Commonly, remote controls are Consumer IR devices used to issue commands from a distance to televisions or other consumer electronics such as stereo systems, DVD players and dimmers. Remote controls for these devices are usually small wireless handheld objects with an array of buttons for adjusting various settings such as television channel, track number, and volume. In fact, for the majority of modern devices with this kind of control, the remote control contains all the function controls while the controlled device itself has only a handful of essential primary controls. Most of these remote controls communicate to their respective devices via infrared signals and a few via radio signals. Earlier remote controls in 1973 used ultrasonic tones. The remote control code, and thus the required remote control device, is usually specific to a product line, but there are universal remotes, which emulate the remote control made for most major brand devices.
The main technology used in home remote controls is infrared (IR) light. The signal between a remote control handset and the device it controls consists of pulses of infrared light, which is invisible to the human eye.
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