It can select indipendently between 2 ins for the left output and 2 ins for the right output, like A/B for Left and A/B for Right. It can be obviously considered as 2 mono 2to1 switches in a single unit.
Roy pointed me the fact that this module, together with the Stereo Switch, is only monophonic!
I had forgotten to check for polyphony, because I wanted to use them as switches for audio signals from outside the modulars, and i should have done them with a monophonic surface...