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September 1999 P/N 880-503284-001-A1 - page 57 / 65





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Test Failures


Figure 5-4

Sending and Receiving Pattern

Test pattern sent

Local NCC 2020 Sends pattern Checks pattern

Test pattern received

Far CSU (in Line Loop)

If the QRSS pattern is received with no errors, the Test Error Counter will not increment.

If the Test Error Counter does increment, one of the following applies:

The far end CSU never went into a loopback and therefore the test pattern being transmitted is not being received at all. This would cause the Test Error Counter to increment at a rapid and steady rate.

The far end CSU did go into a loopback, but the pattern received at the local NCC 2020 does not match the pattern transmitted. In this case the Test Error Counter might increment in uneven amounts at virtually any rate.

If the test passes, consider doing the same test with a different pattern. Some patterns will fail on a T1 which passes other test patterns. See Table 5-2 for details on the various patterns.

If the test fails consider one of these alternatives:

Use a loopback closer to the local CSU. The telephone carrier may be 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 it appears that the local CSU is 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”.

Verilink NCC 2020 User Manual


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