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BSTJ 10: 4. October 1931: Application of Printing Telegraph to Long-Wave Radio Circuits. (Bailey, Austin; McCann, T.A.) PDF

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Preview BSTJ 10: 4. October 1931: Application of Printing Telegraph to Long-Wave Radio Circuits. (Bailey, Austin; McCann, T.A.)

Application of Printing Telegraph to Long-Wave Radio Cizcuits * By AUSTIN BAILEY and 7. A, McCANE suet die rumen at cr ee ee a cre et ee DRINTING telegraph equipment! lecouse of ite speed, accuracy ane cavenience in earsaiting ineligence, hae bawome rege vised as very useful methed of teegraphy on wiee circuits. Tr some ‘important, therefore, to determine something of the pore uty of present ype of celetypewiters on rad cites, Te common practice to transmis she signal fer operating tele typewriter equipment over wire crete km any one of several electrical Teas. Asinealiertlegraps acti He ign-e freguenty ang inte a se iepntan. More recently alternating currents of voice: Irecuancy sel of higher ecuency have been employed.) Ta employ- ing rai frequencies for operating eletypevriter equipment where the onerating ienpules are o longer puided by a wire crea, new prob- eu ad usy coulis asiae, which are venta pe of ea tee raph transaieson. Tor this eeasna, ies desirable to veview Drie the conditions under which sadio telegraph spatcam are operated. Ta manualesonding sural-roneving practice for radio eegraphy i tas ten coxermary 10 utile, at the receiving end, only 3 marking tome or round whieh ie received during intervals corvesponding tothe time that the seing ley i depresed Tn tranemizting signale from anvare (rants, signal ofa dilleren fequency is eent out ducing ‘he spacing verods fo order to simplify the keying process, but this spscing signal in not tlie at the rosiving end. For aural secepion he nevew'y aul slient resirement ie that the marking tone Be slistnguishable ieough tie oe. Using eae wecriviog it posse br ‘etinguish the signal uncer a wide variation of conditions because of the alility of the ear to accomadate itself to variations in cgnal level ann signal co-noise ratio in J 4 on BELL SUSIRA TROHNICAL JOURVAK. From the transaissioa etandyein, tape or automatic sending, it sending for # tape peterated in accordance with a telegraphis ox, Rineelya matter of increntig sped and acenesty of the characters fanamitied.” Automatic tape reordiag of radio signal suc ax by the sypton resoner ne similar device, ranoves the alvantage obeained ion te tone craccer of she signal #0 eful in ear reemon, and tubsttusee for ths tonal character te Te acute ability ofthe eye ta tletinguish between signals and noive on the tape recore* Tm sacriie- Sag chs ability to receive with gree accuracy’ ta the preseune a emi Siderabie noise there, however, a gun in the speed ef receiving lin Signals. The tant sd which iim pecmanent form, makes it pos be for several operator simaltseousy to transeribe feet, parcs of the reecvw! message epeeds mel slower then the ¢ransmicting speed Tinting telegraphy goer one step further in removing the human levee com the process nf rersiving and substituting aecbaniem Ivhich sane: be imple to a delaite act hy ear exrvent element re- Caved. The printing schaala inevitaby recirds what it receives Srilhout using any iuigweat factor inthe proce other than tke me: ‘husieal application uf sus fs tera 62 have been pat into ely (he desigeer, Uislew the wransmitel signal is received with such fn Tewsity and charar ter aa tobe te contrlling signal at the receiving en run will usually senlt, These of pristng talegraph equipment fadio creuitey therefore, makes “he sgesl-tonoise casio neeeeary fr the receiving of aatistactory coy greater than would be required for ines aural reception er tape sigaal recording. Tt ie of enaserabe interest to compare che approximate sinimu valucsuf sgna-tornoice ratio reine for satisfactory *(eansastion ot Intelligence by single se band long-wave radi using the customary Aiulte sideband carer telegraph, This hasbeen done in thetable on the flowing page ‘When automatic mwas for recording the signals are applied at the veiving end of a ruli ecle tis desirable that considerable uni Teveity exe in the mutput level of the receiving