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I've just learned that electrical chargers with pins with holes in them are illegal in Australia. Here's what I'm talking about (ignore the one second from the left): Plugs with holes in them

What's the purpose of these holes?

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marked as duplicate by Connor Wolf, PeterJ, Passerby, Rev1.0, Daniel Grillo Jul 25 '14 at 10:35

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Ah, true - I didn't search hard enough :) interesting that there seems to be no definitive answer (retention sounds most likely, but someone else mentioned manufacturers disabling them by threading something through the holes). – Matt Lyons Jul 25 '14 at 2:32
It is to prevent someone else from using your devices without you approving: i.stack.imgur.com/6omPZ.jpg – jippie Jul 25 '14 at 5:34
up vote 4 down vote accepted

Retention mechanism: Some sockets have a spring loaded ball like structure (or variant) that engages this hole as a "detent" holding the plug in place.

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I think you might find that the ones with holes are re-using American style pins in the Australian position.
Australian pins are flat blades measuring 6.35 by 1.6 mm, 17.35 mm in length.
American pins are flat blades measuring 6.35 by 1.524 mm, 15.875–18.256 mm in length.

Interestingly, according to Wikipedia the hole doesn't really have a safety or electical function.

The small hole near the end of the power (non-ground) blades of some NEMA plugs is used for convenience in manufacturing; if present, it must be of specified diameter and position.1 Small specialized padlocks are available to fit these holes, allowing "lockout" of hazardous equipment, by physically preventing insertion of locked plugs into a power receptacle.

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