I have four seperate buildings and have a USR modem in each switch cabinet. I've been able to dial in to our main building for quite a while, however lately when trying to reach this particular switch, I get a hand shake then a squeeling noise. Connection/dial up to other switches are fine. I have switched out the modem with a known good one, configured exactly as the others and still have the same problem. I'm thinking it has something to do with the Option 11 switch but I'm not sure what. Any suggestions?