Abstract: In order to record information spirally on a disk and to reproduce the recorded information accurately without any contact, at the recording, an information signal and a predetermined signal for synchronous detection are added together, the resultant signal is subjected to frequency modulation and, while a laser beam intensity-modulated by the frequency-modulated signal is minutely swung in the radial direction of the rotating disk at the same frequency as that of the synchronous detection signal, it is caused to impinge on the disk to thereby record the information spirally on a recording medium of the disk without any contact. During the reproduction, as the disk is being rotated, a light spot is caused to impinge along an information groove formed on the disk, and reflected light or transmitted light from the disk is detected in the form of an electric signal.

Abstract: A PCM recording and reproducing apparatus comprising an error detecting circuit for detecting a frame including at least one word information signal with an error, the frame being a reproduction signal read from a recording medium on which certain pulse coded information is recorded in a frame distribution system, and a compensating circuit for compensating the reproduced information signal by the use of the output signal from the error detecting circuit, thereby removing the adverse effects of information dropout in spite of a high density recording.