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Nixie tube

(Numeric Indicator eXperimental-1) The first electronic digital readout. Developed by Burroughs in the 1950s, a Nixie tube is a vacuum tube filled with neon that contains 10 wires formed in the shape of the digits 0 through 9. The wires are attached to cathodes on one end and a wire mesh anode on the other. When voltage in the range of 170 to 250 volts is applied to the wire, it glows. Nixie tubes gave way to LED displays in the 1970s. See LED.

Nixie Tubes
Today, using old tubes and modern chips, some people build their own Nixie tube clocks such as this one. (Image courtesy of Mike's Electric Stuff,


(Light Emitting Diode) A display and lighting technology used in almost every electrical and electronic product on the market, from a tiny on/off light to digital readouts, flashlights, traffic lights and perimeter lighting. LEDs are also used as the light source in multimode fibers, optical mice and laser-class printers. See LED lightbulb.

In the early 1970s, red LEDs were used in the first digital watches, but were superseded by lower-power LCDs within a few years. LEDs still use more power than LCDs, but less power than incandescent bulbs. They also last for decades and are virtually indestructible.

LEDs and LCDs coexist on countless devices where the LEDs provide the status lights, and the LCDs display data. In addition, white or red, green and blue LEDs are used as the backlight source on many LCD TV sets. See LCD, LED TV and flat panel TV.

Several Colors
LEDs are semiconductor diodes that typically emit a single wavelength of light when charged with electricity. Originally red, today, several colors can be generated based on the material used for the tips of the probes. Aluminum indium gallium phosphide (AlInGaP) is used for red and yellow. Indium gallium nitride (InGaN) is used for green and blue, and with the addition of phosphor, for white light as well. See digital billboard, OLED, IRED, LED printer, fiber optics glossary and Nixie tube.

An LED Unit
The LED is the semiconductor die, which sits in a reflective cup that is also a heat sink. Voltage is applied to the LED, and electrons and holes in the two semiconductor layers are attracted to each other at the junction. When they combine, photons are created.

LEDs and LCDs Are Used Together
Small alphanumeric readouts can be LED or LCD, but the indicator lights on countless products are LEDs.

First LED Watch
The Synchronar 2100 was the first LED watch and the first solar powered watch. It preceded Hamilton's famous Pulsar LED watch in 1970. (Image courtesy of the private collection of Peter Wenzig.)

LEDs Offer Flexibility
A flick of a switch changes the ambience in this Los Angeles bedroom (top), while the Westin Hotel staircase in Shanghai (bottom) cycles colors or becomes a musical light show. (Images courtesy of Color Kinetics, Inc., Bedroom design and photo by Steven Cordrey. Staircase by Light Directions Hong Kong, photo by Friendly Light.)

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