US1772168A

US1772168A - Multiplex broadcasting system

Info

Publication number: US1772168A
Application number: US187273A
Authority: US
Inventors: Edmund R Taylor; Oscar B Hanson
Original assignee: American Telephone and Telegraph Co Inc
Current assignee: AT&T Corp
Priority date: 1927-04-28
Filing date: 1927-04-28
Publication date: 1930-08-05
Anticipated expiration: 1947-08-05

Description

Mf /s Au 5 1930. E, R. TAYLOR ET AL 1,772,168

NULTIPLEX BROADCASTING SYSTEM Filed April 28. 1927 2 Sheets-Sheet 1 v mmvrons EB]ZZ 101w? BY QB mom 7 A TTORNEY Aug. 5, 1930. E. R. TAYLOR MULTIPLEX BROADCASTING SYSTEM Filed April 2a. 192'r 2 Sheets-Sheet 2 INVENTORS 5"" JYams-om E121 BY 0.

ATTORNEY Patented Aug. 5, 1930 UNITED STATES PATENT OFFICE EDMUND R. TAYLOR, OF NEW YORK, N. Y., AND OSCAR B. HANSON, OF ROSELLE, NEW

JERSEY, ASSIGNORS TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A COR- IPORATION OF NEW YORK MULTIPLEX BROADCASTING SYSTEM Application filed April 28,

This invention relates to multiplex broadcasting systems, and particularly to arrangements in such systems for interconnecting a plurality of sources of news, music or the like with a plurality of transmitting stations, so that the programs originating at said sources may be simultaneously broadcast by said transmitting stations.

There will be shown herein a system for operating a plurality of broadcasting studios in connection with a number of transmitting stations. A particular form of interconnecting system is described herein, merely for the sake of illustration, and is so arranged that any one of the studios may be connected to any one of the transmitting stations, two studios not being connected to any one transmitting station at the same time. This is accomplished in a manner such that the audiences of the various transmitting stations do not hear any of the switching noises and do not observe any, apprec,,iable delays between selections, or that any other program is being transmitted by any other transmitting 25 station except the one the audiences are scheduled to recelve.

It is one of the objects of this invention to provide in a multiplex broadcasting system interconnecting a plurality of transmitting stations through a control room, a telephone intercommunication circuit, so that the announcers in the various studios may be connected telephonically to the operator or operators in the control room. Accordingly, there will be shown herein a system whereby any announcer may speak to the control room operator associated with his studio, and vice versa.

It is another object of this invention to provide in a multiplex broadcasting system interconnecting a plurality of studios and a plurality of transmitting stations through a control room, a telephone interconnecting circuit, so that an operator at any one of the transmitting stations may be connected telephonically with the operator or operators at the control room and with the announcer or announcers at the various studios.

It is another object of this invention to provide a monitoring circuit or circuits in a radio 1927. Serial No. 187,273.

broadcasting system, so that anyone in a studio where program matter originates may monitor the program matter as it is being transmitted through the control room, or as it is being transmitted by the transmitting station. In the particular circuit to be described hereinafter, a person in any one of the studios may monitor the program matter transmitted from any one of the studios.

It is another object of this invention to provide in a multiplex broadcasting system interconnecting a plurality of studios with a plurality of transmitting stations through a control room, means to indicate to the announcers in the various studios that the apparatus and equipment at the control room are ready for the transmission of program matter through some or all of the various transmitting stations.

And it is a further object of this invention to provide signals at the various transmitting stations to indicate to the operators at said transmitting stations that program matter should be coming into their stations from the various studios.

While the nature of the invention will be pointed out with particularity in the appended claims, the invention itself, both as to its further objects and features, will be better understood from the detailed description hereinafter following when read in connection with the accompanying drawing, in which Figs. 1 and 2, when placed side by side, show one application of the rinciples of this invention to a multiplex roadcasting system.

Referring to the drawing, there is shown a multiplex broadcasting system interconnecting two studios A and B, and three transmitting stations comprising radio transmitters ST 8T and ST and corresponding radio antennae TA TA and TA,. These studios and transmitting stations are so interrelated that the programs originating at these studios may be simultaneously broadcast by the transmitting stations, the system being so interlocked that both studios may not be connected to any one transmitting station at the same time. Each studio has three control relays, one control relay corresponding to each transmitting station. At studio A, these control relays are designated by the reference characters R R and R and at studio B, these relays are designated by the reference characters R R and R Some of the apparatus for connecting one of the studios with a particular transmitting station is located at that studio, and the rest of the apparatus is located at the control room. Each studio has a program microphone or microphones and an announcers microphone or microphones. Moreover, a nemo circuit is connected to each studio so that the program from some distant pickup point may be brought into the studio in order to be transmitted through an appropriate transmitting station. Yet, it will be understood that while only one nemo circuit is shown connected to any one studio, any number of these nemo circuits may be connected to the studio, within the scope of this invention, apparatus being provided to switch the apparatus at the studio from one nemo circuit to another nemo circuit associated therewith. The program microphones MP and MP the announcers microphones MA and MA and the nemo circuits NC and NC correspond, respectively, to studios A and B. Switches K and K and K and K are also located at the respective studios, so that any one or more of the transmitting stations may be transferred by these switches to one or the other of the studio microphones or to the microphones at some distant pick-up points connected to the corresponding nemo circuits. Studios A and B terminate in studio bus-bars Sb and S6 respectively. The transmittin stations are connected through line ampli ers LA LA and LA to corresponding channel busbars CB CB and CB respectively.

