Vacuum & Gas-Filled Displays

This section encompasses various types of thermionic and cold-cathode display tubes, including Nixie tubes, Panaplex displays and VFDs.

Gas Discharge Displays

Gas discharge displays are low pressure neon lamps with multiple, shaped or shape-shaded cathodes. Tubes in this family include Nixie, Pixie and Panaplex displays, designs primarily of Burroughs origin. Nixie tubes were driven by a range of decade counter technologies, including hard valve and thyratron decades, dekatrons, beam switching tubes, discrete transistor counters and specialized TTL devices.

The earliest gas discharge displays were patented in 1934 by inventor Hans Paul Boswau, who envisioned all sorts of useful applications for such numeric display tubes. Boswau's primitive design consisted of shaped wire cathodes sandwiched between glass or mica discs in a large end-view envelope; this device never entered commercial production.

In 1954, National Union began to market their own numeric gas discharge tube, which dispensed with the glass plates of Boswau's device and replaced them with stiff wire supports. Sold under the 'Inditron' trade name, National Union's display was a cumbersome, experimental device, and was only produced in limited quantities.

Less than a year later, Burroughs introduced a new design which incorporated an anode mesh and a new gas mixture, transforming the numeric gas discharge display into a practical device. Electronics lore states that the name 'Nixie' originated when a Burroughs draftsman labeled drawings of the tube NIX1, shorthand for Numerical Indicator Experimental 1. Though Burroughs filed the Nixie term for trademark status in 1956, 'Nixie' has since become a generic descriptor used to refer to any gas discharge numerical display which contains an anode grid.

Vacuum Fluorescent Displays

Vacuum fluorescent display tubes share more in common with a cathode ray tube than they do with the Nixie tubes they tend to mimic. A VFD tube has a low voltage filament which is energized in a vacuum, causing electrons to 'boil' off. Metal plates covered with a phosphor coating are charged to between 25 and 50 volts, causing electrons leaving the filament to strike the plates and illuminate the phosphor. Later models of VFD also have a control grid, a metal screen that is placed between the digit and the filament. The control grid acts as a valve, allowing the digit to be turned on or off without the need to power down and re-heat the filament.

Anod IN-1
 Anod IN-1

The Anod IN-1, the USSR's first mass-produced Nixie tube, is a large end-view device with a 18mm digit height and an obscure 11-pin phenolic base. Unlike most Nixie tubes, the IN-1 fill gas contains no mercury, a circumstance which dramatically shortens the lifespan of the device to only a few thousand hours.

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Anod IN-2
 Anod IN-2

The Anod IN-2 is the Soviet analogue of the Burroughs B4021 miniature Nixie tube. The IN-2 shares its envelope with the Anod A-107, A-108 and A-109 dekatrons, and has a side nipple which exits at an angle to allow for horizontal stacking installations.

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Burroughs HB-106
 Burroughs HB-106

The Burroughs HB-106 is the first commercially manufactured Nixie tube, designed as a companion display for the Burroughs 6700 beam switching tube. Unlike National Union's competing 'Inditron' design, the HB-106 possesses an anode mesh which greatly simplifies the device's required drive circuitry. The HB-106 also has a silicone surround to increase visibility, and a distinctive red plastic label similar to the labels applied to early Haydu and Burroughs beam switching tubes. Although it retains the HB-prefixed Haydu part number, the example pictured here was manufactured after Burroughs had abandoned the Haydu branding on such tubes.

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Burroughs B4021L
 Burroughs B4021L

The B4021 is Burroughs' first miniature end-view Nixie tube. With an 8mm digit height and an envelope diameter of 17mm, the B4021 ranks as one of the smallest Nixie tubes ever manufactured. While the default B4021 has standard tube pins, the B4021L shown here is one of the few early Nixie tubes with flying leads.

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Burroughs B4998
 Burroughs B4998

With an envelope measuring only 15x10mm, the Burroughs B4998 is the smallest Nixie tube ever manufactured. The B4998 has the same 8mm digit height as the B4021, but the rectangular envelope reduces the tube's overall size and permits tighter horizontal stacking installations.

While the B4998 is impressively tiny, the integrated BIPCO driver module for this tube is surprisingly large, yet physically proportioned in such a way as to not undermine the small display area potential of the B4998.

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Burroughs B5440
 Burroughs B5440

Introduced in 1969, the side-viewable B5440 is a later example of Burroughs' Nixie tube product line. In addition to the B5440 base part number, Burroughs manufactured a range B544x variants, including the B5441 with dual decimal points, the inverse-mounted B5445, the B5441 and B5448 symbol displays, and the B5440A which lacks a top nipple.

