ADDER X-KVM/P, Инструкция по установке и использованию, Страница: 43 / 57

AdderLink X-Series Installation and Use Page 41
6. Configuring and using the skew
compensator
6.1 What is the skew compensator and why is it needed?
The skew compensator corrects the video colour split that is sometimes introduced
when a video picture is transmitted over twisted pair cables. Twisted pair cables are
typically constructed using four pairs of twisted wires. Each of the pairs of wires are
normally twisted at slightly different rates to reduce the crosstalk between the pairs.
This is highly advantageous for digital data transmission but can sometimes cause a
problem when the cables are used to carry video signals. The reason for this is that
three different pairs are used to carry the red, green and blue colour components of
the video picture. If the length of cable used is long enough and the twist rates
differences between the twisted pairs are large enough then there will be a
significant length difference between the wires that carry the different video colour
signals. This means that the colour signals will arrive at the X-KVM remote receiver
at different times and the colours on the video picture will appear to split causing the
picture clarity to be reduced. A typical characteristic of this colour split effect is a red,
green or blue shadow around bright white objects. The skew compensator removes
this colour split by deliberately delaying some of the colour signals so that all the
signals arrive at the remote receiver at the same time.
6.2 Can I predict if a skew compensator will be needed?
It is remarkably difficult to predict if a skew compensator will be needed because
twisted pair cables from different manufacturers have substantially different
characteristics. Although Category 5e and Category 6 cables typically have larger
twist rate differences than Category 5 cables there are several types of Category 5e
and Category 6 cables with low twist rate differences. With similar specification
cables, the colour split introduced by one cable may be four times the colour split
introduced by another apparently similar cable. What’s more, colour split effects
become more noticeable at higher screen resolutions. The reason for this is that the
pixel time on higher resolution screens is shorter and so a given colour delay
represents more pixels.
As a general rule, colour signal skew is more of a problem with higher specification
cables (i.e. Cat 6 / Cat 5e), longer cable lengths and higher screen resolutions. For