For the sake of convenience, the course of transmission from one of the studios, studio A, to one of the transmitting stations, such as the station associated with the channel bus-bar CB will now be considered in somewhat greater detail. At studio A, there is a microphone control panel CP which adjoins the program microphone MP and the announcers microphone MA Suitable means (not shown) is associated with the microphone control panel GP for feeding current from a battery (not shown) to either or both of these microphones, and still other means (not shown) is provided for observing the magnitude of the current flowing from the battery through the particular microhone connected to the control panel (3P t will be understood that these microphones may be of any well-known, type, as, for example, of the type known as the carbon transmitting microphone, or of the type known as the condenser microphone, with the amplifier usually associated therewith.

It is to be remembered that the equipment at studio B is shown herein similar to the equipment at studio A, and that the descrip tion of the equipment at studio A' applies equally well to the description of the equipment at studio B.

The circuits connected to the microphone control panel CP have become known as the program and announcers circuits. These circuits are connected, respectively, to the lower contacts 9' and is of the switches K and K A nemo circuit N0 is connected to the contacts a and b of the switch K Switches K and K are so arranged as to connect the program microphone MP the announcers microphone MA or the nemo circuit NC with the input of the amplifier CA at the control room.

Three lamps L L and L at studio A are also controlled by the switches K and K and indicate to the announcer whether switches K and K have been operated to connect the program microphone MP the announcers microphone MA or the nemo circuit NC with the amplifier CA These connections will be described in somewhat greater detail hereinafter.

The main transmission path may be followed from the contacts 6 and f of the switch K through the amplifier CA at the control room, which is terminated in a suitable impedance PT through the inner contacts b and c of the main relay R to the studio bus-bar S5,. The main relay R functions to open the circuit between studio A and the corresponding bus-bar $6 at times when it is considered undesirable to transmit the program matter originating in studio A. A volume indicator LL is bridged across the main transmission path between the amplifier CA and the terminating impedance PT both at the control room, to indicate the transmission volume or level after amplification. The magnitude of the terminating impedance PT mentioned hereinabove, is low as compared to the magnitude of the impedance in the inputs of the line amplifiers LA LA and LAg, so that when one of the amplifiers, such as LA is connected to the studio bus-bar Sb the other amplifiers LA and LA either or both of them, may be also connected thereto or disconnected therefrom without appreciably affecting the amount of energy transmitted by the amplifier LA This is so because most of the energy transmitted by the amplifier CA is expended in the terminating impedance PT which is of a small magnitude, and because very little of the energy is expended in the input of each line amplifier.

n order to minimize the possibility of crosstalk between studio bus-bars or channel busbars when the studio bus-bar Sb is disconnected from the amplifier CA a contact is closed by armature d of the main relay R thereby short-circuiting the studio busbar SL so that when the main relay R is not energized, the line relays LE LE and LR similarly become short-circuit-ed, so that program matter can not be transmitted to these line relays. Accordingly, any voltages which may be induced in these circuits are prevented from being impressed upon the input of the line amplifiers LA LA and LA and are further prevented from being amplified, all of which would cause objectionable cross-talk or interference. The operation of the line relays LE LR and LR will be described in somewhat greater detail hereinafter.

13 The system is so laid out that either of the studios may be connected with one or more transmitting stations simultaneously, and, moreover, so that any transmitting station may be connected to any studio. The interlocking arrangement shown herein prevents any one transmitting station from being connected to both studios at the same time. This is essential to prevent confusion between programs. The omission of an interlocking arrangement would permit the tying together of two or more studio bus-bars in the corresponding studios to the same transmitting station. The line relays LE LE and LR and LR- LR, and LE associated with the studios A and B, respectively, are

so arranged as to prevent any one transmitting station from being connected to both studios at the same time. Failure of operation, or improper operation of these line relays LR, and LR, would permit the transmitting station associated with the channel bus-bar CB to become connected to studios A and B simultaneously. Improper operation of the other line relays will produce similar undesirable effects.

The studios and the control room are provided with signaling devices to keep the announcers at the studios and the operator or operators at the control room continuously advised of the manner in which the studios are connected with the various transmitting stations. Means are provided to permit the announcer at either studio to connect his studio to one or more of the transmitting stations. After his studio has been connected to these transmitting stations, the system is arranged so that the other studio can not be connected to the same transmitting stations at the same time. Thus, the announcer at any studio has at his disposal apparatus for picking up and for releasing the various transmitting stations, and he has also various signaling devices which keep him continuously advised as to whether or not the various transmitting stations are already connected to his studio or to the other studio. A description of the apparatus mentioned hereinabove will be described in somewhat greater detail hereinafter.

