The Rate of rise heat detector, HS-WS19L, is designed to sense the rapid of abnormal rise in temparatureof air. If ambient temperature rises rapidly, the air in chamber expends and preses the diaphram to close the contact point to give advanced warning. When a slower temparature change occurs, the expanded air escapes through a bleeding hole to keep the pressure balanced so what the fault alarm never occurs. Brand: Hooseki Product Type: HS-WS19L mia_ brsinaga@ yahoo.com Phone 085691398333, 021-40911748