Hydroponic Grow Lights - Ballasts
Ballasts are power transformers which turn 240 volts into the right electricity to fire high power lamps, such as CMH, HPS and MH globes for use with hydroponic systems. Ballasts plug into a grow light reflector, then the lamp screws into the reflector. They can be magnetic or digital - the magnetic are cheaper but they use more power and run hotter. Digital ballasts usually have multiple light wattage settings and are more efficient - they are also silent.