The present document sets out the major engineering requirements for telecommunications equipment forming part of a public telecommunications network installed either on public telecommunications operators' sites or in premises of operators' customers. It is expected that the areas of transmission equipment and switching equipment will increasingly merge into one. As a result, the present document should be applied to all forms of telecommunications equipment. The operating authorities should be given the data to help them plan buildings and building utilization, including ceiling heights, equipment and traffic areas, hallways and doors and transport instal