US1843227A - Radio telephone and telegraph system - Google Patents

Description

Patented Feb. 2, 1932 i snm-msc una.

sgrarrssjf; sassari' ontzien;

JSEVPHAiHER-MAN, F, WESTFIELD, ANEW' JERSEY, .ASSIGNOR- T0 AMERICANY-VTELEPHNE..

D TELEGRAPHCOMPANY A COR-1E!ORAIIONOEVNEXELYORIKA RADIOTELEPHONE AND TELEGRAIPH ISYSLIJVI Application'led 'December' 13, 1928. SeriatNo. 325,831.

This 'invention"relates to the ltransmission of=signals,-and more'particularly to arrangements forntilizirigfthe,radio apparatusof radio telephone lsystem 'for the transmission s 5pt :telegraph signalsk 1'0" p ara/tus, which ai is. normally :employed for telephone transmission,`r` forfV the Ltransmission Y of V'telegraph imessages-A when; the`Y apparatus isf*not-employedA for telephone purposes.- It is :particularly desirable :to Kusefthe radio tele; Y

1`5 phoneapparatus1orfthe transmisisonof telegraphic messages between operators in f c011=` Y necti'onfwitlrthef establishment of .telephone connections. .l YY

.Hereto'fore suehxte'legraph :operation-:has

'wbeen carried gout yupon a Vhalf-duplex basis; that is, while#messages-'could be transmitted overathe radio links .in either kdirection they separatecone-Wag liiies'to 'a common switche ing point at whiehconnections eouldfbe estab'- lished-to any desiredl telephone line.- Each;

one-wav eline. was providedl Iwith voiceeconcurrents wereV transmittedfover; the line leadingftoth'e radi'oltransmittenfthe'one-way lineV lea-dingisfrom thefradioreceiver was disabled',

and `ifice'versaf. This was necessary in order to. vobtainrpropertelephone operat1on.;.. Teletransmitter this-:point automatically op- '45 "the onemfayline connected to; the radio transnntt'erope-rative and yto` disable the line =lead ing fromsth'eaf radio rreceiver. Thev` audible c tone was'fathen modulated iupon the carrier wave of ithe radio?y transmitter inv` thelsame Y" D0 niannerfasr telephonercurrents; In order f to receive telegraph `messages the telegraphfreceiver was associated with theoneaway line leading fromthe radio receiver at'a point'bct\veen==.thel radio receiver and the'pointzfat which the disabling meanswasfappliedt0"5;,;v

the one-way' line, so 'that the `fact .tliat'zthe` line as a wholewasdisablechso far astrans.- mission from the radio receiver to -thetele'-' `phone switchingpointwas concernedtdid not prevent reception of-'te'le'graph messages over 1 theY noirdisabled portionfof ,the .one-wayfline.

An 'audible tone of a different frequency was.' usedl to` modulate thefcarrier'and wasthen transmittedA fromv ythe distant' terminal ofthe Y radio link.; Thistone wasthen detectedandifes reproduced by the radio receiver ina manner similar to the-reproduction of'ordinarytele'- Y phone. currents'7 and I'upon4 .being selectively I transmitted from the one-way receivingfline to the telegraph receiver wasAcausedYto-oper-l 70.4 ate-thetelegraph receiver in a well-known manner. were 2 actually transmitted in *only 'sone direcf u tionfiat'atime; yThis-was::accomplishedvasr `25'folows :1 'The radio transmitter land radio -receiver -atronelend- :of tlrevradio link 4were lo cated ysome dist-ance fapartand connected by vWhile the foregoing `arrangement permitted-'the :transmission of tele'graphy mes sages one waj,7 at a vtimeyit is highlydesirable to ybe able to-transmit the telegraph messages on a tull-duplexbasis that telegraphftransmission' mayH takeA place in both' directions. simultaneouslv.` ltmight be supposed Athat this would be entirely possible whereaudibleI 80 'tones of different frequencies are' employed@ trolled: apparatus whereby Y whenf telephone-- for transmitting/the telegraph messages to y theradio transmitter and for receiving the telegraph?messages-from the radio receiver, y but experiencek shows that such is not the ease. Dueto' the fact that the radio receiver 'is nearertothe .localradio transmitter than it graphy f messages l were: transmitted' byL 11n-A y pressing lan yaudible tone,Yinterruptedf=in .ae-- 40 "cordance with 'ther message, uponIY the telefplione terminal',y at'v f' the telephone switching.. points. Thel connection of the telegraph is to the f distant radio transmitter; it-fr'e'f quently receives more energy fromthe local Y transmitter than' from the distanti tra'ns- 90` mitter, even wheirslightly ditterent radio Wave lengths are @employed for transmission inthetwo directions and the receiving system erated the voicefcontrolled devices to yrender r' isYmade highlyselectivefto the wavelengthY ploying directional: antenna syst'en'is. Under f these conditions the telegraph message being sent over the midway=line leadingto theradiol transmitter is received on theoneway line leading friolnthe radio receiver si-nmltaneous-10U ly with the telegraph message from the distant station. While the telegraph receiving apparatus associatediwith the receiving line is able to discriminate by frequency selection between theA two tones corresponding to the vThis ldistortion is so grei'i-t as to cause false signals, particularly when printing telegi'aph messages areY transmitted.

