From the very cool blog, Evil Mad Scientist.
Anyone remember these kind of displays? They’re called “nixie tubes”. They were invented in the early 1950’s, and introduced by the Burroughs Corp. I mostly recall them in sci-fi movies, and maybe movies like Fail-Safe. The name comes from NIX (Numeric Indicator eXperimental No. 1).
The technology is known as “cold-cathode”, and it’s similar to fluorescent lamps. The way they work is that each symbol is a cathode, and supplying current to it makes the gas in the tube glow around the shape.
EMS dissects one here. The numbers (though they could be letters or any symbol), are stacked one one top of the other, with a small space between them.