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ETHERNET CABLES.. are all the cores used?


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#16 Frunple

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Posted 19 March 2012 - 05:08 PM

Lou, "they" are right and you are right except for the part that you are wrong...
Yes, the conductors are the same but there is a difference in the two standards and the twists are correct except they are wrong about the "A" and "B". How could "A" be newer than "B"?? Common sense says A comes before B. So a quick history...
"A" was always the standard, then they came out with a TDR and you can actually see the signal and what crimps and crossovers etc actually do to the signal. That created the "B". The most important aspect of cat5 is the twists. So you have to do anything you can to maintain those twists as far as you can. If you open up a cat5 and lay out the wires so they form an X or a cross, you will see the orange pair will be across from the brown pair and the blue across from the green. This is the reason "B" was adopted. When you form the wires to insert into a RJ45 using the "A" standard you will have to cross the green pair over at least one other pair. Using the "B", you will not have to cross any other pair so none of the wires are crimped and the twists are maintained the farthest they can be.
Of course this is all moot with cat6 cable because now the pairs do not lay the same depending on the manufacturer so none of it matters.

#17 DELInstallations

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Posted 19 March 2012 - 05:16 PM

In addition to the above, part of the standard also has to do with being backwards compatible with USOC wiring (to an extent)

#18 wuench

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Posted 19 March 2012 - 05:51 PM

I believe the actual history of the standards are that a long long time ago some Sasquatch's sat down with some Aliens and they couldn't agree on which standard to use, and their descendents are still arguing about it to this day... :)

Edited by wuench, 19 March 2012 - 06:10 PM.


#19 k2zs

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Posted 19 March 2012 - 06:51 PM

You should always observe the standards as they are used, 568B for net and 568A for telco. While it is only a color change to most users, it reflects standards that are common for communication. In Telco colors, blue blue/white, orange orange/white, green green/white represent standard line numbers where the blue pair is always the primary number, the orange pair is always line 2, and the green pair is reserved for line 3. When a PBX is involved those colors have specific uses as well like line, hunt, park and so on.

As mentioned earlier, with 10/100 Ethernet, all that's required is the orange and green pairs, but if wired as 568A you won't have a connection. That's why you should follow the standards...

As far as POE goes, I've not had many opportunities to work with it other than terminating cameras and some telephone work. In those instances a special router was used that provides an input for your power and the router would inject it into the network. These were gigabit routers so it is possible to have POE over gigabit networks.

As a general rule of thumb, always maintain your twists and keep them within 1/2" from where the jacket has been removed...

#20 wuench

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Posted 19 March 2012 - 07:38 PM

Ok, all kidding aside, If you wire 568A on both ends you will be fine for ethernet too. Including 10/100, 1000. with or without POE. As Lou pointed out, if the colors are ignored, the wiremap will be the same no matter which standard you use. POE will take a pair if it is free (10/100) otherwise the power will piggy back on one of the pairs (1000).

I think if you take anything from this discussion it would be that the T568A vs T568B debate is great to harass wiring installers about... ;) (and use the same thing on both ends no matter which you pick).

Now what's the best routing and trunking protocols?.. :)

Edited by wuench, 19 March 2012 - 07:41 PM.


#21 wuench

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Posted 19 March 2012 - 07:53 PM

Oh and I found this quote on da Net so it must be true... :) This is how B can come before A....

Twelve months later TSB-40 was published addressing higher speed UTP for hardware connecting, this was revised in January of 1994 to include RJ-45 modular jacks and fly leads. At this time EIA/TIA-568 was also revised and renamed EIA/TIA 568A, the existing AT&T standard 258A was included and referred to as EIA/TIA 568B



#22 cenemelectrical

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Posted 19 March 2012 - 10:45 PM

i have always used 568A

so basically i could use brown and brown/white for another purpose?? and still have network functionality..??

