Barco RCVDS 800 (again)

OK, so it appears that the RCVDS 800 is controlled by the projector? Does anyone know HOW? Studying the pinout published a while back, it looks like there's a serial link.

Why do they have the buttons on the front if you can't use them to switch the channels?!?!?

Of course, the power supply just fried itself, so maybe I don't have to fix it.

(If anyone has a schematic I can study, that would also be nice).