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I am a 7 letter word. Most h...

I am a 7 letter word. Most humans want me. But they hate the first 4 letters of my name. If you get the 2nd, 3rd and 4th letter you are sick. The 5th, 6th and 7th is something with a charge. Who am I?

Correct answers: 129

The first user who solved this task is Sanja Šabović.

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Ultrasonic alarm

In 1953, the first U.S. patent for a burglar alarm operated by ultrasonic sound was issued to Samuel Bagno of New York City (No. 2,655,645) on a system for movement detection in a confined space by intruders or fire. It was manufactured as the Alertronic and first sold in Jun 1950. A sound source produced waves of 19,000 hertz, a frequency too high for normal human hearing. An intruder could be detected by the alarm by a difference in frequency of the reflected waves from the moving body (the Doppler effect). The device would then sound an alarm.

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