This is a matrix switch to handle display between the monitor and projector, plus the desktop PC and a BYOD laptop. It’s on its side, so everything is rotated 90 degrees. On the left (top) you’ll see labels for PC 1 and PC 2. These are the two computer inputs. One is plugged into the back of the CPU in the cabinet. The other is the VGA + audio cabled on top of the desk. Then there are buttons for 1 and 2. 1 is the monitor, and 2 is the projector. So, to have the desktop PC mirrored to both, the lights should both be on at the top, aligned with PC 1.