Looking for a complete list of alarm codes

Specifically Alarm Code 75

"Check your connection to your ISDN service provider"
Do you have a PRI?

I have 2 PRI T1s... The Code 75 refers to a drop of a T?

That's what the book says. It may have been a momentary problem. Was your PRI service down?

Alarm 75 could indicate a "clocking slippage" and not a total loss of signal on the PRI as well.