Dual Output Electrical Adapter, Adds 7-Way RV Blade to 4-Way FlatThere are several different types of connectors used to supply power from a tow vehicle's electrical system to a trailer's wiring system. Some trailers only need the bare essentials running lights, brake lights and turn signals while others require a connection for reverse lights, electric brakes and auxiliary power. With connectors ranging from simple to complex, it may be the case that the connection between your vehicle and your trailer is not a