In studio A, keys K although shown as permanent keys, may be K,,, which are momentary contact keys and control the operation of relay R By closing key K relay R becomes energized by the flow of current through the winding of that relay from a battery B the circuit including the armature of the relay IR conductor 21, key K the winding of relay R key K key K conductor 22, key K and ground. As the winding of the relay R becomes energized, its armature A closes a contact 0, enabling the Winding of the relay R to receive current from a battery B at the same time that current is flowing through the winding of that relay from abattery B The circuit from battery B includes key K conductor 23, key K the armature A and the contact 0 of the relay R the winding of the relay R key K key K conductor 22, key K and ground. After contact 0 of the relay R has been closed by armature A of that relay, relay R remains energized even after key K is released. Shortly after contact 0 of the relay R is closed by armature A, another contact (1 is closed by armature A. Current then flows from the battery B through the windin g of the relay IR this circuit including the battery E the key K conductor 23, the key K armature A of the relay R contacts 0 and (Z of the relay R conductor 24, the wind ing of the relay IE and ground. Thus, as the armature A of the relay R closes its contact (Z, the relay 1R becomes energized to enable its armature to open the contact associated therewith, thereby disconnecting battery 13 from the winding of the relay R Yet, the winding of the relay It, remains energized by the flow of current from the battery B through the circuit including the key K conductor 23, key K armature A and contact a of the relay R the winding of the relay R key K key K conductor 22, key K and ground. However, current may flow through the key K at studio B only when the relay 1R is deenergized. After relay R, has operated to close contact d, and after relay IR has become energized, the relay R at studio B can not become operated by key K, at that studio until the relay 1R has first become deenergized.

The winding of the line relay LR is in parallel relationship with the winding of the relay R conductor 25 connecting these windings. Consequently, the energization or deenergization of the relay R causes a corresponding action of the line relay LR The armatures a and b of the line relay LR are connected through the channel bus-bar CB to the line amplifier LA the radio transmitter ST} and the transmitting antenna TA Therefore, when the line relay LR and the relay R become energized, the main transmission circuit between the studio A and the transmitting station associated with the bus-bar CB becomes closed. Also, the

lamp L at the studio indicates to the announcer that the relay R, has operated. Similarly, the lamp L at the control room indicates to the operator thereat that the line relay LR has operated. The circuit of the lalnp L includes a battery B the lamp L the armature c of the line relay LR and ground. The relay R at studio A may be deenergized by operating key K key K or key K these keys all being included in a series path which includes the winding of the relay R Keys K and K are also in series with the windings of relays R and R at studio A, and hence are the studio and control room master release keys, respectively.

hen the apparatus in the control room is ready for the transmission of program matter to a given radio transmitting station, such as the one associated with the radio transmitter 8T the operator at the control room operates a key SK in order to signal the announcers in the studios that the apparatus is ready for the transmission of program matter. A feature of this invention lies in the provision of a link tying this signal with apparatus at the radio transmitting station in such a. manner that the signal can not be given unless the carrier wave, characteristic of that transmitting station is on the air. \Vhen the carrier frequency characteristic of the radio transmitter ST is being radiated by the radio antenna TA some of the energy radiated by the antenna TA is picked up by a coil Coupled to the antenna. The coil V is connected to a detector, shown herein as a vacuum tube detector, the coil bridging a condenser C and being connected between the grid and filament of the vacuum tube V A battery B is connected to the filament of the vacuum tube V through a resistance Z this filament being heated to an electron-emitting temperature by the current flowing from battery B The output circuit of the vacuum tube V includes a battery B the filament and plate of the vacuum tube V and the winding of a relay R \Vhen radio frequency energy, characteristic of the radio transmitter ST,, is picked up by the winding V the winding of the relay R will become energized due to the flow of current therethrough from battery 13 which is above a definite minimum value. Consequently, the armature of relay R will become attracted to close the circuit of another relay R at the control room, current flowing from a battery 13 through the winding of the relay R the armature and contact of the relay R and ground. When the winding of the relay R becomes energized, its armature is attracted to close a contact associated therewith, thereby grounding the armature. Similarly, relays R and E are associated with vacuum tubes V and V in the input circuits of which are coupling coil W, and

condenser C and coupling coil 'W and condenser C the windings W and W rendering relays R and R operative when currents characteristic of radio transmitters ST and 8T are being radiated by the transmitting antennae TA and TA respectively. Similarly, there are relays R and R at the control room, which become energized by the flow of current therethrough from batteries B and B when the armatures of the relays R and R are attracted, respectively,thereby grounding the armatures connected to these relays.

