A camera and a microphone array configuring a monitoring system are capable of receiving electric power from a PoE apparatus through a LAN cable. In a case where a first switching operation is performed on a microphone array side, an output terminal of an input switch is connected to an input terminal of a PoE electric power reception circuit side. An input terminal of an output switch is connected to an output terminal of a PoE electric power transmission circuit side. On a camera side, an output terminal of the input switch is connected to an input terminal of a PoE electric power receptor side. The microphone array receives electric power that is supplied from the PoE apparatus for operation and transmits the electric power towards the camera. The camera receives the supplied electric power from the PoE apparatus through the microphone array and the LAN cable for operation.