as-i bus

i was reading about the as-i bus and got stuck with the bus.....it says that the supply and data are share on the same cable. how it works? can anybody explain this please?

thank you all for your help. cheers!

Good literature at : http://as-interface.net/

http://en.wikipedia.org/wiki/Asynchronous_serial_interface

http://www.as-interface.co.uk/

http://www.automation.siemens.com/m...communication/as-interface/Pages/default.aspx