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CHAPTER 12: Testing and Troubleshooting
Test Purpose
The DTE & Loop test is used for the following purposes:
• Verify integrity of the DTE interface and cable.
• Provide a loopback for network tests.
Interpreting Test Results
A BERT tester must be used to interpret the test results of a DTE & Loop test.
12.3.2 L
OOP
O
NLY
(RT)
The Loop Only (RT) test allows the loop interface and a major portion of the
DTE interface for the local CSU/DSU MS DBU to be tested from the remote site
over the actual communication circuit. Figure 12-6 illustrates the loopback point
and the signal paths for this test.
Figure 12-6. Loop Only Test.
Test Purpose
The Loop Only test is used to provide a loopback for network tests.
Interpreting Test Results
The Loop Only test is used for the purpose of looping the DDS circuit back
to the telco. No test results are available from the local CSU/DSU MS DBU.
12.3.3 DTE O
NLY
The DTE Only test provides a method for testing both the DTE interface drivers
and receivers of the local CSU/DSU MS DBU plus its loop transmitter and
receiver. For this test, the loop transmit data is connected to the loop receive data
at a point close to the physical network interface. This test can be used to verify
proper operation between the local DTE and the local CSU/DSU MS DBU.
LOCAL
DSU/CSU
TELCO
DTE
Interface
NET Rx
NET Tx
DTE Rx
DTE Tx