I'm renting an older house that was renovated a few years ago, and I'm hoping to utilize the cat5 wiring in the house for networking.

Here's the setup:

internet --> coax --> modem --> wireless router --> wireless devices
                                                --> ethernet output --> RJ45 wall jack
.... in another room....
RJ45 wall jack --> PC

For now, I'm just trying to connect the RJ45 jack connected to the router to the RJ45 jack connected to my PC. In theory I think this just means I need to splice the correct two cables together at our network "closet". Here's what the "closet" looks like: zoom in on wires

(Yes, they are just stapled to a piece of plywood in the basement.) The yellow wires are cat5e, but appeared to be wired into some sort of phone jack block, with an RJ11 socket on the side.

Can any networking experts tell me:

  1. What is the beige box?

  2. What happens if I disconnect the yellow wires from the beige box? We're not using the landlines at all, though a phone in the kitchen is wired to the doorbell and an intercom system.

  3. What's the best way to splice the ends of the yellow wires together? Will it just work as one continuous wire if I do so? (Total cable length is definitely less than 50m, this is a small house.)

Thanks so much for your help!

  • 4
    First off, you should get the ok from the owner/manager before you go making changes to the network. I just networked my entire home before putting it up for rent and I'd sure want to know and be more than willing to help the tenants out. Second, how many devices do you ultimately want hard wired in various rooms? I know you say one for now, but you'll want to do things a bit differently if there's a chance for more...
    – Paul
    Jul 15, 2014 at 16:27
  • The 5 lower beige wires are also cat5, no?
    – Paul
    Jul 15, 2014 at 16:37
  • 1
    The top most beige cable is cat3 with two phone lines. The red and green wires are line one, black and yellow are line two. All the other beige cables may be cat5, though are used only for a single phone line. The yellow cables are also cat5, and are also used for a single phone line.
    – Tester101
    Jul 15, 2014 at 19:20

3 Answers 3


The yellow cables are probably Cat5e, which has 4 pairs of wires. (The beige cables are probably Cat 3, which might only have 2 pairs of wire). A single phone line only requires 1 pair, so as you can see the other pairs are just twisted off.

You definitely can reuse the cable for ethernet access, but you will lose the phone jack obviously.

Here are some things you should know about working with ethernet cabling:

  • Unlike phones with are relatively low-bandwidth, ethernet cables need to be in good condition with the pairs twisted around each other properly and with properly terminated connections. The mess you show is fine for phones but will cause lots of interference with ethernet data. If you want to reuse the cabling for data you need to cut back the cable all the way to the yellow sheathing and start over with new CAT 5e terminations. The proper way to do it is to terminate all the cables at a patch panel, but you could also just crimp a regular RJ-45 on the end and connect them that way. You cannot just twist the wires together and expect to get a good signal. Also, at the other end of the cable (in the room with the jacks), you will need to do the same thing: cut back the cable to where it's clean, and start over with new RJ-45 jacks.
  • Also unlike phones (and household electricity), you cannot split a cable into 2 cables just by joining the same color wires. If you have more than two devices you want to connect, you need to use an ethernet switch, which is a small appliance that will properly route the data packets between 2 or more devices.
  • The yellow cables are cat5. The top most beige cable is cat3. The 5 other beige cables are cat5.
    – Tester101
    Jul 15, 2014 at 19:14
  • 1
    @Tester101: you might be right, although without looking at the markings on the side of the cable it's really hard to tell. CAT 3 can have 2, 3, or 4 pairs. "CAT 5" and "CAT 5e" are often used interchangeably to mean CAT 5e, but some old buildings do have real CAT 5, which is not capable of gigabit ethernet.
    – Hank
    Jul 15, 2014 at 19:34
  • I think you might be right. Looking at the twist of the pairs, it does appear that the beige cables may be 4 pair CAT-3 or CAT-5 (not CAT-5e).
    – Tester101
    Jul 17, 2014 at 12:13

It looks like the owner has set up the entire house for phone using only one pair of wires from each cat5 cable, which is fine. I like the plywood switchboard. It's very configurable if not pretty. And it's tidy, so I expect you'll hear about it if you monkey around with it too much.

  1. Those beige boxes are RJ11 jacks just like you said. It looks like they are being used as splices/spitters however.
  2. Disconnecting any of the cat5 cables (of which I think you have 11) will disconnect phone line to the room the cable serves.
  3. use a cat5e Junction box. You won't need any special tools or hardware like a crimper or a hub, but you'll be limited to just one device. Otherwise, do what Michael says.

You'll also need one of these jacks (I know Home Depot has them) for the room where your computer is. Usually you put a box in the sheetrock and get the appropriate cover plate for these, but I don't know how the cable is run to the room. Again, no special tools needed to install it save the little plastic push tool that comes with it.


The beige boxes are standard surface mount telephone jacks. Disconnecting them will disable the phone jacks in the house (which you say you mostly aren't using).

The easiest way to splice the ends would be to Terminate the ends with an RJ-45 connector, and then use a coupler to connect the two wires.

If you are trying to connect more than two of the cables, then you can use a simple network hub, switch or router to connect all the cables you need.

  • You should use a switch to connect multiple network cables together, not a hub.
    – Tester101
    Jul 15, 2014 at 19:12
  • @Tester101 I was suggesting a hub due to the fact that they can be found cheap, with no power requirements, but it's good to mention it, so I'll update my answer. Jul 15, 2014 at 19:37

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