Infrared is a light that is normally invisible to people, (it would be reddish of you could see it) but devices such as light-emitting diodes (LEDs) can easily create an infrared beam.
This infrared beam is used as a method of remotely controlling electronic devices such as televisions. It works by adding a control code on to the light beam. A light sensor in the television senses the infra-red and extracts the control code from it. This code then changes the relevant setting such as channel selection or volume control.
You will also find infra-red control being used in shops for automatically opening doors. This works because anything warm - including people - give off infra-red (heat).
A sensor above the door senses the infra-red and opens the door.
Infra-red is mainly used for close-range control - a few yards at most. If the distance is greater then radio control is normally used.
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