Telephone line interface circuit

Details Telephone line interface circuit Telephone line interface circuit

1995-04-11

1997-03-04

Matar, Ahmad F.

Telephonic communications

Subscriber line or transmission line interface

379394, H04M 1900

Patent

active

056087950

ABSTRACT:
A telephone line interface circuit has a transmit path for coupling to a telephone line and a receive path for coupling to the telephone line (2). The transmit path includes a first amplifier (A1) having an output for coupling to the line (2), a first input for receiving a signal to be transmitted and a second input for receiving a first sum signal made up of a.c. and d.c. line voltage signals plus a.c and d.c. line current signals. The feedback loop thus described has sufficient loop gain to constrain the first sum signal to be substantially equal to the signal at the first input. The receive path includes a second amplifier (A4) having a first input for receiving the first sum signal, a second input for receiving substantially twice a second sum signal made up of the a.c. and d.c. line current signals plus the d.c. line voltage signal/and an output for providing receive signals. The circuit thus presents a predetermined impedance to the telephone line (2) and also provides hybrid balance when the impedance of the line (2) is substantially equal to the predetermined impedance.

REFERENCES:
patent: 4796295 (1989-01-01), Gay
patent: 4982426 (1991-01-01), Jakab
patent: 5014305 (1991-05-01), Moisin
patent: 5138658 (1992-08-01), Carter
patent: 5274704 (1993-12-01), Jakab
patent: 5323460 (1994-06-01), Warner

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