Telephone subscriber circuit

Details Telephone subscriber circuit Telephone subscriber circuit

1987-05-18

1990-04-03

Ng, Jin F.

Telephonic communications

Subscriber line or transmission line interface

Network interface device

379405, 379398, H04M 1900

Patent

active

049146939

ABSTRACT:
A telephone subscriber circuit of a telephone exchange comprising active circuit elements with a capacitively-complex input impednace, wherein the signal which is to be transmitted from the exchange to the subscriber is amplified by two operational amplifiers operating in push-pull and is fed via two coupling arms, formed by a series arrangement of a capacitor and a resistor, into the subscriber loop which is itself supplied with d.c. current via two supply resistors. The subscriber circuit in accordance with the invention serves as a compensation network which directionally isolates the signals of the two speech directions and which includes two arms via which the symmetrical subscriber signal is supplied to a subscriber amplifier. In accordance with the invention the entire complex input impedance is sub-divided into a complex and a real component. The complex component serves as a coupling arm which supplies the LF-signal which is to be transmitted and which blocks the d.c. current from the operational amplifiers. The real component serves to supply the supply d.c. current.

REFERENCES:
patent: 3855430 (1974-12-01), Colardelle et al.
patent: 4053722 (1977-10-01), Nahay
patent: 4283604 (1981-08-01), Chambers, Jr.
patent: 4287393 (1981-09-01), Revekamp
patent: 4387277 (1983-06-01), Giles et al.
patent: 4472608 (1984-09-01), Beirne

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