RJ45 Connectors
The RJ45 connector is an 8 position, 8 conductor modular plug (“8P8C) that is used for terminating Cat5, Cat5e, Cat6, Cat7 and Cat8 Ethernet cables. A pinout is a specific order of wires that determines how the connector is terminated.
RJ45 Pinouts Standards
There are two standard RJ45 pinouts, T568A and T568B used in straight through and crossover cables. These two standards are identified by the color-coding arrangement of the eight wires necessary when attaching the connectors to a cable. The difference between the two is the position of the green and orange wires but both are acceptable.
The T568A Straight Through cable diagram, both ends use T568A:
| RJ45 Pin # | Wire Color (T568A) |
10Base-T Signal 100Base-TX Signal |
1000Base-T Signal |
|---|---|---|---|
| 1 | White/Green | Transmit+ | BI_DA+ |
| 2 | Green | Transmit- | BI_ DA- |
| 3 | White/Orange | Receive+ | BI_DB+ |
| 4 | Blue | Unused | BI_DC+ |
| 5 | White/Blue | Unused | BI_DC- |
| 6 | Orange | Receive- | BI_DB- |
| 7 | White/Brown | Unused | BI_DD+ |
| 8 | Brown | Unused | BI_DD- |
The T568B Straight Through cable diagram, both ends use T568B:
| RJ45 Pin # | Wire Color (T568B) |
10Base-T Signal 100Base-TX Signal |
1000Base-T Signal |
|---|---|---|---|
| 1 | White/Orange | Transmit+ | BI_DA+ |
| 2 | Orange | Transmit- | BI_DA- |
| 3 | White/Green | Receive+ | BI_DB+ |
| 4 | Blue | Unused | BI_DC+ |
| 5 | White/Blue | Unused | BI_DC- |
| 6 | Green | Receive- | BI_DB- |
| 7 | White/Brown | Unused | BI_DD+ |
| 8 | Brown | Unused | BI_DD- |
Cross Over Pinout
A crossover cable uses T568A wire color scheme on one end of the cable and T568B wire color scheme of the other end. You can use crossover cable if you need to connect two of the same devices, for example; computer to computer.
Why it’s important to follow the order
When connecting into an existing Ethernet network, you need to figure out if the male or female that the connector is plugging into is T568A or T568B. It’s important to follow that existing pinout sequence because they shouldn’t be used interchangeably as it can impact data communication speed.
Should I use T568A or T568B?
In today’s world the T568B has surpassed T568A and is seen as the standard wiring scheme for twisted pair structured cabling. If you are unsure of which one to use, you can default to T568B.
Four Easy Rules to Remember the Wiring Standards
- Always follow stripe, solid, stripe, solid, etc.
- Brown and Blue never move. Blue is always at the middle (Pins 4 and 6). Brown is always at the end (Pins 7 and 8).
- Green and Orange following the A/B alpha pattern. Green for A and Orange for B.
- Pin 1 is with the clip facing away from you.
After making custom patch cables for a while you will easily remember the wiring patterns. We also recommend to Print T568A and T568B patterns and tap them to your cable box so it will always be available when needed.
