Asus PCI Express Audio Card Xonar DX - Manual (Page 9)

9 ASUS Xonar DX Quick Installation Guide
English
1.4.3 Connecting digital speakers
SPDIF Out
You can also use a coaxial cable for a S/PDIF connection. Just plug the coaxial
RCA male connector to the S/PDIF-Out combo jack and connect the other end
into the coaxial S/PDIF input on your decoder.
Plug the optical TOSLINK adaptor into the S/PDIF-Out combo connector. Then,
connect your decoder’s S/PDIF in port to the optical adaptor with the TOSLINK
optical cable.
1.4.4 Connecting Line-In audio sources
SPDIF Out
Line In