| 摘要 |
PROBLEM TO BE SOLVED: To provide a means capable of realizing stable monitor control, even when an active line and a spare line switching takes place. SOLUTION: When the active line 20 is switched over to the spare line 21, a monitor control board 17, serving as a host station of a polling/selecting system, temporarily suspends the polling of signal A received from a switch control board 16, until the line switching is completed. If the switching signal A is received immediately after the polling is issued, a stand-by mode for a response from a slave station is forcibly cancelled, and the polling is resumed, immediately after the switchover is completed. By thus sending the switching signal A to the monitor control board of the host station to suspend the polling being switched, a non-communication state until the timeout for waiting for the response from the slave station is detected can be eliminated, and notification failure of an alarm to the host station or a loss of response of the control can be prevented. COPYRIGHT: (C)2005,JPO&NCIPI
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