US2240676A - Train telephone system - Google Patents

Description

May 6, 1941. A. G. sHAvER TRAIN TELEPHONE SYSTEM Filed slept. 7, 192s /N VEN TOR Arch/'bald 6. :Shaver Patented May 6, 1941 UNITED STTES PATENT OFFICE 36 Claims.

This invention relates to a system for carrying on communication between different parts of a railway train; between the wayside and a railway train; and between two or more railway trains operating on the same track system. The system is adapted to accomplish these purposes whether the train is moving or standing still.

In its practical application this system may serve several purposes. A person on one part of a train, as the engineman on the head of the train, may communicate with another person on some other part of the train, as the conductor on the rear of the train. Passengers on trains may communicate with their homes and oilices, or be communicated with from those places. Railway train dispatchers in charge of the dispatching of trains may communicate directly 'to and receive communications directly from those in charge of the operation on the trains. Crews and passengers on a train may exchange communication with the crews and passengers of another nearby train on the same railroad.

It is now the prevailing practice in train operation for the conductor and engineman to communicate with each other, especially while the train is moving, by a system of visual and audible signals, conducted by hand, flag and whistle. In the case of long freight'trains such means of communication as now practiced are inadequate and very unsatisfactory.

Under existing conditions passengers on moving trains are unable to communicate with their homes and oflices, or to be communicated with, except as their train may stop at some wayside station where means for communication are available.

A t the present time train dispatchers transmit instructions for a train to operators in wayside stations where such instructions are written up and then handed to one of the crew as the train passes said station.

Where two trains are running near together, the only means now practicable for communication between them are by messenger or by visual and audible signals which means are inadequate and unsatisfactory.

'I'he means provided in this invention greatly improve upon the methods of communication now practiced in connection with railway trains. Its use will provide greater safety and less expense in the operation of trains; business generally will be benefited; and passengers on trains will be greatly convenienced.

The general object of the present invention is to provide improved communicating means, of the character described in my copending application, Serial No. 227,932, filed October 22, 1927, in which communication may take place between the engineman at the head of the train and the conductor at the rear of the train; or between either of these latter two, or both of them, and the train dispatcher, while the train is moving or standing still and the dispatcher is in his oilice.

Another object of the present invention relates to the provision of means admitting of a considerable variation in air gap between the collecting coils, or inductors, carried by the train and the track rails without noticeably affecting the eiliciency of the communication.

Another object is to provide means by which signals may be transmitted from the roadside to the train, and vice versa, to call the party wanted.

Another object is to provide for the simultaneous transmission and reception of communication signals.

Another object is to provide means for mini mizing the eilect of foreign inductive disturbances, particularly those due to conductors on adjacent pole lines.

An additional object is to provide means in the intermediate circuit for maintaining one transformer connecting coil only in said circuit, as the train travels over the railroad, thus maintaining an approximately constant impedance in said circuit.

A further object is to provide means for making communication, particularly telephone conversation, possible under a variety of conditions existing as regards electric currents in the track rails.

In the operation of this system for communicating between the two ends of a railway train three principal elements or :features are concerned-a, transmitting and receiving equipment on one end of the train; an identical transmitting and receiving equipment on the other end of the train; and an intermediate circuit on the trackcenter about a resonated inductor circuit in the .transmission and reception on the train, a means for signaling between the train stations and between the latter andthe wayside stations, a combined transmission and reception circuit, ampli- Iication of the communication signals, means associated with the intermediate circuit for maintaining an approximately uniform impedance condition as relates to transformer connection for wayside stations; means for minimizing objectionable inductive disturbances, etc.

In the accompanying drawing, which shows a preferred embodiment of the invention:

Figure 1 is a diagrammatic arrangement of the circuits and equipment on one end of the train.

The set of equipment on the other end of the train is identical to that shown in Figure l.

Figure 2 is a diagrammatic showing of the circuits and equipment on the track connected with the circuits and equipment in the dispatchers oiiice, or other wayside stations, for a portion of an equipped railroad.

Figure 3 is a diagrammatic showing of a single intermediate circuit with the front and rear ends of the train represented, and a connection for a wIayside station. The intermediate circuit is here applied to a railroad with alternating current in the track rails for other than communicating purposes, as railway block signaling. 'Ihe track rails may also carry direct current for propulsion purposes.

Figure 4 is a schematic diagram showing the wayside transmitting and receiving station conb nected directly in the intermediate circuit.

Figure 5 is a diagram showing a. preferred and optional arrangement for the operation of the signal, in calling a party Wanted.

Figure 6 shows in detail the arrangement for the system is adaptable for other methods of communication such as will hereinafter be explained. The circuits are shown in the various figures as they exist normally.

In Figure 1, IND is an in ductor comprising, usually, a laminated iron core upon which a coil of wire is Wound. For high radio frequencies the coil alone, without the laminated iron core, may be used. G is a source of energy, preferably alternating or pulsating electric current. S is a switch of the telegraph or push key type normally maintaining contact 'l closed and Contact 8 open. T is a telephone transmitter. PI and P3 are transformers. UI and U3 are amplifying tubes. C is a switch of the type generally used in telephony for holding the receiver, and normally it holds contact 22 closed and 23 open. H is a signaling means, being of the type of a howler, a relay with a bell, preferably a time relay with a bell or horn, or a horn similar to a loud speaker. R is a receiver of the usual telephone type or it may be a loud speaker. Q is a battery for the transmitter circuit. AB Is an A" battery for energizing the filaments and BB is the B battery for the plates of the amplifying tubes. AR is a switch, including an adjustable resistance, for controlling the amount of current passing from battery AB to the laments of tubes UI and U3. ST is a switch for adjusting the number of turns of the inductor IND in the transmitting circuit. M is a switch closed only when the transmitter is being used, thus saving battery Q. 3, 2l and 4 are condensers across the coils I, I plus 29, and I plus 29 plus 2 respectively. N is a condenser to keep direct current out of the receiving circuit and to increase the transmitting power of the transmitter; also, being adjustable, it may be used to vary the impedance of the receiving circuit and to increase or decrease the volume of the reception. It is intended also as a filter for certain frequencies. l

The circuits and equipment shown within the boundary line BDYI represent the mechanism carried on the train where there is but one set on the train. Where there are two sets of equipment on the train, as one at the head and one at the rear of the train, both sets are like that shown.

The transmission signaling circuit on the train comprises, generator G, contact 8 closed, switch S, conductor 9, coils I plus 29 plus 2 and conductors 5 and I0.

The transmission telephone circuit on the train comprises, battery Q, switch ST, conductor 59, coil I of inductor IND, conductor 9, switch S, contact 'l closed, conductor 25, transmitter T, conductor 26 and switch M closed. In case it is desired to change the number of inductor turns in the transmission circuit, switch ST is shifted to conductor 28 so that the effective coil of iri ductor IND is I plus 29. In practice it has been found that fewer turns in the coil of the inductor IND are required for good results in transmission than are required in the same inductor for good reception. The condensers 3 in parallel with coil I and 2l in parallel with coils I plus 29 are of capacity to produce a near state of resonance in the respective transmitting circuits, thus aiding to produce quality and volume in the transmitted voice currents.

