| 摘要 |
PURPOSE:To prevent a maintenance line from being broken even when frame out of synchronism takes place intermittently by using an cut of synchronism intermission detection means to bring out of synchronization confirming state forcibly if out of synchronism takes intermittently. CONSTITUTION:An out of synchronism intermission detection circuit 128 counts number of intermission times of an out of synchronism confirming signal for a prescribed period and when the number is a prescribed number or over, a forced out of synchronism confirming signal is outputted to a changeover circuit 126 via an OR circuit 127. If the state of out of synchronism confirming takes place intermittently caused due to the degree of attenuation of an optical reception signal, a formed out of synchronism confirming signal is sent from an out of synchronism interruption detection circuit 128 to the switching circuit 126 via the OR circuit 127 to switch the changeover circuit 126 stable to the position of a crock generator 11. Thus, a clock from the clock generator 11 is fed stably to a multiplexer 122 and a frame is generated, then the maintenance line of the succeeding transmission paths is not broken. |
