| 摘要 |
<p>PURPOSE:To provide a number of protection stages adapted to a transmission error rate by counting the number of times of coincidence between reception frame synchronizing patterns in a certain period and a determined specific pattern and that of disaccord and giving the number of backward protection stages and the number of forward protection stages corresponding to the number of times of coincidence and that of disaccord to a backward protection counter and a forward protection counter. CONSTITUTION:A coincidence detecting circuit 3 detects whether the frame synchronizing pattern of a reception input 1 and the determined specific frame synchronizing pattern coincide with each other or not at the time of generation of a pulse in every frame period of a frame synchronizing pulse 2, and the output is outputted to a line 4 in case of coincidence but is outputted to a line 5 in case of disaccord. A coincidence, number counter 8 and a disaccord number counter 9 are reset by the pulse of a counter synchronizing signal 7 and count the number of times of coincidence and that of disaccord till the next reste and output the counted value of the number of coincidence and that of disaccord to lines 10 and 11 respectively. A protection stage number table 12 outputs the number of backward protection stages and that of forward protection stages to lines 13 and 14 based on the number of times of coincidence and that of disaccord. The number of backward protection stages and that of forward protection stages corresponding to counted values are given to a backward protection counter 18 and a forward protection counter 19 through a register 15 by the protection stage number table 12.</p> |
