Coaxial cable
From Computer History Wiki
Coaxial cable is a kind of cable that is particularly useful for high-frequency signals. It consists of a central conductor, covered in a sheath of insulating material, and a conductive layer around that; this physical configuration is particularly useful for transmission lines. The outer layer is used both for a signal return, and is also usually connected to ground, both to protect the signal on the conductor from incoming noise, and reduce the interference radiated from the conductor.
