Abstract: The present invention pertains to a coded electronic security system which includes a plurality of independent transmitting devices, each of which transmits a radio frequency signal at the same frequency. Each transmitter includes a unique modulator which "keys" it at a frequency which corresponds solely to that particular transmitter. One or more remotely located receivers is adapted to receive and decode the signal generated by any of the transmitters and to indicate which of the transmitters has been activated.

Abstract: The present invention pertains to a receiver for a coded electronic security system which includes a plurality of independent transmitting devices each of which generates a pulse coded RF signal when activated. The receiver demodulates the pulse coded signal and separates from the demodulated signal a high frequency square wave unique to each transmitter in the system and a low frequency square wave common to each of the transmitters in the system. The receiver determines the frequency of the high frequency square wave, verifies that the low frequency square wave is the one appropriate for the system, and then indicates which of the transmitters in the system has been activated.

Abstract: The present invention pertains to a transmitter for a coded electronic security system. The transmitter includes a modulator which automatically keys the radio frequency oscillator of the transmitter "on" and "off" to provide a pulse coded signal unique to the particular transmitter in the system. One or more remotely located receivers, of the type described herein, is adapted to receive and decode the signal generated by the transmitter of the present invention and to indicate which of the transmitters in the system has activated a signal device attached to the receiver.