CPV code 50334400 designates Communications system maintenance services in the Common Procurement Vocabulary (CPV 2008), the EU classification used to describe the subject of public contracts.
50334400 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 50334000 (Repair and maintenance services of line telephony and line telegraphy equipment).