IBM THINKPAD X4 - Manual (Page 14)

7 The Ethernet connector is for connecting the X4 Dock to a
10BASE-T/100BASE-TX/1000BASE-T Ethernet LAN. The indicator on the
connector is the same as that on the ThinkPad computer.
Notes:
1. If your ThinkPad computer does not have the Ethernet connector, you
cannot use the Ethernet connector on the X4 Dock. You cannot use the
Token Ring cable for this connector. This connector can be used for the
10BASE-T/100BASE-TX/1000BASE-T Ethernet connection. However, if your
ThinkPad computer can only be used with the 10BASE-T/100BASE-TX
Ethernet, the connector can only be used for the 10BASE-T/100BASE-TX
Ethernet connection and not for the 1000BASE-T Ethernet connection.
2. If you attach your computer to the X4 Dock, use the Ethernet connector on
the X4 Dock, not the one on the computer.
8 The parallel connector is for connecting a parallel device.
9 The serial connector is for connecting a serial device.
10 The external monitor connector is for connecting an external monitor.
1-4 ThinkPad ® X4 Dock User’s Guide