US1565155A

US1565155A - Carrier signaling- system

Info

Publication number: US1565155A
Authority: US
Publication date: 1925-12-08
Anticipated expiration: 1942-12-08

Description

Dec. 8, 1925. 1,565,155

J. S. JAMMER CARRIER SIGNALING SYSTEM Filed Sept. 20, 1923 5 Sheets-Sheet 1 Mg m E 3% 10 CS 2 r C E P M Q Q m E g D Q M i. E M

' L L m m Wye/71hr:

Jacob $.J0mmer.

' Dec. 8, 1925. 1,565,155

J. S. JAMMER CARRIER SIGNALING SYSTEM Filed t. 20. 1923 5 Sheets Sheet 3 m n //71/e/7/0/": Jami 3 Jam/11 er.

Dec 8, 1925. 1,565,155

J. 5. JAMMER CARRIER S IGNALING SYSTEM Filed Sept. 20, 1923 5 Sheets- She'et 4.

W i f Q 1 Myer? far:

Jacob S. Jammer by iu Affj/ Dec. 8 1925- 1,565,155

.1. S5. JAMMER 4 CARRIER SIGNALING SYSTEM I I Fi d s m zp. 1923 I I 5 Sheets-Sheet 5 J0c0b S. Jam/77 er b M Af/j/ Patented Dec. 8, 1925.

UNHTED STATES PATENT ()FFICE.

JACOB S. JAMMER, OZ NEW." YORK, N. Y.. ASSIGNOR TO VIESTERN ELECTRIC COMPANY,

INCORPORATED, OF NEW YURI". N.

Y., A CORPORATION OF NEW YORK.

CARRIER SIGNALING SYSTEM.

Application filed September T at whom it may concern Be it known that I, Jaoor. S. JAJIIMIlih, a citizen of the United States of America. residing at New York city, in the county of New York and State of New York, have invented certain new and useful Improvements in Carrier Signaling Systems of which the following is a full, clear, concise, and exact description.

This invention relates to a carrier signaling system.

Multiplex carrier telephone and carrier telegraph systems as heretofore employed extend between terminal stations from which radiate low frequency lines which are either permanently connected, one to each of the carrier channels with a multiplex system or any of which may be temporarily connected to any one of the carrier channels by the operators at the respective terminal stations.

In some multiplex systems where the low frequency lines are permanently coupled to the carrier channels of the multiplex system, the low frequency lines extend to other stations which are geographically separated.

For example, a multiplex carrier telephone system between Chicago, Illinois, and Harrisburg, Pennsylvania, has permanently coupled to the channels thereof low frequency lines extending from l'larrisburg to New York and Vashington. Frequently, when all of the usual channels to either point are busy, it is desired to obtain another channel to one or the other of said points.

In accordance with the present practice this is accomplished by calling. say, the New York operator who connects to the Chicago-New York channel. a low frequency line extending from New York to Vashington. This practice is not only cumbersome but time consuming and utilizes lines which should be available for other service. It is, therefore. desirable that in case, for example, the usual Chicagolvashington channels are busy, the Chicago operator be able to establish another channel between Chicago and lVashington without the necessity of going through the station at New York. This represents. of course, but one of many situations in which it would be desirable to control the establishment of a connection from a distance. over a desired carrier channel.

One of the objects of this invention, therefore, is to provide a multiplex carrier signaling system wherein any one of a plurality of low frequency lines radiating from one multiplex terminal station may be selected and coupled to a channel of the multiplex system under control of the other multiplex terminal station.

Other objects and features of the invention relate to the arrangements for selecting the desired radiating low frequency line and the proper balancing network therefor, to the signaling and busy test arrangements associated with the system.

lVhile the invention is being disclosed as applied to a multiplex carrier telephone sys tern, it will be understood that it may be applied to a multiplex carrier telegraph or other signaling systel'u.

In the drawings Figs. 1 and 2 when placed end to end in the order named, show a multiplex carrier telephone system and low frequency lines radiating from one of the terminal stations, either of two of which may be selected and coupled to a channel of the system.

Figs. 2-3, t and 5 when placed end to end in the order named, show a multiplex carrier telephone system similar to that of Figs. 1 and 2 but wherein a call may be initiated from either end.

