Large-screen display devices

PROBLEM TO BE SOLVED: To easily and exactly attain the operational position designation of a large screen displaying means by displaying a screen similar to the screen displayed on a large screen displaying means at a terminal means, and operating cursor position designation in the display screen of this terminal means. SOLUTION: For operating a large screen displaying means 1 by terminal means 6a-6n, the terminal means 6a-6n supply a data request command through a second LAN 9 to a data collection screen generating means 4, receives the supply of plotted data displayed on the large screen displaying means 1 at present, and displays a screen similar to the screen displayed on the large screen displaying means 1 on its own display screen. Then, the position designation of a cursor 10 is operated in this display screen, and only the movement command of the cursor 10 is transmitted through a first LAN 8 to a large screen controlling means 7. The large screen controlling means 7 distributes the supplied movement command of the cursor 10 to each individual controlling means 3a-3n.