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Maintenance Description
9-10 Issue 1 December 1997
Maintenance Signaling 9
The DDM-2000 OC-12 Multiplexer provides maintenance signaling compliant with
the SONET standard (TR-253). The DDM-2000 OC-12 Multiplexer inserts and
detects the following alarm indication signals (AISs), which notify downstream
equipment that a failure has been detected and alarmed by some upstream
equipment:
■ SONET line AIS
■ STS-1 path AIS
■ DS3 AIS.
The DDM-2000 OC-12 Multiplexer also inserts and detects the following signals,
which notify upstream equipment of a failure detected downstream:
■ Line far-end-receive failure (FERF)
■ STS-1 path yellow.
The DDM-2000 OC-12 Multiplexer also inserts and detects STS unequipped
signals. Figure 9-3 is an example of the AIS, yellow, and FERF signals generated
in response to an unprotected incoming OC-12 line failure.
Figure 9-4 shows maintenance signals used by the DDM-2000 OC-12 Multiplexer
in an STS path switched ring application. In this figure, the labels on the arrows
pointing into the DDM-2000 OC-12 Multiplexer indicate the maintenance signals
and failure conditions recognized by the DDM-2000 OC-12 Multiplexer. The labels
on the arrows pointing out of the DDM-2000 OC-12 Multiplexer indicate the
signals generated by the DDM-2000 OC-12 Multiplexer in response to the
indicated incoming signals or failure conditions. The Xs indicate points of failure,
either within the DDM-2000 OC-12 Multiplexer or in upstream equipment.
Unlabeled arrows indicate normal transmission.
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