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Data Removal & Recovery

A cabling demonstration

Patch cabinets come in sizes ranging from wall mounted frames carrying one or two patch panels plus a switch, to full size floor standing frame with lockable sides and glass doors with up to 45U space.

The cable must be installed obeying a set of guidelines designed to preserve the electrical characteristics of the cable. The aim is to prevent ‘crosstalk’ between adjacent pairs within the cable and with other nearby cables.

Cable must not be bent too sharply. During installation (pulling cable) the minimum radius should be no less than 75mm. After installation 25mm is the minimum recommended for both Cat5 and CAT6. Great care must be taken when adding more cable later on, to maintain this minimum.
Leave at least 25% more space than you require when running cable
Don’t run the cable near mains cable, through lift shafts or any other electrically noisy environment. CAT5e may be run in 3-compartment trunking. CAT6 should be run in its own trunking at least 15cm from mains cable.
Cable should be supported using cable tray for horizontal runs and gently cable-tied every 50cm or so. Pulling the cable-tie too tightly will increase the crosstalk. Where cable must be run vertically, use a securely fixed cable tray and cable-tie in bunches of no more than 20 cables. Again, don’t pull the cable-ties too tightly.
When pulling cable, take care not to exceed the pulling weight of 25lbs on a single cable. Take the greatest care not to kink the cable, this weakens the copper conductors and violates bend radius guidelines.
When pulling cable through a hole in the wall, line the hole with a plastic pipe, run the cable through the wall at 90° and seal the hole with fire-retardant foam or other fire precaution.

In large cabinets, the cables should be gently supported on the vertical rise to their termination point. Cable-tie in bunches for each patch-panel (24 or 2 bunches for 48) every 20-30cms. Use plastic sleeving for the run within the cabinet. This helps with managing the bundles but also prevents any damage to the individual cables. If the cable run comes into the room at the ceiling, run the sleeving to just beyond the final ceiling support so that the cable bundles are organised and protected throughout the vertical run down the wall and the vertical run inside the cabinet.

It is helpful to treat smaller quantities of cable in the same way in small patch cabinets, simply because as more cable is added, a chaotic cabinet can only get more chaotic.

How to cable a small patch cabinet.

Tools: you will need a cable stripper for data cable, sidecutters, cable-ties, punch-down tool, screwdriver, cage-nuts and bolts.

Fig 1

There are two types of patch panel. The style I use here can be flipped over and bolted to the cabinet making termination easier. The second type is a shelf-like construction that needs a bolt-on frame to make things easier.

Fig 2

In this photograph, you can see that I have secured the bundle of cable to the frame as a temporary measure to hold in a convenient position. The cable is secured so that the last few to be terminated are long enough to reach.

Examine the patch panel wiring arrangement, each slot should be labelled with a coloured symbol. Some panels have the cable slit into two pairs as the one in the photograph above. Others terminate the whole cable in the upper or lower position. Check also for the version of the wire map, 568a use the green pair for pins 1 and 2, 568b use orange for 1 and 2.

Fig 3

Identify the first cable for termination and measure it for cutting. It needs a comfortable amount of slack, try and maintain the same amount for subsequent cables. Allow 1½ module widths. Use the stripping tool to cut the outer sheath, note that anti-clockwise produces a shallow cut – quite enough for CAT5e. Cutting too deeply may cut throughone of the conductors. This will be difficult to troubleshoot without a TDR meter and may need the whole cable to be replaced if you haven't allowed enough slack.

Fig 4

Separate the pairs and untwist sufficiently to place the individual conductors. Note that the marking for the contact differentiates between the colour/white and white/colour conductors.

Fig 5

You may notice that each coloured pair has a different twist rate. Try to maintain the twist to within ½” of the contacts, but don’t overtwist.

Fig 6

Punch down the pairs in the most comfortable order. If you can, place all the conductors and punch them all down in one go. On this style of patch panel, I find it easier to do the top two then the lower two last. If you look carefully at Fig 6, you will see that I have pushed the conductors down in a dog-leg, particularly obvious on the brown and green wires. With the wires like this, the puchdown tool will not trim the wire. You will need to pull the wire straight and punch down again. Try to keep the wires straight across the jaws of the contacts to avoid having the operate the tool twice. An audible clue to correct operation is a clean did-donk as the tool is pushed home.

Fig 7

A visual check on each conductor to make sure it is properly pushed home and trimmed.

Fig 8

Select the next cable, allow the same slack, measure, cut and strip. Place punch down and check.

Fig 9

As you complete each bunch of four cables, secure then with a small cable-tie – not too tight. When the whole panel is punched down, secure all the cables at one end – in this case with Velcro, but otherwise a cable-tie.

Fig 10

In this next photograph, I have deliberately left one conductor improperly terminated (third from the right, top row). When we terminate the floor or wall points we can test the circuit for continuity and correct pair termination.

Terminating the floor or wall points.

There are a variety of data modules available, some labelled ‘professional’ others labelled ‘euro style’

Fig 11

In this photograph, there are five data modules. The far right hand module is a telephone connector – note it has only six contacts. Most structured cabling solutions would use only data modules for a more flexible scheme. The first two modules are euro style, the two right hand data modules are the professional style. Note three are marked ‘568b’ to identify the wiring map used. I prefer the right hand data module. When choosing a data module, you need to check the mounting frame for the module fits the module and the back box to hold it.

First thing to do is fit the back box and feed the cable through a suitable hole. Please bear in mind to keep the bend radius correct and to avoid mains cable.

The cable needs to be cable-tied to the module to provide strain relief for the conductors.

Fig 12

Carefully trim the cable to the correct length. In a single gang box you can fit one or two data modules. The cable needs to be 4-5” long before stripping. Once the cable is terminated, the cable should not need cramming into the box to get the frame screwed on. Strip 1½” and attach to the module.

Fig 13

Separate the pairs, orange and blue to the top, green and brown to the bottom. Untwist enough for punching down.

Fig 14

Check the conductors are properly punched down and trimmed.

Fig 15

Connect one part of the test equipment to the data module and the other to the appropriate patch panel socket. Press the test button and….oh, the first pair is not properly terminated. Examine the patch panel and punch down properly. If the patch panel is correct, check the module. If there is still a fault, the cable is probably damaged. I did have a faulty batch of euro-modules last year where the two middles pairs made contact, but I had to push the patch cable in and hold it to connect the other two pairs. So be warned, you can meet unexpected faults.

Fig 16

That’s it, fixed it

Fig 17

Test completed OK. Screw down the mounting frame. I always leave the screw slot in a vertical position. It is a lot easier than bending down to look at every screw before undoing it the next time.