PURPOSE: To generate many signals of different frequency at optional interval of time with reduced circuit scale by providing a variable capacity element and a voltage generating circuit which generates a voltage varying stepwise at specific time intervals and applies the voltage to the variable capacity element.

CONSTITUTION: An LC oscillation circuit 1 is provided with a varicap 2 instead of a capacitance element C. This varicap 2 varies in electrostatic capacity C with an input voltage. Further, a voltage generating circuit 3 which generates a voltage V varying stepwise at specific time intervals is provided as the input voltage source of the varicap 3. When a time interval is t1, the circuit 3 generates a voltage V1 and then the circuit 1 outputs a signal of frequency f1. Then, when the time interval is t2 and a voltage V2 is 2V1, a frequency f2 is 21/2f1. Similarly, when the voltage varies so that V3=3V1∼Vn=nV1, the output frequency varies so that f3=31/2f1∼fn=n1/2f1. Consequently, a signal of optional frequency is generated for an optional time by constituting the circuit 3 properly.