Circuit for automatic discrimination of audio intermediate frequencies

1. Field of the Invention A circuit for automatically discriminating audio intermediate frequencies of a received television signal that has a simple, compact and inexpensive circuit structure and can operate stably. The circuit comprises a high pass filter circuit for eliminating a synchronizing signal from an output of a video intermediate frequency detector; a synchronizing signal separation circuit for separating a synchronizing signal from the output of the video intermediate frequency detector; a waveform shaping circuit for shaping a waveform of an output signal of the high pass filter circuit; a counter for counting predetermined clock pulses; a counter controlling circuit, which, triggered by the separated synchronizing signal, (i) causes the counter to count the number of the clock pulses that are contained during a period of time that is defined based on the output of the waveform shaping circuit, and (ii) causes the counter to output a counted value; and a discrimination signal output circuit for discriminating a range, within which the counted value falls, from a plurality of ranges, and outputting a discrimination signal according to the result of the discrimination. The plurality of ranges are partitioned corresponding to audio intermediate frequencies.