This Technical Specification defines the stage one description of the Subscriber Identity Module Application Programming Interface (SIM API) internal to the SIM. Stage one is an overall service description@ and does not deal with the implementation details of the API. This TS includes information applicable to network operators@ service providers and terminal@ SIM@ switch and database manufacturers. This TS contains the core requirements which are sufficient to provide a complete service. It is highly desirable however@ that technical solutions for a SIM API should be sufficiently flexible to allow for possible enhancements. Additional functionalities not documented in this TS may implement requirements which are considered outside the scope of this TS. This additional functionality may be on a network-wide basis@ nation-wide basis or particular to a group of users. Such additional functionality shall not compromise conformance to the core requirements of the service.