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CHAPTER 5: Operation
Remote Digital Loop with 511/511E
The Remote Digital Loop with 511/511E is shown below. After RDL is established,
the remote unit’s restart timer is set to one minute. This is because when the
511/511E generator is started on the local unit, the remote framer begins seeing
unframed packets. The remote unit cannot distinguish the 511/511E pattern from
the line being disconnected, so the restart timer has been lengthened to allow the
pattern generator to function. Once the 511/511E test is started, the local unit
changes its restart timer to one minute. The pattern originates within the DSP and
is sent to the remote unit. It is then looped back to the local unit where it is
evaluated for errors. After 45 seconds, the pattern generator will timeout and stops
sending the pattern. The ER LED will begin blinking until the user turns off the
511/511E switch.
Figure 5-8. Remote loop with 511/511E.
Data Mode with 511/511E Pattern Generators
When the units enter Data Mode, you can turn on the 511/511E pattern
generators on both ends of the link. Once a 511/511E pattern is selected on one
end of the link, the pattern generator will begin transmitting unframed 511/511E
through the line to the remote end. A possible problem with this test can occur
due to the restart procedure. Once the local 511/511E is turned on, the remote
unit begins receiving an unframed 511 pattern. If the remote unit does not turn on
the 511/511E pattern generator within four seconds, the remote unit will restart
and enter the startup mode. Note that once the 511/511E pattern generator is
started, the restart timer is changed to one minute (only on the unit which has the
pattern enabled). If both units enable the 511/511E pattern within four seconds of
each other, both units will be transmitting and receiving the 511/511E pattern.
Both framers are now receiving unframed data and will restart after one minute.
The 511/511E pattern generators will timeout after 45 seconds, re-enabling the
normal data path. The ER LED will begin flashing until the user terminates the
test.
Framer
Processor
Processor
Framer
Pattern
Gen./Det.
Pattern
Gen./Det.
Loop
Control
Loop
Control
Line
X
X
X
X
