Coaxial cable has a central conductor surrounded by insulation, a metallic shield, and an outer jacket. The shield blocks interference. The geometry keeps the signal contained. Coax was used for telephone, television, and early internet. It still carries cable TV and broadband to millions of homes.

Coax has higher bandwidth than twisted pair. It can carry many TV channels and broadband data at once. RG-6 is the common cable for home TV and internet. RG-59 is older and thinner. Connectors include F-type, BNC, and N-type. Each has different uses and frequency ranges.

Coax characteristics

• Impedance: typically 75 ohms for video, 50 ohms for radio
• Shielding: protects against interference
• Bandwidth: higher than twisted pair
• Distance: can run hundreds of meters

Coax is being replaced by fiber in many networks. Fiber has more capacity and lower loss. But coax is already installed in most homes. Cable companies use it for the last mile. Hybrid fiber-coax networks run fiber to the neighborhood and coax to the home. The old cable still has life in it.