Maintenance
4-15
3350-A2-GB20-10
June 1996
Test Commands
The test commands enable you to run loopbacks and
test patterns on the E1 NTU, and to test the front panel
LEDs. These tests can help you isolate areas of trouble if
you are having problems with your E1 NTU.
To access all Test commands from the Test branch,
press F2 to select Test from the top-level menu screen.
F1
E1 HDSL NTU
Stat
Test
Cnfig
F2
F3
Local Loopback Tests
The Local Loopback tests enable you to conduct circuit
testing and fault isolation for the digital line. The
supported local loopback tests are:
•
Line Loopback (LLB)
•
Payload Loopback (PLB)
•
DTE Loopback (DLB)
•
Repeater Loopback (RLB)
The Line Loopback command can be activated and
deactivated in response to commands received over the
network interface. The Network Interface configuration
option NET LLB controls whether the E1 NTU responds
to the commands transmitted on the network interface to
initiate LLBs (see Appendix C, Configuration Options).
Local loopback tests can be aborted (Abort Command)
at any time.
No more than two local loopbacks can be active at any
one time. An additional restriction prohibits certain
loopbacks from running at the same time. Valid loopback
combinations listed in Table 4-9 are identified by YES.
Table 4-9
Valid Loopback Combinations
LLB
PLB
DLB
RLB
LLB
N/A
NO
YES
YES
PLB
NO
N/A
YES
NO
DLB
YES
YES
N/A
NO
RLB
YES
NO
NO
N/A
