这个按钮是调节音量的。

This button is for adjusting the volume.

《牛津词典》

S5扬声器本身的控制面板上唯一的按钮是音量和静音。

The only buttons on the S5 speaker console itself are volume and mute.

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一个按钮控制大部分功能，包括接听电话和重拨，顶部边缘处有一个更小的按钮，用来控制音量和开启、关闭状态指示器。

One button handles most functions including call answer and redial, while a smaller button on the top edge controls volume and turns the status indicator on and off.

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