SYNCHRONIZATION DETECTING CIRCUIT ON DIGITAL SIGNAL TRANSMISSION

摘要

PURPOSE:To shorten the detecting time for synchronization and to prevent the actuation of a muting circuit for a short time, by outputting the synchronization detecting signal through a time constant circuit. CONSTITUTION:The reproduction digital signal synthesized with a block unit is supplied to an input terminal 1 of a synchronizing signal detecting circuit 11. Then a signal having approximately equal cycle to the signal cycle of a block synchronized in phase with the synchronizing signal in a digital signal is applied to a shift register 12 from the circuit 11. The register 12 shifts successively the received detection signals and supplies them to a gate circuit 14. The circuit 14 produces a detection signal of logic 1 only when the N-bit parallel output of the register 12 is continuously coincident by N times for each block transmission cycle and supplies the detection signal to a time constant circuit 15. The circuit produces a signal which is set at logic 1 when an extremely fixed short time elapses from a time point when the input signal is set at logic 1 and then set at logic 0 when a fixed time elapses after the time point when the input signal is set at logic 0 in the form of a synchronizing signal. This synchronizing signal is outputted through a terminal 16.