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Adata link is a means ofconnecting one location to another for the purpose of transmitting and receiving digital information (data communication). It can also refer to a set of electronics assemblies, consisting of a transmitter and a receiver (two pieces ofdata terminal equipment) and the interconnecting datatelecommunication circuit. These are governed by alink protocol enabling digital data to be transferred from a data source to adata sink.

There are at least three types of basic data-link configurations that can be conceived of and used:

• Simplex communications, most commonly meaning all communications in one direction only.
• Half-duplex communications, meaning communications in both directions, but not both ways simultaneously.
• Duplex communications, communications in both directions simultaneously.

In civilaviation, a data-link system (known asController Pilot Data Link Communications) is used to send information between aircraft andair traffic controllers for example when an aircraft is too far from the ATC to make voice radio communication andradar observations possible. Such systems are used for aircraft crossing theAtlantic,Pacific andIndian oceans. One such system, used byNav Canada andNATS over the North Atlantic, uses a five-digit data link sequence number confirmed between air traffic control and the pilots of the aircraft before the aircraft proceeds to cross the ocean. This system uses the aircraft'sflight management computer to send location, speed and altitude information about the aircraft to the ATC. ATC can then send messages to the aircraft regarding any necessary change of course.

Inunmanned aircraft, land vehicles, boats, and spacecraft, a two-way (full-duplex orhalf-duplex) data-link is used to sendcontrol signals, and to receivetelemetry.

• ACARS
• NASA Deep Space Network
• Space probe
• Tactical data link
• Terminal (telecommunication)
• Timex Datalink
• Unmanned aerial vehicle

•  This article incorporatespublic domain material fromFederal Standard 1037C.General Services Administration. Archived fromthe original on 2022-01-22. (in support ofMIL-STD-188).
•  This article incorporatespublic domain material fromDictionary of Military and Associated Terms.United States Department of Defense.

• Data transmission

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