| 摘要 |
PURPOSE:To detect service interruption with high reliability by providing a no-break power supply unit for generating a power supply voltage of a commercial frequency at a normal time, and the power supply voltage whose frequency is different from the commercial frequency at the time of service interruption, and detecting the variation of this power source frequency by an amplifying device side and transferring it to a centralized monitoring device. CONSTITUTION:In case the no-break power supply unit 31 becomes a service interruption state and switched to an inverter circuit whose power source is a battery, an AC voltage whose frequency is different from that of the commercial AC power source of a normal time is generated, and fed to a line 12 through an amplifying device 32. As a result, in a power source frequency detecting circuit 33 of the inside of the amplifying device 32, the variation of a power source frequency, which follows up a service interruption is detected, and this frequency variation information is sent to a centralized monitoring device 17 of a CATV system together with other data such as a signal intensity data, etc., through a monitor signal transmitting/receiving equipment 34. In the centralized monitoring device 17, by knowing the variation of this power source frequency, whether the service interruption exists in an installed position of each power supply unit or not is detected. In such a way, the service interruption can be detected with high reliability by an extremely simple constitution.
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