equipmerc. Tiki ven more important when printing ewipment cused. Such a comic aE ASL Ma Seely pv mega aw nya Space tical apart ot ting a upstate eat tna cos Oconee APPLICATION OF PRIVTING TRLAGEAPH om TAMLE £ waves] P| jm wt en 0 uo 2 wring se Sieg ntl aan mecurements = a of sea 230 (BSc Tolwaboat Sab abve tli: whee sec nat fence ie ig rather to be expoctad iansmch ae ultimately in the syatem ‘here must be a slay mechani operated by the sigsals, Thi relay rust with a certain degree of accuracy reprosice the length of the sgpal impulse. isilesirable to have the relay cemtin unbiased overs considerable ange of variation in signal level. Ila signal impulses transmitted only for wacking, the spacing signal Incomes an interval ‘tno current and the restoring force on the relay’ must he snp lo ‘ely Dy either electrical or mechanical means, "Then ith igs of ‘the usual roundel weve shepe ifthe relay operating fooce varies while the sestoring force remains constant, che sgnale wre either “hea” ne Tight" that is, ie marking intervale ave either lengthened or shar. feed add ehe sytem eames biged ‘The most obvioun way of avsiing thes diiculis is some arrange sent in hich the eeotring force on the relay varied dn a master similar to the operating force resltng fom the received signa One ‘nethoa of accomplishing this veal which has been fun site efi tive is the two-tone method of teansmission. As fara te sli cer isconcemal tnesign's consist of 3 ma:king ancl »pacig signal trate mitted on stghily diferent frequencies. Since these two signals traverse che same trinemision nedium, they are at least when there isn selective fang, subjected «sila variation in the envalent ‘of the tranusion puch. Tkeielore, <4 polar eeceving relay luprated by using ene of these froquescies to produce the operating fre wd the ether fequeney to produce the restoring farce so bi fesults. The increase ii magoiude of variations ot he transmission o iret which can be ruleratel hy employing this twortave method of “raven instead af dhe siagle-tone method ith a Axed bins Ie shown by Fig. it I | “yesiren cunsent (ozciee£ naeve neronence) Fig, ‘lai ban rl oorect an peinter operat mg fr the “SSD CONT Gh pnd Se elt fe “Theee curves show the selasion between eperating cue and the limits of pee anargn within whieh norrect operation i verre for tbh the wing Interrupted tone metal of signaling and for the two- furve method. The upper ond lower limize of te printer aarzin are Some to meet atthe lnwer sels of received exreent lieating that the pete tals completely at thew levels. As might be expected, in Crewing the reesived enrrent level afer dy dos wot affece the orienta "ios range ae eriounly asa oresponding decree. In each condition, Towewes the mangin lew sflested when sgaaling by che two-tone tnethod.” Were it nat forthe presnce of soite an the radio frei, it ‘ould be pase toestaiish the normed operating cucrert atx hier alae, ‘The reewn why chis ie not feasible = that the elrtors in the Voice frequenry telegeeph resiving equipment are operatel near the Upper bert nf their characterises. Unter this condition increasing the gain cannes selativey eral itereaae in current fom the vectier thats receiving och nese nl sigal inputs while the curent from the recifer that is receiving noise orly is increased. ‘Ties because of the desirability of eperatiny troup Nigh ncise levela on foag-nave ralio crit, it a noe advantages to utilize all of the available protection spsinst signal level changes. Rather, 2 Cleaponiae ia sought which wil afford stiafaciocy protection against reasonable signi level vacations without making the rociving eas font unduly vulnersble to noise. This practical operating pone ha been seleoted at the zero iaicate on this Fiore, The teranee in reveive erent Tree variations uml obtained isabout + 3d inthe ‘ee of single tone simaling as compared to about Tb fr two-tone igual, Or the trnnmat artic longevave radio citeaite warations frester than theer tolerated Sy che two-tone tranemlzses mull! Seldom cccur with sulfiient rapidity tv excape mana correction, ‘With the two-tone system the emout afte tering the rect ing mechanism eames in chrough double the feed wid used in the singe-tone system" and the intelligeace traneitted is complezely contained in both