To perform an LLB test, follow these steps:
1.
Activate LLB. This may be done in one of three ways:
- Move the front panel toggle switch to the right to
“Local”.
- Raise the LLB signal on the interface (see Appendix B).
- Set Local Loop from the VT100 screen.
Once LLB is activated, the Model 1092ARC transmitter output is
connected 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
Section 5.2.3. 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 1092ARC.
5.2.2 Remote Digital Loopback (RDL)
The Remote Digital Loopback (RDL) test checks the performance
of both the local and remote Model 1092ARCs, and the communication
link between them. Any characters sent to the remote Model 1092ARC
in this test mode will be returned back to the originating device (see
Figure 13, below). For example, characters typed on the keyboard of
the local terminal will appear on the local terminal screen after having
been passed to the remote Model 1092ARC and looped back.
To perform an RDL test, follow these steps:
32
Figure 13.
Remote Digital Loop
Local 1092ARC
Remote 1092ARC
Important! Do not send a 511 test pattern from the test
equipment when you connect external test equipment to the
1092ARC .
RDL initiated
ER
glows red to indicate the likelihood of a Bit Error
in the received signal. During the 511 or 511/E
test, ER flashes to indicate that the Test Pattern
Detector has detected a bit error.
TM
glows yellow to indicate that the Model 1092ARC
has been placed in Test Mode. The unit can be
placed in test mode by the local user or by the
remote user.
NS
(No Signal) glows red to indicate that the local
Model 1092ARC has not yet connected with the
remote Model 1092ARC.
5.2 TEST MODES
The Model 1092ARC 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 physically from the front panel, or via the interface.
5.2.1 Local Line Loopback (LLB)
The Local Line Loopback (LLB) test checks the operation of the
local Model 1092ARC, and is performed separately on each unit. Any
data sent to the local Model 1092ARC in this test mode will be echoed
(returned) back to the user device (see Figure 12, below). For
example, characters typed on the keyboard of a terminal will appear on
the terminal screen.
31
Figure 12. Local Line Loopback
LLB initiated
