User guide

38 CAT5/5e KVM Extender Range
You can measure pair lengths with a LAN cabling tester (TDR) or view pairs
by stripping back a small piece of cable and viewing how tightly the pairs are
twisted. The most tightly twisted pair is the slowest (longest) and the loosest
pair the fastest (shortest). You can also observe relative delays using the test
card.
Some cables have a ‘3+1’ construction where three pairs closely match. The
fourth pair should be used for data and the other pairs sorted as in the above
table. Other cables have a ‘2+2’ construction where there are two sets of
dissimilar pairs. Put red and green on one set (tightest) and blue & data on the
other.
A suitable pair-swapping scheme is easily made using custom wired patch
cables at each end of the Interconnect cable.
Extender with Skew Compensation
In more extreme cases, you should consider using an alternative extender with
an in-built Skew Compensation feature such as the SDBX series. This allows
you to set independent delay values of up to 42nS on each color signal. Contact
Technical Support for details.
Patch Cable
To obtain optimal video performance with your existing setup, it is desirable to
have the green signal as the reference (slowest). This is because the human eye
is extremely sensitive to additional green distortion (introduced by delays).
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 appears to be improved. The main cable
should be wired according to EIA-568B as shown on page 13. Using a
crossover cable (at each end) will put the green video on the orange colored pair
and the blue video on the green colored pair.
EIA-568A wiring can also be used to the same effect. Contact Technical Support
for details.
The alternative SDBX range of KVM Extenders has been specifically designed
for the extension of high screen resolutions (1600x1200) over long CATx cables
(300m). SDBX Extenders have fully integrated skew compensation and independent
control of low frequency (LF) and high frequency (HF) cable equalization.