Methods and arrangements for voting arrangement with a readjustment of the oscillator frequency of a (low by means of position in the wall of the reception portion of an image and / or sound reproduction system

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.