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"Nixie Tubes"


" Invented by two brothers, the Haydus, who later sold their company to Burroughs, these tubes had a stack of formed numerals, each on an almost invisible supporting structure. A selected numeral would shine with a neon glow. Burroughs had the Nixie at its research center in Paoli, Pa., by 1954. Though the Nixie required a high-voltage supply of at least 170 Vdc, a numeral could be switched on with as little as 20 V. The tube consumed no more than about a watt and it soon took over almost all digital-display applications. Virtually every digital instrument adopted the Nixie until the light-emitting diode came along. It cost about $10, but the price per digit soon plummeted. "

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As a child I was often fascinated with blinking lights. My brother once wired our Christmas tree with 4 different strings of lights and switched them on an off with a motor and micro switches. This was about 1960. My dad had many friends with electrical tendencies. One guy we visited often, had a miniature radio tower that had neon lamps that would blink in sequence.

As a child I played with neons and "B" batteries (67 1/2 Volts) and made many versions of counters and neon relaxation oscillators.

Later, in about 1965, we moved to Florida so my dad could work at the Kennedy Space Center on the Apollo missions.

We met many fascinating people. An engineer that my dad worked with, built the first digital clock that I had ever seen in a home. It had tons of 6 volt incandescent lamps wired to telephone style relays. Once every minute, his clock would click and the flash of light would move to the next level. Every ten minutes, I'd get to watch the minutes carry over to the next column of lights. I remember patiently waiting until midnight so that I could watch the stepping relays all get reset to 12:00.

Of course his readout was in the "columnar" fashion of that era, one lamp above the other, stepping in sequence until the digit column climbed to "9", then the flash of light zipped back to the bottom to start all over again. Wonderful!

On arrival in Merritt Island, My dad, an avid electronics collector, amateur radio operator and experimenter, found Hopkins Electronics in Cocoa Florida. John Hopkins bought all sorts of high-tech surplus from the Space Center and nearby Patrick Air Force Base. It was probably at Hopkins that I saw my first nixie tube.

The Beckman DCU

Many forms of digital indicators were in use at the time. Probably the most popular was the Beckman DCU (Digital Counting Unit) This was a module that could count from 0 to 9 at a maximum rate of abut 100 Khz. They were built on a tall, narrow steel frame, just wide enough to hold a 9 pin tube socket on the back. Five of the 9 pin sockets were mounted above each other and the five 12AU7 tubes extended out of the back of the module. On the bottom was an 8 pin "Octal socket" style plug that allowed the module to plug into the system chassis. On the front of the module was a piece of plastic with the numbers 0 through 9 with neon lamps behind each one in the columnar style. Several modules could be stacked side to side for multiple digits of readout. Frequency counters and digital volt meters were built with the Beckman DCU's. Later I even saw this tube based counter with a seven segment (neon readout).

Non-Linear Systems

Another type of readout that was prevalent at the time was the edge-lit engraved plastic display. This readout had 10 plates of plastic, in a stack, with the numerals engraved in them and edge lit by individual lamps. One company that used this readout was Non-Linear Systems. They had a voltmeter that used stepping relays to balance a bridge. The readouts were connected to the steppers and when the clicking finally stopped you had the digital display of the voltage in question.

"Parity Generator / Checker"

As was the norm at the time, Many parts of the complex launch operations system were built in rack mount sub systems. A cool readout that I first saw in a thing called a Parity Generator / Checker was the rear projection display. This display used a piece of film with the digits printed on it. Starting at the back of the display was a bank of 12 incandescent lamps. In front of them was the film with 10 digits and 2 extra characters, usually + and -. In front of the film was a piece of plastic with 12 lenses that pointed to the rear projection screen located on the front of the display. When stacked side by side they made quite a nice display.