In the words of the distributor.

Meet the Sun System Galaxy electronic ballast.

This state-of-the-art ballast is manufactured to provide todayâ??s serious grower with maximum flexibility & performance. The Galaxyâ?˘ Select-a-Wattâ?˘ is different than any other â??dimmableâ?ť electronic ballast on the market. The Galaxyâ?˘ brand name carries a strong reputation of reliability and performance. There are three ways to use the Select-a-Wattâ?˘ feature:

â?˘ It will properly drive a 400, 600 or 1000 watt lamp to ANSI specifications. For example: Set the switch to 400 watts, insert a 400 watt lamp into your socket and the ballast will operate the 400 watt lamp. The ballast will similarly operate 600 or 1000 watt lamps.

â?˘ The second option for this ballast is dimming a 1000 watt lamp. Adjust the switch to 400 or 600 watts and the ballast will dim the 1000 watt lamp by 40 or 60%.

â?˘ The Turbo Charge feature will increase the output of a 1000 watt lamp (only) by approximately 10%. You will achieve peak performance, but this may decrease your lamp life.

Lamps are only dimmable on wattages lower than the specified lamp wattage. A 1000 watt lamp can be dimmed down to 600 watt or 400 watt. A 600 watt lamp can be dimmed down to 400 watt, but cannot be over-driven to 1000 watts.

Turbo Charge is designed for 1000 watt lamps only. Do not use with 400 watt or 600 watt lamps. This can be hazardous.

Multi-Watt: 1000W, 600W, 400W
Dimmable
What I gather is this is the ONLY digital ballast that does all this.