SCA demodulator circuit diagram

As shown in the figure, the frequency of the voltage controlled oscillator NE565 in this circuit is 67KHz, which is locked by the input 67KHz subcarrier component . The subcarrier is used for uninterrupted advertising background music played by FM radio stations. This circuit demodulates FM sidebands The signal is sent to the advertising sound system through a suitable filter. A 5k ohm potentiometer is used to lock the VCO at the exact frequency. The frequency response extends to 7KHz.