Can I convert this funny cable with 4 wires into an ethernet cable for connecting my laptop to the internet?

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The cable currently has a white/yellow banded wire, a white/blue banded wire, an orange wire and a blue wire.

One of the ends is a BT connector and the other end is an RJ11 head with only 2 pins.

  • Unlikely. RJ45/Ethernet cable uses 8 wires in twisted pairs, so you can't just wire those 4 into an RJ45 plug and expect it to work. Even if there where 8 wires, you have to know what sort of signal is on that wire. If there is a DSL signal on that line though, you can typically plug it in a DSL modem and connect your laptop to the modem via ethernet. It really depends on what that line is used for.
    – wysiwyg
    Jun 12, 2017 at 19:18
  • @wysiwyg Does ethernet actually make use of all 8 wires? Jun 12, 2017 at 19:20
  • Technically not always, but I wouldn't recommend it...earlier Ethernet cable specs did not use all 8, but for modern use they are typically used.
    – wysiwyg
    Jun 12, 2017 at 19:28
  • 4
    Just to make that clear: Only Gbit Ethernet uses all 8 wires. 10 and 100 used only 2 pairs, with "split adapters" to make 2 connections on a fully wired wall plug quite the norm until ca. 15 years ago. Jun 12, 2017 at 19:34

3 Answers 3


First of all: Yes you can, but it won't make you happy.

10Mbit/s Ethernet uses 2 pairs and works quite well over short distances with the kind of cable shown, you just need to crimp an RJ45 plug on it (using the pairs 1/2 and 3/6).

Now 10Mbit/s is not very fast, so you might want to go alternative routes. Assuming The idea behind using this cable is avoiding a recabling, you might want to consider Ethernet over powerlines, this works amazingly well in many home settings, the adapters (Devolo and TP-Link have worked for me) are cheap as chips.


As requested in the comments, a few more details about the needed plugs:

Ethernet typically uses RJ45 plugs with 8 pins (1..8) carrying 4 pairs of wires. For historical reasons, these pairs are assigned to the pins this way: 1&2, 3&6, 4&5, 7&8. Older Ethernet connections use only the pairs 1&2 and 3&6.

So for a straight-through cable you need to connect pin 1 of one end with pin 1 on the other side, same with pins 2,3 and 6 and for a cross-over cable you need to connect 1-3, 2-6, 3-1, 6-2.

If the wires in the cable are paired (i.e. always two are twisted together inside the cable's protective mantle) honor this pairing when connecting the cables.

The mechanical process of putting the plug on the cable is called "crimping" and it is easily done with cheap "crimp pliers". If you don't have one, I recommend you just cut a cheap Ethernet patch cable in the middle and solder the two resulting "pigtail" half-cables to the ends of the old cable, using the orange/orange-white and the green/green-white pairs.

  • My internet DLoad speed is only 5Mbps at best, but would having 10Mbit/s connection to router really damage that? Jun 12, 2017 at 19:27
  • Not at all! Routers are typically either 10/100 oer 10/100/1000 compatible Jun 12, 2017 at 19:32
  • 1
    You can successfully run 100 Mbps over this, can't you?
    – user1686
    Jun 12, 2017 at 20:11
  • @theonlygusti Yes, see this Wikipedia article or this
    – wysiwyg
    Jun 12, 2017 at 21:01
  • 2
    @grawity Most likely you can't: While 100Mbit/s uses only 2 pairs as well, the quality of the cable (i.e. its electric, inductive and capacitive properties) will not be good enough. Jun 13, 2017 at 8:07

You should consult your Internet provider as to the proper patch cords to use when connecting to their internet ports.

Where I live, a phone line with an RJ 11 connector goes to a DSL modem and the DSL modem provides the Ethernet socket for an Ethernet cable to go to my laptop. RJ11 type phone lines do not directly connect to Ethernet ports, but of course BT may have different rules.

You can fabricate your own adaptor, but less headaches to find and buy the proper one.

  • I don't understand; what do you think I should do? Jun 13, 2017 at 7:10
  • Talk to your Internet company first and find out what you need, see if they will provide it or go to a electronics shop to get it. Somehow simply patching a four wire line to an Ethernet plug to go into your computer doesn't sound like it will work.
    – Gene
    Jun 13, 2017 at 16:23
  • Sounds like it will work to me... Jun 13, 2017 at 18:53
  • Ok, let us know how it went.
    – Gene
    Jun 13, 2017 at 20:24

I understand that im a little late to this thread, but there is a lot of misinformation on this thread. 2 twisted pairs does not get you 10 mb/s, it gets you 100 mb/s. Distance matters as much as a cat 5 cable would, there both twisted with rubber sheilding. I personally use cat 3 cable (phone cable) with my gaming pc. Cat 5 cable can transfer at a rate of one gigabit while cat 3 can transfer at a rate of 100 megabits. One gigabit=1/3 of a gigabyte while 1 megabit=1/3 of a megabyte. You will get decent speeds through cat 3 cable, which has 2 twisted pairs.


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