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CATX4000: Video Compensation

This article covers the AVX4016, AVX4024, AVX4016IP and AVX4024IP, also known collectively as the CATX4000.


The AdderView CATX4000 allows hosts to be placed up to 50m (160 feet) away and remote users to be extended by a maximum of 300m (980 feet). Long cable lengths can affect video signals, especially when higher screen resolutions are used. In order to eliminate any video signal degradation, all AdderView CATX4000 units and accompanying Adder X100 and X200 extenders provide effective software-based video compensation features.

Two main types of video compensation are provided within the AdderView CAT4000 installation, these are:

It is important to note that, providing the cabling arrangements do not change, the various video compensations need to be applied only once to each computer or remote user link. During operation, control of video compensation is fully automatic.

Always configure the compensation between the computer and AdderView CATX4000 switch first and then between the AdderView CATX4000 and remote unit. Failing to do it in this order will mean that the video quality/compensation will vary when switching between host computers.

CATX4000 VideoCompensation


  • Start by connecting a monitor directly to the CATX4000 switch itself.
  • On each of the ports, set the cable length on the OSD. See the 'Computer Video Compensation' section below.
  • Make sure that you can switch hosts and the video looks fine on the local monitor.
  • Adjust the video compensation on the X100 or X200 between it and the switch.

Computer Video Compensation

The video compensation for connected computers is achieved using the main menu. Although the compensation can be applied from any local, remote or global user port, it is best achieved using the local user port because this provides the most direct view of the computer output. The compensation is achieved simply by registering the link cable length, however, different cables can vary in their characteristics so it is often useful to ‘fine tune’ the compensation by eye.


CATx cables below 10m give very little loss and so it is not normally necessary to be concerned about setting any computer video compensation if short CATx cables are being used between the AdderView CATX4000 and the CAM for each computer

To apply the computer video compensation:

  1. Place a computer (connected via its CAM and category 5, 5e or 6 cable) into the highest resolution video mode at which it will be used.
  2. If possible, use a monitor and keyboard connected to the AdderView CATx local user port.
  3. Display the AdderView CATX4000 main menu and use it to select the appropriate computer. Note: You must highlight the computer name and press Enter to select it.
  4. Display the AdderView CATX4000 main menu again.
  5. Press F2 to access the compensation feature:
  6. Use the Up and Down cursor keys to increase or decrease the stated cable length, as required. Note: As you adjust the Length value, check the video image for signs of under- or over- compensation, especially to the right-hand side of any hard vertical edges of images.
  7. When the correct compensation has been applied, press Esc to quit the screen and save the settings.

Remote User Video Compensation

Video compensation for each remote user is provided by their Adder X100 or X200 modules, not by the AdderView CATX4000 unit itself. Using the Adder X100/X200 controls you can adjust the picture sharpness and brightness to improve the remote picture quality.


Accurate remote user compensation relies upon visual feedback from the screen image. It is therefore vital to ensure that the video images being sent out from the AdderView CATX4000 are as ‘true’ as possible. Ensure, using the local user port, that the video images received from the computers are correctly compensated BEFORE attempting to adjust the remote user(s).

Video compensation is best carried out when viewing high contrast images with vertical edges, such as black lines on a white background. When doing so, if you notice that the screen image is ‘fuzzy’ or ‘dark’ then the image controls may not be able to solve this condition


If the high contrast images exhibit shadows with separate colours, then there may be a skew problem which requires a different image adjustment (provided only by Adder X100AS/R and X200AS/R modules) - see the Remote user skew adjustment section for details.

To display a suitable high contrast image

The best way to clearly view the effect of sharpness and brightness adjustments is to display a high contrast image, with vertical edges, on the screen.

  • Open a word processor, type the capital letter ‘H’, or ‘M’ and increase the point size to 72 or higher. For best results, the background should be white and the character should be black.
  • A black shadow on the right of the character indicates under compensation.
  • A white shadow on the right of the character indicates over compensation.

