PURPOSE: To obtain a picture area proper to an each case and to display many characters or the like on a display divice by changing the pulse width of vertical blanking when a normal TV image receiver is used as a terminal display device.
CONSTITUTION: When the TV image receiver is used as the terminal of a computer, a vertical blanking switching circuit is connected and a vertical blanking pulse is applied to the base of an emitter/follower TR1 of the switching device through a resistance 2. The output of the transistor (TR) 1 is impressed to a diode through a resistor 4 and also applied to an integrating circuit 6. The integrating output of the circuit 6 is applied to a changeover switch 10 through a diode 9 and also applied to an output TR3 together with a diode 5 through a diode 8. When the switch 10 is used as a display, the output of the circuit 6 is earthed on the earth side and the output pulse width is switched from the pulse width TV image receiving to optimize respective picture areas.
KUBO SUMIKAZU
SHIMATANI TSUYOSHI
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