0     -    General terms (basic terms and terms common to several of the areas covered by the following sections)
 1     -    Switching functions and techniques
 2     -    Signalling functions and techniques
 3     -    Control functions
 4     -    Interfaces and interface functions (machine-machine)
 5     -    Equipment and hardware
 6     -    Executive software
 7     -    Functions for basic and supplementary services
 8     -    Mobile station networks
 9     -    Telephone subscriber's equipment and local lines
Annex A - Alphabetical list of terms defined in this Recommendation.
According to the conventions applied in the lists, indications in round brackets are qualifiers or alternative terms in general use in addition to the principal term.
Examples: call (in software)