A standard objective Digital sounder for fire, protection and industrial applications; the Sonos Sounder Beacon is Licensed to EN54. Common Recognition: VADs are intended to offer a universal warning signal that is definitely recognizable by Every person, regardless of their standard of hearing or cognitive means. Hearing Improvement System Prerequisite: https://www.firesense.co.uk/type/conventional-fire-system/conventional-sounders-vids-vads/