US1573891A - Gain-controlling circuits - Google Patents

Description

Feb 23 1926.

S. B. WRIGHT ET AL GAIN CONTROLLING CIRCUITS Filed April 30, 1925 v www. A Ni W E f acum u .VII H. D P.

M. l w ls m m O M T m 7 m V BYV Patented Feb. 23, 1926.

UNITED` STATES 1,573,891 PATENT OFFICE.

SUMNER B. WRIGHT, OF EAST ORANGE,

NEW JERSEY, AND JOHN 'I'. SCHOTT, OF

BROOKLYN, NEW YORK, ASSIGNORS T AMERICAN TELEPHONE AN D TELEGRAPB.' COMPANY, A. CORPORATION OF NEW YORK.

GAIN -CONTROLLING CIRCUITS.

Application led April 30, 1925.

To all whom 'it may concern Be it known that ive, SUMxnn B. IVRIGHT and Joris T. Scno'rr, citizens of the United States, residing at East Orange and Brooklyn, in the counties oi Ilssex and Kings and States of New Jersey and New York, respectively, have invented certain Improvements in (tain-Controlling Circuits, ot' which the following is a specification.

This invention relates to telephone transmission circuits and more particularly to arrangements l'or controlling the gain of telephone repeaters.

In certain cases it is desirable to transmit a relativelyY high and substantially constant volume over a transmission circuit from all subscribers. For exan'iplc, in the case of a radio telephone transmitter it is necessary to radiate a practically constant volume in 0 order to lieep the voice currents strong as compared to noise. Since certain subscribers may be connected to such a radio telephone transmitter over long circuits having large losses, while other subscribers may 25 be connected over relatively short circuits, and since regardless ot' the length of the circuit .some subscribers talk much louder ythan others, it is necessary to adjust the gain otan amplifier associated with the radio transmitter for the different conditions met with it' the volume radiated is to be maintained constant. In circuits arranged to meet such a requirement'. some method must he provided to insure that when the circuit is adjusted for a large repeater gain to amplify the weak currents, strong currents such as those put out by operators near the input ot the circuit will not exceed the value for Which the circuit is adjusted, otherwise serious distortion or other harmful effects may occur.

It is one of the objects ot this invention to provide a circuit arrangement whereby when an operator comes in on a circuit of the type above described near the point at which the variable gain repeater is provided, the gain Will be reduced to a value such that the volume of energy re ulting from the operators speaking on the circuit Will not exceed the limiting value for the circuit.

Other and further objects of the invention will be clear from the following detailed description when read in connection Seria No. 27,001.

with the accompanying drawing, the ligure ot which illustrates a circuit diagram embodying the principles of the invention.

Referring to thedrawing, SL represents a subscribers line which may be connected to a four-wire repeater llink comprising paths LE and LIV through the usual hybrid coil l() and balancing network N. The path LIfV includes a transmittingr amplifier AIV and the path LE includes a receiving amplitier AE. The path LIV may be connected to a suitable radio telephone transmitter and the path LE to a corresponding radio telephone receiving circuit. The subseribers line SL is connected to the hybrid coil through a trunk TL and in order that different lines may be connected with the trunk, the line SL and the trunk TI, terminate in jacks J1 and J2 respectively, adapted to cooperate with the plugs P1 and P2 of a toll operators cord circuit.

In order to adjust the gain of the amplifier AIV so that the volume of energy transmitted over the circuit LIV may be maintained at a substantially constant value, a potentiometer ll is associated with the input side of the amplifier. This potentiometer ll may be adjusted by steps determined by the gain control dial GC whose cent acts B to K inclusive are connected to close circuits through individual relays B to K, inclusive. These relays in turn establish connections from various points on the potentiometer il to the amplifier AIV. For simplicity, the relays C to H inclusive and their connections are not illustrated. The gain control dial may be manipulated by a technical operator at a technical operators position. A volume indicator VI is provided on the output circuit of the amplifier AIV to indicate to the technical operator the amount of volume being transmitted from the amplifier.

The technical operator is provided with a cord circuit terminating in twin plugs 1) and PJx adapted to co-operate with twin jacks J., and J4 connected in the trunk TL. The technical operators cord circuit is provided with a telephone operator's set which may be'connected to the cord by means of key K3. 'lhe back plug I),l of the cord may be inserted in the jack J, when the technical operator desires to speak over the line LIV at such times as no line such as SL is connected to the trunk through the toll operators cord circuit. lf, however, such a connection is established with the toll operators cord circuit, the technical operators cord circuit may have its front and back plugs P3 and P4 inserted in the jacks J 3 and J 4 respectively so that the connection will extend through the technical operators cord circuit. A special relay A is provided in the gain control circuit and the circuit of this relay is under the joint control of the key K3. of the technical operators cord circuit and the key K, of the toll operators cord circuit. It either operator goes in on the circuit With a telephone set by operating the key K, or keyK3 as the case may be, the

relay A, which is normally energized When either cord circuit is in use, will be released during the time that the operators tele-- phone set is connected to the cord circuit and will close a circuit for a special adjustment of the potentiometer 1l, which will bring the gain of the amplifier AW down to a point such that When the operator talks, the volume of energy transmitted over the circuit LV will not exceed the maximum limit. At the same time, the relays B to K inclusive are all placed in an inoperative condition so that the setting of the potenti- .ometer 1,1 will not under these conditions be determined by the setting of the gain control dial GC. Y

