PURPOSE: To prevent the malfunction of the multiple switching due to the shock noise of the vibration or impact by detecting via the PLL circuit the signal which controls the multiple demodulator circuit in the receiver for the TV multiple sound broadcast.

CONSTITUTION: The control signal of the TV multiple sound is contained in the AM-modulated pilot signal. The detection signal passed through buffer circuit 2 after the AM detection is supplied to PLL circuit 10, and this input signal is compared with the output signal of divider circuit 12 concerning the phase and the frequency. And the output is removed for its high band component through LPF13 to be changed into control voltage V of VCO14 after the DC amplification and then compared with voltage VR corresponding to the intermediate level between the two frequencies of the control signal through voltage comparator 15, and the output turns to be the stereo and bilingual control signals is acordance with the high and low output. Then the signal given from the input signal detector circuit 20 is delivered through one of gates 16 and 18 to carry out the switching control.