Tricolor light-emitting diode dot matrix display system with audio output

In this paper, a novel tricolor dot matrix display system in which all the light-emitting diodes (LEDs) are modulated and encoded with audio information is presented. The novelty is on the concurrent use of the tricolor LED display for simultaneous visual message display and audio signal transmission in a free-space optical link. This is a new generation of tricolor dot matrix displays where, in addition to the usual function of LED display, they concurrently provide audio broadcasting through the visible light rays transmitted by the display panel or assembly. The system is comprised of a tricolor dot matrix display panel with an interface circuit to a computer, an audio signal transmitter, and a receiver. It also comprises an executive program that runs on the computer for the display control of characters, decorative pattern or messages on the display panel. The receiver is designed to demodulate the optically transmitted audio information, and reproduce the messages with the speaker For modulating emission of the LEDs, an oscillator is used to vary the frequency of on/off periods of the LEDs. The frequency of flicker is high enough to be indistinguishable by human eye and, hence, display appears to be constantly illuminated.