I have random RJ11 wires in house which have been cut off as they were used for the master socket and the master socket was in an awkward place. And I was wondering if it was possible to convert both ends of that cable into a RJ45 cable to connect to my PS4 from the router saving time and money from having to buy and install a new cable.

Edit: I don't think it's a "cat" cable. It doesn't have any writings at all. It's the cable used in UK for the master socket (BT 5C) to connect it to the phone and router. Not sure if it's different in other countries. Just a thin white cable. Thinner than a standard RJ45 Cable. –

Is this possible?

  • Doubtful, but what is the cable type? Read the printing on the wire jacket look for the word Cat and tell us what number follows that word. – Tyson Aug 19 '18 at 23:42
  • I don't think it's a "cat" cable. It doesn't have any writings at all. It's the cable used in UK for the master socket (BT 5C) to connect it to the phone and router. Not sure if it's different in other countries. Just a thin white cable. Thinner than a standard RJ45 Cable. – TheGreatScorpio Aug 19 '18 at 23:45
  • You might want to edit those details into the question. – Tyson Aug 19 '18 at 23:58
  • Having existing cable makes it much easier to pull new cable so that you can just do it properly. I can tell you right now you’re gonna throw this idea out the window as soon as your video games start glitching in the heat of a battle. – Appleoddity Aug 20 '18 at 4:49
  • As @Appleoddity says, best use of that existing cable is to pull a new cable through. – Baldrickk Aug 20 '18 at 12:59

The answer is possibly... but without knowing more about the cable and the layout it is difficult to tell.

In theory, telephony cable can be used to support 10/100 connections (not Gigabit) over short distances. If you can find a telephony cable that is not cut and is a "home run" between the two points you need to connect, and it contains at least 4 conductors, it may be possible.

For 10/100 Ethernet to work, you need to have a straight through connection of pins 1, 2, 3, and 6, and the other pins are not relevant/not used in this scenario.

For the purposes of this, we will say the cable has Red, Green, Yellow, and Black conductors. They may be different colored or contain more conductors, but this is all we are concerned with. If the cable is solid with a matching stripe (Blue with a white stripe and white with a blue stripe twisted together, even better).

Connect both ends of the cable the same to an RJ45 JACK (do not crimp ends on the cable), essentially we are going to substitute color pairs of the existing cable for "standard" color codes in EIA/TIA 568B color code.

In the 568B color code, we need W/O-O/W (Pins 1&2) and W/G-G/W pairs (Pins 3&6) Pins 4, 5, 7, and 8 can be ignored (they are for PoE and Gigabit applications, which we are not going attempt with this type of cable).

Now substitute... If you cable is Red/Green Yellow/Black, connect the green to Pin 1, the Red to pin 2, the black to pin 3 and the yellow to pin 6, do the same on both ends and connect with a standard patch cable to the router and computer. If the color are different, just substitute as necessary.


Now, the reality this might work perfectly at 100Mbps, or it may error out like crazy... it may function fine at 10Mbps or fail just as miserably... Or it may not link up at all. There is no way of knowing until you try it.

  • If I remember correctly i think had four cables but i might be wrong need to check when i get time tomorrow. – TheGreatScorpio Aug 20 '18 at 0:17
  • nice detailed answer. in reality I have done this and it worked. of course it depends of the state the cables are in. if those cables are there for a long time it might not work. a lot of times bad wires would cause troubles for ADSL routers and low speeds or disconnects. and dont forget it might be a 2 wire cable (the 4P2C ones, against the 4P4C ones). – Zina Aug 20 '18 at 0:19

First, the RJ45 has eight contacts for four pairs of wires. How many wires does the existing telephone cable have? Unless this cable was for a large office, it likely has only four wires, so cannot be used directly for a full-speed conection.

Second, the cable used for plain old telephone service (POTS) was originally designed to carry signals of a few kHz. Digital Subscriber Line (DSL) managed to get speeds of 250 kb/s to (rarely) 100 Mb/s over POTS, but don't expect the full speed your ISP provides over old copper.

There is discussion of POTS to Ethernet adapters. An adapter kit including transmitter, receiver and power supplies is available for ~US$220, which might be worthwhile if you want to connect points a km apart. Planet Technology has a DSL bridge for ~US$120, but you need one at each end of the cable. DSL Warehouse shows a wiring diagram.

So in most cases, it's more economical and more efficient to snake new Cat-6A cable through the walls or dropped ceilings rather than to reuse the old cable for Ethernet. However, if you have land-line service, just reuse the cable for POTS and use a USB modem adapter (~US$20) for 56 kb/s service. A modem is also a handy way to send and receive faxes without using an internet service middleman.


I would not recommend using an RJ11 / phone network cable for your PS4. I am assuming you use it for gaming and video streaming and you would like to enjoy a delay free experience. To achieve a delay free use of your PS4, you will need a proper ethernet network cable installation(CAT5e, CAT6 or CAT6a). These network cables are designed to reach 1GB and 10GB speed. The biggest differences between these cables and telephone cables is the quantity of copper in the cable (the more the better) and the twists between the individual wires. The twists are important because they help cancel electrical noise that is inherent in electrical cables. Phone cables are designed to carry analog signals which is a low bandwidth requirement.

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