Asus G series E-Manual page 21

Microphone input jack port
The microphone input jack port is used to connect your
Notebook PC to an external microphone.
Headphone output and S/PDIF output combo jack port
This port allows you to connect your Notebook PC to amplified
speakers or headphones. You can also use this port to connect
your Notebook PC to Sony/Philips Digital Interconnect Format
(S/PDIF) compliant devices.
Notebook PC E-Manual
21