US2339678A - Communication system - Google Patents

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US2339678A
US2339678A US453342A US45334242A US2339678A US 2339678 A US2339678 A US 2339678A US 453342 A US453342 A US 453342A US 45334242 A US45334242 A US 45334242A US 2339678 A US2339678 A US 2339678A
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station
stations
type
switch
circuit
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Richard H Campbell
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Webster Electric Co Inc
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Webster Electric Co Inc
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M9/00Arrangements for interconnection not involving centralised switching
    • H04M9/001Two-way communication systems between a limited number of parties

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  • the present invention relates to communication systems and more particularly to intercommunicating systems of the loudspeaking type.
  • One of the objects of the present invention is the provision of a new and improved communieating system of the loudspeaking type comprising one or more stations of the so-called master type, each of which includes an amplifier and a communication direction control switch, and one or more so-called stations of the type having no amplifier or communication direction control switch, in which operators at stations of the latter type can signal operators at master stations that they desire to communicate with them.
  • a further object of the present invention resides in the provision of a new and improved communicating system ofthe character specified wherein operators at substations can not only signal master stations, but are simultaneously apprised as to whether or not the signal has sounded at the master station.
  • Another object of the present invention is to provide a new and improved communicating system of the character specified wherein operators at substations can signal the master stations and a signal is produced at the substation in the event the called station is not busy.
  • a further object of the present invention is the provision of a new and improved communicating system of the loudspeaking type in which the switching operations for signaling and communicating are simplified.
  • the system is shown to include two master stations indicated by reference characters I and 2 and three substations indicated by reference characters 3, 4, and 5. It should be understood, however, that the system may include more than the indicated number of stations of either type.
  • the master stations are identical and consequently it is deemed necessary to describe in detail but one f these and to indicate the corresponding apparatus at the other by the same reference characters followed by the sufilx 2.
  • the apparatus at station I includes an amplifier ID, a loudspeaker I2 01 the permanent magnet type adapted to be utilized both as a receiver and a microphone, a three-position combined Racine, Wis., a corcommunication direction control and power switch l4 and a signal producing device l6 which may take the form of a buzzer and which is supplied with power through a transformer I8.
  • the amplifier l8 may be of any conventional construction and be supplied with power through the power supply lines 20.
  • the amplifier i conditioned to be inoperative when the switch I4 is in its indicated uppermost position.
  • the B supp y to the amplifier is broken by the switch blade 22 in circuit with the B supply conductor 24.
  • the switch II which, of course, includes the-blade 22 is operated to either of its two other positions, the amplifier is rendered immediately operative upon completion of the 3 supply circuit.
  • the communication direction control switch I4 is of the three-position type. In one position, that indicated, the loudspeaker I2 is connected to a circuit consisting of the pair of conductors 26 by means of switch blades 28 and a circuit consisting of the two conductors 38. In the intermediate position, the amplifier input i connected to conductors 26 through the switch blades 28 and the amplifier input circuit including the two conductors 32, and the amplifier output is connected to the loudspeaker through a circuit including the output conductors 34, the switch blades 36, the pai or conductors 38, and the previously referred to conductors 38.
  • the connections of the loudspeaker and circuit 26 to the amplifier loudspeaker being connected to the amplifier input through conductors 30, 38, switch blades 36, conductors 48, and the input conductors 32, and circuit 28 being connected to the amplifier output through the switch blades 28 and conductors 34.
  • switch blades constituting switch l4. be operable simultaneously and they have been thus illustrated as being mgglliyanically connected.
  • the master station includes a plurality of station selector switches 43, 44, and 45, whereby the communication circuit 26 may b connected to circuits individual to the substations 3, 4, and 5. These station selector switches are connected in parallel to the communication circuit 26 so that when any of the switches are closed the circuit 26 is connected to the interstation circuit indiswitch is also prefvidual to the stations associated with-the selector switches.
  • the master station also includes a station selector switch 46 adapted to be closed to signal master station 2.
  • the switch 46 is connected in parallel with the other selector switches.
  • the master station I is also provided with a two-position signal and communication circuit controlling switch 48 adapted in one (its indicated) position to connect the signal producing device I6 to an interstation circuit including the pair of conductors 50 extending to other stations in the system.
  • the circuit 50 and signal producing device I6 are connected in series with the secondary winding 52 of the transformer l8, the circuit including the pair of conductors 54..
  • the circuit 50 is connected to the circuit 26 through a pair of branch conductors 56.
