| 摘要 |
<p>PURPOSE:To automatically switch the period of a mask signal by discriminating pseudo-synchronism or not with respect to an initial alarm mask circuit of multiple synchronous detection which detects synchronism of plural highways in time division. CONSTITUTION:One of plural highways 1-1 to 1-n is successively selected by a selector 2 and is connected to a synchronizing part 3 to detect and protect the synchronism. The phase of a synchronizing pattern detection signal due to preceding synchronizing pattern hunting and that due to present synchronizing pattern hunting in the synchronizing part 3 are compared with each other by a comparing part 5. If this comparison results in coincidence, a first mask signal from a mask signal generating part 4 is selected and outputted by a selector 6; but otherwise, a second mask signal from the mask signal generating part 4 is selected and outputted by the selector 6, and a step out signal in the initial state is masked by an inhibiting circuit 7.</p> |
