3 pulses = Clear to Send (CTS) or Carrier
Detect (DCD) from base unit are not
asserted
4 pulses = IM1/I buffer is saturated
5 pulses = WAN receive frame(s) too large
6 pulses = WAN receive frame(s) not octet
aligned
7 pulses = WAN receive frame(s) aborted
8 pulses = Detected WAN receive frame(s) with
CRC
9 pulses = Detected LAN receive frame(s) too
large
10 pulses = Detected LAN receive frame(s) not
octet aligned
11 pulses = Detected LAN receive frame(s) with
bad CRC
LOS The Loss of Sync LED lights when the unit loses
synchronization with the incoming signal. This may
happen when there is a framing mismatch or a loss
of signal. In unframed mode, the LOS LED monitors
the status of the transmit clock.
ER
The error LED indicates various error conditions,
including framing bit errors, excessive zeros, con-
trolled 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
correct pattern, the LED will turn off. If error inser-
tion is on, the LED will blink once a second if
everything is operating properly.
TM
(Active Yellow) Solid Yellow indicates an Active
Test Mode. The unit may be placed in test mode
by the local user or by the remote user.
6.2 LOOP (V.54 & TELCO) DIAGNOSTICS
The Model 2701/I offers three V.54 loop diagnostics. Use these
diagnostics to test the NTU and any communication links. These tests
can be activated via the front panel switches.
6.2.1 Operating Local Loopback (LL)
The Local Loopback (LL) test checks the operation of the local
Model 2701/I, and is performed separately on each unit.
To perform a LL test, follow these steps:
1.
Activate LL. This may be done by selecting local loop on the
front panel switch.
2.
Perform a V.52 BER (bit error rate) test as described in
Section 6.2.4. If the BER test equipment indicates no faults,
but the data terminal indicates a fault, follow the manufactur-
er’s checkout procedures for the data terminal. Also, check
the interface cable between the terminal and the Model
2701/I.
6.2.2 Operating Remote Digital Loopback (RL)
The Remote Digital Loopback (RL) test checks the performance of
both the local and remote NetLink-E1™, as well as the communication
link between them. Any characters sent to the remote NetLink-E1™ in
this test mode will be returned back to the originating device.
Figure 12. Local Loopback for a Network Termination Application
2Mbps G.703
Network
Ethernet
Device
Model 2701/I
All Switches
set to “OFF”
Receive
Recover
Clocking
Internal
Clocking
Cable Span
2Mbps G.703
Network
G.703/G.704 NTU
Model 2701/I
Clock/
Data
Clock/
Data
Data
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