Nixie, although a trademark of the Burroughs Corp, is the generic term for cold-cathode gas-discharge numerical and symbol indicator tubes. Basically, a neon tube where the numbers to be displayed are actually metal electrodes shaped like the number itself. The result is an easily readable, nice, non-flickering orange or red/orange light in the shape of a number, reasonably visible in daylight.

Manufactured primarily in the 1960s, and based on the same technology as the vacuum tube, they are no longer made but remain in large quantity, and are consequentially not difficult to obtain.

The characters in early models were all 0.3"-- 0.6" digit height and visible from the top/end of a bulbous glass envelope. They eventually became available in a range of sizes up to 2", and later more commonly seen with the stack of digits viewed from the side of the tube, in a conventional miniature radio tube T5 outline. One undesirable aesthetic concern is that since the digits are stacked front-to-rear, un-lit digits partially obscure the lit digit, and the digits seem to shift back and forth as they change, since the stack of digits is about a quarter-inch deep.

Strangely, they are a collector’s item with a virtually limitless storage life. In normal use, they last for 20 to 50 years provided they are properly cared for. This includes not operating them at excessive currents (in which case the electrodes slowly evaporate and blacken the bulb), and illuminating the cathodes periodically to prevent cathode poisoning.

A nodeshell challenge by Apatrix

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