Competing machines such as the Altair 8800 generally were programmed with front-mounted toggle switches and used indicator lights ( red LEDs, most commonly ) for output, and had to be extended with separate hardware to allow connection to a computer terminal or a teletypewriter machine.

The first LEDs were red and yellow, and higher-frequency diodes have been developed over time.

Until 1968, visible and infrared LEDs were extremely costly, on the order of US $ 200 per unit, and so had little practical use.

Although the LEDs were rather dim and not practical for use in direct sunlight, the technology proved to have major uses for alphanumeric displays and was integrated into HP's early handheld calculators.

The first commercial LEDs were commonly used as replacements for incandescent and neon indicator lamps, and in seven-segment displays, first in expensive equipment such as laboratory and electronics test equipment, then later in such appliances as TVs, radios, telephones, calculators, and even watches ( see list of signal uses ).

These red LEDs were bright enough only for use as indicators, as the light output was not enough to illuminate an area.

Most LEDs were made in the very common 5 mm T1¾ and 3 mm T1 packages, but with rising power output, it has grown increasingly necessary to shed excess heat to maintain reliability, so more complex packages have been adapted for efficient heat dissipation.

and 2002, processes for growing gallium nitride ( GaN ) LEDs on silicon were successfully demonstrated, yielding high power LEDs reported in January 2012.

Early red LEDs were notable for their short service life.

Yokoi opted for red LEDs because they were the cheapest ; Nintendo said a color display would have been prohibitively expensive.

" LEDs were also chosen for having the lowest drain on batteries, and for being the most striking color to see.

Nixie tubes were superseded in the 1970s by light-emitting diodes ( LEDs ) and vacuum fluorescent displays ( VFDs ), often in the form of seven-segment displays.

LEDs were better suited to the low voltages that integrated circuits used, which was an advantage for devices such as pocket calculators, digital watches, and handheld digital measurement instruments.

Also, LEDs were much smaller and sturdier, without a fragile glass envelope.

Also included were six 7-segment LEDs ( similar to those on a pocket calculator ) and a 24-key calculator-type keypad.

Around this time, Russian scientists also collaborated with NASA medical scientists who were looking at the use of LEDs as more suitable light sources, compared to lasers, for PDT applications.

In 2007, red LEDs were tested for the platform edge lights on the upper level.

Orange LEDs were tested at the platform edge on the lower level, before being replaced by red LEDs in 2008.

Even the white lights, which were typically single-chip LEDs, glowed with a faintly yellowish color that made them look cheap and unattractive.

Error codes were displayed on one of the first seven-segment displays ( 2 digits ) ever seen, built with lamps rather than LEDs.

" Rear tail lights were changed to " wave-guide " LEDs ( Hella, the OEM, refers to these lights as " CELIS "), while the side and rear turn signals were changed from amber lenses to clear.

In 2007, the original 16 colored floodlamps illuminating the concrete piers were replaced by energy-efficient and computer-controlled LEDs.

Each of the four pages can be selected using a button on the top right of the card, and one of four orange LEDs will light to indicate which page is currently selected.

RGB LEDs for backlighting are found in high end color proofing displays such as HP DreamColor LP2480zx monitor or selected HP EliteBook notebooks, as well as newer consumer grade displays such as Dell's Studio series laptops which have an optional RGB LED display.

* A vertical shutter speed scale with LEDs to indicate both the user selected and camera suggested shutter speed ( in ' M ' mode ) and the value selected (' P ' and ' A ' modes ) by the camera's metering system.

Unlike white LEDs, most CCFLs have an even-white spectral output resulting in better color gamut for the display.

LEDs are used as indicator lamps in many devices and are increasingly used for other lighting.

LEDs powerful enough for room lighting are relatively expensive and require more precise current and heat management than compact fluorescent lamp sources of comparable output.

In 1976, T. P. Pearsall created the first high-brightness, high-efficiency LEDs for optical fiber telecommunications by inventing new semiconductor materials specifically adapted to optical fiber transmission wavelengths.

The Monsanto Company was the first organization to mass-produce visible LEDs, using gallium arsenide phosphide ( GaAsP ) in 1968 to produce red LEDs suitable for indicators.

Packages for state-of-the-art high-power LEDs bear little resemblance to early LEDs.

Most manufacturers ' published ratings of LEDs are for an operating temperature of 25 ° C.

Because LEDs emit less heat than incandescent bulbs, they are an energy-efficient technology for uses such as in freezers and refrigerators.

Typical input and output devices include switches, relays, solenoids, LEDs, small or custom LCD displays, radio frequency devices, and sensors for data such as temperature, humidity, light level etc.

These volatile compounds are decomposed along with ammonia, arsine, phosphine and related hydrides on a heated substrate via metalorganic vapor phase epitaxy ( MOVPE ) process for applications such as light emitting diodes ( LEDs ) fabrication.

This item is part of a computer museum, and was populated with LEDs in 2008 for demonstration purposes only.

LEDs have allowed new text, video displays, and sensors to be developed, while their high switching rates are also useful in advanced communications technology.

Cree's XLamp XM-L LEDs, commercially available in 2011, produce 100 lumens per watt at their full power of 10 watts, and up to 160 lumens / watt at around 2 watts input power.

Because of their inefficiency, incandescent light bulbs are gradually being replaced in many applications by other types of electric lights, such as fluorescent lamps, compact fluorescent lamps ( CFL ), cold cathode fluorescent lamps ( CCFL ), high-intensity discharge lamps, and light-emitting diodes ( LEDs ).

It consists of a 2-D matrix of LEDs with their cathodes joined in rows and their anodes joined in columns ( or vice versa ).

Phosphorescent materials are known for their use in radar screens and glow-in-the-dark toys, whereas fluorescent materials are common in CRT and plasma video display screens, sensors, and white LEDs.

Most microscopes, however, have their own adjustable and controllable light source – often a halogen lamp, although illumination using LEDs and lasers are becoming a more common provision.

Note that while CRTs, plasma screens, and organic light-emitting diode displays generate their own light, liquid crystal displays ( LCDs ) like TFT screens require a backlight of either cold cathode fluorescent lamps or, more often today, LEDs.

Active optical systems triangulate positions by illuminating one LED at a time very quickly or multiple LEDs with software to identify them by their relative positions, somewhat akin to celestial navigation.

When moving the glow stick, timing differences between the on / off state of the different LEDs becomes evident, and the colors are separated into their separate components.

As the cost of LEDs decrease and their brightness increases, expect to see functional fishing lights consisting of large arrays of LEDs.

This was much more cryptic than the alphanumeric display of earlier models like the II / IID, III / IIID, IIP, and IIIP, as it was impossible to determine the meaning of the patterns of LEDs without comparing them against a manual ( or having their meaning memorized, which some technicians exposed to them often might actually do, intentionally or not ).

In some locations where public utility electricity or kerosene are not readily accessible or desirable, propane gas mantle lamps are still used, although the increased availability of alternative energy sources, such as solar panels and small scale wind generators, combined with increasing efficiency of lighting products, such as compact fluorescent lamps and LEDs are diminishing their use.

LEDs provide maximum battery life due to their energy efficiency, and recent technology has greatly increased the light output of LEDs.

Lite-On does manufacture and retail some products under their own name, LEDs and CD / DVD products.

These units do not use visual FSK to activate their red LEDs, but instead, they briefly " pick-up " the line at certain intervals ( normally, within two minutes of a new call ) to check for a " stuttered " dial tone.

Although LEDs are positive resistance devices, they have insufficient resistance to regulate their current consumption when operated from a voltage controlled source, so ballasts are used to control the current through the LED.