| 摘要 |
PROBLEM TO BE SOLVED: To prevent stop of signal distribution in the case of a composite fault by retrieving a path for signal distribution from each path distributing a signal in the case of a fault in both active and standby signal distribution systems. SOLUTION: A primary rating means 53 receives monitor information of a system A distributing an active signal and a system B distributing a standby signal with outputs IN-0, IN-1 of OR circuits 51, 52. When the system A has no fault, no switching is made and when the system A is faulty and the system B has no fault, the system B is selected. Furthermore, when both the systems A, B have a fault and the switching by the primary rating means 63 is not made immediately, the secondary rating is set. In the secondary rating, a fault is detected from each path distributing a signal to retrieve a path able to distribute the signal and when a path able to distribute the signal is found out, the path is selected. Thus, when any signal distribution path is left, the supply of signal is not stopped. |