  • the circuit 50 may be utilized either as a signaling or communication circuit.
  • the substations hav interstation circuits individual thereto, these being indicated by reference characters 63, 64, and" 65, respectively.
  • the apparatus at the various substations is identical and it is, therefore, deemed necessary to describe in detail only that at station 3.
  • the substation includes a loudspeaker 66 utilizable both as a receiver and a microphone and a communication and signal circuit controlling switch including the two switch blades 68.
  • the switch 66 normally occupies a position connecting a loudspeaker 66 to interstation circuit 63 and is operable to connect the loudspeaker either to circuit 50 or to circuit 60-2 in order that the operator at the substation may signal the operators at the master stations that be desires to communicate with them.
  • the switch 66 is moved to the left thereby to connect the loudspeaker 66 to circuit 50 through conductors l0.
  • the switches 66 at the substations connect the loudspeakers thereat to their respective interstation circuits.
  • the selector switch 43 is closed to interconnect circuits 26 and 63 and the operator at station I operates the communication direction control switch I4 to its lowermost position to connect the loudspeaker I2 to the input of the amplifier and the circuit 26 to the output of the amplifier, thus conditioning the circuits for com munication from station II to station 3.
  • the communication direction control switch is operated to its intermediate position to reverse the connections of loudspeaker I2 and circuit 26 to the amplifier thereby to condition these for communication from station 3 to station I.
  • the switch 68 When the operator at a substation desires to call a master station, as, for instance, when the operator at station 3 desires to call station I, then the switch 68 is moved to the left to connect loudspeaker 66 to circuit 50. This operation completes a circuit through the signal producing device, the secondary 52 of transformer l8, and loudspeaker 66, placing all these in series, with the result that the signal producing device I6, which may be a buzzer as heretofore indicated, produces an audible sound at the master station and the loudspeaker 66 produces an audibl sound at the substation, thus indicating to the operator at the latter that station I is not busy.
  • the signal producing device I6 which may be a buzzer as heretofore indicated
  • the operator at station 2 moves switch 48-2 from its uppermost to its lowermost position, thereby connecting the loudspeaker I2-2 at station 2 to the circuit 50-2 and thereafter communication is carried on in opposite directions under the control of the operator at station I who again has merely to operate the communication direction control switch I4 between its intermediate and lowermost positions.
  • switch 48 may be constructed as a three-position switch having a circuit opening position in addition to those indicated so that it can be operated to open both the signal and communication circuits when desired. If desired, this switch could be connected to the various station selector switches in such manner that it is operated to its assacvs circuitopening position whenever one of the station selector switches is closed.
  • the master station selector switches 48 may close circuits to the two-way communication circuits of other stations rather than completing circuits to the signaling circuits at the master stations as indicated. This would enable master stations immediately to call other master stations as distinguished from signaling other master stations.
  • a communication system of the loudspeaking type including a first station having a receiver utilizable also as a microphone, an ampli bomband a communication direction control switch and a second station having a receiver utilizable also as a microphone
  • the combination including, signal producing means and switch means at the first station, an interstation circuit connecting said stations, circuits controlled by said switch means for selectively connecting said interstation circuit to said signal producing means or to said communication direction control switch, and means including a switch at the second station for simultaneously connecting said receiver to said interstation circuit and completing a circuit to said signal producing means.
  • a communication system of the loudspeaking type including one or more stations .of a first type each having a receiver utilizable also as a microphone, an'amplifier and a communication direction control switch and one or more stations of a second type each having a receiver utilizable also as a microphone
  • the combination including, signal producing means and switch means at stations of the first type, interstation circuits individual to each of said stations of the first type extending to stations of the second type and to other stations of the same type, circuits controlled by said switch means at stations of the first type for selectively connecting the interstation circuit associated with the station to the signal producing means or to the communication direction control switch, and means including switches at stations of the second type for simultaneously connecting the receivers thereat to said interstation circuits and completing circuits to the signal producing means.
  • a communication system of the loudspeaking type including one or more stations of a first type each having a receiver utilizable also as a microphone, an amplifier and a communication direction control switch and one or more stations of a second type each having a receiver utilizable also as a microphone
  • the combination including, signal producing means and switch means at stations of the first ype, interstation circuits individual to each or said stations of the first type extending to stations of the second type, circuits controlled by said switch means at stations of the first type for selectively connecting the interstation circuit associated with the station to the signal producing means or to the communication direction control switch, and means including switches at stations of the second type tor simultaneously connecting the receivers thereat to said interstation circuits and completing circuits to the signal producingsecond station for connecting said receiver to said interstation circuit and completing a circuit through said signal producing means and receiver to give an audible signal at both stations when said switch means at thefirst station connects the interstation circuit to said signal producing means.