The receiving signaling circuit on the train for the signaling energy originating on the other end of the train or in the wayside station, which is picked up by the inductor IND, comprises coils I plus 29 plus 2, conductor 9, contact 1, closed, of switch S, conductor 6, condenser N, transformer PI, and conductor 5. Through transformer PI this signaling energy is delivered to the amplifying unit and transmitted as amplified energy to the signaling device H.

The receiving telephone circuit on the train is the same as that described above for signaling reception, but the amplified voice currents are passed through the receiver R when the contact 23 is closed, as by removing the receiver from the hook of switch C. The condenser 4 is arranged across the coil I plus 29 plus 2 and is of a capacity to produce a near state of resonance in the inductor circuit for transmission of the signaling current and for the reception. With the condenser connected as described satisfactory results are obtained in voice reception.

While I have shown condensers in parallel with the inductor coils. I do not wish to be restricted to this arrangement for condensers connected in series with the inductor coils will give satisfactory results. I may also find it convenient to use adjustable rather than fixed .condensers.

In the amplifying means shown in Figure 1 (also in Figure 2), two three-electrode vacuum tubes are employed giving two stages of audio frequency amplication. As is customary in this well known style of amplification, the plate cir- 'cuitrof the rst tube is coupled by a transformer, designed for audio frequency, to the grid circuit of the second tube; and an adjustable switch controls the amount of current passing to the laments of the tubes, thus also controlling the wish to be restricted in this invention to the use of only two stages of amplification nor to the amplifying means and methods shown.

I have, also, shown condenser N of the adjustable type; but it is expected that the conditions relating to the transmission and reception will be suficiently uniform so that when the proper capacitance and inductance areonce xed, there will be no need for adjustment thereafter.

In Figure 2, that part of the equipment and circuit within the boundary line BDY2 is the transmitting and receiving set in the dispatchers office or wayside station. With the exception of the selective equipment DSE, the circuit and general arrangement of apparatus is practically identical with that of the train carried station sets. In the wayside station instead of the transmitting and receiving circuits connecting to an inductor, they connect directly to line conductors DI and D2 which are carried along the railroad and which will be hereinafter referred to. SI is a switch of the telegraph or push key type normally holding contact 83 closed and 84 open. TI is a telephone transmitter. MI is a switch closed only when the transmitter is being used, thus saving battery QI. P2 and P4 are transformers. U2 andvU4 are amplifying tubes. CI is a switch of the type generally used in telephony for holding the receiver, and normally it holds contact IOI closed and |02 open. HI is a signaling responsive means, being of some one of the several types mentioned for H. RI is a receiver of the telephone type and may be a loud speaker if preferred. QI is a battery for the transmitter circuit. ABI and BBI are respectively batteries for the filament and plates of the amplifying tubes. ARI is a 4switch including an adjustable resistance, for controlling the amount of current passing fromfbattery ABI to the filaments of tubes U2 and U4. GIv is a source of energy, preferably alternating or pulsating current, for the signaling features of the system. NI is a condenser of the adjustable type primarily intended to keep direct current out of the receiving circuit and to give resonance to the wayside receiving circuit. As is evident, NI

The transmission telephone circuit for the wayside station comprises battery QI, transmitter TI, conductors 88 and 8|, line conductor D2,

conductor 54, transformer TE, condenser EC, conductor 55, line conductor DI conductor 82,

switch SI, contact 83 closed. conductor 86 and switch MI closed.

The receiving signaling circuit for the wayside station for signaling energy originating on the Y removing the receiver from the hook of switch CI.

may be operated to vary the impedance of the v receiving circuit. J is a switch for convenience in disconnecting the station equipment from the conductors DI and D2.

The transmission signaling circuit for the wayside station comprises generator GI, contact 84 closed, switch SI, conductor 82, line conductor DI, conductor 55, condenser EC, tracksidel transformer TE, conductor 54, line conductor D2, conductors 8| and 89.

The medium for carrying on communication between the train and the wayside station is a series of circuits designated as intermediate circuits each of which consists of a conductor, usually a line wire, connecting to the ends of a block or district or section of track rails andforming a complete circuit. In Figure 2, TR are the bonded rails of a track with insulated joints as 24 dividing the track into' sections and subsections, such as A, B, C, D, E, F and G of which subsections B-C, D-E and F-G form in each case a block, district or section and subsection A is of another block, district or section. Condenser means for conducting the communicating currents around the insulated joints, which are included in the rail portions TR of the interme- J diate circuits', are hereinafter referred to. Two complete intermediate circuits and parts of two others are illustrated. The complete intermediate circuits illustrative of such circuits in general, comprise subsections such as B and C for one and D and E for the other. The intermediate circuit B-C includes track rails TR and condensers TK around the insulated joints, c ondensers AK, conductor 30, front contact 3|, conductors 33 and L, conductor 42, transformer TC, conductor 43, front contact 4I, conductor 40 and condensers AC to the track rails. The intermediate circuit D-E comprises track rails TR. and condensers TK around the insulated joints, condensers AC, conductor 40, front contact 4I, conductors 43, L, and 52, transformer TE, conductor 53, front contact 5I conductor 50, and condensers AE to the track rails.

'I'he intermediate circuit A, which is but partially shown, includes the track rails TR, condensers AK, conductor 30, contact 3|, conductor 33, transformer TA, conductors 32 and L, and a connection of L to the track rails (notl shown) which is similar to the connection of L through contact 3l and condenser AK for intermediate circuit B-C.

cuit 'and the other. P. is in, 0r arranged for connection in, circuit with the line conductors DI and D2. Transformer TE is shown connected permanently to the line conductors DI and D2. Transformer TC is shown for connection to line conductors DI and D2 by a selector operated relay SL closing contacts 46 and 41, the circuit including transformer coil P of TC, condenser CC, conductor 45, contact 41 closed', conductor 48, line conductors DI and D2 to and from the wayside station (already described), conductor 49, contact 46 closed', and conductor 44. The operation of selector relay SL will be'hereinafter interfere with the communication currents, a

condenser as TK is connected around each insulated joint to pass the communication currents around such insulated joint. Such an arrangement. while taking care of the alternating and pulsating currents for telephone purposes does not interfere with the proper Working of the direct current track circuit where used. Track circuits where used are generally of the usual well known sort with a relay at one end, such as TD, and a source of energy at the other such as a battery. Where alternating current track circuits are used treatment necessary is hereinafter referred to.