In order that the announcer at studio A may know which transmitting stations are prepared to receive and broadcast the program originating at his station, lamps L L and L are provided at that studio, each lamp being associated with one of the transmitting stations, these lamps corresponding to relays R R and R respectively. Lamps L L and L at studio A, and lamps L L and L, at studio B are controlled by the signal keys SK SK and SK respectively, which are located at the control room, and which are under the supervision and control of the operator at the control room. The system is so arranged that when one of the relays, such as R becomes operated, the lamp L, at studio B corresponding to the relay R at that. studio will become extinguished. Thus. the lamp L advises the announcer in studio A that the carrier wave of the transmitting station associated with the channel bus-bar CB is on the air and that the transmission path to that transmitting station is ready for broadcasting service from studio A. By operating one of the signal keys, such as SK a lamp L becomes illuminated, current flowing from the battery B, through the lamp Li the key SK the armature of the relay R and ground. The lamp L at the studio also becomes illuminated, regardless of the state of energization of the relay R as will be shown more clearly hereinafter. Vhen the winding of the relay R is deenergized, current flows from the battery B through the armature of the relay 1B,, the conductor 21, contact 7 and armature B of the relay R lamp L key SK the armature of the relay R, and ground. lVhen the winding of the relay R becomes energized, current then flows from the battery B,- through the key K conduct-or 2?), key K contact e and armature B of the relay R lamp L key SK the armature of the relay R and ground. Similarly, the lamp L in studio 13 becomes illuminated by closure of the key SK regardless of the state of energization of relay R current flowing through lamp L, from battery B when the relay R is deenergized, and current flowing from the battery B through the lamp L when the relay R becomes energized. Yet, when the winding of the relay R in studio A becomes energized, the corresponding lamp L in studio B becomes extinguished, while the lamp L in studio A remains illuminated. Thus, there is an indication to the announcer in studio B that the transmitting station connected to the channel bus-bar C13 is not available for the transmission of program matter originating at his studio. Obviously, when relay R at studio A again becomes deenergized, both lamps L and L, at studios A and B, respectively, again become illuminated, thus again providing an indication for the operators at both studios that the transmitting station connected to the channel bus-bar CB is again available for the transmission of program matter.

Keys K and K and K and K are the master release keys, keys K and K being under the supervision and control of the announcers at studios A and B, respectively, and keys K and K being under the supervision and control of the operator or operators at the control room. The keys at studios A and B permit the announcers at these studios to release any one or more of the program transmitting stations from their re spective studios. The keys K and K at the control room break the circuits of batteries B and B and ground, respectively, thereby releasing relays R R and R at studio A, and relays R R and R at studio B, respectively. The keys K and K at studios A and B similarly release relays R R and R at studio A, and relays R R and R at studio B, respectively. Thus, the system enables either the announcer in the studio or the operator in the control room to simultaneously release all of the transmitting stations connected to his (the announcers) studio.

In studio A, the output of the announcers microphone MA passes through the micro phone control equipment. OP to the lower contacts j and 7c of the switch K The output of the program microphone MP simi larly passes through the microphone control equipment CP to the lower contacts 3' and 7c of the switch K The nemo circuit NC is connected to the upper contacts a and Z) of the switch K The upper contacts a and b of the switch K are connected to the blades 6 and f of the switch K The blades e and f of the switch K are connected to the input of the' amplifier CA at the control room. lVhen the switch K is thrown downwardly to engage contacts 9' and k, the announcers microphone MA is then connected to the amplifier CA By throwing the switch K upwardly to engage contacts a and Z2, and by throwing switch K downwardly to engage contacts and is, the program microphone MP will then be connected to the amplifier CA By throwing both switches K and K to their upward positions, the nemo circuit NC will then be connected to the amplifier CA By leaving switch K in its upward position, and by operating switch K the announcer at studio A may connect either the announcers microphone MA or the nemo circuit N C to the amplifier CA A lamp L is located at studio A and provides an indication to the announcer at studio A that the equipment of the control room corresponding to studio A is in readiness for operation. Clearly, the lamp L may, if desired, be a colored lamp to distinguish this lamp from some or all of the other lamps. By closing a key K at the control room, the control rooln operator then sends current from a battery B, through the lamp L at studio A, this circuit including the battery 13 key K conductor 27, lamp L and ground. Another lamp L which is located at the control room, is also operated by key K The circuit of lamp L includes the battery B the key K the lamp L and ground. It is to be noted thatthe winding of the main relay R at the control room can not become energized unless the key K in the control room has first been closed. This will prevent the transmission of program matter to one or more of the radio transmitting stations before the proper connections have been made at the control room.

The main relays R and R at the control room open the main transmission paths between studios A and B and the studio busbars SI), and S5 respectively, whenever it is considered undesirable to transmit the sounds originating in the studios. Again confining the description of the apparatus at the control room to that which corresponds to studio A, it is apparent that one terminal of the winding of the main relay R is grounded, and that the other terminal of the winding of the main relay R is connected through conductor to the contacts 0 and l of the switch K The blade 9 of the switch K is connected to the battery B at the control room through conductor 27 and key K when key K is closed. Thus, when key K is closed, the operation of the switch K at the studio to close either contact 0 or contact Z will permit current to flow from the battery B, at the control room through conductors 27 and 40, and through the winding of the relay R When the winding of the relay R becomes energized, one of its armatures a closes a contact which permits current to flow from the battery B to the lamp L this circuit being closed through the armature a of the relay R and ground. Lamp L indicates to the operator at the control room whether or not relay R has operated. The contacts 6 and c of the relay R control the transmission through the main transmission path between the amplifier CA at the control roomand the studio busbar S6 When the winding of the relay R is not energized, the armature d of this relay shortcircuits the studio bus-bar S6 thereby short-circuiting all of the line amplifiers connected thereto.

