This Recommendation seeks to establish fundamental testing methods and criteria for the resistibility of telecommunication equipment to overvoltages and overcurrents. Overvoltages or overcurrents covered by this Recommendation include surges due to lightning on or near the line plant, short-term induction of alternating voltages from adjacent electric power lines or electrified railway systems, earth potential rise due to power faults, and direct contacts between telecommunication lines and power lines. Major changes compared with the 2003 version of this Recommendation include: " the addition of substantial information and schematics relating to decoupling, terminating and coupling to ground of associated equipment; " the introduction of an internal port to internal port test; " information on classifying ports as external or internal " the addition of tolerances for the power induction and power contact tests.