US2064640A - Railway communicating system - Google Patents

Description

1936' P. N. BOSSART RAILWAY COMMUNICATING SYSTEM Filed Nov. 4, 1933 2 Sheets-Sheet 1 b g lPau! BY Dec. 15, 1936.

P. N. BOSSART RAILWAY COMMUNICATING SYSTEM Filed Nov. 4, 1933 i 2 Sheets-Sheet 2 115 112 W: To Stazz'on Equqbmezyz. g. T? 1152 [14:1-

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2a 2% 125 ll E INVENTOR Paul 1V. Bossam BY CLXW H115 ATTORNEY Patented Dec. 15, 193 6 UNETED STATES PATENT GFFICE 2,064,640 I RAILWAY COMMUNICATING SYSTEM Application November 4, 1933, Serial No. 696,663

28 Claims.

My invention relates to communicating systems for railways, and particularly to systems for telephone communication between a wayside station and a train.

A feature of my present invention is the provision, in systems of this type, of apparatus for permitting communication between a Wayside station and a train occupying any one of several tracks. Other features and advantages of my invention will appear as the specification progresses.

I will describe several forms of apparatus embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Fig. l is a diagrammatic view of one form of apparatus embodying my invention wherewith telephone communication is provided between a wayside station and a train occupying any one of four different railway tracks. Figs. 2, 3 and 4 are diagrammatic views of modified forms of apparatus for coupling the wayside station equipment with the trafiic rails, and which apparatus also embodies my invention. Fig. 5 is a diagrammatic view of a modified form of a transformer for coupling the wayside station equip- ,ment with a line wire. In each of the several views, like reference characters designate similar parts.

Communicating systems have been proposed for telephoning between a wayside station and a railway train, or between two trains, or between two separate locations on the same train by transmitting from one location to the other a carrier frequency current modulated with voice frequencies, the communicating channel preferably including the traiiic rails in the manner disclosed and claimed in the United States application for Letters Patent Serial No. 450,135, filed May 6, 1930, by L. O. Grondahl, for Electric signaling systems. In my present invention, energy is transferred between the traffic rails and the train carried equipment through the medium of inductor coils mounted on the train, and is transferred between the wayside station equipment and the trafiic rails through the medium of track communication transformers connected across insulated rail joints. I have found that a line wire, such as commonly employed in telegraph work, paralleling the railway tracks may be employed in transmitting the carrier current between the two spaced locations. That is, a line Wire by virtue of its distributed mutual electromagnetic induction to the traflic rails and by virtue of the distributed capacities between the line and ground and between the line and the traffic rails will serve as an additional communicating channel. I propose to utilize at times such an additional channel by transferring energy between the wayside station equipment and a line wire through the medium of a transformer coupled directly with the line wire. As will appear hereinafter, the line wire may be utilized as a communicating channel separate and independent from the channel through the traiiic rails alone if it seems desirable to do so.

In systems of the type here involved, the receiving apparatus at each location is normally active and coupled with the communicating channel in order that either location may call the other at any time. The receiving apparatus preferably includes a call selecting circuit responsive to a distinctive frequency only, whereby the receiving apparatus will not respond unless a call intended for that particular location has first been received. The transmitting apparatus of each location is coupled with the communicating channel only during the periods of sending a calling current or a telephone current. With such an arrangement, the telephone receiving device will be automatically switched into the circuit ready to reproduce a telephone message, and stray noises and unwanted conversations will be avoided.

Referring to Fig. l, the reference characters W, X, Y and Z designate four difierent railway tracks, the traflic rails of each of which are designated by the reference characters H and. ii A train indicated schematically at V occupies the track Z, although it will be understood that it may equally as well occupy any one of the other tracks W, X or Y. Mounted on the train V is telephone equipment indicated as a whole by the reference character TE. At the right-hand end of Fig. 1, a wayside station S is provided with telephone equipment indicated as a whole by the reference character SE. Each of these two equipments TE and SE will be fully described as the specification progresses.

i and 5 are inductor coils located on the train V in inductive relation with the traffic rails II and H respectively. By means of these inductor coils 4 and 5 energy is transmitted to and received from the trafiic rails by the train carried equipment TE, the coils 4 and 5 being selectively connected with either a transmitting circuit or with a receiving circuit as will shortly appear. Track communcation transformers TW, TX, and TZ are adapted to transmit energy -matically, a circuit controlling contact operatively connected with the handle I 4 and to or receive energy from the traffic rails of the railway tracks W, X, Y and Z, respectively. That is, these track communication transformers are selectively connected with either the transmitting circuit or with the receiving circuit of the wayside station equipment as will appear when the wayside station equipment is described. It follows, that the train V may occupy any one of the four tracks W, X, Y or Z and the traffic rails of the track occupied will serve as a communicating channel between the wayside station equipment SE and the train carried equipment TE permitting thereby communication between the wayside station S and the train V within a radius of several miles.

Referring now to the train carried equipment TE, a microphone M is provided with an operating handle I4 which is adapted to be manually operated to any one of three positions as indicated by the dotted lines in Fig. 1. These three positions I shall refer toin the following descriptions as normal position, calling position,

and communicating position. As shown sche- I2 is is moved to three positions identified by the numerals I, 2 and 3 in response to the handle I4 being moved to the normal, communicating and calling positions, respectively. Mounted on the handle I4 is a common spring return push button [3, which, as shown schematically, is operatively connected with a circuit controlling contact I5. Contact I5 is normally open and is forced down into engagement with a contact IG by the depressing of the push button I3. A calling relay CR and a directional relay DR are associated with the handle I4, the arrangement being such that when the handle I4 occupies its normal position, both relays CR and DR are deenergized. With the handle I4 moved to the calling position and contact I2 moved to its No. 3 position, current will flow from the B terminal of any convenient source of current such as a battery not shown over contact I2, winding of relay CR, Winding of relay DR to the opposite terminal C of the current source, and the two relays CR and DR will be energized in series. With the handle I4 operated to the communicating position and the push button I3 depressed, current will flow from the B terminal of the current source over contact I5-I6, contact I2, winding of relay DR to the opposite terminal C of the current source and relay DR will be energized. It follows, that normally both relays CR and DR are deenergized, the two relays are energized in series when the handle I4 is operated to the calling position and the relay CR is down and the relay DR is picked up or is down accordingly as the push button is depressed or released when the handle I4 is operated to the communicating position.

