ORIGINS OF THE NIXIE TUBE
SCIENTIFIC AMERICAN
[From the June 1973 issue of Scientific American magazine, pages 66 and 67, written by Alan Sobel (at the time the article was written he was a member of the research department of Zenith Radio Corporation).]

What was needed was a means of displaying a number "in line" rather than scattered up and down several columns.

Of the devices that were designed in the mid-1950's to meet this requirement the most successful was a gas-discharge device called the Nixie tube. At the time the Nixie tube was introduced it was not at all certain that it would become the dominant digital device for electronic instruments. There were two major competitors: incandescent lamps and electroluminescent numbers. There were several ways in which incandescent lamps could be driven from the outputs of vacuum-tube counters, and the lamps could be used to illuminate masks or to edge-light plastic panels to produce a number display. The circuitry required to power these displays was more complicated and more costly than what was needed for the Nixie tube. Moreover, the incandescent indicators themselves were relatively expensive. The electroluminescent numbers were made from powdered phosphors that emit light when they are subjected to an electric field. Unfortunately the early electroluminescent lamps had a short and unpredictable lifetimes and they gradually faded as serious competitors to the Nixie tube.

The name Nixie came about accidentally. A draftsman making drawings of the tube labeled it NIX 1, for numeric indicator experimental No. 1. His colleagues began referring to it as "Nixie," and the name stuck. The tube contains 10 metal cathodes, each shaped to form a different number. The cathodes are insulated from one another and are stacked one behind the other. The anode is a metal mesh. The entire assembly is in a glass bulb that contains neon gas with a small amount of mercury. When an electric potential of about 180 volts is applied between the anode and any cathode, the gas near the cathode breaks down and emits light. With a proper choice of gas pressure and cathode dimensions almost all the light comes from the immediate vicinity of the energized cathode, and the result is a luminous orange-red number.

The Nixie tube was first marketed commercially in 1956. It is still sold by its originator, the Burroughs Corporation, and by Burroughs' licensees in many countries. It is available in a variety off sizes and is widely used in measuring instruments of all kinds and in office equipment such as calculators and copying machines. This tube has been successful because it is reliable and has a long lifetime. Because it is a familiar device to design engineers the Nixie tube continues to be sold in large numbers.

The voltages to operate Nixie tubes are provided by circuits called drivers. Originally Nixie tubes were designed to be driven by vacuum tubes, which themselves operate at high voltages. Modern integrated circuits, however, operate at very low voltages, and interface circuits are required to drive Nixie-tube displays. These driving circuits are readily available from a number of sources, but the need for interface circuits, which provide a high voltage, is one reason why the Nixie tube is being challenged.

HAYDU BROTHERS
George and Zoltan Haydu were great entrepreneurs, good inventors, genuine Hungarian patriots, and a part of northern New Jersey's industrial history. George even got shot in NYC by the Hungarian Secret police while leading an anti-Communist parade, and kept on marching. Great men, both. They did not, however, invent the numerical indicator tube based on gas discharge technology.

The Haydu Brothers made a lot of odd tubes for others, and developed many innovative products until being bought out by Burroughs in 1954 and moved to Plainfield, New Jersey from nearby Warren, New Jersey.

In their work, the Haydu Brothers employed a number of tube designers, mostly experienced men from New Jersey's cradle of American electron tube manufacture in Essex and Hudson Counties: DeForest, DuMont, RCA, and other area tube firms notably including National Union. The latter was formed in a survival-driven merger of Magnatron (Hoboken, New Jersey), Marathon (also of Hoboken), Sonatron (NYC) and Televocal (West New York, New Jersey) in 1929, as none were previously RCA licensees.

NATIONAL UNION
RCA was using its huge patent portfolio to kill off competitors in the tube industry, as well as in all other areas of electronic entertainment. Usually the litigation resulted in payment of back royalties, seizure of assets and/or bankruptcy, so the four little aforementioned firms acquiesced, joined to form National Union (NU), and acquired a single RCA license. It appears that RCA lawyers had a hand in putting the deal together.

National Union made very good tubes and had a decent development shop. Hygrade-Sylvania might have been bigger and in some ways, superior, but NU was fairly clever, and sometimes beat RCA to market with new types. They made a lot of tubes for the war effort, second-sourcing RCA, of course...

NUMERICAL INDICATORS
Somewhere in the early post WW-II period, the need for electronic numerical indicators became apparent; the existing electromechanical registers weren't suitable: NU came up with the Inditron tube (also linked from here, way down their list).

I wholly disagree with their statement that the G-10 was developed in the 1930s, as RCA hadn't even yet developed the T-6-1/2 noval 9-pin base upon which the G-10 sits. (The noval was a postwar outgrowth of RCA's pioneering 7-pin-through glass (T5-1/2 bulb) design first developed just before the war for portable radios... The noval base was released in 1948 to accommodate more complex / multi-section tubes, and became an industry standard. NU was licensed to use it, of course) Accordingly, I place the G-10 no earlier than 1948, although it is likely that some flying-lead experimental devices might have been built a year or two earlier.

I've seen G-10s in the hands of other tube collectors, and own a couple of ancient INDITRON variants (NIB) called G1-045A, here. Both are marked "Research Division, NU", patents pending. The green, black and white box is likely late 1940s, and has handwritten type numbering. These displays are in T6-1/2 bottles on 10-pin bases, with no keying, just a yellow paint mark for the user to abide by when installing the tube. Easy to goof!

