
They have to be connected to a phone for the length of the contract (usually 12 months). I had multiroom when I lived with my parents, they wouldn't run the phone cable through the house so it had to go up and over. Anyway, I rarely open any correspondence from Sky as my bill etc was always the same, I don't know what made me open this letter but I'm glad I did, it was a bill for over £100 for the month, as they said I'd unplugged the phone lines from the other 2 boxes and they were charging me full fare for each additional box. I demanded an engineer visit (foc) and it turned out the phone cable had corroded outside.
I've recently had another sky box put in to our bedroom, and because the engineers never fitted the phone cable when we moved in (outside of the initial 12 months), it is a condition of the multiroom to have all boxes connected. So I had to make it clear when ordering that the engineer would have to connect a phone line to both the existing HD box and the new one. He was there for nearly 2 hours, but did an excellent job.