| 摘要 |
PROBLEM TO BE SOLVED: To secure a transmission line between terminals even when abnormality occurs in a state of power supply to a transmission line switching device itself. SOLUTION: A power supply monitoring part 115 inside a transmission line switching device 11 monitors whether power is supplied from a power source 15 to the transmission line switching device 11 or not and when power is supplied, respective bypass line switching parts 116-1 to 116-6 are switched to a direction A but when power supply is cut off, the respective bypass line switching parts 116-1 to 116-6 are switched to a direction B. Thus, signals on a transmission line #1 are connected through bypass lines 117-1 and 117-2 to a terminal 13 on the side of a present station and terminal 14 on the side of an opposite station. Therefore, even when power supply to the transmission line switching device 11 is cut off, the transmission line between the terminal 13 and 14 is secured.
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