The SR-500 Stingl switch safety vacuum release system monitors the vacuum on the suction side of your pool or spa pump, to reduce the risk of accidental entrapment. When a blockage occurs in the main drain or skimmer, a sudden rise in vacuum will cause the SR-500 to shut down pump operation immediatley and activate an audible alarm. The vacuum is monitored 128 times per second, and the power is monitored 50-60 times per second, ensuring continues power detection. The pump will remain off with the alarm sounding until manually reset. No pool or spa should be without the SR-500. The Stingl switch meets are current codes and standards for SVRS's on new and existing pools and spas. It can act as a pool controller with a programmable timer, or as a stand alone SVRS working in conjunction with an existing pool controller. The SR-500 will work with any sized pump, and is easy to install. Complies with ASME/ANSI 112.19.17.