Leading you to an educated decision.
IR Remote Control
IR remote control units communicate using light waves in the Infra Red spectrum. The physical communication layer is formed by the emmiter (a photo diode) that emits the signal and a receiver (another photo diode) that receives the signal. The light waves are modulated by the emitter at a frequency of 40 KHz. This is done in order to cut out other sources of IR such as electric lamps, etc.