Pneumatics

Hi
This isn't probably the best place to post the question, but i don't know any 
other lego forums where i can post it...
I'd like to know how do the pneumatics work in lego... You know, those pumps 
and the air tank, etc etc etc... I don't have any lego set with pneumatics, so 
i don't have a clue on how they work... I'd really appreciate if someone could 
send me a link to a page explaining how they work, or if you have an e-book or 
know where to get it... thks a lot :)
João Pedro
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