Ideally used with center-positive applications. Some applications will require insulating the bushing from the chassis, so that the shell of the plug won't short to ground.

Center Lug = Center Pin
Short Lug = Sleeve/Bushing ("shell")
Long Lug = Battery Lug (not used if you're not using a battery)

Tech's notes: "The switching portion allows you to wire to the battery. Then the circuit to the battery will open whenever something is plugged in, preserving battery life."