Telecom For Dummies

If your carrier asserts that a quality/continuity/protocol handshaking issue on your dedicated circuit is the result of problem within your hardware, there might be a very quick and easy way to confirm or deny that assertion. You can try this test only when you have two or more circuits with the carrier and only one of them is experiencing a problem. In this test, you unplug the cables that connect the CSUs to the NIUs and exchange them, as shown in Figure 13-7.

Figure 13-7: Crossing CSU cables.

After reconnecting the cables to match the diagram, reboot your hardware and assess the situation. If the problem ends up following the circuit from your carrier, and the multiplexer that was working fine is now failing or experiencing the issue, it’s obvious that your carrier is the source of the problem. If the outage remains within the same multiplexer or CSU that was failing on the other circuit, you have a problem with your hardware.

 Remember  This test is valid only when:

• Both circuits are configured exactly the same: Line coding/framing, out-pulse signal/start

• Both circuits are on the same carrier (both the same long-distance carrier and the same local loop provider)

• Both multiplexers are the same make and model

• Both multiplexers are configured exactly the same (trunk groups, timer settings, and all the hardware specific settings)

If any of these conditions aren’t met, the validity of this test disintegrates instantly. There are too many variations between carriers, configuration, and hardware manufacturers to say with conviction that if one set of your hardware works on a carrier, a different set should work as well.