Since intra-train communication (between head end and rear end of same train) is an important feature of the invention, it is desirable to localize such communication within certain practicable limits, hence the stretch of track included in the train telephone installation is divided into sections or districts (already explained) of a length best suited to meet the existing requirements. The partial circuitconductor 33, contact 3|, conductor 30 and condensers AK-is normally common to the intermediate circuits for the two sections A and B-C; likewise there is a partial circuit through contact 4I common to intermediate circuits for the sections BC and D-E; etc. Since these partial circuit common connections are of relatively low resistance, and intendedly so, the intra-train communication current will be practically confined to the intermediate circuit or circuits the train is within. While a train is passing from one intermediate circuit to another, the limits of the intermediate circuit, or local communication zone, are extended to include the two intermediate circuits; e. g. a train when moving from the section for intermediate circuit B-C to the section for intermediate circuit D-E shunts -relay TD opening front contact 4| and closing back contact 4|, thus making the local zone circuit for the time being include track rails TR and condensers around insulated joints, condensers AK, conductor 30, front contact 3|, conductors 33, L and 42, back contact 4I closed, conductors 43 and L, and 52, transformer TE, conductor 53, front contact 5|, conductor 50 and condensers AE. This extended local zone will persist while relay TD is deenergized. When relay TD is deenergized, back contact 4| shunts transformer TC, temporarily, out of the circuit; but at the same time transformer TE .becomes available in the extended zone for wayside station connection. Hence but one transformer is connected in any intermediate circuit, or any communication circuit zone, at any one time; therefore, the impedance varies but little between an intermediate circuit and two intermediate circuits combined. This intermediate circuit arrangement is in \effect a communication zone traveling with the train, which for convenience may hereinafter be referred to as a traveling intermediate circuit.

Inter-train communication (communication between two or more trains) may be indulged in when two or more trains are in the same intermediate circuit or communication circuit zone extended. This feature is of value since information may be /echanged as to the operating of trains,'meeting and passing of trains, stopping of a following train in case the train head has to stop, etc.

The line conductor L may be composed oi two insulated wires 56 and 51 transposed with respect to each other, or arranged as a twisted pair, but connected together atlthe cross connection to the track, or at the transformer terminals, to form a complete circuit within themselves. Any inductive effect from adjacent line conductors in the circuit of these two wires 56 and 51 is generally confined within the local circuit formed by these two wires in the same manner as is the case in usual telephone practice where the main conductors are transposed at intervals. Thus it is seen how any inductive effect 'from foreign conductors is localized and prevented from reaching the track rails of the intermediate circuit.

Three different methods are shown for connecting the wayside communicating circuit conductors DI and D2, to the intermediate circuits. As illustrated in Figure 2 and heretofore referred to, a permanent connection is made to intermediate circuit of section D-E through transformer TE; a connection hereinbefore referred to under the control of the dispatcher, or wayside station, is shown for intermediate circuit of Section B-C through transformer TC;

and a connection made automatically by the passing of the train through section A, connecting transformer TA to conductors DI and D2, is shown for intermediate circuit of section A.

As to which of these styles of connections is the better to be used, or whether any two of them or all of them should be used in the same installation, depends upon conditions local to the stretch of railroad covered by the installation and the objects to be accomplished. In general, for communication between the dispatcher and trains, the dispatchers line should be free of intra and inter-train communications, except when the dispatcher establishes connection with trains through his selective system. Therefore, for railroad train operating service, the style of connection indicated at transformer TC should generally prevail. In certain locations Where it is desirable for the presence of a train to be reported, a permanent connection, as at transformer TE, or preferably an automatic temporary connection, as at transformer TA, may be installed to enable the train to report to the dispatcher w'ithout having to wait till the dispatcher establishes a connection by .aselector, as at transformer TC. Where it is desired that communication may be carried on freely between the passengers on trains and outside stations (commercial service) then the connection of service lines DI and D2 to the intermediate circuit shouldbe of either the type at transformer TA or transformer TE, the former being preferred because with this style of connection an intermediate circuit is connected to conductors DI and D2 only when a train is in the section for the circuit.

Already in service on many railroads are dispatchers telephone and selective systems, in which the dispatcher may have communication with a wayside station by operating a code key sending a certain code of impulses over the line to a selector in the station with which communication is desired, this selector, and no others,

responding to thecode transmitted to ring a bell to call the party desired to the phone. Such a system in general principle, as indicated by DSE, is used by a dispatcher in operating the combined selector and relay SL to connect transformer TC to the conductors DI and D2, and is well known in the art.

Relay TAR is normally energized. It is deenergized whenever there is a train in the section of track A and closes its back contacts 35 and 36 to connect transformer TA to the conductors DI and D2. Therefore, during the interval that the train is in intermediate section A, the train may freely communicate with the dispatcher or outside station, and vice versa. In an installation where the entire series of intermediate circuits are arranged for connection as is section A, a train passing through would always be connected to the wayside circuit for communication, yet only those intermediate circuits which are occupied by trains would be so connected at any one time.

In Figure 3, inductors |03 and |05 are attached to the caboose and |04 and |06 to the locomotive, all in a position to ride above `the track rails TR. While the inductors are illustrated in se-V ries connection, they also perform well in par-- allel connection. X and Y represent the transmitting and receiving sets for the caboose and locomotive respectively. W represents the wayside transmitting and receiving set connected to the primary P of transformer TR by conductors I0'I and |08.

The intermediate circuit for the communicating current comprises track rails TR, coils RCI connected across the track rails, condenser K2, conductor |20, secondary S of transformer TR, conductors LI, and |2I., condenser K2 and coils RC2.

The coils RCI and RC2 consist of turns of wire on an iron core connected in series with the track rails. The connection of the condensers, K2, to each coil is made to the center point of said turns. For the alternating signal current flowing in at one end of the coil toward the other end of the coil, the impedance is large; while for the communicating current owing in at both ends of the coil towards the center, the induction for one end of the coil neutralizes the induction for thev other end of the coil so that the impedance is practically only that ofthe resistance of the conductor in the coil.

The route of the block signaling alternating current in the rails TR at any instant is represented by the solid line arrows. The coils RCI and RC2 are inductive to the block signaling current but non-inductive to the communicating current, the route for which isv indicated by the broken arrows.

Where direct current is in the track rails, as for propulsion.purposes.its flow in the intermediate circuit will be stopped by the condensers K2. These condensers K2 may be located in the leads between the track rails and the coils RCI and RC2, instead'of whereshown.

Where alternating current -track circuits are used a series of intermediate circuits may be desirable, in which case the connection of the track rails with `the conductor vLI will take the general form indicated in Figure 2; i. e. this connection may be taken through the contact of a train governed track relay toV be severed and the transformers shunted while the train is passing from one track district or section to the next. Also, the wayside connection with the intermediate circuit may be of any one, any two or all of the severalv types illustrated in Figure 2. i

InFigure 4 the intermediate circuit, which is similar to those ci the general system illustrated in this application, comprises the track rails TR, condensers K4, conductor L2, wayside transmitting and receiving set WS, conductor L2 and condensers K4.

