Triaxial cable, usually referred to simply as triax, is similar to coaxial cable except that is has a second conducting sheath and an additional layer of insulation. It is commonly used in television and professional video production, providing increased bandwidth and greater signal protection than coax.
Triaxial cable can use frequency-division multiplexing to transmit multiple data streams between a camera and controller (CCU). Coaxial cable can do the same thing, but triax is more robust and allow more information to be transmitted. Data streams typically include:
- Iris control settings
- Comms (intercom), often more than one channel
- Return video and audio (so the camera operator can see the program feed)
- Tally light, so the camera operator knows when their camera is on line.
- Camera power
- Other information about the camera settings, e.g. filter selection.