Gefjun Disturbers mounted on a train.
A Gefjun Disturber is a device created by List of Code Geass characters#Rakshata Chawla to disable Knightmare Frames. It does this by disturbing the chemical and mechanical processes of the Knightmare's sakuradite and interior computers and gears preventing movement, which also disables all sakuradite-based technology. In addition, the field blocks the motion of hadrons, radio waves, and microwaves. It is first introduced in the first battle of Kamine Island. The Lancelot Conquista was developed with a certain resistance built in, however, it still makes its movement sluggish. Other than this, it has shown several other uses such as controlling the blooming effect of hadron-based weaponry as well as a defensive shield against hadron weapons.
Lelouch, who had several of these devices built onto a train, uses them to paralyze Jeremiah Gottwald by interfering with the Sakuradite in his bionic parts.