Bonding and earthing of telecommunication installations is done for reliability and personnel safety reasons. The evolution of the power architecture of telecommunication systems has created new installation conditions for equipment. To cover these situations, bonding and earthing configurations need to be defined that ensure adequate reliability and safety are maintained. This Recommendation analyses the situation in which the equipments, connected together, are installed in different buildings with different earthing and power feeding conditions. Also this Recommendation includes installation requirements for equipment located in different buildings, having the same earthing and feeding power conditions, to improve the shielding and bonding of telecommunication and power cable between buildings. Other recommendations dealing with bonding and earthing are K.27 (Bonding configurations and earthing inside a telecommunication building), K.35 (Bonding configurations and earthing at remote electronic sites) and K.66 (Protection of customer premises from overvoltages). These recommendations do not cover how equipment installed in these different environments can be interconnected.