ETSI TS 131 111定义了UICC和移动设备（ME）之间的接口，以及强制性ME 程序，特别是针对“USIM应用程序工具包”。本文件主要参考ETSI TS 102 223[32]，其中描述了 UICC中的应用程序工具包。USAT是一套在3G/LTE网络运营阶段使用的命令和程序，此外还有 定义见TS 31.101[13]。指定接口是为了确保UICC和ME之间的互操作性，独立于各自的接口 制造商和运营商。本文件定义了3G/LTE技术:命令；应用协议；每个程序对UICC和ME的强制性要求。本文件没有具体说明与行政管理阶段有关的任何方面。任何内部的 UICC或ME的技术实现仅在其反映在接口上的情况下指定。现在 本文件未规定可能使用的任何安全算法。为免生疑问，对ETSI TS 102 223[32]条款的引用包括该条款的所有子条款， 除非特别提到。目标规范ETSI TS 102 223[32]包含超出3GPP要求范围的材料，以及 本文件说明了哪些部分在范围内，哪些不在范围内。3GPP ME可能支持3GPP不需要的功能，但这样做的要求不在 3GPP的范围。

ETSI TS 131 111 defines the interface between the UICC and the Mobile Equipment (ME), and mandatory ME procedures, specifically for "USIM Application Toolkit".The present document refers in its majority to the ETSI TS 102 223 [32], which describes the generic aspects of application toolkits within the UICC.USAT is a set of commands and procedures for use during the network operation phase of 3G/LTE, in addition to those defined in TS 31.101 [13].Specifying the interface is to ensure interoperability between a UICC and an ME independently of the respective manufacturers and operators.The present document defines for 3G/LTE technology:the commands;the application protocol;the mandatory requirements on the UICC and ME for each procedure.The present document does not specify any aspects related to the administrative management phase. Any internal technical realization of either the UICC or the ME are only specified where these reflect over the interface. The present document does not specify any of the security algorithms which may be used.For the avoidance of doubt, references to clauses of ETSI TS 102 223 [32] include all the subclauses of that clause, unless specifically mentioned.The target specification ETSI TS 102 223 [32] contains material that is outside of the scope of 3GPP requirements and the present document indicates which parts are in the scope and which are not.A 3GPP ME may support functionality that is not required by 3GPP, but the requirements to do so are outside of the scope of 3GPP.