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An infrared light-emitting diode (LED) is not used to light up screens and monitors the way other LEDs are; instead, it is often used for non-visual applications and for nighttime illumination. The application of an infrared LED depends on its nanometers (nm), or its wavelength, with the common usage being between 808nm and 940nm. Infrared LED devices are used in everyday life in TV remote controllers and automated card readers. The use of infrared LEDs can be separated into two types: direct and reflecting, and the manner in which the infrared LED and the receiving diode interact determines the LED's uses.
At the lower end of the infrared frequency, 808nm, infrared LEDs are commonly used in non-visual applications but also are found in security cameras. Solid-state lasers and medical lasers and appliances function with this infrared frequency. Infrared illumination also is possible here, allowing security cameras to function at night without light, though the image they capture is usually low-resolution. At 830nm, this infrared light is used for automated card readers at subways and hotels.
Between 840nm and 870nm, infrared LEDs are found more commonly in visual applications. These LEDs are used in waterproof cameras and in both daytime and nighttime security cameras at stores and crossroads. The non-visual application at this wavelength is mostly seen in silent alarm systems and door phones.
The highest infrared LED signal, 940nm, is the one consumers most often use. This is the LED responsible for the functionality of remote controls, including those used with televisions and digital video disc (DVD) players. Wireless game controllers also belong on this list. Any appliance that uses a remote control with infrared technology uses this LED signal.
To get an infrared LED to work, one of two control methods must be employed. Direct light has the emitting LED in the control device, and the receiving diode in the receiving device, and the emitting device does not need to point directly at the receiving device. This method is the modern method; it is more convenient to use, because the user does not have to directly point the controller at the appliance.
The older method, reflecting light, has both diodes present in the controller unit. With this type of controller, the controller device must point precisely at the appliance for it to work, or it will not catch the infrared reflection. While this is not as convenient, it does allow for a longer functional distance between devices.
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