A remote control is an electronic device used for the remote operation of a machine. It is used to issue commands from a distance to televisions or other consumer electronics such as stereo systems and DVD players. These are small wireless handheld objects with an array of buttons for adjusting various settings such as television channel, track number, and volume. It uses a infrared diode to emit a beam of light that reaches the device. This light is invisible to the human eye but carries signals that are detected by the appliance, as well as by the sensor of a digital camera. They are usually powered by small AAA or AA size batteries.