When the key K at the control room is operated, causing lamp L at the studio to become illuminated to provide an indication to the announcer at studio A that everything in the control room is in readiness for transmission of program matter originating in that studio, and when the switches K and K at the studio are operated to connect either the program microphone MP or the announcers microphone MA or the nemo circuit NC to the amplifier CA at the control room, either lamp L L or L will be illuminated at the studio to indicate to the announcer which of these sources has been connected to the amplifier CA at the control room. The circuit for lamp L includes the battery B the key K conductor 27, blade h and contact (1 of the switch K blade g and contact Z of the switch K lamp L and ground. The circuit for lamp L includes the battery B key K conductor 27, blade h and contact m of the switch K lamp L and ground. The circuit for lamp L includse the battery B key K conductor 27, blade in and contact d of the swtich K blade 9 and contact 0 of the switch K lamp L and ground. A lamp L is controlled by a relay R both of which are at the control room, the lamp providing a visible indication to the operator at the control room that the announcer at studio A has set up his equipment so as to transmit program matter coming over the nemo circuit NC The winding of the relay R is connected to a battery B at studio A through a conductor 41, the contact d and the blade h of the switch K Inasmuch as the switch K must be thrown to its upward position to connect the nemo cir cuit NC to studio A, the relay R at the control room will thereupon become energized, attracting its armature and illuminating lamp L by the flow of current therethrough from a battery B Similarly, a relay R controls a single lamp L to provide a visible indication to the operator at the control room that the announcer at studio B has set up his equipment so as to transmit the program matter coming over the nemo circuit N0 I he line relays LE LR and LE corresponding to studio A, and the line relays LBJ, LE and LE corresponding to studio B, are so arranged that the line amplifiers LA LA and LA may be switched from one studio bus-bar, such as S6,, to the other studio bus-bar S71 This has already been explained hereinabove. Yet, in each of the line relays, such as LB one terminal of the winding of the relay 1s connected to an armature c of that relay, both being grounded. The operation of the line relay LR illuminates a lamp L by the flow of current therethrough from a battery B thereby providing an indication that the line relay LE has operated. The armatures a and b of the line relay LE control the main transmission path between the studio bus-bar SB and the line amplifier LA The other terminal of the winding of the line relay LR is connected to the winding of the relay R in studio A. These windings are in parallel relationship and consequently are simultaneously energized or deenergized.

One of the features of this invention is the provision of a telephone communication system between the announcers in the various studios and the operator or operators in the control room, so that telephone service may be very promptly obtained. In this invention, a telephone system interconnects each studio with the control room, permitting the announcer in the studio to speak to the control room operator associated with his studio. Keys TK and TK T K and TK are located in studios A and B, respectively. TVhen the announcer in studio A closes the telephone key TK and lamp L at the control room lights up, current flowing from a battery B through the key T K conductor 50, lamp L and ground. Thus, the announcer at studio A attracts the attention of the operator at the control room, advising him that he desires to communicate with him telephonically. It

will be understood, however, that lamp L or other visual means, would not be necessary at the control room to attract the control room operators attention if the operator atthe control room continually wore a telephone headset. Similarly the operator at studio B may attract the attention of the operator at the control room by operating a telephone key TK, at his studio, lamp L then becoming illuminated. Keys K and K are located atthe control room, one associated with each studio, these keys being employed to advise the announcers in the studios that the operator or operators in the control room desire to speak to the announcers in the studios by telephone. By closing key K at the control room, a lamp L at studio A is illuminated, current flowing from a battery B at the control room through the key K conductor 51, lamp L and ground. Similarly, lamp L at studio B indicates to the announcer at that studio that the control room operator desires to have a telephone conversation with him. Yet, it will also be understood that these visual means would not ordinarily be necessary if the announcers at the studios were equipped with telephone headsets.

The telephone key 'TK and the lamp L and the telephone key TK and the lamp L are located, respectively, in studios A and B, key TK being operated by the announcer in studio A to illuminate lamp L in studio B whenever the announcer in studio A desires to connect his telephone circuit to the telephone circuit in studio B, telephone key TK in studio B being operated to illuminate lamp L at studio A whenever the announcer in studio B desires to connect his telephone circuit to the telephone circuit at studio A. hen the announcer in studio A closes the telephone key TK current flows from battery B at studio A through the telephone key TK conductor 52, lamp L at studio B, and ground. A telephone substation circuit 813,, including a telephone transmitter and a telephone receiver of any well known type, is connected to a similar-telephone substation circuit SB at studio B, telephonic currents flowing from the substation circuit SB at studio A, through key TK,, conductors and 54, telephone key TK, at studio B, and the telephone substation circuit SE Similarly, when the announcer at studio B operates the telephone 1 key TK, at his studio, current flows from a battery B at studio B, through the key TK conductor 55, lamp L30, at studio A, and ground. Telephonic currents flow between the telephone substation circuit S13 at studio B, and the telephone substation circuits SB at studio A as soon as the announcer at studio A operates telephone key TK It is another feature of this invention to provide a telephone circuit between the announcer in one of the studios, the operator at the control room and the operator at one of the radio transmitting stations, the radio station operator being therefore connect-ed telephonically with the control room operator and with the announcer in the studio furnishing the program. Accordingly, relays TR TR and TR and relays TR,, TR] and TR, are located in the control room, relays TR and TR, corresponding to the radio transmitting station connected to the channel bus-bar CB relays TP and TR! corresponding to the radio transmitting station connected to the channel bus-bar CB and relays TR and T R corresponding to the radio transmitting station connected to the channel bus-bar CB3. These relays are normally controlled by the line relays at the studio. In connection with studio A and the apparatus at the control room associated therewith, it may be said that the line relay LR controls the operation of the relay TR through the armature of the line relay LE Thus, when the line relay LR becomes operated. armature c is attracted, energizing the winding of the relay TR current flowing from abattery B through the winding of the relay TR telephone key TIL, armature c of the line relay LR and ground. Similarly, the operation of the armature c of the line relays LE and LR. control the operation of the telephone relays TR and TR current flowing from batteries B and B through the windings of these relays and through the telephone keys TK and TK respectively.

