The rear switch is an out-of-phase switch and it's on when pointing to the head stock. When the phase switcher is on, the pickup selector is out of the way, because you anyway need both pickups for that.
The one switch in the middle is the coil-splitter. It still does work when the out-of-phase switch is on. An interesting thing is, that the coil splitting doesn't work absolutely. The second coils are laid on ground with a capacitor in between. So it gets a more bassier sound, because low frequencies of the switched away coil are still going it's way to the output jack, while higher frequencies, which pass the capacitor more easily, are short cut. With this, the hum cancelling abilities of the humbuckers are reduced but not completely gone in the single coil mode.
Because the second tone control does filter low frequencies, one can get a more thin single coil sound too.
Here's a sight to the electronics (click at the picture for more!)