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Skew equalization
Skew exists between wire pairs when the physical length of one wire pair is
different from another. Skew affects the displayed image when the differential
length between wire pairs exceeds 2 feet, causing the timing of the red, green, and
blue video signals to appear out of alignment (horizontal registration errors). The
signals transmitted on the shortest pair are shifted to the left if you are viewing
white lines on a black background. A white vertical line on a black field can
appear as individual red, green, and blue lines that are close together; the signal
transmitted on the shortest wire pair leads the other colors and appears to the left
on the display. As the transmission cable length increases, the skew effect increases.
The MTPX Plus has a skew equalizer function that is available using SIS, the
Windows-based control program, or built-in HTML page control. The skew
function provides separate time delay circuits, on the red, green, and blue video
lines on the inputs and the outputs. Each time delay circuit can be independently
adjusted, from 0 to 62 nanoseconds, to properly align the red, green, and blue video
signals on the displayed image. When correctly set, the red, green, or blue video
signal on the shortest wire pair is delayed to properly converge the displayed video
image.
UTP cable test equipment measures and reports wire pair length. The report on
the various pair lengths can be used to properly equalize pair skew. If UTP cable
test measurement cannot be done, pair skew can still be equalized by viewing
a test pattern with a critical eye. Examine the test pattern for loss of horizontal
registration and, through a process of trial and error, equalize any pair skew.
Definitions
The following terms, which apply to all Extron matrix switchers, are used
throughout this manual:
Tie — An input-to-output connection
Set of ties — An input tied to two or more outputs. (An output can never be tied to
more than one input.)
Configuration — One or more ties or one or more sets of ties
Current configuration — The configuration that is currently active in the switcher
(also called "configuration 0")
Global memory preset — A configuration that has been stored. Up to 32 global
memory presets can be stored in memory. Preset locations are assigned
to the input buttons and output buttons. When a preset is retrieved from
memory, it becomes the current configuration.
All 32 global presets can be selected from the front panel for either saving or
retrieving.
Room — A subset of outputs that are logically related to each other, as determined
by the operator. The switchers support up to 10 rooms, each of which can
consist of from 1 to 16 outputs.
Room memory preset — A configuration consisting of outputs in a single room
that has been stored. When a room preset is retrieved from memory, it
becomes the current configuration.
MTPX Plus Twisted Pair Matrix Switchers • Introduction
1-7
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