Even when in use, they require a lot of maintenance—to adjust them from child to child, to keep them in good working order and to keep them clean.

即使使用了安全带时，孩子仍需要很多的保护，例如调整儿童之间的距离；保持安全带发挥作用；并保证清洁。

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The table folds up when not in use.

这桌子不用时可以折叠起来。

《牛津词典》

The language and style you use when making an oral presentation should not be the same as the language in style you use when writing.

你在做口头报告时使用的语言和风格不应该与你在书面写作时使用的语言和风格相同。

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Ships no longer in use contain dangerous materials which can be released into the environment when they are taken apart.

VOA: special.2009.04.27

And when you actually wanna store information on disk, can you actually use, as we'll see in a moment, magnetic particles.

当你想在硬盘中存储信息时，我们将会用到后面，我们会谈论的一种称之为磁性粒子来实现它。

哈佛公开课 - 计算机科学课程节选

In another example, you can use a "when" question in order to ask about the timing of a specific event.

在下面这个例子中，你可以用When 问句来询问一个具体活动的时间。

When 课堂 - SpeakingMax英语口语达人

Even more important, servers can be moved around, even when in use.

ECONOMIST: Virtualisation

When in use, headphones are a safe distance from the implanted device.

CNN: Study: Headphones could interfere with pacemakers

All kitchen appliances (except the fridge) remain unplugged, as do the printer, stereo, cell phone charger, and a few other electronics, except when in use.

FORBES: How a blogger brought her electricity bill down to $5