CATX4000 VideoCompensation3


The Word processor method is accurate and quick. However, for the very finest video compensation, use the test pattern which shows both the skew pattern and a section of mixed size Hs (black on white and white on black).

If the image controls cannot provide a crisp image.
If, after adjusting the image controls, one or more screen images remain fuzzy or have coloured shadows you may need to use the Skew adjustment feature. Please see Remote user skew adjustment for details (Adder X100AS/R or X200AS/R modules only).

To apply the remote user video compensation

  • Ensure that the video image from the computer to be used has been correctly compensated. See Computer video compensation for details.
  • On the remote user keyboard (connected to an Adder X100/X200 extender), simultaneously, press the hotkeys (by default, Ctrl and Shift ) along with to enter configuration mode.

    The three keyboard indicators (‘Num Lock’, ‘Caps Lock’ and ‘Scroll Lock’) will now begin to flash in sequence. The speed of the sequence indicates the level of the sharpness adjustment currently applied: the slower the rate, the lower the level of sharpness being applied

CATX4000 VideoCompensation4

  • While viewing the displayed screen image, use the following keys to adjust the controls:

    Sharpness: Use the Up and Down cursor keys for fine adjustment, PageUp and PageDown for coarse adjustment. There are 255 sharpness levels (one coarse step jumps 10 levels). To autoset sharpness: Press to make the module calculate and apply an automatic compensation level - you can use this as a starting point for your fine tuning. Note: If the monitor goes blank and switches off (due to oversetting the sharpness adjustment) press the Home key to restore.

    Brightness: Use the Left and Right cursor keys for adjustment. There are 255 brightness levels.

CATX4000 VideoCompensation5

  • When no shadows are visible and the displayed images have crisp edges, press Enter to exit configuration mode and permanently save all settings. The new compensation settings will be stored, even when power is removed or if a complete reset is initiated. These settings should not require further changes unless the cabling arrangements are altered.

Remote user skew adjustment

The category 5, 5e and 6 cabling supported by the AdderView CATx consists of four pairs of wires per cable. Three of these pairs are used to convey red, green and blue video signals to the remote video monitor. Due to the slight difference in twist rate between these three pairs, the red, green and blue video signals may not arrive at precisely the same time. This is visible as separate colour shadows on high contrast screen images and is particularly apparent when using higher screen resolutions and some types of category 5e cables.

To alleviate this situation, the Adder X100AS/R and X200AS/R modules provide internal skew adjustment that can help to rectify the situation. The skew adjustment works by delaying or advancing the timing of any of the red, green or blue colour signals so that they are all delivered to the monitor at precisely the same time.

To use skew adjustment

  • Download the test pattern.
  • On the remote user keyboard (connected to an Adder X100AS/R extender), simultaneously, press the hotkeys (by default, Ctrl and Shift) along with Enter to enter configuration mode.
    The three keyboard indicators (‘Num Lock’,‘Caps Lock’ and ‘Scroll Lock’) will now begin to flash in sequence.

CATX4000 VideoCompensation6

  • As appropriate, press either the R, G or B keyboard keys to select the appropriate colour channel. Corresponding keyboard indicators will flash rapidly to show which channel is currently selected for adjustment:Num Lock for Red, Caps Lock for Green and Scroll Lock for Blue.

CATX4000 VideoCompensation7

  • Press the Left and Right cursor keys to retard or advance the timing of the selected colour channel respectively. On screen you will see a change in the position of the selected colour crosses (or colour bars) in relation to the other two.

CATX4000 VideoCompensation8

  • When the selected colour crosses (or colour bars) are correctly positioned, press Enter to exit that colour channel. The keyboard indicators will return to flashing in sequence.
  • If required, repeat steps 3 to 5 to select and adjust any colour channel until the vertical lines of the red, green and blue crosses are all aligned.
  • When all colours are correctly aligned on all video channels, press Enter to exit configuration mode and permanently save all settings.


Once you have made the skew adjustments, it may be necessary to re-adjust the image controls to attain optimum screen images.

Page last modified on Tuesday September 15, 2020 05:26:49 GMT-0000