The wayside transmitting and receiving set WS is connected in the intermediate circuit in series. If there is more than one wayside set, the additional sets are preferably connected in parallel; '1. e. set WSI is connected in parallel with set WS by the conductors III and IIO.

Z represents a transmitting and receiving communicating set on a train in circuit with inductors |I5 and I-I6, which are located to ride above the track rails TR.

In Figure 5, BL is a bell or other audible or Visual alarm energized by battery BLB and controlled byY contact |09, operating when said contact |09 is closed. CR may be an ordinary relay, or it may be preferably a time relay of the type, which, after being energized, remains energized for a prescribed time interval holding contact |09 closed and leaving evidence of its operation. The switch C2, receiver R2 and conductor 9'I and 99 are the same as corresponding devices shown in Figure 2.

IriV Figure 6, TSI and TS2 are the adjoining endsfof two adjacent track circuits for block signaling operated by alternating current, the current flow at any instant being illustrated by the full line larrows. Conductors |22 and |23 for TSI and |24 and |25 for TS2 are connections from the track rails either to the source of alternating current or to the relays forthese track sections. l,

'I'he communicating current flow at any instant is indicated by the broken line arrows.

Coils |21 and |28 which connect across the rails TR, one in each section, are inductive to the alternating current for the track circuits but non inductive for the communicating current. Therefore, the communicating current may flow from the rails TR of section TS2, through coils |28, conductor |29 and coils I 21 to the rails TR of section TSI. Shouldit be desirable to begin an intermediate circuit at this point, it may be done by connecting cross con-ductor |26, leading from the line conductor such-as L of Figure 2, to conductor I 29.

Conductor |29 connects between the center points of the turns of coils |21 and |28. For the alternating signal current flowing from one track rail to the other for each track circuit section, the impedance of these coils is large; but for the communicating current iiowing in at the ends of these coils toward the center, the impedance is practically that of the resistance of the conductor in the turns, as the induction for the communicating current flowing in at one end of a coil is neutralized by the induction for the communicatingcurrent flowing in at the other end of the same coil.

A modified form of intermediate circuit is shown in Fig. 7, wherein a trackway conductor ||4 takes the place of the track rails TR and is insulated from the track rails and-the ground. 'I'his intermediate circuit comprises the trackway conductor H4, condenser K5, conductors |2 and L2, wayside transmitting and receiving set WSZ, conductors L2 and ||3, and condenser K5 nected to conductor H4. The trackway conductor I I4 is the transmitting and receiving medium of the intermediate circuit, instead of the track rails TR; and is preferably supported on the ties of the track and may be located between the track rails, or outside of the rails on the ends of the ties. Z represents a transmitting and receiving communicating set on the train in circuit via conductors ||8 and ||9 with inductor ||1, which is located to ride above the conductor ||4 and to be in inductive relation therewith.

In operating practice the switches S, C, M and Si, C| and MI of Figs. 1 and 2 should be operated in proper sequence; e. g. in calling the other end of the train or the wayside station, switch key S is closed and then released to send out the calling signal, which when received at the called station, as the-wayside station, operates device HI.v The wayside station acknowledges receiving the call by similarly closing and releasing switch key Sl causing the reply signal to be produced in device H. Switches C and C| are now closed connecting in the respective receivers R and Rl. Switches M and MI are now closed as required for the use of transmitters T and TI, respectively, in transmitting and communicating signals. When communication has ceased, switches C and CI are restored to normal position.

Assume a train operating in section A, Figure 1, and that the conductor desires to communicate with a wayside station, or the train dispatcher. By reason of the train being in section A, relay TAR is deenergized closing contacts 35 and 36 connecting dispatchers communicating circuit, conductors DI and D2, to transformer TA. In order to get the attention of the dispatcher, the conductor presses key switch S which energizes inductor IND. Inductor IND, when energized, induces electric current into the track rails TR and thus through the intermediate circuit for A (already described) into the transformer TA where the current is induced into the circuit of conductors DI and D2 containing transformer P2. From transformer P2 the electric energy is carried through the amplifying means to the signaling device HI, operating same. The .dispatcher or wayside station attendant, may then acknowledge the call by depressing key SI which will give a signal to the conductor by device H, as hereinafter explained. The dispatcher, or wayside station attendant, may then operate switch CI closing contact |02, close switch M| and inquire what is wanted through the transmitter TI. This transmitter sets up electric currents in the circuit including the conductors DI and D2 and transformer TA. The intermediate circuit A is energized by these currents from transformer TA so that the inductor IND is influenced from the track rails TR. The energy transmitted into inductor IND is delivered to transformer PI, and thence through the ampliers to receiver R, the conductor having operated switch C to close contact 23 after receiving the answering signal from the dispatcher. The conductor closes switch M and replies through transmitter T which energizes inductor IND. This energy is induced into the track rails TR and the intermediate circuit, through transformer TA into the wayside circuit conductors DI and D2, through transformer P2 to the amplifiers, and thence to the receiver RI where it is received by the dispatcher.

While the train is in track section A, it may be communicated with by the dispatcher, the pro-Y cedure in doing so being much the same as when the conductor calls the dispatcher. The dispatcher depresses the key SI closing contact 84 which connects the source of alternating or interrupted current energy GI to the conductors DI and D2 thus energizing the transformer TA through contacts 35 and 36, which are automatically closed because of the presence of the train in section A. In transformer TA current is induced into the intermediate circuit A containing the track rails TR which in turn inuence the inductor IND. The energy induced in the circuit of the inductor IND from the track rails is transmitted through the transformer PI and the amplifying means to signal I-I operating said signal. The conductor hearing the call may answer same by depressing the key S producing the operation of the signal HI as heretofore explained. The conductor then operates switch C, closing contact 23 and opening contact 22, as by putting receiver R to his ear, and, after closing switch M, proceeds to inquire through transmitter T what is wanted. 'I'he dispatcher having heard the signal HI replying to his call, closes the switch CI, receives the inquiry as to what is wanted and, after closing switch MI, gives his communication through the transmitter TI and the receiver R to the conductor.

