Is it possible to place a switch in one of the four/five wires of an Ethernet cable that will disable it?

For my hardware project I would like the user to be able to disable the internet connection at the flick of a switch!


  • I am aware that it will affect the speed and signal quality but with the hardware I am using it shouldn't matter.
  • I know there are commercial options available on the market, but at $50 and in a bulky branded box they are not suitable for my project!

Is this possible?

  • 3
    One wire won't necessarily break connectivity. You need to disconnect all 8 wires. (ie. an 8 poll switch)
    – Ricky
    Mar 16, 2015 at 23:13
  • I've actually seen a wall plate with a keyed lock to securely and physically disconnect the attached device from the network. I can't seem to find it online though...
    – cpt_fink
    Mar 17, 2015 at 3:30

4 Answers 4


Have you got a physical switch that is rated for Cat5 cabling? The answer to your question is the same as the answer to my question.

More than likely you need to buy:

  • An ethernet optical isolator / optocoupler and drop the power to the isolator
  • An ethernet relay rated for Cat5e or higher
  • Do you know where I would get one of those?
    – JBithell
    Mar 20, 2015 at 17:46
  • 2
    Run the connection through a powered 4 port unmanaged network switch, and kill the power to that instead.... May 23, 2015 at 20:08
  • @TomO'Connor the boot time for a switch is much slower than the sigal rise / fall time for an electronic relay. Jan 24 at 12:11

Partially serious, partially making light of the question, you could try a 4 pole, 2 throw (4PDT) switch like this one on Amazon and solder the switch in place in one of the wires in each pair.

In all seriousness though, Mike Pennington has the best solution with a button connected to a relay. Add a few RJ-45 jacks and the aforementioned items to a project box, and you've got a nice little physical network kill switch.

Edit: Had poles and throws mixed up. Updated Amazon link accordingly. Added edit edit.


Check out the cabling for Ethernet of twisted pair. If you're using 1000BASE-T (1 gig ethernet) then all four pairs are used for communication, so technically killing one pair would disable 1GE communication. However 10BASE-T or 100BASE-T (10/100mb ethernet) only require two pairs for communication, which could lead to a situation of you killing the wrong pair.

There are 8 wires, configured in 4 pairs.

  • I believe my answer mentioned that 1ge required all 4 pairs and 10/100 only required two pairs. I'll admit and update my answer, but your downvote also assumes that the said devices can downgrade to 1GE.
    – Robert
    Mar 16, 2015 at 20:01
  • Thats what happened to me. I build a kill switch that cuts the orange wire. That worked fine until I upgraded to 1000BASE-T and higher. Now when I cut orange, the connection is disabled for 20sec, then the auto negotiation from both endpoint of the cable kicks in, detect the broken orange wire and uses the other wires for communication. (which is only 10mbit or 100mbit though)
    – John Smith
    Oct 25, 2018 at 14:00

A four Pole Single Throw or 4 Pole Double Throw (4PST or 4PDT) will work to disable any ethernet. Be sure to switch one wire in each pair, preferably the white with colored stripe. Here is a $3.55 switch that fits the bill. http://www.ebay.com/itm/1-MINI-TRAIN-TOGGLE-4PDT-4P2T-ON-ON-4-POLE-SWITCH-125-V-/380289420533?pt=LH_DefaultDomain_0&hash=item588b040cf5

Since this is a '2 Throw' or'DT' you could even wire another ethernet network to the unused poles to connect up to.

  • 2
    Ethernet requires much more than electrical connectivity to work; I seriously doubt that switches will do the job reliably Mar 19, 2015 at 0:18

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