Apple PowerBook (Duo 270C) - Manual (Page 269)

4. If you are using an external keyboard or a mouse,
connect its cable to the Apple Desktop Bus (ADB) port
on the adapter. The port is marked with this icon: ◊
Since the floppy adapter has one ADB port, you’ll need to
chain devices together if you have more than one. For
example, you can connect a keyboard to the ADB port, and
then connect a mouse to the keyboard.
If you plan to use the computer’s battery as your power
source, the battery charge will last longer if you use ADB
devices designed for portable computers. These devices are
marked with this low-power icon: Á
If you plan to use your input devices with the power adapter
plugged in, it doesn’t matter which devices you use.
Chapter 13: Building a PowerBook Duo System 253