Multi-Tech Systems MT56DSU-S - Manual (Page 22)

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Chapter 4 - Diagnostics
4.1.4 DSU Back-to-Back Test
This test lets you connect two DSUs with a back-to-back cable to verify proper DSU operation. Using a DSU
that is known to be operational, you can test a second DSU that is suspect.
1. Obtain a DSU Back-to-Back cable (#45050000) from Multi-Tech, or assemble one. Refer to Appendix B
for instructions on building the Back-to-Back cable.
2. Plug the cable into each DSU’s Line jack.
3. On the “good” DSU, set DIP switch #3 to the down position.
4. Set one DSU to internal clocking and the other DSU to DDS clocking.
5. 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.
DTE “Suspect”
DSU
Back-to-Back
Cable
“Good” DSU in
Loopback Mode
Figure 4-4. DSU Back-to-Back Test Diagram