Apple PowerBook (Duo 270C) - Manual (Page 257)

4. If you are using a keyboard and/or mouse, connect it to
the Apple Desktop Bus (ADB) port on the Duo
MiniDock.
Since the minidock has one ADB port, you’ll need to chain
devices together if you are connecting more than one. For
example, connect a keyboard to the ADB port, and then
connect a mouse to the keyboard.
5. If you are using an external floppy disk drive, connect
its cable to the floppy disk drive port (marked with the
icon H).
continues .
Chapter 13: Building a PowerBook Duo System 241