed microprocessors monitor included in the price. Of gold plated. account Britain's current within its hardware structure interest to we of technical bent The keyboard and its separate aggressive home microcomputer which has been optimised for there's the promise of even more, numeric and cursor-control pad market. Delays in the communications. It uses a including full access to the 4MHz is full size and uses familiar introduction date could be dynamic multi -tasking, Z80 processor, CP/M, Basic keytops but has a membrane devastating. The company multi -programming operating interrupt operations, assemblers switch matrix underneath to keep expects to produce 200 000 units system called NCOS. The central and disassemblers. costs down. Matsushita this year and sell them mainly unit of the system, Netway 200 With built in cassette recorder membrane technology is used, through Dixons, Boots, Comet with its 800Kbyte disc drive can and direct -drive green -tube conductive rubber against and Rumbelows. Amstrad be configured, on-line if monitor the basic version costs gold-plated p.c.b. contact areas Consumer Electronics plc, necessary, to support local or £229, and for a further £ 100 one so, theoretically at least, it Brentwood House, 169 Kings remote microcomputers and can have the colour -monitor should last a long time. Road, Brentwood, Essex CM14 other devices using the protocols version. Monitors will not be Considering that the average 4GF. of the host mainframe. Netway available separately. Disc-based consumer is now wary of 200s works in conjunction with monochrome and colour -monitor microcomputer manufacturers EWW 208 Netway 100s which interface versions will cost £429 and £529 individual devices into the respectively including CP/M and network, and with the Netway Logo (a US import language for 150 which provides remote educational programs). The PROCESSOR TO connection to Netway local Japanese Hitachi format (IBM COMMUNICATIONS networks. The full capacity of the data format) 3in disc drives EASE NETWORKING system is a large multi -node should be available separately for network incorporating up to 254 around £200. There is as yet no Instead of employing separate these functions into a single unit. Netway processors each having a CP/M compatible software on 3in communications devices, The system can be configured to combination of up to 32 disc. protocol converters, data connect virtually any type of workstations and host ports, At these prices one couldn't concentrators, multiplexers, microcomputer, terminal, though the system can start by buy the parts and build one cluster controllers, packet wordprocessor, and local -area serving just one or a few cheaper. Assuming no hidden processors, or nodal processors, network with host computers workstations. Scicon Ltd, 49 snags, the only remaining the Netway communications from IBM, ICL, DEC and Berners Street, London W1P 4AQ. question is reliability. Bill Poel, system from Scicon combines all Burroughs. Subsequent EWW 209 general manager of Amstrad's new software company Amsoft and co-founder of Ambit International (recently sold to Bulgin), told E&WW"Amstrad has increased reliability of its products over the years and will continue doing so. We expect a 2 or 3% return rate - the biggest problem will probably be with people who haven't read the instructions properly and those who spill tea in the cassette mechanism" . Main i.cs used are the 6845 c.r.t. controller for 80 -column text and up to 640 by 200 picture elements, an 8912 three -channel sound generator and an 8255 ELECTRONICS & WIRELESS WORLD JULY 1984 87

www.americanradiohistory.com 1000 s -d ¶s)Ì1aifts1ÍÑ FOR CALLS D J' THE ALADDIN'S'CAVE OF COMPUTER AND ELECTRONIC EQUIPMENT HARD DISK DRIVES NOT LINE DATA RASE COMPUTER 'CAB' Fully refurbished DIABLO/DRE series 30 2.5 Mb disk drives. All in one quality computer DEC RKOS, NOVA, TEXAS compatible. cabinet with integral switched Front load. Free stand or rack mount £550.00 mode PSU, Mains filtering, and twin fan cooling. Exchangeable type (via lid removal) £295.00 Originally made for the famous DEC PDP8 computer me3029 PSU unit for 2 drives £125.00 THE ISTEFREE OF CHARGE dial up data base. ORIGINAL system costing thousands of pounds. Made to run 24 DIABLO/DRE 44-4000A/ß 5+5 ex stock front £995.00 1000's of stock items and one off bargains. hours per day the PSU is fully screened and will deliver a 1000's of spares for S30, 4000, 3200. HAWK ex stock. NOW baud, full duplex CCITT tones, 8 bit ON LINE - 300 +5v DC at 17 amps, +15v DC at 1 amp and -15v in repair, refurbishing service. massive Plus house word, no parity. unit is fully enclosed with Call for details or quotation. DC at 5 amps. The complete 01-679 1888 removable top lid, filtering, trip switch, 'Power' and 'Run' EX STOCK INTEGRATED CIRCUITS LEDs mounted on Ali front panel, rear cable entries, etc. MAINS FILTERS etc. Units are in good but used condition - supplied for D8085AH-2 D8086 D8257-5 Cure these unnerving hang ups and data gulches caused 240v operation complete with full circuit and tech. man, for D8202 D8271 AM2764-3DC by mains finie rfe re rice Give your system that professional finish only 74LS86 74LS112 74LS313 SD5A As recommended by Z X81 news letter, ma tchbot £49.95 + Carr. Dim. 19" wide 16" deep 10.5" high. size up to 1000 watt load £5.95 Useable area 16"w 10 5"h 11 .5"d. 7407 2102-6 4116-3 L2127 compact comoletuIr , ,used unit with 3 pin fitted Also available LESS PSU, with FANS etc. Internal dim. CALL SALES OFFICE FOR PFICES vncket ur, o 750wau, £9-99 19"w. 16"d. 10.5"h. £19.95. Carriage 8 insurance £9.50.

SAVE'-' COOLING PANS e Keep your hot parts COOL and RELIABLE SUPER PRINTER SCOOP EO MONITO with our range of BRAND NEW professional 5" CASED Superb little unit made by HITACHI in ergonimcally designed free coolin fans. will Dim. 92 x 92 x 25 mm. 739-T standing case. Very high definition display ETRI 99XU01 132 wide! 12v DC Miniature 240 v equipment fan complete with small but readable columns .. CEN opp. @ 800 ma, so ideal for mobile use. finger guard £9.95. BRA, The "Do Everything Printer" at a price that will with 3" x 3" x 2.5" compact Supplied in AS NEW condition -complete GOULD JB-3AR Dim. NEVER be repeated. Standard CENTRONICS inp. 8 White very quiet running 240 v operation. NEW £8.9 data. Composite 75 ohm vid Black lbbî tie parallel interface for direct connection to BBC, CRT Eq.00 or Green CRT £55.00 8-16 v DC micro BUHLER 89.11.22. ORIC, DRAGON etc. Superb print quality with full Carr 8 Ins £5.00. fan. a / 1/4.-b, brushless miniature reversible Uses pin addressable graphics and 4 type fonts plus Made the British KGM Co. servo motor for extremely high air flow, 12" CASED. by HIGH DEFINITION internal PROPORTIONAL SPACED for use as a data almost silent running and guaranteed 10,000 for WORD PROCESSOR applications. 80- 132 Designed continuous J MODE unit is totally housed in an hr life. Measures only 62 e 62 x 22 mm. columns, single sheet, sprocket or roll paper handling plus display station, Current cost £32.00. OUR PRICE ONLY much more. Available ONLY from DISPLAY ELECTRONICS attractive brushed aluminium case with ON- £12.95 complete with date. at the ridiculous price of ONLUEI99.00 + VAT Complete with OFF, BRIGHTNESS and CONTRAST MUFFIN -CENTAUR standard 4" x 4" x 1.25" full manual etc. Limited quantity -Hurry while stocks last. controls mounted to one side. Much fan supplied tested EX EQUIPMENT 240 v at Options. Interface cable (specify) for BBC, ORIC, attention was given to construction and NEW 240v otiL £6.25 or 110 vat £4.95 or BRAND £19 DRAGON or CENTRONICS 36 way p g £ 12.50. Spare ribbon reliability of this unit with features such as, at £10.50. 1000's of other fans Ex Stock £3.00 each. BBC graphics screen dump utility program £8.50. internal transformer isolated regulated DC fans C1.6 Call for Details. Post 8 Packing on all Carriage and Ins. £ 10.00 + VAT supply, all components mounted on two fibre glass PCB boards - which hinge out for ASR33 ease of service, many internal controls for EPROM COPIERS GE TERM/PRINTER standard A massive purchase of these desk top linearity etc. The monitor accepts The amazing SOFTY 2. The 'Complete Toolkit' ourAT 75 ohm composite video signal via S0239 for writing, copying, modifying, and listing printer -terminals enables us to otter you these quality 30 cps printers at a SUPER I/FROME/95 TCAR..LR socket on rear panel. Bandwidth of the unit EPROMS of the 2516, 2716, 2532, 2732 Fully fledged industry standard ASR33 data around 20 Mhz and will display range. Many other functions include integral LOW PRICE against their original cost of is estimated over £1000. Unit comprises of full OWERTY terminal. Many features including ASCII most high del graphics and 132 x 24 lines. keyboard, cassette interface, serial and parallel with for data I/O auto data modulator. electronic keyboard and printer mech keyboard and printer Units are secondhand and may have screen data Vo, UHF print face similar to correspondence quality RS232 serial interface. 110 ONLY £189.00 + PP £2.50 detect circuitry. burns. However where burns exist they are typewriter. Variable forms tractor unit baud, 8 bit paper tape punch and reader for only apparent when monitor is switched off. NEW 'GANG OF EIGHT intelligent Z80 enables full width - up to 13.5" 120 column and ridiculously controlled gang bang programmer for ALL off line data preparation Although unguaranteed all monitors are paper, upper - lower case, standard RS232 cheap and reliable data storage. Supplied in to Dimensions single 5V rail EPROMS Copies up to 8, 27128 serial interface, internal vertical and tested prior despatch. good condition and in working order x in typ ONLY 2 MINUTES!! Internal LCD horizontal tab settings, standard ribbon approx. 14" high 14" wide by 11" deep. display and checking routines for IDIOT adjustable baud rates quiet operation plus Options: Floor standE12.50 + VAT Supplied complete with circuit. 240 volt AC PROOF operation. ONLY £395.00 + PP £3.00 many other features. Supplied complete KSR33 with 20ma loop interface£ 125.00 + operation. ONLYE45.00 PtuEE9.50CARR. Data sheets on request. with manual. Guaranteed working £130.00 or Sound proof enclosure £25.00 + VAT 24" CASED. Again made by the KGM Co untested £05.00, optional floor stand £ 12.50 with a similar spec as the 12" monitor. Carr B Ins £10.00 OFFER Originally used for large screen data PROFESSIONAL KEYBOARD display. Very compact unit in lightweight An advantageous purchase of brand new surplus allows a great OWERTY, full travel, COLOUR MONITORS alloy case dim, 19" H x 17" D x 22" W. All NOVEX NC -1414-CL Fully cased brand new chassis keyboard offer at fractions of their original costs. ALPHAMERIC 7204/60 full ASCII 60 key, upper, lower + control key, parallel TEL silicon electronics and composite video 14" colour monitor. Many exacting features input make an ideal unit for schools clubs. such as RGB TTL and PAL composite video output plus strobe. Dim 12" x 6" +5 8 -12 DC. £19.50 - DEC LA34 Uncoded keyboard with 67 quality, GOLD, normally open switches on shops etc Supplied in a used but working inputs, Internal speaker and audio amp, condition "GREEN TEXT' switch for high del text standard X, Y matrix. Complete with 3 LED indicators 8 i/o cable - ideal micro applications and matching BBC colour conversions etc. pcb DIM 15" x 4.5"£2495 Carriage on keyboards £3.00. ONLY £55.00 PLUS E9.50 CA RR 6 INS. scheme make this monitor ideal for the most exacting user. Brand new and Fully Guaranteed only £199.00 + £10.00 cart. SUPER DEAL? NO - SUPER STEAL!! SEMICONDUCTOR The FABULOUS 25CPS TEC Starwriter 'GRAB BAGS' Mixed Semis amazing value contents DATA MODEMS RpND$VW AT ONLY £4- +VAT- irr include transistors digital, linear, I C.'s tnacs Join the communications revolution with our irrrri 7 diodes, bridge recs.. etc etc. All devices range of EX TELECOM data modems. Made to Made to the very highest guaranteed brand new full spec. with manu- most stringent spec and designed to operate spec the TEC Starwriter facturer's markings, fully guaranteed. for 24 hrs per day. Units are made to the FP1500-25 features a ` 50+£2.95 100+15. IS. CCITT tone spec With RS232 i/o levels via heavy duty die cast TTL 74 Series A gigantic purchase of an a 25 way 'D' skt. Units are sold in a tested chassis and DIABLO type across the board" range of 74 TTL series and working condition with data Permission print mechanism giving I C's enables us to offer 100+ mixed may be required for connection to PO lines. superb registration and "mostly TTL" grab bags at a price which two print quality. Micro- SaJ%je or three chips in the bag would nnormally MODEM 2B "Hackers Special" fully fledged 0 I.C.'s full electronics cost to buy. Fully guaranteed all up to 300 baud full duplex, ANSWER or CALL. processor 300+ E19.50 modes. AUTO ANSWER. Data i/o via ofl a fraction spec. 100+ £6.90 200+111.30 standard RS232 25 way 'D' socket. Just 2 wire cofmrmalndcompatabIM of its connection to comms line. Ideal networks etc. and full control via CPM Wordstaretc. original cost. Complete with data, tested, ready to run at a 'Many other features include bi direction NEW SUPER LOW PRICE of ONLY MOO + printing, switchable 10 or 12 pitch. full width 381 mm paper handling with upto DEC CORNER VAT + Can. 163 characters per line, friction feed rollers for single sheet or continuous paper MOSTEK CRT 80E Brand new dual MODEM 20-1 Compact unit for use with internal buffer, standard RS232 serial interface with handshake eurocard, Z80 based VT100 PLUS MICRONET. PRESTEL or TELECOM GOLD Supplied absolutly BRAND NEW with 90 day gguarantee and FREE daisy wheel emulator with graphics etc £499.00 etc. 2 wire direct connect 75 baud transmit and dust cover. Order NOW or contact sales office for more information. BA11-MB 3.5" Box, PSU, LTC £325.00 1200 baud receive Data i/o via RS232 'D' Optional extras- RS232 data cable £10.00. Tech manual £7.50. Tractor feed DLV11-J 4 x EIA interface £310.00 socket Guaranteed working with data 149.95 140.00. Spare daisy wheel £3.00. Carriage & Ins. (UK Mainland) £10.00. RK05-J 2.5 Mb disk drives £650.00 MODEM 20-2 same as 20.1 but 75 baud PDP1105 Cpu, Ram, i/o, etc. £150.00 receive 1200 baud transmit £130.00 ELECTRONIC RT11 ver. 38 doc kit £70.00 TRANSDATA 307A 300 baud acoustic COMPONENTS LA36 Decwriter EIA or 20 ma £270.00 coupler RS232 i/o £95.00 EQUIPMENT KLBJA PDP 8 async i/o £175.00 66% DISCOUNT MIRE PDP 8 Bootstrap option £75.00 NEW DSL2123 Multi Standard modem enables us to bring you the best possible Due to our massive bulk purchasing programme which DILOG D0100 RK05 LSI 4 e RK05 disk selectable V21 300-300 bps, V23 75-1200, s. bargains we have thousands of I s. Transistors, Relays. Caps, PCB Sub -assemblies, V23 1200-75 full duplex. 1200-1200 half controller £150.00 Or Switches. etc etc. surplus to our requirements. Because we don t have sufficient stocks of any duplex modes. Full auto answer via modem or MSC4804 (Equiv MSV11-L) 256k bytes one item to include in our ads we are packing all these items into the BARGAIN PARCEL OFA CPU. LED status indicators. CALL or ANS ram card 1499.00 of components at giveaway prices' Guaranteed to be worth modes Switchable CCITT or BELL 103 & LIFETIME Thousands LAX34-AL LA34 tractor feed £15.00 value" Sold by weight 202. Housed in ABS case size only 2.5" x 8.5" at least 3 nines what you pay. Unbeatable 1000's of EX STOCK spares for DEC x 9". f286.00 + VAT 2.5k1s £4.25 + pp £1.25 5k1s £5.90 + £1.80 POPE PDP11 PDP15 6 periperhals. For further data or details on other EX STOCK 10k1s £10.25 + pp £2.25 20 kls £17.50 + £4.75 Call for details. All types of Computer modems contact sales office. equipment and spares wanted for prompt Carriage on all modems £10.00 + VAT. PRICES PLUS VAT CASH PAYMENT All pricesquoted areforU.K Mainland, paid cash with order in PoundsStirlingPLUS VAT. Minimum ordervalue£2.00. MinimumCredit Card order£ 10.00. M inimum BONA FIDE account orders from Government depts, Schools, Universities and established companies £20.00 Where post and packing not indicated please ADD £ 1.00. + VAT Warehouse open Mon -Fri 9.30 - 5.30. Sat. 10 15- 5 30 We reserve the right to change prices and specifications without notice. Trade, Bulk and Export enquiries welcome London SE19 3XF P ' CI i- i Fiilyl r 32 Biggin Way, Upper Norwood, L_i I l\ L II II i _1 Telephone 01-679 4414 Telex 27924 .te CIRCLE 62 FOR FURTHER DETAILS. 88 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com WELL WORTH A SE:(':i LOOK... ,>4 No - you're not seeing double, just the Crotech 3132's Component Comparator in action. This unique feature, using two Crotech component testers, gives you the benefit of checking an active or passive component against a known standard. Complete circuits can also be checked using signature techniques. 4> But that's not the only new feature. The 3132 has three DC source outlets available on the front panel, capable of powering most solid state circuits. Dare we say that the 3132 is the nearest affordable 'scope to come near to being a complete test system?

