This system is designed for twin outboard installations using outboards without Aux outputs. It allows the port engine to charge the port start battery and the house battery when the port VSR is engaged. Also allows the starboard engine to charge the starboard start battery and the house battery when the starboard VSR is engaged, giving a combined charge from 2 outboards into the house battery until the voltage regulators on both engines control the charge. Will also allow the house battery to be charged if running on one engine. Dependability and durability. Quality and control.