Are there any markings or words by the switch? There are a couple of things it could be. The most common one would be IN/OUT which if you are connecting that end into your TV would be set to in, if you are connecting it to the output of your sat box it would be set to out.
Also bear in mind that not all SCART plugs are connected in the same way, in that some have more pins than others. They all fit the SCART sockets on the devices, but they may not perform all the required functions.