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 (brake and taillights, for example). This is called variable voltage.

If your vehicle has variable voltage, you need Smart Diodes. If it doesn't, choose from the options below.