Abstract: A stabilized direct current power supply includes a switching device for selecting DC stabilization operation of the chopper type in the operation mode, in which heating and power consumption in an electronic device could cause a problem, in order to soften the problem. Alternatively the switching device selects DC stabilization operation of the linear control type not generating noise in the operation mode, in which noise for the electronic device circuit could introduce a problem, but heating and power consumption causes no problem. Further, the power supply uses a series transistor common to both types of DC stabilization operation.

Abstract: A recording and reproducing system which can automatically repair, when an abnormal condition of production occurs, the abnormal condition in a recording condition without manual operation-of an operator. When an abnormal condition of a reproduction signal from a compact disc is detected, the compact disc is reproduced again beginning with a head portion of a data block being currently reproduced or a portion immediately forwardly of such head portion, and reproduction signal then is recorded again from a head portion of a data block being currently recorded by digital signal recording and reproducing means or a portion immediately forwardly of the head portion.

Abstract: The inventive focus control system for optical recording/playback apparatus performs the initial focus pull-in operation for bringing the focused beam spot right on the recording medium surface through the focus sweep operation. The light beam focus position is moved under velocity control based on the relative velocity between the focus position and the recording surface detected through envelope detection and differentiation of the signal produced from the reflected light beam from the recording medium surface.

Abstract: A switching regulator operates either in the discontinuous mode or in the continuous mode depending on the magnitude of a load current. A mode detector outputs a mode signal Vg indicative of whether the switching regulator is operating in the discontinuous mode or in the continuous mode. In accordance with the mode signal Vg, an error amplifier selectively operates with a first feedback ratio or a second feedback ratio so as to output an error signal Ver indicative of the variation of an output voltage of the regulator. The error signal Ver is then supplied to a PWM (pulse-width modulation) comparator which in turn outputs a PWM signal in accordance with the error signal. The PWM signal drives a switching transistor to switch an input voltage of the switching regulator.

Abstract: An improved tone control device for controlling a tone within an audio frequency range in a combined mode of fine compensation for frequency characteristic as in the graphic equalizer and coarse tone control as in the bass/treble tone control circuit by making use of corresponding circuits in common for the both control without increasing the scale of circuitry, whereby the audio frequency is divided into N and M (<N) bands and the first manipulation input is fed to each one of the N bands while the second manipulation input is fed to each one of the M bands, the second input is converted into weights for each band in the N bands as by increasing or decreasing the gain thereof with a conversion means and setting the gain of each band by utilizing a gain setting means in accordance with the amount of first manipulation input as well as the weighted gain for an intended tone control.