To provide a cable MODEM system in which an abnormality of a CMTS is discriminated at an early stage and can be displayed on a display means outside a center station.

A center station 10 comprises at least one monitoring cable MODEM 17 and a power supply means 18 for supplying power to a CMTS 12. Information on the operating state of the monitoring cable MODEM 17 is then acquired and when it is determined that the operating state satisfies predetermined conditions, the connecting state of a subscriber side cable MODEM 2 connected to the CMTS is confirmed. When it is determined that this connecting state satisfies the predetermined conditions, the power supply means is controlled to turn off power supply from the power supply means to the CMTS and to turn on the power supply after the lapse of a fixed time so that the CMTS is reset. The state of the CMTS after reset is then determined and the acquired result is displayed on the display means.

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