Patent ID: 7253717

Claim:
An RFID system comprising: a plurality of RFID transponders configured to receive a signal and to generate a response signal based thereon, said RFID transponders having a random number generator usable to determine whether to respond to a received message addressed to said plurality of RFID transponders, said RFID transponders being further configured to use said random number generator to generate a unique identification code based only on a first random number generated by said random number generator, each said unique identification code being associated with a respective RFID transponder; a host computer configured to generate a message for transmission to at least one of said RFID transponders; and at least one interrogator communicatively coupled to said host computer having an interrogator transmitter and an interrogator receiver which operate in half-duplex mode, wherein said interrogator transmitter is capable to transmit messages received from said host computer to said plurality of RFID transponders during a first part of said half-duplex mode and provide an illumination signal to said plurality of RFID transponders during a second part of said half-duplex mode, and said interrogator receiver is capable to receive a signal generated by said at least one of said RFID transponders and provide said received signal to said host computer; wherein said host computer is configured to identify the unique identification code associated with each of said plurality of RFID transponders by iteratively transmitting a message including a variable having a predetermined value to said RFID transponders, and only said RFID transponders which generate a second random number greater than said variable respond to said message by transmitting the identification codes associated with said respective RFID transponders.