 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 a 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.