US2217497A - Switching scheme - Google Patents

Description

Get. 8, 1940. H. R, SHAW SWITCHING SCHEME Filed Ndv. 2, 193a AMPLIFIER COMMON TALK AND LISTEN Inventor: Huber-t R. Shaw HI Attorney.

Patented a. a, 1940 PATENT OFFICE swrrcnmo SCHEME Hubert R. Shaw, Bridgeport, Conn., assignor to General Electric Company, a. corporation of New York Application November 2, 1938, Serial No. 238,415 3 Claims. (01. 179-1) My invention relates to communication systems and particularly to such systems as are used for interofiice communication, public address, etc.

In such systems commonly an amplifier is em- 5 ployed which is alternately reversed in its connections to amplify signals from either of two signal stations and to transmit the amplified signals to the other station.

One object of my invention is to provide such a system having means to prevent regeneration of said amplifier due .to any coupling between conductors which are connected respectively to the input and output of said amplifier and which may be close to each other as in twisted lines in any practical installation of the equipment.

Another object of my invention relates to such a system employing such means for preventing regeneration in which means are also employed to prevent extraneous noises at the location of any station from being reproduced at a different station when the system is not in use.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing in which the single figure represents an embodiment of my invention.

Referring to the drawing I have shown at I a central station, at 2, 3, 4, and 5 a number of outlying stations, and at 6 an amplifier, together with 85 means whereby the operator at station I may call any of stations 2, 3, 4, and 5 through said amplifier, and whereby he may be called through said amplifier from any of said stations 2, 3, 4, and 5. This means comprises a plurality of switches including a talk-listen switch I located at the central station I and also a talk-listen switch 8 located at each of the other stations.

The talk-listen switch I at the central station I comprises a plurality of stationary contacts 9,

III, II, l2, l3, I4, and I5, mounted upon a stator l6, and a plurality of conducting segments 20, 2|, and 22, mounted upon a rotor 23. This rotor may be a suitable non-conducting disk upon which the 50 segments are mounted and which is rotated about an axis by means of a handle 24 movable between two positions as shown in the drawing. The talklisten switches 8 of the stations 2, 3, 4, and 5 are simple double-throw switches which are arranged 55 to connect the loud speaker between the common conductor 21 and either of two conductors 25 or 26 extending to each'station.

The stations I, 2, 3, 4, and 5 may all comprise simple loud speakers preferably of the dynamic type having permanent magnets 0r field coils. One side of all these loud speakers is connected to a common, or ground conductor 21, and to one side of the input transformer 28 of amplifier 6 and to one side of the output transformer 29, of amplifier G, the respective switches l and 8 being shown on the opposite side of the various circuits.

At 30 is a selector switch which may be of the ordinary so-called Yaxley construction comprising a plurality of wafers, each wafer having a number of stationary contacts and rotating conducting segments cooperating therewith, one wafer 3| being provided for conductors 25 extending to the different outlying stations, and. the other wafer.32 being provided for conductors 26 extending to the different outlying stations; By means of these switches as will presently be explained, any one, or all of-the outlying stations 2, 3, 4, and 5 may be connected by the operator at station I for communication with the central station I.

The rotor of the switch 30 is also provided with a member 35 which in one extreme position of the switch engages a switch member 36 arranged in the power supply circuit 31 for the amplifier 3,

thereby interrupting the supply of power to that ampl er.

Having thus indicated the general nature of the equipment to which my invention pertains I shall -now describe ,the various circuits employed in greater detail by reference to its operation. It will be observed that with the switches in the position shown the loud speaker I is connected directly across the secondary winding of transformer 29; this circuit comprises loud speaker I, stationary contact i5, segment 22, stationary contact I4, secondary winding of transformer 29 and ground, or common conductor 21, back to the loud speaker.

It will also be observed that with the switches in the position shown, although station i is connected for listening, no currents generated by reason of noise in the localities of stations 2, 3, 4, and 5 or otherwise, are transmitted to the input of the amplifier I for amplification thereby, and hence produce no disturbance in the station I. This'is by reason of the fact that the circuit of conductors 26 for stations 3, 4, and 5 are all open at segment 38 of water 32 of switch 30, and the circuit of conductor 26 for station 2 is also open at segment 2| of switch I.

With the switch 30 in the position shown the operator at stations 3, 4, and is incapable of callingstation; I The operator at station 2, however, may call station I by moving switch 8 to the left and speakinginto his loud speaker. The circuit for the loud speaker of station 2 extends from ground through ground conductor 21, loud speaker 2, switch 8 in its left-hand-position, conductor 25 of station 2, segment 33 of switch 30, contact 40, conductor 4|, stationary contact II, segment 20, and stationary contact III of switch I, conductor 42 and primary winding of input transformer 28 to ground. These currents are of course amplified by amplifier 5 and supplied to station I.

