MF J - 299有一个内建的电池检查线路。

MFJ-299 has a built-in battery check circuit.

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如果你确实决定来上摄影课，别忘了检查一下你的相机电池是充满电的。

If you do decide to come to the photography class, don't forget to look at your camera battery and make sure it's charged.

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每个月检查一下自己的火灾探测器，保证所有的电池都有充足的电量，警报铃的铃声可以让办公楼里的每一个人都听到。

Check your fire detectors once a month. Make sure the batteries are good and the sound is loud enough for everyone in the building to hear.

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