Recommendation ITU-T K.66: o provides recommendations for bonding and earthing of telecommunication equipment in residential and commercial customer premises; o refers to Recommendation ITU-T K.21 (2008) for equipment resistibility requirements; o recommends earthing and bonding requirements to coordinate with the resistibility requirements of Recommendation ITU-T K.21 (2008) and the safety requirements of IEC 60950-1 and IEC 62368; o recommends the installation practices for bonding of all services and the installation of surge protective devices (SPDs); o illustrates problems associated with earthing and bonding and provides solutions for these earthing and bonding problems. These include: 1) methods to improve the earthing and bonding; 2) methods of providing additional protection external to the equipment; 3) special resistibility and safety requirements; o recommends responsibilities for protection at customer premises; o refers to IEC 62305-3 for protection against direct lightning. This revision of ITU-T K.66 includes an update of the references and a revision of clause 6.3 to include more information on preventing equipment damage. Appendix IV, containing information on special resistibility requirements has been deleted; the reader is directed to Recommendation ITU T K.44 (2008).