Y-splitter + UTP = would Ethernet work?

Discussion in 'NZ Computing' started by Lawrence D'Oliveiro, Feb 27, 2009.

  1. Running a bit short of Ethernet ports yesterday, my client held up a Y-
    splitter, of the type used to connect both handsets and modems to the same
    phone line, and asked if that would work for connecting two UTP Ethernet
    cables into one port. I immediately said no.

    But, thinking about it, the original design of Ethernet was specifically to
    deal with collisions caused by multiple devices trying to talk on the same
    wire at the same time. So would it in fact work?
    Lawrence D'Oliveiro, Feb 27, 2009
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  2. Lawrence D'Oliveiro

    Tony in Oz Guest

    I had the same question asked of me last week, but in relation to 2
    Ethernet cables going into a single port DSL router to enable Engin VOIP
    router to be attached. I said I had never seen an ethernet double adapter,
    and I wouldn't think it would work, which is possibly why I have never seen
    one. Does anyone know of such a thing, and would it in fact work? My
    experience and knowledge of VOIP devices is extremely limited, I get the
    impression the whole technology is still in its infancy. The Engin deal
    seems to be you pay 9;95 a month for unlimited VOIP calls, but you need the
    Engin router to plug in to your DSL router. You then also need to plug in
    the Network card in the computer, thusly needing at least a 2 port DSL
    router. cheers T.
    Tony in Oz, Feb 28, 2009
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  3. Lawrence D'Oliveiro

    SteveM Guest

    You can get splitters to enable 2 devices to share the same run of network
    cabling from an outlet back to the patch panel.

    They come in different configurations:
    etc etc.

    Only thing is Gigabit ethernet will not work as is requires all 4 pairs of
    wires as opposed to 10/100 which only uses 2 pair (leaving the other two
    pair for other devices)

    These do not work in the way your client suggests. One ethernet port, one
    wire only.

    SteveM, Feb 28, 2009
  4. Wouldn't a 4-wire splitter work for that?

    In any case, we can still get 100Mb through a 2-wire splitter?

    Thanks for the info.
    Lawrence D'Oliveiro, Feb 28, 2009
  5. Lawrence D'Oliveiro

    SteveM Guest

    Collisions are delt with inside the switch/hub not on the wire between the
    device and the switch.
    (You're thinking of the old Co-ax style networking)

    SteveM, Feb 28, 2009
  6. Lawrence D'Oliveiro

    SteveM Guest

    SteveM, Feb 28, 2009
  7. Lawrence D'Oliveiro, Feb 28, 2009
  8. But isn't the logic for dealing with that still implemented in the NIC?
    After all, hubs can't deal with collisions.
    Lawrence D'Oliveiro, Feb 28, 2009
  9. Sorry, there are in fact 4 wires in the lower part. So shouldn't that work
    for gigabit Ethernet, then?
    Lawrence D'Oliveiro, Feb 28, 2009
  10. Lawrence D'Oliveiro

    Gordon Guest

    Back in those days, data piddled along, now they have to scream along to get
    all that data shifted.

    Why not use a hub? Seems like the bean counter is being listened to
    Gordon, Feb 28, 2009
  11. Lawrence D'Oliveiro

    oneofus Guest

    I doubt it, there are issues of impedance mismatch on twisted pair that
    are harder to resolve than with coax to sum the voltages, and with coax
    the t points are at the transceivers with a set termination resistance.
    also its not bidirectional anymore, there is a transmit and receive pair

    The splitter you describe splits the four pairs into two lots of two
    pairs, they are useful for putting two data connections or phone and
    data or two phone connections from a comms rack to a data outlet
    oneofus, Feb 28, 2009
  12. The electrical interface does not work with two devices connected on
    UTP. They use point-to-point drivers, not the old multidrop system.
    So, if you want to use more than one ethernet device on one port, you
    will need a hub or switch. A 10/100 switch is pretty cheap now, and
    there are not too expensive gigabit ones too.
    Stephen Worthington, Feb 28, 2009
  13. Lawrence D'Oliveiro

    SteveM Guest

    You are getting 4 pair and 4 wire mixed up. Gigabit uses all 8 wires (or 4
    pairs) Using splitters will force the NIC into 10/100 mode.

    SteveM, Feb 28, 2009
  14. OK, that makes some sense. Thanks to all who replied.
    Lawrence D'Oliveiro, Feb 28, 2009
  15. Lawrence D'Oliveiro

    Richard Guest

    Yes, thats the half duplex mode used when connected to a hub.

    Totally pointless on a switched network.
    Richard, Feb 28, 2009
  16. Lawrence D'Oliveiro

    Enkidu Guest

    I wouldn't have thought so. The eight wires coming into the wall plug
    will have to reduce to four in the cable.


    Enkidu, Feb 28, 2009
  17. Lawrence D'Oliveiro

    PeeCee Guest

    That's coax based LAN's where all cards can access the same wire.
    8 wire (eg Cat 5) has a strictly one to one relationship i.e. NIC to Hub, or
    NIC to Switch.
    The Hub or Switch does all the data collision and switching management in

    However you can get two 10/100 Mbit LAN connections over Cat 5 (& 5E) by
    using the 'correct' Y splitter.

    A normal 10/100 Mbit LAN adaptor (NIC) only uses 4 of the 8 wires in a Cat 5
    cable, specifically pins 1,2,3 and 6 of a RJ45 plug.
    1 & 2 is pair one, 3 & 6 are pair two (Green & Orange pairs), wires 4, 5, 7
    & 8 are left doing nothing (Blue and Brown pairs).
    By connecting another socket to those 4 spare wires you can get another
    10/100 Mbit circuit over the same cable.

    The trick is to wire the spare wires to the pins on the socket the card
    would normally use vis:
    Connect pins 1,2,3,&6 on 'both' sockets (lets call them socket A and socket
    B), the plug end is wired with 1,2,3 & 6 to socket A, the other socket (B)
    is connected to wires 4,5,7,& 8.

    eg imagine a Y connector at each end of a normal in wall Cat5 cable:

    Socket A
    pin 1 - wire 1 - pin 1 Green/white
    pin 2 - wire 2 - pin 2 Green
    pin 3 - wire 3 - pin 3 Orange/white
    pin 6 - wire 6 - pin 6 Orange

    Socket B
    pin 1 - wire 4 - pin 1 Blue
    pin 2 - wire 5 - pin 2 Blue/white
    pin 3 - wire 7 - pin 3 Brown/white
    pin 6 - wire 8 - pin 6 Brown

    These splitters should be available at your local electrical shop, just be
    sure you get the Ethernet/Ethernet ones and not the Ethernet / Phone ones.

    As others have pointed out you can not do this trick however with Gigabit as
    their NIC's use all 8 wires (4 pairs)

    PeeCee, Mar 1, 2009
  18. That can't be entirely true. The switch never knows when a NIC is going to
    transmit, and vice versa. So they still have to deal with some collisions.
    Lawrence D'Oliveiro, Mar 1, 2009
  19. Lawrence D'Oliveiro

    Richard Guest

    Switches will never see collisions since they are full duplex and
    operate each port independently.

    Old style repeater hubs will, but when a 8 port switch is 20 bucks, I
    can see no reason to use a repeater hub.
    Richard, Mar 1, 2009
  20. Lawrence D'Oliveiro

    Cable Splitting

    Jun 4, 2014
    Likes Received:
    Ethernet Cable Splitter works like a charme

    Cable Splitting is a great simple solution if you just need that one extra ethernet line.

    Se how at


    Fully functional 100 Mb/s LAN connection 100% guaranteed.
    Cable Splitting, Jun 4, 2014
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