Chapter 5. Testing61200051L1-1D ISU 2x64 Dual Port ISDN Service Unit User Manual 25Loopback RemoteThis test causes the ISU 2x64 to issue a V.54 inband loopbackcommand to a far-end unit. External test equipment must beused to generate/check test patterns. To use this feature, bothunits must be configured for Clear Channel operation and the far-end unit must be able to respond to V.54 loopback commands.See Setting Protocol Options on page 55 to configure the unit forClear Channel operation. Press Cancel to end the test.Test RemoteThis test causes the ISU 2x64 to issue a V.54 inband loopback com-mand to a far-end unit and BERT test the link using a built-in patterngenerator/checker. This allows a circuit to be tested without anyextra test equipment. To use this feature, both units must be config-ured for Clear Channel operation and the far-end unit must be ableto respond to V.54 loopback commands. See the section Setting Pro-tocol Options to configure the unit for Clear Channel operation. Thebuilt-in 2047 pattern generator/checker displays the number ofbytes transmitted on the top line and the number of errored bytesreceived on the lower line of the front panel display. Pressing 0 willclear the counts. Pressing the Cancel key ends the test. Pressing thedown arrow will loop down the remote unit, allowing a test to aloopback plug. Pressing 2 will insert errors.Loopback DisableThe following options are available in Loopback Disable.No Rem Lpbks: The ISU 2x64 ignores all V.54 and DDS loopbackcommands.DDS Accepted: The ISU 2x64 responds to DDS latching loopbackcommands. This option only takes effect if the unit is in LeasedLine mode.V.54 Accepted: The ISU responds to V.54 loopback commands.DDS+V54 Accept: The ISU 2x64 responds to both DDS latchingloopback commands (Leased Line mode only) and V.54 loopbackcommands.
