US1577107A - Radiophone system - Google Patents

Description

March 16 1926. 1,577,107

= E. E. CLEMENT RADIOPHONE SYSTEM Original Filed 1 6, 2 5 Sheets-Sheet 1 E. E. CLEMENT RADIOPHONE SYSTEM March 16 1926.

Original Filed Q 25, 1924 5 Sheets-Sheet mm mm fiavargtor,

March 16 1926.

E. E. CLEMENT RADIOPHONE SYSTEM Original Filed Sept. 26, 1924 5 Sheets-Sheet 5 March 16 ,1926. 1,577,107

.- E. E. CLEMENT RADIOPHONE SYSTEM E g lmvmm rmw 2 5 E? March 16 1926.

Original Filed Sept. 26, 1924 E. E. CLEMENT RADIOPHONE SYSTEM 5 Sheets-Sheet '5 Patented Mar. 16, 1926.

UNITED STATES PATENT OFFICE.

EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO EDWARD F. COLLADAY, OF WASHINGTON, DISTRICT OF COLUMBIA.

RADIOPHONE SYSTEM.

Application 'filed September 26,1924, Serial No. 740,113. Renewed February 11, 1926.

To all whom it may concern:

Be it known that I, EDWARD E. CLEMENT, a citizen of the UnitedStates, residing at Washington, in the District of Columbia,

v have invented certain new and useful Improvements. 1n Radlophone Systems, of

which the following is a specification, reference being had therein to the accompanying drawing. V

My invention relates to systems of communication, and particularly to telephone and radio systems. Thepresent application is a continuation in part of my copending application, Serial No. 581,829, filed August 14, 1922, now Patent No. 1,522,357, dated Jan. 6, 1925, the present invention having for its main object the provision of centralizcd maintenance and control through the centralization of the source of power or onergizing current for the service units. Another object is to provide a system of distribution for such centralized current supply' which may be phanto'med on the telephone wires without interfering with their normal functions.- Ayfurther object is to provide means for extending the centralized power supply system to sub-centers such as private branch exchange systems. Other objects of my invention will be apparent from a perusal of the following specification and the drawings accompanying the same.

My invention is illustrated in the accompanying drawings, in which:

Fig. 1 is a diagram showing a geueral systcm en'ibodying the same;

Fig. 2 is a diagram showing a central station telephone switchboard, subscribers lines terminating thereon, and subscribers telephones connected thereto;

Fig. 2 shows a n'iodil'ication of the system of Figs. 2 and 3;

Fig. 3 is a diagram to be read in connection with Fig.2, showing the radiophone set at one of the subscribers stations, and the radio switchboard and associated equipment at the central station.

Fig. 4: is a diagram showing a simplified arrangement for controlling and charging the battery of a substation radiophone set over a phantom circuit imposed on a mag-' neto telephone circuit.

Fig. 5 is a schematic diagram of a private branch exchange system with-radiophone receivers at the subscribers station supplied tem of Fig. 6 with local generation at the private branch exchange station taking power supply over the phantom circuit.

Referring to Fig. 1, l, 2 and 3 represent telephone subscribers stations connected by wires 4, 5 and 6 to the central telephone exchange 7, constituting the distributing center for the area in which local subscribers 1, 2, 3, etc., are located. Super-posed upon this telephone system is a radiophone system comprising a central station 8 and subscribers stations 1", 2", 3", etc. The central radio station or exchange is provided with switchboards and a complete broadcasting equipment, and the subscribers stations 1*, 2 3

etc., are provided with receiving instruments rad-iophone system is by means of physical' connections indicated at 1", 2", and 3' at the subscribers stations. and multiples or trunk extensions 15 from the telephone exchange switchboards to the radiophone ex change switchboard in station No. S. The detail of these connections will appear hereinafter, but it should be stated here that the system of connections is such that telephone wired trafiic has the right of way over the wires, while the radio traflic has the right of way over the radio side of the system. The arrangement is such that the radio operator cannot interfere with telephone operation, nor can. a telephone operator interfere with the radio operation, although under proper conditions each can act freely by' way of borrowing facilities from the other. At all times, should a question of precedence arise. the apparatus is arranged so as automatically to cut off the radio connections and tr leave the wired lines clear for telephonic use.

