363-206-285
Maintenance Description
9-24 Issue 3 June 2001
the set-attr-alm and rtrv-attr-alm commands in Section 11, "Commands
and Reports."
The DDM-2000 Multiplexer normally declares an alarm, service affecting (SA) or
non-service affecting (NSA), based on protection switch status. If the failed entity
(circuit pack or signal) is in the standby (not active) state the alarm is NSA. Failure
of an active entity is SA. As an option the user can provision a shelf to escalate or
bump an NSA alarm on a standby entity to SA when both the active and standby
entities fail. Refer to the set-ne command in Section 11, "Commands and
Reports."
Protection Switching 9
The DDM-2000 OC-3 Multiplexer provides equipment protection switching of all
transmission and synchronization circuit packs, and SONET standard line
protection switching for OC-3 lines. Installation of protection equipment is
optional. Protection switches are caused by automatically detected faults in the
circuit packs or OC-3 lines and by external commands from a CIT or TL1/X.25
interface. Refer to the switch-line, switch-fn, switch-ls, and switch-
sync commands in Section 11, "Commands and Reports. " The switch-line
command is not applicable to OC-3 lines configured for path switched rings or to
EC-1 interfaces. For path switched rings, path protection switching is used. Refer
to "Path Protection Switching (Path Switched Rings)" paragraphs in this section
and the switch-path-vt1 or switch-path-sts1 commands in Section 11,
"Commands and Reports."
Automatic Line Protection 9
The DDM-2000 OC-3 Multiplexer uses optional SONET 1+1 unidirectional,
nonrevertive automatic line protection switch (APS) procedures. This means that
after a cut service fiber is repaired, a location does not switch back (revert) and
select the service set as its active fiber/OLIU set. Line switching is not applicable
to OC-3 lines in a path switched ring or to EC-1 interfaces.
Status of ACTIVE LED on OLIUs 9
Figure 9-12 illustrates examples of unidirectional and nonrevertive line protection
switches. Note the squares at locations A and C. Each square represents the
transmit or receive section of an OLIU. Figure 9-12(a) and Figure 9-12(b) are
associated with the Service (S) OLIU and Figure 9-12(d) and Figure 9-12(e) with
the Protection (P) OLIU. Four optical fibers are associated with the service and
protection OLIUs that interconnect the OLIUs at locations A and C. The two fibers
connecting the service OLIUs are the service fibers and the two fibers connecting
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