5.0 OPERAT I O N
Once you have configured each Model 1140 properly and connect-
ed the fiber and RS-232 cables, you are ready to operate the units
This section describes the LED status monitors, the V.52 and V.54
diagnostics and the power up process.
5.2 TEST MODES
The Model 1140 offers two V.54 test modes to evaluate the condi-
tion of the modems and the communication link. These tests can be
activated physically from the front panel, or via the interface. Note:
V.54 test modes on the Model 1140 are available for point-to-point
applications only.
5.2.1 LOCAL ANALOG LOOPBACK (LAL)
The Local Analog Loopback (LAL) test checks the operation of the
local Model 1140, and is performed separately on each unit. Any data
sent to the local Model 1140 in this test mode will be echoed (returned)
back to the user device. For example, characters typed on the key-
board of a terminal will appear on the terminal screen. To perform a
LAL test, follow these steps:
A.
Activate LAL. This may be done in one of two ways: First, by
moving the front panel toggle switch DOWN to “LAL”. Second, by rais-
ing pin 18 on the interface. (Note: Make sure DIP switch SW2-8 is
OFF). Once LAL is activated, the Model 1140 transmit output is con-
nected to its own receiver. The “test” LED should be lit.
B.
Verify that the data terminal equipment is operating properly
and can be used for a test. If a fault is indicated, call a technician or
replace the unit.
C. Perform a BER (bit error rate) test on each unit. If the BER
test equipment indicates no faults, but the data terminal indicates a
fault, follow the manufacturer’s checkout procedures for the data termi-
nal. Also, check the interface cable between the terminal and the
Model 1140.
5.2.2 REMOTE DIGITAL LOOPBACK (RDL)
The Remote Digital Loopback (RDL) test checks the performance
of both the local and remote Model 1140s, and the communication link
between them. Any characters sent to the remote Model 1140 in this
test mode will be returned back to the originating device. 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 1140 and looped back. To perform an RDL test, follow these
steps:
A. Activate RDL. This may be done in two ways: first, by moving
the front panel toggle switch UP to “RDL”. Second, by raising pin 21
on the interface. (Note: Make sure SW2-8 is OFF).
B. Perform a BER (bit error rate) test on the system.
C. If the BER test equipment indicates a fault, and the Local
Analog Loopback test was successful for both Model 1140s, you may
have a problem with the twisted pair line between the modems. You
should then check the fiber line for proper connections and continuity.
5.2.3 USING THE V.52 BER TEST INDEPENDENTLY
The V.52 BER test can be used independently of the V.54 loop-
back tests. This requires two operators: one to initiate and monitor
the test at the local Model 1140, and one at the remote Model 1140.
To use the V.52 BER test by itself, both operators should simultane-
ously follow these steps:
Leds
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