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7.3
Test Cables
If you are using the MultiMux internal DSU, there are two test cables provided which can be used to help checkout your
system (refer to Figure 7-1). The MultiMux Test cable is a special back-to-back composite link test cable that can
connect your two MultiMuxes locally before installing them using a phone line. This cable will allow you to verify
operation of all aspects of the MultiMux prior to actual installation. The second test cable is the Composite Link
Loopback cable. Its function is to loopback the DSU signals to itself (loopback) so that you can check the function of the
MultiMux while installed without having to use the composite link phone line. 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-Techs Technical Support department for
assistance, refer to Chapter 8.
Test Cable
Internal Composite
Connector
MultiMux
MultiMux
Using the Test Cable
Using the Composite Link Loopback Cable
MultiMux
MultiMux
Internal Composite
Connector
Composite Link
Loopback Cable
Note: Used locally before installation to verify operation of
entire system except compolsite link.
Note: Initiate Downline Load must be off for loopback testing.
Figure 7-1. Off Line Test Modes
7.4
Troubleshooting Guide
The following guides are set up as a series of possible conditions, causes and suggested fixes or steps in finding the
failing unit. Because of the different manufacturers equipment involved in typical multiplexer networks, you may
encounter finger pointing as to who is at fault. Who is at fault is not as important as getting you back on line as soon
as possible. The intent of the following guides are to indicate the most probable cause of specific error conditions, but,
since similar conditions may account for a number of different failures, the following guides are just that: a guide to
troubleshooting.
The parts of your mux network are:
Data Channel
Channel devices (printers, terminals, pcs, etc.)
Channel Communications (RS232 cabling, asynchronous modems, etc.)
Voice/Fax Channel
Telephones and fax machines
Station side of PBX
E&M trunk
Control units
Composite Link
Digital composite link communications line with internal or external DSU
External Synchronous link modems
Composite link communications line (4-wire non-loaded metallic wire)
Once you have found the probable cause of your problem, refer to the specific manual chapter for additional help, or
contact Multi-Tech Technical Support (refer to Chapter 8).
Table 7-1. Data Troubleshooting Guide
Condition Possible Cause Corrective Action
Supervisory Console 1. Communications software 1. Install communications software on