The train carried equipment includes a transmitter designated by the reference character TR. This transmitter TR may take different forms and preferably is of the form disclosed in a copending application for Letters Patent, Serial No. 658,932, filed February 28, 1933, by Leland D. Whitelock et al., for Communicating systems, and to which application reference is made for a full understanding of this transmitter. This transmitter forms no part of my present invention and is shown conventionally only in order to not unduly complicate the drawings. It is deemed sufiicient for the present description to point out that the transmitter TR includes a generator of carrier frequency current which is modulated with voice frequencies by speaking into the microphone M. With the calling relay CR deenergized, and its back contact I'I closed, the microphone M is connected to the input of the transmitter TR over the wires I8 and I9. When the calling relay CR is picked up, the micro phone is disconnected from the transmitter TR and a circuit is completed at the front contact 20 which causes the carrier current to be modulated at a given single frequency within the voice frequency range say, for example, at 700 cycles per second. Hence, there is supplied to the output of transmitter TR a carrier telephone current or a carrier calling current at the discretion of the train operator. Furthermore, as fully described in the above mentioned copending application, Serial No. 658,932, the carrier and one side band may be suppressed leaving only the remaining side band to be supplied to the output circuit of the transmitter TR. The inductor coils 4 and 5 are connected with the output of the transmitter TR over a circuit which can be traced from the upper terminal of the inductor coil 4 along wire 2I, output of transmitter TR, wire 22, from contact 23 of the directional relay DR when that relay is energized, and wire 24 to the lower terminal of the inductor coil 5, the two coils 4 and 5 being connected in series. coils 4 and 5 are connected with the output of the transmitter TR only at such times as the directional relay DR is picked up, and when so connected are effective to supply the output of the transmitter TR to the two trafiic rails I I and I I in parallel.

The train carried equipment TE also includes a receiver AR which is adapted to receive and demodulate a modulated carrier current. The receiver AR may take any one of several forms and preferably is of the form described in the aforementioned application, Serial No. 658,932. This receiver AR forms no part of my present invention and is shown conventionally only for the sake of simplicity. The inductor coils 4 and 5 are normally connected with the input of the receiver AR, the circuit being traced from the upper terminal of the inductor coil 4 over wires 2I and 25, input of receiver AR, wire 26, back contact 21 of the directional relay DR and wire 24 to the bottom terminal of the inductor coil 5. It is clear from the foregoing that the inductor coils 4 and 5 are connected with the input of the receiver AR as long as the microphone handle I4 occupies its normal position, and also when handle I4 occupies the communicating position and the push button I3 is released. That is, when the handle I 4 is moved tothe communicating position the push button I3 serves as a medium for transferring the inductor coils 4 and 5 between the transmitter TR and the receiver AR, since with the push button I3 depressed the di rectional relay DR is picked up and its front contact 23 is closed to connect the coils 4 and 5 to the transmitter TR, and with the push button released the relay DR is released and its back contact 21 is closed to connect the coils to the receiver AR.

The output of receiver AR is connected with the primary winding 28 of a transformer TI with the result that there is induced in the secondary winding 29 of the transformer TI frequencies corresponding to the modulating frequencies of the carrier current picked up by the inductor coils 4 and 5. The secondary winding 29 of the transformer TI is adapted to be con- That is to say, the inductor nected with either a call selecting circuit or with an operating circuit of a telephone receiving device. Normally, the secondary winding 29 is connected with the call selecting circuit which includes a reactor 30, a condenser 3i and a front contact 32 of a relay R2 to be referred to later. A portion of the reactor 30 is connected with the input terminals of a full wave rectifier 33, the output terminals of which are connected with the winding of a relay RI. This call selecting circuit is tuned to resonance at a given frequency such, for example, as 700 cycles per second. Consequently, the relay R! is energized in response to a carrier current modulated at the single frequency of 700 cycles per second at such time as the relay R2 is energized and its front contact 32 is closed. The relay R2 is normally held energized by a stick circuit extending from the B terminal of the current source over back contact 34 of the relay RI, its own front contact 35, winding of the relay, and to the opposite terminal C of the current source. The relay R2 is further provided with a pickup circuit easily traced and which includes a manually operated contact 36 when depressed to the position indicated by the dotted lines in the drawings. The relay R2 when deenergized transfers the secondary winding 29 of the transformer Tl from the call selecting circuit to the operating circuit of a loud speaker LS by opening the front contact 32 and closing a back contact 31. That is to say, upon receiving a calling current comprising a carrier modulated at the frequency of 700 cycles per second, the relay RE is picked up and the relay R2 is deenergized with the result that the output of the receiver AR is transferred from the call selecting circuit to the operating circuit of the loud speaker LS. Once the loud speaker LS is connected with the secondary winding 29 it remains in circuit ready to respond to any subsequent telephone current until the manually operated contact 36 is depressed and the relay R2 is reenergized to transfer the secondary winding 29 back to the call selecting circuit.

Referring now to the wayside station equipment SE, a microphone M is equipped with a manually operated handle Hi having connected therewith a circuit controlling contact I2; and on which there is mounted a push button us the same as the microphone handle M of the train carried equipment. The handle hi is capable of being operated to a normal, a calling and a communicating position, and in conjunction with the push button Hi governs a calling relay CR and a directional relay DR in exactly the same manner as the corresponding relays of the train carried equipment are controlled by the handle M and its associated push button I3. It is thought, therefore, that it is unnecessary to repeat this description.

A transmitter TR and a receiver AR are provided for the wayside station equipment which are preferably similar to the corresponding devices of the train carried equipment. As pointed out hereinbefore, these devices are preferably of the form disclosed in the copending application Serial No. 658,932.

The input of the wayside station transmitter TR is connected with the microphone M through a back contact 15 of the calling relay CR with the result that the carrier current generated by the transmitter TR is modulated with voice frequencies whenever the relay CR is deenergized. Relay-CR when picked up, opens the connection with the microphone and closes at a front contact it a coupling circuit wherewith the carrier is modulated at a given single frequency of, say, 700 cycles per second. Hence, the transmitter TR of the wayside station is made to supply a carrier telephone current or a carrier calling current at the discretion of the operator at the Wayside station.