  • a communication system or the loudspeaking type including one. or more stations of a type each having a receiver utilizable. also .as a microphone, an amplifier and a communication direction control switch and one or more stations of a type eachhaving a receiver utilizable also as a microphone
  • the combination including, signal producing means and switch means at stations of the first type, interstation circuits individual to stations of the first type connecting statiqns of the second type to stations of the first type and stations of the first type to others of the same type, circuits controlled by said switch means at stations of the first type for selectively connecting the in-. terstation circuit associated with the station to the signal producing means or to the communication direction control switch at the station, and
  • switch means including switches at stations of the second type for connecting the receivers thereat to I tions of a type eachhaving a receiver utilizable also as a microphone, the combination including. si nal producing means and switch means at stations of the first type, interstation circuits individual to stations of the first type connecting stations of the second type to stations of the first type, circuits controlled by said switch means at stations of the first type for selectively connecting the interstation circuit associated with the station to the signal producing means or to the communication direction control switch at the station, and means including switches at stations of the second type for connecting the receivers thereat to said interstation circuits and completing circuits through said signal producing means and receiver to give an audible signal at both types of stations when said switch means at stations of the firsttype connect the interstation circuit individual thereto to the signal producing means thereat.
  • a station selector switch at the first station for connecting said communication direction control switch to said first interstation circuit
  • the combination including, signal producing means and switch means atstations or the first type, combined signaling and communication circuits individual to stations of the first type connecting stations of the second type to stations of the first type and stations of the first t to others of the same type, com- 8.
  • signal producing means and switch means atstations or the first type
  • combined signaling and communication circuits individual to stations of the first type connecting stations of the second type to stations of the first type and stations of the first t to others of the same type, com- 8.
  • com- 8 In a communication, system of the loud.
  • stations 01 a type each having a receiver utilizable also as a microphone, an amplifier and a communication direction control switch and one or more stations oi a type each having a receiver utilizable munication circuits between stations 0! the first and second types, circuits controlled by said,
  • station to the signal producing means or to the communication direction control switch at the station, station selector switches at stations of the first type for connecting the communication direction controlling switches thereat to said communication circuits, and means including switches at stations of the second type normally connecting the receivers thereat to their respective communication circuits and operable to complete circuits through said combined signaling and communication'circuits, signal producing means at stations of the first type and the receivers at stations at the second type to give an audible signal at both types of stations when said switch means at stations of the first type connect the combined signaling and communication circuit individual thereto to the signal producing means thereat.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Interconnected Communication Systems, Intercoms, And Interphones (AREA)

Description

,Jan. '18, 1944.
R. H. CAMPBELL COMMUNICATION SYSTEM v Filed Aug. 3, 1942 1 WNN ZZZ/6202M 273,056 ZZ W 6' M Patented Jan. 18, 1944 2 COMMUNICATION SYSTEM Richard R. Campbell, Racine, -Wis., assignor to Webster Electric Company,
poi'ation of Delaware Application August 3, 1942, Serial No. 453,342
8 Claims.
The present invention .relates to communication systems and more particularly to intercommunicating systems of the loudspeaking type.
One of the objects of the present invention is the provision of a new and improved communieating system of the loudspeaking type comprising one or more stations of the so-called master type, each of which includes an amplifier and a communication direction control switch, and one or more so-called stations of the type having no amplifier or communication direction control switch, in which operators at stations of the latter type can signal operators at master stations that they desire to communicate with them.
A further object of the present invention resides in the provision of a new and improved communicating system ofthe character specified wherein operators at substations can not only signal master stations, but are simultaneously apprised as to whether or not the signal has sounded at the master station.
- Another object of the present invention is to provide a new and improved communicating system of the character specified wherein operators at substations can signal the master stations and a signal is produced at the substation in the event the called station is not busy.
A further object of the present invention is the provision of a new and improved communicating system of the loudspeaking type in which the switching operations for signaling and communicating are simplified.
Other objects and advantages or the present invention will become apparent from the ensuing description in which reference is had to the ac-.
companying drawing, the single figure of which is a diagrammatic representation of a system embodying the invention.
