ITU-T K.45 specifies the resistibility requirements for telecommunication equipment installed in the access and trunk networks. The equipment in question is mounted outside the protected environment of a central office: it includes the cabinets, cross-connection points, repeaters, line units and remote transmission equipment that are placed in the street, on poles or in unheated enclosures, and it is therefore exposed to the full outdoor electromagnetic environment without the benefit of a building and an integrated earthing system. The recommendation defines the test levels and waveforms appropriate to this exposure, covering power frequency voltages that represent contact with or induction from power lines and impulse voltages and currents that represent lightning, and it distinguishes between the ports that connect to overhead plant, to buried cable and to the local mains supply. It specifies the test procedure, the number of applications and the criteria by which the equipment is judged to have withstood the test, and it provides for a reduced level where the installation is protected by an external surge protective device.