PURPOSE:To perform the designation of a descriptive point position and that of the addition of an underline, by taking synchronization with respective scanning frequency, and superposing a point position signal on respective signal with a tablet input format, etc. CONSTITUTION:A signal superposing part 6, similarly as a clock 5, selects the video signal of a designated one system by external video input signals X1-X3 and a switching indication signal received from a main control part 3, and performs the signal superposition of the signal with a point position data read out from a frame memory part 4 with a timing synchronized with the scanning frequency of the video input signal. Furthermore, an output interface part 7 which outputs other video input signals without performing the signal superposition to the outside and a monitor display 8 as outputs Y1-Y3 outputs a video input signal switching indication signal from the main control part 3 to the outside, The monitor display 8 selects and video-displays the signal on which the signal superposition of the outputs Y1-Y3 from the signal superposition part 6 is applied by the switching indication signal from the output interface part 7.
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