The multiplex carrier telephone system of Figs. 1 and 2 comprises. in general. a high frequency main line ML extending between terminal stations X and Y. The apparatus located at station X is shown to the right of the dotted line in It while the apparatus located at station Y is shown to the left and below the dotted line in Fig. 2. The main line ML terminates at station X in a plurality of transmitting and receiving branches T0,. T0 and TC... and R0,, R0 and R0 and at station Y in similar transmitting and receiving branches.

Different carrier frequencies are employed for the different channels of the system.

The frequencies employed for transmission in one direction are comprised within an entirely different range from those employed for transmission in the opposite direction.

The transmitting branches are similar so a description of one will sullice.

Transmitting branch T0 includes a of the modulator M to which carrier current of the frequency assigned to the channel is supplied from the source 0 and a band filter TBF The modulator M may be of any well known type, such, for example, as the elec tronic valve modulator disclosed in Fig. 412 of the article entitled Carrier current telephony and telegraphy by Colpitts and Blackwell, published in the transactions of American Institute of Electrical Engineers, volume 40, 1921.

The filter TBF is of the type disclosed in the U. S. patent to Campbell, 1,227,113, May 22, 1917. It is designed to pass currents of the carrier frequency and of the frequen cies within either the upper or lower side band thereof and to suppress currents of all other frequencies.

The receiving branches are similar so that a description of one will suffice. v

The receiving branch RC includes a band filter RBF an amplifier A a demodulator DM and a low pass filter LPF The band filter REF is of the type disclosed in the Campbell patent supra and is designed to pass currents of the carrier frequency assigned to this channel and of the frequencies within the same side band as is transmitted by filter TBlF and to suppress currents of all other frequencies.

The amplifier A, and the demodulator DM may be of any well known type. such, for example, as those disclosed in Fig. 412 Colpitts and Blackwell article, supra.

The low pass filter LPF is of the type disclosed in the Campbell patent and is de signed to pass currents of frequencies below the upper limit of the voice range of frequencies and to suppress currents of higher frequencies.

Each pair of transmitting and receiving branches are similarly connected to a low frequency circuit. For example. the associated trai'ismitting and receiving branches TU and RC, are coupled to and conjugately related with respect to a low frequency circuit O by means of a three winding transformer 1 and a lnilancine artificial line or network N,.

The low frequency circuits C and (I, coupled to transmitting and receiving branches of the multiple); system at the sta tion X, may extend to and terminate in jacks at a switchboard in the usual manner. This switchboard may be located at the station X, or, at a distant station.

Likewise, each of the associated receiv ing and transmitting branches at station Y may be similarly connected to low frequency circuits. The low frequency circuits C and C are low frequency lines permanently connected to channels l o. 2 and No. 3

respectively. Line C extends to one disif muse lines have substantially different electrical chararten istics conmensation therefor may i=c ci'i'ccted in any desired manner, such for example as by employing ditl'erent balancing networks as will be described in connection with the system of lligs. 3, l and The low frequency circuit C, terminates in open contacts of two

relays

2 and 3 so that, upon the operation of either relay. the

low fret uenc i circuit C mat be ex aidl ed to the terminals of ack J, or J depending upon which relay operated.

N rmally carrier (urrent of the frequency assigned to chaimel No. l and of the upper magnitude, as explained below is flowing therethrough from station K to station Y. This current is rectified by the rectifier R associated with receiving? branch R C,. The result-in; rectil'icd current flows through relay t. causing it to hold its armature in inid-positimi between the two contacts associated therewith. The magnitude of this curl. t is controlled by a resistance 5 normally bride-god oss the output of modulator through the center, of relay 6 which is normally cneru'ized.

telay controls selecting and coupliiuz; means comprising relays which se ect the desired low frequency line and connect the same to the low frequency circu ts C' The low frequency lines subject to selection are lines L and la the former ortcndingr to New York, for examp e. and the latter to Washington. Each of these lines iiGYllii nates in a jack (i (only one of which is shown) which has associated therewith nnal receiving n'ieans.

