Electrical Questions? Ask an Electrician Online.
I wilk have your answer in a few moments.
Before you go to that expense lets go through a check list first.
The modem has to go inside. It does not install to the outside box.
You connect it to a new or the existing phone jack inside the trailer. It cannot be outside.
The wire from the inside goes to the red green terminals in the box outside
If you have an existing telephone the DSL and the telephone share the same two wires. It uses the same two for both. The DSL service is on top of the phone service. The "MODEM" is what separates the two.
Hope im making it clear. Its an unusual concept for most . Two different functions on the same pair of wires at the same time.