Depending on the version, pressure switches use medium pressure to provide electrical feedback, i. e. to connect or disconnect electrical devices or lamps. Pressure switch uses springs and diaphragm to control at what pressure the switch is triggered. The springs forces are opposing the pressure of the inlet medium. The spring preload correlates with the pressure at which the switch makes electrical contact. When the pressure drops, the switch is reset to its original state. Typical applications are pneumatic control systems, diverse applications in pneumatic braking systems or door opening systems. 10 different HELLA part numbers for WABCO air brake systems. Different applications for most common 24 V applications: Mercedes, MAN, Iveco, Scania, Volvo, Renault, Neoplan, Setra, Irisbus, Solaris, Evobus, Irsisbus.