The operator at the station who-re the jacks in Fig. terminate. desiring to ostablish a connection to l l ashinu'ton by way of the high frequency channel with which either of the low frcquencr lines and B, may be associated, inserts the pine; P of cord circuit CC into jack J Relay 3 thereupon operates connecting the low 'lrmuenry (in cuit G, to the tip and rinp' termina s of the jack and operating busy na s lit? associated with the. iacks. the actuation of ringing; key iirircsses a source of low frequency si ialin; ('1, "went onto relay 16 and cans s the operation thereof. The

relay 6 -which removes resi,

lli

bridged relation to the output of modulator M -rs a result of this action the r tutle of the carrier it transmiterl through the channel is eased and the amount of rectified current throinrh relax l increases. Relay -i.- thereupon closes left-hand contact causing the operation of relays T and Relay t locks up it a contact thereof and the closed cont: relay 9. The operation of relay 53 selects the low frequency line i and connects the same to the low it'requeiicp' circuit A busy tone from source Bi normally connected to the low freipicm-y lines is discennected from line L, by the operation of relay h.

The operation of relay l causes the eucr-- gization of relay it) which connects a source of signaling current 1t to the selected low frequency line i causing the operation of relay 1) associated with jack 3. The operation of rel 12 lights signal lamp 1 3 and energizes r l4- u'hich lorlrs up through its contact and the contact of relay 1%.

Upon the restoration of the ringing key .RK to its normal position. relay 16 releases and relay 6 operates, again bridging resistance 5 across the output of modulator M In response thereto relay 4 allows its armature to return to the mid-position between the contacts associated therewith whereupon relays 7 and 10 release. Ringing current 11 is. therefore. disconnected from the line L which is then connected through the contacts of

relays

8 and 10 to the line windings of the three-winding transformer which in turn couples the low frequency line L to the associated transmitting and receiving branches T C and R of the multiplex system.

The operator at the distant end of the low frequency line L upon observing the lighted condition of the signal lamp 13 may insert the plug of a cord circuit, similar to that shown in Fig. 1. into the jack J to answer the call. Relay 15 thereupon operates. opening the locking circuit (if-relay 14 which releases. extinguishing the lamp 13. The operator at the distant station associated with low frequency line T11 may then communicate with the operator at the other station and receive instructions for completing the de ired connection. after the establishment of which. conversation may take place in the oroinary manner usual to multiplex carrier telephone systems.

At the conclusion of the conversation, the operators withdraw the plugs from the jacks, whereupon relays 3 and 15 return to their normal condition. Relay 8, however, remains locked up so that the low frequency line L remains coupled to the transmitting and receiving branches T C and B C of the channel of the multiplex system.

Should the operator now desire to establish connection over the low frequency line L the plug P is inserted in the jack J ltelay 2 thereupon operates, connecting the low frequency circuit C through to the tip and ring terminals of the jack J and operating the busy signals BS. The actuation of ringing key 11K operates relay 16 which releases relay 1?. Relay 17 thereupon closes its contact which places a short-circuit across the output of the modulator M and reduces to nil the magnitude of carrier current transmitted through the channel. The mag nitude of the rectified current through relay 4; is, therefore, reduced thereby allowing the armature of the relay to close its right-hand contact. Relays 1S and 9 then operate. Relay 18 locks up through one of its contacts and the closed contact of relay 7. The operation of relay 9 opens the locking circuit of relay 8 which thereupon disconnects low frequency line L from circuit C Relay 18, in operating, connects low frequency line L to the low frequency circuit C Relay 9 in closing its front contact, energizes relay 10 which connects ringing current from the source 11 to the low frequency line L. and operates the ringing response relay associated with the jack at the distant end thereof, whereupon the signal lamp thereat is lighted. The restoration of the ringing key to normal position releases relay 16, energizes

relays

17 and 4 and deenergizes relays 9 and 10.

The multiplex carrier telephone system of Figs. 3, 4 and 5 is similar to that of Figs. 1 and 2 in that it comprises a high frequency main line ML terminating at two geographically separated terminal stations W and E in a plurality of transmitting and receiving branches which are associated in pairs, each pair of which may be coupled to a low frequency circuit or line.

