Particularly effective for the Deaf or hard of hearing, specifically in scenarios exactly where visual alarms might go unnoticed. Provision of telephones appropriate with hearing aids, marked With all the common ear and ‘T’ symbol and equipped with inductive couplers and quantity controls. A VAD can be a warning unit https://www.firesense.co.uk/type/conventional-fire-system/conventional-sounders-vids-vads/