In this paper, a novel tricolor dot matrix display system in which all the
light-emitting diodes (LEDs) are modulated and encoded with audio informati
on is presented. The novelty is on the concurrent use of the tricolor LED d
isplay for simultaneous visual message display and audio signal transmissio
n in a free-space optical link, This is a new generation of tricolor dot ma
trix displays where, in addition to the usual function of LED display, they
concurrently provide audio broadcasting through the visible light rays tra
nsmitted by the display panel or assembly,The system is comprised of a tric
olor dot matrix display panel with an interface circuit to a computer, an a
udio signal transmitter, and a receiver, It also comprises an executive pro
gram that runs on the computer for the display control of characters, decor
ative 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 oscillat
or is used to vary the frequency of on/off periods of the LEDs, The frequen
cy of flicker is high enough to be indistinguishable by human eye and, henc
e, display appears to be constantly illuminated.