A nixie tube is a pre-LED electronic device for displaying numbers or other information, in the form of a glass tube containing multiple cathodes and a wire mesh anode, filled with neon and often a little mercury and/or argon at a small fraction of atmospheric pressure. It resembles a vacuum tube in appearance, like those used in early televisions and radios, however, its operation does not depend on heating of a cathode to cause it to emit electrons, as in the thermionic effect. It is therefore called a cold-cathode tube, a form of gas filled tube. Vacuum tubes were almost totally replaced by transistors and nixies were totally replaced by LEDs.
The most common form of nixie tube has ten cathodes in the shapes of the numerals 0 to 9 (and occasionally a decimal point or colon), but there are also types that show various letters, signs and symbols. Each cathode can be made to glow in the characteristic neon red-orange color by applying about 170 volts DC (compare that to the voltage on LEDs...) between it and the anode. You might wish to use our Nixie Tube Anode Resistor Calculator with respect to this clock. Some color variation can be observed between types, caused by differences in the materials and gas mixtures used. Nixies were used in all fields of industry where digital displays and readouts were used. One of the most famous uses of nixies was in the James Bond 1964 Ian Fleming movie thriller, Goldfinger. The small, certainly for that time, dirty atomic bomb had a nixie timer on it that ended at 007, prior to the intended detonation time (thank goodness)! That may have been the first vision of terrorism of the future. Click here for our counter and here for our clock and timer combo display.