Coded electronic security system

Claim 1

An electronic security system for detecting, identifying and reporting the occurrence of alarm activating events at remote locations, comprising: a plurality of transmitters, each located at one of said remote locations and each for transmitting a signal comprising a plurality of transmissions at a selected transmission repetition frequency and with a selected transmission duration less than the interval between said transmissions, said frequency and duration being common to all transmitters in the system, each of said transmissions comprising a series of pulses of RF energy at a selected identical pulse repetition frequency, said pulse repetition frequency being unique to each transmitter in the system; a plurality of transmitter activating means, one for each of said transmitters, each for activating its corresponding transmitter for a selected time period on the occurrence of a particular alarm activating event; a receiver, responsive to said transmitted signal, including separate means for comparing said transmission repetition frequency and transmission duration to selected values, thereby to verify the authenticity of said signal as one originating in one of said transmitters, counting means for measuring said pulse repetition frequency, thereby to determine which of said transmitters originated said signal, and means for providing an output signal representative of the occurrence of an alarm activating event at one of said transmitters if said signal is verified as authentic and determined to have a pulse repetition frequency corresponding to one of said transmitters; and indicator means, responsive to said receiver output signal, for indicating the occurence of an alarm activating event.