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. They can also be speaker strobes which sound an alarm, followed by a voice evacuation message which warns people inside the building not to use the elevators. 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 .
Fire detectors are designed to detect one or more of the three characteristics of fire-smoke, heat and flame. Besides it every fire detection system must include manual call points (break glass), so that in the event of fire can be of immediate help. During a fire importance of activation of the occupants through alarm or bell is of at most vital and this can performed through alarm system.