Do keep optional data in an optional area?

要在可选的区域保留可选的数据。

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Adding new optional data structures to the input message.

向输入消息添加新的可选数据结构。

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You can pass an optional data object and callback function if you need them.

如果需要的话，您还可以传递一个可选的数据对象和回调函数。

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In the text payload, a section called UDH (User Data Header) is optional but defines lot of advanced features not all mobiles are compatible with.

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It will support 4G LTE data and voice through an optional chipset.

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An optional global positioning system unit encodes geographical meta data into your photos.

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