RADIO TAG SYSTEM

PROBLEM TO BE SOLVED: To efficiently transmit a request signal by detecting approach of a maintenance/monitor target and to surely read a response signal transmitted from each tag by means of an on-vehicle reader.SOLUTION: A radio tag system is composed of a tag installed in a maintenance/monitor target and a reader installed on a mobile which passes by the maintenance/monitor target. In the radio tag system, a request signal is transmitted from a transmitter of the reader, the tag receiving the request signal transmits a response signal, and the response signal is received by a receiver of the reader. The mobile includes approach detection means which detects the approach of the maintenance/monitor target during movement, and the transmitter of the reader includes a function to transmit the request signal when the approach detection means detects the approach of the maintenance/monitor target. The tag includes a function to transmit the response signal using a predetermined channel and a transmission pattern when the request signal is received, and the receiver of the reader includes a function to receive the response signal that the tag has transmitted using the predetermined channel and the transmission pattern.