UTP Cabling Pin outs
 


Wiring
Connectors are frequently terminated using the T568A or T568B pin/pair assignments that are defined in TIA/EIA-568-B. The drawings to the right show that the copper connections and pairing are the same, the only difference is that the orange and green pairs (colors) are swapped. A cable that is wired as T568A at one end and T568B at the other (Tx and Rx pairs reversed) is a "crossover" cable. Before the widespread acceptance of auto-MDI/MDIX capabilities a crossover cable was needed to interconnect similar network equipment (such as hubs to hubs). A cable wired the same at both ends is called a "patch" or "straight-through" cable, because no pin/pair assignments are swapped. Crossover cables are sometimes still used today to connect two computers together without a switch or hub, however most Network Interface Cards (NIC) in use today are called smart, because they automatically configure themselves based on the type of cable plugged into them. If a "patch" or "straight" cable is used to connect two computers with "smart" NICs, the NIC will configure itself to switch the Tx and Rx.

 

Pin T568A Pair T568B Pair 1000BASE-T Signal ID Wire T568A Color T568B Color Pins on plug face (socket is reversed)
1 3 2 DA+ tip Pair 3 Tip
white/green stripe
Pair 2 Tip
white/orange stripe
Rj45plug-8p8c.png
2 3 2 DA- ring Pair 3 Ring
green solid
Pair 2 Ring
orange solid
3 2 3 DB+ tip Pair 2 Tip
white/orange stripe
Pair 3 Tip
white/green stripe
4 1 1 DC+ ring Pair 1 Ring
blue solid
Pair 1 Ring
blue solid
5 1 1 DC- tip Pair 1 Tip
white/blue stripe
Pair 1 Tip
white/blue stripe
6 2 3 DB- ring Pair 2 Ring
orange solid
Pair 3 Ring
green solid
7 4 4 DD+ tip Pair 4 Tip
white/brown stripe
Pair 4 Tip
white/brown stripe
8 4 4 DD- ring Pair 4 Ring
brown solid
Pair 4 Ring
brown solid

Note that the only difference between T568A and T568B is that pairs 2 and 3 (orange and green) are swapped. Both configurations wire the pins "straight through", i.e., pins 1 through 8 on one end are connected to pins 1 through 8 on the other end. Also, the same sets of pins connect to the opposite ends that are paired in both configurations: pins 1 and 2 form a pair, as do 3 and 6, 4 and 5, and 7 and 8.

 

568A and 568B Pin-out

568A

568B

 
White/Green --\ White/Orange --\ Pin 1
Green --/ Orange --/ Pin 2
White/Orange ------\ White/Green ------\ Pin 3
Blue --\      \ Blue --\      \ Pin 4
White/Blue --/      / White/Blue --/      / Pin 5
Orange ------/ Green ------/ Pin 6
White/Brown --\ White/Brown --\ Pin 7
Brown --/ Brown --/ Pin 8

 

Even you are using Cat 5 cable with 4 twisted pair wires, it doesn't mean that the cable is 100% compliant with EIA/TIA standard if it is not connected to RJ-45 in the way it should be.  The Straight-through cable ("Patch cable") connection should be:

    Pin 1 and 2 are connected to same twisted pair wire
    Pin 3 and 6 are connected to same twisted pair wire
    Pin 4 and 5 are connected to same twisted pair wire
    Pin 7 and 8 are connected to same twisted pair wire


Here is the pin-out for Crossover cable ("Uplink cable"):
Point A         Point B
TR+     Pin 1     -----     Pin 3     RCV+
TR-     Pin 2     -----     Pin 6     RCV-
RCV+     Pin 3     -----     Pin 1     TR+
RCV-     Pin 6     -----     Pin 2     TR-