Selective call signal detection circuit for multi-channel access type radio receiving station.

摘要

A selective call signal detection circuit comprises a channel free/busy state detection circuit (9) for scanning a plurality of communication channels to determine their respective free/busy states, a present-time channel free/busy state memory circuit (11) for temporarily storing channel free/busy detection signals resulting from the aforementioned scanning of communication channels, a past-time channel free/busy state memory circuit (12) for receiving into storage therein in the subsequent channel scanning cycle the channelfree/busy detection signals of the previous scanning cycle formerly stored in the aforementioned present-time channel free'busy state memory circuit (11), and a comparison circuit (13) for comparing the signals from the aforementioned present-time past-time channel free/busy state memory circuits (11, 12) thereby discriminating between a selective call signal addressed to a given receiving station and selective call signals addressed to other receiving stations. Since this selective call signal detection circuit permits quick discrimination between a channel in the state of normal communication and a channel in the state of selective call, it serves to enhance the efficiency of channel scanning.