One of the many uses of Infrared Technology is short range communications. It uses an infrared spectrum of light which is invisible to the naked eye. The device is fitted with infrared light-emitting diodes (LEDs) to emit infrared radiation which is focussed by a plastic lens into a narrow beam. The beam is modulated i.e. switched on and off, to encode the data. The receiver uses a silicon photodiode to convert the infrared radiation to an electric current. It responds only to the rapidly pulsing signal created by the transmitter, and filters out slowly changing infrared radiation from ambient light. It doesn’t penetrate walls and so can’t interfere with other devices in adjoining rooms. Before the Bluetooth technology, mobiles exchanged data using infrared but now the most common application of infrared technology is your everyday remote control.