Add & Subtract

Pc- 20MHz

2mV/div Crotech instruments Limited 2 Stephenson Road, St. Ives, Huntingdon, Cambs. PE17 4WJ Telephone: (0480) 301818 For full data sheet and a copy of our Highlight brochure - all free - just give us a call or fill in the enquiry card j

CIRCLE 41 FOR FURTHER DETAILS.

SPE D'uil HIGH QUALITY PRECISION PLIERS AND CUTTERS These precision box jointed pliers and cutters are manufactured in West Germany and are of extremely high quality. They are supplied to and used by the electronics industry. They all have double leaf springs, moulded -on PVC grips and polished heads. The cutters have induction hardened cutting edges. As a little test of the quality and the squareness and fit of the jaws we tried Wirelégarld holding pieces of paper with the pliers and cutting the paper with the cutters - we were extremely impressed. Naturally we also tested them with wire and were equally pleased with the results. We decided to offer readers the alternative of a set of the three most vital tools, comprising top cutters, side cutters and snipe nose pliers (smooth

SET A inside jaws). All are approximately 43/4" long. In shops this set (Set A) would comprises Top Cutters cost about £29.70, but our price to readers is £19.50 incl VAT and UK p&p. Side Cutters is a Snipe Nose Pliers Our alternative choice the above set plus pair of round nose pliers which are extremely useful for shaping wires, etc. This set (Set B) comprising the four tools would normally cost £38 but we are offering it at only £24.75 incl VAT and UK p&p. TOP CUTTERS Push tutting We regret the tools are not available separately - only the sets as offered. SIDE CUTTERS To order either of the ajove, use coupon or photocopy or on plain paper and send with crossed cheque/PO made out to Wireless World Offers. Send to Pliers Offer, 48 Beauchamp Place, London SW3 1NX. Allow up to 28 days for delivery, UK addresses only. Closing date July 31st 1984. W VAT receipt will be supplied if SAE is enclosed with order.

Coupon to Wireless World Pliers Offer, 48 Beauchamp Place, London SW3 1NX Please send me. SET B comprises of Pliers/Cutters Sets NAME Sel A Round Nose Pliers plus (please print) Set A at £19.50 ADDRESS

Set B at £24.75

for which I enclose total £

SNIPE NOSE PLIERS ROUND NOSE PLIERS Price includes postage, packing and VAT. Offer applies to UK only. Please allow 28 days for delivery. Registered No. 151537. Reg. Office: Quadrant House, Sutton, Surrey SM2 5AS. 83/199 PRECISION BO% JOINTED PLIERS AND CUTTERS

