Narrow band communication system

Claim 1

A narrow band modulation UHF/Microwave communication system including a transmit/receive base station and a plurality of transmit/receive remote stations, wherein said base station comprises: master oscillator means; means for generating, from an output of said master oscillator means, a plurality of carrier signals of different channel frequencies spaced apart over a band of frequencies; means for generating, from an output of said master oscillator means, a reference carrier signal of a frequency spaced from said band of frequencies; means for transmitting information, as narrow band modulation of respective ones of said different channel frequencies, to a plurality of said remote stations; and means for transmitting, unmodulated, said reference carrier signal to all of said remote stations, and each of said plurality of remote stations comprise: means for receiving at least one of said modulated channel frequencies; means for receiving said unmodulated reference carrier signal; a controllable frequency slave oscillator; means for controlling the frequency of oscillation of said slave oscillator in dependence upon the frequency of said reference carrier signal; means for demodulating said at least one modulated channel frequency with reference to an output from slave oscillator; and means for generating, from an output of said slave oscillator, at least one carrier signal at a respective one of said different channel frequencies.