MOTU MIDI Express 128, USB MIDI Interface, 8 Independent inputs and outputs, 128 MIDI channels, Simple expansion by any M.O.T.U. MIDI Interface, Powered by the USB bus, there is no separate power supply required, Ultra - fast USB connection, Supplied driver: Mac OS9, Mac OS X, Windows ME / 2000 / XP / Vista, 19 ""/ 1U