HJB 34A is a Chinese shipbuilding industry standard, issued in the HJB series used by the naval and marine industry rather than in the national standards system, and it specifies the electromagnetic compatibility requirements that a ship and the equipment installed in it must satisfy. It succeeded an earlier edition of the same requirement and extended the scope of the disturbance programme considerably: the revision added tests for cable bundle injection, for damped sinusoidal transients and for the electrostatic discharge that arises from handling equipment in a confined metallic environment, and it increased the number of cable categories recognised in the installation so that the routing and separation rules could be applied more precisely. The requirement is written for a platform that operates in isolation, without the earthing of a fixed installation and with its own transmitters, radars and power conversion equipment operating simultaneously, and it therefore combines equipment level limits with installation rules that govern bonding, shielding and cable routing.