Coaxial cable

Photo of a coaxial cable
A: outer plastic sheath
B: copper screen
C: inner dielectric insulator
D: copper core
Source: Wikipedia

Coaxial cables are used in cable television systems, among other applications, to deliver information very quickly.

Often referred to as 'coax', these cables are made of a conductive core wrapped in an insulator and a second conductive layer on top. These layers are usually wrapped in an outer insulating layer.

Coaxial cables were originally used because they could carry a much greater amount of data than traditional copper wires, enough to transmit many television channels. However, advances in ADSL technology for copper wires and the widespread use of fibre-optic cables have made this less important.

In television broadcasting, very thick coaxial cables called hard lines are used to connect the transmitter on the ground and the antenna or aerial on the tower. These hard lines are rigid and cannot be bent easily. However, they offer superior performance and less signal loss than normal coaxial cables.