The Light Timer controls either lighting systems with a trigger cord, or standard and electronic ballasts (two 600W or one 1000W at 120V). Day cycles (ON cycles) last 12 or 18 hours, as selected by the user. An internal rechargeable battery maintains the cycles in the event of a power outage. 3 position slide switch to select on/off cycles (corresponding to Day/Night cycles). Features 18 and 12 hour light schedules with a reset position to start a new ON cycle.