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VDV TERMINATION

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UTP cables are terminated with standard connectors (plugs and jacks) or punch downs. The plug/jack is often referred to as a "RJ-45", but that is really a designation for the "modular 8 pin connector" terminated with a USOC pin out used for telephones. The male connector on the end of a patch cord is called a "plug" and the receptacle on the wall outlet is a "jack."

These terminations are called "IDC" for "insulation-displacement connections," by the way, since the wires are held in knife-edge terminations that slice through the insulation and dig into the copper wire, forming a tight seal.

In LANs, there are two possible pin outs, called T568A and T568B that differ only in which colour coded pairs are connected - pair 2 and 3 is reversed. Either works equally well, as long as you don't mix them! If you always use only one version, you're OK, but if you mix A and B in a cable run, you will get crossed pairs.

Each pair consists of a coloured wire and a white wire with a matching colour stripe. The stripe wire is "tip" and the solid colour wire is "ring," referring to the tip of the old 1/4" telephone plug and the ring around the shaft that makes the connections.


Jacks:

The jacks are then terminated with these layouts, looking into the jack:
The jacks are then terminated with these layouts, looking into the jack: Note that the only difference between T568A and T568B is the reversal of pairs 2 and 3 - it's only a color code change.
Note that the only difference between T568A and T568B is the reversal of pairs 2 and 3 - it's only a colour code change. Jacks usually have 110-style punch downs on the back which can be terminated with punch down tools, using special manufacturer's tools or even a snap-on cover for the connector.



The colour codes are going to look like this for these jacks.

Jacks usually have 110-style punch downs on the back which can be terminated with punch down tools, using special manufacturer's tools or even a snap-on cover for the connector. Again, you MUST keep the twists as close to the receptacle as possible to minimize crosstalk.

Note: Cat 3 jacks and all plugs are going to use these colour codes shown to the left.




Plugs:

The plugs are terminated by straightening out the wires in proper order and crimping on a connector. Like we said before, you MUST keep the twists as close to the plug as possible to minimize crosstalk.

Patch cords:

They generally use stranded wire for flexibility but can be made with solid wire for higher performance. Note that plugs may be different for each type of wire, so make sure you have the right type.

Crossover Cables:

Normal cables that connect a PC/NIC card to a Hub are wired straight through. That is pin 1 is connected to pin 1, pin 2 to pin 2, etc. However, if you are simply connecting two PCs together without a hub, you need to use a crossover cable made by reversing pair 2 and 3 in the cable, the two pairs used for transmission by Ethernet. The easy way to make a crossover cable is to make one end to T568A colour coding and the other end to T568B. Then the pairs will be reversed.

Punch downs:

Sometimes there are cross connects using punch downs in the telecom closet, more common on telephone wires than data. These are called punch downs because the cable is punched down into the IDC contacts with a special tool, called (surprise!) a punch down tool. Of course, you MUST keep the twists as close to the punch down as possible to minimize crosstalk. Punch downs come in 4 varieties: 110, 66, Bix and Krone. Most popular for LANs is the 110.

110 Block
110 block (left) 66 block (right)
66 block





Patch panels offer the most flexibility in a telecom closet. All incoming wires are terminated to the back of the patch panel on 110-style punch downs

Patch Panels

Patch panels offer the most flexibility in a telecom closet. All incoming wires are terminated to the back of the patch panel on 110-style punch downs. Then patch cables are used to interconnect the cables by simply plugging into the proper jacks. Patch panels can have massive number of cables, so managing these cables can be quite a task in itself. It is important to keep all cables neatly bundled and labeled so they can be moved when necessary. However, it is also important to maintain the integrity of the cables, preventing kinking or bending in too small a radius which may adversely affect frequency performance.