Synchronizing circuit for detecting and interpolating sync signals contained in digital signal.

摘要

A synchronous circuit comprises a sync signal detecting circuit (3) connected to receive a digital signal with a plurality of frames each consisting of N bits and containing a frame sync signal to detect the sync signal in each frame, and a sync protecting circuit (5, 6, 8) for producing a sync control signal synchronized with the detection of the sync signal and interpolating the sync control signal every frame when the sync signal is not detected. The sync protecting circuit has a counter (7) for counting the number of frames in which the sync signals are not detected. A circuit (10, 11, 12, 13) is provided to quickly synchronize the sync protecting circuit with the detection of the sync signal by the sync signal detecting circuit in a case where noise is output from the sync signal detecting circuit and then a sync signal is detected after a given value has been counted by the counter (7).