Diodes are frequently used in wiring kits to prevent the backflow of current to the electrical system of the towed vehicle or motorhome; however, many newer vehicles now use a multiplex wiring system, whereby multiple electrical signals may be sent down a single wire. If an ordinary diode is used in these applications, then the bulb will illuminate as though the vehicle is braking whenever the taillights are on. That is, you can't tell the difference between the brake lights and running lights. Smart Diodes correctly modulate the voltage to activate only the intended circuit. The result is vehicle lighting that looks and functions as intended. Each vehicle requires two Smart Diodes. Vehicles with LED lights require a different kit than those with incandescent bulbs. Installers can choose a two-pack of Smart Diodes and provide their own wiring and wiring supplies. Alternatively, use our complete wiring kit that features two Smart Diodes, a wiring harness to run the electricity from the front of the vehicle to the rear taillights, split loom, ring terminals and other supplies.