本文件规定了第三阶段的补充业务呼叫保持（SS-Hold）描述 地面集群无线电（TETRA）。SS-HOLD允许用户中断现有单个呼叫的通信，然后，如果需要， 重新建立沟通。人机界面（MMI）和充电原理不在本文件范围内。根据中定义的方法，补充业务规范分三个阶段生成 ITU-T建议I.130[1]。阶段1描述从用户的角度指定服务（请参见 ETS 300 392-10-12[7]）。第2阶段描述确定了所需的功能能力和信息流 支持第1阶段描述中规定的服务（见EN 300 392-11-12[8]）。当前阶段3描述 指定空中接口和各种系统间接口（ISI）上支持SS-HOLD的协议。注1:根据ITU-T建议I.130[1]，任何电信服务的第3阶段描述 解决了网络实现方面的问题。因此，它包括两个步骤:规范 任何服务程序（尤其是服务）中涉及的各个参考点的所有协议 操作）是第3阶段描述的第一步，以及 相应的网络实体是其第二步。注2:未提供后者，因为它们可以从功能实体的规范中派生出来 第二阶段描述中的动作。本文件适用于语音加数据个人通话；更具体地说，是指以下实体:被服务用户及其远程方的MS/LSs； 以及单个呼叫中的服务用户交换和管理基础设施（SwMI）。

The present document specifies the stage 3 description of the Supplementary Service Call Hold (SS-HOLD) for the Terrestrial Trunked Radio (TETRA).SS-HOLD enables a user to interrupt communication on an existing individual call and then subsequently, if desired, re-establish communication.Man-Machine Interface (MMI) and charging principles are outside the scope of the present document.Supplementary service specifications are produced in three stages according to the method defined in ITU-T Recommendation I.130 [1]. The stage 1 description specifies the service from the user's point of view (see ETS 300 392-10-12 [7]). The stage 2 description identifies the functional capabilities and the information flows needed to support the service as specified in its stage 1 description (see EN 300 392-11-12 [8]). The present stage 3 description specifies the protocols at the air interface and at the various Inter-System Interfaces (ISI) to support SS-HOLD.NOTE 1: According to ITU-T Recommendation I.130 [1], the stage 3 description of any telecommunication service addresses the network implementation aspects. Consequently it comprises two steps: the specifications of all protocols at the various reference points involved in any of the service procedures (notably the service operation) are the first step of the stage 3 description, and the specifications of the functions of the corresponding network entities are its second step.NOTE 2: The latter have not been provided since they can be derived from the specification of the functional entity actions in the stage 2 description.The present document is applicable to Voice plus Data individual calls; more specifically to the following entities:the MS/LSs of the served user and of his distant party; andthe served user Switching and Management Infrastructure (SwMI) in an individual call.