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The Model 2720 receiving a RL can be in one of the following states:
RxPr
The Model 2720 is receiving a preparatory pattern.
Sack
The Model 2720, upon receiving a preparatory pattern,
sends an acknowledgement message.
RL
The Model 2720 is in remote loopback mode.
RxTr
The Model 2720 is receiving a terminate loopback mes-
sage.
Wt1s
The Model 2720 is waiting for a sequence of all ones and
will time out if it does not receive it.
IdleP
The Model 2720 is sending a QRSS, 511 or 2047 pattern.
Off
The Model 2720 is in local loopback.
Test Pattern Idle
(default)
Options: Idle or Sending
To send a pattern, press the ‘c’ key and press <spacebar> to send
the test pattern. The “OK” message indicates the received test pattern
is error-free. The “BE” message indicates errors in the received pat-
tern.
Idle
Indicates that Model 2720 is not sending a pattern.
Sending Indicates that 2720 is sending a pattern.
Error Insertion Off
(default)
Options: On, Off
You may inject intentional errors into the test pattern by turning
Error Insertion ON. The Error (ERR) LED will blink once per second.
Selected Pattern QRRSS (default)
Options: QRSS, 511, or 2047
Use this option to select the test pattern used to test the link.
Note: The front panel test pattern switch will initiate the test pattern
selected in this menu (default QRSS).
Network Interface (NI) STATUS
The Network interface (NI) status is shown in
the middle of the Diagnostics/Statistics screen. The brackets are
empty when the link is operating normally. In this example, various two
or three-letter messages are displayed within the brackets, illustrating
what you may see if the Model 2720 is not connected at all or is in a
loss of signal condition. Here are the eight status messages.
Excessive zeros [EXZ], i.e., lack of pulses, detected. This condition
may occur if the unit is not connected to the network, in which case the
EXZ is displayed continuously. If EXZ comes on intermittently, there
may be a frame, line code or data rate mismatch between the near and
far-end units.
Receiver Carrier Loss [RCL] occurs when 192 consecutive zeros
have been detected at the network interface. RCL clears when a pulse
is detected.
Frame Bit Error [FE] occurs when there is an error in the framing bit
sequence. This may happen due to a disconnected line, mismatched
framing formats or severe errors in the data stream. This error may
indicate a noisy line or cable condition. This error may indicate a noisy
line or cable connection if the frames appear to be set correctly.
Severe Frame Error [SE] occurs when the framing error exceeds a
certain threshold of errors. This may happen due to a disconnected
line, an extremely noisy connection, or mismatched framing.
Loss of Sync [LOS] occurs when the T1 framer in the unit cannot
synchronize itself to the received data stream. This may happen due to
a disconnected line.
Out of Frame [OOF] occurs when no valid frame structure can be
found. This may happen due to a disconnected line or mismatched
framing or mismatched framing.
Alarm Indication Signal [AIS] indicates that the remote unit or the
central office is sending a Blue Alarm, because it is not receiving a sig-
nal; the alarm is an unframed all-ones signal, mainly used to keep the
line alive and to indicate that it is not receiving any signal. This may
indicate that the local unit is receiving a good signal, but that the trans-
mit link may be broken.
c
d
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