Step 3: Looping the NIU

If your carrier can't loop your CSU, the next step to attempt is to drop back one step closer to the CFA point of your circuit and loop your NIU (or one step closer to Nirvana, depending on your perspective). The NIU is the last piece of hardware that your local carrier installed.

By looping the NIU, your carrier can test to the back end of the NIU where your local carrier wires into it. Your goal when methodically validating smaller sections of the circuit from the CSU back to your carrier is to find the section that is without errors or problems. Stepping back your continuity tests (for circuit failure issues) or error tests for a clean span (for quality issues) to a section without issues gives you a starting point on the circuit that you know is good. After you find that good section, you can focus your efforts on the next variable, working your way closer to your CSU, which is the hardware or the span of the circuit that's most likely the source of the issue.

If you can loop the NIU

If your carrier can loop the NIU but not the CSU, the problem lies somewhere between the back end of the NIU and the front end of the CSU. The cabling or the CSU has a break in the wiring (if your carrier is seeing a lack of continuity on the line, often referred to as an open) or is shorting out (if the carrier sees errors).

Remember If you test the CSU and it can be looped, you need to ask whomever provided the inside wiring to repair the trouble. If your local carrier pulled the inside wiring, it might be quicker to have your hardware vendor validate or rerun the cabling, instead of waiting the one to five days to have your local carrier dispatch someone to your site. To test the inside wiring, proceed to "Step 4: Looping to your T-1 jack."