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Chapter 7 - Troubleshooting
7.3 Test Cables
If you are using the DataTalker internal DSU or MMH2834 modem, there are three test cables
you can use to check out your system. Two DataTalker back-to-back test cables allow you to
connect your two DataTalkers locally before installing them on either end of a phone line. There is
also a composite link loopback cable that you can use with the internal DSU to loop the
DataTalker composite link signal back to itself.
To test the internal DSU back-to-back, connect the DSUs in the two units with the RJ-45 back-to-
back cable, then configure one DSU for internal clocking and the other DSU for external clocking.
Set the speed to the same value on both units. To perform the composite link loopback test,
configure the DSU for internal clocking and use the composite link loopback cable.
To test the internal MMH2834 modem back-to-back, use the RJ-11 back-to-back cable and
configure both modems for 4-wire leased line operation. Configure one modem for originate and
the other modem for answer. Set the speed to the same value on both units and set transmit
level to -10. To test 2-wire leased line operation, substitute a regular RJ-11 cable in place of the
back-to-back cable and reconfigure the modem for 2-wire operation.
If you are using an external synchronous modem for the link communications, refer to its
documentation for testing procedures.
If you have any problems in performing these procedures, contact Multi-Tech’s Technical Support
department for assistance (see Chapter 8).
Test Cable
Internal Composite
Connector
Internal Composite
Connector
Composite Link
Loopback Cable
Note: Used locally before installation to verify operation of
entire system except composite link.
Test Cable for Internal DSU or MMH2834 Modem
Composite Link Loopback Cable with Internal DSU
DataTalker
DataTalker
DataTalker
DataTalker
Figure 7-1. Off-Line Test Modes