Editing Nixie tube (section)

== Design ==
[[File:ZM1210-operating edit2.jpg|thumb|upright|The stacked digit arrangement in a Nixie tube is visible in this (stripped) ZM1210.]]

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 two), but there are also types that show various letters, signs and symbols. Because the numbers and other characters are arranged one behind another, each character appears at a different depth, giving Nixie based displays a distinct appearance. A related device is the '''pixie tube''', which uses a [[stencil]] mask with numeral-shaped holes instead of shaped cathodes. Some Russian Nixies, e.g. the ИH-14 (IN-14), used an upside-down digit 2 as the digit 5, presumably to save manufacturing costs.

Each cathode can be made to glow in the characteristic neon red-orange color by applying about 170 [[volt]]s [[direct current|DC]] at a few [[ampere|milliamperes]] between a cathode and the anode. The current limiting is normally implemented as an anode [[resistor]] of a few tens of thousands of [[ohm]]s. Nixies exhibit [[negative resistance]] and will maintain their glow at typically 20 V to 30 V below the strike voltage. Some color variation can be observed between types, caused by differences in the gas mixtures used. Longer-life tubes that were manufactured later in the Nixie timeline have mercury added to reduce [[sputtering]]<ref name="Bylander 1979 60" /> resulting in a blue or purple tinge to the emitted light. In some cases, these colors are filtered out by a red or orange filter coating on the glass.

One advantage of the Nixie tube is that its cathodes are typographically designed, shaped for legibility. In most types, they are not placed in numerical sequence from back to front, but arranged so that cathodes in front obscure the lit cathode minimally. One such arrangement is 6 7 5 8 4 3 9 2 0 1 from front (6) to back (1).<ref name="nixieclock home" /><ref name="KD7LMO Overview">{{cite web |url=http://ad7zj.net/kd7lmo/ground_nixie_clock.html |title=KD7LMO - Nixie Tube Clock - Overview |website=ad7zj.net |date=2014-01-17 |access-date=2017-09-20 |url-status=live |archive-url=https://web.archive.org/web/20170714192451/http://ad7zj.net/kd7lmo/ground_nixie_clock.html |archive-date=2017-07-14 }}</ref>  Russian ИH-12A (IN-12A) and ИH-12B (IN-12B) tubes use the number arrangement 3 8 9 4 0 5 7 2 6 1 from front (3) to back (1), with the 5 being an upside down 2.  The ИH-12B tubes feature a bottom far left decimal point between the numbers 8 and 3.