A fire alarm system warns people when smoke, fire, carbon monoxide or other fire-related emergencies are detected. 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. Fire alarm warning devices can also be set to different volume levels.
Belper is a town and civil parish in the local government district of Amber Valley in Derbyshire, England, located about 7 miles (11 km) north of Derby on the River Derwent. As well as Belper itself, the parish also includes the village of Milford and the hamlets of Bargate, Blackbrook and Makeney. As of the 2011 Census, the parish had a population of 21,823. Originally a centre for the nail-making industry since Medieval times, Belper expanded during the early Industrial Revolution to become one of the first mill towns with the establishment of several textile mills; as such, it forms part of the Derwent Valley Mills World Heritage Site.