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Splitting Cat5 Cable

Posted on 2006-11-16
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Last Modified: 2013-11-09
Are there any disadvantages of splitting a cat5 cable run?
Also how many splits can you get out of one cable?


Thanks Guys,


Derek
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Question by:derekruf
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10 Comments
 
LVL 8

Expert Comment

by:saw830
ID: 17961341
Hi derekruf,

Are you asking how many circuits you can get from a cat5 cable run?  Depends on what you are planning to do with them.  There are 4 pairs of wires in the cable.  10baseT uses 2 pair.  Ordinary telephone circuits use 1 pair.  So, you could do 2 LAN connections, or 4 telephone connections, or 1 LAN and 2 telephone connections....

Hope this helps,
Alan
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LVL 77

Expert Comment

by:Rob Williams
ID: 17961362
Do you mean splitting the physical cable for 2 connections, or splicing it? Do not !!!!  You will get terrible "cross talk" resulting in poor performance or no connection at all.

You can install a switch or hub to "split" the connection to multiple systems.
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Expert Comment

by:saw830
ID: 17961367
derekruf,
oops... missed the first part.....

disadvantages?  not really, as long as the interconnects are done properly.
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Author Comment

by:derekruf
ID: 17961395
I would use a switch but I need dedicated lines from my patch panel. Basically Can I take one Cat5 Run and patch that into my panel over 4 ports for example and on the other end have 4 ports to plug into.
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Accepted Solution

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Rob Williams earned 75 total points
ID: 17961428
Do you mean split the wires to punch down on 4 different ports?
Firstly 10/100 Ethernet uses 2 pairs and Gigabit uses 4 pairs, so you couldn't get 4.  But, CAT5 wiring is unlike phone wiring, and has to be treated vary carefully and according to spec. It requires the jacket and twist of the wires/pairs be maintained right to the jack. Not following this, allows for "cross-talk" between the pairs. Though a continuity tester will show no problem, and you may actually get a connection, a proper CAT5 certification meter will show the drastic reduction in performance.
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LVL 79

Assisted Solution

by:lrmoore
lrmoore earned 50 total points
ID: 17961432
No. Ethernet uses 2 pairs. The best you can get is 2 runs per cat5 cable.
This violates all standards, and will not guarantee you anything more than 10Mb Ethernet .
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LVL 8

Expert Comment

by:saw830
ID: 17961527
You'll need one for each end of the split.

Here's an example of what you need if you want to buy them:
http://www.hubbellpremisewiring.com/catalog/model_BR851D.htm

Here's how to "roll your own":
http://www.duxcw.com/yabbse/index.php?board=2;action=display;threadid=18740
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LVL 77

Expert Comment

by:Rob Williams
ID: 17961585
Thanks derekruf

@ saw830
These Hubble adapters and their male to male adapters looked to me to be "the cat's meow" a few years ago, but I had a client having problems, so I tested the cabling with one of the male to male adapters and it failed completely. I think the problem is, within the unit they have 8 parallel bare, connections, which generates incredible cross talk and 'noise'.

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Expert Comment

by:saw830
ID: 17961704
RobWill,

I haven't used that particular brand, and if that is how they are built, then they would have a problem.  Most of the ones that I've used were made up of a male rj45 on a short pigtail going to a little box (about half the size of a cigarette pack) with two female rj45 jacks in it.  I've never had a problem, and believe that if everything is done correctly (to spec), the splits will conform to spec as well.  The spec allows for interconnects, and the splitter is really nothing more than an interconnect.  The spec also provides for twists per inch in the pairs, and the amount that is allowed to not be twisted.  This is probably where the Hubble devices have the problem.

I don't think that being bare is the problem, but the fact that they are parallel for too long of a span, allowing capacitive and inductive interferrence from the adjacent conductors.  I'm not saying that the insulation of CATx cable is trivial, it isn't.  The make up of the insulation affects the capacitive characteristics of the cable, but for the short distance transitioning to, and being inside of a connector, it just isn't enough to make a difference.

In short, I agree with you, but in long, I've not had a problem with any I've used.
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LVL 77

Expert Comment

by:Rob Williams
ID: 17961759
saw830, I can see where the ones with the "short pigtail" would be much better. I think there is a major design flaw in the Hubble units, which is why I was pointing it out.
I'm sure the others probably work, however I purchased a CAT5 certification tester for >$5000 a few years ago, it was a great learning experience for me. Just because devices connect and can communicate, does not mean they are doing so efficiently. I have become much fussier after troubleshooting many wiring issues.
Cheers !
--Rob
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