The Pro Tools Hardware Setup lets you select the
Clock Source for the system.
If you are recording an analog signal directly into Pro Tools, you will usually use the Pro Tools
Internal clock source.
If you are transferring material into Pro Tools from an external digital device, or if you utilize a common house clock signal, you will synchronize Pro Tools to that digital device or common signal.
Depending on your audio interface, external options can include
AES/EBU [Encl],
S/PDIF,
Optical [Encl],
AES/EBU 1–8,
TDIF,
ADAT, and
Word Clock. For details, see the guide for your audio interface.