Stations 12, 13 and 14 in this figure are typical of indilferently located distant sta tions which may or may not be a part of this particular system. As the figure is typical only, no attempt has been made to give the geographical location of such sta' 'tions or to show the actual arrangement and distribution of the telephone centers through which final broadcasting to the subscribers must take place. The main purpose of this figure is to crystallize the method employed, by which the development of a very large number of unrelated individual receiving stations is replaced by an orderly system of distribution through the telephone centers, whereby the individual receiving instruments are localized, maintained, controlled, and supplied with definite service through regular channels, for which a definite charge can be made and collected in the manner usual in wired systems of communication. Inasmuch as the number of wave lengths available for transmission is limited in the present state of the art, advantage is taken of the organized system of wire distribution and localization to create a phantom system controlled and guided thereby.

Briefly stated, as indicated in Fig. 1, each radio central station or radio department of a telephone exchange, is not only provided with broadcasting equipment for its subscribers, but also with radio receivers adjustable by tuning to wave lengths allotted to such stations as those indicated at 12, 13' and 14, as well as primary stations maintained and operated by or under the direction of the telephone organization itself. By means understood in the art, messages received at the radio central stations are relayed on their respective standard wave lengths to the local subscribers.

Referring to Figs. 2 and 3, I have therein shown circuits of the central oliice and substation equipments and connections, Fig. 2 representing the telephone side of the system, and Fig. 3 the radiophone side of the system. Before proceeding to detail description it may be noted that in accordance with standard telephone practice, provision is made for keeping the telephone lines and central ollicc circuits clear of all grounds or other disturbing connections during conversation. hen the radiophone goes into service, by closing the filament. switch its operation in receiving is identical with that of any radio receiver, and in the event that use is made of any partial transmission of waves over the line wires, as will be herein- ,after pointed out, said waves will be at a frequency above or below the limits of audition. In the present diagram, l have shown the circuits arranged with nothing but continuous current for radio purposes over the telephone line wires. This is the simplest form of control and the one nearest to present-day telephone practice, and is absolutely certain not to produce any disturbance in adjacent conductors in the telephone cables. Each radiophone set is provided with a cut off relay energized when the telephone set goes into commission, either by calling or being called, and at the central office whenever the rado operator takes control of the line, he disables it in the usual manner by pulling up the cut off relay at the telephone switchboard, this however being subject to the condition that a special tone test may be put on, so that all operators may know that the line is held on the radio board, and subject to interruption for telephone connection. I prefer to use this tone test only with the radio operators testing plug, because his regnlar connecting plug includes within its functions that of connecting a subscriber through the station amplifier to the broadcasting transmitting set, and a connection of this character should not be inter rupted without permission.

Referring now to the diagrams, Fig. 2, A and A are two subscribers stations conneeted by line wires 16-17 and 1819 respectively to the central station C Where they terminate on jacks J and J. P-P are plugs forming the terminals of a cord circuit 2()-21, 22 23, having a bridged repeating coil 1, ringing and listening keys K and K, supervisory signals s-s and bridging connection to the main battery B. The same battery is shown supplying current to the line relays L, L and through contacts at the cut oil relays L L to the-respective lines for calling purposes. In this system, when a subscriber takes down his receiver, the line relay lights its lamp, which is extinguishcd when the operator inserts the answering plug. Battery supply for the connected lines is thereafter taken through the cord circuit 20-422, 21-423, in a manner well understood in the art. When the substation telephones are out of service, with their receivers hanging on their books, the telephone circuits are conductively open for direct current, leaving the ringers Q, and Q, in circuit for alternating ringing current passing through the condensers rg.

