(under subclass 18) Subject matter wherein the reference
source is a spectrum generator producing a plurality of waves of different frequencies, which waves are simultaneously fed to the comparator or discriminator of the A.F.S. circuit of the controlled oscillator means being provided wherein the generated waves of the controlled oscillator may be selectively locked-in to the desired frequency of the spectrum.
(1) Note. This subclass does not include those systems wherein a filter or harmonic selecting network is provided for selecting a single frequency from the range of frequencies of the spectrum source, the selected frequency being fed to the comparator. Such systems are elsewhere in subclasses 1+, depending on the type of oscillator or type of A.F.S. control.
