On 10/31/2013 10:36 AM, Pavel314 wrote:
....

I've seen other 220 volt plug configurations; some have an L-shaped
blade instead of the round pin, others have four blades in a
circular pattern which lock when turned, etc. Is there any practical
reason forall these variations?

Yes. There's the 20A/15A rating differences as well as to prevent
inadvertent use in wrong voltage circuit plus ensuring polarity for the
cases where it matters, the twist-lock types are for applications like
overhead outlet where there needs to be a mechanical connection to keep
in socket, etc., etc., etc., ...

While there are some duplications/redundancies, much of that is for
historical reasons as later standardization became more rigorous.

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