The example pictured here is a second-source NL-5440, manufactured by National Electronics.

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Burroughs B5971
 Burroughs B5971

Though it resembles the commonly available B5991, the Burroughs B5971 is a segmented alphanumeric Nixie display, with a single plane of linear cathodes. Although the B5971 appears to have a 16-segment readout like later alphanumeric LED displays, it actually only has 13 distinct cathodes. The top and bottom segments are constructed of single cathode, and the center vertical segment is a single cathode as well. This arrangement prevents the display of some characters, such as a capital 'Y'.

Burroughs also manufactured the B7971, a large side-view alphanumeric Nixie tube used in Ultronic Lectrascan stock ticker displays.

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Burroughs B5991 / 8422
 Burroughs B5991 / 8422

Introduced in 1963, the Burroughs B5991 (EIA number 8422) is the ultimate workhorse among all Nixie tubes. Used in countless instruments over a ten year span, the B5991 is a rugged, compact, ultra-long life display in a form-fitting rectangular envelope. The B5991 was second-sourced by both National and Raytheon, and was adopted by Hewlett-Packard for use in their numerous rack-mount timers and counters. To this day, the B5991 remains one of the most commonly available USA-manufactured Nixie tubes.

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Burroughs 7153
 Burroughs 7153

The Burroughs 7153 is a fairly large end-view Nixie tube with a hemispherical envelope and a 20mm digit height. While the 7153 is a standard variant of this tube, Burroughs also manufactured the B6033 long life and B6091 long life wide angle variants. Unlike most other Burroughs Nixie tubes produced during the same period, which have a 170V maximum ionization voltage, the 7153 is rated at 250V.

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Burroughs B9012
 Burroughs B9012

Burroughs introduced the Pixie tube as a low cost alternative to the Nixie tube. Instead of having number-shaped cathodes and a complex internal construction, the Pixie tube has small metal stubs mounted directly to the top of each cathode pin, which glow beneath a metal screen with digit-shaped holes cut above each cathode. The Pixie tube sacrifices readability in exchange for a greatly simplified internal construction and correspondingly lower cost. Despite its affordability, the Pixie tube failed to achieve wide adoption, as most equipment manufacturers opted for the high quality readout of the Nixie tube regardless of the associated costs.

The Burroughs B9012 pictured here is an improved replacement for the original HB-105 Pixie tube. While the HB-105 and B9012 share a similar internal construction, the B9012 includes mercury in its fill gas, greatly improving the tube's lifespan. The B9012 also has a low-profile envelope, while the HB-105 is packaged in the same hemispherical envelope as the HB-106.

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Futaba 9CT06
 Futaba 9CT06

The Futaba 9CT06 is a miniature nine-digit seven-segment numerical VFD in a tubular envelope. Such displays were popular in the mid-1970s for use in calculators, but were superseded by planar VFDs and LCD displays. Casio, Sharp and other Japenese manufacturers produced numerous handheld calculators equipped with various models of Futaba tubular VFD.

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Futaba DM-20
 Futaba DM-20

The Futaba DM-20 is a three-color symbol matrix VFD, specifically designed for the Entex Galaxian 2 handheld game system. Futaba made a number of similar DM-series VFDs for Bandai, Coleco and Entex "mini arcade" systems, coupled to various Hitachi HD38800 series 4-bit microprocessors. Futaba DM-series VFDs feature custom symbols representing various video game artwork.

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Gazotron IN-12B
 Gazotron IN-12B

The Gazotron IN-12 is the Soviet equivalent of the ubiquitous Burroughs B5991/8422 rectangular end-view Nixie tube. Like the earlier IN-1, the IN-12 has an 18mm digit height, but has a much better tube-to-digit size ratio. Although the IN-12 is compatible with the B5991 socket, the presence of an underside nipple restricts it to sockets with a centrally located hole.

The IN-12 was manufactured in two variants: the IN-12A which does not have a decimal point, and the IN-12B (pictured here) which does.

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Gazotron IN-28
 Gazotron IN-28

The Gazotron IN-28 is a Soviet end-view single pixel indicator, designed to be assembled into large bitmap displays. The IN-28 shares its envelope with the IN-4 Nixie tube, but has a 7-pin flying lead base. The IN-28 is a high brightness device, suitable for visibility in outdoor environments.

