HTML 电话 : link to emergency number

Question

如何创建 HTML <a href="tel:"></a>链接到紧急号码，如 911或 112 ?

RFC says

The phone number can be represented in either global or local notation. All phone numbers MUST use the global form unless they cannot be represented as such. [Emergency numbers ("911", "112")] cannot be represented in global form and need to be represented as a local number with a context.

来自 local-context section我觉得理解什么是“本地上下文”并不容易，更不用说这种情况下正确的上下文了。它列出了域前缀，如 houston.example.com或数字前缀，如 +1 ，并且在一段中说

A context consisting of the initial digits of a global number does not imply that adding these to the local number will generate a valid E.164 number. It might do so by coincidence, but this cannot be relied upon. (For example, "911" should be labeled with the context "+1", but "+1-911" is not a valid E.164 number.)

但是这一段的措辞再次令人困惑。

是

<a href="tel:+49-112">112</a>

现在这样做的正确方法，以及它不是有效的 E.164 号码这一事实无关紧要？

或者它不是有效的 E.164 号码是一个问题？

In some other places我看到人们使用

<a href="tel:112;phone-context=emergency.example.com">112</a>

再次 other people recommend

<a href="tel:112;phone-context=+49">112</a>

但是当我在 Android 上点击该链接时，拨号器会打开该号码

112;746632668398+49

Answer 1

引用 Section 5.1.5 RFC 状态

A context consisting of the initial digits of a global number does not imply that adding these to the local number will generate a valid E.164 number. It might do so by coincidence, but this cannot be relied upon. (For example, "911" should be labeled with the context "+1", but "+1-911" is not a valid E.164 number.)

我的解释是，紧急号码应该以国家特定的前缀为前缀，即

在美国，911应该用作 <a href="tel:+1-911">911</a>

在德国 112应该用作 <a href="tel:+49-112">112</a>

本段的其余部分是关于此语法不符合 E.164 建议。据我所知，E.164 在这种情况下是无关紧要的。