I'm experiencing some noise on my phone when it is connected in the wall. There's no noise when connected right in the modem. So I decided to check things out and I noticed something that seems odd to me. My telephone jack uses 2, yes two, Ethernet Cat 5 cables.

Telephone Plug
(source: max-worlds.net)

As you can see, both blue wires are connected to red wire on the telephone jack and both white/blue wires are connected to the green wire. It seems like an odd setup to me. This is a new house. On a side note, I'm thinking they could have done that to allow an Ethernet network, but we already have a Cat 6 network going on...

So I'm wondering if this is a frequent practice, a recommended approach or a bad job.

  • 1
    ANSI TIA/EIA-568 Category 5 Telecommunications Cable. Developed for phone/data communications and adopted as the transmission medium of choice for UTP Ethernet as it carried a signal better than Category 4. What you're seeing is not two phone cables, but a single one stripped out so one twisted pair can be used in a daisy-chain loop. Common practice. Dec 19, 2012 at 19:10
  • Cat 5/6/etc are originally intended as generic cables. Ethernet just happened to use them. Using them for other purposes than Ethernet is perfectly fine. Jul 13, 2022 at 12:59

1 Answer 1


Probably you have two or more phone jacks daisy-chained together. One cable goes to wherever the phone line enters the house and the other runs to another phone jack somewhere else in the house.

This is a common practice. I did some pricing online, and it seems that Cat 5e is comparable in price to 4-conductor phone cable, so the builders may simply have used it because they had it to hand.

  • 1
    You beat me to this answer. It should be noted that this was common practice for wiring phone lines in the past.
    – Craig
    Dec 19, 2012 at 17:42
  • 2
    It still is pretty common. There is no need for analog phone lines to be run in a home-run config, it is cheaper to daisy chain since you use less cable.... and most builders are cheap!
    – Steven
    Dec 19, 2012 at 17:57
  • 1
    Thanks, it makes sense. I dug up a photo of my house under construction and there's indeed a cable going to my basement and one going to my room upstairs. I will leave that as is. Thanks again! Dec 19, 2012 at 18:06
  • @Steven Hey, so I am trying to add an RJ45 port to the wall plate that was previously RJ11 (daisy-chained). How do you punch down multiple wires if you are using a modern keystone port that doesn't have screws?
    – Cfomodz
    Sep 10, 2021 at 6:57

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.