Inorder to overcome this diiiiculty it has been proposed to prevent the tone corresponding to thev telegraph signals from the value. q from theradio receiver some ,of the energy of local transmitter from being transmitted over thel one-way. receiving line by associating therewith, at or near the radio receiver, a :filtering arrangement for. suppressing the tone corresponding to the unwanted telegraph signals. VAs suchk suppressing arrangement'would suppress the corresponding frequency Yin ordinary telephone transmission and thereby cause distortion of the-telephone message, it has been proposed to automatical- 1 ly cut in the suppression device when interfering telegraph signals are being received from the local transmitter and to again cut the suppression device out 'when such telegraph signalsceaseor fall .below a harmful This is` accomplished by selecting thetone corresponding to thegsignals from the local transmitter, rectifying the energy and-causing it to operate a relay arrangement for cutting the filter in and out. As this arrangement should not be responsive to telephone currentsy or static signals ofthe same frequency as thev tone employed for telegraph transmission, tlie relay arrangement for switching the filter in and out is designed Vto, operate only when the tone frequency is received over an interval of time longer than that during which a telephone signal or a static signal would persist, and the arrangement has a sufficient hangover so that when v'it isonce operated to cut in the filter it will be maintained operated during interruptions of the tone such as would occur in connection with the transmission ofthe signals of a telegraph message.

lV VNow in any Ytelegraph system employing two current values for transmission, the code may be considered as being made up ofinarlrs and spaces. In ordinaryi land wire Morse or printer operation, the circuit in itsidle condition transmits acontinuous marking signal. In radio telegraphy the circuit 'when in idle condition transmits-a continuous spacing sig-V nal. If any ordinary Morse or printer trans-` mitter is used in connection with the arrangement above describedY sothat tone istiaiis-r mitted for each spacing signal of the telegraph transmitter and no tone is transmitted during marking intervals, it will be necessary to precede each telegraph message by a tone l sustained long enough to cause the operation of the switching arrangement controlling tie filter. In order to overcome this difficulty, it is proposed, in accordance with the present invention, to reverse'the arrangment V4now used for half-duplex operation and transmit the tone during marking intervals,

the spacing signals being represented by no# tone intervals.- Accordingly, when the telegraph transmitter (suchas a printer) is connected to the circuit and normessage is at the moment being transmitted, the printer sending circuit willbe closed and a marking tone will be applied automatically and without any thought on the part of the operator. The

rectifier and relay arrangement are accordingly'arranged to respond to thistone and cut in the filter. The relay arrangement is also provided with a hangover suchas to maintain the filter cut in during the longest marking interval that would occur during the transmission of a message. Ihe filter will, therefore, remain in the circuit so long as the telegraph transmitter fis applied to the circuit for transmission from the local radio transmitter7 and will be cut out'after the telegraph transmitter has been `disconnected, thus leaving the circuit in condition for telephone transmission.

Since thetelegraph receiving apparatus Yis permanently associated withV the receiving line, the factvv that a continuous tone is received during marking yand no tone during spacing would result in causing the local receiving printer to operate continuously wheneverr the distant transmitter jis' disconnected, resulting in objectionable noiseand the printing of false characters during teiephone operation. This is because the disconnection of the distant telegraph transmitter causes the tone to cease, and as the absence of any tone corresponds to the spacingcondition so far as the receiving printeris concerned', will receive aV continuous spacing signal when the distant transmitter vis disconnected. In Order to prevent this false operation 'of the receiving printer, it is proposed, in accordancewith the present invention, to associate kwith the tone receiving apparatus which controls the local telegraph receiver a relay train similaitothat employed for cutting the iilter in and out of the one-way receiving line. The local printer or telegraph receiver is normally disconnected from the tonereceiving apparatus and is connectedi to a circuit which main tains it in marking condition. vVhen the distant transmitter is applied to the circuit S0 ythat a sustained marking tone is received, the

receiverso that itwill respond to the received i incapaz;

telegraph signals and lwill be maintainedcon` neeted vto the tone receiver yduring;v .tone iii-zA terrnptions: correspend-ingv to Jdie spacingv eige,

iialsfo'f ainessagej 'VVheii5- however, the disderstood- 'troinv -thefollowing; ,detailed de lla; scii'ption thereof: wvliciif read in connection.

with tlieaccompanying; drawing, the l"tigure y offriv'hiohillustratesa; preferred circuit ar:- rangement embodying the principles --o'f 'the invention ,In4 the Adrawing;` the circuitvar-4 only. of the radio link is'shown it: being` .understood-that. theapparatus at the other ter-l minal .ivil'lbe `similarfto .that illustrated.V

Refei-i =ingtofthie drawingga radio transiiiib.

ilarlyya radio `receiver `is conventionally indicated at- R. The-receiver and transmitter arelocated.somedistanee-apart in order to reducefiiiterfe'renc-e in. theV receiver from the :aan loca-lf transmit-ters which. .switching connections are established to-any desired telephone rcircuit by means .of aficord C, which may'connecbthe terminal jackfflof the ifouiwirev circuit-With a 1jael`` Jvf eta desired telephonelineby.means o'f-f the-plugs -P and Pf. The our-Wire circuit compri-ses one-Way lilies TL and RL: con-- 'neeted together. yzit-fthe y telephone oHice through a hybrid coil l0 and balancing net verkl?,- ina Well-'known manner.' LTheflines TLfand RL are onc-.Waylines, the line vTL beingarranged to transmit from the terii'iinal` jaekfJ-tothe radiotransmitter Tand the line RLbeingarraiiged to transmit 'from ,the radiowreceiver R to thejack J. Either or both of theselines may'include a'numb'er of repeaters. (not shown) for amplifying the tele.-

phone. currents 'transmittedv ther-cover.

