Most of the consumer electronics like stereo equipment, lighting installations, camcorders and audio and video apparatus nowadays come with an infrared remote control. Infrared light is below the visible red that it is invisible to the naked eye and apart from this fact it is very much like the other light sources that operate under similar physics laws. And in almost all the cases, the infrared signal is produced by a LED source.



Infra red receive and transmit systems are normally reliable and inexpensive. But the interferences caused by other infrared sources could be an issue of a minor category. Interference can come from infrared audio systems which broadcast infrared signals continuously, from infrared remote controls and from fluorescent and other light sources as the ballast could result in infrared interference and in some case even light that are electronic ballast could result in interference problems. Interference can be avoided if the operating frequency of the electronic ballasts is chosen that the thirty six kilo hertz frequency area problem is out of question.

Normally the infrared remote controls come with a range of thirty two to forty kilo hertz modulated square wave that is used for communication. This square wave is sent to the infrared LED (IR transmitter). The data modulates the carried frequency in amplitude, normally entire on or off type modulation. The data rate lies between the fifty to thousand bits range, which depends greatly on the system used.

The universal infrared remote controls available these days send control information with the help of the infra red light. When the key of the infrared remote control is touched, the circuitry determines the infrared flash sequence corresponding to that particular key. The signal is then sent in the form of voltage sequences which turns a light emitting diode (infrared LED) on and off. The appliance the user points at whether it is a VCR or TV or stereo or DVD normally has an infrared light detector which picks the IR light signal which is then converted into an electrical signal and finally certain digital circuitry determines the functions that is required to be done according to the signal sequence. The universal infrared remote control needs to be very flexible so that it can handle the international standards to encode the commands used by the remote controls. They are the RC5 and RECS 80 codes.

Infrared remote control that has RC5 coding represents every command as a series of bits very similar to the bits that represent letters and numbers in computers. It has a uniform duration and uses the “biphase code". RECS eighty code makes use of the pulse length modulation, in which the information of the bits that has to be encoded is in the length of every pulse.