Applies to type-tested assemblies (TTA) intended for use on construction sites, i.e. temporary places of work to which the public do not generally have access and where building construction, installation, repairs, alterations or demolition of property (buildings) or civil engineering (public works) or excavations or where any other similar operations are carried out. These assemblies may be transportable (semi-fixed) or mobile. This Standard is technically equivalent to and reproduced from IEC 439-4:1990.