| 摘要 |
PURPOSE:To relieve the backup automatically at the restoration of a fault of a communication line after backup by detecting the fault restoration of the communication line automatically during the backup. CONSTITUTION:If abnormality takes place in the communication line 8 extend to object devices 3, 4 and the devices 3, 4 cannot be supervised and controlled, the operator of a supervisory and control equipment 1 connects backup communication lines 11, 12 via a public line network 6 to cover the supervision and control to the object devices 3, 4. Then the supervisory and control equipment 1 inquires about the restoration to the object device 3 through the communication lines 7, 8 at an interval of prescribed time. If the restoration of the communication line 8 is detected, the communication lines 11, 12 connected to the public line network 6 are interrupted to release the backup.
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