Inoi'der .to preventfsinging overy the vovernk allwfour-Wire circuit-` including the radio.

pathszftothe distant I'terminal.,4 and Valso to prevent; singing .over the local circuit from over A.the "line-i TL tothe radio transmitter,

the:z line :TL :is normally disabled.: Y Voice-op erateddevices are provided/whereby `When Itransinission takes placerom thejacl-J over the .line TL'to the. transmitter T, the line TL tant 4transmitter:is disconnectedso thatthey f tone-:ceases to received'.v for l:a time` 'longer rangement: Sand `apparatus at one terminal --r Vtenis:conventionallyA indicated at T; and siin- The-radio `receiver andy radio transmitter are'coniieceejl by moans of aiourwire kcircuit-to a. telephone officel at theftransmitt-er T to the lreceiver :l-,over .the line .RL,. throughl lthehybrid coil vl0, and i disabled-.1.; This is'aecomplishedbyk associat` ing with each one-".vayline a voice-'operated device yforacontrolling .-a short-circuitI :across therotherfline- Invthewcase .of the `line TL# this: apparatus comprises y--aii :amplifier-deL w tenter unit otavell-lmown type .fTVfassociated v with Athe rlineuTL, Asaid uiiitcontrollingcre lays TVR v'and TVRj Vhen voice currents enter the:-amplicrfdeectorYfTV therelays 'f TVRvf-and TVR. are energi-Zedy the latterq-i opening. ,the normal:short-circuit =acfross the# line'fTL and-permittingitraiismissionfto takel place AfromI jack-J .tof'the Itransmitter Tyand the y. latter closing ashort-cireuit Aacross the line RTiaiid the input-terminals of'an ampligui. lier-detectorunit,4 :RV: associated*` Withwthe lineRL.

Theamplilier-.detector un-itffRV is asso'- ciated with-the yline RL and7 responds rto voice cerre-nts,-received=-irom the radio :receiver 1R 35e and-transmitted over the-line-RL to energize'.

a yi'elayRVRina Wellelmownmanner,l soy that the latter short-circuits the-line TL-i'ndependentlyhof thenormal. short-circuit con-` trolled by the relay TVR. The short--cir Fv 961 cuit thusapplied to the-line TL' also'serves' to-short-circuit the ampliier-detector .TV to prevent false. operation.. Delaynetworks TD-N and-RDN are associatedwith the lines TL andRL'-7 respectively, to enable the voice- 95hA controlled switching4 devices to perform their oiiees beforethevoiceeurrents arrive-at the points in thecireuits which are' affected by the switching.. operations. For example, when voice-1. Currents Vare transmitted from-100 the jack J over the lineiTLthe voice currents are sufi'ieicntlyj delayed iin passingthroughv the network ITDN vto enableY the amplifier# detector unit TV to remove the short-circuit from Ithe line TL before the voice currents 10g arrive -at the point at Whichwit is applied. Similarly, When voicecurrents are transmitted from thereceiver'R over the-line vRL'the voice currents are suiicientlydelayed by -the network RDN to eiiablefthe ainplilier-detec- 1m tor RV to short-circuit the line TL before the.- voice .currents have an .opportunity to pass through. the 7hybrid Acoil 10 (due to uiibalance) andv enter the. line VTL.

Duringlperiods when thefcircuit above de- 1p: scribed lis .notrbeingused vfor telephone operation, it isdcsirable to use the radio'facilities:fortheitransmission of telegraph -messages, and moi'eparticularly itis-.desirable to. transmit printer messages betweenvoper- 1550` ators to. give directions necessary to the es-A tablishment.. of-A telephone connections over the radio flink. In Iorder to transmit such telegraph. messages from the telephonefoice shown to a distant telephoneoice associ' 123 ated wvitlithe distantterminalr of the radio2 liiilnthe cord C, Whichis used'for settingl-,up` telephone connections, may 'have-its plug P. insertos `in a jack. .lf which is connected .to

' a telegraph transmitter.A This .transmitteif 1in-f is arranged to 'open and close a short-circuit across-the-terminals of a tone source connectedv to the Vtip and ring conductor of the jack J. For reasons that will more fully appear hereinafter the relay TR has itscon- ,y tact 'so arranged as to open the short-circuit across the tone source G during marking impulsesv and to close the short-circuit during spacing impuls-es. Consequently, an audiblel tone will be applied to the terminals of the ack J and transmitted over the line TL to the radioftransmitter during the marking inf tervals, while spacing signals will be represented by ano-tone condition of the circuit,

` -these conditions being .reversed with respect tothe present .methodjof printer transmission over such circuits. The tone employed is preferably an audible frequency so that Yso it may be transmitted over the circuit TL'in the'same manner as voicecurrents are transmitted; 'A

Since, as has already been described, the line TL is normally disabled by means of the short-circuit applied bythe relay TVRQVit is "necessary to render the connection over the line TL operative in order that the printer signals may be transmitted. 'p This result is accomplished by a ground connection established over the `sleeve conductors of the jack J, plug P, sleeve conductor of the cord C,

sleeve conductors of the plug P", and the telegraph jack J and thence over a conductor 20, through the windings of relays TVR and VTVR to the'plate battery. This causes the energization of relays TVR and TVR independently ofthe plate circuit of the amplilier-detector unit TV'and maintains these re-V lays operated as longasv the telegraphV connection is established. The short-circuit is, therefore, removed from the line TL so that a the tone corresponding to the marking signals may be ltransmitted over the line TL to the r'adiotransmitter T, where itis modu-. lated upon the radio carrier in the same way asordinarytelephone currents, and transmitted to the radio receiver at the distant radio'terminal. The energization of therelay TVR, however', short-circuits the line EL between'the amplifier RA and the delay network YR-Dllso that transmission cannot take place from the radio receiver R over the line RL to the jack J. It is, thereforenec 1 essary that the telegraph receiving appara,

