Why T1 testing necessary? Let’s take a closer look at how carriers test their T1 networks and more important, what T1 test equipment they use.
T1 or DS1, as a standard, has been around since the 1960’s and has evolved from a way to carry multiple voice conversations on one line to a way to carry digital data on a wide variety of physical interfaces. There are many physical
configurations available to fit different roles. [1] T1 circuits can be used in many different ways, but for the most part, you’ll find them distributed in a network transport system as an improved way to carry 24 voice channels in single circuit or transmit any 1.544 Mbps worth of data bandwidth. Testing and troubleshooting T1 circuits is not always an easy task, but necessary when it comes to provisioning, installation and maintenance. Some T1 testing procedures were developed by large telephone companies and others were based on industry testing standards. [2]
Why is T1 important? Anritsu explains. “Well-managed T1 help ensure cellular uptime. Good network management practices include testing prior to acceptance, as well as testing for troubleshooting purposes. In either case, good T1 troubleshooting tools are needed. Troubleshooting can often be done by monitoring an in-service signal, either through a smart jack or dedicated test equipment, while looking for errors. Once spotted, test equipment is normally needed to locate the cause of the error. However, in some cases, in-service testing is not enough, and an out-of-service Bit Error Test (BERT), is required. A BERT involves generating a bit pattern, sending it down the T1 line, looping it back at the far end of the line, and seeing how accurately the bits are returned to the test set. This technique can be used to find and repair many T1 problems.”
Frequent Causes of T1 Problems Include:
1. Signal level too high – Set too high at Smart Jack or CIU
2. Signal level too low – Loose connection or partial short caused by loss of insulation
3. Noise on the line – Loss of insulation allowing stray voltage to enter.
To help alleviate these T1 pains, Anristu relies on its Handheld BTS Master™ or the Cell Master™ with Option 51, 53, or 55. [1]
With equipment such as this, it’s typically connected to a central distribution point. Most testing is executed at this central point, usually called as cross connection point. “These cross connection platforms are applied in different hardware, the most common nowadays are called Digital System Cross-connect better known as DSX . Testing T1 circuits that are connected to DSX panels are a lot simpler and better. Circuits are tied down to these DSX panel for simple and quick access to the circuits. If your circuits are not connected in this matter, it is important to know and understand how your circuits are physically connected and you are ready to access or provide whatever the testing needs you to do with the circuit.” [2]
For T1 testing to be successful, preparation is necessary. Also, understanding of the circuit itself and knowing testing limitation is important.
“Preparation involves setting up the circuit within your network based on the circuit order before the activation date. It might involve several connections and configurations within your network. You can assume that the circuit is still down or inactive yet unless you have the confirmation from the other party that they are done provisioning on their side. Otherwise your testing alone will not conclude anything.” [2]
The typical large players in the testing and manufacturing space such as Anritsu, Agilent, Tessco, Fluke Networks and more all offer equipment to assist with this type of testing.
[1] Anritsu, T1/DS1 Backhaul Testing Field User Guide, http://www.anritsu.com/en-GB/Promotions/base-station-troubleshooting/11410-00552.pdf
[2] simpletechtalk, T1 Line Testing Guide, http://simpletechtalk.wordpress.com/2011/06/30/t1-test-guide/
