DE3328420

A variable frequency oscillator circuit adapted for stabilization of its free-running frequency comprises a first signal synthesizing circuit, first voltage-controlled oscillator, a phase-locked loop and reference signal generator, the phase-locked loop consisting of a second signal synthesizing circuit, second voltage-controlled oscillator, phase comparator and low-pass filter. The first and second signal synthesizing circuits have the same characteristics, and the first and second voltage-controlled oscillators have the same characteristics. The reference signal and output of the second voltage-controlled oscillator are input to the phase comparator. The comparator output is applied to the first and second signal synthesizing circuits. An external signal is applied to the first signal synthesizing circuit, and the output of the first voltage-controlled oscillator acts as the output of the variable frequency oscillator circuit. The principles are applied to reading data pulses from a floppy disk.