The Collaborative International Dictionary of English v.0.48:

Ferranti cables \Fer*ran"ti ca"bles\, Ferranti mains \Fer*ran"ti
mains"\ (Elec.)
   A form of conductor, designed by Ferranti, for currents of
   high potential, and consisting of concentric tubes of copper
   separated by an insulating material composed of paper
   saturated with black mineral wax.
   [Webster 1913 Suppl.]