Choosing category A or B is done when the system is initialized. It was only in certain versions of the switch as well. To get to category B, you need to default the switch and if I remember right, you need an init login. Load the orange card and login. The immediate and only choice you have is to choose A or B, then reset 4. This is fuzzy info because it's cold storage in some worn out brain cells.
Don't do it unless you have to.