| 摘要 |
PURPOSE:To reduce the possibility of misjudgment of a faulty station by reading a digital signal having the same frame constitution as that of an operation mode out of a memory circuit through an intermediate repeater station that detected a circuit fault to transmit said digital signal to a lower station via a transmitter and performing a normal repeating action at the lower station. CONSTITUTION:The inverted parity bits F1, F2... are put into the frame synchronizing signals and an inverted parity bit P is put into the digital signal respectively. A using circuit is switched to a spare circuit after those inverted parity bits are detected. An intermediate repeating station C receives the multi-value QAM modulation wave that is modulated by the digital signal having the same frame constitution as that of an operation mode and therefore can have a normal repeating action. Furthermore the intermediate repeater stations lower than the station C are not displayed at a display part 7 of an end office E since no alarm information is sent to a monitor controller 4. Then only the intermediate repeater station having a circuit fault is displayed at the part 7. This reduces the possibility of misjudgment of a faulty station.
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