REMOTE VEHICLE ACCESS FEATURING HIGH SECURITY

摘要

A remote signal transmitter (10) capable of producing a radio frequency signal for implementation of access commands including an oscillator circuit (18) which is alternatively capable of producing a fixed frequency signal or a modulated frequency signal as a result of selective biasing by a microprocessor (14). The oscillator signal is broadcast as a series of data bits which achieve a unique signature as a result of the sequence in which the fixed and modulated signals are broadcast. In addition, the signals may be broadcast for various durations which are representative of digital zeros and ones. A receiver detects the presence of the fixed and modulated signals and digital values thereof by comparison with stored values. In this manner a friend/foe screen is implemented which then permits implementation of a command contained in the remainder of the data bit stream.