Supplementary to Audible Alarms: VADs are especially efficient in high-sounds parts or the place hearing protection is worn, supplementing traditional audible alarms. A VAD or Visible alarm unit is usually a form of emergency notify method that gives a visual cue to people today for the duration of an crisis. https://www.firesense.co.uk/type/addressable-fire-system/addressable-sounders-vids-vads/