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signal level, the intermediate element receiving an errored signal replaces the errored channel data with a signal consisting of a valid DS3 frame with the overhead bits (the M-subframe alignment bits, M-frame alignment bits, and P bits) with the payload set to a 1010... sequence, the C bits all set
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to alert the receiving end of the circuit that a segment 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. The AIS replaces the failed data, allowing the higher order system in the concatenation to maintain its
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because of the data and framing pattern) is a signal transmitted by an intermediate element of a multi-node transport circuit that is part of a concatenated
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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
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transmission framing integrity. Downstream intermediate elements of the transport circuit propagate the AIS onwards to the destination element.
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OC-xx level indications that indicate if the errored element is in a section, segment, line segment, or path segment of the SONET circuit.
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to zero, and the X bits set to one. This way, the integrity of the DS3 frame is maintained even though the underlying data was compromised.
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There are a number of types of AIS signals, which signal failure of different logical or physical segments of the system, including:
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There are various AIS formats based on the signaling level of the errored circuit. When an element of T1 or (
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for long-distance data links has increased, the need for a similar end-to-end
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circuit-based communication systems, and is also part of the
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system, and became a standard feature of subsequent
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