After applying a high voltage between the metal front grid (anode) and a number (cathode) applied neon gas becomes ionized at the cathode. This leads to the lights of the number with the characteristic orange .

Although the voltage is quite high, the current flowing amount is very small. Therefore, the clocks use little power and generate almost no heat. The tubes are not hot and just feel warm. It is a shine not a glow.

The most common tube has ten cathodes representing the numbers 0 through 9. Observe Nixie tubes and you see numbers made of metal sheet arranged behind each other.

Only the number with applied voltage lights. The remaining numbers remain barely invisible.

Today built-in Nixie clocks tubes are found in old warehouses or removed from discarded equipment. Usually the built-in Nixie clocks tubes are approximately about 40 years old. Stocks of Nixie tubes are difficult to obtain and are expensive. These are rare.

Nixieclocks.ch installs right now unused tubes.