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2-WIRE SHORT-RANGE DSL LINE DRIVER (HDSL WITH V.35 OR X.21)
Remote Digital Loop with 511/511E
The Remote Digital Loop with 511/511E is shown in Figure 5-8. After RDL is
established, the remote unit’s restart timer is set to one minute. This has been
done 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 processor 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 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 start-up 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
