Wiring – Help connecting cat5e cables for home networking

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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!

Best Answer

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.
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