Alarm indication signal: Difference between revisions

Revision as of 15:41, 5 April 2022

Revision as of 22:43, 15 December 2022

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{{Further|Digital Signal 1#Connectivity and alarms}}

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 [[Digital_Signal_1#Alarms|T-carrier]] system, and became a standard feature of subsequent [[plesiochronous]] and [[Synchronous circuit|synchronous]] circuit-based communication systems, and is also part of the [[asynchronousAsynchronous transferTransfer mode|ATMMode]] 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).