I give, what is it ?

Seems like I remember those things from years ago, but I think its something like a trip box, like if for some reason wires in the camp system should get crossed & short & that box will stop the short from getting to you RV.

I could stand corrected though, like a far distant memory that stuck with me. Now 10 minutes from now I might not remember this at all, boy gittin old is fun.
Neil