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5.2.2 Remote Digital Loopback (RL)
The Remote Loopback (RL) test checks the performance of the
link between the DTE device and the DCE as well as the link between
the local and remote DCE devices. Any characters sent from the DTE
in this test mode will be sent to the local DCE, which will send the data
to the remote DCE. The remote DCE should return the data back
through the entire communication link and finally, to the DTE. To per-
form a RL test, follow these steps:
A. Activate RL from the DTE device. This may be done either by
raising pin N on the RS-530 interface (if the RS-530 device is
DTE), or by activating Local Loopback from the HSSI interface (if
the HSSI device is the DTE). The “test” LED should be lit.
B. Perform a BER (bit error rate) test from the DTE.
C. If the BER test equipment indicates a fault, and the Local
Loopback test was successful, you may have a problem with the
cable between the DCE devices.
NOTE:
The Model 2042 simply converts and passes the data
through the communication link. The DCEs must be configured
to perform to the appropriate loopback diagnostic.
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5.2.1 Local Loopback (LL)
The Local Loopback (LL) test checks the performance of the link
between the DTE device and the DCE. Any data sent to the Model
2042 from the DTE in this test mode will be sent to the local DCE and
will then be echoed (returned) back to the DTE (the Model 2042 simply
converts and passes the data to the the local DCE, which must per-
form the loopback). To perform a LL test, follow these steps:
A.
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.
B.
Activate LL from the DTE device. This may be done either by
raising pin L (if the RS-530 device is DTE), or by activating Local
Loopback from the HSSI Interface (if the HSSI device is the DTE).
The “test” LED should be lit.
C. Perform a BER (bit error rate) test from the DTE. If the test
indicates no fault, deactivate LL and proceed as normal.
Figure 10. Local Loopback and Remote Loopback Modes
DCE
DCE
DTE
Model 2040MC-MT
RL
LL
