Subscriber's circuit with a symmetrical amplifier

Details Subscriber's circuit with a symmetrical amplifier Subscriber's circuit with a symmetrical amplifier

Filed on

1978-10-10

Date issued

1980-07-08

Examiner

Brown, Thomas W.

Other Related Categories

179 84A, H04M 322

Type

Patent

Status

active

Patent number

042118964

Description

ABSTRACT:
Subscriber's circuit for connecting a subscriber's line to a telephone exchange, comprising a symmetrical amplifier which is arranged between two feed points having different potentials, the amplifier circuit having two input terminals and two output terminals, each one of the output terminals being connected to a wire of the subscriber's line and each input terminal of the symmetrical amplifier circuit being connected to an output of an associated digital-to-analog converter an input of which is connected to the one or to the other feed point by means of a change-over switch, the change-over switches being controlled in phase opposition by a binary digital signal which characterizes a voltage desired for the subscriber's line and which is derived from a digital signal generator under the control of the telephone exchange.

REFERENCES:
patent: 3808378 (1974-04-01), Hernandez
patent: 4065640 (1977-12-01), Rouiller
patent: 4132864 (1979-01-01), Feng
"The 12 kcs Call Charge Indicating System", P. Guyer, Landis & Gyr Review 19 (1972)2.

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