The Duo one is half that size, sort of square, see picture at

http://www.haun-online.de/Macintosh/HTML/duo230.html

My Service Guide mentions two flavors: a domestic version with RJ-11 connector, and an international version with a Mini DIN-8 connector. Perhaps someone with more familiarity can jump in and comment on external adaptors or whatever that connect to that DIN-8 version...