Bell Telephone Laboratories

William Andrew Huryn

Alan M Gordon

Ronald Joseph Angner

Wayne Jay Egan

There is disclosed a protective coupler for use with key telephone line units (KTU) to provide isolation between the terminal equipment and the central office line. The protective coupler plugs onto the KTU option socket and establishes a dielectric barrier to protect the system from possible overvoltages, guarantees a balanced termination, and meets leakage requirements while remaining operable to pass control and voice signals between the network and station equipment. The central office side of the barrier contains a current sink for control purposes as well as a gain compensation circuit to adjust for varying distances from the central office.

Key telephone unit protective coupler

A multilink intercom is disclosed having hands free answer capability on each of the links. The circuit is arranged for use with the standard key telephone system and is station oriented such that concurrent hands free communication connections can be utilized on each of the links. A common selector is used to serve all of the links and the hands free detector and control circuitry at each station is shared among all of the intercom lines at that station.

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Bricktown, NJ, United States of America

William Andrew Huryn