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5.3 TEST MODES
The Model 1082 offers two proprietary loopback test modes, plus a built-
in V.52 BER test pattern generator, to evaluate the condition of the
modems and the communication link. These tests can be activated phys-
ically from the front panel, or via the interface.
Local Line Loopback (LLB)
The Local Line Loopback (LLB) test checks the operation of the local
Model 1082, and is performed separately on each unit. Any data sent to
the local Model 1082 in this test mode will be echoed (returned) back to
the user device (see Figure 11). For example, characters typed on the
keyboard of a terminal will appear on the terminal screen.
Figure 11.
Local Line loopback
To perform an LLB test, follow these steps:
1. Activate LLB. By moving the front panel toggle switch up to “Local”.
Once LLB is activated, the Model 1082 transmitter output is con-
nected to its own receiver. Data is also looped back to the line. The
TM
LED should be lit.
2. Verify that the data terminal equipment is operating properly and
can be used for a test.
3. Perform a V.52 BER (bit error rate) test as described in “Using the
V.52 (BER) test pattern generator” on page 23. If the BER test
equipment indicates no faults, but the data terminal indicates a fault,
follow the manufacturer’s checkout procedures for the data terminal.
Also, check the interface cable between the terminal and the Model
1082.
LLB initiated
