Usually, dimming ballasts and dimming LED power supplies use 0-10V control signals to control dimming functions. In many cases, the dimming range of the power supply or ballast is limited. If the light output can only be dimmed from 100% down to 10%, there must be a switch or relay available to kill power to the system and turn the light completely off. Most 0-10V controllers offer either a built-in line voltage relay or an external line voltage relay. Depending on the application, these options should be considered.