The Regulator is an Machine added by GregTech 5 used in automation.
It needs to be supplied with Energy to work.
The Regulator is used as follows:
The first 9 Slots hold items. It can only be filled with one stack per item type with automation.
The middle 9 Slots can be programmed to at what stacksize the item should be outputted.
The last 9 Slots set into what Slot of the target inventory the item is put.
This allows 9 items needing different stacksizes to be processed inside the same machine. Especially GregTechs Centrifuge and Electrolyzer have many recipes like that.