An operating unit performs a prescribed operation and includes a standby-state-signal generating unit that generates a standby state signal for switching between a standby state and an operation state of the operating unit in a first part of the operating unit. An optical-signal transmitting unit converts an electric signal, which is a result of the operation in a second part of the operating unit, into an optical signal, transmits the optical signal to a third part of the operating unit, and then converts the optical signal into the electric signal. A power-supply control unit controls a supply of the electric power to the operating unit and a supply of the electric power to the optical-signal transmitting unit by a power supply unit in response to the standby state signal.