PURPOSE: To make the oscillation frequency of a voltage controlled variable frequency oscillator equal to a synchronizing signal frequency regardless of the king of synchronizing signals by controlling the oscillation frequency of the voltage controlled variable frequency oscillator through the use of a pulse signal with a constant time width generated from the inputted synchronizing signal.

CONSTITUTION: When a horizontal synchronizing signal HS is supplied, a one- shot multivibrator circuit 14 triggered by the signal HS, and the pulse signal having the constant time width decided by the values of a resistance 14a and a capacitor 14b is generated. The pulse signal is mixed in a signal in a part to frequency-voltage-convert the oscillation frequency of a voltage controlled variable frequency oscillator 10 through a mixing circuit 16. Consequently, regardless of the kind of synchronizing signals, the oscillation frequency of the voltage controlled variable frequency oscillator can be controlled to equal to the synchronizing signal frequency.