A common function electronic sounder for hearth, protection and industrial purposes; the Sonos Sounder Beacon is Licensed to EN54. Set simply just, this guidance can make it apparent that where by a visible indicator is used as a Main alarm, it should be a VAD Licensed to EN 54-23 Unless https://www.firesense.co.uk/type/conventional-fire-system/conventional-sounders-vids-vads/