Radio receiver with reception-readiness monitoring feature and method

Claim 1

Radio receiver having an RF/IF/demodulator stage (1, 2); means (3) for separating-out a modulated auxiliary subcarrier from an output audio intelligence signal of the RF/IF/demodulator stage and detecting a modulation signal on said subcarrier; means (10) for filtering said modulation signal to provide an announcement recognition (AR) modulation frequency signal, if the subcarrier is modulated by said AR modulation frequency signal; means (9) for filtering a region or radio station recognition (RR) modulation frequency signal having a frequency differing from the AR modulation frequency; a muting circuit (5) coupled to said AR signal filter means inhibiting passage of said output audio intelligence signal from the RF/IF demodulator stage in the absence of an AR signal; and comprising, in accordance with the invention, a reception-readiness monitoring circuit comprising means (11) coupled to the RR frequency signal filtering means (9) for recognizing the degree of modulation of the RR frequency signal as modulated on the subcarrier (57 kHz) and providing an RR change output signal if the degree of modulation changes abruptly; a memory element (12) controlled by the degree of modulation recognition means (11) and storing receipt of an RR change output signal; timing means (13, 14, 15) connected to the memory and controlling the memory to provide a read-out signal indicative of failure to store an RR change output signal upon elapse of a timing period; and indicator means (16, 6) providing an indicator output if the read-out signal from the timing means is received.