| 摘要 |
PURPOSE:To ensure highly reliable synchronism inspection in a simple constitution by transmitting a synchronizing abnormal signal to a multi-frame synchronizing means in the timing of the frames set every prescribed number of pieces in case a prescribed bit of one of said frames is equal to '1'. CONSTITUTION:When the synchronism is secured, a received FA signal = 1 passes directly through an AND gate 212-3 and produces a signal x = '1'. An FA synchronism protecting circuit 206 stores (a=1*x=1). When a received FA signal = '1' is detected by some reason for a period up to the next gate signal a='1', a signal x = '0' is obtained in the timing of the gate signal a='1'. Thus the circuit 206 stores (a=1*x=0). Then the circuit 206 decides an FA synchronism step-out state at the time point when the (a=1*x=0) is continuously stored twice and transmits an FA synchronism detecting signal ='0' to show the occurrence of said step-out. An M synchronism detecting action is also carried out in the same way. |
