
ASM-40CD Ver. 1.0 Loopback Tests 4-1
Chapter 4
Troubleshooting and
Diagnostics
This chapter discusses:
• Types of loopback tests
• Internal BERT operation
• Setting loopback, BER, and LED tests
• Viewing alarm status
• Viewing alarm buffer messages
• Troubleshooting.
All diagnostics options can be implemented from an ASCII terminal or from an
SNMP management tool. The LLB and REM loopbacks can also be initiated from
the DTE via dedicated pins of the DCE connector. These diagnostic approaches
can also be used in combination. For example, the BERT circuit test pattern can
be run on a path determined by one of the loopback connections and then
examine the alarm buffer messages for any transmission error or configuration
mismatch.
4.1 Loopback Tests
Three loopback connections apply to a transmission system consisting of an
ASM-40CD local module and an ASM-40 remote unit.
• Local analog loopback – The analog transmit signal from the local unit
transmitter is looped back to the local unit receiver. The loopback tests the
local ASM-40CD modem, the local DTE and the connections between them.
The loopback is set from the local DTE via the LLB control line (see
Figure 4-1
).
• Local digital loopback – The digital receive signal is looped back in the local
ASM-40CD towards the line. The loopback tests the local ASM-40CD, the
remote DTE and the line between them (see
Figure 4-3).
• Remote digital loopback – The digital receive signal is looped back in the
remote ASM-40 towards the line. The loopback tests the local ASM-40CD, the
remote ASM-40 and the line between them. The loopback is set from the
local ASM-40CD or from the local DTE via the RLB control line (see
Figure 4-2)
.
Komentáře k této Příručce