a 4 wired ethernet cord?!
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Thread: a 4 wired ethernet cord?!

  1. #1
    Blast From the Past
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    a 4 wired ethernet cord?!

    my router got hit by lightning last night... so i bought a linksys and threw out my old belkin

    now. internet had worked flawlessly for years with the same setup untouched in my garage... when i got up there to switch it out i found a 4 wire ethernet cable connected between my router and my modem.

    regular ethernet cable... only 4 wires...
    and it worked...


    i thought you had to have all 8 to get signal.. am i right??
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  2. #2
    Did someone said Pizza :) FanacooL's Avatar
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    I have seen something like that in my last job, well although it was 6 wires not 4 but i am curious to know about it too, how come the link still works with not all of the eight connected.
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  3. #3
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    Hey Hey,

    I guess it all depends on who you talk to

    I've seen PCMCIA Network cards with hardwired cables off them that only have four wires inside... I know networking profs that have failed students for crossing pins 4 and 5..

    Standard (straight-through) Pinout

    1 2 3 4 5 6 7 8
    1 2 3 4 5 6 7 8


    Crossover Pintout

    1 2 3 4 5 6 7 8
    3 6 1 4 5 2 7 8

    Notice their are a couple that don't change?

    This is because all you require are your Transmit Pair (TX+ and TX-) and your Receive Pair (RX+ and RX-).... The reason you use a cross-over is because you're using like devices (2 Computers for exampe)... and if both transmit over the same wire and receive over the same wire, you'll have a problem..

    I can't hook both ends of the garden hose up to faucets and expect water to come other both the ends at the same time... I need a steady flow in one direction... with one entry and one exit... Imagine if every road was a one way street but you both down it in both directions.. very few people would get out alive... This is how cabling works (which is why we cross them)..

    So as you can see.. only 4 are required... now this applies to 10BaseT and 10/100 (100BaseT) only.... With Gigabit all 8 are required (a new type of encoding is used and a new type of data transmission)

    The other wires in 100Mb ethernet are basically just shielding... they help to eliminate things like cross talk.... I've even heard people say that if you use the standards for wiring (specific colours in each pin position) that you'll get better speeds than if you select at random (although either will work) and they claim this is because of the shielding provided... however I can't prove that...

    Anyways the company in question cheaped out.... they saved on the cost of four small copper wires... but I guess in the end that adds up...

    Hopefully that explains it all without confusing you more..

    Peace,
    HT
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  4. #4
    Blast From the Past
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    yep, explains alot

    although after i got our linksys router it wouldnt accept a signal from the 4 wire cable, so had to get the full set of 8 up there....

    interesting though
    work it harder, make it better, do it faster, makes us stronger

  5. #5
    AO Senior Cow-beller
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    If I recall correctly, 10Base-T and 100Base-T only use 2 of the 4 pairs of wires, as described by HTRegz above. Some food for thought:

    http://en.wikipedia.org/wiki/10BASE-T
    http://en.wikipedia.org/wiki/RJ-45

    And the bottom of that second page has a slew of links to Category 3 and Category 5 cabling descriptions, as well as a bunch of other boring EE type of stuff.

    Theoretically, you could wire your new router to the modem via 4 bare copper wires connected properly into the opposite RJ-45 jacks...but don't count on actuall making it work.
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