Abstract: A circuit for controlling white balance in a video signal comprising separators for separating a luminance signal, a red signal and a blue signal from the video signal, gain control amplifiers for amplifying the separated red signal and the separated blue signal, substractors for making a red minus luminance signal and a blue minus luminance signal from the luminance signal, the amplified red signal and the amplified blue signal, integrators for integrating the luminance signal, the red minus luminance signal and the blue minus luminance signal, switching circuit, coupled between the substractors and the integrators, for switching outputs of the substractors to supply the luminance signal, the red minus luminance signal and the blue minus luminance signal having only levels under predetermined levels to the integrators, and microcomputer for determining whether the outputs of the integrators belong to a certain white area, to control gains of said gain cortrol amplifiers when the ouput of the integrators belo

Abstract: An apparatus and method for automatically controlling adjustment of a head switching point in a VCR allows for automatic adjustment of the head switching point instead of the conventional manual adjustment thereof. The adjustment can be performed during every tape playback routine, thereby providing stable image quality. According to the present invention, a drum pulse signal is amplified by an amplifier, delayed by a time constant of a delay monostable multivibrator and output as a head switching signal by a frequency generator. The microcomputer outputs control data to adjust a head switching point by adjusting the constant of the monostable multivibrator such that a desired head switching point is obtained. The control data from the microcomputer is converted by a digital/analog converter into an analog voltage signal for adjustment of the time constant of the delay monostable multivibrator, thereby enabling the desired adjustment of the head switching point.

Abstract: A recording and playback system for code recording of VCR which comprises a synchronous separator, an 1/2 frequency demultiplier, a microcomputer, a comparator, a control pulse amplifier, a key matrix, a control circuit, a control head, a pulse generating head, and particularly at least demultiplier, transistor, switch, and resistor, whereby it is made to record a code in initial stage of recording, whereby it can be reproduced only when decoding the code in the initial stage of reproducing, while in a state of not selecting a code mode, it operates as similar as the conventional VCR, and even if one knows the code, the code cannot be decoded in other VCR having not the decoding function whereby it cannot be reproduced normally, whereby complete secret preservation can be kept, while in the normal mode being of not code mode, it operates similarly as the conventional system so that it can be easily applied to conventional system.