34 replies to this topic

[cenemelectrical]

Hello

when an ethernet cable is in use... are there any of the wires that are not used?? say if i wasnt using Poe i could use those core for another use?

[video321]

when an ethernet cable is in use... are there any of the wires that are not used?

10/100 = yes
1000 = no

[Frunple]

Fast ethernet uses the orange and green pairs or pins 1,2, 3 and 6.
Gigabit ethernet uses all 4.
Not sure what you mean by "core" though?

[Desert_AIP]

Not sure what you mean by "core" though?

He's talking about the "conductors".

[Desert_AIP]

The other pairs are also used for PoE in Fast.

[wuench]

10/100 Brown Pair are not use - Are used for POE though
1000

[gatchel]

Depending on Mode A or Mode B....

Read these....

http://en.wikipedia....iki/TIA/EIA-568

http://en.wikipedia....r_over_Ethernet

[Lou Apo]

Depending on Mode A or Mode B....

Read these....

http://en.wikipedia....iki/TIA/EIA-568

http://en.wikipedia....r_over_Ethernet

Can someone please explain to me why there are two different color schemes. They are the exact same pairing scheme but for some crazy reason there are two competing thoughts as to which colors should be used for which pairs.

[wuench]

If the installation is residential, choose T568A unless other conditions apply (see below). The two inner pairs of 568A are wired the same as a two-line phone jack.

I usually wire 568B myself, because that is what I am most familiar with. But 568A is the recommended residential standard and also Elk's DBH is 568A.

And I am sure you will have some people come in and tell you one is better than the other, 568A is newer I think, but I doubt for anything residential it really makes a difference.

In the end as long as both ends match for Ethernet you are fine. So pick one and be consistent.

Edited by wuench, 19 March 2012 - 01:28 PM.

[Lou Apo]

And I am sure you will have some people come in and tell you one is better than the other

Well, I'm sure you are right, but they would be wrong, unless perhaps it has something to do with confusion or color blindness prevelance in IT technicians. The fact is that the color painted on the wire does not affect the electrons. Provided you keep the pairs matched at their current pinout locations, it is 100% exactly the same to use whatever color you want. In fact, the wires could have no color at all and you could ohm it out to know what goes where.

Edited by Lou Apo, 19 March 2012 - 02:07 PM.

[wuench]

Not giving anyone a head start But the arguments I have heard in the past are that one is better than the other due to the way the wires are twisted within a cable and the various signalling. One is supposedly less prone to interference than the other, I am thinking A because it is newer. But I can't remember. And I am not sure that it is still true now that all wires are in use with gigabit.

There are EE's somewhere that stay awake at night thinking about that kind of stuff....

Edited by wuench, 19 March 2012 - 02:14 PM.

[ecborgoyn]

My $0.02:

Yes, wuench is correct. The justification is based on the structure of the CatX cable. To minimize crosstalk, the twisting 'pitch' of the pairs are different. And the pairs themselves are twisted around one another. There's even some design to assure that the twisting ratio have very large 'common factors'. This is to minimize crosstalk due to harmonics.

I read somewhere that the 568B standard was based on an old AT&T/BellLabs design. And then the standards body improved it with the 568A scheme. Easy to remember the B spec from Bell...

[Lou Apo]

OK, I can buy that, more so with 10/100 since several pairs are just dead and thus the twisting of the pairs around the other pairs could conceivably keep the "live" wires further apart. But gigabit uses all of the wires. Either way, I think you would need some spectacularly expensive equipment to be able to measure any difference.

[ecborgoyn]

I agree. The differences might be noticeable under extreme conditions. (e.g. max cable length, min signal strength, max timing jitter, etc. etc.). I doubt that any residential system would ever notice it.

Pick a standard and be consistent. I chose 568B as my first Cat5 patch panel was labeled as such. At that point in time, most all installation were the B spec as it existed first and was the de-facto standard (If it works for AT&T.....).

[wuench]

I had to add a keypad the other day to the elk and actually had to look up 568A on the net... ugh...