Alarm indication signal: Difference between revisions

Revision as of 00:46, 13 March 2012

Revision as of 21:08, 24 August 2012

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These are [[SONET]] OC-xx level indications that indicate if the errored element is in a section, segment, line segment, or path segment of the SONET circuit.

{{Further2Further|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 [[asynchronous transfer mode|ATM]] standards.