Nimo tube

Nimo was the trademark of a family of small cathode-ray tube (CRTs) used for numerical displays.

[1][2] The Nimo tube operated on a similar principle as the charactron, but used a much simpler design.

Having only three electrode types (a filament, an anode and ten different grids), the driving circuit for this tube was very simple, and as the image was projected on the glass face, it allowed a much wider viewing angle than, for example, Nixie tubes, which Nimo tried to replace.

[3] The tube required 1750 volts direct current (DC) for the anode and also required 1.1 volts for the filaments, as well as a cathode bias for the filaments that enables or disables the display of a character on a specific tube.

This allows the display tubes to be multiplexed, simplifying the interface circuitry.