| 摘要 |
PURPOSE:To minutely recognize a faulty location by applying the error detection of a reflected monitoring signal and extracting and collating a monitoring signal to be sent while extracted at the middle-order group at the transmitting and receiving sides. CONSTITUTION:The signal received at an opposite side is reflected and sent again via a standby route, then the signal is demultiplexed into a middle order group monitoring signal 34 at the receiving side by a high-order group demultiplex section 13 and demultiplexed further into a low-order group monitoring signal 35 at the receiving side by a low-order group demultiplexing section 14. One of the low-order group monitoring signals 35 is selected by a low-order group monitoring signal selector 24 and fed to an error detection circuit 25. The error detection circuit 25 discriminates whether or not the signal selected by the low-order group monitoring signal selector 24 is equal to the low-order group monitoring signal 31 generated by the low-order group monitoring signal generating circuit 21 to detect a fault in the standby side route.
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