US1773092A - Carrier telegraph circuits - Google Patents

Description

Au 19, 1930. R -H CLAPP 1,773,092

CARRIER TELEGRAPH CIRCUITS Filed March 12. 1929 ||||||H||. V I mi Mutral Sounds:

. Stat/1m I gs lNVENTOR 3 BY 'i@@ ATTORN EY Patented Aug. 19, 1930 UNHTED STATES PATENT OFFICE ROBERT E. cLArr, or RAMSEY, NEW JERsExnssIGNOR To AMERICAN TELEPHONE AND TELEGRAPH COMPANY, a CO PORATION or NEW YORK CARRIER TELEGRAPH CIRCUITS Application filed March 12, 1929. Serial No. 346,361.

This invention relates to carrier telegraph systems, and more particularly to carrier telegraph systems in which two-way half-duplex Operation is provided with the requirement of only one carrier frequency. The principal Object of the'invention is to provide for telegraph operation of the type indicated above Without the'requirement of line balance.

In accomplishing his purpose, the applicant employs the method of Operation in accordance with which carrier current is sent .into the line to produce a spacing signal and is cut off for a marking signal, and so arranges the apparatus and circuit that the receiving apparatus at either end'of the tele graph circuit responds freely to current transmitted from the distant end i but is rendered incapable of operation while current is being'sent out from the near end.

The .invention will beclearly understood when. the following detailed description is read with reference to the accompanying drawing, which shows diagrammatically, and

in part schematically, one desirable embodiment of the invention. In the drawlng there is shown 1n such detail as is deemed advisable the apparatus and circuit arrangements of a station X at one end of a carrler'telegraph system. The

connection from station X to a subscribers office is indicated at the left of the drawing, and a two-wlre line 1s shown connecting station X to a distant station Y at the right, it being understood that the apparatus and circuits of station Y are identicalwiththose of station X. While the apparatus of a single carrier channel only is shown in the drawing, it is understood that other similar channels may be provided in a multiplex system.

At station X a vacuum tube oscillator O is the source of carrier frequency oscillations and is connected to the lnput of the vacuum tube amplifier A which transmits the carrier current to the line. The polar relays R and R the resistances 1' and T the sending key K, the neutral and polar sounders (schematically shown), the receiving relay R and the receiving amplifier A and the rectifier through the armature, the tube A is rendered opcrative,:and carrier current is sent over the line to produce a spacing signal at station .Y.

Associated with thevacuum tubes A and D in the receiving channel is a second rectifier tube D connected as shown, A transformer T has its low winding W bridged across the input of the rectifier tube D and its high winding W connected in the plate circuit of rectifier tube D .There is impresed on the grid of tube D 21; negative potential great enough to prevent the flow of current in the plate circuit of the tube when signals are received from the distant station 1 Y. Due to this biasing voltage, of course, and the resultant high impedance offered by the transformer T, the bridging of the transformer windingw across the input of tube D causes practicallynoloss therein, and the signaling from station Yfto station X is not interfered with. v

When, however, the carrier current from oscillator O is sent out, this current being approximately QOdb. higher than the current received over the line from SttltlOIlqY, the negative voltage on the grid of tube D isreduced to the pointat which current flows in the plate circuit of that tube. This flow of current through winding W of transformer Treduces to a low value theimpedance of the-transformer seen from the input circuit of tube 1),, and the effect'of-the bridged winding W becomes practically, that of a short circuit on the input of tubeD Consequently, any current transmitted through amplifier- A will not operate the tube D and the receiving relay R is unafiected;

.l/Vhen thesending key K at station Xanda a hightreq the sending key at station Y are both closed, there is no carrier current on the line, and the receiving circuits at both stations are 1n condition for the rece tion of signals. If,