Referring now to Fig. 3. it will be observed that the radio switchboard which I have designated generally by the letter R, is connected to the subscribers lines by multiple taps marked fil 17, and i7", and '18, 19, 19 These terminate on multiple jacks J d, corresponding to the multiple jacks on the telephone switrhlmard. it should be noted that throughout this system the tip wires 16 and 155 with their branches are connected to ground. while the sleeve wires 17 and 19 and their branches. are connected to battery. This isextended into the radio side of the system for the purpose of securing proper balance lxelwcen the main battery or power plant of that side and the main battery or power plant of the telephone side of the system.

At the subscribers stations taps are also taken oft from the telephone terminals to the radiophone terminals as indicated at 18, 19, and 19. (The radiophone is shown only at one substation for sake of simplicity of illustration). The two branches 19 and 19 are taken from the sleeve or battery side of the line 19, and are connected to opposite terminals of the winding of a relay L, which constitutes the substation cut off relay for the radiophone. The winding of this relay is bridged by a condenser 9 through which both ringing and voice currents can pass without substantial impedance. Where the radiophone is attached to a party line substation, this relay L may be omitted, since on such party lines there are usually grounds on one side or the other. As will presently appear, the radio circuits described herein are applicable to two-party or fourparty lines, with individual metering of the party stations.

Normally, that is to say, when the telephone circuit is not in use, the cut off relay L is deenergized and as a consequence the line wires 18 and 19 are connected through the back contacts of the relay through switches 24 and 25 to the extreme terminals of the high impedance phantom coil 26, the middle terminal of which is connected through conductor 27 to the negative ter;- minal of the A battery marked A in Fig. 3, the lus terminal of which is grounded locally as shown. For completing the phantom charging circuit, the phantom coil 26 is matched by one side of the repeating coil of the operators test cord circuit TC of Fig. 3 which coil has a central tap 170 to the negative terminal of the charging battery A the positive terminal of which is grounded locally.

The radioplione receiver at the substation A is shown as comprising an antenna 28, tuned coupler 29, detector tube 30, audio amplifier tubes 31 and 32, and the usual trans-formers 3 3, 34-, 35, the last mentioned transmitting the amplified audio waves to the telephone receiver or loud speaker 36. The filament battery is.A The plate battery is B and suitable tuning condensers and coils, tickler coil for regenerative effects, etc., are provided as required. I should remark in passing that this representation of the radio receiver is intended to be typical only. The present invention does not concern itself specifically with the design of the local radiophone sets, and other circuits and appa 'atus may be substituted for those shown in the diagrams without departure from the invention.

- The-pair of contacts 27, 27 close the 3.9-. and 40, f0rming terminals of the induction coil circuitv I", to the to energize his talking circuit.

tip and sleeve side of the telephone line respectively, through the back contacts. of relay L The transmitter T is shown hanging upon a hook switch H controlling the connection of wires 41 and 42, constituting a parallel link between the battery A and the filament bus 43. Thus the filament can be heated and the radiophone put in service.

In, addition to the hook, the subscriber has a manual switch it by which hecan connect the battery 'wire 42 through a wire 44 to his transmitter T, coil I and ground, so as I provide an ordinary'telephone receiver-t in series with the secondary of the induction coil I, and I interpose a pair of condensers 9 9 between the secondary of the induction coil I and the receiver t on the one hand, and the conductors 39 and 40 on the other, so that while the subscriber bymeans of switch 71, can connect his phone T t for receiving calls over the telephone line, he cannot originate calls thereover from the radiophone extension.

Returning now to the central station, and particularly to the radio department thereof shown in F ig. 3, T represents a broad casting transmitter, symbolized in very simple form, but supposed to contain the usual elements of power supply, modulator, oscillator and aerial, with suitable amplification of the audio waves supplied on the input side. The jack J connected to the amplifier t and thence to the transmitter'T, symbolizes a group of such jacks or equivalent connecting means such as automatic switches, controlled by dials or keys for con necting any of the wire lines to said radio transmitten, Detailed appliances, both for the switching and for the radio transmission, are well known in the art, and" need no specific description in this specification, my present invention having to 'do particularly with the method of transmitting by wave radiation to the substations, and ot bringing in all conversation originating or received at the substation radiopho'ne over the subscribers wire line. Thisincludes repetition of modulated radio waves received at the radiophone substation and also originating messages gathered up and to be putthrough the amplifier t on the transmitter T for broadcasting.

