A receiver includes an internal antenna installed on a substrate and capable of receiving a wireless signal, and an external antenna connected to a connector, which is arranged on the substrate, and capable of receiving the wireless signal. A demodulator is arranged on the substrate and demodulates the wireless signals received through the internal antenna and the external antenna. An applying circuit is arranged on the substrate and applies a voltage to the external antenna via the connector. A disconnection detector is arranged on the substrate and detects whether the external antenna is disconnected based on a voltage or current applied by the applying circuit. The internal antenna forms a part of the applying circuit.