A visual display system was a type of monitor used by the Ledosians on Ledos, a planet in the Delta Quadrant, to test pilots for examinations.
In 2378, after beaming aboard the USS Voyager, Kleg, the instructor for Lieutenant Tom Paris' pilot test, asked him if he had access to a visual display system on Voyager, to which Paris told him he would be able to find one. (VOY: "Natural Law")