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.
Chesterfield is a large market town and borough in Derbyshire, England, 24 miles (39 km) north of Derby and 11 miles (18 km) south of Sheffield at the confluence of the River Rother and River Hipper. Including Whittington, Brimington and Staveley, it had a population of 103,801 in 2012, making it Derbyshire's second largest town. It has been traced to a soon-abandoned Roman fort of the 1st century AD. The name of the later Anglo-Saxon village comes from the Old English ceaster (Roman fort) and feld (pasture). Its sizeable street market is held three days a week. The town sits on a coalfield, but little visual evidence of mining remains. Its great landmark is the Church of St Mary and All Saints with a crooked spire.