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5.2 LOCAL LOOP DIAGNOSTICS
The NetLink-E1 offers local loop diagnostics. Local loop is useful when
isolating installation or performance problems. The Model 2707RC local
loop is initiated via the front panel toggle switch labeled LLB.
Operating local loopback (LLB)
The local loopback (LLB) test checks the operation of the local NetLink-
E1, and is performed separately on each unit. Any data sent to the local
NetLink-E1 in this test mode will be echoed (returned) to the user device
(for example, characters typed on the keyboard of a terminal will appear
on the terminal screen)
To perform an LL test, do the following:
1. Activate LL. This can be done in any of the following ways:
—
Enter
Local Loop
from the NMS Diagnostics/Statistics menu
and select the
Local Loop
option from the drop-down menus
—
Activate the
LL
signal on the DTE. If you are not sure which
lead is the
LL
signal, refer to Appendix D on page 29
—
Toggle the front panel switch to the
Local
position
2. Verify that the data terminal equipment is operating properly and can
be used for a test.
3. Perform a BER test (bit error rate). If the BER test equipment indi-
cates no faults, but the data terminal indicates a fault, follow the
manufacturer’s checkout procedures for the data tereminal. Also,
check the interface cable between the terminal and the NetLink-E1.
