Just to Add Clarification to those who find this thread in the Future.

On a 6 or 8 Pin Jack. Traditional Modular cords use the Inner most pair. This is the White/Blue pair. Axxess phones like your 8520 use the 2nd pair from the middle. This is the White/Green pair on TIA 568B wiring. This is the White/Orange pair on USOC and TIA 568A wiring.
USOC Orange Pair [Linked Image from lib.store.yahoo.net]

[Linked Image from black-box.eu]

https://en.wikipedia.org/wiki/Modular_connector
https://www.phonegeeks.com/phjawicoco.html

Last edited by LinuxTech; 10/16/14 12:45 PM.