Zigzag plotter

In it's sixth version, the Doctor's TARDIS had a component called the zigzag plotter which looked like a car gear lever. The zigzag plotter only worked if the operator stood in a specific place while using it. The Eleventh Doctor talked Amy Pond through it's use to stop the TARDIS being thrown into the Time Vortex with only her inside. (DW: The Lodger)