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CHAPTER 12: Testing and Troubleshooting
Test Purpose
A DTE with TP test verifies the internal transmit and receive circuitry of the
CSU/DSU MS DBU.
Interpreting Test Results
If the unit is functioning properly, the CSU/DSU MS DBU displays:
DTE WITH TP
TST ERR=XX
The first line of the display indicates the type of test being performed, while the
second line of the display indicates the number of errors accumulated by the test
pattern detector.
If errors occur during this test, the test error count can be reset to zero by pressing
1. To verify proper operation of this test, single bit errors can be injected into the
transmitted test pattern by pressing 2. These errors appear on the TEST ERR
display.
12.3.5 T
EST
P
ATTERN
The Test Pattern option converts the local CSU/DSU MS DBU into a BERT tester
for the purpose of testing the DDS circuit. If this test is used, the remote DSU/CSU
must be in loopback or transmitting a test pattern. Figure 12-9 illustrates the data
paths for this mode.
Figure 12-9. Test Pattern Only.
LOCAL
DSU/CSU
NET Rx
NET Tx
DTE Rx
DTE Tx
Error
Inject
Test Pattern
Generator
Error
Clear
Test Pattern
Detector
REMOTE
DSU/CSU
DTE Rx
DTE Tx
NET Rx
NET Tx
Error
Inject
Test Pattern
Generator
Error
Clear
Test Pattern
Detector
TELCO