+or ,Are- °el* e 4fr/r 11101eir, /or 1R IOW ao. 4110 4 ANON luteI. Instruments for IEEE 488 Novel sub -woofer AS 3.30 Italy L 4200 OKL 38.00 Spain Pis. 370.00 DM ... 7:00 SN4uatr1and SFr. 8.00 Pig_ 24.0(h _-$IngEpme M$ 7.00 DR 9.0e- (IS A $ 4 A90 - ,// www.americanradiohistory.com Directional power metpx TM10 ., leads by a head For colour brochure contact: FARNELL INSTRUMENTS LIMITED Single detector head covers wide WETHERBY LS22 4DH frequency and power band TELEPHONE (0937) 61961 25MHz to 1GHz 20nW to 100W and TELEX 557294 FARIST G VSWR from 110 3 Head can be used 1.5m from meter (e.g. inside closed car boot) Fully portable -works from internal battery or vehicle battery Farrell Mains adaptor/charger and rechargeable U battery available Manufactured, tested and inspected to CIRCLE 1 FOR FURTHER INFORMATION Min. Def. Std. 0524. www.americanradiohistory.com RADIOCODE CLOCKS LTD SPECIALISTS IN ATOMIC TIME, FREQUENCY AND SYNCHRONISATION EQUIPMENT NEW PRODUCTS MINIATURE RUBIDIUM OSCILLATOR MODULE Lower power, fast warm up, optional output frequencies, programmable frequency offsets. RUBIDIUM FREQUENCY STANDARD High performance, compact and rugged instrument. 2U rack or V, ATR case options. INTELLIGENT OFF -AIR FREQUENCY STANDARDS Microcomputer controlled instruments, directly traceable to N.P.L., precision ovened local oscillator, comprehensive monitoring and status information, real time synchronisation. LOW COST MSF FREQUENCY STANDARD Instant operation, directly traceable to N.P.L., self-contained portable unit no scheduled frequency changes, 24 hr transmission, real time synchronisation Off -air frequency Time code generators/reader Radiocode standards Record/replay systems Intelligent time systems Intelligent display systems Clocks Ltd* Caesium/Rubidium based Precision ovened oscillators Unit 19, Parkengue, clocks & oscillators Time/frequency distribution Kernick Road Industrial Estate, Penryn, Master/slave systems systems Falmouth, Cornwall. Tel: Falmouth (0326)76007 ('A Circuit Services Associate Co.) CIRCLF26 FOR FURTHER III{T. FIELD ELECTRIC LTD 3 SHENLEY ROAD, BOREHAMWOOD, HERTS. Telephone: 01-953 6009 OPEN SIX DAYS A WEEK. 9.00am - 5.00pm THURSDAY 9.00am - 1.00pm CALLERS WELCOME NEWRAD INSTRUMENT CASES LTD ALL POWER SUPPLIES 200-250 V.A.C. INPUTS SPECIAL OFFER DOT MATRIX PRINTERS 230 SWITCH MODE POWER SUPPLIES VAC £32.00 inc c/packing 35 VOLT 10 AMP D.C. £12.50 ADVANCE 5 VOLD 20 AMP 0 . £19.50 HITACHI 9" B/WHITE MONITORS 230 VAC 5 VOLT 40 AMP D.C.. £30.00 TESTED .. [/5.00 19, Wick Estate, Gore Road 5 VOLT 60 AMP Unit Industrial D.C.