5 now, the operator at for instance, opens his k K and carrier; current from the oscillator tg is sent out-to produce a spacing signal at Y, the large transmitted current causes in efiect a short circuiting of the input of the rectifier 1);"81jt1th6 receiving relay R 1s, of

course, not operated; at Y, however the signal is received in the usual way. when the operator at Y wishes to break in, he opens his sending kgy, and carrier current from the oscillator at 18 sent into the line. As soon wthesemder at X closes the key K,thereceiving relay R, is operated to its spacing contact 'S, which connects positive battery to that armature. Withthis condition, no curwent flows in thesending loop through the resiatanee R because the ends of that circuit cnn'noct to equal potentials. Also,the current is reversed in the windings which are conthrough tht t esistance r to ground, 95 thus hoIdin the relayin marking condition aabefore. inoenopurrentflows in the subscrsiber'sloop, operation of his key has no ef- *feet; and the control ofthe circuit has passed ttt theoperator'at station Y. Thus it is seen so that the arrangementdisclosed meets the requirements of'hal f du lex operation.

@ 1 v ampi fier tube A serves to the shunt ng efiect resultin from the ionof tube D, from inter ering with as t? current transmitted to the line from oscildator 0. The sending amplifier tube A serves to stabilize? the impedance which terminates the oscililator clrcuit.

' While the invention has been disclosed in soj-onespecific embodimenttor the purpose of "illustration, itis-tebe understood that it is of embodiment-in other and difierent forms within the true scope of the invention Aasdeilnedin the dedclaims. is claims he carrier telegraph circuit, a sending *channel and a-recai ng channel in association with a transmission line, means assosaid sending channel for sending uency wavesthercover, receiving apperat usm said receiving channel, and a rectifier responsive to hi h frequency waves fiipting'in said sen' ing channel for dis- *saidreceiving apparatus.

w a carrier telegraph circuit, a sending chl,nnel and a receiving channel in association with a transmission line, an oscillator ass ociated' with said sending channel, a rereetifier and a relay controlled there'- may "in said receiving channel, and an auxthreeplecjtrode vacuum tube rectifier ted' with said receiving channel and its plate circuit'connected to form in effect a shuntimpedauee across the input of receiving rectifier, said auxiliary rectifier being biased so that plate current flows therein only when waves which originate in said oscillator flow in the circuit.

3. In a carrier telegraph circuit, a sending channel and a receiving channel in association with a transmission line, an oscillator associated with said sending channel, a sending relay controlling said sending channel to send out or cut off the waves originating in said oscillator, a receiving rectifier and-a receiving relay controlled thereby in said receiving channel, and an auxiliary three-electrode vacuum tube rectifier associated with said receiving channel and having its plate circuit bridged across the input of said receiving rectifier through a transformer, said auxiliary rectifier having its grid biased to prevent 'a flow of plate current in said rec tifier except when waves which originate in said oscillator are sent into the circuit.

4. In a carrier telegraph circuit, a sending channel and a receiving channel in association with a line, a source of carrier waves associated with said sending channel, a receiving rectifier and a relay co ntrolled thereby in said receiving channel, and an auxiliary three'elcctrode vacuum tube rectifier associated with the input of said receivingrectifier in such a manner that when no current flows in the plate circuit of said auxiliary rectifier no appreciable loss is introduced in said input, but when current flows in said plate circuit said input is in effect short-circuited, said auxiliary rectifier being biased so that normally no current flows in its plate circuit, but when a carrier wave is sent into the circuit from said oscillator, current flows in said plate circuit. 7

5. In a carrier telegraph circuit including a sending channel and a receiving channel in association with a transmission line, a source of carrier waves associated with said sending channel, a rectifier in said receiving channel and a receiving relay controlled thereby,

the method of accomplishing two-way transmission on a single carrier frequency which consists in bridging an Impedance across the input of the rectifier, adjusting said imped ance to introduce normally no appreciable loss 'in-said input, and causing a carrier wave from the source associated with the sending channel to reduce said impedance to introduce a loss in said input sufficient to prevent operation of the rectifier.

In testimony "whereof, I have signed my name to this specification this 11th day of March, 1929. V

. ROBERT H. CLAPP.

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