Plugs directly into the existing harness and there is no need to splice and hard-wire into bike's wiring Takes the electrical load away from the bike's electrical/computer circuitryallowing the trailer to draw current direct from the battery Features a separate 7 Amp relay for each of the four lighting functions--if one goes badthe rest remain functional Since this system works as an isolator and has an in-line fuse on the battery lineit prevents any surges or shorts from feeding back to the bike Relay converter prevents the need to get a separate 5-4 converter For 4 wire trailers only