Nvidia 400 - Manual (Page 65)

Drivers Installation
Page 6-5
<Figure 7>
SPDIF-In:
7. This page shows S/PDIF IN function on your system.
a. Click "Auto Lock" to detect S/PDIF input and display its information.
b. Check "Real-time S/PDIF-In monitor" to listen to the S/PDIF IN signal
through Line-out connector.
<Figure 8>
SPDIF-Out:
8. This page lets you choose the type of audio source that will appear on the
S/PDIF-out connector.