| 摘要 |
<p>PURPOSE:To quickly restore a synchronized state when a pseudo synchronizing state is set, by counting synchronization error pulses and forcibly clearing a synchronization protecting circuit when the pulses are counted more than the prescribed number of times within a fixed time. CONSTITUTION:Frame synchronizing error pulses in a pseudo synchronizing state are inputted to a synchronization protecting circuit 10 and counting means 12. When the count value of the synchronizing error pulses of the counting means 12 exceeds a set value in a prescribed time fixed by a timer 14, a signal is outputted to a synchronization protecting circuit clearing means 16 to forcibly clear the circuit 10 so as to set a hunting state again and a synchronizing state is restored. Since the circuit 10 has a prescribed number of protecting stages, the re-hunting state is not set unless the synchronization error pulses are continuously inputted for the prescribed number of times and a state where the pseudo synchronizing state is continued for a long time may be occurred. In order to prevent the occurrence of such state, the re-hunting state is forcibly set by means of the above-mentioned circuits so that the synchronizing-state can be quickly restored.</p> |