£40.00 - CALLERS ONLY CARRIAGE & PACKING ON ABOVE £2.00 New Milton, Hants BH25 6SJ 12" B/WHITE MONITORS 230 VAC TESTED .... £25.00 FARNELL 6 VDC 5 AMP SWITCH MODE. 145 1 87 x 32 Tel: New Milton 0425 621195 £20.00 c/pack £2.00 CLARE CL 3001/OPTO-COUPLER 30p EACH 10 for FARNELL 5 VOLT 20 AMP D.C. £20.00 £2.50 SPEC SHEET/GRAPH AVAILABLE CARRIAGE & PACKING 6 VOLT 40 AMP D.C. 000.00 30P CARRIAGE 8 PACKING ON ABOVE £2.00 ORIENTAL MINUATE CENTRIFUGAL BLOWER 115 A.C. FARNELL FAN COOLED MULTI -RAIL SWITCH MODE OUTLET 11/2011/2 01150. POWERSSUPPLY CARRIAGE AND PACKING +5V at U5 AMP -5V at 5 AMP +12V at 5 AMP £36.00 STC STEREO HEADPHONES 2005 New ideal for -12V at 5 AMP CARRIAGE a PACKING £3.50. communications. £5.00 pair cornaga & packing £1,00 COUTANT 0-7V 7 AMP D C. £2250 SPECIAL OFFER B/W MONITOR TUBES 12in New CARRIAGE & PACKING £2.00 Untested.. £5.00 Callers only TEST PROBES C50U AIRC NEW FARNELL 24 VDC 5 AMP SWITCH MODE POWER AMPENEOL4M/M..SOg INSULATED B.N.C. SKI SURF SUPPLIES ..£35.00 c/pack £2.00 MOUNTACE50p EACH NEW FARNELL 12 VDC 10 AMP SWITCH MODE POWER BELLING LEE t.5 AMP INTERFERENCE SUPPLIES. £35.00 c/pack £2.00 CAPPODESOR.. £ 2.00 EACH CATDRICO NEON CRYSTAL 20 MHZ. F£2.00 EACH DISK DRIVE SERIES 30 COMPLETE WITH 230V SUB RED ONLYO 1 FOR £1.00 P.B.U. & MANUAL. SOLD AS SEEN. 230V SUB: MIN: TOGGLE 4C/o. 75p EACH 10 FOR 6.00 £75.00 c/pack £6.00 RED L.E.D. 2.S 10 FOR £1.25 2EK 1 KEY U £1.25 AURALITE LIGHT NST HEADSET & MIC- IDEAL TEKTRONIK HIGH CURRENT PROBES NEW HOSED FOR COMMUNICATIONS. E% -EQUIP TESTED 'nc carnage .. £48.00 020.00 c/pack 02.00 65p CARRIAGE & PACKING ON ALL ITEMS ALL TRANSFORMERS 250 PRIMARIES LAMBDA 9-0-9V 65 AMP T/X £25.00 LINSLEY-HOOD C.LYONS 250V 10 AMP ISOLATING. ... £4600 WODEN 11V 60 AMP... .... £35.00 WODEN 7.6V 120 AMP £40.00 WODEN 27V 30 AMP £25.00 LATEST DESIGN WODEN 80-0-60V 60 AMP ISOLATING.. £115.00 GOODYEAR 115V 50 AMP ISOLATING.. £115.00 RING FOR CARRIAGE & PACKING Pre -amp Kit (complete) £98 + VAT INST: COOLING FANS 230V 4'/,in x 4'/,m x I'/,in £5.00 £4.75 100W Power -amp Kit (complete) £135 + VAT 115V 4'/,in x 4 /,in x 1 ,in TESTED GUARANTEED AS NEW PLEASE RING FOR QUANTITY DISCOUNT 115V 4'/,in x 4'/,in x 17,in NEW BOXED .. ................ £5.50 P&P £2 per order 115V bin PAPST NEW BOXED £6.00 230V bin ETRI/PAPST AS NEW £7.00 GLOBE INST. 12/12V D.C. BLOWER MOTOR NEW £6.50 Send S.A.E. for details and prices of part kits. Con- ROTRON dm 115V SKIPPER FAN NEW BOXED £5 50 CARRIAGE & PACKING £1.45 version hardware for fitting both units into a Hi-Fi COMING SOON MORE 801 SHUGART D/DRIVES COMPLETE WITH P.S.U. 8 CONTROLLERS tower system and also 19" Rack mounting options. WE ALSO STOCK AT DISCOUNT PRICES KEYBOARDS MONITORS. PRINTERS, DISK DRIVES. OTHER TYPES OF P.S.U.. TEST EQUIP.. FANS, MOTORS F.M.P., GEARBOXES. ANY ENQUIRIES WELCOME. ALL PRICES INCLUDE V.A.T. UNLESS STATED. CIRCLE 10 FOR FURTHER DIcr. ll.s. CIRCLE 13 FOR FURTHER DETAILS. ELECTRONICS & WIRELESS WORT.)) \1.AR('H 1 www.americanradiohistory.com Wireléss°wórld over 70 years in independent electronics publishing March 1985 Volume 91 number 1589 FEATURES 17 43 66 British invention, The new logic symbols Alarmphone innovation and by Ian Kampel by Per Andersen electronics The new standard This final part details the explained circuitry for the d.t.m.f. by R.E. Young emergency autodialler, Background to new series requiring no line 49 connection 25 GPIB Floppy discs An