A civil defense siren, also known as an air-raid siren or tornado siren, is a siren used to provide an emergency population warning to the general population of approaching danger. Initially designed to warn city dwellers of air raids during World War II, they were later used to warn of nuclear attack and natural disasters, such as tornadoes. The generalized nature of sirens led to many of them being replaced with more specific warnings, such as the broadcast-based Emergency Alert System and the Cell Broadcast-based Wireless Emergency Alerts and EU-Alert mobile technologies.
A tornado warning is a public warning that is issued by weather forecasting agencies to an area in the direct path of a tornado or a thunderstorm that is capable of producing a tornado. Modern weather surveillance technology such as Doppler weather radar allow for early detection of rotation in a thunderstorm, and for subsequent warnings to be issued before a tornado actually develops. It is nevertheless still not uncommon that warnings are issued based on reported visual sighting of a tornado, funnel cloud, or wall cloud, typically from weather spotters or the public, but also law enforcement or local emergency management. In particular, a tornado can develop in a gap of radar coverage, of which there are several known in the United States.
A long-range acoustic device (LRAD), acoustic hailing device (AHD) or sound cannon is a specialized loudspeaker that produces sound at high power for communicating at a distance. It has been used as a method of crowd control, which has caused permanent hearing damage, having an extremely high decibel capacity. Other uses have included for negotiations in siege situations to deal with piracy at sea; for mass notification during natural disasters or other emergencies; and by defense forces, including several navies.
A siren is a loud noise-making device. Civil defense sirens are mounted in fixed locations and used to warn of natural disasters or attacks. Sirens are used on emergency service vehicles such as ambulances, police cars, and fire engines. There are two general types: mechanical and electronic.
A tsunami warning system (TWS) is used to detect tsunamis in advance and issue the warnings to prevent loss of life and damage to property. It is made up of two equally important components: a network of sensors to detect tsunamis and a communications infrastructure to issue timely alarms to permit evacuation of the coastal areas. There are two distinct types of tsunami warning systems: international and regional. When operating, seismic alerts are used to instigate the watches and warnings; then, data from observed sea level height are used to verify the existence of a tsunami. Other systems have been proposed to augment the warning procedures; for example, it has been suggested that the duration and frequency content of t-wave energy is indicative of an earthquake's tsunami potential.
An emergency population warning is a method where by local, regional, or national authorities can contact members of the public to warn them of an impending emergency. These warnings may be necessary for a number of reasons, including:
High-frequency direction finding, usually known by its abbreviation HF/DF or nickname huff-duff, is a type of radio direction finder (RDF) introduced in World War II. High frequency (HF) refers to a radio band that can effectively communicate over long distances; for example, between U-boats and their land-based headquarters. HF/DF was primarily used to catch enemy radios while they transmitted, although it was also used to locate friendly aircraft as a navigation aid. The basic technique remains in use as one of the fundamental disciplines of signals intelligence, although typically incorporated into a larger suite of radio systems and radars instead of being a stand-alone system.
The Standard Emergency Warning Signal (SEWS) is a warning siren used in Australia to alert the public of danger. The siren is played over radio, television or public address systems in public places to warn of bushfire, flood, cyclone, tsunami, earthquake or terrorist attack.
Federal Signal Modulators are electronic warning devices produced by Federal Signal Corporation that are used to alert the public about tornadoes, severe weather, earthquakes, fires, lahars, tsunamis, or any other disaster. They are identified mostly by their distinctive stacked "flying saucer" design. The Modulator II is sold based on the more compact chassis of the siren compared to the original Modulators.
The Whelen Engineering Company is an American corporation that designs and manufactures audio and visual warning equipment for automotive, aviation, and mass notification industries worldwide. Founded in a Deep River, Connecticut garage in 1952, Whelen has become a provider of warning lights, white illumination lighting, sirens, and controllers. Whelen products are designed, manufactured, and assembled in two facilities in Chester, Connecticut and Charlestown, New Hampshire.
SiraTone was a brand of electronic outdoor warning sirens produced by Federal Signal Corporation which began production in the early 1980s. These sirens were designed to broadcast high-intensity warning signals over a large area. SiraTone products are/were used for natural disaster notification, HAZMAT incident notification, fire call systems, and more. The SiraTone product line is no longer in production. The product line was succeeded by the Modulator and DSA electronic outdoor warning sirens.
The Mount Rainier Volcano Lahar Warning System consists of two separate components, operating in tandem: Acoustic Flow Monitors (AFM) and the All Hazard Alert Broadcast (AHAB) sirens. The AFM system was developed by the United States Geological Survey (USGS) in 1998 and is now maintained by Pierce County Emergency Management. The purpose of the warning system is to assist in the evacuation of residents in the river valleys around Mount Rainier, a volcano in Washington, in the event of a lahar. Pierce County works in partnership with the USGS, the Pacific Northwest Seismic Network (PNSN), Washington Military Department's Emergency Management Division, and South Sound 9-1-1 to monitor and operate the system.
American Signal Corporation (ASC) is an outdoor warning siren and mass notification company in the United States. ASC was founded in 1873 as Biersach and Niedermeyer (B&N). After performing poorly, the company reformed as Alerting Communicators of America (ACA) in 1968, and expanded the line of warning systems they produced. In 1992, ACA went bankrupt and was bought and reformed as the American Signal Corporation.
Wireless Emergency Alerts, is an alerting network in the United States designed to disseminate emergency alerts to mobile devices such as cell phones and pagers. Organizations are able to disseminate and coordinate emergency alerts and warning messages through WEA and other public systems by means of the Integrated Public Alert and Warning System.
The Public Warning System (PWS) is a network of civil defense sirens installed by the Singapore Civil Defence Force on over 2,000 strategic points in Singapore to warn Singaporeans of impending dangers, air raids and atomic bomb blasts. Thus far, the siren network has only been used for occasional public awareness drills, monthly noon chimes and for commemorating the island's Total Defence (February 15) and Civil Defence Days (September 15). It was also used to mark a minute's silence nationwide for the passing of former prime minister Lee Kuan Yew on the evening of 23 March 2015 and on 1 and 9 August 2020 to mark the first National Day at home.
On June 18, 2001, a small, but fatal tornado outbreak occurred across the Upper Midwest as well as Florida. The outbreak spawned a long-tracked F3 tornado that killed three people, and caused approximately US$10 million in damage. The tornado struck Siren, Wisconsin, a small village whose only siren was malfunctioning when the tornado moved through. Other less damaging tornadoes were confirmed in Florida, Iowa, Minnesota and Nebraska. Following the outbreak, areas affected by the Wisconsin tornado received financial assistance from local and federal authorities.
The Federal Signal Model 2 is an omnidirectional outdoor warning siren produced by Federal Signal Corporation.
The Local Access Alert is a warning system designed to warn radio, television stations, cable television broadcast feeds or satellite signals of impending dangers, such as tornadoes, flash flooding and other civil emergencies. The system was largely replaced by the Emergency Alert System "[1]". in the United States, although it still exists in some areas which have not yet been upgraded, and is still used from time to time in areas that have upgraded to the EAS.
Canadian Line Materials LTD. (CLM) was a Canadian siren manufacturing company which built civil defense sirens. These sirens were built and installed all over Canada to warn residents and military about incoming nuclear attacks from the USSR during the Cold War.
The Thunderbolt is a discontinued mechanical outdoor warning siren made by Federal Signal Corporation. it is a unidirectional siren with a large yellow horn.
