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Indicators: Gas Filled, Neon, Argon

Ernst Erb Otmar Jung 
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Papers » Radio-History, beginning 1909 » Indicators: Gas Filled, Neon, Argon
Michael Watterson
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10.Oct.11 18:12

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Types of Neon Indicator and other Gas Discharge Indicator Geissler tube edited from Wikipedia

Neon was discovered in 1898 by William Ramsey. The first commercial neon lamps were made about 1910. But in the late 19th Century there was much experimention with low pressure gas discharge and different gasses with many ornamental lamps made such as the example on the right (from a Victorian painting as colour photography was very rare).

Neon and  other gases need a particular voltage to be reached before ANY current flows. This is the "striking" voltage. The voltage will then try to drop to a constant lower value depending on gas and to an extent construction. For this reason a gas discharge tube has a negative resistance and must have a series resistor to limit current. Below a certain current the discharge will stop and the indicator go out. The voltage above this point is the sustaining voltage.

Basic Neon Indicator or "Annunciator"

This property of neons is used for combination counter/display such as the Dekatron and also as Releaxation Oscillators and Capacitor Leakage testers.

The Strike voltage is lowered by light, radiation, RF fields, UV or a third electrode. The cold cathode thyratron uses a trigger wire to initiate the "Turning on" much like a Unijunction transistor or Thyristor. However even miniature Thyratrons the size of small neons are not commonly used as indicators. 

Larger bulbs with Cross or flame shaped elements are still manufatured. In the past a wide range of neon lamp shapes were produced.

Today (2011) the Plasma Panel is on wane for domestic video as the LCD are now as good if not better and cheaper to make.

Even the humble Neon Indicator for mains is often now replaced by LED, though some new products still have neon on/off indicators (annunciators).

Broadcasting to the Public started in about 1921 and Neon signs sold in the USA from about 1923. However it wsa more widespread use of the Superhet radio that Manufacturers wanted a "tuning indicator"

1931 to 1935 Neon Tuning rods

Demo by Joe Sousa

Two Tuneon tubes owned by a friend. Note how black glass has turned.

There is a suggestion that these didn't work very well. With usage the glass all neon tubes will go black.  The rare VG1 annular neon tuning indicator. (identical to the Visi-glow) 1934 is more a "Magic Eye" shape. The true (and effective) "Magic Eye" (A miniature beam deflected CRT type triode) was developed in 1934 and common by 1935.


Russian Bargraphs

These are the IN-9 (12mA),and IN-13 (4mA=FSD)

The year of introduction and year ceased production is unknown. The IN-9 is two wire, smaller and less sensitive. The IN-13 has a third "trigger" or "pilot" wire to enable strike at a lower HT  than would otherwise be the case.  They are available in Neon (pinky/orange) or Argon (purple/violet). 

IN-9 10mA is about 100mm. Max is 12mA

The bargraph length is proportional to current. They use rather too much power for battery equipment.

The larger but more sensitive IN-13, FSD is 4mA


With use the bargraph glass will blacken from bombardment with Neon or Argon ions.



Dekatrons, Nixies and other Numeric Neon based displays.


Read also these related articles


This article was edited 12.Oct.11 12:51 by Michael Watterson .

Michael Watterson
IRL  Articles: 821
Schem.: 623
Pict.: 2383
11.Oct.11 16:15

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The early Nixie displays were made by a small vacuum tube manufacturer called Haydu Brothers Laboratories, and introduced in 1955 by Burroughs Corporation, who purchased Haydu and owned the name Nixie as a trademark. Nixie tubes used an entire shaped character for each digit or letter to be displayed.

Many Burroughs and other US Nixie tubes are available as NOS (New Old Stock). The Russians appear to have copied many US types and created others. Some Russian Nixies use a copy of the "5" flipped upside done as the "2". Russian stock may be newer NOS. Beware of ex-equipment Nixies for Restoration, Repair or new projects as the glass blackens. Another problem is more than one digit on at the same time. This is alleged to be caused by "swarf" in the tube, but a gentle tap or shake can sometimes  cure it  whatever the real reason is.

Model Display Ch mm Comment
ins-1 Annunciator   End dot (e.g. Decimal point)
in-1 Numerals 18 End view Nixie
in-2 Numerals   End view Nixie (pins)
in-3 Annunciator   Side dot (e.g. Decimal point)
in-4 Numerals   End view Nixie (pins)
in-6 Numerals   Nixie (wire)
in-7 Symbols   End view n + m A V M O ~ K —
in-7a Symbols   End view n K - m % + M
in-7b Symbols   End view W V Hz S
in-8 Numerals   End view Nixie (pins)
in-8-2 Numerals   End view Nixie (wire)
in-9 Bargraph   12mA (wire)
in-12a Numerals   End view (pins)
in-12b Numerals   End view (wire)
in-13 Bargraph   4mA with Pilot (wire)
in-14 Numerals   Nixie (wire)
in-15a Symbols   W F Hz S H Ω A
in-16 Numerals   Nixie
in-17 Numerals 10 Miniature Nixie (wire)
in-18 Numerals   Nixie (pins)
in-19 Numeric 25 Nixie (wire)
in-19a Symbols   Nixie p, n, m, µ, k, M, %, °C
in-19b Symbols   ?, Hz, F, H, V, S, T, Ω
in-19v Symbols   Nixie + - A/B _ < % Π dB
in-22 Numerals   End view Nixie (wire)
in-24 Annunciator   short bar "Fuse style"


Russian parts usually are marked in Cyrillic so

in-19a is marked ИН-19А
in-19b is marked ИН-19Б
in-19v is marked ИН-19B
ins-1 might be in bag / box if bulk as ИНС-1
(Transliteration of cyrillic often represented by using lower case)



More unusual Russian gas based displays
Model Type Display Comment
mth90 Annunciator 1 dot Thyratron: Wires pre-cut with balls of solder
th5b (ТХ5Б) Annunciator 1 dot Thyratron
its1a 7 Segment 1 digit Thyratron: -300VDC, 100VDC, and 50VDC but 5V control. Looks like VFD due to green phosphor. Self-latching
itm2m Annunciator 4 x 4 Thyratron: Coloured Matrix
in-28 Lamp 1 dot building large dot matrix. Very bright
31 mm, 13ma @ 175V


Commonly available (eBay Autumn 2011) Russian "dot" Annunciators
ins-1 in-3 mth90 th5b in-28

(Images edited and processed from larger photographs of Ukrainian sellers of NOS,
so "fair use" for illustrative & comparison purposes)

Common Neon
(with AC, DC only one rod is lit)

This article was edited 12.Oct.11 15:38 by Michael Watterson .

Michael Watterson
IRL  Articles: 821
Schem.: 623
Pict.: 2383
30.Jul.15 18:28

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See also the RR145 tuning indicator used in the Blaupunkt 4W95 radio and perhaps others in 1936, a related idea to the Tuneon.

There are some articles in German.  Perhaps the bar varies in length with current due to a slight angle of the electrodes. A minimum current is required so there is usually an adjustment potentiometer.

Suggestion by  Prof. Dr.-Ing. Dietmar Rudolph.