Edwards Fire Alarm Bells are specially designed for fire alarm applications. The gongs are made of selected alloy steel to give the loud, resonant tones necessary in fire alarm systems. Two gong sizes are available to overcome different ambient noise level. The Fire Alarm Bells are of the underdome type with heavy duty mechanisms. Each bell is supplied with a mounting plate that fits any standard single-gang opening (see Installation Data). For weather-proof application Edwards offers an optional surface weatherproof back box. Refer to the Specification chart for applicability and catalog number of the weatherproof back box for the respective bell.