Clearer picture with a twist

Belden has introduced three NanoSkew Unshielded Twisted Pair (UTP) cables for video display aimed at IP and KVM applications.

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By  Simon Duddy Published  July 21, 2004

Belden has introduced three NanoSkew Unshielded Twisted Pair (UTP) cables for video display aimed at IP and KVM applications. The NanoSkew Brilliance VideoTwist UTP cables distribute component RGB video as well as providing for premise LAN wiring, which eliminates the requirement for two separate cables. The three cables are the 7987R – delay skew with 2.2nSec/100m (24 AWG twisted-pair), the 7988R – delay skew with 9.0nSec/100m (24 AWG bonded-pair) and the 7989R – delay skew with 10.0nSec/100m (23 AWG bonded-pair). Component RGB video systems transmit each part of a video signal through separate cables - one for red, one for green and one for blue. Transmissions require each signal to arrive simultaneously for a clear video image. The UTP cables feature different twist lengths for each pair. This difference causes a signal delay from pair to pair known as skew. The resultant skew limits overall transmission distance with current cabling restricted to distances of 328 to 600 feet. Propagation Delay Skew (skew) is the difference between the propagation delay on the fastest and slowest pairs in a twisted pair cable. Some cable constructions employ different types of insulation materials on different pairs. This effect contributes to unique twist ratios per pair and to skew. Skew is important because if the delay on one or more pairs is significantly different from any other, then signals sent at the same time from one end of the cable may arrive at the receiver at different times. While receivers are designed to accommodate slight variations in delay, a large skew makes it impossible to recombine the original signal. Well-constructed and properly installed structured cabling should have a skew less than 50 nanoseconds (nSec) over a 100-metre link. Clearly a lower skew is better and anything under 25 nSec is excellent. Skew between 45 and 50 nanoseconds is marginally acceptable for broadcast applications.

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