usim

SIM Application Toolkit (STK) is a standard of the GSM system which enables the subscriber identity module (SIM card) to initiate actions which can be used for various value-added services. Similar standards exist for other network and card systems, with the USIM Application Toolkit (USAT) for USIMs used by newer-generation networks being an example. A more general name for this class of Java Card-based applications running on UICC cards is the Card Application Toolkit (CAT).The SIM Application Toolkit consists of a set of commands programmed into the SIM which define how the SIM should interact directly with the outside world and initiates commands independently of the handset and the network. This enables the SIM to build up an interactive exchange between a network application and the end user and access, or control access to, the network. The SIM also gives commands to the handset such as displaying menus and/or asking for user input.STK has been deployed by many mobile operators around the world for many applications, often where a menu-based approach is required, such as Mobile Banking and content browsing. Designed as a single application environment, the STK can be started during the initial power up of the SIM card and is especially suited to low level applications with simple user interfaces.In GSM networks, the SIM Application Toolkit is defined by the GSM 11.14 standard released in 2001.
From release 4 onwards, GSM 11.14 was replaced by 3GPP TS 31.111 which also includes the specifications of the USIM Application Toolkit for 3/4G networks.

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