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cable not working!!!

Discussion in 'Electronic Basics' started by Ahmed Samir, Aug 31, 2003.

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  1. Ahmed Samir

    Ahmed Samir Guest

    hi there

    i needed this small ethernet cable segment-20meters-, and i remembered that
    a friend told me that i can use normal telephone wire -four pairs- instead
    of the UTP cat.5 one

    now i made the cable and put the connectors in it -RJ45- but it wont work,
    there is an LED that lights when cable is connected between the ethernet
    card and the ethernet hub ,but the LEDs wont light, although i tested the
    continuity of the 8 wires of the cable many times.

    does anyone has an explaination???

  2. What has happend to your SHIFT key ??
  3. Ahmed Samir

    Ahmed Samir Guest

    it's fine, how about urs??
  4. the Wiz

    the Wiz Guest

    Is your network equipment 10MHz or 100MHz?

    10MHz connections will work over Cat3 wiring, but 100MHz is iffy, even at short

    Does your wiring match this diagram? Holding the connector with the latch down:

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  5. Ahmed Samir

    Ahmed Samir Guest

    it's 100MHz ethernet
  6. Lord Garth

    Lord Garth Guest


    You'll require CAT5e cable AND you need to wire the pairs as shown for 568B.
    If you don't, operation at 100Mb/s is not likely. If you are wiring two
    together without a hub or switch, you'll need to wire a crossover cable.
    This is
    where pins 1& 2 interchange with pins 3 & 6 at the other end and vice versa.
  7. Ahmed Samir

    Ahmed Samir Guest

    why do pairs have to be in this order, isnt it just pin to pin connection
    between the hub and the ethernet card?
  8. Lord Garth

    Lord Garth Guest

    The signals are differential and must be paired. There is no reference to
    ground, there is TX+ followed by TX- etc. The input can not reject common
    mode noise if the wires are not a twisted pair. Remember that you are not
    dealing with DC here!

    There are only 4 wires needed, specifically pins 1 & 2 which is one pair and
    pins 3 & 6 which is the second pair. You would find it hard to build if you
    didn't use all 8 wires. CAT5e wire has specific characteristics that are
    required for 100Mb/s operation. One specification of CAT5e is the number
    of twists per foot.

    Don't send a phone line down your network cable. You will break the
    specs for 100Mb/s networks. There are specific connectors used for the
    sockets, they are NOT the same as a telephone socket (RJ-45). The allowable
    length of wire that can be untwisted is strictly called out. Look up
    NEXT or Near End CrossTalk.

    These things are not hard to build, just build them right and they will
    serve you long and well.
  9. You didn't conect the wires correctly. Do it right and use Cat5, and
    don't forget that if you are connecting two computers, you have to use
    a crossover. Also, take your questions to the appropriate newsgroup

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