The Gentex 8243PH is a photoelectric system smoke detector listed for releasing device service. It's designed for 24V hardwired use. This Gentex smoke alarm features a temporal 3 (T3) audible signal for evacuation. This model features a universal mount that can be use for ceiling or wall applications. This Gentex smoke alarm also includes auxiliary Form A/Form C relay contacts for initiating remote functions and annunciation. Plus, it also includes an isolated (activates connected panels or annunciators) 135deg; heat thermal alarm. This Gentex smoke detector is a latching (manual reset) model.