ELECTRONICS & WIRELESS WORLD JULY 1984 89

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0.35 0A7 0081Z 1.20 ZS271 0.23 2/4698 0.32 2N3441 0.85 25026 . 25.00 BCY34 1.00 AD149 0.75 BC125 0.18 B1178 0.35 2.00 OAIO 0.55 0082 0.90 ZS278 0.57 2N705 1.25 2N3442 1.25 25103 1.50 BCY39 3.49 AD161 0.35 BC126 0.18 B1179 0.35 BU205 1.30 0A47 0.12 003 1.00 Z11(107 0.12 2N706 0.25 2N3614 2.20 25302 2.00 AD162 0.35 BC135 0.15 BCY4O 2.80 BF180 0.28 BU206 1.50 0A70 0.25 0084 0.80 ZTX108 0.12 2N708 0.25 2N3702 0.11 0.30 25303 1.50 AF106 0.35 BC136 0.19 BCY42 BF181 0.28 BU208 2.00 0A79 0.12 0022 2.75 ZT3(109 0.12 2N930 0.25 2N3703 0.11 2S322 3.50 AFII4 0.75 BC137 0.19 BCY43 0.30 61182 0.30 BY100 0.40 OA/31 0.17 0C123 2.00 ZTX300 0.13 2N1131 0.30 2043704 0.11 0.19 2S324 3.50 A1115 0.75 8C147 0.12 BCY58 BFI83 0.28 BY126 0.13 0A85 0.17 0C139 3.00 ZTX301 0.14 2041132 0.30 2N3705 0.11 20701 2.00 AF116 0.75 5C148 0.12 BCY70 0.17 81184 0.28 BY127 0.14 0A90 0.08 0C140 4.00 ZTX302 0.18 2041302 1.20 2N3706 0.11 0.10 257459 0.95 AFII7 0.75 BC149 0.13 BCY71 B1185 0.30 BZX61 0.17 0A91 0.08 0C141 4.25 ZTX303 0.18 2NI303 0.80 2N3707 0.11 25746A 0.95 AF139 0.33 BC157 0.13 BCY72 0.17 B1194 0.14 Series 0A95 0.08 0C170 1.25 ZTX304 0.20 2N1304 1.20 2N3708 0.10 AF186 1.00 BC158 0.13 BCZII 1.75 B1195 0.12 BZY88 0.10 0A200 0.15 0C171 1.25 Z1X311 0.13 2N1305 1.00 2N3709 0.11 AF239 0.39 BC159 0.13 BD115 0.42 BF1% 0.13 Series OA202 0.15 0C200 1.50 ZTX314 0.25 2N1306 1.50 2N3710 0.10 CV Devices AFZII 4.00 BC167 0.11 BD121 1.70 BF197 0.14 CRS1/40 0.60 0A211 1.50 OC201 2.50 ZTX500 0.14 2N1307 1.10 2N3711 0.10 Large stocks AFZ12 4.00 BCI70 0.11 5D123 2.80 BF200 0.40 CRS3/40 0.75 OAZ200 1.50 0002 2.75 ZTX501 0.14 2N1308 1.75 2N3771 1.40 Prices on ASY26 1.40 BC171 0.11 BD124 2.00 61224 0.25 CRS3/60 0.90 OAZ201 1.50 0C203 3.00 Z114502 0.18 2N1309 1.20 2N3772 1.60 application ASY27 0.90 BC172 0.11 0D131 0.44 BF244 0.28 GEX66 3.00 OAZ206 1.50 0C204 3.00 ZTX503 0.19 2N1613 0.32 2N3773 1.80 EI3OL 18.50 EF85 1.75 GU51 20.00 OD3 2.50 QY3-65 59.86 UF41 2.00 4-250A 80.00 6CG7 2.50 12AX7 1.75 5642 9.00 VALVES EIBOCC 10.50 EF86 1.75 GXUI 15.35 OZ4 3.50 QY3-125 66.50 UF42 2.10 4_400A 87.00 6CH6 13.00 I2AY7A 4.00 5654 3.00 E1001 10.20 EF89 2.50 GXU2 30.00 PC86 2.50 QY4-250 68.00 1.1110 1.75 4B32 20.00 6CL6 3.75 12134A 3.50 5651 4.45 A1834 9.00 E182CC 13.25 EF91 2.95 GXU3 25.40 PC88 2.91 QY4-400 74.20 UF85 1.75 4C35 78.00 6CW4 8.00 12BA6 2.50 5670 4.S0 A2087 13.50 E1861 11.50 E192 6.37 GXU4 44.50 PC95 1.75 QY5-500 175.00 UF89 2.00 4CX250B 45.00 602 1.50 12BE6 2.50 5675 28.00 A2134 17.50 E188CC 8.91 EF93 1.50 GXU50 20.00 PC97 1.75 QY5-3000A UL41 3.50 4CX350A 73.00 6DK6 3.00 12BH7 2.75 5687 6.00 A2293 16.00 E2801 22.51 EP94 2.50 GY501 3.00 F(.'900 1.75 420.00 UL84 1.75 4X150A 60.00 61)Q611 4.75 12BY7 3.00 5696 4.50 A2426 27.50 E283CC 12.00 EF95 5.99 GZ32 .4.00 PCC84 1.50 QZ06-20 32.70 UM80 2.00 4X150D 56.00 6FA8 3.00 12E1 20.00 5718 7.50 A.2521 25.00 E288CC 17.50 EF98 2.00 GZ33 4.75 PCC85 1.50 RIO 6.00 UY4I 2.25 5B254M 35.00 6E118 2.50 12E1 ITT 28.00 5725 5.50 A2900 15,00 EA52 32.25 EF183 2.00 GZ34 3.00 PCC88 2.00 817 3.00 UY85 2.25 5B255M 35.00 6EW6 2.25 12E14 65.00 5726 11.37 A3343 45.00 EA76 2.50 EF184 2.00 GZ37 4.75 PCC89 1.75 R18 3.00 VLS63I 15.00 5C22 160.00 6F6 3.00 13E1 170.00 5727 7.05 AZ31 2.75 EABC80 1.25 EF804S 12.00 KT61 5.00 PCC189 2.50 819 9.24 XG1-2500 55.00 51180E 1650.00 6F23 1.60 19H4 27.50 5749 2.50 AZ41 2.60 EAC91 3.50 EF805S 15.00 KT66 12.00 PCC805 1.60 R20 2.50 XG2-6400 5R4GY 3.50 6128 1.60 19115 47.50 5751 4.00 BK448 114.90 EAF42 2.50 EH90 1.75 KT77 Gold Lion PCC806 1.60 RG3-250 32.68 141.90 5Ú4G 3.00 6F33 33.50 2409 67.25 5763 4.50 131(484 155.35 EAF801 2.00 EK90 1.50 9.00 PCE82 2.00 RG3-250A 32.68 XG5-500 26.60 51/406 2.50 6H1 14.00 30CI5 2.00 5814A 4.00 BS90 58.00 EB41 4.00 EL32 2.50 KT88 15.00 PCF80 2.00 RG3-1250 59.50 XG2.6400 5V4G 2.50 6H2N 2.75 30C17 2.00 5840 4.00 135810 60.00 EB91 1.50 EL33 4.00 KTW61 2.50 PCF82 1.50 95341250 61.60 162.00 5Y3GT 2.50 611304 2.75 30C18 2.00 5842 12.00 BTS 58.95 EBC33 2.50 EL34MUI 4.00 KTW62 2.50 PCF86 2.50 RG4-3000 99.45 XR1-1600A 5Z3 4.00 6116 3.00 30F5 1.60 5876A 31.50 BTI7 151.00 EBC4I 2.50 ELM 2.S0 KTW63 2.50 PCF87 2.00 RR3-250 40.00 53.75 5Z4G 2.50 6J4 5.50 301L1/2 1.38 5879 5.00 5T19 44.05 EBC81 1.50 ELM 2.80 M8079 11.34 PCF200 3.25 RR3-1250 15.75 XRI-3200 81.97 5Z4GT 2.50 6J6 8.93 301L12 1.80 5886 15.00 BT29 349.15 EBC90 1.2S EL42 2.50 M8080 8.25 PCF201 3.25 S11E12 65.00 XR1-3200A 6.30L2 1.75 6J7 4.75 30FL14 2.00 5963 2.50 5169 354.80 EB180 1.50 EIA1 5.25 M8081 9.82 PCF801 2.50 S130 6.00 XRI.6400 6AB4 1.75 6K4N 2.50 3Oí-1 1.50 5965 3.50 0195 129.90 EBF83 1.75 EL83 6.00 448082 9.69 PCF802 2.50 SI3OP 6.00 102.00 6AB7 3.00 6K6GT 2.75 30L15 2.00 6005 2.25 CBL31 4.00 EBF89 1.50 EI.84 2.25 M8083 8.58 PCF805 1.70 STV280.40 YDI120 395.00 6AC7 3.00 6K7 3.00 301.17 2.00 6021 4.50 CL33 4.00 EBL3I 4.00 EL86 2.75 M8091 10.43 PC1806 1.70 14.00 1D1240 450.00 6AF4A 4.25 61(8 3.00 30P4 2.50 6057 10.23 CY31 3.00 EC90 1.25 EL90 2.25 M8096 6.80 PC1808 1.70 STV280-80 Z759 25.00 6AG7 3.00 61(06 7.00 30P19 2.50 6058 12.30 CIK 20.00 EC91 8.00 EL91 9.69 M8097 8.10 PCL82 2.00 21.00 ZMI000 8.00 6AH6 5.00 6L6G 3.00 30PL1 3.00 6059 6.00 C3A 22.00 EC92 1.75 EL95 2.00 M8098 6.15 PCL83 3.00 SU41 5.00 ZM1001 8.00 6AK5 5.99 6L6GA 3.00 3OPLI4 1.80 6061 6.00 COJA 22.00 EC157 380.00 EL156 30.00 608099 8.00 PCL84 2.00 SU42 10.00 ZM1020 9.00 6AK6 2.50 6L6GC 3.00 30PLI5 1.80 6063 3.75 DA4I 25.00 ECC33 4.50 ELMO 8.50 M8100 9.52 PC1A5 2.50 TD03-10 35.00 ZM1021 9.00 6AL5 1.50 6L6GT 3.00 35W4 1.00 6064 0.58 DA42 18.70 ECC35 4.50 EL500/504 3.00 M8136 10.23 PCL86 2.50 TD03-101 35.00 ZM1022 9.00 6AM4 4.00 6L7 2.50 SOCS 1.50 6067 10.23 DAF91 1.75 ECC40 4.50 EL509 7.00 M8137 10.23 PCL805/85 2.50 TT15 50.00 ZM1023 9.00 6AM5 9.69 6N2P 2.50 7551 6.05 6072 6.00 DAF96 1.75 ECC81 1.75 EL821 13.00 M8140 6.00 PD500 6.00 TT21 30.00 ZM1040 19.36 6AM6 6.02 6N3P 2.50 75C1 4.50 6080 14.00 DET22 35.00 ECC82 1.75 EL822 13.97 M8141 6.50 PE06-40N 45.00 TT22 37.50 ZM1041 16.66 6AN5 4.75 6N7 3.00 85A1 7.50 6097A 235.00 0E124 49.00 ECC83 1.75 EM34 5.00 M8142 8.75 PFL200 2.50 T1100 60.00 ZM1042 17.77 6AN8A 3.50 6P25 4.00 85A2 4.45 609713 200.00 D191 1.75 ECC84 1.75 EM80 2.50 M8144 7.50 PL36 2.50 TY2-125 65.00 1B3GT 3.00 6AQ5 2.25 6Q7 3.75 90AG 12.94 6146A 8.25 DF96 1.75 ECC85 1.75 EM81 2.50 918149 6.50 PL81 1.75 TY4-400 75.00 1B24 25.00 6AS6 8.66 6R7 3.25 90AV 12.96 6146B 8.25 DK91 1.75 ECC86 2.50 E3184 2.00 M8161 9.35 PL81A 2.00 TY4-500 98.35 1835A 48.00 6AS7G 8.75 6SA7 3.00 90C1 6.00 6159B 19.00 01(92 2.00 ECC88 2.10 EM85 2.75 M8162 10.40 PL82 1.50 TY5-500 201.50 1663 64.00 6ÁT6 1.25 65C7 2.75 90CG 14.54 6189 9.50 DK% 1.75 ECC89 2.00 EM87 2.50 M8163 8.25 PL83 2.50 TY6-800 196.50 IRS 1.75 6AUSGT 5.00 6517 2.50 90CV 15.45 6201 11.40 DL92 2.00 ECC9I 8.93 EN32 17.46 M8190 5.00 PL84 2.00 TY6-5000A 155 1.75 6AU6 2.50 6S007 3.00 92AG 15.50 6442 20.00 DL94 1.75 ECC189 2.10 EN91 87.05 M8195 10.85 PL504/5 2.50 490.00 1T4 1.75 6AVSGA 4.50 6.517 3.25 92AV 12.96 68838 8.25 DL% 1.75 ECC807 1.75 EN92 6.96 M81% 7.50 PL508 2.50 TY6-5000B 2A515 11.50 6AV6 1.50 65K7 3.50 95A1 8.45 6973 4.00 DLSIO 14.00 ECC808 3.00 EY51 2.75 M8204 7.05 PL509 6.00 395.00 2C39A 60.00 6AX5GT 3.00 6SK7GT 3.00 15082 6.50 7025 3.00 DLS15 12.50 ECF80 1.55 EY81 2.50 M8212 11.37 PL5l9 6.00 TY6-5000W 2C43 70.00 667 3.25 65N7GT 3.00 15083 8.35 7551 6.2S DLS16 12.50 ECF82 1.50 EY83 2.50 M8223 6.00 PL801 1.50 407.00 2021 315 6B8 3.25 65Q7 3.40 15002 3.25 7586 12.00 DLSI9 12.50 EC186 2.50 EY84 9.24 M8224 6.30 PL802 6.00 TY7-6000A 2E26 8.25 6BA6 1.50 6SR7 1.00 150C4 6.00 7587 18.50 DM70 2.00 ECH35 3.00 EY86 1.75 M8225 4.50 PY33 2.50 485.00 2J42 98.00 6BA7 5.00 6557 2.75 211 35.00 7609 56.00 DM71 2.00 ECH42 3.50 EY88 1.75 M8248 14.03 PY8I 1.50 TY7-6000W 2J55 175.00 6BA8A 4.00 6125G 3.50 723AB 125.00 7868 6.00 DM160 4.75 ECH81 3.00 EY500A 3.00 MD2901 115.00 PY82 1.50 303.60 2J70A 383.00 6BC4 4.00 6U8A 2.25 803 25.00 7895 12.00 DY87 1.50 ECH83 2.50 EY802 1.75 MU14 2.50 PY83 2.50 TZ40 25.00 21706 336.00 6BE6 1.50 6V6GT 2.25 805 45.00 8005 110.49 DY802 1.50 EC1484 2.50 EZ35 1.75 542(119 55.00 PY88 2.00 U18-20 3.50 21(25 125.00 6BH6 2.50 6X4 2.00 807 3.7S 8068 14.00 E55L 45.00 ECL80 1.50 EZ40 2.50 MX123 72.00 PY500A /.00 U19 13.75 3.400Z 85.00 6616 2.25 6X5GT 1.75 811A 18.33 8122 90.00 E80CC 8.81 SCIAI 1.75 EZ41 2.50 M34145 56.70 PY800 1.50 U25 2.50 3-500Z 85.00 MI KA 4.50 7B7 2.50 812A 18.33 8136 2.50 F8PCF 11.27 EC182 1.50 EZ80 1.50 MXI51 17.25 PY801 1.50 U26 2.50 3A5 3.00 6BL6 85.00 7C5 4.00 813 125.86 8417 6.00 E80F 14.19 ECL83 3.00 EZ81 1.50 MX152 131.25 Q1451 82.50 U37 12.00 3824 11.00 6BL7GT 4.50 7C6 2.50 833A 193.16 18042 11.53 BAWL 13.73 ECI.84 1.50 EZ90 2.00 MX161 152.25 QQV02fi 30.50 UABC80 1.25 . 3828 15.35 6BM6 115.00 7117 4.00 866A 20.03 18045 10.49 E81CC 8.00 OCIAS 1.50 FW4-500 3.50 MX163 20.25 QQV03-10 20.50 UAF42 2.50 3829 20.05 68546 2.00 7R7 4.25 872A 20.00 E81L 13.27 ECL86 1.75 FW4-800 3.50 MX164 25.52 QQV03-20A UB41 3.00 313240M 17.50 6607A 3.50 7S7 3.50 922 6.00 Tested E82CC 8.10 EF37A 5.00 GI .371K 35.00 MX166 147.00 48.38 UBC41 2.25 3B241M 17.50 6BR7 6.00 7Y4 2.25 931A 18.50 Ex -Equipment E83CC 8.40 EF39 2.75 G551K 12.00 54X168 50.00 QQV06-40A UB189 1.50 303 25.00 6BR8A 3.50 7Z4 2.00 1624 4.00 4CX2505 6.50 E86C 8.25 EF40 5.00 0180.2M 17.50 N78 15.00 65.30 UCC84 1.75 3C45 24.50 66S7 6.00 11E3 55.00 1625 3.50 CV Devices E88C 8.25 EF41 3.50 G240.2D 12.00 0A2 3.25 QQy07-5068.60 UCC85 1.85 3C)(100A5 6BW6 6.00 12AH8 5.00 Large stocks F88í. 8.42 EF42 4.50 0400.1K 17.50 0A.32.50 QQZ06.40A UCF80 2.00 47.00 6BW7 1.50 12AT6 1.50 42Ì2E wU7: Prices on E90CC 9.47 E150 2.50 GN4 9.00 OA4 6.00 62.20 UCH42 2.50 3E29 45.00 6BX7GT 580 12AT7 1.75 4212F13. application E9OF 9.90 EF54 5.00 GN4A 9.00 082 4.35 QU37 12.50 UCH8I 2.50 354 2.00 6BZ6 2.75 12AU6 2.50 5544 E91H 6.25 EF55 3.50 GS16 16.00 OB3 2.50 QVO3-12 6.80 UCL82 1.75 3V4 1.75 6C4 1.25 12AU7 1.75 5545 102.00 E92CC 8.75 E180 1.75 GTIC 15.00 0C2 4.35 QV44-7 3.50 UCL83 2.75 465A 60.00 6CB6A 2.50 12AV6 2.50 5551A 114.90 E99F 9.10 EF83 4.00 GUSO 20.00 0C3 2.50 QV08-100155.70 4-125A 60.00 6CD6GA 5.00 12AV7 3.50 5552A 155.35 0.73 0.51 1.02 INTEGRATED CIRCUITS 77496 74141 74Ì76 TBA53Ó 1:99 7400 0.16 7423 0.33 7460 0.18 7497 3.15 74142 2.30 74178 1.36 TBA540Q 2.30 SADPI 55 00 VCRSI78 10 00 7401 0.17 7425 0.30 7470 0.38 74100 1.54 74143 2.60 74179 1.36 TBA550Q 3.22 BASES CRTs SCPI 10.00 VCR517C 10.00 7402 0.17 7427 0.30 7472 0.33 74107 0.45 74144 2.60 74180 1.20 TBA560CQ 3.21 2API 8.50 SCPIA 44.00 74109 0.73 74145 1.00 74190 1.90 TBA673 2.20 26P1 9.00 7403 0.17 7428 0.43 7473 0.38 87Gunakined 0.25 5 ISA 15.00 7430 0.17 0.38 74110 0.51 74147 2.00 74191 1.90 TBA700 1.52 3BP1 7404 0.18 7474 B7Gskirted 0.35 12'.005UP7 25.00 7405 0.18 7432 0.30 7475 0.54 74111 0.71 74148 1.76 74192 140 TBA720Q 2.30 B9A unskined 0.25 5.00 3DPI 007-5 63.32 7406 0.43 7433 0.40 7476 0.02 74116 1.85 74150 1.80 74193 1.90 TBA750Q 2.07 B9Askirted 0.35 3E01 10.00 007-31 58.07 Tube Bases 74118 1.00 74151 0.94 74194 1.25 TBA800 1.20 31P7 6.00 7407 0.43 7437 0.32 7480 0.56 Int Octal 0.35 1)G7-32 58.07 Prices on 7408 7438 0.32 7482 0.75 74119 1.54 74154 1.00 74195 1.20 TBA920 2.90 3GP1 6.00 0.20 Local 0.55 DG7-36 65.00 application 7409 0.20 7440 0.32 7483 0.00 74120 0.83 74155 0.90 74196 1.35 TBA920Q 2.90 Nuvistorbase 3JP1 8.00 2.00 0003-91 56.83 7410 0.17 7441 0.90 7484 1.05 74121 0.43 74156 0.90 74197 1.35 TBA990Q 2.90 8 pin 0.10 3JP2 8.00 DlLTexas DH7-11 113.12 7412 0.29 7442 0.72 7486 0.39 74122 0.62 74157 0.75 74198 2.70 TCA270Q 2.90 14 pin 3JP7 10.00 DIL Texas 0.10 VCR97 12.00 7413 0.32 7447AN 1.17 7490 0.60 74123 1.18 74159 2.20 74199 2.30 TCA760A 1.38 16 pin 3KP1 15.00 DlL Texas 0.10 VCR138 12.00 7416 0.32 7450 0.18 7491 0.82 74125 0.58 74170 2.40 TAA570 2.30 Valve screening 3RP1 35.00 VCR138A 12.50 74126 0.58 74172 4.40 TAA6305 3.50 3WP1 20.00 7417 0.32 7451 0.18 7492 0.60 cans all sixes 0.40' VCR139A 8.00 7420 0.18 7453 0.18 7493 0.60 74128 0.63 74173 1.42 TAA700 3.90 7422 0.20 '7454 0.18 7494 0.82 74132 0.72 74174 1.60 TBA480Q 1.84

