tutorial: UTP cables
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  1. #1
    Senior Member cwk9's Avatar
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    Post tutorial: UTP cables

    A tutorial by cwk9
    Every thing you wanted to know about UTP buy were afraid to ask

    A few questions that need to be answered before we get started.

    Q: What does UTP stand for?
    A: UTP (Unshielded Twisted-Pair Cable).
    Q: What does UTP look like?
    A: Itís that blue cable thatís always running around computer labs.
    Q: Were can I find a video of a man shooting a TV?
    A: Try here http://www.howstuffworks.com/what-if-shoot-tv.htm
    Q: Is there STP (Shielded Twisted-Pair Cable) cable to?
    A: Yes but it is more expensive and is rarely used in computer labs.
    Q: How is UTP different from Cat5?
    A: UTP is a type of wire; cat5 is a TIA/EIA standard. But for the purpose of this tutorial I will mostly be referring to cat5 cable. There are also Cat 5e Cat6 and Cat7 but most networks are still cat5.
    Q: Why are your writing this donít you have anything better to do?
    A: No.


    Letís start with whatís in a UTP cable. If you cut open your standard UTP cable you will find that it is not one wire but 8 wrapped in a blue outer jacket. The 8 wires will be twisted in pairs. In addition each pair of wires is wrapped around each other UTP must follow precise specifications as to how many twist are permitted per foot of cable. Each wire is a different color so that you know witch order to place them into the RJ-45 connector (more on this latter). There are two reasons for the twisting. One is to reduce crosstalk.

    Definition from Cisco
    CROSSTALK: When electrical noise on the cable originates from signals on other wires in the cable, this is known as crosstalk. NEXT stands for near-end crosstalk. When two wires are near each other and untwisted, energy from one wire can wind up in an adjacent wire and vice versa. This can cause noise at both ends of a terminated cable

    The other is to limit signal degradation RFI (radio frequency interference) and EMI(electro-magnetic interference). Some things you should try and avoid to minimize EMI and RFI are.

    -Televisions
    -Radios
    -Microwaves
    -Heaters
    -Welders
    -Computers
    -Motion sensors
    -Motors
    -Fluorescent lights

    This wire twisting technique works so well you will rarely need STP wiring to deal with RFI/EMI. Once as a test I tried running some cat5 into ceiling then wrapped around a Fluorescent light 20 times and then back down and it still worked perfectly. So just what is in the 8 little wires? Copper of course. Either 22 or 24 gauge with an impedance of 100 ohms to be exact. If you are wondering why UTP CAT cables are so popular and most other cables have died out there a few compelling reasons.

    -CAT is cheap, cheap, cheap.
    -you donít have to worry about terminators (not the terminators for the movie the BNC kind)
    -UTP has a diameter of about .43cm so itís easy to work with. If you have ever seen an old thicknet (garden hose coax) cable you would understand what a god send 0.43cm must have been.
    -Works with RJ connectors
    -Fastest copper based networking media.
    -Its blue

    Of course itís not perfect there are a few draw backs.
    -More prone to EMI/RFI than coaxial cable and STP.
    -Can only go about 100 meters before it needs a boost from a repeater or other networking device. You might want to keep it less than 70m just to be safe. Some coax cables can go 500m and fiber goes even further.
    -Its blue

    Back to those color coded wires. If you buy the wire in bulk you will need to attach it to something. Cables will most often connect to an rj-45 connector (phone is rj-47) or patch panel. What order you place the wires into the rj-45 determines weather your making a straight-through cable or crossover cable. Straight-through cables maintains the pin connection all the way through cable. Hence pin 2 on one end will be pin 2 on the other. Cross over cables are specific to Ethernet, pin 1 at one end should be connected to pin3 at the other end; pin 2 at one end should be connected to pin 6 at the other. Crossover cables are used to directly wire two computers together or connect to a networking device that does no perform the cross over for you. Devices that need a roll over cable are usually designated with an X near the port. For everything else thereís straight-through cables. Placing all those wires in to the rj-45 in the right order is a bigger pain in the ass than you might think. Itís not to be attempted by anyone with lousy dexterity or a short attention span. Here are some links to help you build your own cables.
    http://www.informit.com/content/inde...9200FBE28F9%7D

    http://howto.lycos.com/lycos/step/1,...+20002,00.html

    The first layer of the OSI model is the physical layer which means that no layer above it can function with out it. Because cables are in that layer we can make the logical assumption that your network is only reliable as the cabling used in it. To save your self some trouble you might want to get a cable tester so you can test the cables youíve made before you start running them through the walls. Cable testers (sometimes called time domain reflectometers or TDRs) vary in complexity. Some only have a red and green light on them others will tell you what kind of cable you have, what wires are working and how long it is. Of course if you donít need to worry about wire testing that often you can just connect two computers and have them ping each other.

