A nixie tube is an electronic evice for displaying numerals or other information. The glass tube contains a wire-mesh anode, and multiple cathodes in the shape of Arabic numerals. 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 and/or argon, in a Penning mixture (Weston 1968, p. 334), (Bylander 1979, p. 65).