method and device for the automatic adjustments might have of a afsteminrichting in oscillatorfrequentie set a super he - terodyne ontvanggedeelte weergavein direction of a for beeld and / or sound.

摘要

The invention provides a method and apparatus for automatically controlling the local-oscillator frequency in a superheterodyne receiving section of a sound reproduction system through the use of a digital a.f.c. circuit. A frequency is derived from the local oscillator frequency and compared with a modulator frequency. The discriminator forms a dc voltage corresponding to the difference between the local oscillator frequency and the discriminator frequency. A varactor in the local oscillator is controlled with the dc voltage such that the local oscillator frequency varies opposite the direction of control of the dc voltage.