I have a Mag 10.

One switch is the up/down switch and the other(the white push-in button) is the breaker fuse. Normally you don't have to do anything with the the breaker fuse. If for some reason the automatic stop does not work and the ball slams into the pulley on the end of the boom, the breaker with trip before the motor burns out. When that happens, wait a minute and reset the switch and the downrigger will work again.

The positive ion control puts a +0.5v on the downrigger wire. One thing to remember with this design is that if you put a black box on this downrigger, the auto-stop feature won't work.