PURPOSE: To prevent an interference with another radio system using the same carrier wave by activating a control means at the time when a subcarrier signal emitted from a gate device is detected.

CONSTITUTION: A data transmission/reception control part 13 of a radio communication control part 12 sends a control signal to a subcarrier generator 21 through a signal control part 16, and generates a subcarrier signal. This signal is modulated by a modulator 22, and transmitted by radio to a commutation ticket 8 from an antenna 7 through a distributor/synthesizer 23. When the commutation ticket 8 is shown in a communicating area of the antenna 7 of an automatic ticket examining device main body 2, a radio wave from the antenna 7 is received through an antenna 30 by the commutation ticket 8, and detected by a detector 38 through a distributor/synthesizer 31. When it is discriminated that the detected signal is a specific subcarrier signal exceeding a constant level by an activation circuit 32, the activation circuit 32 transmits an activation signal to a control part 36. In such a way, an interference with another radio system using the same carrier wave can be prevented.