A ringing suppression circuit is provided at one or more nodes each having a communication circuit executing communication with another node by transmitting a differential signal through a pair of communication lines connected to the nodes. The operation controller is configured to shift a mode of the suppressor to a normal-operation mode when the differential signal is transmitted through the pair of communication lines, and to shift the mode of the suppressor to a low-current operation mode when the differential signal is not transmitted through the pair of communication line. A current consumption of the suppressor is less in the low-current operation mode than the normal-operation mode. The suppressor and the operation controller are configured to receive permanent power from a DC power supply, and the communication circuit is configured to receive power from the DC power supply via a power supply switch.