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General Electric Y1938
 General Electric Y1938

Devices included in this entry:

General Electric Y1938 seven-segment VFD (engineering sample; pictured in thumbnail)
General Electric Y1938 seven-segment VFD
General Electric Y4102 overflow indicator VFD


Introduced in 1970, the General Electric Y1938 is a rare, early example of a USA-manufactured VFD. The Y1938 is a single-digit seven-segment display, packaged in a compact cylindrical envelope with a nine-pin miniature base. Such devices were developed as an alternative to Nixie tubes, which have higher voltage requirements and other undesirable electrical characteristics. Unlike later VFDs, the Y1938 lacks a control grid, making multiplexed operation impossible.

Y1938 prototypes have a substantially different internal construction than production variants, with the phosphor elements painted on a monolithic ceramic substrate. This superior construction method was likely abandoned to reduce manufacturing costs.

General Electric Y1938 Datasheet (PDF)

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Iseden DP89A
 Iseden DP89A

The Iseden DP89A is an unusual proto-planar VFD in a hermetic metal-and-glass envelope, with a unique dual 14-pin DIP base. The DP89A apparently saw limited adoption, as the only known application of this device is as the display of the Rockwell 61R handheld scientific calculator.

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National Union GI-10 'Inditron'
 National Union GI-10 'Inditron'

Introduced in 1954, the National Union GI-10 'Inditron' is an early Nixie-style numerical indicator tube, developed in parallel to (and possibly predating) the successful Burroughs design. Unlike a conventional Nixie tube, the GI-10 does not include an anode mesh, requiring an adjacent cathode to be pulled high to ignite the glow discharge. Additionally, the failure-prone numeral cathodes in the GI-10 are constructed of a delicate bent wire instead of a stamped plate. The GI-10 can be inserted into a conventional 9-pin tube socket, but provisions must be made for its long center anode pin. The combination of a short lifespan, convoluted drive requirements and non-standard basing doomed the GI-10 to obscurity, while the robust Burroughs Nixie tube enjoyed wide adoption.

Special thanks to Randall Logan for providing an excellent scan of the GI-10 datasheet.

National Union GI-10 Datasheet (PDF)

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NEC LD8113
 NEC LD8113

The NEC LD8113 is a medium-sized numeric VFD with an eighth vertical center segment and a 14mm digit height. This unusual segment arrangement allows the LD8113 to generate both numbers and a range of extra characters, including a '+' symbol and a more naturally shaped number '4'.

Similar eight-segment VFDs were used in the display of the Commodore C112 desktop calculator.

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Orzep IV-21
 Orzep IV-21

The Orzep IV-21 is the Soviet equivalent of Japanese calculator VFDs like the Futaba 9CT06. The IV-21 includes eight digits and decimal points, plus sign and overflow indicators.

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RFT Z560M
 RFT Z560M

The RFT Z560M is a typical Germany-manufactured end-view Nixie tube in a Compactron-style envelope. The Z560M is equivalent to many other medium-sized end-view Nixie tubes, including the Burroughs B5092 and 122P224, but adds a translucent red coating which increases readability.

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Reflector ILV2-5/7M2
 Reflector ILV2-5/7M2

The Reflector ILV2-5/7M2 is a Soviet-manufactured 5x7 RGB bitmap VFD with 105 discrete elements in a 5x21 arrangement, with three elements per pixel. Although it is a novel device, the irregular element spacing and a lack of stackability make the ILV2-5/7M2 impractical for most applications where RGB capabilities would be an advantage.

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Rodan MG-17F & MG-17G
 Rodan MG-17F & MG-17G

Devices included in this entry:

Rodan MG-17F seven-segment Nixie tube (pictured in thumbnail)
Rodan MG-17G seven-segment Nixie tube (pictured in thumbnail)


The Rodan MG-17F and MG-17G are seven-segment in-plane displays in a tubular envelope - transitional devices which fall between conventional Nixie tubes and Panaplex displays. These tubes were used in a number of calculators manufactured in the 1969-1971 timeframe, but were quickly superseded by the fully planar, multi-digit Burroughs Panaplex display.

The MG-17F has upper and lower decimal points, allowing it to be inversely mounted. The MG-17G has a shorter envelope, omits the upper decimal point, and has a simplified internal construction.

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Tung-Sol DT-1704B 'Digivac'
 Tung-Sol DT-1704B 'Digivac'

The Tung-Sol DT-1704B 'Digivac' is one of the earliest and most primitive VFDs known. Unlike most VFDs, the DT-1704B has no internal supports. Each segment consists of a rectangular phosphor-coated element, welded directly to a control pin. This gives the display segments the appearance of floating, but does little to enhance the display contrast. Like the equivalent GE Y1938, the DT-1704B has no control grid, and cannot be multiplexed.

Tung-Sol later introduced the DT-1704C, which includes an internal mica support behind the display segments.

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