No center pin in these, like the G-10 has, but rather an exhaust tubulation is there instead. That makes me think the G1-045A was designed to avoid the side tubulation, but I've not been able to establish which tube came first. My guess is that mine are lab variants, designed to use conventional tube envelopes and manufacturing equipment, including rotary Sealex machines. These look like very elongated Nixie tubes, missing the front mesh, and having lots of painted on insulation on the internal wiring to the various cathanodes. Trouble is, they needed a special 10-pin socket, and I've never, ever seen any of those.

The pre-Haydu tube most often cited is the National Union GI-10, not G-10 (sic) as I'd written. Perhaps "GI" might mean "gas indicator". After going downstairs and finding the carton with little gas bottles, sure enough the ones I have might well be GI-054A, and not G1-045A, but that is difficult to say for sure. The stamped yellow ink isn't very clear, and that is understandable as these are certainly handmade toys from time when the earth was still flat.

The NU INDITRONs seem quite difficult to find. In 40 years I've only seen a half dozen or so, including the ones here. Mine came unsolicited in a heap of postwar tube cartons from the estate of a good friend who liked tube audio, old radios and musclecars. I am certain that he never even noticed them, much less cared what they were. Sadly, all the NU 2A3 and NU 50 boxes were empty...

Given the close knit tube-design community in this area, one might expect the Haydu Brothers were well acquainted with NU's designs, and improved by adding a front cathode mesh to make driving the numerals simpler. Haydu often took R&D products and productized them for others, including RCA, in an early form of outsourcing. Who knows what went on between NU, Haydu and Burroughs? Government (AEC) money may have been involved, but that is just conjecture that needs discussion within the Tube Collectors Assocation.

Also by 1952 or so NU was getting out of vacuum tubes to become more diversified, and I have no information regarding patent issues, but suspect that Haydu must have legitimately acquired some rights to the underlying design and manufacturing technology. (NU, in 1965 bought Emerson TV & Radio, who had previously acquired the DuMont name. All were fine area companies, and I knew people who worked at each of them.)

PATENT
Patent 2,142,106, Signaling System and Glow Lamps Therefor, was filed on May 9, 1934 and awarded on January 3, 1939. The inventor is listed as Hans P. Boswau from Galion, Ohio. (Mr. Boswau appears to have been the chief engineer of the Lorain County Radio Corporation and the Lorain Telephone Company during the 1930s.)

From the patent:

This invention relates to signaling devices and more specifically to glow lamp indicators for selectively signaling numerals, letters or other characters or symbols.

The patent describes the operation of the device:

In the well-known space discharge devices or glow lamps, a pair of metallic electrodes are sealed within a glass bulb filled with neon, mercury, sodium or other suitable gases at a definite very low pressure. When a unidirectional (direct current) potential is applied to the electtrodes and gradually increased, the glow discharge will set in at a certain definite potential called an "igniting potential." The luminous glow discharge is produced by negative electrons and positive gas ions and takes place within a certain small distance from the exposed surface of the cathode or negative electrode, which appears to be surrounded or coated with a thin film of light. This film of light follows the contours of the cathode surface in all details.

When the potential is further increased, thbe glow discharge becomes somewhat brighter. When the potential is gradually reduced, the glow discharge is maintained down to a potential considerably below the igniting potential, until at a certain definite minimum potential the discharge ceases.

If an intermediate potential somewhere between the igniting and minimum potential is applied to the electrodes, there will be no glow discharge, but if the potential is momentarily raised to or above the igniting potential and thereafter reduced to the intermediate potential, the discharge will be started by the igniting potential and thereafter be maintained by the intermediate potential until the potential is reduced to or below the minimum potential. This characteristic of the glow lamp makes it possible to control the starting and stopping of the glow discharge by means of brief momentary impulses of high and low potentials, with the lamp normally connected to an intermediate potential.

Thus, the glow lmap may be lighted by the application of an igniting impulse and thereafter remains lit, until the potential is reduced momentarily below the minimum potential. This feature offers a means to control glow lamps without external holding relays or other means for keeping the lamp circuit closed with it is desired to have the lamp glow.

The fact that the exposed parts of the cathode of a glow lamp are entirely surrounded by a thin film of luminous discharge may be utilized to display any desired character by means of properly shaped cathodes. A cathode consisting of a wire shaped in the form of the numeral 1 will, when ignited, produce a luminous outline of the numeral 1, and similarly any other desired character may be formed.

The patent also describes a stock quotation system using a coding scheme adapted to the use of these numeric gas discharge tubes as the display device.

ANNOUNCEMENT
NIXIE - Electronic Read-Out Tube

The first mass-produced all-electronic "read-out" tube is now in volume production at Burroughs Corporation's Electronic Tube Division, Plainfield, N.J., the Company has announced. The tube, known as NIXIE, is described as a small, low-cost electron device which converts electronic signals directly to readable characters. It contains all the numeric digits, any one of which can be selected and displayed in a common viewing area. It can be triggered by Beam Switching Tubes or any suitable voltage source requiring approximately 1/4 watt.

Applications for the NIXIE tube include computer read-out, industrial control, electronic instrumentation, military electronic control, and channel selectors.

Unusually good readability is said to result from design features which provide a wide viewing angle and sharply defined digit contours. Other advantages claimed for the NIXIE are compactness, and a rugged construction capable of meeting military requirements for shock, vibration, and temperature.

According to the manufacturer, the NIXIE uses a minimum of power, circuitry and components and is inexpensive to install and maintain. It is believed by Burroughs to be the simplest all-electronic method of performing the read-out function.


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