This has been working for seven years. Since yesterday Customer cannot make outgoing calls ('All lines busy") and incoming calls ring busy. Telco says equipment issue. The DTI card has a yellow LED on it at the top - not normal. As soon as I put into loop back mode from the smart jack back to the DTI card card goes normal green. Thus I figured a Telco issue so tomorrow I have to fight it out with them and their sophisticated test equipment.Problem is their smart jack looks normal as well - clean and green. How do I prove beyond a shadow of a doubt it is not the DTI card or is it?