Multitech MT56DSU-S, User Manual

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Chapter 4 - Diagnostics
4.1 Introduction
The DSU is set to a default of Normal (non-diagnostic) mode at the factory. When diagnostics are to be run,
change the Loopback DIP switch as described in Chapter 2 of this manual.
When a failure occurs in the digital facility (Telco equipment), the network will detect the failure and send a
repetitive OOS signal sequence to your equipment. Your equipment can detect local loop failure by the
absence or distortion of the digital signal. If an OOS is received when data is expected, check the remote (far-
end) transmitting equipment. If the remote equipment is transmitting properly, contact your telephone
company. If the Telco is required to perform remote tests, the channel will be temporarily interrupted and loss
of data may occur.
The following sections describe the tests that are available for the DSU.
4.1.1 Loopback Test
This test allows you to test the local DTE and local DSU. Use the following steps to perform the Loopback
Test.
1. Set DIP switch #3 to the down position.
2. 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
(Or BERT Tester)
Local DSU
(In Loopback Test Mode)
Figure 4-1. Loopback Test Diagram