Quote Originally Posted by Guy Roland View Post
It may be to split the bulbs. 4 bulb fixtures can be wired 2+2 what I mean is if you have 6 fixtures in your shop you can wire the two inside bulbs on each fixture to one switch and the outer 2 to a second switch.

This saves electricity as you can run half your lighting in the daytime or for normal work or turn on all bulbs for nightime or more critical work.
Standard switches are not made to switch the voltages present in ballast output leads, if you want to have 2-level illumination you need multiple ballasts & switch the ballasts 120 volt input.