Accordingly, when one of the line relays, such as LE is operated to connect studio A to the radio transmitting station connected to the channel bus-bar CB the corresponding telephone relay TR at the control room is operated to connect the telephone substation circuit T13 located at the same radio transmitting station. to the telephone substation circuit SB at the control room, and, if the telephone key TK at studio A is closed, to the telephone substation circuit SB at studio A. Similarly. the operation of the line relays LR, and LR bring about the operations of the corresponding telephone relays TR and TH respectively, to connect the telephone substation circuits TB and T13 at the radio transmitting stations connected to the channel bus-bars CB and CB respectively, to the same telephone substation circuit SB at the control room, and, if the telephone key TK at studio A is closed, to the telephone substation circuit SB at that studio. Telephone substation circuits TB TB and TB located at the transmitting stations connected to the channel bus-bars CB CB and CB respectively. may be connected to a telephone substation circuit S13 at the control room through the operations of the telephone relays TR, TR, and TR respectively, and, if the telephone key TK at studio B is closed, to the telephone substation circuit SE at that studio.

The telephone relays have been shown hereinabove to be controlled by the line relays. These telephone relays may be controlled by the telephone keys at the control room. The telephonekeys TK TK and TK may be used to control telephone relays TR TR and TR and the telephone keys TK TIL. and TK may be used to control the telephone relays TR, T11 and TR respectively. In connect-ion with studio A, it may be said that the operator at the control room may connect his substation circuit S13 to the substation circuit TB at the radio transmitting station corresponding to the channel bus-bar CB by closing key TK Vhen key TK is closed, a telephone relay TR is energized by the flow of current from battery B through the winding of that relay, through key TK and ground. The arma-' tures of the relay TR are attracted, thereby connecting the telephone substation circuit SB at the control room, to the telephone substation circuit TB at the radio transmitting station. Similarly, the operation of the keys TK and TK may be used to connect the telephone substation circuit SB at the control room, to the telephone substation circuits TB and TB, at the radio transmitting stations associated with the channel bus-bars CB and CB respectively. It will be obvious that while only one telephone substation circuit has been shown herein at the control room, operatively associated with the telephone keys TK ,.TK and TK separate telephone substation circuits may be connected to the various telephone substation circuits at the radio transmitting stations T13 T13 and TB;,, respectively.

Relays SR SR and SR, are provided at the control room, and are energized when the corresponding line amplifiers LA LA and LA are ready for use. but are not connected to a studio bus-bar. The inputs of these line amplifiers will become short-circuited by the armatures of the relays SR SR and SR when the line relays are operated. In other words, when the line relays LE LR and LE corresponding to studio A, and the line relays LR], L11 and LE corresponding to studio B are not energized, relays SR SB and SR at the control room. will be operated. The relays SR SR and SR, are interlocked with the relays IR IR and IR the signal keys 5K SK and 8K and the relays R R and R respectively. The interlocking of these keys and relays permits the operation of relays SR SB: and SR only when the signals keys SK SK and SK, are closed, when the relays 1B IE and IR are unoperated, and when the relays R R and R are operated, respectively. For the sake of simplicity, the operation of only one of these relays, SR will be considered. One terminal of the winding of the relay SR, is connected to ground through conductor 29, the middle contact of the key SK and the armature of the relay R The other terminal of the winding of the relay SR is connected to battery B at the control room, through conductor 30, conductor 21 and the armature of the relay 1R Therefore, upon closure of the signal key SK current will flow from battery B through the winding of the relay SR thereby operating said relay. The armature of the relay SR is then attracted, providing a short-circuit for the input of the line amplifier LA Relay SR is always operated to put a short circuit on the input of the amplifier LA when the signal key SK is closed, when the relay IE is unoperated and when the relay R is operated. \Vhen the winding of the relay 1R becomes energized, as, for example, when the relay R in studio A, becomes energized, the circuit connecting battery B at the control room, and the winding of the relay SR is opened, deenergizing the winding of relay SR removing the short-circuit from the input of the amplifier LA and placing this channel in an operative condition. Similarly. relays SR and SR are energized by current from battery B at the control room through the armatures of relays IE and IE conductors 31 and 32. the middle contacts of signal keys SK and SK the armatures of relays R and B respectively, and ground.

