Specifically productive for the Deaf or hard of Listening to, especially in situations where Visible alarms might go unnoticed. Set just, this steerage makes it crystal clear that in which a visible indicator is utilized being a primary alarm, it have to be a VAD Qualified to EN 54-23 Until https://www.firesense.co.uk/type/conventional-fire-system/conventional-sounders-vids-vads/