SUCO pressure switches PLUS NAMUR are potential-free and are supplied directly via the measuring circuit (operating current IB). The live parts are electrically isolated from the housing, i.e. there is no electrical connection between the switching contact and the housing. Due to the resistor circuits, a current level is permanently present at the output of the pressure switch, irrespective of whether the contact is activated or not. This is also referred to as the closed current principle.