The SIM Application Toolkit is an ETSI defined standard (GSM 11.14) that defines a framework on top of Java Card for SIM resident application (so-called SIM Toolkit applets).
The SIM (Application) Toolkit is an ETSI defined standard (GSM 11.14) that defines a framework on top of Java Card for SIM resident application (so-called SIM Toolkit applets). These applets exists outside of the GSM 11.11 file system. Mobile phones that support SIM toolkit will regularly poll applets, allowing a SIM Toolkit applet to (1) add GUI menus and (2) respond to events, such as reception of certain SMS text messages or selection of specific menu items by the user. The SIM Toolkit applets are managed by Global Platform, which explicitly allows management over-the-air (OTA) by the mobile network operator (MNO). Most mobile phones place the menus generated by the SIM Toolkit applets in a "Extra" or "Tools" menu. This has three major advantages in user-friendliness: firstly, the MNO can perform remote applications management (install new versions, etc.); secondly, SIM applications can respond to messages from the network without disturbing the user, and thirdly, a SIM application can use the handset’s GUI, and such an application takes priority over applications that are not located on the SIM (such as MIDlets and apps).