    A little more Q and A to answer any questions you might still have.

    Q: What Ethernet specifications use UTP?
    A: 10BaseT, 100BaseT, 100BaseTX and 1000BaseT use UTP. 10Base2 and 10Base5 are coax. 100BaseFX is fiber
    Q: I want to wire my LAN with pink wires. Does Ethernet cable come in pink?
    A: I have seen yellow cross-over cables but other wise there all blue. You could always use spray paint.
    Q: is there anything more boring than talking about Ethernet cables
    A: Yes http://radioqualia.va.com.au/freeradiolinux/a

  2. #2
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    nice tutorial!

  3. #3
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    Little follow-up if I may... (not that you have a choice

    Their's also Cat3, but that's limited to 10mbps. Don't buy it anymore, not worth it: get Cat5 or Cat5e

    XXXBaseY should be interpreted as:
    XXX=speed in mbps
    Base=well, base!
    Y=media type: T as in Twisted Pair of course, but 2 and 5 you ask?
    2 = thin coax, the 2 is from 200m max range, but should actually be read 180m (go figure!
    5 = thick coax, 500m max range...

    In fiber, beside FX there's SX and LX, LX having longer range (10km...)

    And a little correction on that Q&A: UTP DOES come in diffrent colors (although I've never seen pink!)

    Another thing that might be of interest: there are 3 types of UTP cables:
    -riser: used mainly in walls, hence "riser". Maid with solid core conducters so less flexible.
    -plenum: mandatory (depending on building codes) in air conduits (like supspended ceilings). Also maid from solid core conductors but the cable envelope doesn't produce toxic vapors when it burns (made of teflon). More costly...
    -patch: used mainly between patch panels / switches / computers. Maid with multi-core conductors so more flexible. Costs more too...

    you can know what kind of cable it is by looking at the printings on the cable envelope:
    "CMR OR MPR" = riser (cmR, mpR)
    "CMP OR MPP" = plenum (cmP, mpP)
    "CSA OR CMG" = patch

    More info: http://www.mohawk-cdt.com/prod/

    Ammo
    Credit travels up, blame travels down -- The Boss

  4. #4
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    Originally posted here by ammo
    [And a little correction on that Q&A: UTP DOES come in diffrent colors (although I've never seen pink!)

    Ammo [/B]

    I have. you dont want to. Purple too.
    Remember -
    The ark was built by amatures...
    The Titanic was built by professionals.

  5. #5
    Senior Member cwk9's Avatar
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    Today I saw a green and orange utp cable. I still have yet to see pink.
    Its not software piracy. Iím just making multiple off site backups.

  6. #6
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    just a thought: If you think you have a faulty cable look check this:

    Check the correct cable patter:

    White Orange == Orage & White striped (applies to all White <COLOR> sequences)

    White Orange, Orange, White Green, Blue, White Blue, Green, White Brown, Brown

    Also, make sure the cables are all the way through the RJ-45. If you look at the fron of it, you should see the end cabled gently touching the RJ-45's plastic font.

    The cat5 cables last a pretty long time, so, age really isn't a factor. However, the cable will probably need to be re-crimped.
    Viper

  7. #7
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    There are to color order standards:
    EIA/TIA 568A -> White Green, Green, White Orange, Blue, White Blue, Orange, White Brown, Brown
    EIA/TIA 568B ->White Orange, Orange, White Green, Blue, White Blue, Green, White Brown, Brown

    And a crossover cable is a cable with one end 568A and the other end 568B...

    Ammo
    Credit travels up, blame travels down -- The Boss

  8. #8
    Antionline Quitter..Srsly
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    good post very helpful...kinda reminds me of my CCNA class ...like withing the first week we had that...annoying that calss was
    \"\"A weak mind is like a microscope, which magnifies trifling things but cannot receive great ones.\" ó G.K. Chesterton, 19th-century English essayist and poet\"

  9. #9
    Senior Member cwk9's Avatar
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    I just finished cisco semester one so thatís were most of this stuff is coming from.
    Its not software piracy. Iím just making multiple off site backups.

  10. #10
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    Hey, is CCNA worth it? I'm thinking of getting it, but I don't know if my university courses will cover most of the CCNA... Think I'd be wasting my time?

    Ammo
    Credit travels up, blame travels down -- The Boss

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