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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

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.

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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. – Fiasco Labs Dec 19 '12 at 19:10
up vote 11 down vote accepted

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.

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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 '12 at 17:42
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 '12 at 17:57
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! – Maxime Morin Dec 19 '12 at 18:06

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