At each terminal, the transmitting and receiving branches are coupled to the main.

line Mli through a three-winding transformer T, one winding of which is in series with the main line. The second winding is connected to the band filters of the transmitting branches and the third winding is connected to the receiving branches.

This system, as illustrated, has three channels. Two of these channels No. 2 and No. are coupled in the usual manner through three-winding transformers to low frequency lines EFL and IJFIJ extending from the termina station and lines LFTF and Fifi extending from station E.

Different carrier frequencies are employed for the different channels of the system. The frequencies employed for transmission in one direction are comprised within an entirely different range from those employed for transmission in the opposite direction.

llach end of channels No. 2 and No. 3 is equipped with means whereby signals incoming over the low frequency line may be translated into signals outgoing over the high. frequency line and for translating the signals incoming over the high frequency line into signals outgoing over the low frequency line. Since this equipment for each end of the two channels is alike, it is shown in detail in connection with only one channel and at one ei'ad thereof only.

This signaling" transmitting equipment may he described in connection with the operation. Thus, low frequency signaling;- current ineoinin to the multiple; terminal station over low frequency line LFL operates relay thereby causing the release of relays 2G and 27. The resultant closure of the contact of relay 2? short-circuits the output circuit of the modulator M thereby preventing the flow of carrier current of the frequency assigned to this channel over the main line. ll heu a ringing; signal is incoming over the main line. as indicated by the absence of carrier current therefrom relay 28 in the output circuit of rectifier ll releases causing the energization of relay 99 which thereupon closes its contacts. The 010- sure of the right-hand contact short-circuits the llllClDOliltSll'lf the line windings of the hybrid coil thereby preventing singing during the ringing operation. The closure of the left-hand contact operates relay 30 which connects a source of ringing current 31 to the low frequency line LFL Channel. l lo. 1 of the multiplex carrier telephone system illustrated in Figs. 3, iaud 5 has associated therewith apparatus and circuits so organized that any one 0t live low frequency circuits four outgoing and one incoming, may be coupled to the carrier channel at the terminal station W. At the terminal station E there is provided apparatus controlled from terminal station ll for selectinp any one ot four outgoing); low frequency lines, applying low frequency ringing signaling current to the selected low frequency liiio, applying a busy tone to a non-selected low frequency line, selecting: and connecting the proper balancing network to the selected low frequency line and finally connecting the selected low frequency line and its balancing); network to channel No. l. The selection is effected by shifting the frequency of. the carrier current transmitted over the main line ML and selectively operating; at the distant terminal receiving relays associated With rectifiers coupled to the channel through selective circuits.

The operator at terminal station W des ring to establish connection by way of channel No. over the low frequency line All extending: from station E to a distant station, may insert the plu o a cord circuit, similar to that shown in s 1 into jack A thereby causing; the operation of relay 32. Relay operates lousy signals BS associated with each of the jacks A to E inclusive and also operates relay Relay 33 connects the tip and ring terminals of jack A to the line windings of the three-winding transformer 1. Relay 3% also causes the operation of relay ill over circuit including ground connection which thereupon closes the filament circuit of the electronic ralre of oscillator Flt) which renders the oscillator active in the generation of oscillations of the frequency assigned to channel No. l for transmission over the main line fi nu station il to station E. Carrier current of the fl'fiiltlcllty generated by oscillator SO and tinnsinitted orer the main lino hill is selected by the tuned circuit TC and impressed upon the rectifier ll. The resul ant rectified current flowing in the output circuit of the rectifier energizes relay 35 whereupon relay releases and relay 8? 0pcrates. llelay 37, in operating, closes the filament circuits of rectifiers All. BR, CR and DR.

