YD/T 5098 is a Chinese telecommunications industry design code, and it is a design document rather than a test standard: it tells the engineer how the lightning protection and earthing of a telecommunications station are to be arranged, and it is the document under which such a station is designed and inspected in China. The scale of the problem is unusual. A large station may be fed from several directions, may have a very extensive earthing network that is bonded to those of adjacent buildings, may carry thousands of copper subscriber pairs that leave the building, and may also contain equipment supplied from a direct current power system, so the earthing design has to reconcile the requirements of the alternating current installation, of the telecommunications equipment and of the building and the surrounding structures. The code governs the arrangement of the earthing network, the bonding of the various systems, the protection zones through the building, the routing of cables and the selection and placement of protective devices.