It may he explained here that the transmitter T for general purposes is assumed to be the standard wavelength transmitter for the local exchange area, to which all of the substations are tuned and upon which they depend both for original messages a'nd programs and for those received and relayed from a distance.

The cord circuit between plugs P and P in Fig. 3 is the same as the operators cord circu t in. Flg. 2, but the 'adio operator also has special test cords such as that shown m the Ilt upper part of the figure connected to plug 1 Here the keys KK are of standard construction, as in the other cords, and the test contact of the plug I is connected through suitable resistance to the supervisory lamp .9 to the radio battery A, means such as the conunutator 1) being provided to give special tone test on the test thimbles of the multiple jacks J J, etc. It will be noted that when this plug P is inserted in a subscribefis radio jacl; J, a phantom charging circuit. is completed between the central otiice radio battery A and the subseribers radio A battery A which circuit may he traced from the plus or grounded side of the battery A through ground to the grounded plus terminal of the subscribers battery A through A to conductor 27, phantom coil 26, both sides of subscribers line by way of contacts Q-t---Q5, contacts of relay 1), line branch conductors 191S, into Fig. 2, line conductors 19-478, radio multiples 19-1S into Fig. 3, through jack J and plug J and thence through windings 91 and 92 of the repeatting coil 90, conductor 17 to minus t-ern'iinal o'l' battery A Two important advantages arising); from this method of supplying current to the suhscribefis radiophoue set, are that the use of the line for the transmission of voice currents is not interfered with by the closure oi the charging circuit, and that the current capacity of the line is doubled to! the charging circuit,

The radio operators testing and charging plug: TC is also provided with a testing instrument in the form of a voltmeter V adapted to be connected through av switch. S to the ringing, ltey K in place of the ringinc generator G, the circuit: connections hein; such that one terminal of: the voltmeter will be connected to both sides of the line while the other terminal oi the voltmeter is grounded. Thus, as. one terminal of the subscribers A battery is connected to both sides of the line and the other terminal grounded, the voltmeter reading will in'di' cate the condition of the subscribers battery. Tt is to be understood that the voltmeter V is typical of any testing instrument which it may be desirable to use. The operator's listening, set LS, which may be common to several cord circuits such as TC is provided with outgoing and incoming order trunks G and 1C, whch lead to the listening set associated with the cord circuit (l of the telephone operator, the trunk 0G being normally opened or disconnected from the radio operators listening set at the contacts OS, while the trunk IC is normally disconnected from the telephone opcratofs listening set at the contacts TS.

In operation, when the radio operator's phi; TC is in a subscribefis jack. for ex ample jack J the subscribers battery A will be charged from the central battery A over the phantom circuit above described, and the cut-ott relay L (Fig. 2) at the telephoneccntral switchboard will be held energized through the test contact 171 of the cord circuit TC, which energizing circuit may be traced from the central otlice battery 15, through supervisory lamp and its shunt through contact of supervisory relay 172 to test contact 171 and thence through test contact N2 of jack J test conductor 19" into Fig. 2. cut-oil relay L to ground and back to thc'groundcd Side of the battery B. This disconnects the line signaling apparatus at the telephone switchboard to prevent false signals due to the use of the line by the radio operator. Should the subscriber at A desire to call the telephone operator for the purpose of establishing telephonic comnnmichtion with another subscriber, while the line is held by the radio operator throujg li the cord circuit TC, the subscriber rapidly opens and closes the tip side of his line by actuating" the switch 27 Each time the tip side of the line is thus opened the tip supervisory relay 172 is deenergrized, opening the shunts around the supervisory lamp and causing, the lamp to liash. This flashing of the lamp calls the operator using the cord circuit TC who, listcning in by means of the listening key K and the listening set LS, may ascertain the wants of the subscriber and either pull the plug l to give thesubscriber control of the telephone switchboard line signal or close the. contacts ()S and communicate over the outgoing order trunk 0G with the telephone operator at the cord circuit 0 who will take the ordcr aml establish the connection. In emergency telephone connection can also be made through cord TC direct. v closing the contacts 173, 2T, QT, and switch it, the subscriber may coliVtiFe from his radiophone set, through the transmitter T and telephone rcocivcr t. The energizing circuit of the transmitter 'l" may be traced from battery A through wire 41-2, and contacts of switch 71/, ll. T, I, and through ground back to battery A while the connection of the transmitter across the subscribcfls line may be traced from line wire 18. through line branch 18", contact of relay L, contact 27, 40. o, 1 t, 9", 39, 27, contact ot' relay L", line branch 19 to line wire 19.

