Cordolaine

A Cordolaine signal was a jamming signal that excited the copper atoms in bullets and caused their expansion within a gun barrel, rendering Earth-made guns useless. The Sontarans used this type of signal in their invasion of Earth. UNIT managed a counter-measure by using rad-steel coated bullets. This made the Cordolaine signal ineffective. (TV: The Sontaran Stratagem/The Poison Sky)

The Sinestrans had access to Cordolaine signals and used them to keep Scott Neilson from shooting them at New Scotland Yard in 1978. (AUDIO: The Sinestran Kill)