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CHAPTER 6: Operation
6.3.3 L
OOPS AND
P
ATTERNS
The following section describes the remote loopback/BER test modes.
Remote Digital
When remote loop/511 or remote loop/511E is enabled via the front-panel switch,
the remote unit’s restart timer is set to one minute. It does this because when the
511/511E generator is initiated 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 stop sending the pattern. The ER LED will begin blinking until you
turn off the 511/511E switch.
Figure 6-3. Block diagram showing two Line Drivers
communicating over the DSL span.
6.3.4 U
SING THE
V.52 (BER) T
EST
-P
ATTERN
G
ENERATOR
To use the V.52 BER tests in conjunction with the remote digital loopback tests,
follow these instructions:
1. Locate the remote loop/511 and remote loop/511E toggle switch on the
front panel of the Line Driver and move it DOWN. This activates the remote
loop with V.52 BER and transmits a 511 test pattern into the loop. If any
errors are present, the local unit’s red ER LED will blink sporadically.
Framer
X
X
X
X
Processor
Processor
Framer
Pattern
Gen./Det.
Pattern
Gen./Det.
Loop
Control
Loop
Control
DSL
Span
