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How anti-theft tags work - magnetostriction
About this video
Applied Science explains how retail anti-theft tags work. A tiny magnetostrictive strip acts as a mechanical oscillator excited by a magnetic field, and magnetizing or demagnetizing it arms or disarms the tag.
Why it appears in the archive
HN recommends it as an informative explanation of what those tags are, especially in threads about implants and RFID.
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From the Hacker News discussion
Right, which is precisely why automatic doors are completely irrelevant. On a related note, here's an interesting and informative video from Applied Science on how these tags work: [VIDEO]
Read original comment ↗Are you sure these tags are RFID? I have only ever seen magnetostrictive tags [1] (but I don't buy expensive clothing...). [1] - [VIDEO]
Read original comment ↗Those RFID tags are pretty minimal though. Basically just a thin trace antenna and silicon die directly molded into plastic. [VIDEO] I still agree that it's amazing that our society can make functional structures with feature sizes in the nm/µm ranges so cheaply that we can afford to throw them away.
Read original comment ↗