Assume the train is passing from the section including subsection A through subsection B into subsection C. Relay TB is deenergized to close its back contact 3| and connect together conductors L of the section associated with subsection A and the section B-C. This results in the joining together of the intermediate circuits for these two sections into one combined or enlarged intermediate circuit which persists while the train is in subsection B. Since each of these intermediate circuits has been heretofore described, the makeup of the combined, or enlarged, intermediate circuit is readily understood as a combination of the two (A and B-C) with the cross connection through front contact 3| broken. During the interval this enlarged or combined intermediate circuit exists, communication signal currents originating on the train and intended for the dispatcher or wayside station, pass inductively from the train inductors IND into the enlarged intermediate circuit by way of the track rails TR and the condensers TK at the insulated joints, causing a corresponding current in said enlarged circuit. As transformer TA is shunted while back contact 3| is closed, the communication signal currents for the dispatcher or wayside station, pass thru the secondary S of transformer TC and are induced into the primary P of this transformer, since the dispatcher must have operated his selective system for selector relay SL to connect transformer TC with conduc- 'andere 7 tors D and D2, as hereinafter described for connecting up with a train in subsection C. Primary coil P of transformer TC being in circuit with the conductors DIY and D2 and transformer P2, the communicating signal currents are received in the amplifier circuit of which P2 is a part and passed to the receiving device H| or RI, as the case may be, in the dispatchers oice. The dispatcher in communicating with the train passing through the subsection B, sends communicating signal currents, as already described, into the circuit including conductors D| and D2, and the primary P of transformer TC. In transformer TC these communicating signal currents are induced into` the combined intermediate circuit (A and B-C) including the track rails TR from which they are induced into the train carried inductors IND and taken through the train carried amplier and receiver circuits to the receiver H or R, as the case may be, on each end of the train.

As heretofore stated the signal responsive means H and H| or either of them may be relays, or loud speakers in which latter case the receivers R and RI will be a convenience though they may not be strictly necessary. It is considered good practice to provide signals through H, in particular, of a character that they may be heard by the conductor and engineman above the noise of the train and by them if they are outside the train. Further, it is desirable that the signal responsive means H be of such type that it leaves visual or audible evidence of having been operated. In case the communication signals are distorted or a change in volume of the reception is desired, the adjustable condensers, N on the train and N| in the wayside station, may be operated to change the character of the received signals.

Where the means of communication is by voice it is well to answer a call by a like signal before listening in, and thus avoid the unpleasantness of the signaling noise in the telephone receiver. Before sending a signal call over the line, it will be good practice to iirst listen in to see if the line is already busy; this is particularly true in calling from the train to the wayside station, or in calling from the wayside station to the train if there are apt to be two or more train sets in the intermediate circuit. In the case of a train dispatcher, it is doubtful that any signal call to the dispatcher previous to starting conversation is necessary, since the dispatcher is generally always on the` circuit with his receiver.

In the event it is desirable to distinguish in calls between the head end and rear end of a train or,

between trains, considering there may be at times more than one train in an intermediate circuit, a system of coded signals may be used, a prescribed call being assigned to each train head end and rear end.

The devices H on the trains may comprise a selector responsive only to a code of impulses sent out from the wayside station. In the case of train dispatching service the selective system for telephoning may be made to operate selectors on the trains so that any particular train station may be called without disturbing any other train station. The reverse may be arranged where it is desirable to call a particular wayside station from a train. The transmission of the code impulses to operate the selector device requires only that the switch keys S and S| be replaced with a set of code keys and the selectors be appropriately arranged as a part of the devices H and HI.

Assume a train operating in any of the subsections, as C and that communication between the conductor and the engineman is desired. The party initiating the conversation, as the conductor, presses switch key S energizing the inductor IND on the rear of the train with signaling current, which in turn inuences the rails TR to cause electric energy to ow in the intermediate circuit including the track rails TR, condensers AK, conductor 30, contact 3 I, conductor L, transformer TC, conductor 43, contact 4|, conductor 40 and condensers AC. Since the inductor IND at the head of the train rides over the track rails TR,'it is inuenced by the current in the intermediate circuit so that the circuit of inductor IND at the head of the train is energized including transformer P| in the set on the head of the train. The transformer PI transmits the energy to the amplifying means and thus it is carried to the signal H at the head of the train as a straight sig nal or code of signals. The engineman hearing the call, may then enquire what is wanted by communicating directly through the transmitter T of his set, or by first signaling back in a manner similarly to the procedure of the conductor. The steps and procedure in communication are now similar to those described between conductor and dispatcher, except no wayside selective or telephone circuit (conductors DI and D2) is concerned.

Figure 3 shows in schematic form the arrangement of apparatus for rear end to head end communication and vice versa using two inductors for each set. When X transmits, inductors |03 and |05 are energized inducing communication current into the track rails TR, which are a part of the intermediate circuit, coils RCI, condenser K2, conductor |20, transformer TR, conductors L| and |2|, condenser K2, and coils RC2. Inductors |04 and |06 receive the energy from the track rails and same is transmitted to set Y for reception therein. The operation is similar where Y transmits, but now |04 and |06 are transmitting inductors and,v |03 and |05 receiving inductors As shown in Figure 1 there is but one inductor, but two inductors as in Figure 3 give a stronger sending and receiving influence.

Assume communication is desirable between the two ends of a train While the train occupies subsection B, and that the conductor on the rear of the train or caboose initiates the communication. He transmits communicating signal currents into the inductor IND on the caboose. These are induced from the inductor into the track rails TR which form apart of the combined or enlarged intermediate circuit for sections A and B-C a1- ready described. Since the inductor IND, on the head end of the train or locomotive, is in communicative relation with the track rails TR of the same combined or enlarged intermediate circuit, the communicating signal currents are induced into the circuit of the locomotive carried inductor IND and thence taken through the locomotive carried amplifier and receiver circuits to the receiver H or R, depending whether communicating is by code signal or by voice. Should the engineman reply or initiate the communication, the procedure on his part and the cycle of operation is similar to that just described.

For communication between sets at the ends of a train or between trains in the same intermediate circuit, the transformer for such intermediate circuits, as TC of intermediate circuit for section B-C, performs no useful purpose. This transformer serves only to connect the intermediate circuit with wayside stations.

Assume that the dispatcher desires to communicate with the train in subsection C of intermediate circuit for section B-C. He operates a code key, which is a part of the selective apparatus DSE in his ofiice, and a certain code of electric impulses is sent over the conductors DI and D2, with which selector relay SL is in circuit, and to which the selector relay SL is responsive. The selector relay operates to connect the transformer TC with the conductors DI and D2 by closing the contacts 46 and 41. Communication may now be carried on between the train and the dispatcher as heretofore described.

Since the rear and head ends of a train are always in the same intermediate circuit, or the same circuit extended, the dispatcher may communicate with either end or both ends of the train; or al1 three may communicate together at the same time.

While the train is proceeding from one section to another, as from section B-C to section D-E, relay TD is deenergized closing back contact 4l and opening front contact 4|. Intermediate circuit for section B-C is now extended; or in effect intermediate circuits for sections B-C and D-E are combined for the interval the train occupies track section D. As back contact 4| shunts transformer TC, the dispatchers communication with the train will now have to be carried through transformer TE, which in this case is in constant connection with the intermediate circuit.