' tusbe associated with the line RL for reception L of telegraph signals from vthe distant station in suchvmanner as not to be affected bythe short-circuit controlledby the relay TVR. fAccordingly, vsuch telegraph receiving` apparatus is bridged across the line RL at Vv---y/ ybetweenv the point at which the shortcircuit is 4applied and the radio receiver R. j

The one-way amplifier RA is then connected between the terminals -fl/ of the telegraph receiving apparatus and the point at which the short-circuit is applied by the relay TVR, so that the short-circuit does not have an effect upon the telegraph receivingapparatus and transmission may take place from the radio receiver R- over the line RL to the terminals x-Jy and thence into the ltelegraph receiving apparatus.

The telegraph signals received from the distant radio transmitter arev applied to such radio transmitter as an interrupted'tone in a manner similar to that already described with respect to the station shown, but in'this instance the tone will' have a different fre-V quencyl from that generated by the tone source G. vThe tone employed at the distant station the radio receiver R due to'interference'from the local transmitter T, such telegraph re` ceiving apparatus includes a filter RF for selecting the desired tone. An amplifier RA may also be provided for amplifying the received current, Aand a detector RD of wellknown type is provided'-for rectifying the, tone to'produce direct current signals corre- TheY direct current impulses actuate the polar respending tothe telegraph impulses.

lay Pltl, as Willlbe described in more detail later, and by means of ythis relay are trans-V mitted to the receiving printer conventionally indicatedatVrRP, as ,willfalsol be made clear later,

' vThe arrangements() far described will operate satisfactorilyfor halfduplex operation Vwhere the circuit is only'used for the transmission of telegraph messages in one direction at anyone time. T11-attempting to operatethe circuit on a full-duplex basis so that transmission of telegraph r'ne'ssagesy tak-es place in both 'directions at the `same time, how: ever, difficulty may be encountered where interference from the local transmitter'T is very heavy, due to the fact thattbe signals from the local transmitter T, when transmitted over the line RL at the same time as the desired signals from Vthe 'distant transmitting station, vwill tendto overload thewrepeaters (not shown) in the line RL, and thereby cause distortion of the signals actually received by the telegraph receiving apparatus." It theref 12 line RL `the tone frequency corresponding to n fore becomes necessary to suppress Vfrom the thetone source G. VThis is accomplished by switching into the line RL on the output side ofthe radioreceiver R a suppression filter RSF, of any lwell-knowntype, so vdesigned as `to1suppresslffro1nl the `1li-ne' RLfthetone fre- /i'quencycorrespondingrto the .source G; `While @freely passing .other :frequencies: :Within the il'voicel range. lAsfthe:inclusion` of'sucha iilter `@5in irthef .-telephone circuit 'i during telephone 'ftransmissioni*y Wouldhtend: 'xto :suppressfrom the telephone band `frequencies infthefy nei ghloorhood` of the 'tone from' the source G, .thereebyca'using' theitelephonic distortion, the arfm rangementv should be 'suchl that .the suppres- `sionfilter RSFf fis 'onlycut into v'the :circuit rwlrenthe systemiisvheing used l'for telegraph 1reception,apadiRP, having an impedance equal. zto the/impedance ofi. thelter ina the lfrequency vl.ran-get outside the hand; which: the `vlfatter suppresses, being lsubstituted vtherefor duringtelephone' reception.

This switching operation is: accomplished rbyfselecti-ng some of theenergy oftheunde- `isire df tone".v from fthe localiy :transmitter T on -the :eutputfside of the `radio' receiver` R, and by irectifyingt the =.energy, operating, relay traint-.to switchithefilterin 'and out-.of the @circuit Accordingly-zt circuitqis'i bridged @25. across the iterminals^.fm-+y f which comprises an fampliiierRA for `amplifying'the unwanted tone frequency,'aaselectingtilterRF' forl sefleeting such fan: unwanted tonel frequency, and af dete'ctorR'Dl .for .rectifyingthe-.selected Cur- '""'30 1rent=tov ,operatev a polar relay? "Pll. The lpolar lrfelay; PRlcontrolsfthe'circuit' of a relay PE2, whichiinturiropens a circuitiof a'polar relay 11T he llatterfrelay controls 'the kswitching relays" '1D-.Rr and 13.1% for switchingzthedilter :lEachotitherpolar relays'PRl,A PE2 and 'BRS' fifrrcludes:1 an operating -ivi'dinzgf and a @hiasingfwinding"the biasingfwindings b1, b2 rand b heilig'connected in series and through -hattery The current flowing fthroug'h these biasing vvwindings* norrnally'fholds :their arma- 'turesiagainst their :hack-contacts, hutv When a currentA flows through V.the corresponding open; relatingwindings o-fmsuflicientnstrength,l a pull is pro duced upon 'the'airmature inthe opposite direction; andthe armatures of the relays .are .shifted tovftheir front contacts Vhen a -tonefis received thed-etector' RD produces a e150 rectified currentt-hrough the operatingwindingoi which shiftsv the; armature' of the relay LPRlto its front-or-lefthand contact',"thereby -fcausing Acurrent to flow from' ground lthrou gh the.operatingmvinding- 02. .to. battery. The .-current ythrough' the ,operating winding of `the polar relayi PE2 in turn Shifts its; armaturey #from e its right-hand or .aback contact A`to gits :diront "Contact,y thereby opening the circuit normally existing from; ground through thefoperating- Windng. 03 "ofthe relay FR3, 1 to battery. 'lhe'relay FR3 thereupon vshifts its armaturefroms its front Acontact-to its righthand oie-hackrco'ntact,='ftherehy completing a circuiti fromf groundthro-ugh thevoperating windings-@and ogof'therelays P135 and PR4.

