H03J7/00—Automatic frequency control; Automatic scanning over a band of frequencies
H03J7/18—Automatic scanning over a band of frequencies
H03J7/20—Automatic scanning over a band of frequencies where the scanning is accomplished by varying the electrical characteristics of a non-mechanically adjustable element
H03J7/24—Automatic scanning over a band of frequencies where the scanning is accomplished by varying the electrical characteristics of a non-mechanically adjustable element using varactors, i.e. voltage variable reactive diodes
H03J7/26—Automatic scanning over a band of frequencies where the scanning is accomplished by varying the electrical characteristics of a non-mechanically adjustable element using varactors, i.e. voltage variable reactive diodes in which an automatic frequency control circuit is brought into action after the scanning action has been stopped