Abstract: A phase detection circuit for detecting the phase shift of an input signal. An A/D converter converts the input signal into first, second and third digital data according to successive three sampling points. A first subtractor subtracts the third data from the second data to produce a first subtraction signal. A second subtractor subtracts the first data from the second data to produce a second subtraction signal. A third subtractor subtracts the second subtraction signal from the first subtraction signal to produce a signal representing the phase shift. An adder adds the first and second subtraction signals together to produce a signal representing the amplitude of the input signal. A converter converts the signal representing the phase shift into a signal representing the absolute value of the phase shift according to the signals representing the phase shift and the amplitude.

Abstract: A DC motor is supplied, from a motor driver, with a brake voltage constituted by a forward drive voltage, a reverse drive voltage, and a stop voltage of a zero potential level. An operational current of the motor driver is supplied to a low-pass filter whose output is supplied to first and second sample and hold (S/H) circuits. The first S/H circuit performs its sampling operation after a minute period of time in which the brake voltage goes through a polarity inversion from the reverse drive voltage to the forward drive voltage. The second S/H circuit performs its sampling operation after a minute period of time in which the voltage applied is changed from the forward drive voltage to the reverse drive voltage. The outputs or sampled values of both S/H circuits are compared with each other by a comparator. When the sampled values equal each other, i.e., when the number of rotations of the motor becomes zero, the comparator outputs a coincidence pulse. This pulse is supplied to a stop detector.

Abstract: A circuit for adjusting a picture quality by processing a digital video signal. A digital filter receives the digital video signal and extracts a high-frequency component therefrom. A first waveform-shaping element wave-shapes the high-frequency component to provide a noise cancel signal for canceling the noise. A second waveform-shaping element wave-shapes the high-frequency component to provide a contour compensation signal for compensating a contour of a picture. An adder adds the digital video signal, the noise cancel signal and the contour compensation signal to provide a signal with adjusted picture quality.

Abstract: A control system for an optical disc information reproducing apparatus in which information data stored in an optical disc is read out during a rotation of the optical disc by a light spot of a light beam.