This test is destructive.
For documentation purposes, the term DS1 applies to the DS1 Interface media modules.
The Far CSU Loopback (R-LLB) test causes a loopback at the far-end CSU, and tests all circuitry and facilities from the local DS1 board to the far-end CSU.
The test is highly destructive and can only be initiated by entering the command test ds1-loop location far-csu-loopback-test-begin.
Enter busyout board to busy out all trunks or ports on the DS1 Interface media module before running the CPE Loopback Jack test.
Use busyout board to busy out all trunks or ports on the DS1 Interface media module before running the Far CSU Loopback test.
If the DS1 is administered for ami-zcs line coding and the far-end CSU is not a 120A CSU module or a 401A T1 sync splitter, density protection on the CSU must be disabled during the test due to the large number of zero’s in the 3-in-24 test pattern.
The Far CSU Loopback test has the DS1 Interface media module transmit a loopback activation code to the remote CSU, waits up to 15 seconds for return of the code to verify the loopback has been established, transmits a framed 3-in-24 test pattern, begins counting bit errors in the received test pattern, and returns a PASS result. If the loopback is not established within the 15 seconds, the test fails.
The status of the Far CSU Loopback test appears in the error log as Error Type 3901. Several aux values give information on the status of the test.
Use list measurements ds1 summary to show the length of time the test has been running (Test Duration field) and number of bit errors detected (Loopback/Span Test Bit-Error Count field). If the test pattern is passed through the loopback cleanly, the number of bit errors should be very low. The command also shows the type of loopback/span test executing (Test field), the type of pattern generated for the loopback/span test (Pattern field), and whether the pattern (3-in-24 Pattern) is synchronized (Synchronized field).
Use test ds1-loop location end-loopback/span-test to end the test.
Use release board location to restore each trunk or port on the DS1 Interface board to the in-service state.
