How anti-theft tags work - magnetostriction

Applied Science1 HN recommender · recommended in 1 month, 2017–2020

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explainer · general · evergreen · 2017–2020 on HN

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.

HN recommends it as an informative explanation of what those tags are, especially in threads about implants and RFID.

3 comments from Hacker News

@wolfgang422017-07 · in “Why People with Brain Implants Are Afraid to Go Through Automatic Doors”

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: ▶ this video

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@aftbit2020-12 · in “ACE: Apple Type-C Port Controller Secrets”

Those RFID tags are pretty minimal though. Basically just a thin trace antenna and silicon die directly molded into plastic. ▶ this 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.

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@sannee2018-11 · in “Alarm over talks to implant UK employees with microchips”

Are you sure these tags are RFID? I have only ever seen magnetostrictive tags [1] (but I don't buy expensive clothing...). [1] - ▶ this video

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