This part of IEC 60728 deals with the safety requirements applicable to fixed sited systems and equipment. As far as applicable, it is also valid for mobile and temporarily installed systems, for example, caravans. Additional requirements may be applied, for example, referring to " electrical installations of buildings and overhead lines, " other telecommunication services distribution systems, " water distribution systems, " gas distribution systems, " lightning systems. This standard is intended to provide specifically for the safety of the system, personnel working on it, subscribers and subscriber equipment. It deals only with safety aspects and is not intended to define a standard for the protection of the equipment used in the system.