ISO/IEC 14763-4:2021(E) specifies the measurement of two- and four-pair balanced cabling of a) end-to-end (E2E) link Class D, E and EA; b) modular plug terminated links (MPTLs) of Class D, E, EA, F, FA and of Class I and II; c) direct attach cabling of Class D, E, EA, F, FA and of Class I and II. The free connectors which terminate two and four pairs in field and laboratory conditions are included. This second edition cancels and replaces the first edition published in 2018. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: • measurement of the transmission performance of modular plug terminated link (MPTL) and direct attach cabling were added. • Additional requirements of test head designs of E2E link were introduced.