J17 - Digital Audio Out; J18 - Digital Audio In - Intel 440BX Manual

Hardware Setup
J17 – Digital Audio OUT
Connect to the external Audio Amplifier or Mini-Disk by
using optional SPDIF/OUT bracket/cable set, selectable
output signal level depends on the device needed.
Connect to pin1 and pin2 for 5V signal level or pin3 and
pin2 for 0.5V signal level.
Pin
1
2
3
J18 – Digital Audio IN
Connect to "DIGITAL AUDIO" port of the CD-ROM
drive by using the SPDIF/IN cable, which gives you the
non-distortion digital audio from CD-ROM. Connect to
pin1 and pin2 for 5V signal level or pin3 and pin2 for 0.5V
signal level.
Pin
1
2
3
1
J17
J18
Sound Pro
Chipset
23
Signals
5V Signal
Ground
0.5V Signal
Signals
5V Signal
Ground
0.5V Signal
1
J17
J18
I/O Chip
VGA
Chipset
+