Switching stage for automatic tuning of FM radio receiver - has delay stage compensating signal strength variation but inhibited during station changeover

摘要

A switching circuit for F.M. radio receivers has a tuning display that is responsive to a specific pilot signal but is not affected by transient reductions in the strength of the received signal. The receiver consists of an intermediate frequency amplifier (1), an F.M. demodulator (2) and a low frequency amplifier (3) coupled to the loudspeaker. A recognition stage (4) detects the pilot signal and is coupled to the display (6) over a time delay switching stage (6). The output of the demodulator (2) is coupled over a switching stage (7) that reacts to a change in signal frequency. When changing from one station to another the stage (7) inhibits the time delay unit (5).