On Wed, 26 Apr 2006, Russell McMahon wrote:

>> There is a clever plastic tongue inside that covers both holes and can
>> only be shifted if both prongs go in at the same time. Sometimes it is
>> acuated by the body (laterally).
>
> Some sockets here have shutter on phase and neutral (live and return) which 
> are opened by the longer earth pin being inserted first.

The 2-prong protector works by being wedged against dogteeth left or 
right inside if only one prong pushes it. Only if both go in at the same 
time does the tongue-like cover shift into a recess between the 
dog-teeth. It is very simple and very clever (and you can push against 
with with a nail and it won't open because the opening movement is 
aside, not in).

Peter
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