I removed the old jack and discovered eight wires: BLUE, ORANGE, GREEN, BROWN, WHITE/BLUE, WHITE/ORANGE, WHITE/GREEN and WHITE/BROWN.
In the industry we refer to them as 4 pair.
Blue & Blue/White is the first pair
Orange & Orange/White is the second pair
Green & Green/White is the third pair
Brown & Brown/White is the fourth pair
CAUTION If this is on a phone system then crossing, shorting or miss wiring could damage equipment.