thernarking and che spacing igual Tein therefore, logical to expe: hat there wil not be much dierence between the (Grown and ssgiecone syetems from the asi interfere stand- point. TP there were no reveive signal the ire through the marking fd spasiag Ellen pray woul laner nt to rome extent but dur ing operation either the mark ox space wigal ie always yrewnt. ‘The noise my effectively annul eter signal by being apprexinacely of Sal inensity and epporte phase, bu the ace through the othe Fieri ersved with the Fill Intensity and, therelove, nay opesate the relay Fabel, Empleving princing telagraph equipment on radio reuits fs aot ew." Thare iss, however, been comparatively tele commercial tse of such systems and chere have nen very fewr quantitative date published. Suck peectial informatio ad wpacnitative data ag have been abvained hy the lll System rogavding tie sppicaion uf pring Aelepeaph to radi eivuies rebate to longeatance overseas point-te point communication al a hrtaiatiner point to-poine eveiand cr uit. Hott of thes crculte were operated on long waves (about 50 Wilocycts, For the past thice years printing ceeyraph has been employed on the long-wave rac telephone ceeuit ™batween New Vo and Tandon tw exchange information pertsining to The apecalina of the telephone service The printer's admirably suital 1 thin Kind of avian vince the information exchange frequenty consste of foreign ames of places ard people a. fanilar 1 the watched apecstors. By the tw of “he printer, these can be spelled out with speed and accuracy swithnat the necesity of attested ram uation "The printing telegraph azcangesnen sve at New Vork for use sof the (lephone crate department on the transatlantic circuits are slow in Tig. 2. Tae instruments sor ted on te table in the foregeound, This table ie lated ane behind the switchboard operae tors Asa large vonjority of che business tramsacied is of a question and anaes nature, ‘here are speciat arrangements in the printer lo ee ‘bene SYSTEM TECHNICAL, sowRNAT, Snvlicate whether the mesage printed original with tke New York or with the London serator. Messages tranwnilied feoat the local machine are typed ie while thoge received fron the distant teem inal are typed fn black, “This was arcompliched by modifying the techarisrs of the machine: automatically shife a hall read Dall black yvina «boa Phe voicefrajmmitytelegcaph terminal equipment? and ity ciated appurates re swan Tig. $._ The equipment enmpies the ‘oice-frenuency terminal ext fr repeating beteeen the lec ee printer Joop cirewit andthe ac fine circu. The printer silching ciruis, testing urangencats, and moriuoring equipment are, for convesienve, Jrekuded ia the same sexily of apparaton. The installation includes fll the suipment necesrary fr one channel of Lwo-tone carcertele- {graph system and suficiene equipmen: for adding nates by povitng Sulable fers ul a smi sunt of aediiensl apparatus, The connection of the printers to the telephone vircait t shown schematically in Tig, 4. ‘The wananiting Ielegraoh circuits are ot ‘cunnected permanently 10 the io chancel. When its desired to co taliish the relezrapa circuit, the coaneetion ie mace through tne er Urs curd reat So che tranetlantie ewo-wire telephone eicult a = ‘nan sia Wo chat wed (amet ilephonesabseribers AUG EC tos bila, SYSTEM TRORNICAL JOURNAL ‘nitoring arramgenmts ave provided for ee telephone aneentor, the Technical aperster, and che prtee operator, The distant ésming! Cperator may incrrupe the printer circle with voice if such intervup fon seer expen: Tn addition tothe yrinuer used by the printer Phonon, a prlatcr at the techaieal opera's pesiton, not shown in ig. 4 i oontiaacusly erected to monitor ua the system. shen he zoted that ia the arirgement shown ia Diy. 4 two diferent voice frequencies ar uted for ramvission and two others for reception, thus giving che mln tages ofthe twu-toae method of rans Inision, The voisefrequency tenes go out wer wie circuits to the framonitiag aation at Rocky Point where, by means of ue singe side Tran suppressed carer matin of cadiowranuaasion ™4ehown in Ti A they sce changed to radio feequeneieol abou 60 kilocyces and an ified. The cyrivalent radianed power for cach frequency is abit Sokilowotte. Farsgaals coming frum England noch the sme