A frequency modulator configured NE566 integrated voltage-controlled oscillator shown in FIG. When the signal input terminal potential DC position, forming a cycle of constant
frequency oscillation; change input terminal potential, IC output frequency of the frequency modulation circuit changes accordingly. FIG component parameter reference value, when the resistance: Ri - R2 - lOOfl. Rd - lOkZRP2 - when 50kfl, 20 to the output frequency can be about a corresponding change in 40kHz; RP2 or change the value of G, the output frequency changes accordingly.