AUDIO MULTIPLEX DEMODULATION CIRCUIT

PURPOSE:To make adjustment unnecessary for stereo separation in a production process by comparing the level fluctuation of a sub-channel signal with reference voltage for stereo or bilingual broadcasting and performing the feedback of a gain control circuit. CONSTITUTION:When a stereo broadcasting reception is performed, a stereo separation is automatically obtained by performing the control of an audio multiplex signal level by a level detection circuit 9, a comparator 10, a filter 11 and a variable gain amplifier 12 based on reference voltage V1 switched and connected by a switching circuit 13 so that the sub-channel signal level of the output of a BPF3 is 0.8Vrms. When a bilingual broadcasting reception is performed, the control of the audio multiplex signal level by the circuit 9, the comparator 10, the filter 11 and the amplifier 12 is performed based on reference voltage V2 switched and connected by the circuit 13 so that the sub- channel signal level of the output of the BPF3 is 0.6Vrms.