PS/2 Port
Older ThinkPads typically feature a Female PS/2 Mouse Port, which can also support PS/2 Keyboards when used with a special PS/2 splitter cable.
Current ThinkPads no longer have a physical PS/2 port, but still have the logic integrated, all that is required is to attach the ThinkPad to a supported Dock or Port Replicator with a PS/2 port.