How a Nixie shows a digit

Where are all the other digits when one is glowing?

An IN-14 Nixie holds ten numeral-shaped cathodes, 0 to 9, stacked one behind another inside a gas-filled glass tube with a common anode, plus small decimal-point cathodes. The driver connects one numeral to the return path, and the gas glows in a thin sheath around that numeral's shape. The others stay where they are, as fine dark wire in front of and behind it; the glow is bright enough that the eye reads past them. The numeral is not a hot filament: it is a cold cathode wrapped in glowing gas.

Unlike a dekatron, a Nixie stores nothing. The digit is chosen from outside, by a driver chip, and lasts only as long as that driver keeps selecting it.

Property	Nixie	Dekatron
Visible state	Selected numeral shape	Position of the glow
Selection	External digit driver	Ordered pulses that pass the discharge between electrodes
Role	Displays an externally selected digit	Holds a powered count and moves it up or down
Stores a value	No: the driver holds the digit	Yes, while powered: the glow position is the value

Coming in Phase 2

An interactive numeral stack (pick a digit and see its layer light, front and side views) arrives with the Nixie hardware, once the IN-14's real stack order has been checked against a tube.