A transmitter/receiver for train detection

A transmitter/receiver device is used together with a control device (100) on the ground, which performs detection of a train (10), performs transmission and reception of a train detecting signal, and collates data added to a received train detection signal with predetermined data. A transmitter (11a) adds a first unique code data to a train detecting signal transmitted from the control device (100) and transmits the signal including the first unique code data to a track circuit (1). A receiver (11b) receives the train detecting signal from the track circuit, adds thereto a second unique code data and transmits the thus enlarged signal to the control device (100).