Chapter 4. Tests and Diagnostics ASMi-31
Installation and Operation Manual
4-2 Diagnostic Tests 24-01-00 19:17
Local Analog
Loopback (LLB)
The Local Analog Loopback (LLB) test checks the performance of the local
ASMi-31, the local DTE, and the connections between them (see
Figure 4-1). Perform the test separately at the local and the remote site.
ASMi-31
Line
Interface
DTE
Transmit
Receive
Data
Clock
Clock
Data
Figure 4-1 Local Analog Loopback
➤
➤ ➤
➤ To perform the Local Analog Loopback test:
• Activate the test via the DTE interface analog loopback.
The TEST LED lights up.
The ASMi-31 modem transmit output is connected to the receiver circuits
internally at the line side. If a fault is indicated, call a technician or replace
the unit.
Set the DTE equipment in half duplex (which produces an "echo" through
the system). It is recommended that you repeat the LLB test using an
external Bit Error Rate Tester (BERT).
Perform the test at both ends. If the BERT equipment test indicates no faults,
but the data terminal indicates a fault, follow the DTE manufacturer's test
procedures . Also check the interconnecting cable interfacing between the
terminal and the ASMi-31 modem.
After completing the test (or when the fault has been corrected), deactivate
the LLB via the DTE interface and proceed to the Remote Loopback
(Communication Link) Test.
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