| 摘要 |
PROBLEM TO BE SOLVED: To carry on a service without interruption of a line having no fault without affecting it by detecting the faults for every line and performing the switching between the working and standby systems. SOLUTION: An external package 31 includes a receiving main signal output control circuit 33, which inputs plural switch changeover signals 5 received from a working package 1, plural switch changeover signals 25 received from a standby package 21 and plural switch changeover signals 32 received from the outside for every line and then outputs a main signal output control signal 7 supplied to every line of the package 1 and a main signal output control signal 27 supplied to every line of the package 21. Then line fault detection circuits 203 and 210 monitor the presence or absence of faults for every line. If a fault is detected, the signal 5 or 25 is outputted to switch the package 1 to the package 21 for only the faulty line. |
