The Switch Selection (KWT) is a toggle between which switch branches receive commands when the Throw Switch Button (WGT) is pressed together with double or single slip switches. The problem lies with the fact that these switches are actually two physical switches, but are operated using a single button.
The two buttons "a/b" and "c/d" operate like radio buttons: pressing the "a/b" button changes the current selection to a/b switches, while pressing "c/d" changes the current selection to c/d branches. A light above each button indicates the current selection.
The a/b switches are the switches that open to the left, while the c/d switches open to the right.