| 摘要 |
PURPOSE:To control optionally the extent of display of a superimposed picture and to prevent it from going to a hindrance to a background picture by changing the pulse width of picture display controlling signals generated synchronously with synchronizing signals in a monostable multivibrator circuit etc. CONSTITUTION:Ys signals (d) output range of which is controlled by display controlling signals (c) are inputted to a signal switching circuit 4. When the Ys signals (d) are in the range of high level, input R, G, B signals of characters, graphics etc. to be superimposed are selected and outputted, and the characters and graphics etc. are displayed, and in the range of low level, video signals of a background picture are selected and outputted, and the background picture is displayed. Accordingly, in this circuit, the pulse width of display controlling signals (c) can be changed optionally by making a resistor R variable, and the output range of Ys signals is controlled by a gate circuit 3 according to the display controlling signals (c). Thus, the extent of display of characters, graphics etc. of a superimposed picture can be changed optionally in horizontal direction.
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