Automatically combines or isolates battery banks, no more old fashioned 1,2, All switch! This convenient and affordable kit gives you both an automatic charging relay and a dual purpose battery disconnect switch. The simple to use switch has 3 positions, OFF, ON, and COMBINED. OFF disconnects all loads from BOTH the engine and house batteries. ON connects the engine to the engine battery and the house loads to the house battery. Combined connects both batteries together to all loads to allow emergency engine starting from the house battery. Before now it took 3 switches and a bunch of wiring to provide these functions.