A basic function Digital sounder for fire, security and industrial purposes; the Sonos Sounder Beacon is Accredited to EN54. Dr Zzeus Q&A: If hearth alarm indicator devices tend not to meet the expected specifications, is the technique compliant? Merged sounder and visual indicator bases for conventional hearth alarms are gadgets https://www.firesense.co.uk/type/conventional-fire-system/conventional-sounders-vids-vads/