civil defense siren

A civil defense siren (also colloquially referred to as an air-raid siren or tornado siren) is a siren used to provide emergency population warning of approaching danger and sometimes to indicate when the danger has passed. Some (that are mostly located in small towns) are also used to call the volunteer fire department to go fight a fire. Initially designed to warn of air raids in World War II, they were adapted to warn of nuclear attack and of natural destructive weather patterns such as tornadoes. The generalized nature of the siren led to many of them being replaced with more specialized warnings, such as the Emergency Alert System.