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Thread: How many conductors does Ethernet require.

  1. #1
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    Question How many conductors does Ethernet require.

    OK I know Cat 5, Cat 5E, Cat 6 etc all contain 4 pairs (8 conductors) but how many can I make it work with?

    I have a situation with a customer that is running a phone on one pair leaving 3 pairs for the PC. Now it appears one pair is open.

    Can I make it work on just two pairs?

    This is not subject to any testing or certification, all they care about is getting it to work. I suggested wireless but they do not want to go that way.

  2. #2
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    Bob I have never seen ethernet work on less than 4 pair. I am no expert but I have seen many times where one wire was loose and the system would not work.

    Obviously running a new wire is not a option so wireless, as you suggested, would be the way to go. Better yet use a wireless phone. They have phones that you plug in a transmitter at a wall jack and picks up a wireless signal for the phone.

  3. #3
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    Quote Originally Posted by Dennis Alwon View Post
    Bob I have never seen ethernet work on less than 4 pair.
    It has been functional on no more then three pairs for at least 5 years. It just stopped working.

    When I put a cheap leviton tester on it it indicated I had pairs 1,2 and 3,6 working.


    Since I posted this thread I found this

    Standards Summary

    which seems to indicate that I have enough and the problem is not the cabling.


    Obviously running a new wire is not a option so wireless, as you suggested,
    Distance is short, but it would be real tough and cost prohibitive.

    Better yet use a wireless phone.
    That is some great thinking but unfortunately it is not a standard phone it is a 'system' phone with many features.


    They have phones that you plug in a transmitter at a wall jack and picks up a wireless signal for the phone.

    Hmmm I wonder if that would run the special phone?

  4. #4
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    Quote Originally Posted by iwire View Post
    OK I know Cat 5, Cat 5E, Cat 6 etc all contain 4 pairs (8 conductors) but how many can I make it work with?

    I have a situation with a customer that is running a phone on one pair leaving 3 pairs for the PC. Now it appears one pair is open.

    Can I make it work on just two pairs?

    This is not subject to any testing or certification, all they care about is getting it to work. I suggested wireless but they do not want to go that way.
    Ethernet only requires 4 conductors, I don't remember which ones, but I'll try to find it.

    I have done what you want to do before and it will work.

  5. #5
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    ring and tip

    don't know if this is any help...........

    http://www.lanshack.com/wire_phone_jack.aspx

  6. #6
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    Quote Originally Posted by roger3829 View Post
    Ethernet only requires 4 conductors, I don't remember which ones, but I'll try to find it.

    I have done what you want to do before and it will work.
    I found it. Check out this link. You only need Pins #1, 2, 3, 6

    http://www.ertyu.org/steven_nikkel/ethernetcables.html

  7. #7
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    Quote Originally Posted by roger3829 View Post
    I found it. Check out this link. You only need Pins #1, 2, 3, 6

    http://www.ertyu.org/steven_nikkel/ethernetcables.html
    Thanks, that is what my tester indicated I had. :smile:

    A little background, the customers workstation stopped working, they called in their IT contractor and the IT guy figured the cable was bad. He tested the cable but he was on the wrong cable at the patch panel. To be fair he was on the port that was marked for that work station but that was incorrect so of course his test showed an open condition.

    Once I put a toner on the work station end I found the correct port at the patch panel. Once I tested that port to the work station I had good continuity on pins 1,2,3,6.

    It seems they have another issue. I left a detailed note for the IT that comes back with my cell number so we can talk about it.

    I just wanted to make sure two pairs could do it. :smile:

  8. #8
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    Quote Originally Posted by roger3829 View Post
    I found it. Check out this link. You only need Pins #1, 2, 3, 6

    http://www.ertyu.org/steven_nikkel/ethernetcables.html
    Correct, but you can get cross talk when using the other pairs for other things.
    The faster your network gear, the more prone you are to failure.

    You also run the risk of equipment damage if a ethernet pair gets shorted to a non-ethernet pair. Not saying don't do, just beware the pitfalls.

  9. #9
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    Quote Originally Posted by roger3829 View Post
    I found it. Check out this link. You only need Pins #1, 2, 3, 6

    http://www.ertyu.org/steven_nikkel/ethernetcables.html
    I learned something new again. Let me ask-- why do we run 8 conductors. Are there ethernet systems that need 8 conductors and some that need 4 or will any system work on 4 conductors. I am a bit confused on this.

  10. #10
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    I believe it has to something to do with parallel transmission. 8 wires equals 8 bits ot transmision, or a "byte" at a time. 4 wires equals 4 bits, a "nibble". Many of our cameras and wireless routers at work run on 12VDC and we use one cat5 cable for transmisssion and power supply. I can provide more info on Monday if you are interested.

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