Coaxial cable, or coax (pronoonced 'ko.æks), is a type o cable that haes an inner conductor surroondit bi a tubular insulatin layer, surroondit bi a tubular conductin shield. Mony coaxial cables an aa hae an insulatin ooter sheath or jacket. The term coaxial comes frae the inner conductor an the ooter shield sharin a geometric axis. Coaxial cable wis inventit bi Inglis ingineer an mathematician Oliver Heaviside, who patentit the design in 1880. Coaxial cable differs frae ither shielded cable uised for carryin lawer-frequency signals, such as audio signals, in that the dimensions o the cable are controlled tae give a precise, constant conductor spacin, which is needit for it tae function efficiently as a radio frequency transmission line.