In the embodiment of the invention illustrated in the figure, the system is shown to include two master stations indicated by reference characters I and 2 and three substations indicated by reference characters 3, 4, and 5. It should be understood, however, that the system may include more than the indicated number of stations of either type.
The master stations are identical and consequently it is deemed necessary to describe in detail but one f these and to indicate the corresponding apparatus at the other by the same reference characters followed by the sufilx 2.
The apparatus at station I includes an amplifier ID, a loudspeaker I2 01 the permanent magnet type adapted to be utilized both as a receiver and a microphone, a three-position combined Racine, Wis., a corcommunication direction control and power switch l4 and a signal producing device l6 which may take the form of a buzzer and which is supplied with power through a transformer I8.
The amplifier l8 may be of any conventional construction and be supplied with power through the power supply lines 20. The amplifier i conditioned to be inoperative when the switch I4 is in its indicated uppermost position. At this time the B supp y to the amplifier is broken by the switch blade 22 in circuit with the B supply conductor 24. When the switch II, which, of course, includes the-blade 22, is operated to either of its two other positions, the amplifier is rendered immediately operative upon completion of the 3 supply circuit.
The communication direction control switch I4 is of the three-position type. In one position, that indicated, the loudspeaker I2 is connected to a circuit consisting of the pair of conductors 26 by means of switch blades 28 and a circuit consisting of the two conductors 38. In the intermediate position, the amplifier input i connected to conductors 26 through the switch blades 28 and the amplifier input circuit including the two conductors 32, and the amplifier output is connected to the loudspeaker through a circuit including the output conductors 34, the switch blades 36, the pai or conductors 38, and the previously referred to conductors 38. In the third or lowermost position of the communication control switch, the connections of the loudspeaker and circuit 26 to the amplifier loudspeaker being connected to the amplifier input through conductors 30, 38, switch blades 36, conductors 48, and the input conductors 32, and circuit 28 being connected to the amplifier output through the switch blades 28 and conductors 34.
It is preferred that the various switch blades constituting switch l4. be operable simultaneously and they have been thus illustrated as being mgglliyanically connected. The er biased to return from its lowerm tion to its intermediate position by a sg r i n g l although it can be biased to return to its upper- 3105b position from either of its two other posions.
The master station includes a plurality of station selector switches 43, 44, and 45, whereby the communication circuit 26 may b connected to circuits individual to the substations 3, 4, and 5. These station selector switches are connected in parallel to the communication circuit 26 so that when any of the switches are closed the circuit 26 is connected to the interstation circuit indiswitch is also prefvidual to the stations associated with-the selector switches.
The master station also includes a station selector switch 46 adapted to be closed to signal master station 2. The switch 46 is connected in parallel with the other selector switches.
The master station I is also provided with a two-position signal and communication circuit controlling switch 48 adapted in one (its indicated) position to connect the signal producing device I6 to an interstation circuit including the pair of conductors 50 extending to other stations in the system. In this position of the switch, the circuit 50 and signal producing device I6 are connected in series with the secondary winding 52 of the transformer l8, the circuit including the pair of conductors 54.. In the second position of the switch 48, the circuit 50 is connected to the circuit 26 through a pair of branch conductors 56. As a result, the circuit 50 may be utilized either as a signaling or communication circuit.
The substations hav interstation circuits individual thereto, these being indicated by reference characters 63, 64, and" 65, respectively.
The apparatus at the various substations is identical and it is, therefore, deemed necessary to describe in detail only that at station 3. The substation includes a loudspeaker 66 utilizable both as a receiver and a microphone and a communication and signal circuit controlling switch including the two switch blades 68. The switch 66 normally occupies a position connecting a loudspeaker 66 to interstation circuit 63 and is operable to connect the loudspeaker either to circuit 50 or to circuit 60-2 in order that the operator at the substation may signal the operators at the master stations that be desires to communicate with them. When the operator at station 3 desires to signal the operator at station I, the switch 66 is moved to the left thereby to connect the loudspeaker 66 to circuit 50 through conductors l0. Whenthe operator at station 3 demost positions, and the switches 66 at the substations connect the loudspeakers thereat to their respective interstation circuits.
In the event the operator at station I desires to communicate with any of the substations, say
station 3, then the selector switch 43 is closed to interconnect circuits 26 and 63 and the operator at station I operates the communication direction control switch I4 to its lowermost position to connect the loudspeaker I2 to the input of the amplifier and the circuit 26 to the output of the amplifier, thus conditioning the circuits for com munication from station II to station 3. To receive a reply from station I, the communication direction control switch is operated to its intermediate position to reverse the connections of loudspeaker I2 and circuit 26 to the amplifier thereby to condition these for communication from station 3 to station I.
when station I desires to communicate with any of the other substations, the operation corresponds to that described above except for the closure of the proper selector switch for the desired substation.
