Alright my Dad's house is really huge, it covers about an acre, and he's got a mansion. Don't worry about the mansion the problem is with the front house. The front house shares an apartment (1 floor), my dad just constructed 3 rooms more for one of his friends(the apartment). Now if he's going to put DSL phone splitters for all of the phone lines will the apartment side need filters, too? The apartment has its phone cable joined with his house's phone line, but the apartment uses a different phone number. The problem is that since the phone lines are joined i'm thinking that it will need filters as well. Can anyone help me out with this issue?