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Diagnostics
Local Loopback with Self Test
The Local Loopback Test with Self-Test checks the internal circuits of the local DSU, isolated from
both the DTE and the network. The test procedure involves two functions:
•
Local Loopback Test causes the DSU loops transmit data back as receive data.
•
Self-Test causes the DSU to enable its internal Test Pattern Generator to provide the
signal for the Local Test loop and enable its Test Pattern Checker to verify the signal. The
DSU is isolated from its DTE while the Test Pattern Generator and Checker are enabled.
The TM indicator is On during the test. The TM indicator remains On as long as the test pattern is
received without errors. TM indicator blinks off when an error is detected.
Figure 4-2
076R160-000
Issue 4
TEST
PATTERN
GENERATOR
DTE
INTERFACE
TEST
PATTERN
CHECKER
Local Test with Self Test
SpectraComm 800 T3 Data Service Unit
Installation and Operation Manual
Diagnostics Overview
SC800 T3 DSU
Tx DRIVER
F
R
A
M
E
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ANALOG
RECEIVER
T
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