Ethernet

The various bodies involved in standardisation of structured cabling (with their abbreviations) are Electronic Industry Association (EIA), the Telecommunications Industry Association (TIA), and previously AT&T (T).

The pinouts below are for RJ45 8pin sockets looking into the socket.

background colour=body colour on wire, character colour=stripe colour on wire. T = tip +ve, R = ring -ve
Examples: EIA568B CAT 5 pin 1 is white cable/orange stripe +ve of pair 2 ; pin 8 is brown cable/white stripe -ve of pair 4

Pin	Hub/Switch	Computer/Device
1	Recieve +ve	Transmit +ve
2	Recieve -ve	Transmit -ve
3	Transmit +ve	Recieve +ve
4	n/c	n/c
5	n/c	n/c
6	Transmit -ve	Recieve -ve
7	n/c	n/c
8	n/c	n/c

The somewhat old fashioned circuit pair IDs relating to Tip and Ring are shown above the socket (T1 R1 etc) but don't confuse them with Transmit and Receive! Note: The terminology comes from the old telecom days of jack plugs with 'Tip' and 'Ring' and corrosponds to the +ve and -ve on the twisted pair of cables and not Transmit and Receive of ethernet data!. EIA568B = TIA568B = T258A (AT&T).

I Recently found a lovely clear diagrams for making your patch leads at Jaysafe Systems - recommended....

ISDN

background colour=body colour on wire, character colour=stripe colour on wire. T = tip +ve, R = ring -ve
Examples: EIA568B CAT 5 pin 1 is white cable/orange stripe +ve of pair 2 ; pin 8 is brown cable/white stripe -ve of pair 4

Crossover

The older CAT3 10Base-T only specified two pairs which historically used to be numbered as pairs #1 and #2 but nowadays are commonly numbered using pairs #2 and #3 to be compatible with CAT 5 / EIA568B (again all electrically compatible - just pair numbers and colour codes changed)

There are also many more I have not shown like USOC, DEC MMJ, Token Ring and voice etc all using the RJ45.

Make your own cable

BT phone circuits over CAT5

Third party adapters and similar are commonly numbered with pin_6 also next to the latch so that they mate pin to pin with the plug as in 1-1,2-2,3-3,4-4,5-5,6-6. I call this plug numbering.

However, on BT sourced equipment and diagrams the socket is likely to be numbered in the reverse order with pin_1 next to the latch so that it mates with the plug like 1-6,2-5,3-4,4-3,5-2,6-1. I call this BT numbering.

I have checked the BS6312 1994 standard and only the plug pinout is defined - on the socket drawing the contacts are numbered in the 'reverse BT way' but it clearly states 'contact numbers for information only' so I take it the standard did not define socket contact numbering.

So beware !!! This point was also noted on the www.epl.co.uk web pages and they have a standard BT wiring diagram which shows this strange BT way.

Where we use our structured cabling to take the British BT telephone systems we use commercial plug in converters by KRONE we use BT Socket A 258A old style adapters (either master or slave types available) at the telephone handset end and our own patch leads in the network rack. The KRONE adapter is connected as follows using the 'plug pin compatible style' numbering for the BS6312 telephone socket:-

  BS6312           RJ45
    1                6
    2                4
    3                1
    4                2
    5                5
    6 latch          3
                     7
                     8

            BT BS6312      BT 2 wire          BT BS6312      BT 3 wire
            G-W  1 latch                      G-W  1 latch                 
      ,---- B-W  2 ---     B -->              B-W  2 ---     B -->            
 1u8  '---- O-W  3           BT lines         O-W  3             BT lines 
 470K       W-O  4                            W-O  4 ---     Grnd                    
       ---- W-B  5 ---     A -->              W-B  5 ---     A -->            
            W-G  6                            W-G  6 ---     C -->                   
       
       

Other Resources

World of Windows Networking
Practically Networked
Jaysafe Systems
Lanshack wiring a RJ45 plug
Jim Fuller RJ45 wiring
PeteNet Tutorials