A typical purpose electronic sounder for fire, safety and industrial applications; the Sonos Sounder Beacon is Licensed to EN54. Dr Zzeus Q&A: If fire alarm indicator products don't meet the essential expectations, is the procedure compliant? The sounder head ‘twists and clicks’ into the base on commissioning, avoiding the wiring https://www.firesense.co.uk/type/conventional-fire-system/conventional-sounders-vids-vads/