vThe relays PRl -andPR' thereupon A: shift 'their armatures insuch direction asfto disconnect the pad RP and substitute therefor Ithe vmsuppression iilterRSF.r The armature`r ofthe relay PR., at the f same ytime rclosesltlie ioircuit. :of a'signal lampi-8Oy tof indicatelth'atfthefsuppressi'ontfilter -isrin circuit.

T-hexr'elay train, above .'desoribedvshould :he f so designed/asto Vpre'Ventsfalsefoperationidue to relatively short telephone andfstaticfsig-,q ana-ls" inv'olrirn Afrequencics corresponding: to the wselectedV tone frequency. Accordingly, theoperatingandxreleasing times ofthe Vari- -ous relays are :fset as :to take into; account ythe time intervals fiiwolvedA in fthe y transmissi-on yof-printer signals. -Assuming rthatithe r-printcrfis operated at a speedI ofiGOWoids-per rminute (about 23` dots'` per second): the's'h'ortest undistorted Inarkingf'ortonetransmitting impulse due tothe printer operation Willsbeegg about 1022 second. c-Allowingfor.- aelittle'fover twenty-five per c nt. distortion,LM this figure becomes .015 second. `TheA longestfuspacing vor! lio-tone` impulseI which would occur'fwill he -six units long, or about'lsecond. Underiag() vthese conditions the relay ftrainffshouldfhe desig'ned to.. .hefunresponsive` to impulsesn-or -tonee groups: fshorter thanY about :1015 second. For impulses longer, thanE .015- second. the relay PR;l ofr the train is operated andfreniains.4 95 -operated efor at leastrlf second; after the impulse 'ends,thus 'providing a. hangeo-verfperiod sufficient f.topreyent release during theclongest: 11o-tone inter-val Which may-occur, during ,fthe vtransmission of-@signals ilheoperation- .100 ofthe frelay PRE/in response to .an impulse -le'ngcr` than .015' 4second -does f not, however, necessarily switch thesuppression iilterAin 'the circuit-as the train shouldfhcyso designed Lthat 'this switching operationnwill not :take .,105 place in response to aniinitialoperation ofthe relay PR-l hyfreasonf of a .fai-rlysustai-ned t'ele phonic frequency Correspending to the tone frequency. To prevent such-falseoperation t'in vresponseto Itelephone currents, the swit-elr n.ing operati on to cut in theilteris arranged `totakel placeonly if the relay PR2 Aremains :operated` continuouslyfor -some .arbitrary ,period such as, say, l-.5 'fseconds fVheln therefore,: a steady-tone is received,` suchs-as occurswhenever.the flocalprinterfis first connected tothe circuit, or ifinterrupted tone `is received` Asuch as 4occurs Whenevertheflocal printer,- -is connected to fthe circuit Whilef-al- 'readyt sending amessage, this switchingfoperation will he performedin l-.5\seconds. In .order-to.insure-.that asteady tonefwill he received finv the: majority of cases, .the-code is arranged; ashas alreadyV been described, -so that the/tone is transmitted duringthe mark- 125 ing interval 'and not during lthe-spacingv infteryahz asf was4 heretofore'` fthe fcase. Conse quently, 'fthe mere fact l of connecting f Zthe printer tothefeircuit at the local transmitter yresults'`l` in the transmission fof-f a/f'steady'tone 130 relay charging current flows through the operating ,untill the". sending j ofv signals commences, .which rcause'sthe completefoperation of the .felay'train v f Y f In orderthat the relay train inayhavethe ,.timing abovedescribed, the relays PE1.' and l `PEsliaveassociated with their operating vvindings resistances and condensers for obtaining; slovv operationorv slow release. In thecase of the relay. PE2 this relay operates lo .upon the shifting ofthe armature of PE1 to 4itsfffront contact. 3,000 ohms, included in the discharge circuit so .that the as soon as the 6 m. f. condenser is discharged A suitable resistance of,

impulses shorter than .015 will` not cause sufficient discharge to operate the relay PE2. Whenthe armature of the PEgfisl shiftedto its back contact, a

Winding 02 of the, relay'PEZ'to charge the 6 m...f.` condenser, yand resistance of, say,

'48,000 ohms, is connected inthis charging ycircuit so thatthe charging currentwill main-` ',tain. the relay'PEz operated for .13: second 'after the relay. PE1 has been released. The 25 relay PEg vips-'normallyoperated, and lits cirycuitconstants aresuch that'it Will not be release'd-until the relay PE2 has been operated for about 1.15r seconds; This is due to the PE1, is

must takeplace before the WindingV o3 gets a f-'sufiicient v operating current`,- occurs very fquickly in series with the small 500-ohi'n re sistancei Eelays PE4 and PE5 are very fast operating and very fast to release, and their operation is controlled by the relay PEB. It will be understood, of course, that the values Yof the resistances and condensers vas above given and as indicated upon the drawing are given'only Jfor purposes `of illustration, and

these valu'esmay be Widely varied and their Aproportions With respect to. each other may be changed Without defeating the result above described.' Furthermore, the timing of the 'U relay train as 'above'given is merely illustrative and may be variedjthrough' aconsiderable range depending upon the Ynaturev of the telegraph lsignals transmitted, the speed of Y.

