Abstract: A pressure switch comprising a housing having a pressure chamber, a port communicating with the pressure chamber and a recessed throat located where the port communicates with the chamber. A flexible diaphragm is disposed within the housing adjacent the pressure chamber, and an electric switch is mounted to the housing. A pressure plate is disposed between the diaphragm and the port. The pressure plate has a first surface contoured to mate with a portion of the diaphragm and a second surface facing the port having a plurality of projections extending from the second surface. The projections are dimensioned to engage the throat portion and maintain the second surface therefrom. The projections define passageways where the port communicates with the chamber when the projections engage the throat.