| 摘要 |
PROBLEM TO BE SOLVED: To attain the proper switching of systems in a duplex system and also to improve the maintenance efficiency of the system without reacting sensitively to the transient errors by discriminating the occurrence of a transmission error when the detected error frequency exceeds a prescribed level. SOLUTION: A main control part fetches the outputs of an error detection part 19 and an error frequency output part 21 via an I/O port 18 and decides whether a communication network has a fault based on these fetched outputs. For instance, the main control part decides occurrence of a fault of the network when the output of the part 19 has an H level with the output of the part 21 set larger than the prescribed value or when the output of the part 19 has an H level with the frequency of output of the part 21 kept higher than a prescribed level set equal to the prescribed frequency respectively. In such a case, a loop interface 12 is controlled via the port 18 and the switching is carried out between the present and standby light transmission/reception parts. |
