PURPOSE: To secure the coincidence of frequency stability between a phase control circuit and a source oscillator by selecting a signal of the corresponding phase out of a delay circuit equivalent to one cycle of an input signal to be controlled by means of a selector and an up-down counter of an (n) modulo.

CONSTITUTION: The waveform of an input signal SIG to be controlled is sampled by a delay circuit 11 and delayed by an extent equivalent to one cycle. Then each tap of the circuit 11 is set opposite to the value held by an up-down counter 13. A sample of the phase value shown by the counter 13 is taken out of the corresponding tap of the circuit 11 by a selector 12. As the counter 13 serves an n-notation counter, the total (n) pieces of signals, i.e., (n) phases of signals which are delayed every 1/n cyles of the signal SIG are obtained and selected by the selector 12. Thus a signal having the corresponding phase is selected out of the circuit 11 equivalent to one cycle of the signal SIG. As a result, the coincidence of frequency coincidence is secured between a phase control circuit and a source oscillator.