The reason why im asking this odd questions is because i have a central area where a security system AND dvr is installed... the owner didnt want remote viewing on the dvr during pre-wire.. but now that the job is complete he wants it... SOOO

i have a delima.. i only have 1 cat-5 running back to central area.( housing the network switch and telephone patch etc etc ) currnetly this cat-5 is being used for the phone line to the alarm...
now i need an ethernet connection there..
so i was thinking i could use the 2 x conductors that are used for the POE and use this as the phone for the security, and the rest for a standard ethernet connection..

any thoughts?

thanks alot

#23 Lou Apo

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Posted 19 March 2012 - 11:14 PM

i have always used 568A

so basically i could use brown and brown/white for another purpose?? and still have network functionality..??

The reason why im asking this odd questions is because i have a central area where a security system AND dvr is installed... the owner didnt want remote viewing on the dvr during pre-wire.. but now that the job is complete he wants it... SOOO

i have a delima.. i only have 1 cat-5 running back to central area.( housing the network switch and telephone patch etc etc ) currnetly this cat-5 is being used for the phone line to the alarm...
now i need an ethernet connection there..
so i was thinking i could use the 2 x conductors that are used for the POE and use this as the phone for the security, and the rest for a standard ethernet connection..

any thoughts?

thanks alot


I have mixed pbx and 10/100 ethernet on the same cat5 without any issues.

POE has 2 different protocols where one combines data and power on the same 2 pair and the other uses the extra 2 pair (10/100). You would presumably use the first style of POE so that the 2 free pair remain. I will not comment on putting regular pots phone line onto cat5 along with data.

#24 Work2Play

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Posted 20 March 2012 - 01:06 AM

I've done the POTS line along side data plenty of times in the earlier days of networking... I used to cheat and use RJ45 splitters - I'd open them up and modify them by cutting the unused pairs out of each side on the side with 2 jacks (cut blue/brown on one side and green/orange on the other, if a 568b jack is used).

And Lou - if you were to just wire a jack with pairs that don't fit the standard, like just going pair by pair (orange white/orange, blue white/blue, green white/green, brown white/brown - for example) - my Fluke tester will fail the cable - it does matter, even at shorter distances - those twists are very important. As others said above, the standard has origins in Telecom so the ethernet standard was designed around this in the way that takes advantage of the twisted pairs. If you're making a 10ft patch cable it'll probably work - maybe not at gigabit; but if you're doing a 100ft run it will fail.

K2ZS - that switch you describe is a special Passive POE switch; it is different from the standard 802.3af POE standard. They're used in security cameras, WISP equipment, etc.

#25 cenemelectrical

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Posted 20 March 2012 - 07:37 AM

so the answer to my question is YES... sweet

now... which cables in the cat-5 can i use? brown and brown/white?

( assuming a 568A standard throughout the house )

#26 ecborgoyn

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Posted 20 March 2012 - 08:03 AM

It sounds like you are installing this for someone else.

I would recommend marking this ethernet connection as 'different' in some manner. Perhaps use a contracting keystone jack color or some other indication. Someday in the future somebody will want to run POE or gigabit over that line and will be confused for a while.

I wouldn't recommend this wiring scheme as good general practice, but it might work in a pinch. (I'm the purist and not the 'hack').

#27 wuench

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Posted 20 March 2012 - 12:07 PM

Yeah, no POE or Gig use the brown. My crappy old network continuity tester doesn't even test/report on the brown pair. :)

Edited by wuench, 20 March 2012 - 12:08 PM.


#28 Frunple

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Posted 20 March 2012 - 05:44 PM

Yeah, no POE or Gig use the brown. My crappy old network continuity tester doesn't even test/report on the brown pair. :)


Gigabit uses all 4 pair.

Edited by Frunple, 20 March 2012 - 05:50 PM.


#29 wuench

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Posted 21 March 2012 - 09:45 AM

Correct, if no gig use the brown. that's what I would do anyway...

Edited by wuench, 21 March 2012 - 09:46 AM.


#30 gatchel

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Posted 21 March 2012 - 03:12 PM

Or just run another cable....CAT5/6 is cheap.




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