Asus T3-P5G43 - Manual (Page 62)

4-8 Chapter 4: Motherboard Info
5. Optical drive audio connector (4-pin CD)
These connectors allow you to receive stereo audio input from sound sources
such as a CD-ROM, TV tuner, or MPEG card.
P5Q18L
CD
Right Audio Channel
GND
GND
Left Audio Channel
P5Q18L Internal audio connector
P5Q18L
SPDIF_OUT
+5
V
SPDIFOU
T
GND
P5Q18L Digital audio connector
6. Digital audio connector (4-pin SPDIF_OUT)
This connector is for the S/PDIF audio module to allow digital sound output.
Connect one end of the S/PDIF audio cable to this connector and the other
end to the S/PDIF module.
The S/PDIF out module is purchased separately.