If your second line is a dedicated line, it will not. To make it part of the other phone line, they have to come out and rewire it or some such. I had our second line canceled when we got DSL and currently all the extensions on that line are dead. Sometime when I have the spare money or am willing to have them add it to my phone bill and increase my monthly payments I am going to have them come out and do that. I last discussed this with them last summer and the fee from Ameritech was about 99.00 plus 25 – 40 per outlet, I can’t recall for sure.