Network Building: Attaching RJ-45 Connectors

RJ-45 connectors for twisted-pair cables aren’t too difficult to attach if you have the right crimping tool. The trick is in both making sure that you attach each wire to the correct pin and pressing the tool hard enough to ensure a good connection.

Here’s the procedure for attaching an RJ-45 connector:

  1. Cut the end of the cable to the desired length.

    Make sure that you make a square cut — not a diagonal cut.

  2. Insert the cable into the stripper portion of the crimp tool so that the end of the cable is against the stop.

    Squeeze the handles and slowly pull the cable out, keeping it square. This strips off the correct length of outer insulation without puncturing the insulation on the inner wires.

  3. Arrange the wires so that they lay flat and line up.

    You’ll have to play with the wires a little bit to get them to lay out in the right sequence.

  4. Slide the wires into the pinholes on the connector.

    Double-check to make sure that all the wires slipped into the correct pinholes.

  5. Insert the plug and wire into the crimping portion of the tool and then squeeze the handles to crimp the plug.

    Squeeze it tight!

  6. Remove the plug from the tool and double-check the connection.

    You’re done!

Here are a few other points to remember when dealing with RJ-45 connectors and twisted-pair cable:

  • The pins on the RJ-45 connectors aren’t numbered, but you can tell which is pin 1 by holding the connector so that the metal conductors are facing up. Pin 1 is on the left.

    Attaching an RJ-45 connector to twisted-pair cable.

    Attaching an RJ-45 connector to twisted-pair cable.
  • Some people wire 10baseT cable differently — using the green and white pair for pins 1 and 2 and the orange and white pair for pins 3 and 6. This doesn’t affect the operation of the network (the network is color-blind), as long as the connectors on both ends of the cable are wired the same!

  • If you’re installing cable for a Fast Ethernet system, you should be extra careful to follow the rules of Category-5 cabling. That means, among other things, making sure that you use Category-5 components throughout. The cable and all the connectors must be up to Category-5 specs.

    When you attach the connectors, don’t untwist more than1/2 inch of cable. And don’t try to stretch the cable runs beyond the 100-meter maximum. When in doubt, have cable for a 100 Mbps Ethernet system professionally installed.