1

Telecom Cabling

Trouble shooting

2

Telecom Cabling

Trouble shooting is a skill that comes with experience and is developed over time.

For the majority of cabling issues you can use your four pair tester to identify problems with pair continuity, which means you simply re-terminate the cable.

For those projects that have to be certified you will be using a cable analyzer that will identify other problems other than continuity issues.

3

Telecom Cabling

In a previous lesson we covered two of the most common problems that the installer will run into when using a cable analyzer.

NEXT or FEXT (near end cross talk) (far end cross talk), these are the easiest to fix because again its just a matter of re-terminating the jack or patch panel.

The Fluke DTX 1800 is one of the most commonly used analyzers in the industry

For $5000.00 dollars you can add one of these to your tool bag (base model only)

4

Telecom Cabling

Another test result you will see is attenuation failure, these are trickier to trouble shoot, as stated in the previous lesson on testing make sure the test cord is fully seated in the port to be tested on both ends.

You will then check the meter to see how far out the fail point is, the cable analyzer will show you the footage and you can walk it off and visually inspect the cable, remember that the footage is an average so you will be with in + or – 5 feet.

5

Telecom Cabling

One of the things you’re looking for when trouble shooting attenuation problems are “shiners” this happens when the cable is damaged and the jacketing is stripped off the conductors revealing copper, it shines when you put your light on it.

6

Telecom Cabling

Shiners occur at direction changes such as when the cable tray has a 90 degree turn or happen when a cable is pulled through a conduit stub that feeds down to a work box.

There are no cable splices allowed in any link so don’t plan on splicing a bad cable, it won’t pass the certification test, you will have to replace the cable.

7

Telecom Cabling

Cable kinks cause attenuation problems too, by locating a kink you can try straightening it out and “massage the cable” another telephony field term, then re-test and hope for the best.

Its because of attenuation problems that we always pull an extra set of cables to the furthest corners of the floor being cabled, these cable sets become our back ups and are labeled “for future use”.

8

Telecom Cabling

Another test result that you may come across is noise, this means your cable is resting on or very close to an EMI source.

What is EMI and what can cause EMI or noise problems?

9

Telecom Cabling

Fluorescent lights, fan motors, electrical cables and audio or paging circuits are the main culprits of EMI.

You will have to re-route cables around these sources to eliminate noise, sometimes a static charge remains in a four pair cable, try temporarily grounding the pairs to the rack and re-test.

10

Telecom Cabling

During installation you will have a lot of miss marked cables or no cable IDs at all, this where you use your toner and wand (inductance amplifier) to tone out the cables.

UTP cable, especially CAT 6 is designed to reduce noise amongst the pairs so toning these

cables is challenging, you may have to do a continuity test on the pairs.

11

Telecom Cabling

Testing continuity on the pairs is a two man job, one person twists the blue pair together and on the other end someone else uses their tone generator set to continuity to test for a short, (the LED will light up when there is a short).

For verification the tech will untwist the blue pair and the other tech will check for an open, if an open shows then the cable in question has been found.

12

Telecom Cabling

By using a four pair break out you can send tone on all four pairs which will make it easier to identify the cable in question.

Twist the leads together to form only two contact points and attach your tone generator to the two leads.

13

Telecom Cabling

Another problem a technician may run into is wiring configuration miss match, 568A patch panels wired to 568B jacks.

This is essentially a transposed pair problem, this happens because universal patch panels are hardwired for 568A and the orange and green color tabs are missing from the 110 punch down modules. (Siemon’s universal patch panels).

14

Telecom Cabling

Be sure that all components in the system are all the same category, once in a while a CAT 3 or 5e jack may be inadvertently installed on a CAT 6 job.

All category rated device are stamped with their designated categories…sometimes the simple stuff eludes us.

15

Telecom Cabling

Some of the locations that are installed on a project may only be 20 feet away form the TR, these locations will not test out because the drop is to short.

To test these short distance locations you need to make a 50 foot patch cord and test through the longer patch cord.

Category 6 coupler to connect two patch cords together

16

Telecom Cabling

Through out this course you’ve seen the end results of great installs and cabling, what happens when you go out into the industry to provide service at existing locations……

A wall mount patch panel with cables running up to another floor, these cables are 150’ patch cords and are not labeled.

Stragglers

17

Telecom Cabling

• What do you do with this, this was a service call to add two more locations……

18

Telecom Cabling

A little closer lookThere is a patch panel in there.

Power strip

19

Telecom Cabling

One thing to be careful of is to make sure you don’t accidently shut the power off to the network while your working around the relay racks.

Sometimes its easier to unscrew the patch panel from the frame and screw it back on backwards then terminate your adds onto the patch panel from the front of the rack, hopefully there is enough slack on the cable bundle to do this, you may have to cut a few tywraps.

20

Telecom Cabling

Another service call“Two of our phones don’t work”. The PBX is in another room with another one of these closets in between.

21

Telecom Cabling

The in between closet, 66 blocks aren’t labeled, 4 pair is run through the cross wire fields and loose cross wires every where.

Lightning protection, old school fuses

22

Telecom Cabling

One of the most important things you can do is write down every thing you do, if you move a cross wire write down what block and pair it came from just in case you have to put it back.

Obviously you need to proceed with caution when dealing with networks that look like rats nests, using string or tywraps you can secure bundles out of your way to free up a small work space.

23

Telecom Cabling

When the AHJ (authority having jurisdiction) arrives at a site for an inspection he will look at several areas in the low voltage install;

Independent support systems for the cabling.Grounding and bonding.Proper fire stopping.The use of plenum materials i.e. tywraps, cables etc. were applicable.He may also check for apprenticeship cards and licenses.

24

Telecom Cabling

The trades are considered a craft, hence “craftsman” and as such they encompass a variety of skill sets such as mechanical ability, problem solving, creativity, customer service skills, communication skills and professionalism.

Your work and final product will be a direct reflection on you and your company and of course this holds true from start to finish whether you are on a long term project or a quick service call.