TRANSPONDER SYSTEM

摘要

An electronic identification system comprising a transmitter (5) for generating an electromagnetic excitation signal, one or more portable transponders (3) for storing variable identification data, and for transmitting an information signal containing the identification data upon entering the field. Transmission of the information signal is independent of the excitation signal in both time and frequency. A radio frequency receiver is provided for receiving the information signal and in response generating an output signal representing the variable identification data contained in the information signal. THe system overcomes two principle disadvantages associated with existing systems: an excitation frequency can be selected for optimum performance given circumstances dictated by each application; an independent response channel can be selected according to the requirements of each installation or application, thereby allowing response signals to be transmitted by transponders at a frequency which differs from the frequency of an interfering signal.