Terms of business: CWO. Postage and packing valves and semiconductors 50p pe order. CRTs £1.50. Prices excluding VAT, add 15%. Telephone 01-677 2424/7 Price ruling at time of despatch. Telex 946708 In some cases prices of Mullard and USA valves will be higher than those advertised. Prices correct when going to press. E. & O.E. Account facilities to approved companies with minimum order charge £10. Carriage and packing £1.50 on credit orders. available Open to callers Monday -Friday 9 a.m.-5 p.m. Over 10,000 types of valves, tubes and semiconductors in stock. Quotations for any types not listad. S.A.E. NAVA 1 CIRCLE 20 FOR FURTHER DETAILS.

90 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com NEW PRODUCTS

SATELLITE WEATHER MAPS The use of new circuitry and a study of users' requirements has enabled Feedback to produce a weather satellite system, the WSR513, at a fraction of the cost of similar systems. The basic version will receive the APT (automatic picture transmission) signals from orbiting satellites in the 136 to 138MHz band. The addition of extra modules and a parabolic dish antenna allows reception of S -band transmission from geosynchronous satellites in the 1690 to 1697MHz band. The basic version is supplied with a helical omnidirectional antenna which incorporates a single -stage preamplifier. This feeds a tuneable v.h.f. receiver and the a .m. subcarrier from this is output to a decoder which converts it to digital form which is entered into the internal memory and provides a synchronizing signal. The ANY SOUND memory is continuously scanned SYNTHESIZER by the raster timing generator, in the dish antenna. The signal may be used as a teaching aid in and images are converted back to from this goes through an r.f. geography and in the study of the Up to eighteen different sound analogue signals and displayed switch which is used to select technical and engineering envelopes may be in the stored on the screen. S -band or APT transmissions. aspects. Each equipment is from synthesizer/amplifier unit Front panel control allows the Controls include channel supplied with a comprehensive Haven Automation. These may selection of resolution and format selection, automatic scan installation and operation manual be selected and mixed to emulate and local or satellite time for scan synchronization, semi -automatic as well as information on any combination of sounds 'from resolution and this can retain or picture acquisition and the satellites and the prediction of bass'. The birdsong to double remove the Doppler effect caused selection of a specific part of the orbits. Feedback Instruments synthesizer was originally by satellite motion. The version image for storage in the memory. Ltd, Park Road, Crowborough, developed to reproduce the to receive S -band transmissions Apart from its obvious uses in East Sussex TN6 2QR. complex sound spectra of a ship's includes a low -noise preamplifier weather prediction, the system EWW 205 engine room to make training exercises more realistic. The company is now exploring to the Ell, the target eprom and. to a microprocessor unit where it markets in the electronic EPROM to the microprocessor control will function as a pseudo-eprom. enhancement of musical system. The Ell has an access Elan Digital Systems Ltd, 16 to instruments, speech therapy, EMULATOR time typically of 175ns. Once 20 Kelvin Way, Crawley, West vehicle and aircraft simulations For use in conjunction with programmed, the system may Sussex RH 10 2TS. and the generation of sound their E series of editing eprom also be used connected directly EWW 206 effects. programmers, Elan have The system fits into 19in racks introduced the Ell eprom and includes a sound simulator, simulator which can speed up three mixer/amplifiers and a program and hardware distribution unit. Each circuit is development by simulating a identical to the others except that target eprom. Programs may be the different sounds are retained run, checked and easily altered on eproms. The units before being committed to interconnect and are controlled permanency in a eprom. One Ell through a GPIB which is also may be used to simulate any of used to control a set of filters to the current range of 24 and produce a required sound. 28 -pin devices including 2716, Eighteen signals from the 2732, 2764, 27128 and 27256. distribution unit are combined in Two units in a master/slave the three mixer/amplifiers to give configuration may be used to the desired mix and output level provide twin eprom simulation or for a specific environment. 16 -bit simulation. The Ell is Haven Automation Ltd, Cwmru available in two versions; one up Industrial Estate, Gendros, to 16K of memory (27128), the Swansea SA5 5LQ. other up to 32K (27256). Data is entered into the main EWW 207 programmer which is connected

ELECTRONICS & WIRELESS WORLD JULY 1984 91

www.americanradiohistory.com DECADE OSCILLATOR

LEVELL ELECTRONICS have a range of oscillators cover- ing frequencies from 0.02 Hz to 2 MHz. There is a FUNCTION GENERATOR that provides sine, square, triangular, pulse and ramp waveforms with high output levels over a wide range. Low distortion RC OSCILLATORS are available with analogue tuning and sine and square wave outputs. The digital tuned series are as detailed below:

FREQUENCY 0.2 Hz to 1.22 MHz on four decade controls. ACCURACY ±-0.02 Hz below 6 Hz. ± 0.3% from 6 Hz to 100 kHz. ± 1% from 100 kHz to 300 kHz. ± 3% above 300 kHz. SINE OUTPUT 5 V rms down to 30 NV with Rs = 600 S2. DISTORTION <0.15% from 15 Hz to 15 kHz. <0.5% at 1.5 Hz to 150 kHz. METER SCALES 2 Expanded voltage and -2/+4dBm. SIZE & WEIGHT 260 x 180 x 180 mm. 5 4 kg. TG66B TG66A Battery Mains & model £295 battery model £310

Prices exclude VAT. Free delivery in the UK. QUANTITY DISCOUNTS available. We supply many other instruments including: FUNCTION GENERATORS, COUNTERS, OSCILLOSCOPES, dB & MICROVOLTMETERS.

Maxon Street, Barnet, Herts. EN5 5SD, England. LEVELL ELECTRONICS LTD. Telephone: 01- 440 8686/449 5028.

CIRCLE 8 FOR,FURTHER DETAI IS.

The Archcr-&nJc ord Coínouter

The ARCHER -a new Z80 based single board computer for professional applications. After a power failure, it carries on where it left off and the on board watchdog guards against software crashes.

SDS ARCHER single board computer £150 SDS DEBUG ROM £ 20 SDS BASIC ROM £ 30 FEATURES SDS ARCHER, CASED with on/off * 4 MHz. Z80A switch, mains connector, lead etc. £200 * 2 serial ports -timer chip * Counter OEM and distributor discounts available * CMOS battery back-up * Bus expansion connector * On -board mains power supply Sherwood Data Systems Ltd * 4 Parallel ports with handshaking Sherwood House * 4 Bytewide memory sockets - up to 64k The Avenue * Power -fail and watchdog timer circuits Farnham Common * High quality double sided plated through PCB Slough SL2 3JX

hcrwood Data .yAcfm Ltd Tel. 02814-5067

CIRCLE 76 FOR FURTHER DETAILS.

ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com Appointments

DISPLAYED APPOINTMENTS VACANT: £ 17 per single col. centimetre (min. 3cm). Advertisments accepted LINE advertisments (run on): £3.50 per line, minimum £25 (prepayable). up to 12 noon Tuesday, BOX NUMBERS: £5 extra. (Replies should be addressed to the Box Number in the July 31st for August/Sept issue advertisement, c/o Quadrant House, The Quadrant, Sutton, Surrey SM2 5AS). subject to space available. PHONE: LUCY O'SULLIVAN, 01 661 3033 (DIRECT LINE) Cheques and Postal Orders payable to BUSINESS PRESS INTERNATIONAL LTD. and crossed.

ALWAYS AHEAD WITH THE BEST! £7,000-£22,000 * Where does your interest lie: Graphics; Comms; Robotics; Simulation; Image and S gnat Processing; Medical; Automation; Avionics; Sonar; Acoustics; Weapons; Radar; Opto and Laser? * Experienced in: Microprocessor Hardware or Software; Digital and Analogue circuitry; RF and Microwave techniques? * There are hundreds of opportunities in: Design; Test; Sales and Service for Táchnicians; Engineers and Managers * For free professional guidance: Call 076 384 676 (till 8pm most evenings) or send your C.V. (no stamp needed) to: ELECTRONIC COMPUTER AND MANAGEMENT APPOINTMENTS LIMITED Freepost, Barkway, Royston, Herts SG8 8BR

MICROPROCESSORS IN SOUND RECORDING BROADCASTING ENGINEER LATIN AMERICA We make a range of timing and control products in the professional audio and broadcasting field and have a vacancy for for an engineer to be in charge of production and test. The To work as a technical advisor with a Latinamerican organisation edu- cation by radio, with 40 affiliated radio stations in 17 countries. successful applicant would have experience in digital and The engineer will initially be based in Quito, Ecuador and will later travel microprocesor circuits (we use 68021, formal qualifications are to radio stations in other countries. The job consists of planning and important but not essential, an interest in sound recording running training courses for local technicians in the maintenance of stu- dio equipment and mainly small short and medium wave transmitters would be an advantage. A certain amount of field work would be and aerials. involved, so a driving licence would be required. A small Applicants should be familiar with the operation and repair of studio expanding company such as ours is greatly in need of a bright equipment and small transmitters and must be able to advise and and intelligent person will not only fill this post but also become instruct people with non -technical backgrounds in these skills. The post is initially for three years on a basic salary. Because of extensive involved in all parts of the company. travel, it is unlikely to suit applicants with families. CIIR provides Spanish Salary in the range of £8,000 £10,000. language training, pre -departure orientation (including instruction in - teacing methods), insurance, air fares and various allowances. Apply in writing to. STEPHEN BROWN APPLIED MICROSYSTEMS LIMITED, For a job description and application form, please send a brief c.v. to CIIR TOWN MILL, BAGSHOT ROAD, CHOBHAM, WOKING, SURREY. Overseas Programme, 22 Coleman Fields, London N1 7AF, quoting ref. 126251 WW1.

The Catholic Institute for International Relations operates a secular over- seas programme and is a member of the British Volunteer Programme. (2614) RADAR/RADIO ENGINEER SALARY: Scale 3/4 up to £8,700 approx p.a. including shift pay and weekend allowances. HOURS: 37 hr. wk. including Saturday and Sunday (no night duties). QUALIFICATIONS: CITY AND GUILDS FULL (TT4)-TECH/ONCor equivalent, + a clean driving licence. ELECTRONICS TECHNICIAN DUTIES: Repair and maintenace of airport 10cm. & 3cm. ground required for expanding South London company in the amusement industry. radars. Navigational aids including ILS and Communications equipment. Applicants are expected to have the appropriate qualifications (minimum HNC) and have experience of electronic engineering. Applicants should have considerable experience and be capable of working The work is interesting and varied, involving repairs, fault-finding without close supervision. Fault finding to component level is essential. and some research and development. Application forms are available from: Salary scale Is currently E8,400 -E9,000 per annum. Airport Director, Southend Airport, Essex, SS2 6YF. Tel. no. (0702) 40201 Complete applications to be returned by Applications giving full details of age, qualifications and experience. 126161 Friday 6th July 1984 (2639)

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NM ffl ffll MI ffl ale I» BIM IM 'MI CAPITAL APPOINTMENTS LTD 1 TEST EQUIPMENT THE UK's No. 1 ELECTRONICS AGENCY DESIGN ENGINEERS If you have HNC/TEC or higher qualifications and are I looking for a job in design, test, customer service, tech- nical sales or similar fields: Rediffusion Consumer Manufacturing design and manufacture colour television 1 a full range of advanced specification Telephone now for our free lobs list receivers and monitors. We have vacancies In all areas of the UK 1 Salarles to £15,000 pa Electronic Design Engineers 1 We are looking for experienced to help us maintain our industry lead in sophisticated 01-637 5551 or 01-636 9659 1 computer controlled test gear for production testing of our (24 hours) Future equipment will be an interesting mix 1 products. test of digital and analogue circuitry aimed at increasing the CAPITAL APPOINTMENTS LTD 1 automation of the production testing operation. 29-30 WINDMILL STREET, LONDON W1P 1HG 2450 If you are able to concetve,design and implement production RIM- - - - Ma - - - - - Mil - Mil IBM- - - test equipment with minimal supervision, we'd like to hear from you.

