TIA/EIA 568 A vs. B

On Sunday, November 13, 2022 at 3:21:30 PM UTC-4, John Walliker wrote:
> On Sunday, 13 November 2022 at 14:49:18 UTC, lang...@fonz.dk wrote: 
> > søndag den 13. november 2022 kl. 05.23.57 UTC+1 skrev Ricky: 
> > > On Saturday, November 12, 2022 at 11:09:42 PM UTC-4, Cydrome Leader wrote: 
> > > > Ricky <gnuarm.del...@gmail.com> wrote: 
> > > > > On Saturday, November 5, 2022 at 6:42:11 AM UTC-4, Don Y wrote: 
> > > > >> On 11/4/2022 11:24 PM, whit3rd wrote: 
> > > > >> > All 'normal' patch cables are 568B, so that's the only spec I'd ever want to use. 
> > > > >> +42 
> > > > >> 
> > > > >> You also want to be sure to be buying connector terminations that carry the 
> > > > >> matching color code, lest folks get even MORE confused. 
> > > > > 
> > > > > Confused about what??? The color of the wires in the cable are totally irrelevant to anything done using cables with RJ-45 connectors on each end. What is important is that the cable be straight through if that's what you need, or crossover, if that's what you need. I will never see the colors in the cables. 
> > > > > 
> > > > > 
> > > > >> > POE, I'm not sure of. 
> > > > >> When power is delivered over the data pairs (Orange/Green), polarity is 
> > > > >> important. So, you want to know whether you've adopted 568A or B. 
> > > > >> Unless you are always probing an 8P8C by pin number (and never actual 
> > > > >> conductors). 
> > > > > 
> > > > > Again, the only difference is the color of the wires in the cables. 
> > > > > You can use either type of cable and they are identically the same 
> > > > > unless you cut one open and look at the colors. 
> > > > This is mostly true. The amount of twist is different between the colors. 
> > > > There's two amounts of twist used, strip the sheath off a cable and look 
> > > > at the pairs. It's obvious once you see it. Wiring up patch cables with 
> > > > odd color sequences may not meet specs. 
> > > The reference I found said there were four twists used, and also indicated the amount of twist is not in the standard. So no point in assuming any correlation between twist and color. 
> > each pair have a different number of twists per length to reduce crosstalk
> According to para 5.8.2 of TIA 568.C.2 
> "Because of their identical pair groupings, patch cords terminated in either T568A or T568B 
> may be used interchangeably, provided that both ends are terminated with the same pin/pair 
> scheme." 
> As for the number of twists per unit length, the standard simply states: 
> "5.6.2 Pair assembly 
> The pair twist lengths shall be chosen to ensure compliance with the transmission requirements of this 
> Standard." 
> In other words, it is entirely up to the cable manufacturer to choose how many twists 
> per unit length are used so long as the completed cable is within specification. 
> So different patch cables could have totally different internal construction 
> and still meet the standard. 

Bingo!  Give the man a kewpie doll!  

-- 

Rick C.

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