A fire alarm system has a number of devices working together to detect
and warn people through visual and audio appliances when smoke, fire,
carbon monoxide or other emergencies are present. These alarms may be
activated automatically from smoke detectors, and heat detectors or may
also be activated via manual fire alarm activation devices such as
manual call points or pull stations. Alarms can be either motorized
bells or wall mountable sounders or horns.
Fire alarm sounders can be set to certain frequencies and different tones
including low, medium and high, depending on the country and manufacturer of
the device.