Abstract: In an intermittently operative phase-locked loop, in order to prevent the oscillator frequency from significantly changing at the time of turning on of an electric power source, a point in time at which a phase difference between clock signals respectively fed to a reference frequency divider and to a frequency divider for dividing the output frequency of a voltage-controlled oscillator becomes substantially zero is detected, and the two frequency dividers are initialized when the above-mentioned point in time is detected after turning on of the electric power source.

Abstract: A digital registration circuit for a multi-tube television camera wherein correction quantities corresponding to positions on a target of an image pickup tube are stored in a digital memory. The digital signal for the correction quantity read out from the digital memory is converted into an analog signal which is supplied to a low-pass filter and smoothed. The smoothed signal is sampled at a sampling frequency higher than the frequency at which the correction quantities stored in the digital memory are read out and the sampled signal is converted into a digital signal. The digital signals sequentially produced are applied to a shift register, and four sequential sample values supplied from the shift register are added together in an adder. The shift register operates in such a manner that four samples are shifted one by one every adding time. An output signal from the adder is used for correcting registration, so that the generation of shading can be prevented.

Abstract: A helical scan type magnetic tape recording/reproducing apparatus for recording/reproducing information, for example, a large amount of time-compressed audio PCM signals on a plurality of information tracks disposed in parallel to the direction of the tape running. Each of the time-compressed audio PCM signals are recorded with one of four frequencies of a pilot signal on a selected information track, and each of the time-compressed audio PCM signals recorded on the information tracks can be selectively reproduced from the corresponding information track. The apparatus includes a circuit for generating a plurality of track indicating pulses which respectively correspond to the information tracks and are phase-locked to the rotation of the rotating heads, and a circuit for selecting one of the track indicating pulses, which is supplied to control time compressing/expanding of an audio signal.