| 摘要 |
PURPOSE:To display characters of different systems at the same position on a screen by comparing system-discriminated data with a system-discriminated result which is inputted previously, and sending vertical position data on a character to a display device according to the newly inputted system-discriminated decision result only when the comparison result shows difference. CONSTITUTION:A system discrimination circuit 1 discriminates whether the vertical synchronizing frequency of a TV signal is 50 or 60Hz. When the circuit 1 discriminates that the frequency is 60Hz, it generates a high-level output and transistors 3 and 6 turn on to input a high-level signal to a control means 8. When the circuit discriminates on a 60Hz system, it generates a low-level output and no high-level data is inputted to the means 8. The means 8 stores this result in a storage device 13 and compares it with the last system discrimination result; only when they are different from each other, the newly inputted system discrimination result is employed to send vertical position data on on- screen displayed characters to the character display device 9 without changing their relative vertical positions on the TV screen. Thus, characters of different systems are displayed at the same positions.
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