The output of the receiver AR of equipment SE is supplied to the primary winding 12 of a transformer T2 the secondary winding 4| of which is normally connected With a call selecting circuit over a front contact d2 of an associated relay R2, and which circuit includes a reactor 43 and a condenser 14. This call selecting circuit is tuned to resonance at 700 cycles per sec- 0nd, that is to say, it is tuned to resonance at the frequency of the calling current delivered by the transmitter TR of the train carried equipment. A portion of the reactor 33 is connected with the input terminals of a rectifier ii, the

output terminals of which are connected with the winding of an associated relay Rl with the result that the relay Ri will be energized whenever a calling current corresponding to a carrier modulated at 700 cycles per second is impressed upon the input of the receiver AR. The relay RI of equipment SE controls at its back contact 38 a stick circuit for the associated relay R2 and which circuit includes a front contact 39 of that relay as will be readily understood by an inspection of Fig. 1. The station relay R2 is further provided with a pickup circuit easily traced and which includes a manually operated contact is. This relay R2 of the wayside station equipment governs the call select- 1 ing circuit at its front contact 52 and completes the connection for the secondary winding il of transformer T2 with the operating circuit of an associated loud speaker LS at its back contact 43. It follows that the output of the receiver AR of the wayside station is normally connected with the associated call selecting circuit and is automatically transferred to the associated loud speaker in response to a proper calling current,

and is manually restored to the call selecting circuit through the medium of the contact it).

The wayside station equipment SE also includes a coupling transformer T5 through the medium of which energy is received from or transmitted to the different track communication 1 transformers TW, TX, TY and TZ. A winding M of the transformer T5 normally connected with the input circuit of the station receiver AR over the back contacts l5 and it of the directional relay DR and is transferred to the output of the transmitter TR when the directional relay DR is energized and its front contacts 4! and. 48 are closed.

The windings 5t, 5t, 52 and 53 of transformer T5 are each adapted to be connected with a winding of the track communication transformers TW, TX, TY and T2, respectively, through the medium of a selector switch SS which will now be described. The selector switch SS may take different forms and preferably comprises a disc 55 of suitable material and which is adapted to be rotated in either direction about the pivot 51, a knob 58 being mounted on the disc 56 to facilitate the disc being rotated manually. Attached to the disc 56 are five contact fingers 59, hi], iii, 62 and 63, the four contact fingers 59, 68, iii and 62 being positioned on one semi-circumference of the disc 56 substantially 30 apart, and the fifth contact finger 63 being positioned on the opposite semi-circumference of the disc.

The switch SS is provided with four pairs of stationary contacts 86 11 88 and 9-9, which are located in the path of the contact fingers for engagement therewith and which are positioned substantially 30 apart. It is clear, therefore, that with the disc 56 set at the position illustrated in Fig. 1, the contact finger 59 bridges the contacts 3-45 the contact finger 60 bridges the contacts 'll' the contact finger 6| bridges the contacts 89 and the contact finger 62 bridges the contacts 99 It is also clear that the disc 56 can readily be rotated to a position Where the contact finger 63 engages any one of the pair of stationary contacts as may be desired, and when so rotated, the remaining contact fingers 59, 69, El and 62 are in a position to be out of engagement with the stationary contacts. The switch SS will ordinarily occupy the position illustrated in the drawings and which position I shall refer to as being its standby or normal position. With the switch SS set in the standby position and the contacts 66 bridged by the contact finger 5-9, the winding 53 of the transformer T5 is connected with the winding 64 of transformer TZ over wires 65 and 66, a condenser 551 being preferably interposed in the wire 69. The bridging of the contact l--'l by the contact finger 69 connects the winding 52 of the transformer T5 with the winding 68 of the track transformer TY over wires 69 and 10, a condenser H being interposed in the wire 10. In like manner, the bridging of the contacts 8---8 by the contact finger Bl connects the winding 5| with the winding 18 of the track transformer TX, a condenser ?9 preferably being interposed in the connection. Furthermore, the bridging of the contacts 9-9 by the contact finger 62 completes the connection of winding 50 of transformer T5 with a winding of the track transformer TW, a condenser 8| being preferably interposed in the connection. The condensers 6?, H, 19 and 8! are positioned as shown to tune out the reactance of the associated circuit. Such condensers may not be necessary since this tuning could be accomplished in the transmitter TR and receiver AR but they are shown in Fig. 1 in the places indicated to keep the receiving circuit as selective as possible in order to reduce the noise picked up from the traffic rails. Hence, with the selector switch SS set at its standby position, the windings 59, 5|, 52 and 53 of the coupling transformer T5 are each connected with a winding of the respective track transformer, connecting all four tracks to the receiver AR.

In Fig. 1, it is assumed that the tracks Y and Z carry no ordinary track signaling current, whereas, tracks W and X are assumed to be provided with track circuits common in railway signaling. It will be understood, of course, that the traffic rails II and H of the tracks Y and Z are preferably bonded in the usual manner. Since tracks Y and Z are not arranged with the usual track circuits there is no objection to tying one traific rail to the other. In the case of track Z, insulated rail joints 82 and 83 are placed in the trafiic rails II and H respectively, adjacent the Wayside station S, and the winding 84 of the transformer TZ is connccted to the two rails in parallel on both sides of the joints 82 and 83, the transformer T2 being of the air core type. In like manner, insulated rail joints 95 and 86 are placed in the traffic rails I I and H of the track Y, respectively, adjacent the station S and a winding 8'! of the transformer TY is connected to the two rails in parallel on both sides of the joints and 86. The transformer TY is of the iron core type, there being little difference whether an air or an iron core transformer is used. In the case of the tracks W and X, since these tracks are assumed to be equipped with the usual track circuits, the traffic rails may not be tied together and thus a separate transformer winding is provided for each rail. In the case of the track X, the insulated joints 88 and 89 are placed in the traffic rails H and II, respectively, conveniently located with respect to the wayside station S and windings 90 and SI of the transformer TX are connected around the insulated joints 88 and 89, respectively. In the case of the track W, the insulated rail joints 92 and 93 are placed in the rails II and H respectively, conveniently located with respect to the wayside station S and windings 94 and 95 of the transformer TW are connected across the joints 92 and 93, respectively. Transformer TX is shown as an air core type transformer and the transformer TW is shown as an iron core type transformer. Since the carrier current employed with my system is of relatively high frequency, the windings 90 and SH of the transformer TX, and the windings 94 and 95 of the transformer TW introduce relatively small impedance into the respective track circuit; it being understood that the insulated rail joints 88 and 89 of track X, and the insulated rail joints 92 and 93 of the track W are not the usual insulated rail joints used to separate adjacent track circuits but are additional joints located at an intermediate point in the track circuit. Furthermore, since the tracks W and X are assumed to be equipped with the usual track circuits and consequently are divided into sections by the usual insulated rail joints, it will be understood that bypass connections of any convenient type, several of which are well known to the art, may be provided at the insulated joints of adjacent track circuits for conveying the communication current from the rails of one track circuit to the rails of the next track circuit but blocking the flow of the track circuit current.

