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Cat5/Cat5e/Cat6 UTP Network Wiring and RJ45 Pinout

  • How far can I go with Cat5/Cat5e cable?
    According to ANSI/TIA/EIA-568-A standard, "horizontal wiring" from a wiring closet to the outlet should be 90 meters or less, plus another 3 meters for a patch cord to the workstation. In round numbers, that's about 300 feet.

    If you plan to connect between buildings with different power sources, or go beyond 300 feet, you should consider using fiberoptic line with a media converter at each end.
  • What's the difference between 568A and 568B?
    TIA/EIA-568A and -568B are two standards for connecting Category 3 and Category 5 wire to connectors. Both are appropriate for high speed data, though 568B is somewhat more common for installed wiring and 568A is more common in jumpers. There is no performance advantage either way. The only real difference between the two is the order in which the pairs are used (orange and green).

    Hold a cable as if to plug it into a wall jack, the locking tab down (contacts facing you). The contacts are numbered 1-8 from left to right. Here's what you will see:
Pin 1: Green
Pin 2: Green
Pin 3: Orange/White
Pin 4: Blue
Pin 5: Blue/White
Pin 6: Orange
Pin 7: Brown/White
Pin 8: Brown

Pin 1: Orange/White
Pin 2: Orange
Pin 3: Green/White
Pin 4: Blue
Pin 5: Blue/White
Pin 6: Green
Pin 7: Brown/White
Pin 8: Brown
568A and 568B may be used interchangeably in a system SO LONG AS both ends of a given cable are terminated the same way.
  • Can I use a modular coupler to join two network cables?
    There are some couplers out there designed for category 5 wiring, but most are not -- they're mostly intended for extending cellular and business phone sets. And it isn't always apparent which are which. In general, you are better off using one cable of the right length than joining several together.
  • What are those plastic clips that came with my RJ-45 jacks?
    They provide some strain relief (so the wire doesn't pop out of the connection) and keep dirt and moisture out. They are not a replacement for using a proper punchdown tool to make the wire connection.

  • Why are the RJ-45 plugs I crimped on failing?
    There are two varieties of network cables that should be used: one has solid conductors and is generally used for permanent wiring; the other has stranded conductors and is generally used for making flexible patch cords. Some RJ-45 plugs are designed for solid wire (their contacts straddle each conductor), others are designed for stranded wire (and pierce through between of the strands). Using the wrong type of plug for a given type of cable will make a poor connection that may fail intermittently. There is a third variety of RJ-45 plug that will work with either solid or stranded wire.

    Another cause for bad crimp connections is using the wrong crimping tool for a given brand of connector. In particular, many AMP brand connectors have the strain reliefs located in a different position than most. Using a standard tool with these plugs will damage the plug.

    Additionally, ensure that the wires when cut are of equal length and pushed all the way up into the plug so the copper is flush at the top.

    RH45 Connector

  • Why do some patch cables have boots?
    They look nice, and the companies that make patch cables can sell them for more money. Also, when you pull a cable back through a nest of other wires the boot keeps the locking tab on the plug from getting snagged and broken off. (That probably isn't a big concern for most home networks!)

    Do boots keep dust out? Possibly, but a jack with a plug in it shouldn't be getting stuff in there anyway... it's the empty jacks that collects dust.
  • Is plenum cable any better than PVC?
    Plenum rated cable is required by some fire codes if you run wiring in locations where the HVAC system moves air -- above suspended ceilings and through cold air returns, for instance. This cable is designed to withstand higher temperatures than ordinary PVC jacketing and burns less readily than PVC. For most homeowners, plenum rated cable is probably not necessary and typically costs 2-3 times more than PVC. There is no electrical difference between the two, and either will perform equally well.
  • What's all this about twists?
    Each network cable contains four pairs of wire, each pair twisted at a regular rate. Better grades of cable deliberately apply different amounts of twist to each pair. 10-Base-T and 100-Base-T lines use two pairs, one to transmit and one to receive data, copper Gigabit uses all four pairs. The twists provide a consistent impedance along the length of the cable, reduce the crosstalk between pairs and tend to make induced noise cancel out.

    To preserve these qualities, it is important to maintain the twist when installing connectors, right up to the point of termination. You shouldn't untwist more than about a half an inch of wire. And when you install the cable, take care not to pull it tightly or make sharp bends, as those will disrupt the pairs' integrity.
  • What are 66 and 110 blocks?
    Both are "punchdown" blocks used to interconnect voice and data systems in an orderly way. Type 66 blocks have been around longer and were developed for the phone company; they make it easy to connect multiple phone taps to a given line, and with the use of bridging clips provide an easy way to disconnect inside wiring from a circuit for troubleshooting. Older 66 blocks are not suitable for category 5 wiring, although several manufacturers have come out with revised 66 blocks that will work.

    110 blocks are newer and are preferable for computer work: for one thing, they make it easier to preserve the twist in each pair right up to the point of connection. Most Category 5 jacks also use type 110 terminals for connecting to the wire.

    A traditional impact punchdown tool with interchangeable bits like a Harris/Dracon will cost about $75 and can punch either 66 or 110 blocks (or any number of other types). Less expensive impact tools without interchangeable bits run about $25. Both kinds of impact tools both connect and trim the wire to the correct length. For a couple of bucks you can get a plastic tool for 110 blocks that might get you by for a few connections, but it won't trim the wire. Personally, I would stick with an impact tool.
  • Isn't coaxial cable better?
    Coax is always better than twisted pair. The 10-Base2 is a limited by the equipment on either end of the cable. The cable has a very high bandwidth capability, if the proper equipment is attached on either end. If you look at it from a very narrow data persons point of view, not an electronics person, 10-Base2 is slower than cat 5 cable. Cat 5 cable won't come close to RG-58.
  • What is the difference between Cat-5 and Cat-5e?
    Cat-5e is enhanced Cat-5 cable. The only difference between the two UTP cables is the tested signal level. Cat-5e is tested at a higher frequency or signal level than regular Cat-5. You could find Cat-5 and Cat-5e anywhere for about the same price. Getting Cat-5e means you are getting cable that is tested under higher standards.
  • What is a crossed or cross-over Ethernet cable and how do i make one?
    A crossed Ethernet cable is used for communication between two computers without using network gear such as a router, switch or a hub.

    To identify a cross-over Ethernet cable, hold one end as if to plug it into a wall jack, the locking tab down (contacts facing you). The contacts are numbered 1-8 from left to right. One end will have a different color sequence to the other. A crossover cable, like a straight through cable, works both ways.

Using the 568B standard, the cross-over wiring sequence for ONE end:
PIN 1 - Orange/White
PIN 2 - Orange
PIN 3 - Green/White
PIN 4 - Blue
PIN 5 - Blue/White
PIN 6 - Green
PIN 7 - Brown/White
PIN 8 - Brown

And for the OTHER end:
PIN 1 - Green/White
PIN 2 - Green
PIN 3 - Orange/White
PIN 4 - Brown/White
PIN 5 - Brown
PIN 6 - Orange
PIN 7 - Blue
PIN 8 - Blue/White

In practicality, for straight-through cables, it doesn't matter what the color sequence is. It will still work and there will not be a degradation in network performance. However, from a design perspective, you should adopt one of the two standards and use it throughout your project. If you are adding network cables to an existing setup, follow the standard that's being used at the premise. In the majority of the cases you likely see EIA/TIA-568B being used.