Nixie tube

A Nixie tube, or cold cathode display, is an electronic device for displaying numerals or other information using glow discharge.

The glass tube contains a wire-mesh anode and multiple cathodes, shaped like numerals or other symbols. Applying power to one cathode surrounds it with an orange glow discharge. The tube is filled with a gas at low pressure, usually mostly neon and often a little mercury or argon, in a Penning mixture.