With the train V occupying the track Z within a reasonable distance of the wayside station S either to the right or to the left of the insulated rail joints 82 and 83, and its transmitter TR rendered active to supply a carrier calling current or a carrier telephone current; a like current will flow in the winding 8 of the transformer TZ inducing a corresponding current in the winding 64 of that transformer. Assuming the switch SS to be set in its standby position so that the contacts B6=- are bridged, the current induced in the winding 64 of transformer T2. will flow in the winding 53 of transformer T5 and will induce in turn a corresponding current in the winding 44 of that transformer which current will then be applied to the input of the receiver AR. On the other hand, if the transmitter TB of the wayside station is rendered active to supply a calling current or a telephone current, this current will be fed across the insulating rail joints 82 and 83 directly into the rails of the track Z in parallel. The result will be that a corresponding current will be induced in the inductor coils 4 and 5 of the train V assuming, of course, that train V is within reasonable distance of the wayside station either to the right or to the left of the insulated rail joints 82 and 83. The current induced in the inductor coils 4 and 5 will be applied to the input of the train carried receiver AR. It is to be noted that the energy transmitted from the wayside station to the train carried equipment is fed directly into the traffic rails across the insulated rail joints and that the energy transmitted from the train carried equipment to the wayside station equipment is received directly from the traiiic rails at the wayside station, whereas, in the case of the train carried equipment, the energy is transferred across a relatively long air gap existing between the inductor coils 4 and 5 and the traiiic rails. For this reason, the transmitter TB of the wayside station equipment may not be required to amplify the energy to as high an energy level as the train carried transmitter, and the wayside station receiver AR may not need such a high gain amplifier as the train carried receiver.

In the event the train V occupies the track Y and the selector switch SS is set at its standby position, two-way communication between the train carried equipment TE and the wayside station equipment SE is permitted in the same manner as described above in connection with the train occupying the track Z, the track transformer TY now functioning as the medium for transferring energy to and from the traffic rails. In like manner, two-way communication is permitted between the wayside station equipment and the train carried equipment when the train occupies either track X or W, the transformer TX or TY functioning as the medium for transferring the energy between the wayside station equipment and. the traflic rails.

In Fig. 1, the reference character L designates a line wire paralleling the railway tracks W, X, Y and Z, such for example, as the common line wire strung along a railway track and used for telegraph 'or other signaling purposes. I have found that such a paralleling line wire helps to transmit carrier current in systems of the type here involved. The voltage is induced in the line wire and the circuit is completed through the capacities of this line wire to ground and to the trafiic rails. Thus the line wire L having a calling or carrier telephone current induced therein provides a channel for the current to travel in either direction from the point of induction, thence to ground, say through a condenser 96, ground 97 to ground 99, condenser 98 and back to the line wire L some distance on the other side of the point of induction. It should be realized that these condensers 96 and 98 are the inherent distributed capacities between the line wire L and ground and do not represent anything added to the line. They are, of course, distributed throughout the entire length of the line wire L, and are shown dotted in Fig. 1 to visualize the channel in order that it may be more clearly understood. Distributed capacities H30 and I8! between the line wire L and the traffic rails of the several railway tracks also exist inherently without the addition of any physical apparatus, and provide a further closed channel for the transmission of the carrier current. These capacities Hi0 and H are also shown dotted in Fig. 1 in order to visualize their existence, although as stated above, they represent no additional physical apparatus. Utilization of this additional communicating channel is provided by adding a transformer T6 at the wayside station S, which links the line wire L with the wayside equipment in the following manner. The magnetizable core N2 of transformer T6 encloses the line wire L and has mounted thereon a winding I 03 which is connected with a winding IM of the coupling transformer T5 over wires I05 and I06, a condenser it! and a contact I08 of a manually operated key K being interposed in the wire I06. The manually operated key K is provided so that the use of this additional channel may be selected by the operator at the wayside station independent of whether or not he is using the cominunicating channel through the traflic rails. he normal standby position of the key K would be, say, with the contact I08 closed and then when communication is in progress, the closed or open position for the key K would be determined by trial in accordance as to which will give the best transmission. Although transformer T6 is shown in Fig. l with only a single turn of the line wire L through it, a modified form is shown in Fig. 5 wherewith a second winding I09 is mounted on the core 12 and this winding me is connected in series with the line wire L. Since the carrier current employed is of relatively high frequency. this transformer T6 would introduce relatively small impedance into the telegraph or signaling circuit in which the line wire L is ordinarily employed. It will be understood, however, that the line wire L may be an additional line wire placed parallel with the railway tracks, and whose only function is that of serving as a communicating channel for my system should it seem desirable to do so. In the event the line wire L is an additional line wire serving as part of the communicating channel for my system, the capacities 96, 98, it!) and Ill! may each be made a physical apparatus in parallel with the inherent distributed capacities should it seem desirable to do so. It follows that energy is transferred to the line wire L from the wayside station equipment through the medium of the transformer T6, and the energy induced in the line wire L will travel out in either direction from the transformer T6, to ground and the traffic rails through the distributed capacities and then back to the line on the other side of the transformer T6. Current will be in turn induced in the traffic rails by virtue of the distributed mutual electromagnetic induction of the line wire to the traffic rails, and will flow in the rails in multiple. On the other hand, energy induced in the traffic rails by the train carried equipment will cause current to flow not only through the channel including the trafiic rails but will also cause current to flow in the channel including the line wire L, by virtue of the distributed mutual induction of the rails to the line wire and also by virtue of the distributed capacities and this latter current will induce a corresponding current in the winding 1 03 of transformer T6.

Assuming that the key K and the switch SS of Fig. 1 are both set in their usual standby positions, and that the crew of the train V desires to telephone to the operator at the wayside station S, the procedure will preferably be as follows: The operator of the train will first move his handle M to the calling position and hold it there for a period in order to transmit a calling current to the trafiic rails of the track Z, or whichever track the train may be occupying at the time. This calling current will flow in the track winding of the corresponding track transformer T2, TY, TX or TW, and also in the line wire L, and hence will be in turn, ap plied to the receiver AR of the station equipment. After having been filtered, amplified and detected by the receiver AR, the calling current will be applied to the call selecting circuit with the result that the loud speaker LS will be automatically switched into the circuit, and will sound a note indicating to the station operator that telephone communication with him is desired. The operator at the station S will then determine over which track the signal is coming by rotating the selector switch SS to bring the single contact finger 63 into engagement with the different stationary contacts, in turn, until he receives the strongest signal. The key K would also be operated to determine if the line wire L was assisting in the transmission. Having determined from what track the strongest signal was being received, which would be, in the absence of unusual track conditions, that track which the train occupies, the station operator would set the switch SS for that track in order to obtain the best transmission and to avoid interferencewith any other train which might be occupying one of the other tracks. The station operator will now move his handle I l to the calling position for a period to supply to the rails and to the line wire L a calling current which will be picked up by the inductor coils 4 and 5 and will be applied to the call selecting circuit of equipment TE and the train-carried loud speaker will be connected with its receiver AR. The station operator will next move his handle l4 to the communicating position. The train operator subsequent to the sending of a calling current will move his handle It to the communicating position. The two operators will now carry on the desired conversation by manipulating their push buttons to set up the sending and the receiving conditions for their equipments. When the desired communication is completed, the switch SS and key K would be restored to their standby positions connecting alltracksas well as the line wire L with the receiver of the wayside station. At the completion of the conversation, each operator would also restore his respective microphone handle to itsnormal position and would operate the .respective contacts 36 and M1 to reestablish the call selecting circuits.

