| 摘要 |
PROBLEM TO BE SOLVED: To transmit information through an auxiliary trunk transmission line on the occurrence of a fault in a trunk transmission line. SOLUTION: Auxiliary transmission lines 11a, 11b that connect its own data transmitter 1ab to other data transmitters 1aa, 1ac when the trunk transmission lines 10a, 10b fail, are connected to auxiliary trunk transmission line ports 5a, 5b. A transmission line fault detection section 6 receives a transmission line state signal 12 from connected trunk line ports 4a, 4b and the auxiliary trunk transmission line ports 5a, 5b and outputs a transmission line fault signal 14. A port switching discrimination section 8 receives the transmission line fault signal 14 and outputs a port switch control signal 15 to a port switch control section 7 on the occurrence of the faulty trunk transmission lines 10a, 10b. The trunk line port switch control section 7 receives the port switch control signal 15 and outputs a trunk line port switch control signal 13 to the trunk line ports 4a, 4b and the auxiliary trunk transmission line ports 5a, 5b.
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