Tecmark Adjustable PSI Pressure SwitchThese switches convert a pressure signal to an electrical output in response to a change in pressure and movement of an elastomeric diaphragm which opens and closes an electrical circuit based on a set pressure. 3 spade connections allow either a simple on off configuration or the extra connection point can be used to toggle a dual speed application. Usually mounted in the heater tube, it can also be found in the plumbing leading to the heater. The