A recognition signal is a

signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing' ...

whereby a person, a

ship A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished ...

, an

airplane An airplane or aeroplane (informally plane) is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, propeller, or rocket engine. Airplanes come in a variety of sizes, shapes, and wing configurations. The broad ...

or something else is recognized. They can be used during war or can be used to help the police recognize each other during

undercover To go "undercover" (that is, to go on an undercover operation) is to avoid detection by the object of one's observation, and especially to disguise one's own identity (or use an assumed identity) for the purposes of gaining the trust of an ind ...

operation Operation or Operations may refer to: Arts, entertainment and media * ''Operation'' (game), a battery-operated board game that challenges dexterity * Operation (music), a term used in musical set theory * ''Operations'' (magazine), Multi-Man ...

s. It can also be used in

biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary ...

to signal that a

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and b ...

chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., w ...

is to be bound to another molecule.

War

These signals are often used to recognize friends and enemies in a war. For

military A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare. It is typically authorized and maintained by a sovereign state, with its members identifiable by their distinct ...

use these signals often use colored lights or the International marine signal flags

Police

Other uses of the signal include the police who sometimes use a recognition signal so that officers in

uniform A uniform is a variety of clothing worn by members of an organization while participating in that organization's activity. Modern uniforms are most often worn by armed forces and paramilitary organizations such as police, emergency services, ...

can recognize officers in normal clothing (undercover). The

NYPD The New York City Police Department (NYPD), officially the City of New York Police Department, established on May 23, 1845, is the primary municipal law enforcement agency within the City of New York, the largest and one of the oldest in ...

often use

headband A headband is a clothing accessory worn in the hair or around the forehead, usually to hold hair away from the face or eyes. Headbands generally consist of a loop of elastic material or a horseshoe-shaped piece of flexible plastic or metal. T ...

wristbands Wristbands are encircling strips worn on the wrist or lower forearm. The term can be used to refer to a bracelet-like band, similar to that of a wristwatch, to the cuff or other part of a sleeve that covers the wrist, or decorative or function ...

or colored

clothing Clothing (also known as clothes, apparel, and attire) are items worn on the body. Typically, clothing is made of fabrics or textiles, but over time it has included garments made from animal skin and other thin sheets of materials and natura ...

as recognition signals which are known as the "

color of the day According to ancient customs in Thailand, there is an astrological rule (which has influence from Hindu mythology) that assigns a color to each day of the week based on the color of the God who protects the day or Navagraha. For example, the God o ...

Biology

A recognition signal is also a

signal used in

to signal the end of a section of DNA or RNA during

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

duplication Duplication, duplicate, and duplicator may refer to: Biology and genetics * Gene duplication, a process which can result in free mutation * Chromosomal duplication, which can cause Bloom and Rett syndrome * Polyploidy, a phenomenon also known ...

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery ...

Notes

External links

Signalman manual
Communication Biological techniques and tools Military communications

References

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War

Police

Biology

See also

Notes

External links

References