====== Structured Cabling ======

Structured cabling refers to a planned and organised way to wire data cabling in a building, usually this will be Cat5e cable terminated on an RJ45 patch panel at the wiring centre end and RJ45 faceplates at the user's end. This is a flexible way to carry data and telephone traffic, but I have not seen much info about how to wire the incoming telephone circuit to the patch panel. This attempts to rectify the position. Thanks to Robert Bradley (who will know who he is if he ever reads this!) for the info here.


===== Telephones over structured cabling =====

At the patch panel end, I'll assume the incoming circuit comes in on an LJU (Line Jack Unit, BT speak for the socket they terminate their line on- same principle as RJ11 used in USA for example). 

The LJU socket has 6 connections, usually 1 & 6 are unused, 2 & 5 are the speech pair and 3 & 4 are used for signalling. 

1 & 6 may be used for special circuits, e.g. Telewest wire 2MB/s leased lines using 1 & 2 and 5 & 6 for the two data circuits to Nokia DNT2 units.

^ Pin   ^Pair Colour	^Function ^
|1	|Green/White	|Not Used |
|2	|Blue/White	|"B" wire, -50v rel to earth |
|3	|Orange/White	|Bell |
|4	|White/Orange	|Earth, only for PABX usually |
|5	|White/Blue	|"A" wire, 0v rel to earth |
|6	|White/Green	|Not Used |




^ RJ45	^ LJU	^ Pair	^ Function ^
| 1	| 3	| 2	| Signalling |
| 2	| 4	| 2     | Signalling |
| 3	| x	| 3	| Not Used |
| 4	| 5	| 1	| Speech |
| 5	| 2	| 1     | Speech | 
| 6	| x	| 3	| Not Used |
| 7	| x	| 4	| Not Used |
| 8	| x	| 4     | Not Used |