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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 nine LED indicators that monitor
the status of communication. Figure 12 shows the location of the LEDs.
TXD
When the unit sends a one, the TXD LED is
green. When it sends a zero, the TXD LED
is orange. 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 green. When it receives a zero, the RXD
LED is orange. Moreover, the RXD LED is
active only in active DS0 channels. In inac-
tive channels, the RXD LED is off.
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.
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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/CSU loopback, the TST LED will stay
on. These are the test modes:
• V.54/CSU 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.
5.2 LOOP (V.54 & TELCO) DIAGNOSTICS
The NetLink-T1™ offers three V.54 loop diagnostics and is compat-
ible with two Telco loop diagnostics. Use these diagnostics to test the
CSU/DSU and any communication links. These tests can be activated
via the software control port (See Section 3.2.3 System Diagnostics),
via signals on the serial port interface or the front panel switch.
5.2.1 Operating Local Loopback (LL)
The Local Loopback (LL) test checks the operation of the local
NetLink-T1™, and is performed separately on each unit. Any data sent
Figure 12. Model 2710RC front panel, showing LED indicators.
Model 2710RC
