Detection of pager signal in FM radio transmission.

摘要

Apparatus for detecting the presence of a paging signal at 57 KHz in a frequency modulated transmission includes a phase locked loop (14) which is sensitive to the presence of a pager signal. The phase locked loop (14) which produces phase adjusting pulses at a repetition rate representative of the presence or absence of a pager signal. The phase adjusting pulses are fed to a detector (22) which produces a bistable signal which is either low, indicating no pager signal, or high, indicating the presence of a pager signal.