Fire Angel ST-623E-R Thermoptek Smoke Alarm with 5-year batteries & Escape light. The extra bright light beam & loud clear alarm from the Fire Angel ST-623E will ensure you & your family are alerted to danger & are guided to safety. The Thermoptek multi-sensor technology which pairs the the very latest in optical sensing with thermal enhancement reacts to fire in under half of the time of a standard alarm. This alarm cannot be connected to other alarms in your home.