When `communication is completed the dispatcher may disconnect conductors DI and D2 from transformer TC by again operating the selector SL. Communication between rear end and head end may be maintained through the combined intermediate circuits for sections B-C and D-E in the same general manner as described for subsection C of the intermediate circuit for section B-C and that shown in Figure 3. When passing from one intermediate circuit to another the common connection there between is automatically severed and the transformer for wayside connection is shunted so that no interruption in intra-train communication occurs; nor is the quality of the communication affected since the impedance of the circuit is but slightly changed.

If the wayside communication with a train is to be of considerable length, connection should be made of the wayside circuit with several intermediate circuits in order to avoid interruption.

Where two or more trains are in the same intermediate circuit or in an intermediate circuit extended, communication may be carried on between them in a manner similar to that procedure explained for rear end to head end communication. This is clearly indicated in Figure 3, by considering that set X and equipment belongs to one train and set Y to another train.

While I have described this system mainly as a telephone system of communication, I do not wish its use to be so confined. A means for transmitting signals between wayside and train, between the two ends of a train, and between two trains has already been described. It is readily evident these signals may be put in code, as the Morse code, and communication carried on in that manner. It has also been pointed out how devices H and HI may be operated as relays. Such operation may be made use of in carrying on communication by the printing telegraph, as for controlling the Teletype, a Well known Asystem of printing telegraph which is now much used commercially.

I have shown the intermediate circuit includandere ing the track rails, which is the preferred form, but I do not wish to be confined to such use alone as I may .use an independent trackway conductor, as indicated by II4 in Figure 7, and may locate same in the center of the track.

I claim as my invention:

1. Means for carrying on communication between a railway train and a'wayside station comprising, a track system having a series of track districts, a track, circuit section in each district, a conductor connected to the ends of each district to form therein an intermediate circuit including the track rails of said district and said conductor, a transformer connected in each of said intermediate circuits for connection to a wayside circuit, a relay controlled by each of said track circuit sections, and a circuit controlling contact operated by each of said relays so arranged that, while a train occupies the track circuit section of any track district. the connection of the conductor at the end of that track district is broken, the transformer is shunted from the intermediate circuit of the adjoining track district and the intermediate circuits for the two adjacent track districts are thrown together forming an extended or enlarged intermediate circuit.

2. Means for carrying on communication between a railway train and a wayside station comprising, a track system having a series of track districts, parallel electric conductors continuous throughout the length of the system connected together at the ends of each district by cross conductors, said parallelconductors when so con.

nected forming an intermediate circuit for each district, a transformer associated with a wayside circuit connected in each intermediate circuit, and train operated means within each track district for opening a cross conductor section of the intermediate circuit for that district and shunting the transformer from the intermediate circuit of the adjoining district.

3. Means for carrying on communication between a railway train and a wayside station comprising, a track systemhaving a series of track districts, parallel electric conductors continuous throughout the length of the system connected together at the ends of each district by cross conductors, said parallel conductors when sorconnected forming an intermediate circuit for each district, a transformer associated with a wayside circuit connected in each intermediate circuit, and means operated by the train, in passing from one track district to another, for opening said cross conductor section of the circuit, shunting said transformer from one intermediate circuit and combining the intermediate circuits for the two adjacent districts into one extended or enlarged intermediate circuit.

4. In a system adapted for communication between a moving railway train and a wayside station, the combination comprising transmitting and receiving circuits on the train, a series of intermediate circuits on the trackway each in inductive relation with said train circuits as the train progresses over the railroad, transmitting and receiving circuits on the wayside, and devices connecting., said wayside circuits with said intermediate circuits, some of said devices being in permanent connection, others being connected only by the presence of a train on the track, and still others being connected selectively from the wayside station. Y

5. In a system for carrying on communication between the-two ends of a railway train or a railway :train and a wayside station, a series of intermediate circuits in they track system each comprising the rails in a'stretch of track, a conductor insulated from said track rails extending along said stretch of track, cross conductors connecting said conductor with said track rails at the ends of the track stretch, induction coils in said cross conductors inductive to the ow of alternating signaling current from the track rails to said conductor but non-inductive to the ow oi communication current to said conductor, a train traveling in the track system, and an electrical circuit on said train electrically coupled with the track rails for transmitting communieating current into saidY rails toY ow therein in parallel.

6. In a system of train communication, a stretch of track for trains, a series of sections in said stretch each with an intermediate communication circuit therefor, a rst train in one of said sections, a second train in another of said sections, transmitting and receiving communieating circuits including amplifying means on each end of each of said trains in exclusive communicative relationship with the intermediate circuit for the section occupied by the respective train to eect communication between the ends being operative for carrying on communication between the ends of said second train simultaneously with the communication being carried on between the wayside station 'and said rst train.

7. In a system for communication between the front end and rear end of a train, the combination comprising, a stretch of track for the train,

a transmitting and receiving communicating set on each end of the train, en inductor in circuit with each of said sets, a series of intermediate circuits, each associated with a different section oi' said track and adapted to be in electrical relation with said inductors as the train moves over the railroad, means associated with the intermediate circuits yof adjacent sections of said track and operated by the train for conductively uniting the intermediate circuits of said adjacent sections for the interval that the train occupies both of said sections, and means in the communicating sets amplifying the communication impulses transmitted between said train ends.

8. Ina system for communication between a railway train and a wayside station, in combination, a communication zone traveling with the train comprising, a rst intermediate circuit including a transformer therein adapted to be connected to said wayside station, a second intermediate circuit including a transformer therein adapted to be connected to said wayside station, devices in said second circuit connecting said rst circuit with said second circuit and eliminating said iirst circuit transformer from the intermediate circuits as connected while the train is passing from the location of the first circuit to the location of the second circuit and restoring said rst circuit including the transformer therein to location of said first circuit, andneansln the wayside station including receiving apparatus in electrical relation with said intermediate circuits for amplifying the communication impulses received therein through the circuits for said communication zone.

9. In a system for communicating between a y'wayside station and a railway train and between the two ends of a railway train on a stretch of.

track, an intermediate circuit comprising the two rails of said stretch, said track rails at each end connecting .to a condenser and a cross conductor connecting between said condensers, a wayside conductor along said stretch, and means including a circuit switch adapted to be closed in either of two positionsconnecting said conductor .to said cross conductor.

10. In a system for c-ommunicatingbetweex the front end and rear end of a railway train and/o' between said train :and a wayside station, a single winding inductor coil mounted on a train and adapted for inductively transmitting or receiving communicating current, a transmitting and receiving means on each end of the train comprising a transmitting circuit and a receiving circuit, said transmitting circuit including a cert-ain number of turns of the winding of said inductor coil and said receiving circuit including a certain other number of turns of the winding of said inductor coil.

