LED traffic light as a communications device

The visible light from an LED (light emitting diode) traffic light can be modulated and encoded with information. Hence, it can be used for the broadcasting of audio messages or any traffic or road information. Essentially all LED traffic lights can be used as communications devices. The paper focuses on the description of an audio information system made up of high brightness, visible light emitting diodes (LEDs) in which one or more LEDs are modulated and encoded with audio messages. The system also comprises a receiver combined with a speaker which is located at a distance from the LED traffic light. The receiver is designed to demodulate the optically transmitted audio information and broadcast the messages with the speaker. The optical link employs intensity modulation with direct detection. The audio information system implemented on an LED traffic light can provide the function of open space, wireless broadcasting of audio messages.