PURPOSE: To obtain deep modulation and to reduce waveform distortion and jitter, by simultaneously performing FM with an analog modulation input and FSK with a digital modulation input signal.

CONSTITUTION: An analog modulation input signal is applied to a terminal 6 of the 1st phase-lock circuit 1. An analog modulation signal is superimposed on an output of a low-pass filter 15 in a phase-lock loop. A voltage controlled oscillator 11 is controlled with the superimposed signal. An output signal of the voltage controlled oscillator 11 is mixed with an output signal of a voltage controlled oscillator 21 of the 2nd phase-lock circuit 2 and is given to a frequency divider 23. A digital modulation signal is given to the frequency divider 23 and the frequency dividing ratio is controlled in response to a mark and a space signal. The output signal of a reference oscillator 3 is frequency-divided into a desired transmission frequency and given to a phase comparator 24, resulting that both modulations of analog and digital signals can be realized.