a question for those with technical pen knowledge --
i remember futzing around with some old school plastic rotring technical pens when i was a kid visiting some older cousins. i would mostly just draw/sketch/doodle with them, and it wasn't until years later when i got into fountain pens that i started reading up on rotring.
these days, rotring remains a favorite partly because of this nostalgia, but i'm really more interested in their fountain/ballpoint/rollerballs. i remain curious about those technical pens, though. can someone tell me what they were originally made for? i've read online that they are for architecture/design/technical drawings, but i think my cousins were only in high school, or maybe college. also, what's the difference is between rapidographs and isographs? it is simply that one uses cartridges and the other refills from ink bottles?