We have had issues with 4 conductor line cords and Tech support(Vertical and ESI) always says to change them out to single pair line cords. Which in some cases works as i'm sure i'm not the only person that has seen it. In some instance i have some 10' and 14' ones that come with phones but its always the one that goes the whole way around the room. I've gotten around by putting a coupler in place then using the cord with the phone but a coupler is just another point of failure. I can't find them anywhere or even just the silver line cord itself and ends to make it. I may be just calling it the wrong thing?