Crosstalk is an undesired mutual interference of transmission channels in telephone networks or in the cabling of LANs. It is a frequency interference of adjacent conductor pairs due to capacitive and inductive couplings between current-carrying lines.
Crosstalk can be reduced by design measures by reducing the partial capacitances between adjacent conductors. To reduce these capacitances, the cable pairs of symmetrical cables are stranded with different lay lengths. Further decoupling is achieved by shielding the individual pairs and quads.
Crosstalk is divided into near end crosstalk( NEXT) at the beginning of the cable and far end crosstalk ( FEXT) at the opposite, distant end of the cable. In addition, there is also crosstalk between data cables, alien crosstalk( AXT).