Asus T3-PH1 - Manual (Page 48)

4-8 Chapter 4: Motherboard Info
5. Digital audio connector (4-1 pin SPDIF_OUT)
This connector is for an additional Sony/Philips Digital Interface
(S/PDIF) port(s). Connect the S/PDIF Out cable to this connector,
then connect to the S/PDIF module of the system chassis.
6. 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.
R
Digital Audio Connector
+5V SPDIFOU
T
GN
D
SPDIF_OUT
R
Internal Audio Connector
CD
(black)
Right
A
udio Channel
Left
A
udio Channel
Ground Ground