Abstract: A time division switching system is disclosed having a plurality of telephone line circuits and common control circuits for switching calls over a time division communication bus. Ringing loop current detectors are shared by groups of the line circuits for detecting call answer signals during active ringing on a call and for controlling the line circuits to interrupt, or trip, the ringing upon a called party answer. Each group of the line circuits is permanently connected to a ringing current supply via an individual one of the loop current detectors. Each line circuit includes ringing control circuitry operated and released by the common control circuits for connecting ringing current to a called line during an active ringing interval and for disconnecting it during a silent interval of the ringing cycle. The circuitry is responsive to a detection of a called station answer signal by the shared loop current detector for immediately tripping ringing.

Abstract: A time division switching system is disclosed having a plurality of telephone line circuits and common control circuits for switching calls over a time division communication bus. Ringing loop current detectors are shared by groups of the line circuits for detecting call answer signals during active ringing on a call and for controlling the line circuits to interrupt, or trip, the ringing upon a called party answer. Each group of the line circuits is permanently connected to a ringing current supply via an individual one of the loop current detectors. Each line circuit includes ringing control circuitry operated and released by the common control circuits for connecting ringing current to a called line during an active ringing interval and for disconnecting it during a silent interval of the ringing cycle. The circuitry is responsive to a detection of a called station answer signal by the shared loop current detector for immediately tripping ringing.