The. operator at station I may now answer the call by operating his switch Iv to the opposite, or talk, position which is the dotted line position of handle 24 shown in the drawing. In this position the conducting segments 20, 2I, and 22 are rotated counterclockwise by the distance equal to the space between two adjacent contacts. In this position conductor 43 of station I is connected through stationary contacts I4, segment 22 and stationary contact I3 to conductor 4| and thence through stationary contact 40, segment 38 and stationary contact 44 of switch 3l'to conductor 25 of station 2 with which conductor switch 8 is now in engagement. The output currents from the amplifier 5 are thus transmitted to the loud speaker 2. At the same time loud speaker I is connected to the input of the amplifier through stationary contact 9, segment 20 and contact ID of switch I, and conductor 42 to the primary winding of transformer 28. Thus any words spoken by the operator at station I are heard by the operator at station 2.

During the subsequent conversation it is necessary for the operator at station I to alternate switch I between its talk and listen positions as he alternately talks and listens. The switch 8 in the outlying station, however, may remain in its left-hand position throughout the conversation.

If, with the equipment in the position shown in the drawing, the operator at station I desires to call any of the stations 2, 3, 4, and 5 he operates the switch 30 to the position corresponding to the station to be called and the switch 24 to the talk position and then speaks 'into the loud speaker. His loud speaker is then connected to the input of the transformer through stationary contacts 9 and III of switch I. The output of the amplifier is connected through conductor 43, stationary contact I4, segment 22, and contact I3 of switch I, thence through stationary contact II, segment 2I and contact I2 of switch 1, conductor 45, stationary contact 46 and segment.

and that one of the other stationary contacts with which it may be in engagement of switch '32 to conductor 26 of the called station. Thus the words spoken into the loud speaker I are heard by the operator at the called station.

The operator at the called station then moves his switch 8 to the left and answers into his microphone.

It will .be seen that the loud speaker at station by moving its switch I to the talk position. In this position the subsequent conversation may be carried on without further manipulation of switch 8.

All of stations 2, 3, 4, and 5 are connected to the system by means of switches 3I and 32 in exactly the same way as that shown on the drawing for station 2 when switches 3| and 32 are moved in the counterclockwise direction to corresponding positions. If this switch be moved in the counterclockwise direction through the space of one contact then all of these stations are connected together; that is, all of the conductors 25 of the various stations are connected together by segment 49 of switch 3I and all conductors 26 are connected together by segment 38 of switch 32, all of conductors 25 are then also connected to switch I through segment 39, stationary contact 40, and conductor M and similarly all of conductors 25 are connected to switch I through segment 41, contact 46 and conductor 45. Thus, if the operator at station I operates his switch to the talk position and speaks into the loud speaker his words are reproduced at all of the outlying stations. Hall of the operators at the outlying stations operate their switches to the left they may all talk with the central station as in conference telephony.

The conductors 25, 26, and 21 which exten to the outlying stations may, of course, be twisted together or in cable form. With the circuits arranged as described, no regeneration of the amplifier is produced by reason of conductors connected to the input and outlet circuits but which are twisted together, or lie in proximity to each other, throughout any considerable length extending to a distant station. The switch I and the conductors 42 and 43 as well as loud speaker I may all be arranged within the housing of amplifier 5 and thus there is no appreciable coupling between the output and input circuit of the amplifier in these conductors.

All of conductors 25 are connected to conductor 21 at their remote ends by resistors 45. These resistors have such a value as to load the line and reduce pick up of noise and disturbing voltages therein.

While I have shown particular embodiments of my invention it will, of course, be understood that I do not wish to be limited thereto, since differ-' ent arrangements both in the circuit arrangement and the instrumentalities employed may be made without departing from the spirit and scope of my invention. I, therefore, contemplate by the appended l-aims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new anddesire to secure by Letters Patent of the United States is:

1. In combination, a pair of intercommunicating stations, an amplifier at one of said stations, means to connect said amplifier for transmission from either of said. stations to the other, said means comprising double-throw switches in each station, each ofsaid switches being arranged in one position to' connect the respective station to one conductor for talking thereover and in the other position to connect it to another conductor for listening thereover, said conductors connecting said amplifier with said switches, and switching means to isolate any conductor extending between said stations connected to the input of said amplifier from any conductor extending between said stations connected to the output of said amplifier thereby to avoid feed-back from the output of said amplifier to the input thereof.

2. In combination a pair of intercommunicating stations, an amplifier, common, talk and listen conductors, extending from said amplifier to each of said stations, the listen conductor of one station being connected to the output of said amplifier and the listen conductor of the other station being open circuited at said one station, and the talk conductors being connected to the input of said amplifier, each station being normally connected between the respective common and listen conductors and having switching means to disconnect it therefrom and to connect it between its common and talk conductors, and means in said one station to connect the output of said amplifier to the listen conductor of the other station whereby regeneration of said amplifier is not produced by reason of coupling between the talk and listen conductors of said other station.

3. In combination a pair of intercommunicating stations, three conductors joining said stations, an amplifier in one of said stations, said 5 one station being normally connected across the output of said amplifierand the other station being normally connected between two of said conductors, one of which is grounded and the other of which is disconnected from said ampli- 10 fier, means to connect said other station between said grounded conductor and a third of said three conductors, said third conductor being connected to the input of said amplifier, and means at the one station to connect that station across 15 the input to said amplifier and to connect the output of said amplifier to said other of said three conductors.

HUBERT R. SHAW.

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