| 摘要 |
PURPOSE:To prevent the furtive glance of picture information utilizing spurious radio waves radiated from a signal line connecting a computer and a CRT display. CONSTITUTION:The signal generation circuit 13 generates a bit-serial display data signal synchronized with a clock and transmits it on a display data signal. A dummy signal generation circuit 14 generates a dummy signal synchronized with the clock and transmits it on a dummy signal line. A display circuit 31 displays a picture on a CRT display 30 based on the display data signal transmitted through the display data signal line. The dummy signal line is terminated by a terminal circuit 32. The dummy signal changes at clock time when the display data signal does not change, and it does not change at clock time when display data signal changes. The dummy signal can be made into a rectangular wave that changes at a period twice as much as that of the clock. In such a case, the dummy signal needs to be made large. The dummy signal can be changed at random.
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