Networking / Beginners

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Using a T-1 test set

If all the previous tests don't reveal the source of your problem, your next step is to replace your hardware and see whether that brings the circuit up. If this doesn't resolve your issue, you need to call out a hardware technician with a portable T-1 test set, possibly a Phoenix test set model 5575 or a T-Berd test set made by TTC.

Tip If you have a complex phone system, or if your business is in any way based on providing phone service, whoever is servicing your phone system should have a piece of testing hardware. Test sets look like a cross between a tool-box and a 1930s lunch box. They range in price from a few hundred dollars for a used Phoenix 5575A, to several thousand dollars for a fully fleshed out TTC T-Berd or TTC FireBerd with all the available ISDN options.

Having a test set for your dedicated circuit is very helpful, so chat with your hardware provider and see what is the best test set for your application and budget. A refurbished Phoenix 5575A might be all you will need and is well worth the $200 you might end up spending for it on eBay.

Tip If you don't want to buy your own test set, you can always have a hardware technician come out and do the work for you. Call your hardware vendor and set up an appointment as soon as possible.

With a test set, you can run the continuity tests that your carrier typically performs. This allows you to begin testing as soon as you have a problem on your circuit, without waiting for a technician to call you back. After you have a technician on the line testing, you can validate his or her findings, and provide the technician with much greater information on your circuit. You can plug the test set into your circuit between the NIU and your CSU for the greatest vantage point. By placing the test set in your circuit at this location, you bypass your entire phone system. This is a tremendous benefit because the test set acts as an insulator between your hardware and your carrier. If your test set is monitoring the signal coming in from your carrier and it shows that the carrier is sending B8ZS/ESF signaling rather than AMI/SF, there is no way the problem can be related to your multiplexer. All the hardware behind your test set is hidden by it and invisible to your carrier. The minor investment will pay off, because it will no longer be possible for your hardware vendor and your carrier to point fingers at each other. The test set is an independent piece of hardware that you can use to replace your multiplexer in the circuit, and can allow you to dial out on an individual channel if your test set has the correct options. If your problem clears when your carrier is connected to your test set rather than to your multiplexer, your hardware is at fault and your next course of action is a detailed check of your multiplexer and the network behind it.