| 摘要 |
<p>PURPOSE:To detect the continuity of the synchronous pattern detecting signals with simple circuit constitution by selecting one bit of the output of a shift register or the output of a logic circuit to output it as the result of decision showing whether the synchronization is fixed or not. CONSTITUTION:A protection stage counter circuit consists of a shift register 1, AND circuits 2-8, and a selector 10 and secures the front or back protection when the fixed state of synchronization is decided based on a synchronizing pattern detecting signal. The register 1 converts the synchronizing pattern detecting signals SI (serial signals) into the parallel signals Q0-Q7 and outputs them. The AND circuits 2 and 3 secure an AND between the output signals Q0 and Q1 and an AND between the output of the circuit 2 and the output signal Q2 respectively and input these ANDs to a selector 10. The selector 10 selects either one of the signal Q0 and outputs of circuits 2-8 and outputs it as a signal Y which shows the result of decision showing whether the synchronization is fixed or not. Thus it is possible to detect the continuity of signals SI and to decide the fixed state of synchronization.</p> |