If the station operator desires to communicate with a train crew, he would ordinarily know the trackthe train was on and he could at once rotate the selector switch SS to the position to select that track. The station operator would then move his handle M to the calling position for a period and then to the communicating position. The calling current sent out from the station would be received aboard the train first by the call selecting circuit which would function to automatically switch the loud speaker LS into circuit with the result that the loud speaker'would sound a note calling the train crews attention that telephone conversation is desired with them. The train operator would now move his handle it to the communicating' position. From this point on telephone communication would be accomplished in the manner described above. After the conversation was completed, the station operator would reset the switch SS to its standby position to again connect all of the tracks with the station receiver, and would restore the handle I l to its normal position and operate the contact iii to reestablish the call selecting circuit. The operator on the train would, in like manner, re-

store his microphone handle H! to its normal position and operate the contact 36 to reestablish his call selecting circuit. In the event the station operator did not have the information as to which track the train occupied, he would send out the calling current and then afterwards determine by trial the proper position for the selector switch SS. In some cases, the best communications might be obtained over the line Wire L independent of the channel through the traflic rails alone, in which event the selector switch SS would be set in a position for disconnecting all of the tracks. It is to be noted that by operating the handle M on the train or the handle M at the wayside station to their respective calling positions for long or short periods in accordance with a prearranged code, a code message can be sent which will be reproduced at the opposite station by the sounding of the loud speaker. As a matter of fact, I have found that by choosing the frequency for the calling current at the voice frequency where maximum transmission occurs, namely, at about 700 cycles per second, code messages can be clearly received over distances and through poor transmitting conditions where a telephone conversation would be unintelligible.

Since the frequency of the carrier current is relatively high, the windings of the track communication transformers could be made so that they would not interfere with the ordinary signaling or propulsion currents in case these are used. As stated hereinbefore, the insulated rail joints for tracks W and X of Fig. l are not the same as separate the traffic rails between adjacent track circuits but are joints added for use in the communicating system only. In case insulating rail joints are already installed at the wayside station in connection with track circuits, the additional insulating joints will not be necessary for coupling the wayside station equipment of my system with the traflic rails, and connection can be made across the joints already installed. Figs. 2, 3 and 2 disclose means for using the same insulating rail joints employed to. insulate adjacent track circuits for the communicating system. Fig. 2 shows a modified form for connecting an air core transformer T! across the two insulated rail joints H0 and HI separating two adjacent direct current track circuits. The winding H2 of transformer T1 is connected across the insulated joint III), a condenser H4 being interposed in the connection; and a second winding H3 of the transformer T1 is connected across the in sulated joint IH with a condenser H5 interposed in the connection. This arrangement provides an absolute block for the direct current track circuit current and is the electrical equivalent to the connection at track X of Fig. 1 for the transferring of the communicating current to and from the trafiic rails in parallel. It is to be noted that in the event the transformer Tl is substituted for the transformer TX of Fig. l, the condensers H4 and H5 could take the place of the condenser 79 interposed in the connection between the transformer TX and the winding 5| of the transformer T5. The impedance of condensers H4 and H5 would be so high at the usual frequency of the alter nating current track circuit current that this connection could also be used where alternating current track circuits are installed. Fig. 3 shows a preferred method for connecting across the mid point of resistances. H6 and H1 are resistances connected across the opposite traffic rails on opposite sides of the two insulated rail joints MS and H9 separating two adjacent track circuits, the resistances H6 and H! being so proportioned as not to shunt the respective track circuit. The winding I20 of a track communication transformer T8 would be connected at the mid points of the resistances H6 and ill while its other winding i2l would be connected with a winding of the coupling transformer T in a manner similar to Fig. 1. Fig. 4 shows a preferred connection where the traffic rails are used to conduct propulsion currents. I22 and H23 are the usual insulated rail joints separating two adjacent track circuits, and I2 4 and 125 are the usual impedance bonds connected across the rails on either side of the insulated joints for conducting the propulsion current around these joints. In the tie between the mid points of the bonds I24 and H25 a single turn winding [26 of a track communication transformer T9 is interposed. The other winding I21 of transformer T9 would be connected with a winding of the coupling transformer T5 in the usual manner and this winding i2?! would have as many turns as desired to properly match the impedance of the track circuits. The single turn winding 626 would introduce only a small amount of impedance to the propulsion current.

Although I have herein shown and described only certain forms of apparatus embodying my invention, it is understood that various changes! and modifications may be made therein within the scope'of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

l. A railway communicating system including a stretch of railway track, a wayside station; communicating equipment at said station including a transmitter, a receiver" and a circuit adapted to be connected to either the transmitter or receiver; an insulated rail joint disposed in each of the traiiic rails of the track, a transformer having connections with the two rails of the track in parallel on both sides of said joints, a winding for said transformer connected with said circuit to supply alternating current to the rails in multiple when the transmitter is connected with said circuit and to receive current from the rails in multiple when the receiver is connected with said circuit; and a station remote from the first mentioned station including a transmitting device, a receiving device and a. circuit adapted to be connected with. either of said devices and in inductive relation with. said rails in parallel whereby two-way communication between the two stations may be effected through the traffic rails.

2. A railway communicating system including a railway track, a train adapted to travel on said track, a wayside station along the track; communicating equipment at said station including a transmitter, a receiver and a circuit adapted to be connected to either the transmitter or receiver; an insulated rail joint disposed in each of the trafiic rails of said track, a transformer having connections with the two rails of the track in parallel on both sides of said joints, a winding for said transformer connected with said circuit to supply alternating current to the rails in multiple when the trans mitter is connected with said circuit and to receive current from the rails in multiple when the receiver is connected with said circuit; and train carried equipment including a transmitting device, a receiving device and a circuit adapted to be connected with either of said devices and in inductive relation with the trafflc rails in parallel whereby two-way communication between the wayside station and the train may be effected through the traiiic rails.

