This Recommendation provides bonding configurations and earthing for telecommunication equipment installed inside different buildings in the following cases: 1) buildings with different earthing and power feeding conditions; 2) buildings with the same earthing and power feeding conditions. This Recommendation: ?is intended to facilitate the internetworking between different equipment (interconnected by metallic links); ?can be used for new installations and@ if possible@ for the expansion and replacement of the existing installations; ?is not intended to replace national regulations on bonding and earthing. The user should refer to [ITU-T K.27] for bonding configurations and earthing inside the telecommunication building; to [ITU-T K.35] for bonding configurations and earthing at remote sites; to [ITU-T K.66] for bonding and earthing of telecommunication installations inside a customer premises. Bonding requirements between a building and an adjacent tower are outside the scope of this Recommendation. NOTE ?C In this case@ the user should refer to [b-ITU-T K.47]@ [b-ITU-T K.56] and [ITU-T K.71].