A radio-frequency identification system includes (a) responders each having a
unique
identification number, (b) an interrogator making an inquiry to and receiving a
response from each of the responders, and (c) a host computer controlling communication
made between the responders and the interrogator, and binary-searching a number
space of the identification number of each of the responders for identifying a
responder(s) existing in a communication area in which the responders and the interrogator
can make communication with each other. The host computer has a function of acting
as a discriminator for generating a control signal in accordance with first to
N-th (N2) communication areas in each of which the responders and the interrogator
can make communication with each other, binary-searching the number space in each
of the first to N-th communication areas one by one to identify a responder(s)
existing therein, and inactivating the thus identified responder(s).
