Augustus_McCrae said: I know.
you obviously don't get it.
If you had only one switch, instead of two, then:
X-- would equal ON
-X- would equal OFF
--X would equal OUT OF PHASE
But, you don't...you have two switches, with 9 possible positions (one of which is OFF OFF)
X-- X-- and --X --X are the same, because they are both ON, but not out of phase with one another.