1. Allow 1 ballast to run 2 lamps, 2 ballasts to run 4 lamps 2. Controlled by timer for effortless changeover Lamp A & Lamp B This "Switch Box 4" is a dual unit, can be used up to 2 ballasts to flip swicthing lamps A&B and lamps C&DThe Switch Box 4 can be used for:1) 1 ballast to run 2 lamps A & B, 1 on and 1 off at a time, controlled by built in timer.2) 2 individual ballasts to run 4 lamps A & ...