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LOS The Loss of Sync LED lights when the unit
loses synchronization with the incoming sig-
nal. This may happen when there is a fram-
ing mismatch or a loss of signal. In
unframed mode, the LOS LED monitors the
status of the transmit clock.
ALM The alarm LED indicates the presence of a
Blue or Yellow Alarm, or Out of Frame con-
dition. The ALM LED will blink on every half-
second. Alarms may occur due to:
•
Loss of Synchronization
• Loss of Frame
• AIS (Blue Alarm)
• RAI (Yellow Alarm)
ERR The error LED indicates various error condi-
tions, including framing bit errors, excessive
zeros, controlled slips, severe errors, or bit
errors (when sending V.52 test patterns).
When sending a test pattern, the LED will
remain lit if the unit does not receive the
identical pattern. When it receives the cor-
rect pattern, the LED will turn off. If error
insertion is on, the LED will blink once a
second if everything is operating properly.
TST The test indicator LED blinks with a specific
pattern depending on the type of test mode.
When the unit is in local analog loop, the
LED will blink on briefly. When the unit is in
remote loop, the TST LED will blink off
briefly. When the unit is sending a test pat-
tern or is putting the remote unit into V.54
loopback, the TST LED will stay on. These
are the test modes:
• V.54 Loopback & V.52 Patterns
• D4 Line Loop (CO initiated)
• ESF Line Loop (CO Initiated)
• ESF Payload Loop (CO Initiated)
PWR The power indicator LED will remain lit while
the unit is powered. It turns off when the
unit is not powered.
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5.0 OPERATION
Once the NetLink-T1™ is installed and configured properly it is
ready to place into operation. This section describes the function of
the LED indicators, and the use of the loopback and pattern test
modes.
5.1 LED DESCRIPTIONS
The NetLink-T1™ is equipped with seven LED indicators that moni-
tor the status of communication. Figure 4 (below) shows the location
of the LEDs on the NetLink-T1™ Series front panel.
TXD When the unit sends a one, the TXD LED is
turned on. When it sends a zero, the TXD
LED is turned off. Moreover, the TXD LED
is active only in active DS0 channels. In
inactive channels, the TXD LED is off.
RXD When the unit receives a one, the RXD LED
is turned on. When it receives a zero, the
RXD LED is turned off. Moreover, the RXD
LED is active only in active DS0 channels.
In inactive channels, the RXD LED is off.
RXD
LOS
ALM
ERR
T/L
PWR
TXD
Model 2711
Figure 4. Top of NetLink-T1™, Showing LED Indicators