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Why was 568a / 568b developed and why didnt they just do it alphabetically eg blue, blue white, brown, brown white, green, green white, orange, orange white.
I understand that according to structured cabling standards you have to use 568a / 568b but the cable will still work what ever you do, as long as its the same on both ends (unless you intentionally want a cross over cable)
sam
Posted 2016-10-04T11:14:47.720
Reputation: 3 411
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UTP cables used in the 586 standard inherited their colors from the 25 pair color code developed by AT&T for cabling used in telecommunication purposes.
The following table shows the combination of colors to be used for each pair
This gives us these combinations:
UTP cabling simply used the first four combinations of twisted pairs.
The order used in 586a is compatible with 1-pair and 2-pair Universal Service Order Codes (USOC) pinouts that are a requirement in federal contracts by the U.S. government.
Pair 1 connects to the center pins (4 and 5) of the connector. It gives compatibility with the first line of RJ11, RJ14, RJ25, and RJ61 connectors that all have the first pair in the center pins of these connectors.
The position of the other wires is because signal shielding would be optimized by alternating the "live" and "earthy" pins of each pair. However it isn't possible because the outermost pair would be too far to meet the electrical echo requirements of high-speed LAN protocols. That's why only one pair is "untwisted" and used as a shielding for the central pair.
jcbermu
Posted 2016-10-04T11:14:47.720
Reputation: 15 868
Because someone thought it's cooler. You'd probably have to ask one of the original authors to get a real answer. Aside from that there might be some "common" coding used in other cabling standards in regards to ground etc. Otherwise you're correct it doesn't matter as long as you match both ends in the same way (for straight). – Seth – 2016-10-04T11:21:57.377
1because you can unplug a strand of cable, flip it upside down, and look at the colors through the clear connector to see what kind of cable it was (patch, crosspatch, etc). – Frank Thomas – 2016-10-04T11:56:07.120
2"Alphabetically" is language-dependent. – a CVn – 2016-10-04T12:13:45.333