Further details of the invention will now be clear froma description of the operation 'F which is as follows: The toll operator will establish a connection from a line such as SL to the radio transmitter associated With the circuit LW by inserting'the 'front and back plugs P, and B2 of her toll cord circuit in the jacks J1 and J 2 respectively. A circuit is now established from battery, over the back contact of the relay M, sleeve conductor of the back plug P2, sleeve conductor of the jack J 2, over contacts 15 and 1G of jacks J 3 and J 4 to conductor 17. Relay A, Which has one. terminal of its winding connected to the conductor 17 and the other terminal connected to ground, will be energized and Will open the circuit 18. At the same time, one of the relays B to K inclusive, as determined by the setting of the gain control GC, is energized and connects a point of the potentiometer ll tothe input transformer of the ampliiier AW. As soon as the subscriber begins to talk over the circuit, the volume transmitted from the ampliiier AW will be indicated by the volume indicator Vl so that the technical operator may adjust the gain control dial GC to bring the volume to the desired level. For example, it the subscriber talks in a weak voice over a long telephone line the volume indicated by the volume indicator Vl will be quite low and the gain control dial will be set upon its high contact B,

thereby closing a circuit from ground through the Winding of the relay B to the conductor 17. The relay B is energized and connects the upper terminal of the input Winding of the transformer over the front contact of the relay B to the upper terminal of the potentiometer 1.1. lf, however, the volume of current incoming lrom'the line SL should be greater, the gain control dial might be set to a lower contact, such as J, in which case the relay J would be energized and close the circuit from the input transformer to a lower setting ot the potentiometer. lt will be noted that the circuits of all of the relays A to K inclusive extend over the sleeve conductor ot' the jack J 2 to a battery in the sleeve circuit of the back cord of the toll operators cord circuit.

Suppose now, with the gain control set upon contact B so that the relay B is operated for the corresponding setting of the potentiometer l1, the toll operator should desire to speak over the circuit. The key K1 Will then be actuated to connect the toll oplerators telephone set to the toll cord. e operation of the key vlli, closes a circuit of the relay M associated with the toll cord, which relay in turn opens the sleeve connection to the QA-volt battery. T his removes battery from the sleevev conductor ot' the trunk and consequently from the conductor 17. The relay B or any other relay of the set of relays B to l inclusive will be deenergized so that these relays no longer control the setting of the potentiometer. rlhe relay A will also be deenergized at the same time and will close a circuit over its back Contact from the upper terminal of the input transformer, through the conductor 18, to a point on the potentiometer ll such that the volume ot energy due to the operators speech as indicated on the volume indicator VI will not elvceed the limits for the. circuit. lf at a time when the connection through the operators toll cord is not establisln-d` the technical operator should desire to speak over the circuit, the technical operator will insert the back plug B, into the jack J4, thereby opening the connection to the sleeve conductor of the jack J2 at the contact 1G and connecting the tip and ring conductors leading from the hybrid coil to the tip and ring conductors of the technical operator-s cord circuit. The conductor 17 is also connected over the sleeve conductor ot the twin jack and the sleeve conductor of the twin plug and thence over a contact of the key K3 and a contact ot the relay l, to a Q-l-volt battery. A circuit is thus established troni the Q4-volt battery for one ot the relays l to l( inclusive, depending upon the setting oi the gain control dial at that time. lihen the operator throws the talking key liz., 1o connect the telephone set to the technical operators cord circuit, the battery convce nection tothe sleeve conductors of the twin plug P4 is opened at contact 19, thereby releasing the relay of the group ll to K inclusive which is atthe moment actuated t-o open the potentiometer connection then established. At the same time thel relay A is deenergized and establishes the. normal potentiometer connection through the conductor 18, bringing the volume level back to the level desirable for the conreisation oi an operator.

