IBM THINKPAD X4 - Manual (Page 13)

Rear view
1 The security lock key is for locking the eject button.
2 The power jack is for connecting the ac adapter.
3 The security keyhole enables you to attach a mechanical lock to secure the
X4 Dock to a heavy object, such as a desk.
4 The keyboard/mouse connector is for connecting an external keyboard,
keypad, or mouse.
5 The Universal Serial Bus (USB) connectors are for connecting USB 1.1 and
USB 2.0 devices.
Note: When you attach a USB cable to the connector, make sure that the mark
shown in the drawing is to the upper side. Otherwise, the connector
might be damaged.
6 The modem connector is for connecting the X4 Dock to a telephone line.
Notes:
1. If your ThinkPad computer does not support the modem connector, you
cannot use the connector.
2. If you attach your computer to the X4 Dock, use the modem connector on
the X4 Dock, not the one on the computer.
About the ThinkPad X4 Dock 1-3