Unbalanced attenuation TCL and his family

Transverse Conversion Loss (TCL)
is the ratio (in dB) of a common-mode returned voltage measured on a wire pair relative to a differential-mode voltage applied to the same end of the pair. The TCL value shows how well the impedance of the pair's conductors is balanced. This parameter and its derivatives, also called Unbalanced Attenuation measurements, are required by all major standardisation bodies like ANSI/TIA, IEC or YD/T