Both of mine do. They work off the brake light system, intercepts the signal from the switch. That's what tells it to apply brakes, but it's just on and off, can't tell how hard you are applying them. so you need the right setting on the control box so when you lightly apply the vehicles brakes the trailer is not locking up, but also when your coming down a hill the trailer brakes assist in stopping.
I usually fiddle around with mine when I first get on the road, using the manual button on the controller and no vehicle brakes, I set it so the trailer brakes would slow down the truck and trailer to eventually stop both.
I have to do this often because the set ups on my 2 trailers are much different. Also a different setting going to the quarry empty and returning loaded.
JB