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.
Dereham (/ˈdɪərəm/), also known as East Dereham, is a town and civil parish in the Breckland District of the English county of Norfolk. It is situated on the A47 road, about 15 miles (25 km) west of the city of Norwich and 25 miles (40 km) east of King's Lynn.
The civil parish has an area of 21.51 km2 (8.31 sq mi) and, in the 2001 census, had a population of 15,659 in 6,941 households; the population at the 2011 census increased to 18,609. Dereham falls within, and is the centre of administration for, Breckland District Council. The town should not be confused with the Norfolk village of West Dereham, which lies about 25 miles (40 km) away.
Since 1983, Dereham has been twinned with the town of Rüthen in North Rhine-Westphalia, Germany. It is also twinned with Caudebec-lès-Elbeuf, France. In spite of the reunification of Germany in 1990, the sign on the A47 at the entrance to Dereham from the Swaffham direction still refers to Rüthen being in West Germany; this sparks periodic comment in the local press.