wiring ethernet with < 8 conductors

[eljefino]

Have some cat 5e running into my computer room from the router in the basement. Want to add a phone line. Understand ethernet will run on fewer than 8 twisted strands, want to "borrow" two. Looking for wiring diagrams, having a hard time. Using leviton punch block jacks so I can separate a twisted pair pretty easily. Forget if I did 568A or B but I just "kept my story straight" throughout.

Will be difficult to run more wire though I understand from an interference standpoint might be more ideal.

EDIT: Looks like I'll be playing with 100base-TX.

 

[djb]

An analog phone is usually run on the blue/white pair. These are always wired to the middle pair (pins 4&5) on an 8 pin connector.

If you are running 10baseT or 100baseTx, the signals are sent on the orange/white and brown/white pairs.

The intent was that you could plug either an Ethernet device or a standard 6P4C phone plug into structured wiring and have it work. It's far better to use two separate jacks, and don't use maximum length runs.

Gigabit Ethernet and above use all four pairs, so don't upgrade the equipment.

 

[Quest]

Well, theoretically speaking, you can run your ethernet 100b-t with just 4 wires (2pairs) and get the job done (just like cat-3 cables).

Howeveer, you cannot go very far for you do not get the proper twists for noise immunity, and also the jacks aren't standard in ethernet anyways.

Bottomline: if I were you and have a strong/powerful wireless router such as WRT54GL or similar, I would rather resort to making it wireless instead of retro'ing a phone jack into ethernet.

Q.

 

[brianl703]

100baseT ethernet uses the green and orange pairs.

You can mix 100baseT ethernet and analog phone on the same cable (using the brown or blue pairs for analog phone) with no problem. I've done it many times. Those who say it cannot be done ought to visit the IEEE website, download the 802.3 specs (they're free), and get educated.

To do what you want, wire a jack on both sides to either 568A or 568B (your choice; make it the same on both sides), using only the green and orange pairs.

The blue and/or brown pairs can then be connected to an analog line.

 

[Kiwi_ME]

I have a CAT5E with shared 100baseT and phone line running over some 60 yards with no problem.

 

[PandaBear]

I can vouch for the lack of twist causing noise to be a speed issue. 10 years ago I bought a cable off some kid from the internet because my dad wants grey cable rather than blue to wire the house. That guy send me a cable that wasn't twisted right and thus amplified the noise rather than cancel out the noise. It was fine running 10mbps rather than 100mpbs, until I read about the problem and have to re-crimp the connector to use the right twist.

 

[brianl703]

It sounds like what you had is a split pair. That will cause problems for analog phone lines too. It causes excessive crosstalk.

I've fixed a few network wiring jobs that were done incorrectly, pairs were split, and it didn't work at 100mpbs. After correcting the split pairs, the problem was fixed.

 

[eljefino]

Well I wound up rethinking and used a wholly abandoned ethernet cable going to another room. Wired up the blue pair and stuck an RJ11 into the RJ45. This is for my magicjack line.

Gizmo initially seems promising.

 

[brianl703]

If you ever use that RJ45 for Ethernet again, you'll want to bend up the two pins that the RJ11 plug has pushed down.