Pressure-wave switches are electro-pneumatic converters which convert a positive or negative pressure wave into an electrical contact or pulse. Actuation of the pressure-wave source generates a pressure wave which is transformed into an electri-cal pulse by a diaphragm inside the pressure-wave switch. If the switch is designed with normally open contact, the diaphragm contact will press against the contact screw and thus make electrical contact. In the case of a normally closed contact, the closed contact opens when the diaphragm is deformed.
Contact is made briefly, since the pressure wave escapes through an adjustable valve opening in the pressure-wave switch. This valve ensures that the volume of air in the signaling element is bal-anced in order to avoid erroneous triggering. Transient changes in air volume may be caused by changes in atmospheric pressure or temperature fluctuations, and are of no consequence.