When the operator at a substation desires to call a master station, as, for instance, when the operator at station 3 desires to call station I, then the switch 68 is moved to the left to connect loudspeaker 66 to circuit 50. This operation completes a circuit through the signal producing device, the secondary 52 of transformer l8, and loudspeaker 66, placing all these in series, with the result that the signal producing device I6, which may be a buzzer as heretofore indicated, produces an audible sound at the master station and the loudspeaker 66 produces an audibl sound at the substation, thus indicating to the operator at the latter that station I is not busy. To reply to the call, it is necessary for the operator at station I simply to move switch 48 from its uppermost to its lowermost position thereby interconnecting circuits 26 and 50 through the switch and through the branch circuit 56. Thereafter communication between stations I and 3 is carried on in opposite directions under the control of the operator at station I who manipulates the communication direction control switch I4 between its lowermost and intermediate positions. At this time the buzzer I6 at station I is disconnected from station 60 so that should some other substation or master station desire to signal station I, no audible sound is produced either at station I or the calling station. Asa result, the operator at the calling station is apprised that station I is busy.
In the event that master station I desires to communicate with master station 2, the operator at the former closes a station selector switch 46, thereby interconnecting circuits 26 and 50-2. This interconnection closes a circuit through the buzzer I6'2 which circuit extends through the secondary winding 52-2, the circuits 50-2, 26, and through the loudspeaker I2 at station I. The result is the production of an audible signal by the buzzer at station 2 and an audible signal by the loudspeaker I2 at station I. To reply, the operator at station 2 moves switch 48-2 from its uppermost to its lowermost position, thereby connecting the loudspeaker I2-2 at station 2 to the circuit 50-2 and thereafter communication is carried on in opposite directions under the control of the operator at station I who again has merely to operate the communication direction control switch I4 between its intermediate and lowermost positions.
It may be noted that when one of the master stations calls and communicates with one of the substations, or a master station, as, for instance, when station I calls station 3 or station 2, that the switch 48 at station I need not be operated from its indicated signal circuit closing position to a communication circuit closing position. As a result, other stations may complete signaling circuits to station I to indicate they desire to communicate therewith. In the event it is not desired to have other stations able to signal in this manner when one of the master stations is in communication with another station, then switch 48 may be constructed as a three-position switch having a circuit opening position in addition to those indicated so that it can be operated to open both the signal and communication circuits when desired. If desired, this switch could be connected to the various station selector switches in such manner that it is operated to its assacvs circuitopening position whenever one of the station selector switches is closed.
Although the invention has been disclosed in connection with specific details of a preferred embodiment, it should be understood that such details are not intended to be limitative of the invention except in so far as set forth in the accompanying claims. The system is susceptible not only of the modifications heretofore indicated, but also of others. For instance, the master station selector switches 48 may close circuits to the two-way communication circuits of other stations rather than completing circuits to the signaling circuits at the master stations as indicated. This would enable master stations immediately to call other master stations as distinguished from signaling other master stations.
Having thus described my invention, what I claim as new and desire to secure by United States Letters Patent is:
1. In a communication system of the loudspeaking type including a first station having a receiver utilizable also as a microphone, an ampli fierand a communication direction control switch and a second station having a receiver utilizable also as a microphone, the combination including, signal producing means and switch means at the first station, an interstation circuit connecting said stations, circuits controlled by said switch means for selectively connecting said interstation circuit to said signal producing means or to said communication direction control switch, and means including a switch at the second station for simultaneously connecting said receiver to said interstation circuit and completing a circuit to said signal producing means.
2. In a communication system of the loudspeaking type including one or more stations .of a first type each having a receiver utilizable also as a microphone, an'amplifier and a communication direction control switch and one or more stations of a second type each having a receiver utilizable also as a microphone, the combination including, signal producing means and switch means at stations of the first type, interstation circuits individual to each of said stations of the first type extending to stations of the second type and to other stations of the same type, circuits controlled by said switch means at stations of the first type for selectively connecting the interstation circuit associated with the station to the signal producing means or to the communication direction control switch, and means including switches at stations of the second type for simultaneously connecting the receivers thereat to said interstation circuits and completing circuits to the signal producing means.
