The B-7971 is a very large alphanumeric display tube developed by Burroughs, originally designed for use in stock tickers. Unlike regular Nixie tubes with numerals arranged on a stack, the B-7971 contains 14 individual segments that can be combined to display every letter of the English alphabet as well as the digits 0 through 9. An additional segment in the bottom can be used to display an underscore.

Known for its exceptional longevity, with later models—distinguished by an “antenna” on the anode cage—supposedly lasting even longer, the B-7971’s has become a popular choice among collectors for creating large Nixie clocks. Since the tube’s total current draw varies with the number of segments lit, a single anode resistor cannot effectively limit the current. Instead, each cathode must be connected to its own resistor. The datasheet suggests using different resistor values for different segments to ensure uniform brightness. The most frequent failure mode of a B-7971 appears to be two or more cathodes shorting together. This may occur due to physical impact or the tube being overdriven for prolonged periodes of time. New old stock of B-7971 tubes is virtually nonexistent, as nearly all units available today have been salvaged from the aforementioned stock tickers.

The E1T is a decadic counting tube developed by Philips, predating the invention of gas-filled Dekatrons. Each pulse advances the tube’s internal count by one and generates a voltage spike, which can be used to trigger specific actions. Internally, the E1T operates as a small cathode ray tube with a ribbon-shaped electron beam that occupies one of ten stable positions. The current position of the beam is indicated as a glowing strip, with each position marked with its corresponding value on a piece of film affixed to the tube’s glass envelope. The tube’s envelope is coated with a transparent protective layer, which is prone to cracking over time, particularly in damp environments. Consequently, E1Ts in pristine condition have become increasingly rare.

When the Nixie tube was introduced in the 1950s, it faced a significant drawback: its driving circuitry required transistors with relatively high breakdown voltages capable of handling the elevated operating voltages. At the time, such transistors were not widely available. This limitation created a demand for an alternative display technology that could operate with low-voltage, low-current logic circuitry. The solution was the Pixie tube, initially designated as the Z550M and later renamed the ZM1050.

The MG-19B is a tiny, segmented neon-filled display tube produced by Rodan and marketed under the Elfin brand, designed for use in small electronic instruments. It features two additional diagonal segments, enabling it to display the digits ‘1’ and ‘7’ more naturally, as well as certain other alphanumeric characters. The tube also includes a right decimal point. Unlike Nixie tubes, each cathode in the MG-19B requires an individual resistor, as the current needed varies with the number of illuminated segments. With a 180V breakdown voltage and a recommended 230V anode voltage, the tube operates at significantly higher voltages than most Nixie tubes. This made driving the MG-19B more complex, as affordable high-voltage transistors were not readily available when the tube was introduced.

The OmniRay SAO M 40 is a so-called Sphericular Optic Display. While similar in both appereance and operation to projection displays like the IEE one-plane readout, the theory behind the M 40 is vastly different. It employs the principle of geometric optics to produce a character on a flat viewing screen. The screen area is subdivided into more than a thousand tiny convex lenses, each focusing light from its specific focal plane. Characters are displayed by illuminating only certain sections of the screen from different angles, which selectively allows light to pass through areas, producing a character composed of many tiny dots. A comprehensive explanation of the operational theory behind this device is available in the description of a similar model manufactured by Burroughs, accessible via the link provided below.