Should the telephoneoperatordesire to connect with the subscriber A while. the line cut-oil relay is held up by the connection (it the radio plug TC with the sub scribcrs radio multiple jack J. the operator upon touching the ring or test contact oi" the multiple jack J with the tip of the cord P, instead of receiving the usual click in the rcccirer of her listening, set, will receive a characteristic busy test due to the ti )les 1819 the o)erator may rin )ast the phantom coil through the ringing condenser Q2. The subscriber A upon raising his receiver from the switchhook in response to the call will bridge his transmitter circuit across the line in the usual manner which will close his line circuit through the cut-off relay L which upon cnergization will open its contacts and disconnect the line extensions 1819 from thesubscribers radiophone set. Thus, during use of the telephone line for telephone purposes, from the subscribers main telephone set, the radiophone set will be disconnected therefrom. As an alternative arrangement, contact L on the telephone switchhook, as shown in Fig. 2* can be substituted for relay L. 3

When the radio operator is notconnected with the subscribers line through plug TC and the subscriber A wishes to establish connection with the radio operator, he signals the telephone operator by actuating the switch 174 to rapidly close and open the line which rapidly energizes and deenergizes his line relay L and causes the line lamp Z- to flash. This flashing of the line lamp in stead of a steady lighting distinguishes the call for radio service from the usual call for telephone service so that the telephone operator may apprise the radio operator of the subscribers wants over the order trunk IO without having to communicate with the calling subscriber.

In Fig. 4 is shown an arrangement for supplying current over a grounded phantom on a. magneto telephone line circuit to a radiophone receiver at the subscribers station. Iii-this instance the problem is simplified due to the absence of a line and a cut ofi relay at the central office. In this arrangement RP represents the amplifier portion of the subscribers radiophonewhich may be of any known or other suitable type having a pair of filament battery bus wires 175 and 176 connected respectively to the minus and plus terminals of a local A battery A", the plus terminals being arranged to be out of connection with the wire 176 through switch 177. The plus terminal of the battery A is also connected to ground through one contact of the gang switch 178 while the minus terminal is connected through the other contact of the switch 178 and conductor 179 to the middle terminal of the phantom coil 180 bridged across the telephone line 181182. This coil is matched by a similar coil 183 similarly connected at the central oflicc station C to the line and to the minus terminal of the battery A the connection with the battery being made through conductor. 184, switch plug 185, conductor 186, charging bus 187 and choke coil 188. The plus pole of the battery A is grounded at the central station.

When it is desired to charge the subscribers battery A, the gang switch 178 and the plug switch 185 are closed completing the phantom charging circuit which may be traced from the plus or grounded side of battery A through ground to the subscribefsestation, through contact of switch 178, battery A conductor 189, contact of switch 178, conductor 179 to middle of coil 180 and thence over both sides of line 181182v through coil 183, conductors 184, 185, 186, 187 and 188, back to battery A. By operation of the switch 177, the sub scriber may connect his radiophone set in a local circuit with the battery A independently of the condition of the charging Circuit.

