Patent ID: 7902982

Claim:
A radio-frequency-identification interrogator that performs a communication-channel selecting process in a minimum transmission termination period for selecting, upon stipulation of a maximum continuous transmission period to continuously transmit a signal to an electronic tag and the minimum transmission termination period to terminate a signal transmission after a lapse of the maximum continuous transmission period, an appropriate communication channel to be used in the signal transmission before the signal transmission to the electronic tag, the radio-frequency-identification interrogator comprising: a nonresponse-ratio determining unit that determines, after a plurality of signals are transmitted in the signal transmission, whether a ratio of a number of nonresponses during a first predetermined period from the electronic tag to a number of the plurality of signals exceeded a predetermined value; and a signal-transmission terminating unit that terminates, when it is determined that the ratio of the number of nonresponses during the first predetermined period from the electronic tag to the number of the plurality of signals exceeded the predetermined value, the signal transmission to the electronic tag for a second predetermined period, wherein the radio-frequency-identification interrogator performs, after a lapse of the second predetermined period, the communication-channel selecting process for restarting the signal transmission to the electronic tag.