Patent ID: 7764164

Claim:
An interrogator to transmit and receive a signal to and from a wireless tag, comprising: a carrier sense unit to detect an idle channel in a plurality of channels used for communications with the wireless tag; a transmitting unit to transmit the signal to the wireless tag by use of the detected idle channel; a detecting unit to detect communication timeout when an abnormality in the communications with the wireless tag continues for a predetermined timeout period; and a control unit to control the transmitting unit to interrupt the transmission to the wireless tag when the detecting unit detects the communication timeout within a predetermined observation period from a point of time when starting the transmission of the signal to the wireless tag, while continue the transmission to the wireless tag when the detecting unit detects the communication timeout after the predetermined observation period, and to control the carrier sense unit and the transmitting unit to re-detect an idle channel after elapse of a predetermined halt period from the transmission interruption due to the detection of the communication timeout and resume the transmission to the wireless tag by using the re-detected idle channel.