' transmission randthe margin Y* of insurance against'false operation deemed necessary in -a Aparticular design.

1 As has been previouslystated, the receiving telegraph instrument, such as the receiving printer yEP,l is operated by the' shifting of 'i' 'the armature ofthe relay PE1in the output circnit'of the detector ED', the armature of the'frelay PE1v .sending `negative or positive impulses. tothe receiving printer EP for Amarking and spacing signals, respectively. i AWith-the codearrangement previously de-y escasa? scribed, in 'which the'tone istransniittedduring marking intervals and nol tone during the aspacing interval, it will be evident that ,Where ever the telegraph sender at .the Idistant 'end is disconnected, from-the jack corresponding? rPhe result is that the armature of the relay PE1 will be shifted to itspositive contact due, to the action of the biasing Winding b1',

and thereceiver will th'enreceive va continu-4: .ous'spacmg signal ,so that itWill continue to operate .unless some means is provided to preventthis action. Accordinglya relay Ltrain comprising relays PE1 .,PE2 and-PES is lprovided,fthelastrelay (PEJ)y ofthe trainr .operating to control a relay PE1 Whose armature serves to switch the receiving printer EP .to J, the marking tone, Whicli is normally Ysent -ivhen no signals are transmitted and whichy normallyy functions ,'to ,hold the armaftureof the relay PE1 against its negative contact to send ay marking signal to the ieceiv-f` Ving` printer EP, will no longer! be received.l

from a normal marking battery'lto a 'contact which. completes the connection; fromy the printer. to the armature ofV therel'ay- PE1. g. rhis relay trainwill preferablyliave the-same timing' and hang-over features as the relay train previously described for controlling the switching of the suppression filter ESF.. The

initial relay PE1 of the train is a simple es.

polar relay Whose Windingis in circuit with the armature of the receiving` polar relay PE1( and therefore the armature ofthe rela.

PE1 moves in unison With the armature of r the receiving polarLrelay. Thearinatureof? ico the polar relay PE1 controls the circuit of,

the relay PE2 inthe same Waythatthe relay PE1-v of the previous train is controlledby the relay PE1. In short, the relayA PE1 is merely provided because the' usual polar rel ay f of the type of the relay PE1 has only one set of contacts. If such relay had two sets of contacts, onerof the sets of contacts would be used to control the relay PE2 and the other relays of the train inV exactly the same Way as the relay PE1 controls its train.

yPhe result is that When'the'printer is not connected'atvthe distant 'sending station, re-

'lays-PE1( and PEgivill be released, the lat 'ter maintaining thc relay PES Voperated so l.

that the operating circuit of theswitching relay PE1. is openv and the armature of said relay PE1 is held against its left-hand or back Contact to connect-the receiving printer VEP to a'positivel markingsource. This prevents the receiving printer from receiviDQ.' 2l Continuous positivespacing current rover the armature of thel relay PE1 As soon as the printer is connected to the circuit at the' distant sendingrstation, a toneavill be re- 'Y vceived Aand rectified. by the' detector ED1..

This tone must continue for a periodof, say, .O15 second in order to enable' the relay PE1',l to actuate the relay PE1', and when the latter relay is actuated, it. will not be released yffor, aperiod otfsay, lsecondpor. long 1e1ioughto-hold overtlie longestno-toneiinter- .valwhiclr may occur. during thesending oi' :signalsl The relay PRQx-lioivever;Willniiot i 5 release in response tothe operation lof relay PfRggiiiilesstlie.latter relayfreinains operated L continuously for soin e.: interval -suehr asfitor `ing the frelay PRL fivliicli is quick to operate fand@- quick to 'release,. l.so that the. vreceiving 2printerRP `is;disconnected from the normal marking sourceand is connectedtoithe'arma- "Wlieiiftliel distant vprinter is disconnectedl so jt-lilnt tlietone ceases; tlie relay P32',- releases Las--sooii-'i-as tlie tone has ceased toifaperiod of; say, second, i'thereby' causing the 4relay @PHJ to operate quickly and throughfrelay "PR/-slritt vthe connectionot'. the receivin KVprinterv RP totlielnormal markingsource.

iti-Will' be observed thatthe relay train vfor l'coiinectingthereceivingpriiiter RP in circuit responds onlyto'thetone frequency originatfingat `"the 'distant gtliaii'sinitter. iThe relay `traiiitor s Witcliingithesuppressioir lilter RSF into* and4 outj of circuit?l on the other hand, responds onlyto the-tone 'frequencytransmitted 5 iii'oinltlieflocal fti'aiisiiiitterT. Consequently fit-he' receiving printer may `be lcut finY and out ot circuit and may receive its signals-Withoiit material distortion regardless of Wlieth er "oi rottlie localprinter TP is connected'to the lflircircuit overthe'cord C. "Vlienever such local itransinitting Vprinter TP is connected in oirc'uitji however,l the suppression'iilter LWill be "cutlin' quiteindepend-ently 'otivlietlier signals are'heing `receiveditroni the distant-transmi tais' @L IESE,

dft-Will loe 'obvious tliatthe general principlesfl-ierein 5d-isclosed1- may be embodied iii inany- 4otherr` organizations .-Widely different 'trom i tliose illustrated L1vithout departing Utroni the spiritot the invention asfdetined "iii-` -tlie'-` following claims.

