TV or radio receiver tuning circuit - uses comparator for rated and oscillator frequency, disconnection of tuning line to channel selector, and measuring oscillator frequency

摘要

The circuit is intended for TV or radio receiver tuning in an automatic transmitter search. It measures certain criteria from the received signal. On impingement of a signal from a transmitter to be received, the transmitter search is held by a stop circuit. The tuning circuit is designed to initiate the following order of steps. The rated frequency is supplied, together with the oscillator frequency of the channel selector (1), to a comparator effecting the change of the tuning voltage until the two frequencies are identical. The tuning line to the channel selector is then disconnected and the oscillator frequency is held by the automatic frequency control. After this, the oscillator frequency is measured at a higher precision by change-over of the comparator. If it still differs from the rated frequency, the latter is commutated until they are equal. Finally the automatic frequency control is disconnected and the tuning line reconnected.