This European Telecommunication Standard (ETS) defines the interface b etween the Subscriber Identity Module (SIM) and the Mobile Equipment ( ME) for use during the network operation phase of GSM as well as those aspects of the internal organization of the SIM which are related to the network operation phase. This is to ensure interoperability betwee n a SIM and an ME independently of the respective manufacturers and op erators. The concept of a split of the Mobile Station (MS) into these elements as well as the distinction between the GSM network operation phase, which is also called GSM operations, and the administrative man agement phase are described in the GSM 02.17 [6]. This ETS defines: - the requirements for the physical characteristics of the SIM, the el ectrical signals and the transmission protocols; - the model which shall be used as a basis for the design of the logic al structure of the SIM; - the security features; - the interface functions; - the commands; - the contents of the files required for the GSM application; - the application protocol. Unless otherwise stated, references to GSM also apply to DCS 1800. This ETS does not specify any aspects related to the administrative ma nagement phase. Any internal technical reallocation of either the SIM or the ME are only specified where these reflect over the interface. T his ETS does not specify any of the security algorithms which may be u sed. This ETS defines the SIM/ME interface for GSM Phase 2. While all attem pts have been made to maintain phase compatibility, any issues that sp ecifically relate to Phase 1 should be referenced from within the rele vant Phase 1 specification.