After the insertion of the plug in the ack A, the ringing;- key of the associated cord circuit is actuated causing the operation of relay 38. The operation of relay 3% causes the energization of relay 39 which connects condenser 40 in parallel with the condenser of the frequency determining circuit associated with the oscillator, thus changing the i? .quency of the current generated thereby. The oscillator now generates and tnnsmits over the main line current of different frequency which is selected by the tuned circuit Afltl and impressed upon the rectifier All. The resultant rectified current in the output circuit of the retifier All causes the operation of relay l1. Relays l2 and 4:3 thereupon operate. l-lelay 4-2 selects lou frequency line All, and causes the operation of relay (31 which short circuits a winding of transformer 4-4: to prevent singing during the ringing operation. At the time of the cluuine in frequency of the current generated by the oscillator. relay35 releases and relay 36 operates. Relay illbeinga slow release relay holds up until relay 43 operates and su mlies a ground for com )letin the lockino' a. t tn a circuit of relay 37. Relay 43, in operating, locks up over a circuit including one of its contacts and the contact of relay 36. The operation of relay 4? also causes the operation of relay All which connects in series with the line windings of the three-Winding transformer all a balancing; network NA to balance the selected low frequency line All.

The operation of relay 4.3 also causes the operation of relays 45 58 62 and 63. litelay 4-5 connects a source of ringing current 4-6 to the selected low frequency line AL. Relays 58 62 and 63 connect a busy tone from source BT to the non-selected low frequency lines BL. Cl] and DL. The distant end of the low frequency line AL is teriniated in a jack similar to jack J shown in ltlll Fig. 2 and has associated therewith similar signal receiving apparatus so that in response to the connection of ringin current from source to the selected low frequency line All, the signal lamp at the distant end thereof is lighted.

Upon restoration of the ringing key to normal position, relay 38 releases thereby releasing relay 39 which shifts the frequency of the current generated by the oscillator back to normal. Relay 41 thereupon releases and relay operates. Upon the operation of relay 35, relay 36 releases but relay 36 is slow to release so that a ground is substituted at a front contact of relay 45 before being removed at the contact of relay 36.. whereby relays 43, AN, 45, 58, 62 and 63 remain locked up. Relay 42, however, controlled through a contact of relay 41 releases thereby disconnecting ringing current from the low frequency line AL and connecting this line through to the three-wind ing transformer 44. Relay 61 releases when relay 42 releases.

he operator at the distant end of the selected and connected low frequency line AL observing the lighted condition of the lamp associated therewith, may connect to the jack the plug of a cord circuit similar to that shown in Fig. 1 and communicate with the operator at the initiating terminal to receive instructions as to the number of the line to which connection is desired. Since the oscillator SO and the modulator M are active normally, they are in readiness to transmit the return speech from station E to station TV as soon as the operator at the distant station on line AL begins to talk.

After the completion of the connection between the calling and called parties conycrsation may ensue at the conclusion of which the operator at station W and at the distant end of the low frequency line AL may withdraw the plugs from the jacks to restore the apparatus of the system to normal condition. Then the plug at station is withdrawn from jack A, relays 32 and 34 release, thereby disabling the oscillator SO. Since no current is now being transmitted by the oscillator SO, relay 35 releases and relay 36 operates. Between the time of the opening of a contact of relay-35 and the closure of the contact of relay 36, relay 43 releases whereupon relay 37 releases opening the filament circuit of the rectifiers AR, BR, CR and DR. The release of relay 43 also causes the release of relays AN, 45, 58, 62 and 63. Since relay 37 is held up until the operator at station XV withdraws the plug of her cord circuit in taking down the connection, the rectifiers AR, BR, etc. are held in readiness to respond in case of a recall by the operator at station V. This can be done by merely actuating the ringing key in the operators cord circuit at station W, without having first to withdraw the plug.

The oscillator SO furnishes current of the normal frequency when none of the condensers 40, 40", 40 or 40 is connected in parallel with the condenser of the frequency determining circuit. This normal frequency is the carrier frequency assigned to channel No. l for transmission from west to east. An oscillator S0 at the station E furnishes carrier current of the frequency assigned to channel No. 1 for transmission from east to west. This oscillator, SO, as stated, is normally operative so that current of the frequency supplied thereby is normally flowing over the main line ML and this current is selected by the receiving band filter RBI? passes tnrough the demodulator DM the amplifier A and the high pass filter HPF and is delivered into the input circuit of rectifier R Relay 47 is, therefore, energized by rectified current in the output circuit of the rectifier and remains energized so long as carrier current is being transmitted over the main line from the oscillator SO.

