Product that splits 1000W into 2x500W

Whats the items name that does this?

its actually a lumatek ballast or a splitter you can buy them from greners.com and the splitter is like 20 bucks, but you need a special ballast. if you get the lumatek ballast it splits it into two "basically" ballast from a single 1000w and you need to run it on 240v circuit though.

What it does is allows you two run two bloom rooms off of one ballast. But you can only run one room at a time.

If one is on the other must be off. n so forth.