This device allows temporary isolation of house loads from the engine circuit during engine cranking to protect sensitive electronics. It automatically combines battery banks during the charging cycle and isolates them while discharging. 12/24 Volt auto ranging voltage input. Hermetically sealed contacts/vaporproof/ignition protected for use aboard gasoline powered boats. Remote LED output indicates relay state away from ACR; LED light indicates when batteries are combined. Supports high-output alternators up to 120A.