Recommendation ITU-T K.129 defines the basic electrical parameters to be met by silicon PN junction voltage clamping components used for the protection of telecommunication equipment or lines from surges. Examples of equipment include those located within a telecommunication centre, customer premise, access or trunk network. It is intended that this Recommendation be used for the harmonization of existing or future specifications issued by PN diode surge protective component manufacturers, telecommunication equipment manufacturers, administrators or network operators.