Recently, I came across some useful diagrams and notes related to cabling.
Here are the urls:

Good technical articles at: www.internetcsi.com/edd.htm#technical

Useful: ftp.dgii.com/techsupport/hardware/cable/

For an incredible diagram showing RJxx to DBXX pinouts, see:
http://ftp.dgii.com/techsupport/hardware/cable/rjdb3.pdf

also: www.man.ac.uk/~mbhmivv/telecom.html

John Backus
www.beechglen.com