Civil defense

Civil defense, civil defence (see spelling differences) or civil protection is an effort to protect the citizens of a state (generally non-combatants) from military attack. It uses the principles of emergency operations: prevention, mitigation, preparation, response, or emergency evacuation and recovery. Programs of this sort were initially discussed at least as early as the 1920s and were implemented in some countries during the 1930s as the threat of war and aerial bombardment grew. It became widespread after the threat of nuclear weapons was realized.

Since the end of the Cold War, the focus of civil defense has largely shifted from military attack to emergencies and disasters in general. The new concept is described by a number of terms, each of which has its own specific shade of meaning, such as crisis management, emergency management, emergency preparedness, contingency planning, emergency services, and civil protection.

In some countries, civil defense is seen as a key part of "total defense". For example, in Sweden, the Swedish word totalförsvar refers to the commitment of a wide range of resources of the nation to its defense - including to civil protection. Respectively, some countries (notably the Soviet Union) may have or have had military-organized civil defense units (Civil Defense Troops) as part of their armed forces or as a paramilitary service.

Civil Defense (Star Trek: Deep Space Nine)

"Civil Defense" is the 53rd episode of the television series Star Trek: Deep Space Nine, the seventh episode of the third season.

Plot

While converting the station's old ore processing unit into a deuterium refinery, Chief O'Brien and Jake Sisko accidentally trip an old Cardassian security program, which was set to put the station on lockdown in the event of a Bajoran uprising during the Occupation.

O'Brien, Jake, and Commander Sisko are trapped in the ore processing unit, an area of the station which was once run using Bajoran slave laborers. Fail safes in the system prevent the rest of the crew from accessing the area or beaming the trapped people out. When Jake crawls up the ore chute and tries to break out, the entire station locks down. An image of Gul Dukat plays on all the monitors, announcing that rioting Bajorans have escaped. Poisonous gas is released into the ore processing unit.

In Ops, Major Kira, Dr. Bashir, and Dax have been locked in to prevent presumed homicidal Bajoran workers from storming the station's control center. Odo is dismayed to find himself locked in his security office with Quark.

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.

A mechanical siren generates sound by spinning a slotted chopper wheel to interrupt a stream of air at a regular rate. Modern sirens can develop a sound level of up to 135 decibels at 100 feet (30 m). The Chrysler air raid siren, driven by a 331 cubic inch Chrysler Hemi, generates 138 dB at 100 feet.

By use of varying tones or on/off patterns of sound, different alert conditions can be signaled. Electronic sirens can transmit voice announcements in addition to alert tone signals. Siren systems may be electronically controlled and integrated into other warning systems.