Should a call originate at the distant end of the low frequency line AL, the plug of the cord circuit thereat is inserted into the jack and the ringing key associated with the cord circuit is actuated. Relay 48 responds to the ringing current and in responding causes the operation of relays 43, AN, 45 and 49. Relay 43 locks up over a circuitincluding the contact of energized relay 36 and also maintains relays AN and 45 in locked up condition. The operation of relay 43 causes the operation of relays 58, 62 and 63 which connect a busy tone into low frequency lines BL, CL and DL. The operation of relay 49 short-circuits the output of modulator M thereby stopping the transmission of carrier current from oscillator SO to the main line. Relay 47 in the output circuit of rectifier R therefore releases and causes the operation of relay 50 and the lighting of signal lamp 51. Relay 50 looks up through the closed contact of relay 52 and maintains the lamp in a lighted condition.

Upon the restoration of the ringing key to normal position, relay 48 releases thereby causing the release of relay 49 which, in turn, allows relay 47 to operate.

The operator at station V observing the lighted condition of lamp 51 inserts into the answering jack E, the plug of the cord circuit similar to that shown in Fig. 1 whereupon relay 52 operates opening the locking circuit of relay 50 and extinguishing lamp 51. The busy signals BS associated with the calling jacks A, B, C and D and the answering jack E, are operated upon the energization of relay 52. The operation of relay 52 also causes the operation of relay 34 which relay 3? and to furnish a ground for the locking circuit of relay 43 which ground is substituted :tor that contact of relay 3o. lay 3t} releases upon the operation 0'? relay m4.

rnished through the but being slow to release, this contact does not open until utter the closure of the contacts of i 85. 'ihus the locking circuit of rela 'ntained.

i l-it the conclusion of the cr ation, the

pin -s are Withdrawn train the apparatus is restored to noru'ial condition in the manner previously dose.

l desire "5 channel he plus jack B the op iflhould the opera tor at st:- to establish a connection by N0. 1 to the low trequency line El. t of the cord circuit is inserted in the whereupon relay 52% operates, causing eration of the busy signals and relay o l. llelay connects the tip and ring tel-ininals of jack B to the line windings ot transformer 1 and causes the operation of relay 3% which starts the oscillator Stil The oscillator SO generates and transi'nits over the line carrier curre which is selected by the high pass filter liPF and the tuned circuit TU. Relays 35 and 3'? operate and relay releases as before.

The ope 'ator actuates the ringing ltcy of the cord circuit Where ipon relay 55 r sponds, czrusinp, the operation of relay 56 which connects condenser 40" in parellel with the condenser of the oscillator quency determining circuit. The frequency oi the current gene *atcd by the oscillator is thcreliy shifted and tunei'l circuit C lects this shittcd ti .c ucncy current and recti tier rectilies the same. The resultant roctiiicd current operates relay 5? which :auses the operation or renys 5e and 59. ltclay 58 selects low frequency line BL. and auses the operation of relay ()1. Relay 59 loci-Is up over a circuit 'inchulin the contact of relay Which now o ted. ay 59 causes the operation ct re '2 l, 42, 62 and ('33. All of these rela now locked up, due to the fact that relay is locked up. Relay 60 connects ringing curi nt to the selected low irctpiency line Pill which lights the si nal lanip at the other end. Relay Bil con nects balancing network ell in series with the line windings ott transtornier 4: 1 to halance the selected low frequency line BL. liel: I 62 and connect a source of lousy tone .l to the non-selected low frequency lines AL CL and Dill.

Upon restoration of the ringing key to normal position, relays 55 and 56 release. The frequency of the current generated by the oscillator S0 is thereby shifted hack to normal so that in response thereto relay 5'? release" and relay 35 operates. Relays 58 and 61 release on the release oil relay but relay and those relays dependent thereon remain operated because a ground tor its locking circuit established at the contact of relay hetore being removed at the contact oil" slow release relay Further extension ot the connection may now be made in the manner previously described utter which conversation may ensue. it the couch sion oi conversation, the plug is Withdrawn and the apparaus restored to norn'ial condition as in the manner previously described.

