I’m sure you’ve seen pictures like this:
and wondered “I’ve seen the NASA Mission Control before, but I’ve always wondered how they displayed those beautiful numerals both above the large screens and on the consoles, I wonder how they work?”
Well, you can find out after the break!
Unlike Nixie Tubes (which were used in more backroom operations; they weren’t as easy to read and didn’t give the same ‘wow’ factor for the cameras), they are not under vacuum and did not require immense power to keep them lit.
Above: Nixie Tube Display VS. In Line Readout
These devices called either “One Plane Displays” or “In-Line Readouts” were like mini projectors that contained small slides for numbers, letters, and even background color to highlight the information being displayed. Most were built by the Industrial Electric Engineers (IEE) and displayed Futura font, which is smooth and easier to identify than on Nixie tubes or edge lit displays
Below is an exploded view of the internals of an individual display which shows the light bulbs, light separator, magnification, and slides in the slide holder:
These displays were used on to display the channel number, process timers and position coordinates. Unfortunately, as processing speed increased and the advent of the LED and 6 segment displays were introduced, these displays were phased out and deemed inefficient and space wasting.