Techko's S187D Safe Pool Alarm is designed to monitor a gate, door, window or other entryway to you pool area. A high output 110 dB alarm siren sounds when the magnetic contact is broken without pressing the adult bypass button. Two sensors are included so that you can have your sliding glass door open, with your screen door shut, leaving the alarm active. This alarm is always in protective mode and will sound the instant a door, window or gate is opened and will continue until the bypass button is triggered. The S187D is ETL listed and approved under UL 2017 standards.