Editing Remote control (section)

==Technique==
The main technology used in home remote controls is [[infrared communication|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 but can be seen through a digital camera, video camera or phone camera. The transmitter in the remote control handset sends out a stream of pulses of infrared light when the user presses a button on the handset. A transmitter is often a [[light-emitting diode]] (LED) which is built into the pointing end of the remote control handset. The infrared light pulses form a pattern unique to that button. The receiver in the device recognizes the pattern and causes the device to respond accordingly.<ref>ICT Roger Crawford – Heinemann IGCSE – Chapter 1 page 16</ref>

===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.

===Consumer electronics infrared protocols===
Different manufacturers of infrared remote controls use different protocols to transmit the infrared commands. The [[RC-5]] [[Communications protocol|protocol]] that has its origins within Philips, uses, for instance, a total of 14 bits for each button press. The bit pattern is modulated onto a [[carrier frequency]] that, again, can be different for different manufacturers and standards, in the case of RC-5, the carrier is 36&nbsp;kHz. Other consumer infrared protocols include the various versions of SIRCS used by Sony, the RC-6 from Philips, the [[Ruwido]] R-Step, and the NEC TC101 protocol.

===Infrared, line of sight and operating angle===
Since infrared (IR) remote controls use light, they require line of sight to operate the destination device. The signal can, however, be reflected by mirrors, just like any other light source. If operation is required where no line of sight is possible, for instance when controlling equipment in another room or installed in a cabinet, many brands of IR extenders are available for this on the market. Most of these have an IR receiver, picking up the IR signal and relaying it via radio waves to the remote part, which has an IR transmitter mimicking the original IR control. Infrared receivers also tend to have a more or less limited operating angle, which mainly depends on the optical characteristics of the [[phototransistor]]. However, it is easy to increase the operating angle using a matte transparent object in front of the receiver.

===Radio remote control systems===
[[Image:Garage-door-opener-remote-control.png|thumb|250px|The exterior and interior layout of the remote control for a garage door opener]]

Radio remote control (RF remote control) is used to control distant objects using a variety of radio signals transmitted by the remote control device. As a complementary method to infrared remote controls, the radio remote control is used with electric garage door or gate openers, automatic barrier systems, burglar alarms and industrial automation systems. Standards used for RF remotes are: [[Bluetooth]] [[Bluetooth profile#Audio/Video Remote Control Profile (AVRCP)|AVRCP]], [[Zigbee]] (RF4CE), [[Z-Wave]]. Most remote controls use their own coding, transmitting from 8 to 100 or more pulses, fixed or [[Rolling code]], using [[On-off keying|OOK]] or [[Frequency-shift keying|FSK]] modulation. Also, transmitters or receivers can be ''universal'', meaning they are able to work with many different codings. In this case, the transmitter is normally called a ''universal remote control duplicator'' because it is able to copy existing remote controls, while the receiver is called a ''[[universal receiver]]'' because it works with almost any remote control in the market.

A radio remote control system commonly has two parts: transmit and receive. The transmitter part is divided into two parts, the RF remote control and the transmitter module. This allows the transmitter module to be used as a component in a larger application. The transmitter module is small, but users must have detailed knowledge to use it; combined with the RF remote control it is much simpler to use.

The receiver is generally one of two types: a super-regenerative receiver or a [[superheterodyne]]. The super-regenerative receiver works like that of an intermittent oscillation detection circuit. The superheterodyne works like the one in a radio receiver. The superheterodyne receiver is used because of its stability, high sensitivity and it has relatively good anti-interference ability, a small package and lower price.