IEC 61439-4:2012 defines the specific requirements of ACS as follows:
- ASSEMBLIES for which the rated voltage does not exceed 1 000 V in case of a.c. or 1 500 V in case of d.c.;
- ASSEMBLIES where the nominal primary voltage and the nominal secondary voltage of transformers incorporated in ACS are within the limits specified above;
- ASSEMBLIES intended for use on construction sites, both indoors and outdoors, i.e. temporary places of work to which the public do not generally have access and where building construction, installation, repairs, alteration or demolition of property (buildings) or civil engineering (public works) or excavation or any other similar operations are carried out;
- transportable (semi-fixed) or mobile ASSEMBLIES with enclosure. The manufacture and/or assembly may be carried out other than by the original manufacturer. This first edition of IEC 61439-4 cancels and replaces the second edition of IEC 60439-4 (2004), and constitutes a technical revision. This edition includes the following significant technical changes with respect to the last edition of IEC 60439-4:
- modification of the title as "Part 4: Particular requirements for assemblies for construction sites (ACS)";
- alignment on IEC 61439-1 regarding the structure and technical content, as applicable;
- to allow comparison with tested ACS.

This publication is to be read in conjunction with IEC 61439-1:2011.