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Twisted pair - 4 pairs of 'twists'

by:Yatai     2020-07-21

Twisted is another type of CCTV cable

Twisted pair cable is a good alternative to coaxial cable if the length of the run is more than a few hundred meters. With twisted pair, runs of up to 600 meters can be used without any in-line repeaters.

Twisted pair transmission is also called balanced video transmission. The cable consists of 4 pairs of 'twists'. Because each pair of wire are twisted for the length of the cable, any electro-magnetic interference affects both wires equally. Both wires are subjected to the same interference, which is why it is called balanced transmission. Unlike coaxial cable, where the shield is grounded and commons the zero potential between the two points, the twisted pair video transmission concept does not common the zero potential between the two points.

If the two wires have similar characteristics, and enough twists per meter(the more the better!), they will be subjected to the same levels of interference and voltage drop. This allows for most unwanted noise to be eliminated at the receiving end.

Video balun - converts twisted pair to coax

In CCTV cameras usually have a BNC connection on the camera. You cannot directly connect twisted pair cable to this. Whats needed is a video balun on both the sending and receiving end. You still connect a coax cable to the camera, the coax cable then runs into a video balun, which transmits the signal over twisted pair. On the receiving end, another video balun is required to convert the signal to run through a coaxial cable.

Because twisted pair cables generally have 4 pairs per cable. This actually allows you to carry 4 video signals in the one cable. So you can connect to 4 cameras at one location with the run of one cable

Fiber optics - CCTV Cable

Fiber optics uses light as a carrier

Fiber optic transmission provides the best quality and is the most secure transmission media. Fiber optics have been used in long distance and overseas communications for decades. It has mainly been unused in CCTV cameras for fear of it being a 'touchy' technology and 'too expensive'. Fiber optics are becoming cheaper and simpler to install, so it's use will increase in the future.

Fiber optic transmission uses light to transmit data, rather than electric currents. The advantages of fiber are:

intercepting the signal, which would be easily detected

Fiber optics do have some disadvantages however. Terminating fiber optic cables requires special tools and better precision of workmanship than with any other cable. Also switching and routing of fiber optic signals is difficult. Fiber optic cables are also more fragile, stepping on the cables could easily damage them.

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