questions about cat5

[violaboy]

Two questions:

I know it's proper to follow the color coding guidelines of either the T568A or B, but if you were making a 50 foot cable, would it really matter. A buddy wired (didn't follow code) up a cable the same on both ends, but it wouldn't transmit data, although it would show green leds on the nic and a connected network icon. Just wondering why it wouldn't work. I've heard some of the pairs have less turns than others...true?

The other question is...can someone tell me how each pair is used in transmitting data for T568B. ie...receive, transmit, and how full and half duplex changes the mix. Thanks, and if it's too much to type, just throw me a link to a site.

 

[violaboy]

Let me clarify that question!

Is it electrically important and critical to data transfer that you use pairs/wires 1,2,3,6 ? Could you substitute one of the unused for one of these. Just curious. Also, I just read that 4,5,7,8 are completely wasted, even with full duplex.
"Note that pins 4, 5, 7, and 8 and the blue and brown pairs are not used in either standard. Quite contrary to what you may read elsewhere, these pins and wires are not used or required to implement 100BASE-TX duplexing--they are just plain wasted."

http://www.duxcw.com/digest/Howto/network/cable/cable5.htm

Is this true?

 

[MasterRacker]

Pins 1&2 are pair 2, pins 3&6 are pair 3. As long as each of those sets of pins are connnected as a pair and are polarity correct on each end the other wires don't matter for normal usage in a patch cable. The color codes are just a convention for the numbering of the pairs. The differing twists is to reduce crosstalk between pairs. The link light is just a simple continuity check. If you buddy's cable didn't work it's probably because he didn't wire 1&2 as a pair and 3&6 as a pair.

All that being said, throw the mess away and wire one to code. (Better yet, buy one.)
Jeff
I haven't lost my mind - I know it's backed up on tape somewhere ....

 

[Degg]

Full Duplex means that you can transmit and receive at the same time. Half Duplex means you can only transmit OR receive, but not both at the same time. As far as which wires you use, the colors dont really matter. what matters is what PIN you wire them up to. You must use PINS 1,2,3,6 on your wall jack/RJ-45 connector for it to work. the colors provide a standard to make things more universal.
For normal ethernet, pins 4,5,7,8 are not used. But, some applications do use these pins. For example, if you have a Cisco VOIP (Voice Over IP) Phone, and you want to power it from a switch, then it uses the extra pairs for power. in that case, you need 4 good pairs of wire. I have had cables that work for ethernet, but wont supply power to a VOIP phone because of a bad pair (4,5,7,or 8). Hope this helps.

D

 

[jimbopalmer]

Also gigabit ethernet does use all 4 pair. I tried to remain child-like, all I acheived was childish.

 

[violaboy]

Thanks for all the input. I'm still a little unsure about one thing. Could you substitute one of the unused pairs, say pair 1 or 4 for 2 or 3. I'm just curious if there is a physical difference between the pairs. I'd never do it, I'm just one of those people that always asks why! Thanks everybody.

 

[Degg]

you can use any pair you want, just as long as you use the same pair on both ends. there isnt any real difference to be concerned about, the wires are all the same. The difference is in the twisting, which is mainly for crosstalk between pairs. I have used a single cat5 cable for 2 ethernet connections, 2 pair for each connection and they both work just fine.

D