Verilink NCC 2130 (880-503285-001) Product Manual - Manual (Page 52)

Diagnostics
5-10 Verilink NCC 2130 User Manual
Test Failures If the test fails consider one of these alternatives:
• Use a loopback closer to the local CSU. The telephone carrier is
able to put up loopbacks at various locations along the path of
the T1 circuit. Start far away and work your way back to the
local CSU.
• If the local CSU seems defective try using a repeater loopback.
Send a test pattern while the local CSU is in repeater loopback.
The test pattern never leaves the CSU because it is receiving
what it is sending. If this test passes the CSU is probably OK.
• If a problem is identified but not resolved by this procedure,
go on to the next section, “Troubleshooting”.
Troubleshooting When a problem exists in a T1 network application, a different
approach is suggested. In the verification procedure above the
initial test passed data through the entire T1 circuit, including both
local and far end CSUs. This was done because no trouble was
expected.
With trouble known to exist, begin by establishing what is good.
Start with a repeater loopback test in the local CSU.
Repeater Loopback The repeater loopback test takes the transmit data just as it is
about to leave the network port of the CSU, and feeds it directly
into the receive circuitry of the CSU. If the CSU is transmitting bad
data, it will now receive bad data and the problem will be located
(the CSU). If the CSU is transmitting good data but the receive
circuitry is defective, the signal received fails and the CSU declares
an alarm.
Use the “R” command on the Diagnostics Menu to initiate a
repeater loopback. A warning message appears:
Service Affecting, Are you sure ? (Y/N) Service Affecting, Are you sure ? (Y/N) Service Affecting, Are you sure ? (Y/N) Service Affecting, Are you sure ? (Y/N)
Press “y” because you are sure. During a repeater loopback test the
NET LED on the CSU should be green and the EQPT LED should be
amber. The STAT LED will usually turn red because of a transient
bit error condition which occurs when the test begins. Ignore the
STAT LED when conducting loopback tests on a CSU.
If the EQPT LED blinks amber to red during a repeater loopback,
errors are being detected in the DSX-1 data presented by the local
equipment. Verify cabling and option compatibility.
If the NET LED is not green during a repeater loopback test, contact
Verilink Technical Support for assistance.