Electronic proximity identification system

摘要

An electronic identification and recognition system including a portable card having a circuit therein for generating and transmitting and identifying signal comprising predetermined frequency pulses. The card functions in cooperation with a reader which radiates a radio frequency carrier signal received by an antenna in the card. This signal is used both to power the circuit of the card and to provide the basic frequency signal which is modified to generate secondary frequency signals which are transmitted back to the reader in a predetermined sequence identifying the card.