Triaxial cable is a type of cable, often used in communications, particularly in the television industry. It is called "triaxial" because it consists of three separate conducting elements, usually arranged in alternating concentric rings of conductor and shielded insulation. The shielding and insulation prevents the individual signals from the conductors from interfering with each other. Connectors for these cables are specially designed to prevent their accidental use with other types of connectors and cables.
The design of a triaxial cable, when viewed in cross section, resembles a bulls-eye. The center of the cable, or core, consists of a conductor, which is generally a single solid wire, but may be a braided wire. The core is encased in insulating shielding. Around this is another layer of conductor, which may also be solid or braided, followed by another layer of shielded insulation. A third conductive layer, which can also be solid or braided, is wrapped around the inner two layers, and the cable is finished with a final outer layer of shielding.
Several different grades of triaxial cable are available today. Common sizes of triaxial cable include 14 mm, 11 mm, and 8 mm, the measurements referring to their thickness. Resistance can vary as well, including 50 ohm, 75 ohm and 90 ohm cables, but the most common types have a resistance of 75 ohms.
The main difference between triaxial cable and typical coaxial cable is that triaxial cable can act as a power conductor as well as a signal conductor, and for this reason, triaxial cable is often used by the television industry to connect television cameras to their control units. With this type of cable, the control unit is able to provide power to the camera as well as to transmit and receive signals, all at the same time. Many venues that regularly host televised events have their own system of triaxial cables, enabling television crews to quickly set up for an on-location broadcast.
Triaxial cable is not generally used in home applications, but at least one company markets a signal distribution system for the home that can distribute signal to multiple home units. This type of system can combine multiple signal sources and then distribute them to several separate locations in the home. These units are designed for use with satellite systems and can combine and deliver closed circuit television, regular television signals, satellite signals and even standard FM signals. These systems are relatively unknown outside of Europe, however, as of 2011.