PURPOSE: To ensure the tuning between the oscillating frequency and one of plural frequency bands having different frequencies, by applying the output of a frequency discriminating circuit to a varicap diode of a variable frequency oscillating circuit.

CONSTITUTION: The output of one of quartz oscillators 1∼3 which is selected by a selection switch 4 is converted into the DC voltage having a level proportional to the oscillating frequencies of the oscillators 1∼3 through a simple frequency discriminating circuit which contains an amplifying circuit 9, a differentiating circuit 10, a wave detecting circuit 11 and a DC amplifying circuit 12. This DC voltage is applied to a varicap diode CD1. The CD1 and L1 decide the oscillating frequency of a variable frequency oscillator 8 and then excite the oscillator 8 with a frequency of m-times as high as the oscillating frequency of the oscillator 8. The output of the oscillator 8 is fed back via a loop containing a frequency divider 5, a phase comparator 6, a low pass filter 7 and a varicap diode CD2 which decides the capture range.