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CAT5 and CAT6 Cable and 568A and 568B standard

Why worry?

WebMux uses gigabit interfaces. To make reliable connections at gigabit speed, the type of cable and connection of cable to the sockets are making differences. WebMux requires to use CAT 6 cables for working reliably in the gigabit speed. To be able to communicate between the WebMux and the switch, both sides need to put logic 1 and 0 on the wire in certain sequence. At gigabit speed, each pair of wire is operating at above 250Mhz, that is four time faster than the TV signales viberates through the air. At that high frequency, the capcacitance of the wire makes big differences. Different wire isolation material also make big differences. How each pair of wire is connected to the RJ45 header is also making differences.

Difference between network cables

cable Category 5 Category 5E
Category 6
Category 7
Specified frequency range 1-100 MHz <=100 MHz >=250 MHz >=600 MHz
Attenuation at 100MHz 24 dB 24 dB 21.7 dB 20.8 dB
Attenuation at 250MHz 54 dB 44 dB 36 dB 30.8 dB
Wire Gauge 24 24 22-24 22
Delay skew 50 nsec 50 nsec 50 nsec 20 nsec
Designed Speed 100BT 100BT/
GigaBT 10GT
Brand A 47.1 dB 40.1 dB 35.9 dB 32.1 dB
Brand B N/A* 37.1 dB 30.1 dB 29.1 dB

568A and 568B wirings

The 568 committee (part of Electronic Industries Alliance - EIA) decided to allow both wiring schemes (568A & 568B) to exist within the TIA/EIA-568-B Standard. The reason was that at the time, many of cabling plants had been installed to the B standard (formerly known as WECO or AT&T 258A). Even though they allowed both wiring schemes, TIA/EIA-568-B.1-2001 stated in their standard that 568A wiring would be the preferred method for all new installations. The United States National Communication Systems Federal Telecommunications Recommendations do not recognize T568B. Having both A & B methods does nothing but cause errors and confusion. Luckily, today, almost all RJ45 (also known as 8P8C) jacks and patch panels show diagrams for both A and B. The only difference between the two is the interchanging of the 2nd and 3rd pairs (white/orange and white/green, respectively).

Luckily, cables make based on 568A and 568B schemes are exchangeable. Look the picture for those two RJ45 headers:


Pair # Wire
1 - Blue Blue
2 - Orange Orange
  Orange White
3 - Green Green
4 - Brown Brown

From the chart above, you can see the pair one is always at center. The wiring schemes between the 568A and 568B are only swapped the pair of green/green-white and orange/orange-white. Each pair maintains as a pair is very important, but replace one pair's color with another pair's color does not actually has any difference in electrical characters. Please note in each pair, one wire is for transimitting, one wire is for receiving. Pair one is always at center with reversed T and R, and pair two surrounds pair one. Pair three is on the left hand side, and pair four on the right hand side. From left to the right, you will see one T alternated with one R. Gigabit network cable uses all four pairs. Any one wire in any pair not follow the pair order will cause WebMux not making reliable connections to the switches.

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