| 摘要 |
PURPOSE:To prevent the fault of an auxiliary system from being latent by checking whether a test cell is detected in a prescribed time by a second extraction circuit or not, detecting the fault in the channel of a living system, comparing the test cells of the living and auxiliary systems extracted by a first extraction circuit and detecting the fault of the auxiliary system. CONSTITUTION:By a second extraction circuit 19 arranged between a switching circuit 18 and an outgoing line 21, the fault in a channel 14 of the living system is detected according to whether the test cell is detected in the prescribed time or not. The test cells of the both systems extracted by first extraction circuits 15 and 16, which are arranged in the output sides of both the living system and auxiliary system and extracts the test cell, are compared and logic is obtained with the detected result of a detector 22. Then, the fault in a channel 13 of the auxiliary system is detected. Thus, in the system having the auxiliary system for corresponding to the fault of a hardware, the normality of the auxiliary system can be confirmed.
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