This is a really good question on the third PRI, I'm going to add a third T-1 Card next week at a local college with a 7.1 XC with MCDN. I have a PRI in Slot 1 and a T-1 configured as an SL-1 Tie Line to a second facility. I just purchased a refurbished T-1 Card that is release 01-J, will this card work or should I call my supplier tomorrow?
Also on this topic, can I configure the third T-1 card as PRI-A so they don't have to use a third pool code to access it?