Visible fire alarm notification appliances may operate in either the public or private mode. They are most often used in the following situations: As a supplement to audible fire alarm notification appliances.
Where ambient sound levels may make it difficult to hear audible fire alarm notification appliances.
Where required by other codes or standards.
Where there may be hearing impaired individuals who cannot hear audible fire alarm notification appliances.
As a method of calling attention to a signal received on a fire alarm control or annunciator panel.

NOTE: This is an unformatted excerpt from our online fire protection training library.