These positions are based in our Chessington Engineering Centre but some visits to our factories in the North East and Lancashire will be required at infrequent intervals. Salaries MEDICAL PHYSICS are obviously dependent on qualifications and experience, but will reflect the importance of future test gear projects to the TECHNICAL Company's long term development. Interested 7 ... Then write or phone: OFFICER Harry Brearley, Rediffusion Consumer Manufacturing Ltd., Medical Electronics Fullers Way South, Chessington, Stirrey. KT9 1HJ. Saudi Arabia Telephone: 01-397-5411. c. £14,950 p.a. inc. tax free Allied Medical Group are the British health care consultants to REDIFFUSION 240, the prestigious 650 bed Riyadh Al-Khaij health care programme in Saudi Arabia. The two hospitals which comprise the Programme are new, superbly equipped, mainly U.K. staffed and enjoy a full range of paramedical and support services. The Bio -Engineering Section of the Department of Medical Physics and Bio -Engineering - based in Riyadh - is ELECTRONIC responsible for servicing approximately 2,200 items from a wide range of bio -medical equipment. INSTRUMENT We now need an MPTO to specialise in the maintenance of an extensive range of laboratory equipment covering clinical FIELD SERVICE chemistry, haematology, microbiology and histopathology. The complexity of the equipment ranges from multi -channel TECHNICIANS analysers and centrifugal analysers to simple tissue processors Sartorius Instruments is a world leader in electronic other technicians weighing in the analytical, research, quality assurance and centrifuges. You will work with two and allied industries. The product range is expanding fur- repairing and scheduling maintenance of the laboratory ther into industry and personnel are required to supple- equipment. This small group also provides a maintenance ment our already established Field Service team. Areas service to the Medical Physics Department's Nuclear Medicine, with a vacancy include the South Midlands and Northern Radiation Protection and Radiotherapy Sections for their home counties plus a relief engineer prepared to travel nucleonic counting equipment. nationwide. For this post, you will need an HNC or equivalent plus at Successful applicants will service and install our elec- least four years experience. - tronic weighing instrument systems. Primary responsibi- The Sterling salary quoted (based on 5.0 Saudi Riyals = lities will be problem solving of Sartorius equipment con- £1) includes a bonus of one month's salary for each twelve tract maintenance and customer liason. months satisfactory service, payable at the end of contract. Education to a suitable allied qualification ie. C & In addition to the tax free salary, this two year single G/TEC - Electronics is preferred for the relief engineer. status contract post attracts one of the best benefits packages A successful trouble shooting ability in electronics exper- offered in the Middle East. ience of balance/scale service or maintenace of fine For further details and an application form, please write instruments is otherwise necessary. On appointment you will 4 weeks training in our workshop in Belmont. quoting Ref: P/RKH/6653/WW, to: Kate Vincent, Personnel spend Officer, Allied Medical Group, 12/18 Grosvenor Gardens, Candidátes must be in possession of a current driving ODZ. Alternatively, call our 24 hour answering licence and over 23 years of age. A company car is pro- London, SW 1W vided. service on 01-730 5339, quoting reference number. All applications will be dealt with in the strictest In additional to the above vacancies trainees are required for general electronic and mechanical balance confidence. maintenance at our in-house service centre at Belmont - Surrey. If you would like to apply for a position (l Allied Medical Group Please write for an application form to the in Fast Service Co-Ordinator M The Best of British Health Care the Middle Saratorius Instruments Ltd 18 Avenue Road Belmont Surrey Telephone No. 01-643 8870 (2621) (2832)

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CUT THIS OUT! Clip this advert and you can stop hunting for your next appointment. We have a wide selection of the best appointments in Digital, Analogue, RF, Microwave, Micro- processor, Computer, Data Comms and Medical Elec- EARLY RESPONSIBILITY tronics and we're here to serve your interests. Call us now for posts in Design, Test, Sales or Field

Service, at all levels from £6,000-£16,000. . `Technomar& IN ELECtRONICS Engineermg t- /eclmical Recruitment 11 Westbourne Grove, London W2. Tel: 01-229 9239. i1435, Are you recently qualified (HNC - H.TECH or DEGREE) with hands-on sandwich or work experience in both analogue and digital circuitry and electronic test knowledge and with the abil- ity to programme in `Basic'? THE EUROPEAN MOLECULAR BIOLOGY LABORATORY Then if you have the initiative to take responsibil- A Research Institute Situated in Heidleberg, West Germany, ity for the design, construction and maintenance INVITES APPLICATIONS FOR THE FOLLOWING POST: of specialised and proprietary test equipment, contact us by telephone and we will send you a SYSTEMS form, or write to us with full c.v. and an indication INTEGRATOR of your salary requirements. The successful candidate will be responsible for the conception and implementation of Microcomputer Hardware and Software for Telephone CHERTSEY 62671 use in various projects with the Laboratory such as on-line Image Personnel Department Processing and Graphic Display Systems. Systems already in use in the laboratory are based on Z80 and M68000 processors in the VME standard configuration. A Kent Industrial knowledge of these systems is desirable but not essential. The basic salary offered will be around DM3900 - monthly. Certain allowances will be payable in addition, depending on personal Measurement Limited circumstances. An initial contract of 3 years will be offered, which can be renewed. PLEASE WRITE BRIEFLY FOR AN APPLICATION FORM, Hanworth Lane, Chertsey, Surrey. QUOTING REFERENCE N.83/23T0- (2608) EMBL, PERSONNEL SECTION,

POSTFACH 10.2209, D-6900 HEIDELBERG (2617)

At H.M. Government Communications Centre we're using the very latest ideas in electronics technology to design and develop sophisticated communications systems and installations for special Government needs at home and overseas. Electronics With full technical support facilities on hand, it's an environment where you can see your ideas progress from initial concepts through prototype construction, tests and evaluation, to the pre -production phase, with a chance to Engineers influence every stage. Working conditions are pleasant, the surroundings are attractive, and the career prospects are excellent. Ideally we're looking for men and women who have studied electronics to degree level or equivalent and have had some experience of design, whether obtained at work £9561 will be made as or through hobby activities. Appointments Higher Scientific Officer (£7149-£9561) or Scientific Officer (£5682-£7765) according to qualifications and experience. Communications For further details please write to the address given below. As our careful selection process takes some time, it would be particularly helpful if you could detail your Design in qualifications, your personal fields of interest and practical experience, and describe the type of of working environment most suited to your career plans. High Tech Country The Recruitment Officer, HMGCC, Hanslope Park, Buckinghamshire MK19 7BH. 12448)

ELECTRONICS & WIRELESS WORLD JULY 1984 95

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BORED T Engineer Then change your job! Wireless Test Engineer Senior 1) Electronics £8,500 Z80 and instrumentation and telecommunications training calibration. Nets area. of vital national importance 2) Bench/Service Engineer £8,500. Hand held radio and allied communications equipment. Advanced This is an opportunity to join a team which provides the field of mobile radio and be capable of the day-to-day field. Croydon. vocational training for technical staff in the operation supervision of a small section of technical instructors and staff. The post requires an officer with a and maintenance of telecommunication equipment for administrative 3) Technical Support Engineer practice and Police Forces and Fire Brigades in England and Wales and good knowledge of telecommunication £11,000+ car. Design, test and service of for the Home Defence and Prison Services. principles, including micro -electronics, and the office automation systems. Overseas You will identify staff training requirements, develop capability of preparing and presenting courses which are travel. Berks. new training techniques, approve applications for essentially orientated towards the maintenance of coming into service 4) Test Engineer. academic training, operate to a financial budget, prepare telecommunication equipment Test and troubleshoot minis and micros. estimates, provide statistical reports and cost data on because of the World Administrative Radio Conference Berks area. Directorate of Telecommunications training and serve as (WARC) Frequency Conversion Programme. will be within Training Liaison Officer. Salary for this Stanmore-based post Service Engineer. the range L10,575 -C12,660 (including L500 Outer London Candidates should have an appropriate degree or £10,000+ car. Computerized info. + data Weighting) according to qualifications and experience. equivalent (Including overseas) qualification in retrieval systems. Training in U.S.A. SALARIES UNDER REVIEW. electronics or be suitably qualified senior technicians Middx area. MAY BE who have appropriate training and about 15 years RELOCATION ASSISTANCE AVAILABLE. Hundreds other Electronic For details and an application form (to be of experience in a related field of work and who have further and Computer vacancies to £12,500 by 13 July 1984) write to Civil Service either satisfied the CEI requirements for registration returned Phone or write: Commission, Alencon Link, Basingstoke, Hants as a Technician Engineer or hold an HNC/FTC in Roger Howard, C.Eng., M.LE.E., M.I.E.R.E. Electronics or Telecommunications. Applicants should, RG21 1JB, or telephone Basingstoke (0256) 68551 preferably be corporate members of a relevant (answering service operates outside office hours). CLIYEDEN CONSULTANTS Please quote ref: T/6252. 92 The Broadway, Bracknell, Berkshire professional institution. All candidates should have at Tel 0344 489489 least 4 years experience in the design, installation and The Civil Service is an equal opportunity 1 ,4 ), maintenance of communication systems, preferably in employer CLIVEDEN Home Office (2638)

Outstanding opportunities to move into Sales or Sales Management U.K. & Export The expansion in our markets means We are looking for men or women that we urgently need to recruit the educated to at least HNC level in following staff for key positions in the electronics who have a solid basis of direct sales staff, over five weeks annual U.K. and overseas:- practical experience. Knowledge of the leave, staff pension and free life assurance SALES ENGINEERS radio communications industry would scheme plus many other benefits TECHNICAL SUPPORT be advantageous and for overseas sales a associated with employer. ENGINEERS second language (French or Spanish) a major If you are interested please telephone AREA SALES MANAGERS would be useful. Graham Addison to find out further REGIONAL SALES If you are ambitious and are seeking details on Windsor (07535) 68101. Or MANAGERS a new challenge these opportunities will write giving full details of career and We are Racal Dana Instruments allow you to develop your career in - current salary to:- Personnel Officer high technology products and will Ltd., an international manufacturer of selling Racal -Dana Instruments Ltd., test and open up exceptional promotional paths sophisticated electronic Duke Street, Windsor, Berkshire. measurement instrumentation for the in several different areas. radio communications, ATE and We can also offer an attractive salary microprocessor based industries. package including company car for U.K. 0000(2631) Racal's people are RaCal% success

96 ELECTRONICS & WIRELESS WORLD JULY 1984

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As a candidate you will have a PRINCIPAL DESIGN degree in electronics and experience in one or more of and the following: Customised Chips, High Density PCB ATE ENGINEERS assemblies, CAD/CAM, Computer HIGH TECHNOLOGY / ATE EQUIPMENT Based Systems using Pascal/Assembler or S. ENGLAND to £16K BITE, Proprietary Test Systems eg Gen Rad, Membrain, Marconi and Hewlett Packard. To support the growth of the above mentioned engineering division our This is a first class career opportunity for a person with knowledge client also has vacancies for Engineers in less Senior positions and experience of Hi -Tech. Electronic and Automatic Test Equipment Development. Your technical nterest will be immediately captured by These important positions present a major opportunity to the the highly advanced technology now being employed. Your challenge professional engineer set to establish a career in Hi -Tech Electronic will be to integrate the product with the design of the ATE. providing and Automatic Test Equipment Design and Development. Our client innovative solutions to both design and test methodology problems. provides an attractive salary package, the possibility of travel and full company benefits, including five weeks holiday and a generous relocation package to an attractive location in S. England. From original concept you will be providing an active contribution to the design and development of systems using analogue. digital signal processing, digital data, electro-optics. infra -red and millimetnc To find out more and to attain an early interview please contact circuits and systems. You will provide a consultancy service to KEN JACOBSEN in complete confidence on Hemel Hempstead development teams on testability. BITE and ATE appl cations. (0442) 47311 during office hours or one of our duty consultants on developing test ability and methodology as applied to future and Hemel Hempstead (0442) 212650 evenings or weekends. specialised microelectronic packaging. Alternatively write to him at the address below.

