Have a site that's had line Issues from day one. All have been with the Lec, until the customer said they were getting a screech on the lines every so offten. They came out and found static on the lines, unlpug them from ATM16 the static goes away.We replaced the ATM16, and now after the lines are in the system after a min. or so there is a tone heard on the lines almost a ring but not. As far as we can tell you can still dial in/out on the lines. Remove the line with the ring noise from the system and it goes away. Any ideas? Could this be a bad ground?