本建议定义了传送直接拨入信息所需的基本功能、程序和消息。

This Recommendation defines the essential functions, procedures and messages required for the transportation of direct-dialling-in information.

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防止用户更改直接拨入或通过网关守卫服务器进行的呼叫的方式。

Prevents users from changing the way calls are placed, either directly or via a gatekeeper server.

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