EXP,cl It Iv(' Recru It ment S('I'v ices

THE INTERNATIONAL SPECIALISTS IN RECRUITMENT FOR THE ELECTRONICS COMPUTING ANO DEFENCE INDUSTRIES 25-33 Bridge Street, Hemel Hempstead, Herts., HP1 lEG. (2634)

GROUND ELECTRONICS AND TELECOMMUNICATIONS UNIVERSITY OF OXFORD Dyson Perrins Laboratory - ENGINEERSITECHNICIANS .. R.F. Electronics Earnings over 2 years not less than £23,500 (tax-free) PLUS free Engineer accommodation and meals, expert medical care, personal accident An electronics engineer with qualific- insurance PLUS 21 days' UK leave at 17 week intervals with free air travel to ations to degree or H.N.C., standards and from Heathrow. is required to develop radio frequency accessories associated with Nuclear Magnetic Resonance instruments, Applications are invited for immediate and forthcoming bachelor status working at up to 500 MHz. The ability to vacancies with our Company in the Sultanate of Oman. The work involves the contribute to software developments maintenance of modern military equipment connected with the same instruments associated with the three will be of added value. Appropriate branches of the Armed Services. experience demonstrating the ability Ideally, applicants should have a thorough knowledge of techniques and to progress the hardware develop- have ments unassisted will be expected. been employed for a minimum of 5 years' within the field of one or more Nuclear Magnetic Resonance is an of the following: mobile and static military radio systems, associated important and growing scientific and antennae and ancillary equipment; cryptographic telegraphy medical technique and this two year and appointment offers an opportunity to equipment: weapons fire control systems and navigation aids used in air gain valuable experience in this area. traffic control. The appointment will be at up to If £8530 p.a., depending on experience. you feel you are suitably qualified and interested in joining our Further particulars from and written Company, please write giving a brief summary of your qualifications and applications with the names of two ref- experience to. The Company Personnel Manager, Airwork Limited, erees to: Dr. A.E. Derome, Bournemouth-Hurn Airport, Christchurch, Dorset BH23 6EB. Dyson Perrins Laboratory, South Parks Road, Oxford. OX1 30V Tel. Oxford 59601, ext. 203. (2633)

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Product Management Engineer Electronics Audio Mixing Consoles Sony Broadcast Limited, one of the world leaders in the professional sound broadcast and recording industry, markets a complete range of technician professional audio equipment throughout Move up with the award winners. Europe, the Middle East and Africa. In addition to microphones, analogue tape machines, mixing Our winning of the Queens Award for Technology 1984 is just consoles and RF communication products, we one of our outstanding success. The company has an example are also at the forefront of digital audio enviable reputation in the marketplace and this is reflected in the calibre of staff we recruit. The Special Products Division designs technology. and builds special purpose machines for engine and fuel system An excellent opportunity has now arisen to join manufacturers worldwide. a team responsible for the product management An additional ELECTRONICS TECHNICIAN is now sought of our professional audio equipment. The -someone aged 22-35 who has served a recognised successful applicant will provide support on our apprenticeship, and has an ONC/HNC, to be involved in work of full range of mixing consoles. There will be a an interesting and practical nature, featuring assembly, wiring and combination of in-depth technical involvement testing one off PCB's, prototype machines and test rigs, followed with inter -departmental and customer liaison. up by analysis and reporting of results. 2 years relevant This will overseas travel experience is therefore essential. position also entail some The salary offered will be according to your age, experience and as required. qualifications. Applicants should be educated to HNC If you would like the opportunity of working for an award winning (Electronics), or equivalent, and have several company with a secure future please apply for an application form years experience in the professional audio from: industry. Knowledge of the operational features Rod Mitchell, Personnel Manager, of mixing consoles and experience of console Leslie Hartridge Limited, Tingewick Road, design would be particularly relevant. MK181 EF. Buckingham, Bucks. We offer attractive salaries together with first Tel: Buckingham (0280) 813661. class conditions of employment, and relocation assistance will be given where appropriate.

1f interested, please contact: Mike Jones, artridge Senior Personnel Officer, Sony Broadcast Ltd.. A Lucas Company(2630) City Wall House, Basing View, Basingstoke, Hants. RG212LA. Tel: (0256) 55011

Sony Broadcast Ltd. City Wall House Basing View, Basingstoke SONY Hampshire RG21 2LA Power Supply Broadcast Telephone (0256) 55011 (2619) Development Engineer Negotiable Salary Coventry THE PAPUA NEW GUINEA UNIVERSITY OF TECHNOLOGY ELECTRONIC SERVICE UNIT CHIEF TECHNICAL OFFICER (COMPUTING) in the expanding new telecommunications Our sustained growth Applications are invited for the above position, which becomes is technology - combining voice, data and video services, vacant at the beginning of 1985. creating some exceptional opportunities, at the Company's Duties include planned maintenance and repair of an extremely Headquarters in Coventry. . wide range of electronic equipment, upkeeping of servicing records, Applicants must have at least two years' experience in the field advisory service to academic staff, supervision of technical staff, and training of Technical Officer trainees. of Switch Mode Power Supply design or in a related field where The Electronic Service Unit is housed in recently enlarged of closed loop he/she has acquired a sound understanding air-conditioned quarters, and has a wide range of modern test control theory and/or magnetics, will be an advantage. equipment. Computer facilities are available. The successful candidate must be able to work as a member of Applicants should be qualified to Technician Engineer level and a small team and make a real contribution to the development of should have substantial experience of electronic workshop technique high frequency power supplies to customer specifications. and management. Experience with microprocessor -controlled equipment and microcomputers would be an advantage. We're offering excellent negotiable salary, dependent upon Salary: Chief technical Officer (Computing) K20,520 per annum qualifications and experience, plus the usual big company (K1 = Stg 0.8177) (Level of appointment will depend upon qualifications benefits. and experience). The initial contract period is for approximately three years. Other may be available where Assistance with relocation expenses benefits include a gratuity of 24% taxed at 2%, appointment and appropriate. repatriation fares, leave fares for the staff member and family after 18 Interested? Then please write enclosing a brief C.V. to Joan months of service, settling -in and settling -out allowances, six weeks Thorpe, Personnel Department, GEC Telecommunications paid leave per year, education fares and assistance towards school fees, free housing. Salary protection plan and medical benefit schemes are Ltd, P.O. Box 53, available. Coventry Detailed applications (two copies) with curriculum vitae, CV3 1HJ. (2627) together with the names and addresses of three referees and indication of earliest availability to take up appointment should be received by: The Registrar, Papua New Guinea University of Technology, Private Mail Bag, Lae, Papua New Guinea by 30 July 1984. Applicants resident in the United Kingdom should also send one Telecommunications copy to the Association of Commonwealth Universities (Appts), 36 Gordon Square, London WC1 H OPF, from whom further information may be obtained. (2618)

98 ELECTRONICS & WIRELESS WORLD JULY 1984

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ARTICLES FOR SALE Advanced ® PERFECTION ASSURED telecommunications: FLOPPY DISKS MEET ANSI, DIN, ECMA, IBM, careers with extensive scope at Cheltenham JIS AND SHUGART SPECIFICATIONS. Join the Government Communications Headquarters, EVERY DISK IS CERTIFIED AND one of the world's foremost centres for R & D and produc- GUARANTEED TO BE 100% tion in voice/data communications ranging from HF to MINI FLOPPY DISK satellite - and their security. Some of GCHQ's facilities ERROR FREE. are unique and there is substantial emphasis on creative Sr DISKETTES PRICE PER solutions for solving complex communications problems Certified for Single OR Double QUANTITY DISC using state-of-the-art techniques including computer/ Density media with hub ring 1-10 10-40 50-90100+ MD1-S/S 48 tpi 1.61 117 112 1.05 microprocessor applications. Current opportunities are PRICES EXC VAT for: MD1-D S/S 48 tpi 1.70 1.23 1.17 1.10 MD2-D D/S 48 tpi 2.00 1.44 1.37 1.29 40 tpi suitable for 40 track MD1-DDS/S 96 tpi 1.86 1.41 1.35 1.28 Telecommunication 96 tpi suitable for 80 track MD2-DD D/S 96 tpi 2.33 1.76 1.68 1.60 PBOXOF10 VIDEO TAPES PLEASE SEND £2 Technical Officers FORBOXOFTEN- Two levels of entry providing two salary scales: VHS E-180 £35.00 ANY QUANTITY £6262-£8580 & £8420-£9522 ABeta FORNEXTD10 Minimum qualifications are TEC/SCOTEC in Electronics/ L-750 £38.00 £5 FOR NEXT DAY Telecommunications or a similar discipline or C & G Part DELIVERY.

Il Telecommunications Technicians Certificate or Part I C10cat plus Maths B, Telecommunication Principles B and either 10 Radio Line Transmission B or Computers B or equivalent: Computer minutes £23.00 C15 15 minutes £24.00 ONC in Electrical, Electronics or Telecommunications En- Cassettes C20 20 minutes £25.00 gineering or a CIE Part I Pass, or formal approved Service technical training. Additionally, at least four years' (lower High quality low noise cassette tapes. Short play, leaderless level) or seven years' (higher level) appropriate exper- construction for use with computer cassette systems. Each tape ience is essential in either radio communications or radar, in individual plastic library case with index card. data, computer or similar electronic systems. At the lower entry level first line technical/supervisory control of HOW TO ORDER For disks all 50p per box of ten for p&p. First technicians involves "hands-on" participation and may class mail for small packets - next day delivery for heavier involve individual work of a highly technical nature. The ones. For cassettes allow £5 carriage costs (min order is 100) for higher level involves application of technical knowledge next day elivery. Post/carriage costs include VAT. and experience to work planning including implementa- tion of medium to large scale projects. P. V. TUBES PLE5BVAT TOALL PRICES Telephone: Dept. E (0254) 36521 Radio Technicians - 104 ABBEY STREET, (0254) 32611 visa ACCRINGTON, LANCS BB5 1 EE. £5485-£7818 Telex: 635562 Griffin G for PV Í To provide all aspects of technical support. Promotion í262H prospects are good and linked with active encouragement to acquire further skills and experience. Minimum qualifi- cations are a TEC Certificate in Telecommunications or equivalent plus two or more years' practical experience. TO MANUFACTURERS, WHOLESALERS Cheltenham, a handsome Regency town, is finely en- dowed with cultural, sports and other facilities which are BULK BUYERS. ETC. equally available in nearby Gloucester. Close to some of LARGE QUANTITIES OF RADIO. TV AND Britain's most magnificent countryside, the area also offers reasonably priced housing. Relocation assistance ELECTRONIC COMPONENTS FOR DISPOSA may be available. SEMICONDUCTORS, all types, INTEGRATED CIRCUITS, TRANSISTORS, DIODES, RECTIFIERS, THYRISTORS, etc. RESISTORS, C/F, M/F, W/W, etc. CAPACITORS, SILVER MICA, POLYSTYRENE, C280, C296, DISC CERA- For further information and your application form, please MICS, PLATE CERAMICS, etc. telephone Cheltenham (0242) 32912/3 or write to: ELECTROLYTIC CONDENSERS, SPEAKERS, CONNECTING WIRE, CABLES, SCREENED WIRE, SCREWS, NUTS, CHOKES, TRANSFOR- MERS, etc. ALL AT KNOCKOUT PRICES - Come and pay us a visit ALADDIN'S CAVE TELEPHONE: 445 0749/445 2713 Recruitment Office, Government Communications Headquarters, R.HENSON LTD. Oakley, Priors Road, Cheltenham, 21 Lodge Lane, North Finchley, London, N.12 15 minutes from Tally Ho Corner) (16131 Gloucestershire, GL52 5AJ. 12452)

QUARTZ CRYSTALS OSCILLATORS AND FILTERS of all types. Large stocks of standard ARTICLES FOR SALE items. Specials supplied to order. Personal and export orders welcomed - SAE for lists please. BRIDGES waveform/transistor analysers. Cali- OEM support thru:- design advice, prototype Crystal brators, Standards. Millivoltmeters. Dynamome- quantities, production schedules. HI-FI REVIEWING ACCURATE ters. KW meters. Oscilloscopes. Recorders. Sig- Colledge Electronics. Merriott, Somerset TA16 I need a young person to help me test hi-fi Tel: 73718 RELIABLE nal generators - sweep, low distortion, true products, during June, July and August 1984. INS. 0460 (2612) RMS, audio, FM, deviation. Tel. 040 Pay - around £80/wk. You must have an 376236. (1627) interest in hi-fi and music, a knowledge of electronic principles and minimum qualific- ations of O Levels in a science subject and English. Central London location (Padding- 2764 EPROM25ONS £5.65 Zvtnniep Zlmeß ton). Phone/write: NOEL KEYWOOD, 64 Private enpuuæs send t 3r m st3rnps ror brornure FREE Mail Order newspaper of Castellain Road, Maida Vale, London W9 Bargains. Relays; Diodes; Thyris- 1EX. 01-289 3533 FD1771 FOC £17.50 THE QUARTZ CRYSTAL CO. LTD. tors; Capacitors; Resistors; Bridge (2635) s1.C.C. WORKS, WELLINGTON CRESCENT Rectifiers; Cable Straps; High +75pP&P+VAT NEW MALDEN. SURREY 01-942 0334 & 2950 Speed Fuses and Mechanical Components. PREMIER MICROSYSTEMS LTD. (8493) Harehill, Todmorden, Lancs. OL14 5JY 208 CROYDON RD PCB HAND ASSEMBLY quantity. SHEETMETAL FOLDERS 18% x 18G, Tel. Todmorden (STD 070 681) 4931 -any LONDON SE207YX (2530) Highest quality at sensible prices. INTER- 01-6597131 (2538) Vice or Bench model. £38. Leaflet, 01-890 ESTED? Phone 01-274 3070 (2570) 7838 Anytime. (2569)

