Didn't know any still existed!
None of my .PDF mention the 12 port. The mention the T-1, Dual Density board, the DID adapters.
If I remember correctly you connect to them as you would any SPV...
I cannot find the installation manual, that's where defaulting would be found rather than the programming manual.
I would suggest looking at all User Mailboxes, Voice Mail Greetings, Broadcast Announcements and System List and delete and recreate.
The System Admin Guide is helpful on rebuilding.
Sheesh, I haven't seen a Sprint Protege since 2003!