Sharing Ethernet and Phone on the same CAT5 Cable

When we built our house 4 years ago, the builder installed a central wiring panel. Every room has a Cat5 jack in it that terminates back to a 110 block in this panel. However, they only ran 1 cable to each room, and it's only delivering standard phone. At the time, I didn't see a real need to pay a whole lot of extra money for a separate cable to support ethernet, when I could just setup a wireless router.

Then I got a job working from home, which included a VoIP phone. My office is upstairs and all my network gear is downstairs. So I initially installed DD-WRT on an extra Linksys Wireless Router and turned it into an Ethernet to Wireless Bridge and connected my VoIP phone to that. However, I started to experience issues with QoS using this setup that I never could really seem to resolve. So, I started looking at ways to get this phone on a wired connection. Obviously, I could move my DSL Modem and Router upstairs into the office, but I have other equipment downstairs that's connected to it. So what to do?

Well, knowing a few things about Ethernet and phones, it dawned on me that I could actually mix phone and Ethernet on a sinlge Cat5 cable. Standard Ethernet only uses 2 pairs out of the 4 available. That leaves 2 "extra" pairs. So, here's how I've re-wired everything to allow for a single Ethernet and 2 phone lines in every room now.

On a standard RJ45 connector, Ethernet only uses pins 1,2,4, and 5. I bought a small patch block from Fry's electronics and terminated each fo the cables from each room on the block. Then on the other side of the block I made a custom cable that only connected to pins 1,2,4,5 on the block, and an RJ45 on the other end that I plugged into a small Linksys switch, which fit nicely into the panel. Luckily the panel included an outlet for power to the switch. The remaining pins (3,6,7,and 8) I patched to the 110 block where my phone service comes in.

In order for this to work though, each jack in the house must also be rewired. Plugging an ethernet cable into the jack and connecting it to the PC could be dangerous to the PC. You've now got phone signal coming into the ethernet jack, and sending a 90 volt ringing signal into your PC is probably not a good thing. All I had to do was to split the pairs out again on the jack into 2 jacks - one for phone and one for ethernet.

I've now got 1 Ethernet and 1 Phone jack in each room, and it seems to be working really well. I was actually a bit concerned that I might get some interference from the ethernet signals and the DSL coming on on my phone line, but it all seems to be working really well.