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'''Alarm indication signal''' ('''AIS''') is a signal transmitted by a system that is part of a [[telecommunications]] link to let the receiver know that the link is logically, but not physically, dead.
'''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.


There are a number of types of AIS signals, which signal failure of different logical or physical segments of the system, including:
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 path''' (AIS-P)
* '''Alarm indication signal line''' (AIS-L)
* '''Alarm indication signal line''' (AIS-L)

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 [[operations and management|OAM]] function has led to the development of a similar [[Ethernet alarm indication signal]] ([[EthAIS]]).


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Revision as of 13:55, 25 October 2005

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.

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)

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 OAM function has led to the development of a similar Ethernet alarm indication signal (EthAIS).