A paging system in which an address code is transmitted at a lower transmission rate than message code and a discrimination code defines the boundary between the address and the message. The receiver includes a low pass filter with a cut-off frequency switchable between the reception rate for the address...http://www.google.com.au/patents/US4642632?utm_source=gb-gplus-sharePatent US4642632 - Digital paging system having bit rate switching means and digital paging receiver therefor
