IBM Mini Dock, Port Replicator, Port Replicator II manual 4

(5) The Universal Serial Bus (USB) connector is for connecting a USB 1.1
device.
(6) The line-out jack, a jack 1/8 inch (3.5 mm) in diameter,is for connecting an
external stereo audio device.
(7) The line-in jack, a jack 1/8 inch (3.5 mm) in diameter,is for connecting an
external stereo audio device.
(8) The power jack is for connecting the ac adapter.
(9) The mouse connector is for connecting a mouse.
(10) The keyboard connector is for connecting an external keyboard or an
external numeric keypad.
(11)The external-diskette-drive connector is for connecting an
external-diskette-drive.
Note: If your ThinkPad computer does not support the external-diskette-drive,
you cannot use the connector.
(12) The parallel connector is for connecting a parallel device.
(13) The serial connector is for connecting a serial device.
(14) When you attach a mechanical lock to the security keyhole, the release
button is locked so that the computer cannot be removed from the ThinkPad
Port Replicator.
ThinkPad Port Replicator II
4ThinkPadPort Replicator, ThinkPad Port Replicator II, and ThinkPad Mini Dock: User’sGuide