very basic cable question

The colors don't matter electrically, but using the standard colors might reduce errors.  Make sure you wire the pairs correctly and that you don't exchange the wires of a pair.  Pins 1+2 are a pair, as are 3+6, 4+5, and 7+8.

Here's a Wikipedia page: https://en.wikipedia.org/wiki/Ethernet_physical_layer#Twisted-pair_cable

Thanks, John. I have been reading several wiki pages about the topic, and my brain hurts! I guess I'm wondering if T568A or B wiring is best? As I read it, B is compatible with older telco standards, but A is required by the Fed for some reason. I think the most important thing is to keep the cable straight through, keep the wires connected to the same pins.

The standards are much more important when wiring inside the walls of a building or wiring to a building.  In that case, you really want to use a standard so you can get the wiring right the first time and your installers don't have to think about it.

If you are making cables for connecting devices together and not going through walls, which standard you use isn't so important.  Just wire the cable straight through as you have said, and make sure 1+2, 3+6, 4+5, and 7+8 are paired since they carry differential signals.  10baseT and 100baseT only use 1+2 and 3+6.  1000baseT uses all four pairs.

After doing some more research, I'm wondering why the 3+6 pairing; does the extra twist give some noise or crosstalk cancellation? I also notice that the sequence goes from stripe -solid to solid -stripe then back to stripe -solid through here and am trying to understand how the wires revolve back into their pair packages going back into the cable. Once they're back in the jacket, it's all CatX. Just trying to also understand the differences between Cat5x and Cat6x, reading there's also Cat8 stuff out there!

I'm also concerned about the usability of cables, as Cat6 seems so stiff that it would only be useful in long runs, and Cat5 could be used in The Last 10 Feet. I can't imagine how stiff a Cat8 cable might be; it seems coax would be more flexible.

Thanks for your insights. I'm also looking at PoE...

Lee Schulz wrote:

 

After doing some more research, I'm wondering why the 3+6 pairing; does the extra twist give some noise or crosstalk cancellation? I also notice that the sequence goes from stripe -solid to solid -stripe then back to stripe -solid through here and am trying to understand how the wires revolve back into their pair packages going back into the cable. Once they're back in the jacket, it's all CatX. Just trying to also understand the differences between Cat5x and Cat6x, reading there's also Cat8 stuff out there!

I'm not sure about this, but I think the 3+6 pairing is backward compatibility to telephones.

Take a look at the RJ-45 wiring diagram at: https://en.wikipedia.org/wiki/Ethernet_physical_layer#Twisted-pair_cable

The middle two wires 4+5 can be used for a standard telephone line, which only has two wires Tip and Ring.  RJ-11 telephone connectors use the middle two pins for Tip and Ring.  The next outer two wires can be used for a second telephone line with its own twisted pair.  They were also used for low-voltage AC to light up a Princess Phone.  The four middle pins of a telephone connector map to the middle four pins (3-6) of the RJ-45.

So here's the deal.  You can run 8-wire (4-pair) cables around your building and use 4+5 for telephones and 1+2 plus 3+6 for 10baseT or 100baseT Ethernet.  In fact, you can get by with just 6 wires if all you need is 10/100baseT, or leave the extra pair 7+8 as a spare.

I'm not that familiar with Cat5/6/8 standards.  Basically, with a higher Cat number you can go longer distances at higher bit rates.  I have a DSL uplink so there's really no need for me to go faster than 100baseT, so Cat5 is fine for me.  If you want 1000baseT, you may need better cable.

Lee Schulz wrote:

 

After doing some more research, I'm wondering why the 3+6 pairing; does the extra twist give some noise or crosstalk cancellation? I also notice that the sequence goes from stripe -solid to solid -stripe then back to stripe -solid through here and am trying to understand how the wires revolve back into their pair packages going back into the cable. Once they're back in the jacket, it's all CatX. Just trying to also understand the differences between Cat5x and Cat6x, reading there's also Cat8 stuff out there!

I'm not sure about this, but I think the 3+6 pairing is backward compatibility to telephones.

Take a look at the RJ-45 wiring diagram at: https://en.wikipedia.org/wiki/Ethernet_physical_layer#Twisted-pair_cable

The middle two wires 4+5 can be used for a standard telephone line, which only has two wires Tip and Ring.  RJ-11 telephone connectors use the middle two pins for Tip and Ring.  The next outer two wires can be used for a second telephone line with its own twisted pair.  They were also used for low-voltage AC to light up a Princess Phone.  The four middle pins of a telephone connector map to the middle four pins (3-6) of the RJ-45.

So here's the deal.  You can run 8-wire (4-pair) cables around your building and use 4+5 for telephones and 1+2 plus 3+6 for 10baseT or 100baseT Ethernet.  In fact, you can get by with just 6 wires if all you need is 10/100baseT, or leave the extra pair 7+8 as a spare.

I'm not that familiar with Cat5/6/8 standards.  Basically, with a higher Cat number you can go longer distances at higher bit rates.  I have a DSL uplink so there's really no need for me to go faster than 100baseT, so Cat5 is fine for me.  If you want 1000baseT, you may need better cable.