Asus T4-P5G31A - Manual (Page 52)

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.
R
P5K18L-SE
P5K18L-SE Internal Audio Connector
CD
(black)
Right Audio Channel
Left Audio Channel
Ground
Ground