frlhould the operator at station l f insert the plug into yicl; C. the low frequency line "ll will he select on. tor. upon the insertion of the pin relay (it operates causing the opi? relay (35. which. in turn. operates 1nd starts the oscill tor SO. lieand 37 then operate and relay 36 rein response to the actuation of the lzey ot the connected cord circuit. operates causing the operation of ay which connects condenser 40 in the queue; dctcri'i'iininp; circuit of the oscil- The "frequency ot the oscillator is thus shitte l. Current out the shifted trequency is selected iy ed circuit ETC and rectified by rectifier is and the resultant recti 'ed nt operates relay 68, Whereupon 1' and t? opera-it Che operaselects low "requency line 1 Relay 89, in op tion of re.

and operates elay (5i.

i crating, loclzs up in the manner described in cor i tl it and operates res lays 58 and uczun network inc wi 111i. balance the selected lounelay 4O (OHUGCL ringselected low tlrequcucy tic '. 't 11- the ringing hey to normal positioin relays (32. (ll. ant. 8 relea-isei relay 35 operates and rcday 3") releases.

t be selected by "he ul' it our t ot the cord circui into The insc 'on or": the p ug iito the :1 uses the operation of relay it which. ii to. operates relay T2. Relay operat. lav B-lto start the oscillator. ll'cla: y 35' and iii t'unction a. before descr he actuation of the ringing key 1. ot the connected cord cir "uit causes the re IOl lay Tl. Relays 63 and thereupon opcrate. Reta 63 selects the low fre iiency line DL and operates relay til. llelay T5, in operating, causes the operation of relays DE, 7c, 42, 5S and $2. Relay DN connects balancing network ND in circuit with the line windings of transformer it to balance the low frequency line Dli. Relay in connects ringing current to the selected low fre quency line. Relays 1:2, as and 62 connect the ousv tone source to the nonselected low frequency lines. Upon restoration of the ringing key to normal position, relays 72, 73, ii, 6 3 and 61 release, relay 35 operates and relay S6 releases.

Should a call originate at the distant end of low frequency line ISL. CL or Dli, the apparatus associated wit 1 the line on which the call originates operates as described in connection with line All to operate the signal 'eiving apparatus associated with the receiving jack E.

lr'hile only one channel of the multiplex carrier telephone em has been shown as equipped with apparatus for selecting any one of a plurality of low frequency lines, signaling thereover and connecting the same to the channel of the multiple): system, other channels may be similarly equipped, if desired.

Likewise, in the system of Figs. 1 and other channels of the multiplex carrier telephone system shown therein may be equipped with selecting mechanism similar to that illustrated in connection with one of the channels. The channels of the multiple; system (Figs. 1. and not equipped with selcctin mechanism may he equipped with signaling mechanism such as disclosed in detail in connection with the west terminal oi channel IJFL in Fig. 23.

lhe invention set forth herein is. of course. susceptible of various other embodiments and applications.

I claim:

1. In a carrier wave signaling system, a carrier wave channel, stations in which said channel terminates, a modulator at one tion, a detector at another station, a plurality of low-frequency terminal circuits adapted to be operatively associated with said modulator, a corresponding plurality of low-frequency terminal circuits adapted to be operatively associated with said detector, and means controlled in response to the taltinp; for use of one of the first-mensociating it with the modulator and for operatively associating one of the secondmentioned plurality of terminal circuits with the detector.

2. In a signaling system. a two-way carrier wave channel terminating in respective stations, a modulator and a detector asso ciated with said channel at each station, a plurality of low-frequency terminal circuits at each station arranged for connection with the respective modulator and detector for repeating into and receiving from the carrier wave channel, and means controlled in response to the taking for use of one of the l()\\-fl(]ll0llt}' terminal circuits at one station for operatively associating it with the modulator and detector of that station and for operativcly associating one of the lowfrequency terminal circuits at the other station with the modulator and detector of that station.

3. In a carrier wave transmission system. a carrier wave channel terminating at each end in carrier signaling apparatus, a plurality of lowfrequency terminating circuits adapted for interclumgeable connection to the carrier signaling apparatus at each terminal of the channel, an operators cord circuit including a key, means to connect the cord circuit to any of the terminal circuits at one station, and means controlled in response to the connection of the cord circuit to a particular one of said terminal circuits and to the actuation of said key for connecting to the carrier signaling apparatus at the distant end of the channel the corresponding terminal circuit thereat.

