Cat 5 Networking

The pinouts below are for RJ45 8pin sockets looking into the socket. The circuit pair IDs are shown above the socket (T1 R1 etc) but don't confuse them with Transmit and Receive! Note: The terminology T and R 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! background colour=body colour on wire, character colour=stripe colour on wire. T = tip +ve, R = ring -ve Examples: T568B CAT 5 pin 1 is white cable/orange stripe +ve of pair 2 ; pin 8 is brown cable/white stripe -ve of pair 4 The CAT5 sockets (ModTap) supplied by RS are generally colour coded to the EIA568B (T568B) standard (formerly known as AT&T 258A) and ISDN sockets are generally coded to EIA568A standard (which is electrically compatible but the pair and colour codes of #2 and #3 are swapped around - just to be awkward! Patch cables and premises wiring is normally made straight through (pin1 <=> pin1 etc) with any necessary crossover being done in the hub. However, a X-over patch lead is sometimes required and it is also possible to join two machines directly together without a hub using just a x-over cable where T2 is connected to T3 and R2 connected to R3. 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. BT phone circuits over CAT5 Modern BT phone systems use the BS6312 plug and socket with CW1311 tinsel CW1308 solid cable. The BS6312 plug has 6 pins with pin 6 defined in the standard as next to the latch. The matching BS6312 socket is very confusingly found numbered in two ways! 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 Conventional BT wiring colours for sockets (from BT leaflet supplied with extension sockets & Line Connection Unit LCU) using BT style pinout numbering and showing BT 2 and 3 wire feed into house. BT BS6312 BT 2 WIRE GREEN/WHITE   1 latch BLUE/WHITE 470K to pin 4 2 --- B --> ORANGE/WHITE   3 WHITE/ORANGE 1.8uF to pin 5 4 WHITE/BLUE ---> 5 --- A --> WHITE/GREEN   6 BT BS6312 BT 3 WIRE GREEN/WHITE 1 latch 5 BLUE/WHITE 2 --- 6 ORANGE/WHITE 3 7 WHITE/ORANGE 4 --- 6 WHITE/BLUE 5 --- 7 WHITE/GREEN 6 --- 8 Earth loop recall uses BS6312 pin 4 shorted to pin 5. Bell ring generated by master socket on pin 3 via capacitor 1u8 shown. Secondary socket does not have additonal components. BT phone handset to RJ11 WECO line cord BT phones commonly use either the BS6312 BT type plugs to connect handset and line cords to the phone (History:there was a variation on the BT 6312 used on the old Sinclair QL computers) or the American WECO RJ11 plugs and then need a RJ11 to BT BS6312 for the line cord. This latter type 4-way cord is wired as follows:- BS6312 RJ11 (6 pin) 1 latch 1 2 --- 2 3 --- 3 4 --- 4 5 --- 5 6   6