The Doorbell Fon connects between the incoming line and the house phones. The connection is similar to a security system hookup, except that it doesn't use the RJ31X jack. This presents a special problem for DSL since the Doorbell Fon must be wired ahead of the internal phone lines. You could use a standard alarm system DSL filter like this one (my website).
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You'll also need to wire in the RJ31X jack.
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The procedure isn't complicated but it's also not intuitive. I can sketch out a diagram for you if you need it.