iiWhat'is -claiined is: 1Q Ink vavradio signaling system including. a -ri' dio transmission? yliiik,'a radio transmitter f. "d a'fradiof iecfeiverY at one terminal of said Vv'radio link, a -iouiivire junctioii,` afiioriii'a'lly disabled one-way -transmittingliiie extending 'troni said' tour-Wire j unetioii 4to -saidradio 'tr-'ansinittei",y a tone-Way receivingline extend- 0 ing ti.oiii`sai l-1radio 'reoeiverto said junction7 imea-ns associated with each oi said lines and 'responsive to rteleplionesignals Vtransmitted tliei'eovei i to disable ftlie 'other line, telegraph transmitting apparatus and lvtelegraph recei v- *1U-5 fing# apparatus, said telegra'plif transmitting l apparatus producing a tone'interruptedinraccordaiice with a codesothatthe tone istransl initted duringniarkingsignals and: v.no tone istraiismitted during.spacingsignalsgWhereliy a sustained marking. tone/preceding:the

transmission of codevsignals is. transmitted when said telegraph transmittingapparatus vis connected to said' four-Wire'juiictiom said telegraph l'receiving apparatus including means tov translate aniziiiterrupted toneiot different frequency':received tromtliedistant terminal yinto. ,direct A"currentsmarking 1 and spacing .signals and means ,responsive toisaid 'direct-current signalsyineans op'eratingnivh'en thev ,telegraphI transmitting 1 apparatusf is.:v asf sociated withsaid'.-foui-\vire j unctionlto 'render saidftransmitting linefop'eifative aiidxto -f disable Isaid receiving line',l means 'connecting .said telegraph receiving appauati-is with r sai d receivin o: v line between .the i `point ats which i it ldisabledland-.saiid radio'ireceiver,I a supplies si on device ior suppressing,theitoiie frequency supplied` by said-telegraph :transmitting apparatus while passing the f tone-.frequency .used tor telegraphitransinission from tliedis .tanti terminal,y and'.means.responsivetoV .the

sustain edtma-rkingftoiic, transmitted byaadio 'trom the local radio transmitterlto tlieflocal Arad i o "receiver upon vconnection. 'of Ithe's telcgraph transmitting .apparatusto connect .said

suppression' device in lsaidreceiwingf line.

2.1 ln' a radio :signaling systeiiiiincludinga radio vtransmission.flink;a radio transmitter vaiidfa .radio receiver at oneterniin'aliof said -radio link, a tourivire, junction; a-no'rmfilly ldisahled oneway transmitting' line ,extend- -iiig 'from said tour-Wire auction 'tosaid radio transmitteuY a one-'Way .receiyingfline .extending 'tromlsaid radio 'receivento said ajuncti'on, means associated ivithreach ofsaid iliiies yand -responsiveftol telephone ysignals. transmitted .t ieieovei-fto; disable :the otheixline;'telegraph transmitting apparatus and.` telegraph receiving apparatus,-.saidf telegraph;l transmitting apparatus producing: a tone :iiitcui'uptediin accordance \v1tli1.a-rcodeso .that tlievtonezfis transmitted duringinarking si gnalsiand no tone is transmitted f during spacing signals,

-whereby: a. sustained iiiarkingtone preceding .tlieftransiiii-ssion 'of code signals.: is transmitted when .said i telegraph; :transmitting` apparatus is connectedto saidHtour-Wiregjiinction` said telegraph receiving apparatus 'zincludin f nieansf Ato translate fan 'interrupted tone: ofv different frequencylreceived fromftlie `distant' termi nal :into di rect :current marking an d spacing signals. and means responsive to said Vdirect current sigiialsz'fmeaussoperating when' .the telegraph transmitting. apparatus associated ivitlisaid rfour-wire -j unctionAv to vrender said transmitting lineopenative and to.` disable said receivin fline= :meanseonnect- 'ing said telegraph receiviiig fapparatusffwith said :receiving line-betweenitliepoint at which it isdisabledrv and said radiorecei-veigv assap- -said means operating iii response to a sustained tone of the frequency supplied by said telegraph transmitting apparatus upon'being connected to the four-Wire. junction.

