Current supply circuit

Details Current supply circuit Current supply circuit

1987-03-12

1988-04-12

Ng, Jin F.

Telephonic communications

Subscriber line or transmission line interface

Network interface device

379324, H04M 1900

Patent

active

047379880

ABSTRACT:
A current supply circuit for supplying a speech current via subscriber's lines to a telephone set, in which a pair of constant-current circuits, each so constituted as to hold the potential between the base and the emitter of a control transistor therein to be consant, is connected across the subscriber's lines so that the control transistors are connected in series to a DC power source. A constant-voltage circuit is connected across the bases of the control transistors for making the voltage of the base-emitter paths of each of the control transistors to be constant. At least one of the constant-current circuits may be connected across the subscriber's lines via a light emitting diode of a photo coupler.

REFERENCES:
patent: 3916110 (1975-10-01), Lee et al.
patent: 4203009 (1980-05-01), Tattersall
patent: 4525602 (1985-06-01), Robra et al.

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