General DataComm SpectraComm 800 T3, Руководство по установке и эксплуатации

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Diagnostics Diagnostics Overview
4-2 SpectraComm 800 T3 Data Service Unit 076R160-000
Installation and Operation Manual Issue 4
Local Loopback Test
The Local Loopback test isolates the DSU from the network by connecting the transmit logic
circuits to the receive logic circuits. The loopback provides a path through the DSU for an externally
generated test signal. The figure below demonstrates the Local loopback data path.
Figure 4-1 Local Loopback Test Data Path
Test Procedure
1. Enter test data at the DTE.
2. Compare data entered at the DTE with data looped back and displayed by the DTE.
3. During Local Loopback:
• TM LED illuminates steady ON during the test.
• The DTE interface remains active.
• The DSU loops transmit data from the DTE back as receive data.
• Either the DTE or a bit error rate tester (BERT) connected to the DTE interface can
supply and check a test signal.
• The device supplying the test signal is responsible for error detection and reporting.
SC800 T3 DSU
Tx DRIVER
ANALOG
RECEIVER
T
3
N
E
T
W
O
R
K
F
R
A
M
E
R
DTE
INTERFACE
DTE