Early touchscreens were far from the multitouch displays found on the newest iPhone or iPad, and a 1982 episode of BBC’s “Tomorrow’s World” shows exactly why.
While modern touchscreen displays use either a resistive or capacitive display to sense what your finger is touching, touchscreens in 1982 actually used a grid of intersecting infared light beams. When your finger touched the glass of the display, it would interrupt the horizontal and vertical infared light beams, sending a coordinate of where your finger was to the TV.
So what were touchscreens used for back then, as smartphones were more than a decade away? You’ll have to watch the video to find out, but it involves yellow balloons and air pistols.