Testing the DS1 span

Last Updated : Apr 30, 2024 |

Procedure

  1. Enter busyout board location to busy out the DS1 media module.
  2. At the SAT terminal, enter change ds1 location and verify that the near-end csu type is set to integrated.
  3. On page 2 of the DS1 administration screen, confirm that the TX LBO field is 0 (dB). If not, record the current value and change it to 0 dB for testing.
  4. Press Enter to save the changes.
  5. Enter test ds1-loop location cpe-loopback-jack.

    This command turns on simplex power to the loopback jack and waits about 20 seconds for any active DS1 facility alarms to clear. A “PASS” or “FAIL” displays on the terminal. This is the first of the two results. A “FAIL” indicates a fault is present in the wiring between the ICSU and the loopback jack. The loopback jack may also be faulty. A “PASS” only indicates that the loopback jack looped successfully, and not that the test data contains no errors. If a “PASS” is obtained, continue with the following steps.

    Note:

    The loss of signal (LOS) alarm (demand test #138) is not processed during this test while the 3-in-24 pattern is active.

  6. Enter clear meas ds1 loop location to clear the bit error count.
  7. Enter clear meas ds1 log location to clear the performance measurement counts.
  8. Enter clear meas ds1 esf location to clear the ESF error count.
  9. Enter list meas ds1 sum location to display the bit error count.
  10. Repeat Steps 5 through 8 as needed to observe bit error rate characteristics. Also, wait 1 to 10 minutes between Steps 5 through 7. One minute without errors translates to greater than a 1 in 10 to the eighth error rate. Ten minutes without errors translates to greater than a 1-in-109 error rate.
  11. If the test runs for 1 minute with an error count of 0, confirm that the 3-in-24 pattern error detector is operating properly by entering test ds1-loop location inject-single-bit-error. This causes the 3-in-24 pattern generator on the DS1 media module to inject a single-bit error into the transmit pattern. A subsequent list meas ds1 summary location command displays the bit error count:

    • If a count greater than 1 is displayed, replace the ICSU and retest.

    • If the problem continues, replace the DS1 media module.

  12. Terminate the test by entering test ds1-loop location end-loopback/span-test.

    Wait about 30 seconds for the DS1 to re-frame on the incoming signal and clear DS1 facility alarms. Loopback termination fails under the following conditions:

    1. The span is still looped somewhere. This could be at the loopback jack, at the ICSU, or somewhere in the network. This state is indicated by a fail code of 1313. If the red LED on the loopback jack is on, replace the ICSU. Re-run the test and verify that the loopback test terminates properly. If not, replace the DS1 media module and repeat the test.
    2. The DS1 cannot frame on the incoming span’s signal after the loopback jack is powered down.

      This means that there is something wrong with the receive signal into the loopback jack from the dumb block or the Smart Jack. If the service provider successfully looped and tested the span, up to the Smart Jack, this condition isolates the problem to the wiring between the loopback jack and the Smart Jack. Refer to Loopback Jack fault isolation proceduresfor information about how to proceed in this case. The test cannot be successfully terminated until a good signal is received. To properly terminate the test before a good receive signal is available, enter reset board location.

  13. Restore the TX LBO field to the original value recorded in Step 2.
  14. Release the DS1 media module using the release board location command.
  15. Leave the loopback jack connected to the DS1 span.