This Global System for Mobile communications Technical Specification ( GTS) defines the interface between the Subscriber Identity Module (SIM ) and the Mobile Equipment (ME), and mandatory ME procedures, specific ally for SIM Application Toolkit. SIM Application Toolkit is a set of commands and procedures for use du ring the network operation phase of GSM, in addition to those defined in GSM 11.11 [14]. Specifying the interface is to ensure interoperability between a SIM a nd an ME independently of the respective manufacturers and operators. The concept of a split of the Mobile Station (MS) into these elements as well as the distinction between the GSM network operation phase, wh ich is also called GSM operations, and the administrative management p hase are described in GSM 02.17 [3]. This Technical Specification defines: - the commands; - the application protocol; - the mandatory requirements on the SIM and ME for each procedure. Unless otherwise stated, references to GSM also apply to DCS 1800. This standard does not specify any aspects related to the administrati ve management phase. Any internal technical realization of either the SIM or the ME are only specified where these reflect over the interfac e. This standard does not specify any of the security algorithms which may be used. This Technical Specification defines an enhancement for GSM Phase 2+ o f the SIM/ME interface for GSM Phase 2. While all attempts have been m ade to maintain phase compatibility, any issues that specifically rela te to Phase 1 should be referenced from within the relevant Phase 1 sp ecification.