<P> 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 . Most fire alarm systems in Europe sound like a siren with alternating frequencies . Fire alarm electronic devices are known as horns in the United States and Canada, and can be either continuous or set to different codes such as Code 3 . Fire alarm warning devices can also be set to different volume levels . Fire Alarm systems in the United Kingdom are tested at a weekly basis in compliance with the BS - fire 2013 regulations . </P> <P> After the fire protection goals are established--usually by referencing the minimum levels of protection mandated by the appropriate model building code, insurance agencies, and other authorities--the fire alarm designer undertakes to detail specific components, arrangements, and interfaces necessary to accomplish these goals . Equipment specifically manufactured for these purposes is selected and standardized installation methods are anticipated during the design . In the United States, NFPA 72, The National Fire Alarm Code is an established and widely used installation standard . In Canada, the ULC is the standard for the fire system . The equivalent standard in the United Kingdom is BS 5839 Part 1 . </P>

The primary role of a fire alarm system is to