introduction to the bus 70 by David March accompanied by our Principles of optical equipment survey Continuing the survey of storage disc storage in microcomputers by J.R. Watkinson 31 This second article in our Sampled -data servos Aesthetic sub definitive compact disc -woofer series details the physics The second part of Dr system of the readout process Taub's new analysis - by M. Bronzite outlining the sampling Analysis of path -length and aliasing processes - diffierence leads to an is held over to the next unconventional crossover issue design REGULARS 6 72 26 Comment and News Letters Events Electro-reductionist Current dumping, challenge, World Causality, IT education telephones, CB Snafu, Neutrons probe structures 78 46 New products Literature received 37 Computer music, Low-cost modem, Image frame Communications store New-look spectrum management?, External voices, Midgley's inventions, Cable & DBS 61 Circuit ideas Vmos squelch for pulse receivers, Bit -rate generator, Z80 instruction counter, Strobe probe www.americanradiohistory.com Front cover, designed Editor by Philip Brooker and PHILIP DARRINGTON by g.E 01-6613128 B.Sc. (Eng.), photographed by ' É.E - invention 5 F'l'MR Ae.S. Kenneth Crook, Deputy Editor British illustrates R.E. GEOFFREY SHORTER, B.Sc. innovation and Young's piece on 01-6618639 ab that Bn uP British invention, ed to show electronics ever of Technical Editor This quologstrenguias level; g which starts on as capable the global with years fields at MARTIN ECCLES over the tis W page 17. contribuuons.mbesedoing so. 01-6618638 an ,M fi.j pr.MP rtanid s yes.mo.f. rta sunce lwn^-.np°".¡ WdOl woo Projects Editor m+a, pM NEXT MONTH RICHARD LAMBLEY 01-6613039 Quartz crystals are by no means as simple as they News Editor might appear. Gordon Hulyer of Cathodeon DAVID SCOBIE explains their 01-6618632 characteristics and usage. Drawing Office Manager Current followers were ROGER GOODMAN discussed by F.J. Lidgey 01-6618690 in February 1984. He now joins forces with Technical Illustrator Christofer Toumazou to BETTY PALMER describe an accurate current follower design, Advertisement Manager which is used in a universal voltage BOB NIBBS, A.C.I.I. amplifier. 01-6613130 In "How long is a piece of MICHAEL DOWNING wire?", John Wiseman 01-6618640 looks at electrically short transmitting aerials - ASHLEY WALLIS those less than a quarter 01-6618641 wavelength - which he describes as the no -mans' Northern Sales land of design. aerial HARRY AIKEN 061-872 8861 Current issue pnce 85p, back issues (if available) £1.06, at Retail and Trade Mid: and Sales Counter, Units 1 & 2, Bankside Industrial BASEL McGOWAN Centre, Hopton Street, London SE I. Available on microfilm; please contact 021-356 4838 editor. By post, current issue £ 1.30, back issues (if available) £1.40, order and payments to Classified Manager EEP Sundry Sales Dept. , Quadrant House, BRIAN DURRANT The Quadrant, Sutton, Surrey SM2 5AS. 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