Selective paging system

Claim 1

A paging communication system for selectively signalling any of a plurality of individual paging receivers by transmitting a carrier-wave signal frequency modulated in accordance with a pulse-train signal coded to identify the receiver on call to cause such receiver to produce an alert signal, said system comprising: means for selectively generating any of a plurality of pulsetrain calling-code signals, each having a repetition rate of approximately 100 hertz, and each uniquely identified with a different individual paging receiver; a transmitter coupled to said generating means and responsive to the selected calling-code signal for developing said frequency modulated carrier-wave signal and transmitting it to said receivers; and a plurality of individual paging receivers each comprising a. means for receiving the transmitted frequency modulated carrier-wave signals; b. means coupled to the receiving means for detecting the received calling-code signal; c. means comprising a low-pass filter coupled to said detecting means and having a cutoff frequency substantially equal to twice said repetition rate for converting the detected calling-code signal to a substantially noise-free continuouswave signal having different amplitude levels reflecting the code represented by the detected signal; d. means coupled to said low-pass filter and responsive to the different amplitude levels of said continuous-wave signal for developing a digital signal containing said code; e. digitally responsive decoding means coupled to said digital signal developing means for recognizing the code represented by said digital signal and for providing a recognition signal in response thereto; f. and indicating means responsive to said recognition signal for providing said alert signal.