It, when a connection is established through the toll operators cord circuit', the technical operator desires to come in on the circuit, plugs 1) and I), of the technical operators cord circuit will be inserted in the jacks J3 and J,l respectively. The normal tip and ring connections through the twin jacks J?, and J,t are now broken and the tip and ring connections are established through the technical operato1"s cord circuit. The connection from the sleeve of the jack J2 to the conductor 17 is also broken and conductor 17 is connected over the S contacts of the twin jack J ,E and the corresponding S contacts of the twin plug P, and over the contact 19 ofthe key K3 to the armature of the relay L. A circuit is also com-- pleted from the AZ4-volt battery through the winding of the relay L, contact RS of the twin plug P3 and corresponding contact of the jack J3 to ground. The relay L being energized, the circuit previously traced from the conductor 17 to the armature of the relay L is extended over the TS contacts ot the twin plug P3 and twin ackJ, over the sleeve contact of the jack J2 and plugP2,and thence over the back Contact of the relay M to the 2t-volt battery connection at the toll operators position.

It will thus be seen that the controlling circuit for the relays A to K inclusive extends through both cord circuits. Therefore, it' the toll operator throws her key K, the relay M will be operated to release all ot the. relays A to K inclusive, thereby breaking the setting of the potentiometer as determined by the gain control dial and establishing a setting of the potentiometer over the conductor 18. Similarly, if the technical operator throws the key K,s the relay controlling circuit will be opened at contact 19 with the same result. The operation of the key K3 or key K, as the case may be docs not open the through connection as established by the cord circuits.

It will, of course, be obvious that any number of sets of twin jacks similar to J 3 and J4 may be provided in the circuit at different positions and by using cord circuits at these points similar to the technical operators cord circuit any desired number of operators may independently come in on the circuit in the manner above described. This is for the reason that each cord circuit of the type shown at the technical operator`s position completes a sleeve connection over the talking keys of successive cords in series so that the operation ot any key will set the gain control circuit to normal without interrupting transmission.

It will be obvious that the general principles herein disclosed may be embodied in many other organizations widely differentf'rom those illustrated without deiiartinpll from the spirit of the invention as defined in the appended claims.

lVhat is claimed is:

l. In a signaling system, an amplifier, means to control thc gain of said amplifier, a. cord circuit for establishing connections to said amplifier, an operatorlsl telephone set associated with said cord circuit, and means whereby when said operator-s telephone set is connected in circuit the existing gain adjustment of said amplifier will be disabled and the amplifier will be adjusted to the requirements of said operators telephone set. y

2. .In a signaling system, an amplifier, a potentiometer having variable settings for controlling the gain of said amplifier, a cord circuit'. for establishing connections to said amplifier, an operators telephone set associated with said cord circuit, and means whereby when said operators telephone set is connected in circuit the existing potentiometer connection is disestablished and a normal potentiometer setting dependent upon the requirements of said operators telephone set will be established.

3. In a signaling system, an amplifier, meansfor variably adjustingr the gain of said amplifier, a plurality of cord circuits connected in tandem to establish connections to said amplifier, operators telephone sets for each cord circuit, and means whereby when the operators telephone set of any cord circuit. is connected in the circuit the existing gain adjustnnmt of said amplifier will be automatically disestablished and a gain adjustment conformingto the requirements of the operators telephone set will be automatically established.y

4. In a signaling system, an amplifier, an adjustable potentiometer for varying the gain of said amplifier, a plurality ot cord circuits adapted to be connected in tandem to establish connections to said amplifier, operators telephone sets for each cord circuit, and means whereby when an operators telephone set is connected in circuit, the existing setting of the potentiometer will be automatically disestablished and a setting corresponding to the requirements of the operators telephone set will be automatically established.

5. In a signaling system, an amplifier, a potentiometer, an adjustable switch for variably setting said potentiometer to adjust the gai-n of said amplifier, a cord eircuit for .establishing connections to said amplifier, an opcrators telephone set associated with such cord circuit, means Whereby when the operators telephone set is connected in circuit the settingof the potentiometer determined by said switch Will be automatically disostablisl'ied and the potentiometer will be automatically set to produce a gain in accordance with the requirements of said operators telephone set.

6. In a signaling system, an amplifier, an adjustable potentiometer for controlling the gain of said amplifier, a gain control switch f adapted to be variably set, a plurality of relays selectively energized in accordance with the setting` of said switch, each relay controlling an individual setting ot said pot-entiometer, an additional relay controlling the normal setting of said potentiometer, a cord circuit for establishing connections to said amplifier, an operators telephone set associated with said cord circuit, and a circuit for said relays extending to said cord circuit and controlled thereby whereby when the operators telephone set is 'connected in circuit the circuit of said relays Will be changed to disestablish the potentiometer setting determined by the selective relays and to establish the normal setting controlled by said additional relay.

In testimony whereof, We have signed our naines to this specification this 29th day ot April, 1925.

SUMNER B. VRIGHT. JOHN T. SCHOTT.

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