Since I forgot my iBook Power Adapter in Oldenburg while driving to my parents, I searched for the adapter specs .. which was not easy.
Apple has “crossed” a cinch plug with a 2.5mm phone jack .. but according to some Usenet posts only the inner 2.5mm phone jack is needed for supplying power to the iBook.
See: Google Groups ibook klinkenstecker netzteil and especially here for the details – and most important: differences for Powerbook adapters (Sorry, search results in german only).
So .. where do I get a 2.5mm phone plug and a stabilized 24V power source .. today .. on a sunday. Oh well .. good thing my parents have a notebook, too 🙂