[technofiend]

Electrically I don't see how that works since there's no interruption of the metal pin inserted into the socket like you see on a tip/ring headphone plug. Unless there's a mechanical process that energizes the live side of the inserted plug after a certain depth?

[krastanov]

No mechanical process, the wall socket is depressed in the wall, so that by the time any metal prongs connect, the prongs are hidden.

[n3k5]

You have to look at the plug in combination with the socket.

https://en.wikipedia.org/wiki/Schuko#Safety_features