Abstract: A make-before-break pressure switch has a pair of snap-acting discs separated by a travelling spacer. At a low level switching pressure, the travelling spacer is moved by the pressure sensing diaphragm to snap one disc for moving a contact blade to close a pair of contacts. On increasing pressure, the second disc is snapped at a high level switching pressure to cause a blade spring to go over-center and effect snap actuation of the contact blade to re-open the contacts. Upon decreasing pressure reverse operation occurs; and, the over-center blade snaps the blade to close the contacts which remain closed until a low level opening pressure is reached.