Wait. I didn't know this. They send inverse signals? Really? Does that mean that long cat-5 cables made with the wrong standard wont work on some equipment?!
You are mentioning two things. 1) yes, they send send signals, and their "inverse" over a pair of cables. That's guaranteed by the use of transformers on your network card/network switch. Current that the transformer sends in one line of a pair, has to be returned in the other pair.
On an old 10MBit or 100MBit/s card (10BaseT, 100BaseT) on each device there will be one pair to send data out, and one to receive data. This uses up 4 pins on your RJ45 connector, the other 2 are unused. The pair that is used on your network card to send out data are pins 1 and 2. The pair that is used on your network card to receive data is on pins 3 and 6.
The 2nd thing you mention are the two standards TIA/EIA-568 assigns colors to pins, and they have a version A and B where the colours of pair 1/2 and pair 3/6 are swapped.
Hence, when you have a cable where one side is wired according to "A" and the other is wired according to "B" you have something that, in the old days, was called a cross-cable, which you could use to directly connecto two computers with each other, without having a hub or switch in between. Which is very useful, especially if you'd connect e.g. two switches in two buildings with each other.
But because miswirings regarding the two color schemes were so frequent, and connecting routers/switches/computers directly using "straight" cables was so convenient, most devices manufactured after the 90s can swap these pairs internally automatically. Hence no matter if you have a strait or cross-cable, or a miswired 568A/B installation computers will just function fine.
With 1000BaseT (Gigabit-Ethernet) data is transmitted and received on all pairs simultaneously, and also this miswiring is automatically detected and taken into account.
There are two standards, you can pick either it doesn't matter. You use the same pattern of colors on both sides. (The colors different between the standards, but the difference is cosmetic, not electrical.)
That means pin 1 is the same on both sides, the devices using this cable have to be different, like a network card on one side and a switch on the other. Internally the two devices have opposite meaning of what wire is receive and transmit.
Or you can use one standard on one end, and the other standard on the other. This makes a crossover cable, where the receive and transmit pairs are swapped.
This is good when connecting two devices that both have the same belief about which pin is receive and transmit.
These days people got tired of dealing with that and most devices auto negotiate which pin is which, and the type of cable doesn't matter.
Ethernet uses differential signaling, a pair of wires transmits the positive and negative sides of the signal. When interference hits the twisted pair, it affects both signals the same way, and the effect is cancelled out.
If you try to use two wires from different pairs for one signal, you lose this property because now the wires are further apart, and possibly worse, twisted with another signal.
Comments
Wait. I didn't know this. They send inverse signals? Really? Does that mean that long cat-5 cables made with the wrong standard wont work on some equipment?!
You are mentioning two things. 1) yes, they send send signals, and their "inverse" over a pair of cables. That's guaranteed by the use of transformers on your network card/network switch. Current that the transformer sends in one line of a pair, has to be returned in the other pair.
https://www.google.de/search?q=ethernet+transformer&tbm=isch
On an old 10MBit or 100MBit/s card (10BaseT, 100BaseT) on each device there will be one pair to send data out, and one to receive data. This uses up 4 pins on your RJ45 connector, the other 2 are unused. The pair that is used on your network card to send out data are pins 1 and 2. The pair that is used on your network card to receive data is on pins 3 and 6.
The 2nd thing you mention are the two standards TIA/EIA-568 assigns colors to pins, and they have a version A and B where the colours of pair 1/2 and pair 3/6 are swapped.
https://en.wikipedia.org/wiki/TIA/EIA-568
Hence, when you have a cable where one side is wired according to "A" and the other is wired according to "B" you have something that, in the old days, was called a cross-cable, which you could use to directly connecto two computers with each other, without having a hub or switch in between. Which is very useful, especially if you'd connect e.g. two switches in two buildings with each other.
But because miswirings regarding the two color schemes were so frequent, and connecting routers/switches/computers directly using "straight" cables was so convenient, most devices manufactured after the 90s can swap these pairs internally automatically. Hence no matter if you have a strait or cross-cable, or a miswired 568A/B installation computers will just function fine.With 1000BaseT (Gigabit-Ethernet) data is transmitted and received on all pairs simultaneously, and also this miswiring is automatically detected and taken into account.
There are two standards, you can pick either it doesn't matter. You use the same pattern of colors on both sides. (The colors different between the standards, but the difference is cosmetic, not electrical.)
That means pin 1 is the same on both sides, the devices using this cable have to be different, like a network card on one side and a switch on the other. Internally the two devices have opposite meaning of what wire is receive and transmit.
Or you can use one standard on one end, and the other standard on the other. This makes a crossover cable, where the receive and transmit pairs are swapped.
This is good when connecting two devices that both have the same belief about which pin is receive and transmit.
These days people got tired of dealing with that and most devices auto negotiate which pin is which, and the type of cable doesn't matter.
Ethernet uses differential signaling, a pair of wires transmits the positive and negative sides of the signal. When interference hits the twisted pair, it affects both signals the same way, and the effect is cancelled out.
If you try to use two wires from different pairs for one signal, you lose this property because now the wires are further apart, and possibly worse, twisted with another signal.