Editing Remote control (section)

===Opto components and circuits===
[[Image:control-remote-spectrum.png|thumb|250px|The emission spectrum of a typical sound system remote control is in the near infrared.]]

[[File:Blue infrared light.jpg|thumb|250px|The infrared diode modulates at a speed corresponding to a particular function. When seen through a digital camera, the diode appears to be emitting pulses of purple light.]]

Most remote controls for electronic appliances use a near [[infrared]] [[LED|diode]] to emit a beam of light that reaches the device. A 940 [[Nanometre|nm]] wavelength LED is typical.<ref>{{cite web|url=https://clickermart.com/blogs/news/what-is-the-wavelength-of-the-infrared-used-in-remote-controls/|title=What is the Wavelength of the Infrared Used in Remote Controls?|date=18 December 2017|website=clickermart.com|access-date=15 October 2018}}</ref> This infrared light is not visible to the human eye but picked up by sensors on the receiving device. Video cameras see the diode as if it produces visible purple light. With a single channel (single-function, one-button) remote control the presence of a [[carrier signal]] can be used to trigger a function. For multi-channel (normal multi-function) remote controls more sophisticated procedures are necessary: one consists of modulating the carrier with signals of different frequencies. After the receiver demodulates the received signal, it applies the appropriate frequency filters to separate the respective signals. One can often hear the signals being modulated on the infrared carrier by operating a remote control in very close proximity to an [[AM radio]] not tuned to a station. Today, IR remote controls almost always use a pulse width modulated code, encoded and decoded by a digital computer: a command from a remote control consists of a short train of pulses of carrier-present and carrier-not-present of varying widths.