Provides 4-way selection for battery 1 / 2 / both, and off. The switch itself is very durable and rated for massive output. It features removable windows on all four sides to cater for whatever cabling arrangement you have. Alternator Field Disconnect (AFD) protects your alternator when switching batteries in and out of the circuit. By disconnecting the alternator moments before the battery (moments after when re-engaging), there’s always a load on the alternator to protect the regulation circuitry.