Airport information boards
Please, where is a timeline for technology developments in departure and arrival time information boards for passengers to read? I can find nothing about it in Wikipedia.
Recently they all seen to be television / computer screen type, but I seem to remember from former years a type where each letter position had turning flaps with letters on. When was the first advance from merely a paper-printed timetable or someone chalking it on a blackboard? E.g. what method was usually used in 1950, or 1960?