In Fig. 5 I show an arrangement in which the 'idea of supplying battery to the radiophone subscribers is applied to private branch exchange systems, in which certain of the trunks T T, T and T leading from the main exchange M to the PBX station are phantomed with a charging circuit or circuits for storage batteries such as A and B which act as a common source of current supply for the radiophones RP RP, etc., associated respectively with the private bran'ch' exchange, subscribers telephone sets T, T etc. The batteries A and B are the A and B batteries, respectively, for the subscribers radiophone sets and are connected to the sets through the three bus wires 191, 192 and 193. These batteries A and B are arranged to be charged from the central oiiice batteries A and B, respectively, over separate phantom circuits, or they may be alternately connected for charging to a single phantom circuit.

A more detailed circuit diagram of-the arrangement for charging the private branch exchange batteries each over a separate coil 196, and in the PBX station at the outside terminals of the winding 197 of a repoating coil 198. The winding 199 of the repeating coil 196 is connected through a cut-oil jack 200 to a drop signal 201 at the main telephone station, while at the PBX station the coil 202 is similarly connected to a cut-cit jack 203 to the drop signal 204. To facilitate the passage of voice current through the trunlr from jack to jack, the repeating coils are bridged by telephone condensers 205 in the usual manner. At the main exchange the trunk side 195 of the repeating coil 196 is tapped at the middle and connected through a conductor 206 and switch 207 to the plus terminal of the charging battery A the minus terminal of which battery is grounded at the main exchange. Similarly a conductor 208 connects the middle of the trunk side of the repeating coil at the PBX station through a switch 209 to the plus terminal of the battery A the minus terminal of which battery is grounded at the PBX station. The trunk T and its terminal apparatus is the same as the trunk T and has phantomed on it a charging circuit for the battery B which circuit is connec ed to the battery at the PBX station by way of the conductor 210 leading through switch 211 and conductor 212 to the plus terminal of the battery B the minus terminal of which is grounded as shown. At the main station M the phantom circuit is connected with the charging battery B by the conductor 213 which leads from the middle point of the trunk side of the repeat ing coil through the switch 214 to the plus side of the battery B, the minus side of which is grounded. Thus, the batteries A and B are connected to separate charging batteries A and B, respectively, at the main station over separate grounded phantom circuits, one on the trunk T and one on the trunk T. The primary sources A and B at the main exchange are of sufficient voltage to aifect proper charging of their respective secondary batteries A" and B The common- battery supply basses 191, 192 and 193 are the same as thoseof Fig. 5, and so are multipled to the battery consuming elements in the radio receivers. For example, where a detector tube or single tube set is used as indicated in Fig. 6, the filament and supply leads 216 and 217 are connected to the busses 191-192, respectively, while the plate circuit conductor 218 is connected to the bus 193, the plate circuit return being effected through the filament lead 217 to the middle or common bus 192 as is usual where a local set of batteries is used. To keep radio frequency currents off the busses 192 and 193 a radio frequency by-pass condenser 219 is connected as shown.

Vhere only one charging circuit is available the circuit arrangement of Fig. 7 may be used in which is shown the single phair tomed circuit imposed on the trunk T arranged to be switched in circuit with the battery A and generator A, or the battery 15 and generator B according to which battery is to be charged. In this arrangement the plate battery 1) is shown tapped at an intermediate point to supply detector voltage to the. bus 193, while the fourth bus 220 is led from the extreme positive tcrininal for supplying plate voltage whcrc amplilier tubes are used.

Fig. 8 shows a furthc' arrangement for supplying current from the main station in which the primary energy is supplied over the trunk line T in the form of alternating current of superaudio frequency which may or may not be modulated with audio signals but which is transformed into the proper form of energy for charging the secondary batteries A and B through a suitable high frequency motor 221 and a pair of generators 222 and 222 driven thereby.

'In Fig. 9 is shown a further modification of the idea of charging over a phantom circuit in which the batteries are charged by a pair of local generators 224 and 225 driven by a motor 226 supplied with power over the phantom circuit from a source 227 at the main station.