3. A railway communicating system including a stretch of railway track, a wayside station; communicating equipment at said station including a transmitter, a receiver and a circuit adapted to be connected to either the transmitter or receiver; an insulated rail joint disposed in each of the traffic rails of the track, a trans former, means for connecting a winding of the transformer with the two traffic rails on both sides of said joints and including two conductors one on each side or the joints connected with the two rails in parallel, other means for connecting another winding of said transformer with said circuit to supply alternating current to the rails in multiple when the transmitter is connected with said circuit and to receive current from the rails in multiple when the re ceiver is connected with said circuit; and a station remote from the first mentioned station including a transmitting device, a receiving device and a circuit adapted to be connected with either of said devices and in inductive relation with said rails in parallel whereby two-way communication between the two stations may be effected through the trafiic rails.

l. A railway communicating system including a stretch of railway track, a wayside station; communicating equipment at said station including a transmitter, a receiver and a circuit adapted to be connected to either the transmitter or receiver; an insulated rail joint disposed in each of the trafiic rails of the track, a transformer, a first winding of said transformer connected across the insulated joint of one trains rail, a second winding of said transformer connected across the insulated joint of the other raffic rail, a third winding of said transformer connected with said circuit to supply alternating current to the rails in multiple when the trans mitter is connected with said circuit and to receive current from the rails in multiple when the receiver is connected with said circuit; and a station remote from the first mentioned station including a transmitting device, a receiving device and a circuit adapted to be connected with either of said devices and in inductive relation with said rails in parallel whereby two-way communication between the two stations may be effected through the trafiic rails.

5. A railway communicating system including a plurality of railway tracks, a train adapted to travel on said tracks, a wayside station; communicating equipment at said station including a transmitter, a receiver and a circuit adapted to! be connected with either the transmitter or the receiver; a coupling transformer having a first winding connected with said circuit and a plurality of track windings one for each of said tracks, a circuit means to connect each of said track windings with the trafiic rails of the respective track in parallel to supply alternating current to the rails of each of said tracks in multiple when the transmitter is connected with said circuit and to supply current to the receiver from the rails of any one of said tracks when the receiver is connected with said circuit; and train carried equipment including a transmitting device, a receiving device and a circuit adapted to be connected with either of said devices and in inductive relation with the traffic rails in parallel whereby two-way communication between the wayside station and the train may be effected through the traffic rails with the train occupying any one of the plurality of tracks.

6. A railway communicating system including a plurality of railway tracks, a train adapted to travel on said tracks, a wayside station; communicating equipment at said station including a transmitter, a receiver and a circuit adapted to be connected with either the transmitter or the receiver; a coupling transformer having a first winding connected with said circuit and a plurality of track windings one for each of said tracks, insulated rail joints disposed in the trafiic rails of each of said tracks, a circuit means for each of said track windings and connected with the traffic rails in parallel on both sides of the insulated joints of the respective track to supply alternating current to the rails of the respective track in multiple when the transmitter is connected with said circuit and to supply current to the receiver from the rails of the respective track when the receiver is connected with said circuit; and train carried equipment including a transmitter, a receiver and a circuit adapted to be connected with either of said devices and in inductive relation with the traffic rails in parallel whereby two-way communication between the wayside station and the train may be effected through the traffic rails with the train occupying any one of the plurality of tracks.

7. A railway communicating system including a plurality of railway tracks, a train adapted to travel on said tracks, a wayside station; communicating equipment at said station including a transmitter, a receiver and a circuit adapted to be connected to either the transmitter or the receiver; a coupling transformer having a first winding connected with said circuit and a track winding for each of said tracks, insulated rail joints disposed in the traflic rails of each of said tracks, a track transformer for each of said tracks and having a winding connected with the rails in parallel on both sides of the joints of that track, a second winding for each of the track transformers connected with the cor responding track winding of the coupling transformer to supply alternating current to the re ceiver from the rails of the respective track in multiple when the receiver is connected with said circuit and to supply current to the rails of the respective track in multiple when the transrnitter is connected with said circuit; and train carried equipment including a transmitting device, a receiving device and a circuit adapted to be connected with either of said devices and in inductive relation with the trafiic rails in parallel whereby two-way communication between the wayside station and the train may be efiected through the traffic rails with the train occupying any one of the plurality of tracks.

8. A railway communicating system including a plurality of railway tracks, a train adapted to travel on said tracks; train carried equipment including a transmitting device, a receiving device and a circuit adapted to be connected with either of said devices and in inductive relation with the trafiic rails in parallel; a wayside station; communicating? equipment at said station including a transmitter, a receiver and a circuit adapted to be connected to either the transmitter or the receiver; a coupling transformer having a first Winding connected with said circuit and a plurality of track windings one for each of said tracks, a circuit means connected with each of said track windings adapted when closed to transfer energy between the winding and the trafiic rails of the respective track in multiple, a manually operated switch having a standby position for closing all of said circuit means, and said switch adapted to be set in other positions for closing any one of said circuit means only whereby communication between the train and the wayside station through the traffic rails may be initiated from any one of said plurality of tracks and then selectively restricted to the particular track occupied by the train.

9. A railway communicating system including a plurality of railway tracks, a train adapted to travel on said tracks; train carried apparatus including a transmitting device, a receiving device and a circuit adapted to be connected with either of said devices and in inductive relation with the traffic rails in parallel; a wayside station; communicating equipment at said station including a transmitter, a receiver and a circuit adapted to be connected with either said transmitter or said receiver; insulated rail joints disposed in the trafiic rails of each of said tracks, a track transformer for each track connected with the rails in parallel on both sides of the insulated joints, circuit means for each track including a winding of the respective track transformer and adapted when closed to transfer energy between the circuit of the station equipment and the track transformer to supply current to the rails in multiple when the transmitter is connected with the circuit and to supply current from the rails to the receiver when the receiver is connected with the circuit, a manually operated switch having a standby position for closing all of said circuit means, and said switch adapted to be set in other positions for closing any one of said circuit means only whereby communication between the train and the wayside station through the trafiic rails may be initiated from any one of the plurality of tracks and then selectively restricted to the particular track occupied by the train.

10. A railway communicating system including a plurality of railway tracks, a train adapted to travel on said tracks; train carried equipment including a transmitting device, a receiving device and a circuit adapted to be connected with either of said devices and in inductive relation with the trafiic rails in parallel; a wayside station; communicating equipment at said station including a transmitter, a receiver and a circuit adapted to be connected to either the transmitter or the receiver; a coupling transformer having a first winding connected with said circuit and a plurality of track windings one for each of said tracks, insulated rail joints disposed in the traffic rails of each of said tracks, a track transformer for each track connected with the rails in parallel on both sides of the insulated joints, a circuit means for each track including a winding of the respective track transformer and the respective track winding of the coupling transformer to supply alternating current to the trafiic rails of the respective track in multiple when the transmitter is connected with the circuit and to supply current from the rails to the receiver when the receiver is connected with the circuit, and a manually operated switch for selectively controlling said circuit means.