3. In a communication system of the loudspeaking type including one or more stations of a first type each having a receiver utilizable also as a microphone, an amplifier and a communication direction control switch and one or more stations of a second type each having a receiver utilizable also as a microphone, the combination including, signal producing means and switch means at stations of the first ype, interstation circuits individual to each or said stations of the first type extending to stations of the second type, circuits controlled by said switch means at stations of the first type for selectively connecting the interstation circuit associated with the station to the signal producing means or to the communication direction control switch, and means including switches at stations of the second type tor simultaneously connecting the receivers thereat to said interstation circuits and completing circuits to the signal producingsecond station for connecting said receiver to said interstation circuit and completing a circuit through said signal producing means and receiver to give an audible signal at both stations when said switch means at thefirst station connects the interstation circuit to said signal producing means.
5. In a communication system or the loudspeaking type including one. or more stations of a type each having a receiver utilizable. also .as a microphone, an amplifier and a communication direction control switch and one or more stations of a type eachhaving a receiver utilizable also as a microphone, the combination including,, signal producing means and switch means at stations of the first type, interstation circuits individual to stations of the first type connecting statiqns of the second type to stations of the first type and stations of the first type to others of the same type, circuits controlled by said switch means at stations of the first type for selectively connecting the in-. terstation circuit associated with the station to the signal producing means or to the communication direction control switch at the station, and
means including switches at stations of the second type for connecting the receivers thereat to I tions of a type eachhaving a receiver utilizable also as a microphone, the combination including. si nal producing means and switch means at stations of the first type, interstation circuits individual to stations of the first type connecting stations of the second type to stations of the first type, circuits controlled by said switch means at stations of the first type for selectively connecting the interstation circuit associated with the station to the signal producing means or to the communication direction control switch at the station, and means including switches at stations of the second type for connecting the receivers thereat to said interstation circuits and completing circuits through said signal producing means and receiver to give an audible signal at both types of stations when said switch means at stations of the firsttype connect the interstation circuit individual thereto to the signal producing means thereat.
' to said signal producing means or to said communication direction control switch, a station selector switch at the first station for connecting said communication direction control switch to said first interstation circuit, and means including a switch at the second statidn normally connecting said receiver to said first interstation circuit and operable to complete a circuit through said second interstation circuit, the signalproducing means at the first station and the receiver at the second station to. give an audible signal at both stations when said switch means at the first station connects the second interstation circuit to said signal producing means.
assacvs also as amicrophone, the combination including, signal producing means and switch means atstations or the first type, combined signaling and communication circuits individual to stations of the first type connecting stations of the second type to stations of the first type and stations of the first t to others of the same type, com- 8. In a communication, system of the loud.
speaking type including one or more stations 01 a type each having a receiver utilizable also as a microphone, an amplifier and a communication direction control switch and one or more stations oi a type each having a receiver utilizable munication circuits between stations 0! the first and second types, circuits controlled by said,
station to the signal producing means or to the communication direction control switch at the station, station selector switches at stations of the first type for connecting the communication direction controlling switches thereat to said communication circuits, and means including switches at stations of the second type normally connecting the receivers thereat to their respective communication circuits and operable to complete circuits through said combined signaling and communication'circuits, signal producing means at stations of the first type and the receivers at stations at the second type to give an audible signal at both types of stations when said switch means at stations of the first type connect the combined signaling and communication circuit individual thereto to the signal producing means thereat.
RICHARD H. CAMPBELL.
US453342A 1942-08-03 1942-08-03 Communication system Expired - Lifetime US2339678A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2500141A (en) * 1946-11-09 1950-03-07 Operadio Mfg Company Intercommunication system
US2536820A (en) * 1948-09-17 1951-01-02 Prahm Louis Two-way communication system
US2547854A (en) * 1948-02-06 1951-04-03 Webster Electric Co Inc Intercommunication apparatus
US2573257A (en) * 1947-02-24 1951-10-30 Cornell Dubilier Electric Combined radio and intercommunicating set

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2500141A (en) * 1946-11-09 1950-03-07 Operadio Mfg Company Intercommunication system
US2573257A (en) * 1947-02-24 1951-10-30 Cornell Dubilier Electric Combined radio and intercommunicating set
US2547854A (en) * 1948-02-06 1951-04-03 Webster Electric Co Inc Intercommunication apparatus
US2536820A (en) * 1948-09-17 1951-01-02 Prahm Louis Two-way communication system

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