The PSP20 uses the pump motor as a sensor to protect swimmers from the dangers of pool & spa drain entrapment. This is the only anti-entrapment device available that comes with a no-nuisance trip guarantee! The PSP20 is simple to install and setup. The unit is supplied as a fully-assembled control panel designed to be installed between an existing pump control panel and the pump motor. Installation typically takes less than one hour and programming and calibration take just minutes using the patented ‘Auto Set’ feature.