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Warning system

System to inform of a future danger

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A warning system is any system of biological or technical nature deployed by an individual or group to inform of a future danger. Its purpose is to enable the deployer of the warning system to prepare for the danger and act accordingly to mitigate or avoid it.

Warnings cannot be effective unless people react to them. People are more likely to ignore a system that regularly produces false warnings (the cry-wolf effect), but reducing the number of false warnings generally also increases the risk of not giving a warning when it is needed. Some warnings are non-specific: for instance, the probability of an earthquake of a certain magnitude in a certain area over the next decade. Such warnings cannot be used to guide short-term precautions such as evacuation. Opportunities to take long-term precautions, such as better building codes and disaster preparedness, may be ignored.

01Biological warning systems

There are 8,200 alarm sirens for civil protection throughout Switzerland. They are tested once a year, on the first Wednesday in February. Sound sampleⓘ
There are 8,200 alarm sirens for civil protection throughout Switzerland. They are tested once a year, on the first Wednesday in February. Sound sampleⓘ
Warning light indicating danger of laser exposure
Warning light indicating danger of laser exposure

02Man-made warning systems

Civilian warning systems

Military warning systems

Historical beacon-based systems:

Space-based missile early warning systems:

Airborne early warning systems:

Ground-based early warning radar systems:

Optical sensors:

Emergency broadcasting:

Early warning siren for earthquakes and floods
Early warning siren for earthquakes and floods
A fire alarm that warns people if a building is on fire
A fire alarm that warns people if a building is on fire
Watch videos about Warning systemExplainers and documentaries on YouTube (opens in a new tab)

Sources and credits

This article is adapted from the Wikipedia article Warning system, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.

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