11. In a system Iadapted for communication between the two end-s of a railway train and/or between the railway train and a wayside station, in combination, a normally inactive transmitting set and a normally active receiving set on each train end and in the wayside station, a communication zone traveling with the train, said zone always` comprising an electrically complete conductive intermediate circuit with which said train end sets are in continuous communicative relation, and electrical means associated with said intermediate circuit adapted to be operated to 12. In a system for communicating between a' vehicle operating in a track district and a wayside station, communication apparatus on the vehicle including a transmitter, a receiver, an amplifier for communication signals, and a resonant circuit, said receiver and said amplier being normally in said circuit and said circuit being arranged to abnormally include said transmitter, a wayside station communication apparatus in-l cluding transmitting and receiving means, a series of wayside mediums for conveying communication impulses each adapted to be in communicative relation with said vehicle communication apparatus, and means for communicatively connecting the wayside communication apparatus with any one or several of said mediums, some of said means being controlled from the wayside station and other of said means being controlled by the vehicle.

13. In a system for carrying on communication between the two ends of a railway train and/or between the railway train and a wayside station, a series of intermediate communication circuits in an alternating current signaled track system each comprising the rails in a stretch of track, a conductor insulated from said track rails extending along said stretch, cross conductors connecting said conductor with said track rails at the ends of the track stretch, induction coils in said cross conductors inductive to the flow of alternating signal current from the track rails to said conductor but non-inductive to the ow of communication current in said conductor, and

means in said cross conductors adaptable to unite adjacent circuits of said series.

v14. In a system for carrying on communication between the two nds of a railway 'train :nd/or.

between the railway train and a wayside station, an intermediate circuit for "an alternating current signaled track system comprising, the rails rent from the track rails to said conductor but non-inductive to the ow of communication current in said conductor, and means forming a part of said circuit adapted to connect said circuit with the wayside station. l

15. In a system for communication between a wayside station and railway trains in a stretch of track, apparatus including an amplifier on each train and in said wayside station for transmitting and receiving communication signals, each such apparatus provided with a normally inactive transmitter and a normally active receiver and the amplifier being in circuit with the receiver, a wayside circuit operatively associated with the apparatus for each train within which communication signals from and to said train are conned, and means associated with the electrical means for each train and the apparatus for said station for optionally placing the transmitting and receiving apparatus of said station in communicative relation with the transmitting and receiving apparatus of any one, or more than one, of said trains, said arrangement making possible a communication from said station to one of several trains at one time.

16. In an inductive train telephone system, a stretch of track including the two running rails for a train, a communication circuit associated with the stretch of track and electrically closed with the stretch of track either occupied by a train or unoccupied, said communication circuit comprising the two running rails in parallel and a common return path, operative with a train facing in either direction and running either forward or backward, and adapted to travel with a train moving over the stretch of track by additions to the circuit ahead of the train and subtractions from the circuit behind the train,.said additions and subtractions being dependent upon the movement of the train, inductors, each including a, winding, located at dierent points on said train in such manner that, with a train present on said running rails, the inductors are disposed adjacent to and separated by an air gap from the running rails and, together wit 'the rails, constitute electrical transformers of which the windings of the inductors serve as primary windings and the railsv as secondary windings, train carried telephone transmitting sets at said train points, manually controlled means for connecting said sets in circuit with the inductor windings to inductively n transmit modulated current into said running rails, said current iiowing in the two running rails comprised in the communication circuit in the same direction at any instant so that the current transmitted from one train point is received upon the train at a dierent point, train carried telephone receiving sets at said train points normally connected in circuit with said inductor windings to inductively receive current from said rails, a wayside circuit, means operative to inductively connect said wayside circuit with the communication circuit whether or not a train is on said running rails, a telephone receiving set at a wayside station normally connected to the wayside circuit, a telephone transmitting set at said Wayside station, and manually controlled means for connecting said transmitting set in circuit with the wayside circuit.

17. A trackway system of circuits for interconnecting' telephone sets at diiierent points on moving trains comprising, the two rails of a stretch of track, a series of conductors along said stretch, circuit connections from each end of each conductor to both of the track rail-s, and switching contacts for opening the circuit connections of adjoining ends of adjacent conductors and for connecting said adjoining ends together.

18. A trackway system of circuits for interconnecting telephone sets at different pointson moving trains comprising, the two rails o-f a stretch v of track, pairs of condensers bridged across the track rails at separated points, a series of conductors along said stretch, circuit connections each including a contact element connecting adpoining ends of adjacent ones of said conductors to the midpoints oi?I the condenser bridges, and means including the contact elements for opening said circuit connections and for connecting said adjoining conductor ends together.

19. A trackway system of circuits for interconnecting telephone sets located on moving trains comprising, the two rails of the track on which the trains run, a series of conductors each connected withvthe next adjacent conductor through a winding of a transformer, and circuit connections oetween the conductors and the track rails -so placedl as to form a plurality of loop circuits each of which includes a section of the track rails, one of said conductors and one of said transformer windings.

20. In -a train telephone system, a stretch of track,a train moving along the track, a telephone set at one end of the train in direct inductive relation with .both rails of the track, a telephone set on the other end of the train in direct inductive relation with both rails of the track, a series of train controlled relays at spaced intervals along the track, and a variable circuit for transmitting energy between said two train telephone sets comprising, alternately, the two track rails from a point substantially 'ahead of the train to a point substantially in the rear of the train and a return path including contacts of only two of said relays, and the two track rails from a point substantiallyv ahead of the train to a point substantially in the rear of the train and a return path including contacts of -said two relays and acontact of a third relay.

21. In a train telephone system, a section of railroad track, a wayside line, a two-winding transformer, circuit connections connecting one transformer winding across said line, a loop circuit including the other winding of said transformerassociated with the track section, and train controlled means associated with-the track section for short circuiting said other transformer winding to reduce the impedance of said loop circuit.

22. In a railway telephone system, a stretch of railway divided into blocks, a first section and a -providing an exclusive connection between'the telephone stations of the train in the block, and means associated with the second section of one of said blocks and responsive to a train occupying said section for transforming said two individual loop circuits into one single loop circuit' providing a connection between the telephone stations of both of said trains.

23. In a railway telephone system, a stretch of track divided into blocks, a ilrst section and a second section wholly within each block, a train occupying the iirst section of one of said blocks, telephone stations at different points on said train, an individual loop circuit for said occupied block providing an exclusive connection between the telephone stations of said train, an adjoining block, an individual loop circuit for said adjoining block, a telephone station associated with said adjoining block in communicative relation with the loop circuit for that block, and means associated with the second section of the occupied block and responsive to a train occupying said second section to transform said two individual loop circuits into one single loop circuit providing a connection between the telephone station associated with the adjoining block and the telephone stations on said train.

24. A trackway system for conveying'signals to and from moving vehicles comprising a series of closed loop circuits associated with a stretch of track for the vehicles, means `for inductively connecting adjacent loop circuits under certain conditions, and means for joining said adjacent loop circuits to form a single loop circuit under other conditions.

