| 摘要 |
PURPOSE:To prevent the luminance of displayed characters in the television and video mode from varying, by superimposing the DC voltage from an RGB luminance controlling volume and a signal which becomes ''H'' level in modes other than the RGB mode by using a diode. CONSTITUTION:A switching circuit 1 switches three color difference signals R-Y, G-Y, and B-Y and the output of an on-screen priority circuit 2 and a DC voltage for controlling the luminance of RGB signals passing through the on- screen circuit 2 is supplied from an RGB luminance controlling terminal 1a. When the RGB mode is selected under this condition, a diode 7 is cut off and the DC voltage which is determined by the position of a volumen 4 is supplied to the controlling terminal 1a through another diode 5. Since the diode 7 is conducted and a fixed voltage is supplied to the controlling terminal 1a under the television and video modes, the DC voltage becomes constant irrespectively of the position of the volume 4. Therefore, on-screen displaying characters which are always easy to see are obtained under the television and video modes.
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