+100 First, any of your 120V AC items inside the trailer come through this device. Secondly, any 12V DC items inside the trailer are powered by this device.
When I bought my 1977 Trillium
1300, it never had a battery. But it had 120V outlets and 12V DC lights. I replaced the old worn out PD6911, and added a battery for dry camping
. I rarely have hook ups when I camp. Even if I often did have hookups, I still prefer a battery so I have a choice of where to camp. Many of my favorite camping areas: National and State Parks, Forest Service and BLM camping do not have hookups.