Our 2000 3255RL came from the factory with a doorbell. It didn't work at first when we bought the Monty previously enjoyed, but we changed batteries and it works fine now. But, other wireless doorbells will set it off. We were parked next to Chaser at the rally in Mt. Shasta. They were on the show and tell tour and every time someone rang their doorbell ours rang too.
So, other wireless devices set them off, and rain getting in the outside button will set it off also.
Virgil and Karen
2000 3255RL
2006 F350 PSD 4x4