11. A railway communicating system including a plurality of railway tracks, a train adapted to travel on said tracks; train carried equipment including a transmitting device, a receiving device and a circuit adapted to be connected with either of said devices and in inductive relation with the traffic rails in parallel; wayside equipment including a transmitten'a receiver and a circuit adapted to be connected with either the transmitter or the receiver; circuit means for each track including a transformer adapted to transfer energy to and from the traffic rails of the track in parallel, and a manually operated switch for selectively coupling the circuit of the wayside equipment with any one of the circuit means whereby two-way communication between the wayside equipment and the train carried equipment may be effected through the traffic rails of the track occupied by the train.

12. A railway communicating system including a railway track, a train adapted to travel on said track; train carried equipment including a transmitting device, a receiving device and a circuit adapted to be connected with either of said devices and in inductive relation with the traffic rails of the track in parallel; a wayside station; communicating equipment at said station including a transmitter, a receiver and a circuit adapted to be connected with either the transinitter or the receiver; a line wire paralleling said track and so positioned with respect tothe rails that, solely by virtue of the distributed mutual induction between the line wire and the rails, current flowing in the rails induces current in the line wire and current flowing in the line wire induces current in the rails; and a transformer inductively coupled with said line wire and having a winding connected with said circuit of the wayside station to supply alternating current to said line wire when the transmitter is connected with the circuit and to supply current from the line wire to the receiver when the receiver is connected with said circuit whereby communication between the wayside station and the train may be effected through the line wire and the distributed mutual indication between the line wire and the trafiic rails of the track.

13. A railway communicating system including a railway track, a train adapted to travel on the track; train carried equipment including a transmitting device, a receiving device and a circuit adapted to be connected with either of said devices and in inductive relation with the trafiic rails in parallel; a line wire paralleling said. track. and so disposed with respect to the rails that current istransferred between the line wire and the rails solely by virtue of the distributed mutual induction between the line wire and the rails, a remote station; and communicating equipment at said remote station ineluding a transmitter, a receiver and a circuit adapted to be connected with either the transmitter or the receiver and electrically coupled with said. line wire whereby communication between the remote station and the train may be effected through the trafiic rails and the line wire.

14. A railway communicating system including a railway track, a trainadapted to travel on said track; train carried equipment including a transmitting. device, a receiving. device and a circuit adapted. to be connected with either of said devices and: inductive relation with the traffic rails in. parallel; a wayside station; communicating equipment at said station including a transmitter, a receiver and a circuit adapted to be connected with either the transmitter or the receiver; a line wire paralleling said track, a line transformer inductively coupled with the line wire and having a winding adapted to be connected with the circuit of the wayside station, a track transformer inductively coupled with the trafiic rails of the track in parallel and having a winding adapted to be connected with the circuit of the wayside station, and manually operated means for governing the connections between the circuit and said transformers whereby communication between the wayside station and the train may be effected through the channel including the traffic rails, or through the channel including the line wire and the distributed capacity existing between the line wire and the traffic rails or through both of said channels.

15. A railway communicating system including a plurality of railway tracks, a train adapted to travel on said tracks; train carried equipment including a transmitting device, a receiving device and a circuit adapted to be connected with either of said devices and in inductive relation with the traffic rails in parallel; a wayside station; communicating equipment at said station including a transmitter, a receiver and a circuit adapted to be connected with either the transmitter or the receiver, a line wire paralleling said railway tracks, a .line transformer inductively coupled with the line wire and having a winding adapted to be connected with the circuit of the wayside station, a track transformer for each of the railway tracks inductively coupled with the traffic rails of the track in parallel and each having a winding adapted to be connected with the circuit of the wayside station, and manually operated means for selectively governing the connections between said wayside circuit and said line and track transformers.

16. A railway communicating system including, a railway track, a train adapted to travel on said track, train carried equipment including a receiver adapted to receive and demodulate a modulated carrier current and a circuit connected with said receiver and in inductive relation with the traffic rails in parallel, a wayside station, station equipment including a transmitter adapted to supply a modulated carrier current, a line wire paralleling said railway track, a transformer inductively coupled with said line wire and having a winding connected with said transmitter to supply the modulated carrier current to said line wire whereby communication between the wayside station and the train may be effected through the line wire and the distributed capacity between the line wire and the traffic rail of the track and ground.

17. A railway communicating system including a stretch of railway track divided into track circuits separated by insulated rail joints, a train adapted to travel on said track, a wayside station along the track; communicating equipment at said station including a transmitter, a receiver and a circuit adapted to be connected to either the transmitter or the receiver; a transformer, circuit means for connecting the transformer with the two trafiic rails on both sides of a pair of insulated rail joints separating two adjacent track circuits and arranged that the two rails of each track circuit are in parallel, means included in said circuit means to block the flow of track circuit current from one track circuit to the other, other means for connecting said transformer with said circuit of the wayside station to supply current to the rails of each track circuit in multiple when the transmitter is connected with said circuit and to receive current from the rails in multiple when the receiver is connected with said circuit; and train carried equipment including a transmitting device, a receiving device and a circuit adapted to be connected with either of said devices and in inductive relation with the trafiic rails in parallel whereby two-way communication between the wayside station and the train may be effected through the traffic rails.

18. In combination with two adjacent track circuits separated by two opposite insulated rail joints; a transformer having a first, a second and a third winding; means for connecting the first winding around one of said joints including a condenser, means for connecting the second winding around the other of said joints including another condenser; communicating equipment including a transmitter, a receiver and a circuit adapted to be connected with either the transmitter or the receiver; and means for connecting the third winding of the transformer with said circuit to supply current to the rails of each track circuit in multiple when thetransmitter is connected with said circuit and to receive current from the rails in multiple when the receiver is connected with said circuit.

19. In combination with two adjacent track circuits separated by two opposite insulated rail joints, a resistor for each track circuit connected across the trafiic rails, a transformer having a first and a second winding, means for connecting said first winding between the mid points of said resistors; communicating equipment including a transmitter, a receiver and a circuit adapted to be connected with either the transmitter or the receiver; and means for connecting the second winding of said transformer with said circuit to supply current to the rails of each track circuit in multiple when the transmitter is connected with said circuit and to receive current from the rails of each track circuit in multiple when the receiver is connected with said circuit.

