ST98-2 is a sensor to detect glass breaking. It provides maximum reliability and ignores any other sound/noisy but glass breaking, since it alerts when a detected sound matches one of the variety glass breaking sound images recorded in its memory. This appliance is not intended for use by persons (including children ) with reduced physical, sensory or mental cababilities, or lack of experience and knowledge, unless they have been given supervision or instruction concerning use of the appliance by a person responsible for their safety. children should be supervised to ensure that they do not play with the appliance. Features : Very high noise immunity; Omnidirectional sensitivity allows mounting on ceiling or walls; Three LED , red- alarm, green- power, green reception; Easy to install and adjust.