One of the features of this invention is the provision of a monitoring system for monitorin the output of each studio while the program matter is being passed through the studio and through the amplifier at the control room. This permits the announcer in the studio, or the artist speaking into the microphone to determine whether the program matter is being transmitted from the studio to the control room. Accordingly the outputs of the amplifiers CA and CA are multiplied to studios A and B through resistances R and R and conductors and 61, and through resistances R and R and conductors 62 and 63, respectively. Conductors 60 and 61 terminate in a jack J at studio A, so that the operator at the studio, or the artist speaking into the microphone may monitor his own circuit if he connects a plug P to jack J plug P being connected to a headset H Conductors 62 and 63 are connected to a jack J so that the announcer. or artist at studio B may, upon connecting plug P into ack J monitor the output of studio B after the program matter is transmitted through the amplifier CA at the control room, plug P at studio B being connected to a headset H The operator in studio A may also connect plug 1? at his studio with jack J jack J being connected through conductors 64 and 65, conductors 63 and 62, and through resistances R and R to the output of the amplifier CA at the control room, this amplifier amplifying program matter transmitted from studio B. Similarly, the operator at studio B may connect plug 1? to jack J which is connected to the output of the amplifier CA at the control room, through conductors 66 and 67, conductors 60 and 61 and resistances R and R to the amplifier CA at the control room, amplifying the program matter transmitted from studio A. In accordance with this invention, the operator at any one of the studios may monitor the program matter transmitted from his, or from any other studio, to the control room, which may obviously be at some distant point. After the program matter has passed through the amplifier at the control room corresponding to the studio to be monitored. the resistances R and R and R and R these resistances being of large and definite magnitudes. are inserted between outputs of amplifiers CA and CA at the control room, and the corresponding jacks at studios A and B, respectively, in order that any noise or other disturbance on the monitoring circuits will have but a negligible effect on the program matter being transmitted from the studios.

It has been pointed out hereinabove that visual signals are provided in the control room to indicate to the operator atthe control room that astudio is connected to a transmitting station. Similarly, visual signals may be provided to indicate at a transmitting station that some studio is connected to that transmitting station. In other words,

signals may be provided at each transmitting station to indicate when program matter should be comin to that transmitting station. This may be accomplished by having a circuit extend between contacts on the main relays and line relays, so thatwhen a main relay and an associated line relay are operated, and the desired transmitting station is on the air, this circuit will be closed to operate a relay, for example, R at the control room, the operation of this relay controlling the operation of another relay, R at the transmitting station, the armature of which controls the illumination of the lam L at the transmitting station. In connection with the transmission of program matter from studio A to the transmitting station connected with the channel bus-bar CB when the main relay R is operated, and when the line relay LR is also operated to connect the output of the amplifier CA to the transmitting station connected to the channel bus-bar CB a circuit is closed through relay R this circuit including armature a of the main relay R armature d of the line relay LE the winding of the relay R battery B and ground. Relay R becomes energized to attract its armature. Current then flows from battery B through the winding of the relay R at the transmitting station, this circuit including the battery B the armature of the relay R and its contact, the winding of the relay R and ground. The armature of the relay R is attracted, closing a circult through lamp L at the transmittlng station, current flowing from the battery B through the lamp L through the armature of the relay R at its contact and ground. Thus, a visual signal is provided at the transmltting station to indicate to the operator at the transmitting station that program matter should be coming to that transmitting station. Similarly, when program matter should be coming to the transmitting stations connected to the channel bus-bars CB and CB the relays R and R at the control room are energized by the flow of current therethrough from batteries B and B which in turn operate relays R and R at the assoc ated transmitting stations,lllummatlnglamps L and L by the fiow of current therethrough from batteries B and B respectively.

The phrase transmitting station or radio transmitting station, as employed herein designates a radio transmitter, public address equipment, an individually loaded loud speaker or any other suitable signaling device or circuit. The word studio, as employed herein, designates a place where a program of news, music or any other sound originates, whether it be 1n a room ad acent to the control room, or at some point distant from the control room, requiring a connection thereto by local or long distance telephone lines, or any other suitable signaling medium.

While only two studios and three transmitting stations have been shown and described herein, it will be understood that the system is adaptable to connect any number of studios and any number of transmitting stations, within the scope of the invention.

Vhile no auxiliary equipment, such as equalizers, repeating coils, artificial lines, etc., are absolutely essential to the operation of the system, as shown herein, it is to be understood that such equipment may be added, as found desirable, in any manner well known to the art, without departing from the spirit of the invention or from the scope of the appended claims.

While this invention has been shown and described in one particular embodiment, merely for the purpose of illustration, it is to be clearly understood that the general principles of this invention may be embodied in other and widely varied organizations without departing from the spirit of the invention or the scope of the appended claims.

