Cat5 Wiring Question

Ok here is my situation i have a residental customer they have CAT5 run in a star formation for their phone system only 2 pair on each cat 5 segment is being used.  The phone system is a business type im assuming digital.  Each segment is run to a phone closet and two pair on each line is punched into a phone punch panel.  Ok so what i would like to do is take the other two pair on each line punch that into a Data rj45 punch panel and then rewire each face plate so that two pair go to the rj11 phone jack and 2 pair goes to the rj45 jack so they have have a data network.  

So my question is will doing this cause problems on either the phone system or data networ since all four pairs are in the same cable.  Can you run both data and phone on the same cat5 segment ?   Take into consideration this house is not dasy chained.  

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With no hard science to back up my statements, I believe it would work but I also believe you will experience lower than normal performance due to interference. The twists in the CAT5 cable are precisely twisted at the right rates to ensure crosstalk cancels itself out. Introducing another signal from a voice network seems certain to distrupt that.

hope this helps.

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You might it get it work, but there is more than likely going to be intermittent issues. I have seen people try to use just the wrong color sequence when making cables and they experienced problems.  Sending the 2 over the same lines is asking for trouble I think.
Hmmmm..... it *might* work. Probably would for 10-BaseT, but I think you'll run into problems at 100-BaseT, and I'm fairly sure you can forget about Gigabit over that sort of arrangement. Something else you can forget about is using standard wire testing gear that expects all 4 pairs to be present - and that will make troubleshooting more difficult.

Frankly, this sort of thing always strikes me as a penny-wise, pound-foolish. The short-term savings in not running a wire plant for data is going to be rapidly lost in lower reliability, greater difficulty in troubleshooting, and limitations (as related to new technologies) as time goes on.

I worked for a place that did almost the exact same thing, except they used Cat3 cable, and it was about 10 or 11 years ago. And it worked fine for 10-BaseT. But when 100 Mb/s technologies came along, guess what? 100-VG AnyLan required 4 pairs. 100-BaseT required Cat5. There was another 100 Mb/s spec that needed all 4 pairs. So guess what? In the late 90s, we ended up ripping out all the Cat3 2-pair data line garbage and running Cat5. If they'd simply run Cat5 to begin with, the viability envelope would have been 10+ years. The Cat3 wire wasn't in there 5 years before we started ripping it out.
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Yes, this will work.  In a few scenarios I have had to do this myself and I have not noticed and serious degredation of signal strength.  The only real trick is making sure your wiring is correct.

However, the times I did this were on very short runs and no real bandwidth by any means was used on any of these "hybrid" lines.

All the points noted above are valid, and in the best case scenario, heed PsiCop.
adproAuthor Commented:
I will never figure out why a builder of an expensive home 800,000+  doesnt run dual cat5 cables to each phone face plate.  But to get new runs in a house this size will cost way more than most people are going to want to pay.  I hate when i go into a residential house and the people that live there tell me ya the builder told us we are wired with cat5 so we shoudl be able to do data.  but Phone is already being used on that cat5.   Well if i did do this i was only going to do 10-bt  since they will only be using it for internet anyways no big file transfer locally.  So do you guys think i shoudl even try it or shoudl i tell them that its not a goo idea?   last thing i woudl want is for them to spend the money to have it done and then for it not to work.

Thanks for all the feedback.

For a home user I wouldn't see there being any noticeable loss for either voice or data.  The times I mentioned above were done in a production environment 10/100.  
The real questions come with the integrity of the system.

Is the system going to be a high end production network?  By all means, no skimping on anything.  Mission critical apps and programs that require bandwidth cannot have a 'weak link' network backbone.  Absolutely do not combine voice and data over the same lines.

Is the system a non-critical network?  Most likely the answer here is what costs the least.  Just make sure the client knows that the system is no longer scalable at all and that by combining the two on one layer the peak performance limits are lowered for each.  And that this is considered the "half a**" way of doing this (no pun intended) and yes, be more tactful :-)

Keep in mind as well that the data punch needs to be as close as possible to the phone punch to minimize the distance of the untwisted pairs have to go to reach it.  The rule of thumb is that you don't want more than 1 inch of your wires to be untwisted (that is impossible in this case... just minimize the distance).
I had a client once that made his own network cables...he didn't realize the importance of using the right order of colored pairs when creating cables...he only though that as long as the order matched on both sides that it would be fine....well all over the network, different users had times where they could barely access network was on and off...but in the end an improperly wired cable will lead to interference and ultimately poor performance...if you can get performance at all.

Since money is obviously an issue, if they are only using the network data internet access, you might want to consider just going wireless.
adproAuthor Commented:
only problem with wireless is the size of the house
repeat the signal with lots of access points or directional antennas...its still gotta be cheaper than re-wiring the house!
The interference loss of the dual use cables for voice/data will still outperform wireless throughput if you are 100base-T.

Perhaps this works as your best cost effective/flexible plan:

**Dual wire your existing endpoints as described above noting the small loss due to cross-talk/interference.
**Run your highspeed internet into the closet and use a wireless router/firewall to connect the data punch panel to the outside world.
**Use a new physical CAT-5 drop to locations of additional wireless AP's as desired.

Now you have them covered with voice/data at each endpoint and can support a wireless signal where desired.


Use the blue pair for telecoms use and leave the brown pair un-connected.  Orange and Green are used for data transmission.
If you don't want to have trouble with your customer you have to give them a stable solution. Using a sigle CAT5 wire to transfer voice and data is something you have to avoid...

If they don't want to invest in cabling, maybe they are interested to invest in IP telehony. You can install a central IP based Communication System and then use a single data line to connect both phones and pc's on each workplace. Most IP phones connect direclty to an existing CAT5 data network and have one more plug to connect the PC to the phone, so you need only one wall jack to connect both the computer and the IP phone to an existing CAT5 network...

Karasardelis Kostas
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