SYNCHRONIZATION STATE DETECTION CIRCUIT

摘要

PURPOSE:To prevent erroneous output of a detection signal representing the synchronization state. CONSTITUTION:A timer section 2 outputs a pulse measurement time set by a time base section 1. An out of synchronism pulse counter 3 and a synchronous pulse counter 4 output respectively an out of synchronism signal and a synchronizing signal when a synchronizing signal pulse inputted in response to the frame synchronization state from an input terminal 8 reaches a set measuring time. An N-time count section 5 outputs the synchronizing signal or the out of synchronism signal received in excess of a preset reference number. A count comparator section 6 upon the simultaneous receipt of the synchronizing signal and the out of synchronism signal from the N-time count section 5 outputs the out of synchronism signal with priority. A selection circuit 7 outputs a synchronization state pulse representing out of frame synchronism when the circuit 7 receives no input of the synchronizing signal and the out of synchronism signal from the count comparator section 6.