' 3, In a radio signaling system including a f radio transmission link, a. radio'transmitter "junctionpmeans associated With each of said' sei and a radio receiver at one terminal of' said ia'diolink, artour-Wire junction, al normally disabled one-Way'transinitting line extending Vvfrom saidv four-Wire .junctionk to said radioF transmitter, a one-Way receiving line lextending .from said radio receiver to said lines and responsive vto telephone signals transmitted thereover to disable vthe other line,; telegraph transmitting apparat-us and l telegraph e receivingapparatus, said telegraph transmitting apparatusfproducing a` 1 Vtone interrupted `in accordance with a. coc e so that the toneis transmitted during marking y "signals and notone. is transmitted during fspacingsignals, whereby a` sustained mark- A ma' ing tone precedingthe transmission of code signals is transmitted .when said telegraph transmitting:apparatus is connected vto said four-Wire jiinction,fsaid telegraph receiving ',app-aratus including means to translate anV iinterru'pted tone tot different `frequency recei'ved from the distant terminal into direct current marking and spacing signals and meansresponsive to said direct current siglnals, 'means operating rW-hen the telegraph transmitting .apparatus is associated with said :four-Wire junctionto render said trans- -initting line operative and todisable said receiving line, means connecting said telegraph V- receiving apparatus With said receiving line between the point at Which it is disabled and said'radio receiver, a suppression device for :suppressing the tone frequency supplied by saidtelegraph transmitting apparatus While passingthel tonel frequencyused for telegraph transmission from the distant termi- `device iii-said. receiving line, said means operating inresponseto a sustained tone oi' the requ'ency supplied by said telegraph transmitting apparatus upon being` connected to the four-'Wirer junction, said means also operating to maintain said suppression device connectedduring interruptions of said tone diie to spacing-signals, 1 l f' Y t 4411i .a radio signaling system including a radioftransniission link, a radio transmitter and a radio receiverratone terminal ot said radio link, ,a ,four-Wire' junction, a normally ldisabled one-Way transmittingl liney extending Vfrom said `lour-vvire junctionto said radio transmitter, acne-way receiving line extendnal,'and means to connect said. suppression ving from said radio receiver to said junction,

means associated With veach of saidliiiesand responsive to telephone signals transmitted tliei'eover to` disable the other line, telegraph transmitting apparatus and telegraph re- Vceiving apparatus, said telegraph transmitting apparatus producing a tone interrupted in accordance With a code, said telegraph receiving apparatus including means to translate an interrupted tone of different trequency received from the distant terminal i into direct current marking and spacing signals and means responsive to said direct current signals, means operating when vthe telegraph transmitting` apparatus is associated With said tour-Wire 'junction to render said transmitting line operative and to disable 'said receiving line, a suppression device for suppressing the tonel 'requency'supplied by said telegraph transmittingapparatus While passingthe tone frequency usedqfor telegraph transmission 'rom the distant terminalmeans responsive to the tone transmitted by radio roin theflocal radio transinitter'to `the local radio receiver' to connect said sup- Ypression device in said receiving line',` said.

telegraph .receiving apparatus being associated with said receiving line between the point at which it is disabled and theradio receiver -andsaid direct 'Jcurreiit signal responsive means being ,iiorniallyvdissociated from saidntranslating means and connected to a marking circuit, and means'responsive to ythe tone transmitted by radio'troin the distant radio terminal for Vconnecting said vsignal responsive means to saidtranslating Y 5. In a radio signaling system including a radio transmission link, a radio transmitter and a radio receiver at one terminal of: said radio link, afour-Wire junction, a normally `disabled one-Way transmitting line extending from said tour-Wire junction to said radio transmitter, a one-Way receiving line extending from said radio receiver to said junction, means associated With each of said lines and responsive to ytelephone signals ,transmitted thereovei to disable the other line, telegraph transmitting apparatus and telegraph revvvice for suppressing the tone frequency supplied-,by said telegraph transmitting apparatus While passing the tone frequency used for telegraph transmission from the distant terminal, means to connect said suppression l n being associated with said receiving line between the point at which it is disabled and the radio receiver and said direct current signal responsive means being normally dissociated from said translating means and connected to a marking circuit, and means responsive to the tone transmitted by radio from the distant radio terminal for connecting said signal responsive means to said tra-nslating means.

6. In a radio signaling system including a radio transmission link, a radio transmitter and a radio receiver at one terminal of said radio link, a four-Wire junction, a normally disabled one-Way transmitting line extending from said four-wire junction to said radio transmitter, a one-way receiving line extending from said radio receiver to said junction, means associated with each of said lines and responsive to telephone signals transmitted thereover to disable the other line, telegraph transmitting apparatus and telegraph receiving apparatus, said telegraph transmitting apparatus producing a tone interrupted in accordance with a code, said telegraph receiving apparatus including means to translate an interrupted tone of different frequency received from the distant terminal into direct current marking and spacing signals and means responsive to said direct current signals, means operating when thetelegraph transmitting apparatus is associated with said four-Wire junction to render said transmitting line operative and to disable said receiving line, a suppression devicefor suppressing the tone frequency supplied by said telegraph transmitting apparatus while passing the tone frequency used for telegraph transmission from the distant terminal, means to connect said suppression device in said receiving line, said means operating in response to tone impulses of predetermined character and of the frequency supplied by said telegraph transmitting apparatus, said meansv also operating to maintain said suppression device connected during interruptions of said tone due to spacing signals, said telegraph receiving apparatus being associated with said receiving line between the point at which it is disabled and the radio receiver and said direct current signal responsive means being normally dissocated from said translating means and connected to a marking circuit, and means responsive to the tone transmitted by radio from the( distant radio terminal for connecting said signal responsive means to said translating means.

7. In a signaling system, a circuit over which signaling impulses of various kinds, including printing telegraph signals, are transmitted at different times, means controlled by printing telegraph signals regardless of the character whose code istransmitted for determining when the signaling impulses on the circuit are printing telegraph signals, and switching arrangements controlled by said determining means for connecting a receiving printing telegraph device to the circuit.

8. In a signaling system, a circuit over which signaling impulses of various kinds, including code signal impulses, are transmitted at different times, means responsive to code signal impulses regardless of the character represented by the code for determining when the signaling impulses on the circuit are code signal impulses, and switching arrangements controlled by said determining' means for connecting a code receiver to the circuit.

In testimony whereof, I have signed my name to this specification this 12th day of December, 1928.

JOSEPH HERMAN.

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