Dsl is sensitive to the signal to noise ratio. however not too sensitive. Your house wiring can have one or two branches on the line and it will still go through. The problem comes when you have a whole house full of branches on the line, and many unterminated jacks which are otherwise live, but have no dsl terminators on them.
This is not a diagram to spec, I have just been a tech at LMi.net for about 7 years. We were covad's second customer after sun, and well I have seen a lot of dsl lines work, and a lot of dsl lines not work.
One of the most common sistuations that I see has to do with the "Inside Wiring". Covad wants to fix this with a covad dispatch where they charge you $250 for 15 min worth of work, and then $80 an hour after that. But the upside is that it should work when the tech leaves. We have one client (a school with children chewing on the telephone wires) which has needed a covad tech out multiple times over the years.