process isfollowed at the British end, the sadiared irequenciey however, Sierent from thoge trensmieeel inthe opposite dirton "The must serious handkap fx the use of prinsing telegraph on the long-wave channel ie noise, Daring the winter months tle trouble is tperientd, but interruptions are frequene and are acsaionally of ever hnurs' duration durisg the sunme= meaathe. At ce radio re Ceiving atatons the directive antenna syste used for tlephony ™ realy reduce the nine received ‘Nnother inportant faclor in reducing reseving interference freauency eelectvity. The sadio recive itself sestrces the receive Tene sary to that eit for single side band telephony, passing Tame! about 4000 cycles wide, This s accomplished by the single sie and earveeresuprlielrecever* shonin Fig. The band cdmittet Ineach of the tie cisnel detectors beyond ie reeiver is narrowed Alo toabout 110 cycles By a wee frequency Bler as ieicte in Fig. {Tels estimated that ifthe printer Were used continual on the feng-wave trvatlantic channel forthe entie year, the pet cent of cr ‘ore Would exceed 0 percent lea than 12 per ent of the time and 5.0 Der cen ls thaa 2 por ent nf ue tie Tr order to obcsia more aoswale quansitative information regu fag the ele of asse on te transnason of telety penritersigals over lin ceuity a cevies uf tex was eared une daring 1930, Por the harp of these fete rao ves was established beeween che tn ivtng station a Roky Point, Ly Lane a temporary recelving sacon a Rochester N,V, ailitance of 280 i ‘This one-way crit utiliged at New Yee the transaante trans- suiting felts foe printing tlegrap described above with the ex = AppLicavton OF painrine Taneunaes 0 ception that automatic tanemision froma perforated tape for operat= ing mie celetypenriters was eubeluted for tke manta keyboard method foe aperating tape printers ordinarily used “At Rorky Point the power of the radio erausmiter was greatly eduvel for these tests. The average nawer ranted in che direction of Fochester was equivalent ¢o 0.7 Blewate radiated feom a nmtives= tienal antenna. ‘The average deviation om ee valve was less haa 1 Ub. Under these conditions the average Held receive in Rochester was {225 db wine one microvele per swder. The average cleviation from this mean value yas ese thax 2 db, A daily bol-honr tess was made in te aerncan or evening at time wo chosen a5 t0avuid the sunset perl of disturbed rio ansssssen ‘Ar eachene:, laboratory type eecciving euiment was emplnved for picking up the radi sgaale and dermslulating chem to vite fe= quencies, The voice frequency sigmle wee Uren wsed to oprrale Standard voice Gsueney carrier termaal cquipment at: Rochester. ‘This was modified for two-tone operation in 2 manner sila to chat shown forthe tnusetlantie receiving, tevrinal ia Ti. “The tclerypewriter signals were sent out from New York at 60 ‘worls per minute from an automatic sae tanamiteer. ‘The eupy re= ‘even ver the eee circu was subsequently compared ith smal Lseously recorded crny which was not vext over the radio crit Keyboard errors wsieh occur eceninually in perferaing the tye for ‘zntomasie Lransmiselon appesvnd im both copies. Disergaediag these rors anil counting al wie Wid aot appear on bot copie, it a fosdble to cls che percent of errs ame Ly 1adio ronson, During the hall-our daily test period, sbout 10000 characters were ents Tels apparent ast ree of errr hc were lee an bout 0. ppt cenc coud not be ceermined serrate! ‘Before making ts half-hour test each day to determine the pe cent of erors recived ut Rochester, meszremente were made i the amount [Cr siznal snd of asic in the otpot ofeach woizefeecueney Mer ‘The ‘Senl-uo-noice raro thes mssurel Was ogsured to Be the val o> Taarg ever the soneeding half hour of lest. The nacure of these ineesurements was such thatthe data were sqmewhar scattered. How Ger, by suitable smonthing procedives che spprownate curve shown Sn ig. Sw ole ‘At lleulton, Maine, routine radi nee“ cvervations are made four times each day on ke antenna and Hoarly of the svave-antenna, Cystenn as nat of the operating prosalire in maintaining tamsalae Te telephone services" [e epemed detralle to nd cue wherher Tie data which extend over several years could be util 1 extrapolate

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