Diodes are used to tie into the towed vehicles brake light, running light and turn signal wiring, and connect it to the motorhome. Diodes permit electrical current to flow in only one direction - from the motorhome to the towed vehicle's taillights - Prevents electrical feedback and the damage it can cause to both vehicle's electronics. If you're using a diode, why not use the best ROADMASTER's Hy-Power diodes have a heavy-duty, powder-coated aluminum heat sink, and each diode is protected against the elements - all components are housed inside an epoxy-sealed, powder-coated aluminum case.