20. In combination with two adjacent track circuits separated by two opposite insulated rail joints and an impedance bond for conducting propulsion current around said joints, a transformer having a single turn winding and a multiple turn winding; communicating equipment including a transmitter, a receiver and a circuit adapted to be connected with either the transmitter or the receiver; means for connecting the single turn winding of the transformer in series with the mid connection of said bond, and means for connecting the multiple turn winding of the transformer with said circuit to supply current to the rails of each track circuit in multiple when the transmitter is connected with said circuit and to receive current from the rails in multiple when the receiver is connected with said circuit.

21. A railway communication system comprising a stretch of railway consisting of a plurality of tracks, a train adapted to travel on said tracks, train-carried equipment including a receiver of periodic current and a circuit disposed in inductive relation with the trafiic rails, a line wire, means including a capacitance for connecting the line wire with at least one rail of each of said tracks at one end of said stretch of tracks, means for effectively connecting the line wire with at least one rail of each of said tracks at the other end of said stretch of tracks, a wayside station, communication equipment at the Wayside station including a transmitter of periodic current, and a line transformer having one winding connected with the transmitter and another winding serially connected with the line wire to supply current from the transmitter to the rails of said tracks for effecting communication between the station and the train when occupying any one of said tracks.

22. A railway communication system comprising a stretch of railway consisting of a plurality of tracks, a train adapted to travel on said tracks; train-carried equipment including a transmitter of periodic current, a receiver of such current and a circuit adapted to be connected to either the transmitter or the receiver and disposed in inductive relation with the traffie rails; a line wire, means! including a capacitance for connecting the line wire with at least one rail of each said tracks at one end of said stretch, means for effectively connecting the line wire with at least one rail of each of said tracks at the other end of said stretch of tracks, a wayside station; communication equipment at the wayside station including a transmitter of periodic current, a receiver of such current and a circuit adapted to be connected to either the transmitter or the receiver; and a line transformer having one winding connected with said wayside station circuit and another winding serially connected with the line wire whereby two-way communication between the station and the train may be effected through the circuit including the line wire and the traffic rails when the train occupies any one of said tracks.

23. A railway communicating system including, a railway track, a train adapted to travel on said track; train-carried communication equipment including a transmitting device, a receiving device and circuit means operative to electrically couple said devices with the traiiic rails in parallel; a line wire extending along the railway and disposed to one side of the trafiic rails for transferring communication current between the line wire and the rails solely by virtue of the distributed mutual induction between the line wire and the rails, a wayside station; communication equipment at said station including a transmitter, a receiver and circuit means operative to effectively couple the transmitter and the receiver with said line wire whereby communication between the wayside station and the train is effected through the line wire and the traflic rails by virtue of the distributed mutual induction between the line wire and the traffic rails.

24. A railway communicating system including, a railway track, a train adapted to travel on said track; train-carried communication equipment including transmitting apparatus, receiving apparatus and circuit means operative to electrically couple the transmitting apparatus and the receiving apparatus with the trafiic rails in parallel; a wayside station, communicating equipment at said station including transmitting apparatus and receiving apparatus, a line wire extending along the railway substantially parallel to the traffic rails and disposed with respect to the rails for transferring communication current between the line wire and the rails solely by virtue of the distributed mutual induction between the line wire and the rails, and circuit means at said station operative to couple its transmitting apparatus and receiving apparatus with the line wire and including a line transformer having a winding interposed in the line wire, whereby communication between the wayside station and the train is effected through the line wire and the traffic rails by virtue of the distributed mutual induction between the line wire and the trafiic rails.

25. A railway communicating system including, a railway track, a train adapted to travel on said track, train-carried equipment including a receiver capable of receiving and demodulating a carrier telephone current, a train-carried circuit associated with said receiver and including an inductor in inductive relation with the traflic rails, a wayside station, station equip ment including a transmitter capable of supplying a carrier telephone current, a line wire extending along the railway and disposed for distributed capacity to ground and distributed mutual electromagnetic induction to the rails, and a line transformer having one winding interposed in said line wire and another winding connected with said transmitter to cause carrier telephone current to flow in the line wire by virtue of the distributed capacity between the line wire and ground for establishing communication between the wayside station and the train by virtue of the distributed mutual electromagnetic induction between the line wire and the traflic rails.

26. A railway communicating system including a railway track, a line wire extending along the railway and disposed to one side of the traffic rails for distributed capacity to the ground and distributed mutual induction to the rails, a train adapted to travel on said track, train-carried communication equipment including a transmitter and a circuit coupled to the traffic rails, said equipment operative to cause communication current to flow in the rails in multiple in both directions from the train which current is efiective to induce an electro-motive force in the line wire by virtue of the mutual induction of the rails to the line wire, said electromotive force efiective to cause communication current to flow in the line wire by virtue of the distributed capacity between the line wire and ground,

and another communication equipment including a receiver responsive to the communication current and a Winding disposed in inductive relation to the line wire.

27. A railway communicating system including a railway track, a line wire extending along the railway and disposed to one side of the traflic rails for distributed mutual induction to the rails, a plurality of circuit means one at each of selected points along the railway to connect the line wire with ground and each including a condenser, a train adapted to travel on said track, train-carried communication equipment including a transmitter and a circuit coupled with the trafiic rails, said equipment operative to cause communication current to flow in the rails in multiple in both directions from the train which current is effective to induce an electromotive force in the line wire by virtue of the mutual induction of the rails to the line wire, said electromotive force effective to cause communication current to flow in the channel formed by the line wire and said circuit means, and another communication equipment including a receiver responsive to the communication current and a winding disposed in inductive relation to the line wire.

28. A railway communication system including, a railway track, a line wire extending along the railway and so disposed with respect to the two traffic rails and with the ground that electromotive forces induced in the line wire in response to a communication current which flows in the rails in multiple are additive and cause current to flow in the'line wire in both directions from the point of induction and return through the ground, a train adapted to travel on said track, train-carried communication equipment including a transmitter and a circuit coupled with the trafiic rails, said equipment operative to cause communication current to flow in the rails in multiple to induce current in the line wire by virtue of the mutual induction of the rails to the line wire and which line current flows in the line wire and the distributed capacity between the line wire and ground, and another communication equipment including a receiver responsive to the communication current and a winding disposed in inductive relation to the line wire.

PAUL N. BOSSART.

CERTIFICATE OF oonize'criom Patent No. 2,064,640. December 15, 1936.

PAUL N. BOSSAR'I'.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 9, first column, line 4647, claim 12, for the word. "indication" read induction; 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 2nd day of March, A. D. 1937.

Henry Van Arsdale l) Acting Commissioner of Patents.

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