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Chapter 5. Testing
61202.029L2-1 ISU 128 User Manual 21
Loopback Remote
Loopback Remote allows the ISU 128 to issue a V.54 in-band loopback com-
mand to a far-end unit while still accepting data from the DTE connector. This
provides bit error rate testing of an entire link using an external BERT test set.
To use this feature, both units must be configured for Clear Channel operation
and the far-end unit must be able to respond to V.54 loopback commands. See
the chapter Protocol Options to configure the unit for Clear Channel operation.
Press the Cancel key to end the test.
Loopback Remote 1B and 2B are only used with the DTE set to asynchronous.
Test Remote
Test Remote allows the ISU 128 to issue a V.54 in-band loopback command to
a far-end unit and BERT the link using a built-in 2047 pattern generator/
checker. This allows for testing a circuit without any extra test equipment. To
use this feature, both units must be configured for Clear Channel operation
and the far-end unit must be able to respond to V.54 loopback commands. See
the chapter Protocol Options to configure the unit for Clear Channel operation.
The built-in 2047 pattern generator/checker displays the number of bytes
transmitted on the top line and the number of errored bytes received on the
lower line of the front panel display. Press 0 to clear the counts. By pressing
the down arrow, you can loop down the far end unit and run a head to head
2047 pattern test. Press Cancel to end the test.
Loopback Disable
The following options are available when disabling loopbacks:
No Remote Loopbacks
The ISU 128 ignores all V.54 and DDS loopback commands.
DDS Accepted
The ISU 128 responds to DSU Latching Loopback commands. This option
only takes effect if the unit is in leased line mode.
V.54 Accepted
The ISU 128 responds to V.54 loopback commands.