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* '''Alarm indication signal line''' (AIS-L)
* '''Alarm indication signal line''' (AIS-L)


Middle 20th century analog [[carrier system]]s had Carrier Group Alarms by which a failure was alerted to [[telephone exchange]] equipment, imposing an automated make-busy condition so the trunks carried by the failed system would not be used. The improved AIS originated with the [[T-carrier]] system, and became a standard feature of subsequent [[plesiochronous]] and [[synchronous]] circuit-based communication systems, and is also part of the [[asynchronous transfer mode|ATM]] standards.
Middle 20th century analog [[carrier system]]s had Carrier Group Alarms by which the failure of a [[pilot signal]] was alerted to [[telephone exchange]] equipment, imposing an automated make-busy condition so the trunks carried by the failed system would not be used. The improved AIS originated with the [[T-carrier]] system, and became a standard feature of subsequent [[plesiochronous]] and [[synchronous]] circuit-based communication systems, and is also part of the [[asynchronous transfer mode|ATM]] standards.
As the use of [[Ethernet]] for long-distance data links has increased, the need for a similar end-to-end [[OA&M]] function has led to the development of a similar Ethernet alarm indication signal ([[EthAIS]]).
As the use of [[Ethernet]] for long-distance data links has increased, the need for a similar end-to-end [[OA&M]] function has led to the development of a similar Ethernet alarm indication signal ([[EthAIS]]).



Revision as of 03:51, 2 July 2008

Alarm indication signal (AIS) is a signal transmitted by a system that is part of a concatenated telecommunications system to let the receiver know that some remote part of the end-to-end link has failed at a logical or physical level, even if the system it is directly connected to is still working. Other systems attached to a system transmitting AIS then relay the AIS indication onwards to other systems.

There are a number of types of AIS signals, which signal failure of different logical or physical segments of the system, including:

  • Alarm indication signal path (AIS-P)
  • Alarm indication signal line (AIS-L)

Middle 20th century analog carrier systems had Carrier Group Alarms by which the failure of a pilot signal was alerted to telephone exchange equipment, imposing an automated make-busy condition so the trunks carried by the failed system would not be used. The improved AIS originated with the T-carrier system, and became a standard feature of subsequent plesiochronous and synchronous circuit-based communication systems, and is also part of the ATM standards. As the use of Ethernet for long-distance data links has increased, the need for a similar end-to-end OA&M function has led to the development of a similar Ethernet alarm indication signal (EthAIS).


See also

  • concatenation (telecommunications)