Here is the problem. I have 2 lines with hum on them. Where ever I put the lines the trouble follows. There are lines 804 and 810. If I disconnect the Legend side the hum goes away. But by moving the lines to different line ports and the trouble follows. , We are fighting with ATT that they have a problem on these 2 lines but they refuse to do anything about it. Is there a meter or something I can use on these lines to prove it is their problem and not mine?? And yes the cards have been replaced,pwr supply and cabinet.