Automatic telephone number identification circuit

Details Automatic telephone number identification circuit Automatic telephone number identification circuit

1975-07-16

1977-01-04

Claffy, Kathleen H.

179 18FH, H04M 1536

Patent

active

040015122

ABSTRACT:
An identification circuit, which is useful in a communication system comprising a plurality of remote stations and one central station, for automatically distinguishing between two remote stations in the system which are common to a single communication line pair connection to the central station. A two-party telephone line in a telephone network is an example of such a system. The identification circuit includes a ground mark circuit which in turn includes sufficient dc resistance to provide an electrical imbalance on the communication line pair when the ground mark circuit is connected between the communication line pair and ground. A sensing circuit and a control circuit are also provided, with the sensing circuit being responsive to a dc current in a portion of the communication line pair connected to a selected one of the two remote stations to energize the control circuit, which is in turn operable to connect the ground mark circuit between the communication line pair and ground. The electrical imbalance thereby appearing on the communication line pair is detectable by the central station.

REFERENCES:
patent: 2277623 (1942-03-01), Allen
patent: 3278687 (1966-10-01), Everett
patent: 3339028 (1967-08-01), Taugner

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