The aim of the work is analysis of possibilities for improving the layout characteristics of the plug-in units of standard construction systems (19-inch and metric systems) without any improvement or changes in the existing international and harmonized therewith national standards. On the basis of the solutions regulated by the specified standards, the possibility for development and implementation of single-board functional electronic modules in design of cases of plug-in units of standard construction systems is reviewed and substantiated. Constructive solutions are proposed to secure modular design of plug-in units on the basis of single-board functional electronic modules, such solutions being applicable to the whole diversity of the electronic equipment. A conclusion is made on probable implementation of COTS technologies in all types of electronic equipment.