NEXT
NEXT is a measure of interference from other wire pairs. The signal bleeds from one set of wires to the other causing crosstalk.
The NEXT measure seeks to determine how much signal bleed is occurring.
A cable tester measures NEXT by placing a series of different frequency signals on the wire
A good cable tester displays the NEXT readings against the acceptable limits put forth in the standard.
Both ends of the cable should be tested for NEXT.