There usually called FlipFlop Boxes and they work with relay's/contactors many hydro shops sell them but for 4 light flip the go for like 400 bucks total ripoff when you can build one yourself from 150 to 200 or less if you just want to flip say 2 l000 watter's. I tried to get info on how to build one but dont know what type of relay I need if I knew the relays I could build one and make a how to............check picture to see what one looks like.......