Ringing circuit for telephone subset, designed as an integrated circuit

摘要

This ringing circuit detects the presence of the ringing signal on the subscriber line by means of a first circuit for detecting transition of the same direction in the ringing signal and of a second time measuring circuit for defining a validity window for the occurrence of a transition of desired direction and for providing a ringing control signal when the ringing signal is recognized. The ringing circuit is supplied by rectified AC ringing signals wherein a sufficient-voltage detection circuit is provided to authorized the operation of the ringing circuit.