Multi-Tech Systems MT56DSU-S - Manual (Page 21)

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Chapter 4 - Diagnostics
4.1.2 Line Loopback Test
This test enables you to test the local DTE, the local DSU, the communications link, and the remote DSU. Use
the following steps to perform the Trunk Loopback Test.
1. Set DIP switch #3 on the remote DSU to the down position.
2. Send data from the local DTE, it should be looped back to the local DTE. If you have access to a Bit Error
Rate Tester, this can be used in place of the local DTE.
Local DSU
Network
Local DTE
(or BERT Tester)
Remote DSU
(In Line Loopback Test Mode)
Figure 4-2. Line Loopback Test Diagram
4.1.3 DSU Loopback Test
This test lets you verify proper DSU operation by matching a transmitted signal to the “looped-back” receive
signal. Refer to Appendix B for cable description.
1. Obtain a DSU Loopback cable (#45640100) from Multi-Tech, or assemble one. Refer to Appendix B for
instructions on building the Loopback cable.
2. Plug the Loopback cable into the back panel Line jack.
3. Send data from your DTE, it should be “looped back” to your DTE. If you have access to a Bit Error Rate
Tester, this can be used in place of the DTE.
Loopback
Cable
DSU
being tested
DTE
Figure 4-3. DSU Loopback Test