Bell Telephone Laboratories

Michael W Leibowitz

Karl R Wittig

Alan M Gordon

Gerry C Balzer

There is disclosed a line circuit for establishing a hold condition on a communication line, extending between a switching machine and a key telephone station, during an open switching interval (OSI) when no current flows on the communication line. The control signal required to enable the hold circuit is arranged to be time dependent. For a fixed time interval, which bridges the OSI period, after the telephone station answers a ringing line a hold condition is enabled (402) exclusively by a control signal on the A lead from the station. This time dependent hold enable arrangement permits a hold capability during an OSI condition. After this time interval elapses (403) a hold condition is enabled by (404) a joint signal condition on the A lead and a current continuity condition on the communication line.

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Charleston, SC, United States of America

Michael W Leibowitz