4. In a carrier telephone system, a carrier telephone channel, a detector therefor, a pluralitv of frequency selective circuits associated with the detector, a plurality of tele phone lines, means controllable over said channel and including said detector for selectively operating certain of said selective circuits to connect a desired telephone line to said detector, and means for transmitting speech over said channel and the connected line.

5. In combination, a carrier wave channel including a modulator at one terminal and a detector at the other terminal, a plurality of terminal circuits at each terminal adapted for connection respectively to the modulator and to the detector. and means including said channel and one of the terminal circuits connectible to the modulator for controlling connection of one of the terminal circuits to the detector, the particular terminal circuit connected to the detector being dependent upon the terminal circuit over which the control is exercised.

6. In combination, a carrier wave channel, a detector therefor, a plurality of terminal circuits connectible interchangeably to said tioned terminal circuits for operatively its-detector, and means controlled in response llO to toe fre uency of the were transmitted over said channel for selecting and conne ing one of the terminal circuits to the de tector.

T. It a conni'iunicat" i an, a carrier wave channel terminating at one tation in a detector, a group of lines ada ed for con nection interchangealiily with said. detector, means controllable over saml channel t'or selecting; a line and coni'zecting it to the detector, and means to indicate all of the re maining lines of the area as inaccessilfe.

8. in a coininuni ating; system, a carrier Wave channel. a group ot lines adapted for operative association interci"oigeahly with said channel, and means controllable over any line for opera'ively z. ,ociating it with the channel an for iii-{rivaling all of the remaining lines oi the group as inaccessible.

9. In a communicating a carrier Wave channel, inc-ans to'ti 'iyely d1 1 z erent over the channel wares frequency characteristics rier Wave controlled hy the signals to he sent, a detector tor said cha e W Hin- l, a plurality ot tern'unatinp; lines adapt.. l tor selectiic connection to said detector, nieans coir trolhhle by Waves transinittec over the channel and dependent upon the treipiency characte "istics of the vave for selecting; and connecting; ore of the terminating lines to the detector, and means operating in response to the 0k 'rier Way tor maintaining the selected line connected during the transn'iission of signals.

10. in a signaling system, a carrier Wave channel terminating; in a detector a plurality of terminal circuits adapted for interchangeable connection to said detector, means controllable over said channel for selecting and connecfing to the detector one of said terminal circuits, :1 id means responsive to the selection of such circuit for applying signaling current thereto and indi cating the remaining lines as inaccessible.

ll. In a communicating; system, a carrier Wave channel, terminating in a detector, plurality of ter ninal lines adapted for intcrchangeahle connection to said channel, a plurality oi? irequency-selective circuits operativcl i c ntrol ot the carrier Wave.

in, a con'intruncating; system, a carrier rare channel means to tr; isinit a carrier Wes oi characteristics ware and iii the r-cover, a lurality of terminal circuits connectihle to said channel,

means actuated ii. response to receipt of the cari 'icr ware tor enerp other W rig the selective inca s, means to cause the selective means to select and ccnnect to the channel a deed one of the il circuits, anti means lining the connection er wave. '21 signaling system, a trezctiye ca'rier transmission chan- I ns to transmit a "\VflVQ ot a particular t'requeuc i'lll'O'tigll said channel contiinioiissly daring signaling periods, a plurality of terminal circuits, and means for transmitting waves 01 other frequencies Within the transmissimi frequency range of said channel dirinp' nonslgnalinp; periods or opcrztirely associating a selected one 01": said terminal circuits With said channel.

let. it multiplex carrier telephone system comprising a high frequency main line extending between two stations Vt and E, a plurality of low frequency lines radiating from station E, a plurality of balancing net worl-rs, one for each of the low frequency lines, and means at station controlled over the main line from station W tor selecting one of the low 'treqiiieney lines and its balancing network and coupling the same to one of the channels of the systen'i.

In witness whereof, it hereunto subscribe n y name this 12th day 0 September, A. D.

selective means,