CURT Truck Backup Alarm for 7-Way RV Blade Trailer Wiring Model 57727CURT Truck Backup Alarm for 7 Way RV Blade Trailer Wiring Model 57727 There 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