IHSE USA R434-91 Series SDLink Rackmount Hubs - Manual (Page 53)

Appendix D: Advanced Cabling Issues (Skew) 51
Appendix D: Advanced Cabling Issues (Skew)
The suggestions made in this Appendix should only be investigated if you
cannot obtain satisfactory image quality after configuring the Remote Unit (as
described in Section 3). The techniques described here are usually only
necessary when you are operating at the highest screen resolution (1600x1200)
with long Interconnect cables.
Dealing with Severe Skew
The SDBX KVM extender provides a maximum skew compensation of 42nS.
This is more than adequate for most cables. However, it may not be enough if a
particularly long cable is used that exhibits severe delay skew. In this case,
some of the procedures described below should be considered. In extreme
cases, you should consider using an additional external delay line (Model:
SDLY1) or an alternative CATx cable as recommended by Technical Support.
Green Delay
Introducing delays in the video signals inevitably may cause some distortion at
the highest screen resolutions (1600x1200). For example, it may result in pixels
being sampled twice on TFT screens.
The human eye is extremely sensitive to green distortion. To obtain optimal
video performance it is best to ensure that no green delay is required. You can
visually check the relative pair delays by viewing the test card (without any
delays applied). The two color bars on the left require delaying, but the color
bar on the right requires zero delay (slowest) and is the reference. Ideally, green
should be the reference signal.
If your system requires a large delay on the green signal, try using a
crossover patch cable at each end of the link (instead of straight patch cables
to connect to wall outlets). In many cases, the crossover should transfer the delay
requirement to the blue signal rather than green. The human eye is much less
sensitive to blue distortion and so video quality can be improved. Check the result
using the test card and adjust the delays accordingly. The main cable should be
wired according to EIA-568B as shown below.