DIGITAL RADIO PAGING COMMUNICATION SYSTEM

A B S T R A C T A digital radio paging system comprising a transmitter at the central or base station and receivers at different remote stations. The transmitter generates in a predetermined sequence a preamble digital signal, a calling digital signal and an end mark digital signal. A carrier wave is modulated by this sequence of digital signals and the modulated carrier wave is received by the receivers where it is demodulated into the preamble digital signal, calling digital signal and end mark digital signal. The receivers also recover from the modulated carrier wave a clock pulse synchronised with the detected digital signal sequence. Demodulation is brought about under the action of a power source the voltage of which may be controlled in response to detection of the preamble digital signal and end mark digital signal or in response to a series of pulses of predetermined period generated in the receivers.