A data link is a means of
connecting one location to another for the purpose of transmitting and receiving digital information (
data communication
Data communication, including data transmission and data reception, is the transfer of data, transmitted and received over a point-to-point or point-to-multipoint communication channel. Examples of such channels are copper wires, optic ...
). It can also refer to a set of electronics assemblies, consisting of a transmitter and a receiver (two pieces of
data terminal equipment) and the interconnecting data
telecommunication circuit. These are governed by a
link protocol enabling digital data to be transferred from a data source to a
data sink.
Types
There are at least three types of basic data-link configurations that can be conceived of and used:
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Simplex communications, most commonly meaning all communications in one direction only.
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Half-duplex communications, meaning communications in both directions, but not both ways simultaneously.
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Duplex communications, communications in both directions simultaneously.
Aviation
In civil
aviation
Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' include fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air aircraft such as h ...
, a data-link system (known as
Controller Pilot Data Link Communications) is used to send information between aircraft and
air traffic control
Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled air ...
lers for example when an aircraft is too far from the ATC to make voice radio communication and
radar
Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...
observations possible. Such systems are used for aircraft crossing the
Atlantic,
Pacific and
Indian oceans. One such system, used by
Nav Canada and
NATS 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's
flight 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.
In
unmanned aircraft, land vehicles, boats, and spacecraft, a two-way (
full-duplex or
half-duplex) data-link is used to send
control signals, and to receive
telemetry.
See also
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ACARS
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NASA Deep Space Network
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Space probe
Uncrewed spacecraft or robotic spacecraft are spacecraft without people on board. Uncrewed spacecraft may have varying levels of autonomy from human input, such as remote control, or remote guidance. They may also be autonomous, in which th ...
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Tactical data link
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Terminal (telecommunication)
In the context of telecommunications, a terminal is a device which ends a telecommunications link and is the point at which a signal enters or leaves a network. Examples of terminal equipment include telephones, fax machines, computer termina ...
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Timex Datalink
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Unmanned aerial vehicle
Sources
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{{Authority control
Data transmission