How does a remote control work?

  1. I'm specifically interested in television remote controls, garage door opener remote controls, and car door remote controls.

    I know that the remote control must send a signal somehow to the television, garage door, or car door respectively. But what type of signal does each type of remote control signal? I mean, is it a radio wave or what?
  2. jcsd
  3. DrClaude

    DrClaude 2,403
    Science Advisor
    Homework Helper
    Gold Member

  4. Different ones use different techniques. TV remote controls are fairly fun and straight forward. They typically switch an infrared LED on and off at a 44kHz rate. A receiver in the TV picks up infrared and is tuned to 44kHz.
    The 44khz signal is called a carrier. Using it helps the TV distinguish the difference between steady sources of light, like sunlight, and the remote.
    To get message across, the carrier is turned of and on in a sequence that's unique to the TV brand and function.
    Garage doors and cars do the same thing with a radio signal (the carrier), but most of these remotes only use each code once and then move to another code in a very long list. The opener or car only uses each code once, and then rejects it from there on. This keeps thieves from using a receiver to steal the code and reuse it.

    Left over remotes are pretty common. I really encourage you to take one apart to look at. You'll find a little LED in the TV/VCR/Cable remotes, and a loop in car remotes that is used as an antenna.

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