I bought three colors: white with blue, black, white (actually more white greyish than white). They are all perfectly calibrated. So they work great! What I love about them is that they are portable, you can take them anywhere, they are small, handy and so easy to use. You just press one button to turn it on. Tone is measured in real-time, so the numbers will fluctuate as the noise level changes during a call or when a tone is measured. If you want to capture a specific number and hold it while it's displayed, just press the hold button and the screen will freeze on that number so you can see it clearly. If you press MIN you will see the lowest value that has been switched on, if you press MAX you will see the highest value that has been recorded since switching on. My MOST AWESOME feature of this little guy is that you can very easily set it to start flashing an alarm when the volume reaches the level you set for it. For example, if you choose 80 decibels as the alarm sound level, you can set it in three simple steps and the next time you turn it on, it will always warn you by flashing on the backlit screen because it is not happy that the level exceeds 80 dB. This is great as you can see at a glance if the noise level is outside your acceptable range without having to worry about checking the numbers. This is especially important when working with children or others who do not want an audible alarm but can easily hear the flashing light and adjust the volume accordingly. I like it. To set an audible alarm check out the seller link they gave me when I was struggling to find info on how to set an alarm so now they have an easy step by step guide for you: https://www.amazon.com/vdp/a61e504a611945bbbdf992cbfbdaf854P.S. Из трех цветов, которыми я владею, черный и не совсем белый имеют рабочее оповещение, но я все еще пытаюсь установить его на белый и синий, я связался с продавцом, чтобы узнать, есть ли у него опция, и я обновлю этот обзор соответствующим образом in the near future. .
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