The RJ-45 connector is used in Ethernet networks for connecting the cable to the equipment. It's pretty obvious that it needs to be properly installed. Ethernet 100BASETx operates at 100 Megabits/second, a pretty good clip for unshielded twisted pair wire! A very large number of the problems in a new network installation can be attributed to cabling and bad connections. The network cards and software are useless without a good connection!
The RJ-45 has eight connections, and is used with a four-pair unshielded twisted pair (UTP) cable. The wire is 22-24 AWG, usually solid core. Stranded cable is also available and is much more flexible, but much harder to work with. You'll need to use the proper connector for the type of wire you use. It pays off to use the good stuff, your network's health depends on it!
There are also different categories of UTP. Either Cat 3 or Cat 5 cable should be used for Ethernet networks. You should also be aware that there is special "plenum" cable for cable runs in false ceilings. Plenum cable does not emit toxic fumes in case of fire. For most cable runs, it is advisable to use Cat 5 plenum cable… it will work for all situations.
OK, to connect the RJ-45 connector to the UTP, you'll need to strip two or three inches of insulation from the wires. Be careful not to nick the wires or their insulation. There are tools made for this purpose… if you have one, use it! If you don't, you can use a knife or xacto knife. Just score the insulation (it doesn't take much), then pull it off. Note that each pair of wires is twisted… the number of twists per foot is fairly critical. They attenuate the crosstalk and determine the characteristics of the cable. It's important to use the proper cable - telephone cable won't work!
Fan out the wires and straighten them out as best you can. Oh… did you notice that the wires are different colors? There's a reason for that… you've got to follow the color-code! Eight wires - eight colors… hmmmm! Here's the color code for a straight-thru (EIA 568B) Ethernet cable(the first color is the dominant color):
| Pin 1 | White/Orange |
| Pin 2 | Orange/White |
| Pin 3 | White/Green |
| Pin 4 | Blue/White |
| Pin 5 | White/Blue |
| Pin 6 | /Green/White |
| Pin 7 | White/Brown |
| Pin 8 | Brown/White |
Now for the fun part! You'll need to dress the wires in the
proper order and lined up so they'll fit into the connector. This takes some
patience and really makes you feel like a klutz! Keep after it though, and do
the best you can. Work at it until the wires are flat and in order. It's easy
to get frustrated, but remember who is boss here!
Ok, now that you're totally frustrated, you have to trim the
wires to about a half an inch. You can use a pair of flat-nose pliers to hold
the wires in place or just tough it out and hold them in place. If you've done
it right, you can actually let go of the wires (See the picture? I did it right!).
You must make sure that the wires are in the proper order!
Make sure you use SHARP diagonal-cutters!
Carefully slide the wires into the connector. They each have to fit into their own little individual slot, so watch what you're doing. Carefully slide the wires into the connector.
Notice the alignment in the photo. Looking at the "bottom" of the connector (the side with no tab) and from the cable end, Pin 1 is on the left. The white-orange wire goes in Pin 1!
It's really easy to cross the wires here, and you don't want that to happen!
When the wires are properly inserted, you should be able to see copper when looking at the end of the connector. If not, you'd better start over again! I'm serious… the wires need to be seated all the way before crimping. You'll have a bad connector if not seated properly. Either the wires are too short or you cut them crooked. Also the outer sheath needs to be far enough into the connector for the crimp part of the connector to hold it.
Use a high quality crimper when making RJ-45 connections. Spend a minimum of about $40 or $50 on it. You can easily spend quite a bit more and if you're making a lot of cables it's worth it.
Most crimpers won't release until you squeeze them hard enough for a proper connection. If you're a weenie, you may have to have a friend do your crimping.
OK, that's it! It's an excellent idea to test your cable with a cable tester. Of course, you'll have to put a connector on the other end of the cable first! You can get a basic cable tester for around $100 or a really good one for $2500. The basic one will check for good connections. The really good one will check for good connections, impedance, length, crosses, near-end-cross-talk (NEXT), and lots of other stuff.
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