I do not claim herein the arrangement of bus circuits and supply from central, as shown in Fig. 5 nor the charging of batteries of the branch exchange to supply individual subscribers, nor the arrangement of generators and batteries shown in Figs. 7, 8, and 9, these features being claimed in my copending application, Serial No. 89,409, filed February 19, 1926, as a division hereof.

\Vhat I claim is:

1. In a broadcasting system, a main station, a plurality of substations, means at said main station for generating and transmitting to the substations radio waves means at the substations for receiving said waves, metallic wire circuits from the main station to the substations, phantom circuits imposed upon said wire circuits, and a centralized source of current supply for the substation receiving means, connected to said phantom circu ts and distributed thereby to the several substations.

2. In a broadcasting system, a main station, a branch station, a plurality of wired trunk lines from the main station to the branch station, a. plurality of subscribers substations, means at the main station for generating and transmitting radio waves, means at the substations for receiving said waves, individual wire circuits and common multiple connections from the branch station to the substations, a phantom circuit imposed on one of said trunk circuits, and a centralized source of current supply for the substation receiving means distributed to the several substations over said phantom circuit. and said multiple connections.

3. In a' broadcasting,system, a main station, a lnanchstation, a plurality of wired trunk lines from the main station to the branch station, a plurality of subscribers substations, means at the main station for generating and transmitting radio waves, means at the substations for receiving said waves, individual wire circuits and common 'trunk lines from the main station to the branch station, a plurality of subscribers stat-ions, means at the main station tor generating and transmitting radio Waves, means .at the substations for receiving said waves,

individual wire circuits and common multiple connections fronrthe branch station to the substations, a phantom circuit imposed on :one of said trunk circuits, a storage battery at the branch station connected to the said common multiple connections for supplying current thereover to the several substation receiving means, and a centralized source of charging current connected with said storage battery over said phantom circuit, together with means associated with the substation receiving means for com nnmicating with said branch and main stations over said individual wires and said trunks.

5. In a broadcasting system, a main station, a branch station, a plurality of wired trunk lines from the main station to the branch station, a plurality of subscribers stations, means at the main station for generating and transmitting radio waves, means at the-substations for receiving said waves,

individual wire circuits and common multiple connections from the branch station to' generating and transmitting radio waves,

means at the substations for receiving said waves, individual line wire circuits from the main cXchange to the substations, telephone link circuits at the main exchange for interconnecting said wire circuits for telephone purposes, a supervisory signal for each link circuit, a current supply circuit for the substation radio receiving means connected in a grounded phantom circuit imposed on the line circuit, grounded phantom current supply circuits arranged to be connected with one-of the individual lines for supplying current to said substation current supply circuits over a grounded phantom circuit coinpletcd through the line upon connection of the supply circuit, a supervisory signal for each supply circuit, and means at the substations for selectively actuating said supervisory signals.

7. In a combined telephone exchange sys tem and radio broadcast receiving system, a plurality of subscribers substations, radio receiving means at said substations, individual wires connecting said substations with the telephone exchange station, connecting links at the telephone exchange station for interconnecting said line circuits for telephonic purposes, means for supplying current to the said substation receiving means over phantom circuits imposed on said individual wire circuits, link supervisory signals associated with said link circuits, sup ply supervisory signals associated with said phantomsupply circuits, and means associated with said substation receiving means for selectively actuating said supervisory signals.

8. In a combined telephone and radiophone system comprising a plurality of telephone substations, a' telephone central station, line Wires interconnecting them, a plurality of radiophone substations, a radiophone central station, means to transmit messages from said radiophone central station to its substations by modulated high frequency waves, means at the radiophone substations to transmit messages telephonically, wire connections between the radiophone substations and telephone substations, wire connections between the radiophone central station and the telephone central station, phantom circuits connegting said radiophone central station with said substations superimposed upon said wire connections, supervisory signals at said telephone central station, supervisory signals at said radiophone central station, and means at saidradiophone substations for actuating said supervisory signals at either said radiophone central station or telephone central station, selectively.

In testnnony whereof I hereunto atlix my signature.

EDWARD E. CLEMENT.

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