100 ELECTRONICS & WIRELESS WORLD JULY 1984

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COMMUNICATION RECEIVERS HNC Electronics? RACAL SOOKC/S TO 30MC/S IN 30 BANDS 1 MC/S WIDE - RA17 MKII 2125 RA17L £ 150 RA117E f 225 NEW METAL LOUVRED CASES FOR ABOVE STS. ALL RECEIVERS ARE AIR TESTED AND CALIBRATED IN OUR WORKSHOP. SUP- PLIED WITH DUST COVER - OPERATION INSTRUCTIONS See yourself in video? - CIRCUIT - IN FAIR USED CONDITION RACAL SYN- THESISERS (DECADE FREQUENCY GENERATORS) MA350BSOLID STATEFOR USE WITH- MA79-RA217- If you're a qualified electronics technician, keen on video, RA1218. ETC. - £100 to £150 MA250 - 1.6MC/S to 31 6MC/S £100 MA1350 - FOR USE WITH RA17 and want to work in the world of video production, talk to RECEIVER - £100 to £150 MA259G- PRECISION FRE- QUENCY STANDARD SMC/S-1 MC/S - 100KHZ - £100 to £ 150 PANORAMIC ADAPTOR RA66 £ 150 RA137 IF CON- Unipart. VERTOR - 10 TO 980KC/S - £75 - RA218 INDEPENDENT SST! UNIT - £50 - RA153 AND RA 253 TWIN-CHANNEL We keep all our customers and staff in the pictureabout RECEIVER - 1 TO 30 MC/S - THIS IS VIRTUALLY TWO RA117s IN ONE CASE £150 to £200 RA1218 SOLID STATE RECEIVER WITH ELECTRONIC FREQUENCY DISPLAY TO promotions, news, training etc. through our own exciting 10HZ - FREQUENCY 1 TO 30 MC/S - £500 RA6217 - RECEIVER SOLID STATE - COMPLETE WITH SEPARATE Channel 5 video communications package. SYNTHESISER - INCLUDES FM - A VERY HIGH -GAIN, SENSITIVE AND EXTREMELY STABLE RECEIVER - NORTH AMERICAN RACAL MADE £400 RA337 LP CON- Right now we need two technicians to back up our VERTOR 3 TO 980KHZ FOR USE WITH SOLID STATE RECEIVERS - £150 EDDYSTONE COMMUNICATION production team in our studios and on location. You'll RECEIVERS - EC958 - SOLID STATE - HIGH STABILITY - 100KHZ TO 30MC/S £350 to £400 - EC964RO - SOLID carry out routine maintenance and emergency repairs in a STATE- SINGLE CHENNEL -SBB-MAINS OR BATTERY - 1.6 TO 27 5MC/S AND 400 to 535KHZ £100 WITH 2 -camera studio, 3 -machine editing suite, and a fully - MANUAL PLESSEY PR1556 SOLID STATE 60 KC/S - 30 MC/S £400 REDIFON SSO RECEIVER - R499 - SOLID equipped A/V theatre, photo studio and record library. STATE - 10 FIAFO CHANNELS - RANGE 1 5 TO 30MC/S AND 255KHZ TO525KHZ - MAINS OR BATTERY - COM- PLETE WITH IVA ADAPTOR ARU10A - £100 WITH Location shooting and some setting up of presentation MANUAL CREED 75 TELEPRINTERS - FITTED TAPE PUNCH AND GEARBOX FOR 50 AND 75 BAUDS- 110VOLT equipment on -site will be required. AC SUPPLY - IN ORIGINAL TRANSPORT TRAY SEALED IN POLYTHENE - LIKE NEW - £15 EA. REENFON TT11 AUDIO TELEPRINTER CONVERTOR RECEIVER SOLID STATE If you have an HNC or equivalent in electronics, some - SUPPLY 110 DR 240 AC - MADE FOR USE WITH ABOVE TELEPRINTER ENABLING PRINT-OUT OF MESSAGES knowledge of video techniques and equipment and, RECEIVED FROM AUDIO INPUT OF COMMUNICATION RECEIVER - £15 WITH CIRCUIT TESTED. REMFON TT10 essentially, a strong personal interest in electronics, we will CONVERTOR AS ABOVE BUT INCLUDES TRANSMIT FACI- ...... LITIES - £20 OSCILLOSCOPES - STOCKS ALWAYS provide a competitive salary and comprehensive CHANGING -SELAB'S111 SOLID STATE - 1BMC/S £1751 COSSOR COU150 - 35MC/S £200 TELEOUIPMENT 075 - benefits. 5oMC/S £300 TEKTRONIX 485 - 100MC/S £1000 SOLARTRON CD1740 - 50MC/S £300 TEKTRONIX MAIN FRAME TYPE 7704 £750 7504 £600 77040 £1000 FM Please write, initially, for an application form to: RECORDER SANRHM0 SABRE 111 14 CHANNELS £350 uNi TRANSTEL MATRIX PRINTERS - AFTYR - 5 -LEVEL BAU - Ian Wells, Personnel Manager, Unipart International, DOT CODE - UP TO 300 BAUDS - FOR PRINT-OUT ON PLAIN TELEPRINTER PAPER £50 to £100 TRANSTEL AHIIR AS ABOVE BUT ALSO 8 -LEVEL ASC11 (CCITT NO. 2 Unipart House, Cowley, Oxford OX4 2PG. AND CCITT NO. 5) LIKE NEW £200 ARMY FIELD TELE- PHONE SETS, TYPE F - L AND J - LARGE QUANTITY IN STOCK £6 TO £15 DEPENDING ON TYPE AND QUANTITY (2629) AVAILABLE P O.R DON 10 TELEPHONE CABLE HALF - MILE CANVAS CONTAINERS - £20 NIGHT VIEWING INFRA -RED AFV PERISCOPES - TWIN EYEPIECE - 24 - VOLT DC SUPPLY -£100 EA - ORIGINAL COST TO GOV- ERNMENT OVER £11,000 EA. STATIC INVERTORS- 12 o r 24 -VOLT INPUT - 240 -VOLT AC SINEWAVE OUTPU- - VARIOUS WATTAGES P O.R. XY PLOTTERS AND PEN RECORDERS VARIOUS - P.O. R. FERROGRAPH SERIES 7 TAPE RECORDERS MONO £100 - STEREO £150 LOW - NOISE AMPLIFIERS - 500MC/S TO 40G/CS IN VARIOUS

RANGES MADE BY WATKINS JOHNSON, 110- OR 240 - VOLT MAINS INPUT £25 TO £50 SIGNAL GENERATORS VARIOUS - TF995/A3 £80 TF 2015 10MC/S-510MC/S AM and FM. £675 TF 801D-85 10-485 MC/S £100 TF144H £100 TF1060/2 £75 HP606A AND 8- £100- B£150 HP608 £100 HP614A £100 HP618B £100 H P620A £ 100 TELONIC SIA/2000SWEEP GENERATORS L3 Instrument Service Engineer and L5 PLUG -INS 4 TO 75MC/S £60 TELONIC SWIEEP GENERATORS 2003 - 850 TO 2150MC/S £275 TF1313 BRIDGE £100 TF791 DEVIATION METER £100 TF893A POWER METER £50 AERIAL MAST ASSEMBLY 30FT. NIGH COMPLETE WITH 16FT WHIP AERIAL TO MOUNT ON -OP -GUYROPES- INSULATORS - BASE AND SPIKES. ETC for a key role in new ideas and technology - IN HEAVY-DUTY CARRYING BAG - NEW - £30 RACAL FREQUENCY COUNTER TYPE 836 £50 TEKTRONIX PLUG -INS - 1 0 1 £50. 102 £ 40. 104 £ 10O. M £ 50 £10,000: Beckenham, Kent All Terns are bought mrect Isom H M Government Item, newn

Tent cere ex -works 5 A C lore Tu es P.none lor appommnent.

CARRIAGE EXTRA -.- to join the Wellcome Foundation Limited, a major group of chemical and pharmaceutical EXPORT TRADE AND QUANTITY DISCOUNTS GIVEN JOHN'S RADIO companies with headquarters in the UK and a turnover close to £700m. WHITEHALL WORKS, 84 WHITEHALL ROAD EAST BIRKENSHAW, BAADFORO BDII TER As site based Instrument Service Engineer, you would become a key member of the Instru- TEL: (02741684007 ment Maintenanceteam group it is WANTED REDUNDANT TEST EOUIPMENT RE- fora of engineers whose responsibility to provide an adv- CEIVING AND TRANSMITTING EQUIPMENT VALVES, anced electronic and precision mechanical engineering capability to the company. PLUGS SOCKETS SYNCHROS, ETC. 1848) This is a most unusual job and we believe you will have to be an unusual person to succeed in it. You will need a very broad range of experience and ability, and be able to mend a much needed analogue recorder, yet tomorrow have the ability and enthusiasm to switch your attention to helping out a scientist with his/her broken computer controlled spectrometer. Six -channel chart recorder with six colour facility. £59. Twin pen recorder with semi -conductor Aged around 30, you should have a qualification in Electronics or Instrument Maintenance- amplifiers 2mV-20.V.,11 ranges £98. Variable AC, PSU, two meters 25A, 50v., transformer :so- such as the City and Guilds Full Technical Certificate - together with 5 to 10 years' experience lated£69. Decade capacitance box, precision 1.11 servicing electronic equipment. knowledge of modem electronic instruments and their con- total microfarads £A9. Low-ohms meter £29. Sweep generator. Signal Generator. Stab. psu s. struction and an understanding of the electronics interface with computers is essential. Teleprinter. Lab microscope, £89. 6.v-83A rechargeable batteries (make portable search- We offer a competitive salary, depending on experience and ability. Excellent benefits include lights) ¡Sea. FM/AM Generator. Tektronix Cali- five weeks' holiday, pension and life assurance scheme and generous assistancewith reloca- brator. Fibreoptic light supply (variable intensity). Centrifuge. Infra -Red Gas Analyser. 50KV variable tion expenses as appropriate. stabilised EHT supply. Tektronix Waveform Gen- erator. Rye Megohmmeter. N Sweep Generator. Water Conductivity Meter. Akratork Torque Guage. Video Oscillator. 7-track portable recor- der. Record 4" chart recorder £49. Single to 3 -phase converter. Dissolved oxygen meter. NiCad charger. FM/AM Modulation Meter. etc. Please write enclosing a full CV and quoting ref. WRL/276, to: A. Murdoch, Personnel Officer, The Wellcome research Laboratories, Beckenham, Kent 0403-76236. BR3 3BS. (2613) (2016) Wellcome ELECTRONICS & WIRELESS WORLD JULY 1984 101