25. A trackway system for conveying electrical impulses to and from vehicles comprising a series of closed loop circuits associated with a stretch of track for the vehicles, remotely controlled means for inductively connecting adjacent loop circuits, and vehicle controlled means for joining said adjacent loop circuits to form a single loop circuit.

26. In a system adapted for communication between the front end and rear end of a train, the combination of a stretch of track for the train, normally inactive transmitting apparatus and normally active receiving apparatus including a resonant receiving circuit for each end of the train, and an intermediate circuit in said stretch changing in location in the stretch as the position of said train changes by additions to the intermediate circuit ahead of the train and subtraction from the intermediate circuit behind the train, said intermediate circuit being in continuous electrical. relation with the apparatus on each end of the train as the train travels through the stretch.

27. In a system for communication between a wayside station and railway trains in a stretch of track, apparatus on each train and at said wayside station adapted to transmit and receive communication signals, said wayside station apparatus including an amplier of communication signals, a transmitter, a receiver, and a circuit arranged to normally include said ampliiier and said receiver and optionally to include said transmitter, wayside' means in electrical relation with the apparatus on each train and the apparatus at the wayside station for conveying said communication signals between said wayside station and said trains, and devices operatively associated with said wayside means and controlled from said station for optionally placing said station in communicative relation with any one, any several, or all of said trains.

28. In a system of the class described, a plurality of sections in a stretch of track, an intermediate circuit 'for each section, a single normally active transformer in each intermediate circuit, and means located vadjacent the ends of' the sections of said stretch operative to connect adjacent intermediate circuits together and to render the transformer for one of said circuits inactive duringthe interval a train is passing from one section to another.

29. In a system for communication between a wayside station and a plurality of trains in a stretch of railway track, a calling system comprising apparatus on each train including a relay responsive only to a coded electric current signal prescribed for said train, an intermediate circuit for said stretch including the track rails in multiple, said circuit being' in electrical relation with the apparatus on each train, a wayside station, conductors associated with said intermediate circuit and leading to said wayside station, means also associated with said intermediate circuit for at times connecting said conductors in electrical relation with said intermediate circuit, and apparatus at said wayside station adapted to be electrically connected to said conductors for sending to each of said trains the electric current signal to which the relay on the train is responsive.

30. In a communication system, a railway track divided into signal sections by block joints of wayside signal equipment, high frequency bypasses around said block joints, a conductor in the vicinity of said track, a low impedance bus circuit connecting each said track section to said conductor, and means for automatically and temporarily opening each bus circuitI as a train enters the section associated therewith and closing said circuit as the train leaves said section.

3l. An apparatus according to claim 30 characterized further by the fact that said means for automatically opening and closing said bus circuits are relays connected to the rails of said track sections.

32. In a system for communicating between a railway train carried station and a wayside station, the combination comprising, a stretch of track including the rails for the train to run on, transmitting and receiving sets including circuits connected therewith for the station carried on the train, means associated with these circuits for bringing them into a state of resonance for the communication currents transmitted from and received on the train, a conductor electrically coupled with said train carried circuits and located on said track near to but insulated from said rails, transmitting and receiving sets including circuits connected therewith at the wayside station, and electrical circuit means including a circuit closing device, closed only while the train is in said stretch of track, for connecting said conductor in circuit with the transmitting and receiving circuits at said wayside station.

33. In a system adapted for communication between a railway train station and a wayside station, the combination comprising, a stretch of track including the rails for the train to run on, a track circuit in said stretch including said rails and a relay for controlling the opening and closing of circuit contacts, electrical transmitting and receiving communication apparatus in said train carried station, circuits connecting said train station apparatus with an inductor also carried on said train, means associated with said train carried circuits forv bringing said circuits *nto a state of resonance for the transmitten and received communication currents, a conductor in electrical relation through an air gap with said inductor and located on said track near to but insulated from said rails, electrical transmitting and receiving communication apparatus at said wayside station, a wayside communication line connected with said wayside station communication apparatus. and electrical circuit means including said relay contacts, closed only while the train is within said track circuit, for connecting said conductor in circuit with said wayside communication line that two way communication may be carried on between the train station and the wayside station.

34. In a system for carrying on telephone communication between a wayside station and a station on a railway train, the combination comprising. a stretch of track having dened limits, a circuit including a line conductor as one 4side of the circuit and a track conductor as tl'ie` other side of the circuit, said track conductor mounted on the ties adjacent the track rails but insulated therefrom and terminated at substantially the limits of said stretch of track, a train carried inductor mounted on the train in relatively close proximity to said track conductor for close inductive coupling therewith, a telephone set for said train station coupled with said inductor, and a telephone set for said wayside station coupled with said line conductor.

35. In a system for carrying on communication between a wayside station and a station on a railway train, the combination comprising, a stretch of track having deiined limits, a circuit including a line conductor as one side of the circuit and a conductor on the track as the other side of the circuit, said track conductor being mounted on the ties adjacent the track rails but well insulated frornsaid rails and the ground and terminated at substantially the Llimits of saidY stretch of track, a train carried inductor mounted on the train in relatively close proximity to said track conductor for close' inductive coupling therewith, a communication Set for said train station electrically coupled with said inductor, and a communication set for said wayside station electrically coupled with said line conductor.

l 36. A system for carrying on twowway communication between a railway train carried station and a wayside station, comprising, a track system having a series of track districts, ailrst conductor close to the 'track throughout the length of each district, s'aid nrst conductor being on the roadbed for and adjacent to the rails of said track butinsulated `from said rails, an additional conductor throughout the lengthoi each district connected to said tlrst conductor at one end of said district, electrical transmitting and receiving communication apparatus includiug a circuit therefor at the train carried station, said circuit being so positioned as to be electrically coupled with said first conductor, electrical transmitting and receiving communication apparatus Yat said wayside station, a wayside communication circuit connected with the apparatus at said wayside station and extending along said track system. and electrical circuit means for each district including a circuit closing device, closed only while a train is on the track in said district, for connecting said iirst conductor and said additional conductor at the other end of said district in circuit with said wayside communication circuit, the arrangement being such that two way communication may becarried on between the wayside station and the train in any district while the train occupies that district.

ARCHIBALD G. SHAVER.

CERTIFICATE oF CORRECTION.

Patent No. 2,2}.|.O,6"(`6. Hay 6, 1914.1.

ARCRIBALD`G. SHAVER. p

It is hereby certified that error appears in the printed specificatio of the above numbered patent requiring correctionsm follows: Pageb, second column, line 22, for the word "head.read --ahead-g page 10, first column, lines 55,56, and57,claiml5,forthewords "and means associated with the electrical means for each train and the' apparatus for" read-.--and a selector operatively Aassoci ated with each ofsaid circuits and controlled from-w; line 11.5, same claim, for "of" read or; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

signed and sealed this 29th day of July, A. D. 19h1.

Henry Van Arsdale,

(Seal) Acting Commissioner of Patents.

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