There is a switch behind your warantee sticker on the back of your unit. You have to be careful as to not void your warantee. It does not require any soldering or anything. It was added to create a greater convince to those who are installing them in RV's and boats.
You still have to ground the parking brake wire(green) to the chasis. I would suggest grounding it at the same spot you ground the whole unit(black wire)