| 摘要 |
PURPOSE:To switch to a standby device without generating a malfuction in service, by driving a switching means of a switching device of the present working device and the standby device, before supply voltage exceeds an allowable value. CONSTITUTION:When a falts occurs in an electric power supply device PWO at a time point t1, supply voltage V supplied to a present working communication controller CCUO starts to attenuate from a standard value VO, and when it becomes lower than detecting voltage VR at a time point t2, a detecting device DETO outputs a detecting signal DSO, and sends it to a switching controller SC and a central processor CPU. The switching controller SC which has received the detecting signal DSO drives a switching device S1 and S2 at a time point t3, and transfers automatic teleprinter exchange service to a standby communication controller CCU1 from the present working communication controller CCUO. At the time point t3, the supply voltage V supplied to the present working communication controller CCUO is maintained so as to exceed an allowable value VL, therefore, there is no possibility that an erroneous operation occurs. |
