This topic might have a better name.
Magnetic Field Generator
Talk about it here.
The Daleks used a Magnetic Field Generator to shield their city on Skaro.
The Eleventh Doctor overloaded the magnetic field generators after he and Amy Pond found the Daleks had destroyed the human race in 1963, using the Eye of Time to alter history, so went to Skaro. The Daleks lost the Eye and never used it to alter history. (GAME: City of the Daleks)