I have a site that all of a sudden calls are coming in and the ring is solid meaning a straight ring until you pick up, then no one is there. The lines originate from a T1 that then breaks out to analog. The carrier supplies the T1. The DSU 2 seems healthy.

It sounds like the carrier. They will swear it isn't but 99 percent of problems that occur on T-1 circuits are the Carrier
especially when the circuit is up and working like it should then all of a sudden there's problems. Call the carrier and tell them to fix it..insist it;'s their problem. I've always found a threat of getting the T-1 service from someone else works well too...if they play the "It's not us" game.

I agree. I have never seen a DSU do this before. It's like phantom calls inbound,
straight ring with no pauses, and then no one there.

plug a single line set in to the line and see what it does. A butt set would probably work but I would use a 2500 set to be certain. That should prove who owns the trouble. I'd bet it's the provider.
mark

Turns out it was line port 5 on the dsu that was causing the issue.