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V.D.US FOR SALE Data General DGC - 6012 FOR THE BEST PCB SERVICE ARTICLES FOR SALE RS232 V24/current loop 110-4800 baud. Qwerty CAPACITY AVAILABLE and numeric keypad ideal for interfacing with mic- AVAILABLE ros useful in test equipment. Give away prices £70-£125. Phone 01-866 2871 (2611) *Circuit Design & Deveiepment TW ELECTRONICS LTD Digital and Analogue OPTOELECTRONICS WAVEGUIDE, Flanges and Dishes. All stan- Layout dard sizes and alloys (new material only) from Artwork DATA BOOK 1984 THE PCB ASSEMBLERS PCB artwork layout and mechanical detailing. P.O. stock. Special sizes to order. Call Earth Stations, investi- approved standard. by Texas £6.00 01-228 7876, 22 Howie Street, London SW11 More and more companies are Price a profes- 4AR. (2099) gating the advantages of using *Board Manufacture DIGITAL ELECTRONIC CIRCUITS sional subcontractor. Such an undertak- Prototype to semi-production, excellent rates. ing requires certain assurances. & SYSTEMS by N.M. Morris *Wiring & Assembly PRICE: £5.45 TW are able to satisfy all of them - PCB assembly, wiring and cable forming. Flow solder- When replying to classified quality, competitive pricing, firm delivey ing facilities available. MICROELECTRONICS: and close co-operation with the cus- A PRACTICAL INTRODUCTION by readersare *Test advertisements, tomer. Full test facilities available. R.A.Sparkes PRICE: £8.50 Assembled boards at 100% inspected recommended to take steps before flow soldering and reinspected One or all services available. SOLDERING IN ELECTRONICS by after automatic cropping and cleaning. Please telephone Chelmsford R.J. Klein Wassin Wassink PRICE: £51.00 to protect their interests (0245) 357935, or write to HCR Every batch of completed boards is is- Electronics, The Industrial Unit, with a of confor- Parker Road, Chelmsford. OPTICAL FIBER COMMUNICATIONS before sending money sued signed certificate (30mins from Liverpool Street St.l (1169) BY G. Keiser PRICE: £9.50 mity and quality - our final assurance. (2519) For further details, contact us at our new DIGITAL IMAGE ANALYSIS works: PRICE: £26.00 SPECIALISED SUB CONTRACT SERVICES by S. Leviald: Blenheim Industrial Park SEMI -CUSTOM IC DESIGN & VLSI Bury St. Edmunds Custom Design - Assembly - 1P33 3UT by P.J. Hicks PRICE £13.50 WANTED Suffolk Testing of VHF and UHF equipment: Telephone: 0284 3931 (1466) Cable Television, Communication INTRODUCTION TO MOS LSI Equ., Filters, amplifiers etc. Contact: DESIGN byJ. Mayor PRICE: £18.50 FREE PROTOTYPE of the finest quality with designed by us. Compe- HANDBOOK OF BATTERIES & WANTED EVERY P.C.B. artwork high standard of work. JT ELECTRONICS LTD., FUEL CELLS by D. Linden PRICE: £63.00 titive hourly rates, and Halstead (0787. Test equipment, receivers, Halstead Designs Limited. Tel: Unit C4, Industrial Estate.. 477408. 2126 THE DESIGN & DRAFTING OF valves, transmitters, com- Button End, Harston, PRINTED CIRCUITS by D. Lindsey PRICE: £41.50 ponents, cable and Cambs. CB2 5NX. electronic scrap and quan- SERVICES Tel: (0223)871 239 PRICES INCLUDE Ref. 3575 * ALL and Tlx: 21792 (2623) POSTAGE tity. Prompt service * cash. Member of A.R.R.A. PROM, EPROM & PLA Programming service from original DESIGN SERVICES. Electro. design de- THE MODERN or list. Most devices catered velopment and production service available for M&B RADIO device digital and analogue instruments. RF Transmit 86 Bishopsgate Street for. Charges £2.25 per copy + 5p ten and receivers, telemetery and con rol BOOK CO. Leeds LS1 4BB per 16 bytes manually entered. systems. 20 years' experience. R.C.S. Electronics, Appreciated. Wolsey Road, Ashford, Middlesex. Phone Mr BRITAIN'S LARGEST STOCKIST 0532 435649 VAT extra. S.A.E. Falkner 53661. (8341 of British and American 199561 M.GAFFNEY P.C.B.s & PANEL LABELS to your require- Technical Books ments. Design - Prototypes - Production. 17 Solway Close, Fearn head, G. N. SLEE CUSTOM PRODUCTS, 78 Derry 19-21 PRAED STREET Warrington WA2 OUR. (2622) Grove, Thurnscoe, Rotherham, Yorks. S63 OTP. Telephone: (0709) 895265. (2401 LONDON W2 1 NP VERBGATE LTD. Telephone: 01-402 9176 We buy large and small par- ANALOG COMPUTERS LIMITED chartpak Closed Saturday 1 p.m. I/C, stockist Please allow 14 days for cels of surplus transistors, CAPACITY NOW AVAILABLE FOR: reply or delivery capacitors and related 122451 electronic stock. Immediate Design & Development, Complete Artwork Service, Camera settlement Work, Prototype thru to Production PCB Manufacture/Assy. ENCAPSULATING EQUIPMENT FOR.coils, Tel: 01-208 0766 transformers, components, degassing silicone Telex: 8814998 5 Cork Street, Eccles, Maidstone, Kent, ME20 7HG rubber, resin, epoxy. Lost wax casting for brass, (24781 bronze, silver, etc. Impregnating coils, transfor- TELEPHONE 106221 79987 TELEX 965633 (23481 mers, components. Vacuum equipment, low cast, used and new. Also for CRT regunning metallis- ing. Research & Development. Barratts, Mayo Road, Croydon CR0 2QP. 01-684 9917. (9678) STEWART OF READING CIRCOLEC MORSE READING PROGS.Work on clean sig- 110 WYKEHAM ROAD THE COMPLETE ELECTRONIC SERVICE nals without hardware interface. ZX81 1K UNEX- READING RG6 1PL Artwork, Circuit Design, PCB Assembly, Test & Repair Service, Q.A. PANDED MEMORY. Translated code with word TEL NO: 0734 68041 Consultancy, Prototypes, Final Assembly. Full PCB Flow Soldering and line spaces for easy reading Automatic scroll Service. action. £7 incl. PRICES PAID FOR SPECTRUM 16/48K. Scroll action with 10 -page TOP Quality workmanship by professionals at economic prices. scrolling memory, instantly accessible page by ALL TYPES OF SURPLUS Please telephone 01-646 5686 for advice or further details. page. £8 incl. All types variable speeds. Feed TEST EQUIPMENT, MANOR signal direct into EAR socket. Pinehurst Data COMPUTER EQUIPMENT, TAMWORTH Studios, 69 Pinehurst Park, West Moors, WIM- COMPONENTS etc. 302-310 COMMONSIDE EAST, MITCHAM BORNE, Dorset. BH22 OBP. (2532) ANY QUANTITY. (2616) (1391) PRINTER FOR BBC MICRO or any computer DESIGN AND MANUFACTURE. ANALOGUE, with RS232 interface. 18OCPS. Bidirectional Feat rv,c DIGITAL, RF AND MICROWAVE CIRCUIT AND printing. Dot matrix 7X9. True descenders. Buf- * 4 "T SYSTEM DESIGN. Also PCB design, mechanical fered. Various baud rates. Variable tracktor set- A o:rk C4rnpettvive design and prototype/small batch production. - Ad- tings. Ideal for users requiring fast continuous SURPLUS enmote Limited, 27 Longshot Estate, Bracknell, printing. Cables and plugs included. £80. Phone: We offer good prices for test equipment, Berks. Tel: Bracknell (0344) 52023. (656) Crowthorne (0344) 776894. (2610) components, redundant computers, PCB's connectors. Immediate settle- DESIGN AND DEVELOPMENT SERVICE. RF ment. %e03B6-832152J transmitters and receivers. Telemetery U.H.F. V.H.F. Anologue and digital circuits, control sys- TIMEBASE tems. Full manufacturing facilities. RCS Electron- Phone Dr. Eric VIDEO &TVTESTEQUIPMENT(PAL) 94 Alfriston Gardens 49IWastb ics, Wolsey Road, Ashford. Middx. WilliemsP.C.B.Artwork, (2637) PHILIPS Sholling, Southampton SO2 8FU ppqqHoneybourne, Evesham, Wores, WR11 SPT. Falkner on 53661. monitor £750 LDH620014' colour Telephone: 10703) 431 323 II:lIIIINN SMALL BATCH PCBs, produced from your art- PM5519 pattern generator £500 1832) work. also DIALS, PANELS, LABELS. Camera (2537) TURNAROUND. De- SYSTEM VIDEO work undertaken. FAST tails: Winston Promotions, 9 Hatton Place, London i. etc. into 1204A & 1205 waveform & colour TURN YOUR SURPLUS cs transistors ECIN 8RU. Tel. 01-405 4127/0960. (9797) analysers(1 unit) £2100 cash, immediate settlement. We also welcome the opportunity to quote for complete factory clear- DIGITEL ance. Contact COLES -HARDING & CO. 103 D4060-01 noise meter £480 WANTED The Publishers take all South Brink, Wisbech, Cambs. 0945 reasonable care to ensure that All 18mths old. For details SURPLUS ELECTRONIC 584188. (9509) HI-TEST, 64 classified advertisements are write/phone- COMPONENTS AND SERVICE. Ana- Castellain Road, London W91 EX. PROFESSIONAL DESIGN genuine, but readers must satisfy EQUIPMENT lopue/RF circuit/System design. Specialising in tel: 01-289-3533. (2636) and network themselves that they will be the opportunity to quote for microwave amplifier, oscillator We also welcome 6805/6809 series micropro- what they require complete factory clearance design. MOTOROLA obtaining cessor design/development capability. All work before entering into transactions, B. BAMBER ELECTRONICS by competent profes- VALVES, PROJECTOR Lamps, 6000 types, list carried out to a high standard 5 STATION ROAD, LI1TLEPORT, CAMBS. sional engineers. Trontech Electronics Design particularly if they involve large 75p, world wide export. Cox Radio (Sussex) Ltd., Phone: Ely 860185 10.531 Services, 81 Finchampstead Rd, Wokingham, sums of money. . 2519) The Parade, East Wittering, Sussex. Phone (024 (2483) 366)2023. (1991) Berkshire. Tel: 0734 790103 (2439) 1984 102 ELECTRONICS & WIRELESS WORLD JULY

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www.americanradiohistory.com 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 range that repre- sents the best value for money available anywhere. V-212 20MHz Dual Trace V-209 20MHz Mini -Portable V-222 20MHz (illustrated) V-509 50MHz Mini -Portable V -203F 20MHz Sweep Delay V -1050F 100MHz Quad Trace V -353F 35MHz Sweep Delay V-134 10MHz Tube Storage V-422 40MHz Dual Trace VC-6015 10MHz Digital V -650F 60MHz Dual Timebas'e VC -6041 40MHz Digital

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INDEX TO ési1d ADVERTISERS Appointments Vacant Advertisements appear on pages 91-103

PAGE PAGE PAGE A&H Supplies 6 Gemini Marketing Ltd 42, 43 Radford Electronics 36 Airlink Transformers Ltd 20 Global Specialities 21 Radiocode Clocks 1 AM Electronics 86 GP Industrial Inside Front cover. Radio Components specialists 60 Analogue Devices 53 Outside Back Cover Radio Society of Great Britian 70 Armon Electronics 36 Grandata Ltd 84 Ralfe Electronics P, F, 82 Aspen Electronics Ltd 68 Greatech Electronics 16 Research Communication Ltd 20 Robot (UK) Ltd 8 RST Valve 90 Happy Memories 10 B.BamberElectronics 60 Hams Electronics London 20 Barlec Richfield Ltd 24 Harrison Bros 44 Barrie Electronics Ltd 42 Hart Electronics Kits Ltd 86 36 Sherwood Data Systems 92 Beckenham Peripherals Hawke Electronics Ltd 44 Black Star 48 Sowter Ltd E.A. 84 Henrys Audio Electronics 68/69 South Midland Communication 68 Henson(R) 68 Special Products Distribution 54 House of Instruments 21 Cambridge Kits 48 Strumech Engineering 10 Carston Electronics 20 Stewart of Reading 42 Surrey Electronics Ltd 6 Control Universal Ltd 8 ILP Electronics 48 Cricklewood Electronics 30 Crotech Instruments 89 Langrex Supplies Ltd 90 Taylor Bros 36 Levell Electronics 92 Technomatic Ltd 4/5 Dataman Designs 35 Techtest Ltd 44 Display Electronics 88 Thander Electronics Ltd 54 MB Radios 82 Thanet Electronics 70 80 Micro Concepts Thorn EMI Instruments 77 86 48 Easibind Minim Electronics Thurlby Electronics 86, 104 Electronics Brokers 11, 13, 15 Electrovalue 80 EMS Manufacturing 54 Newnes Technical Books (C Butterworths) 6 Electronics Wireless World Editorial feature .. 70 Valradio Power Ltd 15 Electronics Wireless World Pliers offer 89 Opus Supplies 59, 63 Vigilant Communication 24

Farnell Instruments 1 Foundrometers Ltd 15 Pantechnic 82 Whiteley Electronics 84 Future film Developments 6 PM Components 78/79 Wings Appeal 80 Fylde Electronics Ltd 8 Pye Unicam Inside Back Cover Wye Winding Co 10

Japan: Mr. Inatsuki, Traoe Media - IBPA (Japan), 8.212. Jack Mantel, The Farley Co., Suite 650, Ranna Building, OVERSEAS ADVERTISEMENT AGENTS Cleveland, Ohio 4415 Telephone 1919. Veat, Azabu Heights, 1-5-10 Roppongi, Minato-ku, Tokyo 106. - 1216)621 France & Belgium: Norbert Hellin, 50 Rue de Chemin Ray Rickles, Ray Rickles & Co., P.O. Box 2028, Miami Beach, F-9100, Boulogne, Paris. Telephone: 103)585 0581. Florida 33140 - Telephone (305) 532 7301. Tim Parks, Ray Rickles & Co., 3116 Maple Drive N.E., Hungary: Ms Edit, Bajusz, Hungexpo Advertising Agency, 7432. United States of America: Business Press Inter- Atlanta, Georgia 30305. Telephone (404) 237 Budapest XIV, Varosliget. Jay Feinnan, Mike Business Press 15055, national Ltd, 205 East 42nd Street, New York, NY 10017 - Loughlin International, Telephone: 225 008 - Telex: Budapest 22-4525 Memorial Ste 119, Houston, Texas 77079 Telephone (713) Telephone 1212) 867-2080 - Telex: 238327. - INTFOIRE 783 8673. Jack Farley Jnr., The Farley Co., Suite 1584, 35 East Walker Drive, Chicago, Illionois 60601 - Telephone 1312163074. Canada: Colin H. MacCulloch, International Advertising Italy: Sig C. Epis, Etas -Kompass, S.p.a. - Servizio Estero, Victor A. Jauch, Elmatex International, P.O. Box 34607, Los Consultants Ltd., 915 Carlton Tower, 2 Carlton Street, Via Mantegna 6, 20154 Milan. Angeles, Calif. 90034, USA - Telephone (213) 821-8581 - Toronto 2 - Telephone 14161 364 2269. Telephone: 347051 - Telex: 37342 Kompass. Telex: 18-1059. * Also subscription agents.

Printed in Great Britain by 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. Business Press International 1984. Wireless World can be obtained abroad from the following: AUSTRALIA and NEW ZEALAND: Gordon & Gotch Ltd. INDIA: A. H. Wheeler & Co. CANADA: The Wm. Dawson Subscription Service Ltd., Gordon & Gotch Ltd. SOUTH AFRICA: Central News Agency Ltd.: William Dawson St Sons (S.A.) Ltd. UNITED STATES: Eastern News Distribution Inc., 14th Floor, 111 Eighth Avenue, New York, N.Y. 10011.

104 ELECTRONICS & WIRELESS WORLD JULY 1984

www.americanradiohistory.com Here's all the help you need Philips versatile PM5109 LF further benefits. In addition, there is Fully automatic operation means generator and unique combined a choice of low -distortion or fast - that all you do is connect the input, distortion meter/oscillator, the settling modes. select the test frequency - and then PM 6309, give you all the help you read-out the distortion. Separate need for HiFi and audio service PM 6309 is a simple -to -operate two -channel testing is also possible applications. They're easy to distortion meter that can handle all for stereo equipment. operate - and economically priced. types of audio equipment. It has been specially designed to provide Use the inquiry service to obtain PM 5109 brings together all the high appropriate signal generation plus further information. technology features you require an accurate distortion measuring from a test instrument. It offers capability within a single instrument. Inquiry No. symmetrical or asymmetrical PM 5109 LF generator 74 outputs; pure sine wave signals; a It offers a built-in RC oscillator, total PM 6309 distortion meter 75 wide 10 Hz -100 kHz frequency harmonic distortion (THD), 3rd range and switchable output harmonic distortion and rms impedances. A high 30 Vpp measuring facilities. It not only amplitude in the asymmetrical measures distortion according to Philips Test and Measuring mode, with stepped and continuous DIN 45500 - but also determines the Pye Unicam Ltd York Street, Cambridge CB1 2PX attenuation; a 10 Vpp floating output distortion figure accurately when Tel (0223) 358866 Telex 817331 in the symmetrical mode, and useful unstable audio signals are being TTL or DIN loudspeaker outputs are applied. GN13

Test & Measuring Instruments PHILIPS

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MBM2732 MBM2732A MBM2/64 2/581 2816 MBM27C64 2716 2732 MBM27128 2815 MBM27C256 AM2716 A M2732 AM2764 AM27128

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