This section of IEC 870-5 applies to telecontrol equipment and systems with coded bit serial data transmission for monitoring and controlling geographically widespread processes. This section of IEC 870-5 gives rules for defining information elements and presents a set of information elements, in particular of digital and analog process variables, that are frequently used in telecontrol applications. Clause 4 presents syntactic rules for defining application specific information elements. These rules comprise methods for semantic declarations, that is assignments of the functional interpretation of the defined information fields. Clause 5 applies the declaration method to the basic data types defined in Clause 4 and introduces particular subtypes of data. Clause 6 presents a set of information elements that are frequently used in telecontrol applications. These elements and the mentioned recommended applications for these elements are recommendations only. Definitive declarations of information elements have to be fixed in application profiles. Single information elements, sequences or combinations of information elements may form an information object that is identified by an object address and by an object structures specification described in IEC 870-5-3.