| 摘要 |
PURPOSE:To instantly cope with the abnormality of an operational node by operating one of nodes as an operation node and the others as supervisory nodes and allowing the supervisory node to play a roll of the operation node when the operation of the operation node is abnormal. CONSTITUTION:A supervisory node 3a is in standby till a text is received from an active transmission line 1a and a received text is buffered in a RAM 31 and the text is sent to the operation node 3b to discriminate whether or not the text is returned after a prescribed time via a standby transmission line 1b. When no replay comes and the result of collating the returned text is noncoincident, the supervisory node 3a discriminates the operation of the operating node 3b is abnormal, after the operation stop instruction is sent to the operation node 3b to start the operation mode by itself. Thus, when the operation node is abnormal, the supervisory node applies the operating mode in place thereof, thereby coping with the abnormality instantly.
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