CPV code 35711000 designates Command, control, communication systems in the Common Procurement Vocabulary (CPV 2008), the EU classification used to describe the subject of public contracts.
35711000 is a leaf code — the most specific level of its branch — so it can be used directly as the main CPV code of a contract notice. If it does not quite fit, check the neighbouring codes under 35710000 (Command, control, communication and computer systems).