Failures of Ethernet local area network (LAN) ports have been attributed to the use of inappropriate surge protective devices (SPDs), lack of insulation coordination and inappropriate wiring, which causes the failure of transformers, associated wiring, components and connectors. Recommendation ITU-T K.126 discusses isolation transformer parameters and how they influence the equipment common-mode and differential-mode surge performance. Access to the full text of Recommendation ITU‑T K.95 is necessary to fully understand this Recommendation.