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Wiring Telephone Circuits with CAT5 Cable

CAT5 Cable for Home Telephone Installations

Wiring a house for phone, ethernet and CATV/DSS

A great idea... but how do you hook up 4-wire phones to 8-wire CAT5e? Which pairs do you use?

In 2006, I re-wired my 41 year old house with combo cable (sometimes referred to as "smart cable" or "quad cable", the version I used was similar to this: Quad Cable). My grand plan was to pull this cable -- which comes in several versions, but I used one with 2 RG6Q coax cables and 2 CAT5e cables -- to each room in the house, as well as to the garage, my workshop, and possibly even to the back patio. (Ultimately, I wired all the rooms in the house, the workshop and the garage, but never made it to the patio...yet. I'm still hoping to get back up into the attic and finish the job one day.) I used both RG6Q cables for satellite (DirecTV), and then one CAT5e cable for ethernet and the other for telephone.

With that plan in mind, I searched far and wide on the internet to figure out what the 66-block wiring order should be for the 4-wire telephone installation using CAT5 cabling.

I did find it on a couple sites, but only one (Wolfgang S. Rupprecht's "Cat5 To Every Room of the House" page, which no longer seems to be available) had what I thought was a clear graphical representation. On the other hand, that site also had a typo in the color codes -- it showed all the wires in a CAT5 cable being striped, whereas in fact only half of them have stripes, the other half being solid colors. So I'm borrowing the format of Wolfgang Rupprecht's table here, but correcting the color codes on the CAT5 wires. The other difference with my version is that I've tried to make the color coding a bit easier to read than on his page -- just because I need it to be as clear as possible!

So if you've been wondering which CAT5 pairs to use when you hook up a telephone line, here you go... use it in good health.

Pair T/R Telco Ethernet
1st Pair Tip Green White/Blue
Ring Red Blue
2nd Pair Tip Black White/Orange
Ring Yellow Orange
3rd Pair Tip   White/Green
Ring   Green
3rd Pair Tip   White/Brown
Ring   Brown

By the way, and for what it's worth, I've also read on more than one site that mixing ethernet and phone on the same ethernet cable is not recommended. Ringing voltage on the phone line can, in some cases, interrupt the ethernet connection. And, perhaps more importantly, gigabit ethernet needs the spare pairs on the CAT5 cable, so don't put phone on the same cable if you ever want to move to gigabit!


Last updated on Tuesday April 7, 2015 at 11:26 PM CST.