Validating the Circuit You Are Testing

Incredible, but true! People have tested for hours on a circuit, with conflicting information coming from both the hardware vendor and the carrier, only to eventually find out each test performed was on a different circuit.

If your carrier sees the circuit up and you see it down, you may not be looking at the same circuit. If your carrier takes down the circuit, but you still see it running and passing calls, you definitely aren’t looking at the same circuit. Having multiple carriers with several DS-1s per carrier might be great for your least-cost routing, but all those DS-1s can add a degree of confusion when you try to troubleshoot a single circuit.

Identifying a circuit is sometimes tough because you can make mistakes anywhere from the CFA point to the point the circuit enters your hardware. Confirm the circuit IDs assigned by both your long-distance carrier and the local loop provider. Then perform the following steps:

Unplug your hardware from the T-1 jack or reboot your CSU.

Your carrier should see the circuit drop, bounce, or reset. If the carrier sees nothing happen on its end, the carrier needs to begin looking at the other circuits you have on its network. Perform the same test until everyone is sure you’re dealing with the same circuit.
Follow the cabling from your multiplexer to the T-1 jack and all the way to the NIU if you can.

If nothing else, the circuit ID of the span should be written on the T-1 jack in your phone room. Validate that the circuit ID matches what you have on file, and then proceed to the NIU for more investigation.
Check the NIU to see whether you are connected to the wrong jack.

If the circuit you are working on was active and passing traffic at one time, this is probably not the issue, but if this circuit was recently installed, you may have discovered your problem.
Check the circuit IDs listed on the NIU.

The NIU should list at least the local loop provider’s circuit ID. These numbers should match the circuit ID listed on your T-1 jack in your phone room.
Check the NIUs for changes when they are looped or sent into failure.

NIUs have lights on them that identify the disposition of the circuit they provide. A loopback light (LBK) is illuminated when your carrier is looping the NIU, and red lights are displayed when your carrier disables your circuit. You might need to check all of your NIUs before you find the one that reflects the work your carrier is doing on it, but this is the most foolproof method of identifying your circuit.

Remember If your carrier performs all these tests and none of your circuits respond accordingly, the circuit you are working on either doesn’t belong to that carrier, or is somehow absent from the carrier’s visible inventory.