The days of the old humming, magnetic core&coil-type HID Ballasts have come to an end. The Digital (electronic) Ballast is the latest in HID Ballast innovation. The Digital Ballasts are more efficient, quieter, cooler and softer/easier on the HID bulb all the while allowing for a much smaller and neater package.
The Digital Ballasts do not have any of the usual transformers or capacitors; instead these ballasts have electronic circuitry doing the same job, only much more efficiently using significantly less current. The Digital Ballast have the capability of self diagnostic and reset, including specific protection circuits to detect various lamp-and ballast-fault conditions allowing to safely shutdown or reset the ballast. When the ballast fires the HID bulb it sends full power to the cold HID bulb. Over time, this shortens the HID bulb life and reduces the output and life span of the increases the power over the next few seconds until the HID bulb has reached full brightness. This is also known as soft starting, which minimizes the damage to the HID bulb and increases its life. After one year of use the usable light coming from HID bulb being used in the coil type ballast would have lost over 10% more usable light over the same period of time.