US1519211A - Loud-speaker circuits - Google Patents

Description

w. MARTIN LOUD SPEAKER CIRCUITS Filed Jun 1'7, 1922 INVENTOR. W17: Miriam ATTORNEY time nee le, 1924. v 3

UNITED STATES PATENT OFFICE.

H. MARTIN, OF NEW YORK-, N. Y., ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

LOUD-SPEAKER CIRCUITS.

Application flledJune 17, 1922. Serial No. 568,847.-

k To all whom it may concern:

Be it known that I, WILLIAM H. MARTIN, residing at New York, in the county of Bronx and State of New York, have invented certain Improvements in! Loud- Speaker Circuits, of which the following is a specification. V

This invention relates to improvements in telephone circuits and particularly to the types of circuits suitable for use with loud speaker apparatus.

The field of use for the loud speaking telephone is found to extend, among other things, to announcing systems, phonograplh reproduction, intercommunication, and

giving of public address or other performance. It often happens that in circuits designed for the above purposes, and particularly for the urposes of public address or announcing, t at the loud speaking receiver will be located in relatively close proximity to the transmitter and as a result an acoustic coupling may exist between the receiver and transmitter, which may impress sufficient energy upon the transmitter to cause singing to take place in'the circuit. In general it is the object of this invention to prevent such singing in loud speaker circuits by roviding an additional electric coupling etween receiver and transmitter which is adjusted to neutralize theetlect of any acoustic coupling which may exist between them. Other features of the invention will appear more fully from the detailed description hereinafter given.

' The invention ma be more fully understood from the fol owing description together'with the accompanying drawing in the figure of Which is illustrated a circuit diagram of a loud speaker system embodying the invention.

In the drawmg is shown a transmitter T. The condenser type of transmitter, or any 7 other desired type, may be used. The

transmitter T is included in a transmitter circuit 1 which includes a battery, a winding of. transformer 1, and a series resistance 1' The other winding of transformer 2 is connected to an amplifier circuit, which includes the vacuum tube amplifier A The output of the amplifier is connected through a transformer 3 to a receiver circuit 4, which includes the series resistance r, and the loud speakin receiver .R which is illustrated schematically as it is of a well known type.

If, as often may be the case, the receiver R is su'fiiciently close to the transmitter T,

it may cause the voice waves to be impressed through the air upon the transnntter T and thus cause singing to take place in the circuit. In other words the acoustic coupling) between the receiver and transmitter may e suiliciently great so that, when operating through the amplification in the electrical circuit between the transmitter and the receiver, a flow of energy is I A is connected to a distortion network N. I

The distortion network N is connected to circuit 6 which is bridged across the terminals of resistance r, in the transmitter cireuit 'l. The distortion network N comprises a series and shunt combination of resistance, inductance and capacity, the elements of, which may be varied. With this arrangement the original energy from the transmi tter will be transmitted through the ampliiier A, to the receiver circuit 4: and will actuate the loud speaker R. A. portion-of the sound from ,the loud speaker B may affect the transmitter T and tend to cause a circulation of energy, or singing. However, at the same time a portion of the energy from the receiver circuit will be transmitted over circuit 5, 7 through amplifier A and distortion network N, and over circuit (3 to the transmitter circuit 1. This energy can be made to neutralize the effect of the energy transmitted acoustically and will prevent singing from taking place. The amplifier A and distortion network N obviously must be adjusted differently to meet diil'erent acoustic conditions. The distortion network N needs to be adjusted for both variation of eiiiciency with frequency and phase relation with frequency.

While the arrangements of the invention have been disclosed as embodied in certain s ecific arrangements which are deemed deslrable, they are capable of embodiment in lilil man other types of circuit arrangements without departing from the spirit of the invention as defined by the appended claims.

What is claimed is: 1. circuit including a transmitter and a receiver so arranged that an acoustic coupling exists between said receiver and transnntter, and an electric coupling asso- 'ciated with sa d circuit adapted to neutralize the effect of said coupling, said electric coupling comprising an amplifier and a distortion network and means for adjusting the same.

2. A loud speaker system comprising a transmitter circuit and a receiver circuit, an.

amplifier circuit interconnecting said eiruits, a series resistance in said receiver circuit, a'series resistance in said transmitter circuit, an input circuit associated by a variable connection with first said mentioned resistance, an amplifier in said input circuit, a variable distortion network associated with the output of said amplifier, and a circuit connecting said distortion network to said second mentioned resistance;

3. A circuit including a transmitter and a. receiver so arranged that an acoustic coupling exists between said receiver and transmitter, an electric coupling associated .June, 1922.

WILLIAM H. MARTIN.

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