What is claimed is:

1. In a radio broadcasting system, a plurality of studios wherein programs originate, a plurality of transmitting stations, means for interconnecting the various studios with the various transmitting stations so that the programs originating at any two of the studios may not be simultaneously transmitted by any one of the transmitting stations, and means at each studio for monitoring the output of any desired studio.

2. In a radio broadcasting system, a plu rality of studios wherein programs originate, a plurality of transmitting stations, means for interconnecting the various studios with the various transmitting stations so that the programs originating at any two of the studios may not be simultaneously transmitted by any one of the transmitting stations, and means at each studio for monitoring the output of any desired transmitting station.

3. In a radio broadcasting system, a plurality of studios wherein programs originate, a plurality of transmitting stations, a control room including means for interconnecting the various studios with the various transmitting stations so that the programs originating at any two of the studios may not be simultaneously transmitted by any one of the transmitting stations, and means extending from the control room to the various studios to enable the announcers in the various studios to simultaneously and selectively monitor the program transmitted from any of the studios.

4. In a radio broadcasting system, a plurality of studios wherein programs originate, a plurality of transmitting stations, means for interconnecting the various studios with the various transmitting stations so that the programs originating at any two of the studios may not be simultaneously transmitted by any one of the transmitting stations, and means to enable the announcers in the various studios to simultaneously monitor the outputs of their respective studios.

5. In a radio broadcasting system, a plurality of studios wherein programs originate, a plurality of transmitting stations, means for interconnecting the various studios with the various transmitting stations so that the programs originating at any two of the studios may not be simultaneously transmitted by any one of the transmitting stations, and a plurality of monitoring circuits one extending from each transmitting stations to each studio so that the announcers in the various studios may simultaneously monitor the programs being transmitted by any of the various studios.

6. In a radio broadcasting system, a plurality of studios wherein programs originate, a plurality of transmitting stations each employing a different carrier frequency, a control room through which pass circuits extending from the various studios to the various transmitting stations, means to permit any number of transmitting stations to transmit the program of any one studio, means to prevent the connection of any two studios to any one transmitting station, a plurality of amplifiers at the control room one associated with each studio, and a plurality of monitoring circuits one extending from the output of each amplifier to the corresponding studio to enable the announcer at that studio to monitor the program emanating from his studio.

7. In a radio broadcasting system, a plurality of studios wherein programs originate,

a plurality of radio transmitting stations each employing a different carrier frequency, a control room, a plurality of circuits extending from the various studios through the control room to the various radio transmitting stations, means at the control room to connect the various transmitting stations to the various studios and to prevent the connection of any two studios to any one transmitting station, a plurality of amplifiers at the control room one corresponding to each studio, a plurality of monitoring circuits one extending from the out-put of each amplifier at the control room to each studio, and means to enable the announcer at each studio to monitor through said monitoring circuits the output of any one of said studios.

8. The combination of a plurality of studios wherein programs originate, a distant control room, a plurality of circuits extending from each studio to the control room for the transmission of program matter from the various studios, a plurality of amplifiers at the control room one corresponding to each studio, and a plurality of monitoring circuits each including resistance of a definite magnitude, the resistance of each monitoring circuit interposing a transmission loss corresponding to the amplification of each amplifier, each monitoring circuit extending from the output of one of the amplifiers at the control room to the associated studio, thereby enabling the announcer in any studio to monitor the program matter originating at his studio and being transmitted through the control room.

9. In a radio broadcasting system, a plurality of studios wherein programs originate, a plurality of transmitting stations each employing a different radio frequency, a control room through which pass circuits interconnecting the various studios with the various transmitting stations so that the programs at the various studios may be simultaneously broadcast by the various transmitting stations, means to prevent the simultaneous transmission of the program matter of two studios through any one transmitting station, a plurality of visual indicating devices one at each studio, and means whereby said indicating devices may indicate to the announcers at the various studios that the control room operator is prepared to transmit the program matter originating in said studios through the various transmitting stations.

10. In a radio broadcasting system, a plurality of studios wherein programs originate, a plurality of transmitting stations each employing a different radio frequency, a control room through which pass circuits interconnecting the various studios with the various transmitting stations, a plurality of visual indicating devices one at each studio, and means extending between the various studios and the control room to operate each indicating device in order to indicate to the announcer at each studio that the carrier frequency characteristic of a particular transmitting station is on the air.

11. In a radio broadcasting system, a plurality of studios wherein programs originate, a plurality of transmitting stations each employing a different radio frequency, a control room through which pass circuits interconnecting the various studios with the various transmitting stations, a plurality of visual indicating devices one at each studio, a plurality 0f detecting devices one at each transmittlng station, each detecting device detecting some of the current of the radio frequency characteristic of the associated transmitting station, and means at each transmitting station whereby the detected current may be transmitted to the indicating device of one of the studios in order to operatethat indicating device at the studio from which program matter is being supplied to that transmitting station.

12. In a radio broadcasting system, a plurality of studios wherein programs originate, a plurality of program transmitting stations, means for connecting any one of the studios to one or more of the program transmitting April, 1927.

EDMUND R. TAYLOR. OSCAR B. HANSON.

Re ferencea C1 ted Swthe 1,499,081 179-2 Maxfield l, 575, 984 250-6