System Configuration : I/O Setup : I/O Setup Pages : Output Page

Output Page
The Output page of the I/O Setup lets you create and assign Pro Tools Output channels to send audio to the physical outputs of your audio hardware.
Configure output signal path names and formats on the Output page. Output channels can have overlapping output paths. Output names, channel widths, and physical output assignments are saved with the system and the session, and can be recalled from either.