The Switch is a mechanical switch, actuated by the High and Low Level Sinker Switches.
A 2-wire electrical connection is used (220V, 7.5A or 110V, 15A). A choice of terminals is provided, so that the Switch is turned either OFF or ON at the High Level and vice versa:
For Pumping (ie switch ON when Low Level is reached) use Terminals A1 and A2. For Draining (ie switch on when High Level is reached) use Terminals B1 and B2.