The most common and cheapest dimmer is a TRIAC. The down side is they generate undesirable amounts of Electro-Magnetic Interference (EMI). Trailing Edge (Reverse Phase or ELV) dimmers are more expensive but generate significantly less amounts of EMI compared to a TRIAC. In the U.S. most Trailing Edge dimmers require a neutral wire be run to the dimmer. A 0-10V dimmer uses low voltage control wires to dim; this usually requires an extra pair of wires to be run to every driver from the dimming module.