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CATX4000: Learning the EDID

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


Unlike digital video interfaces, analogue interfaces like VGA do not detect when the monitor has been changed.  They typically only detect the monitor and read the EDID on boot.  Therefore, a reboot would be required to ensure that the host is reading the expected EDID.  There are of course exceptions, particularly on some laptops where they do detect the presence of an external monitor.

Out of the box, each CATX-Module has a built-in EDID that supports a default set of resolutions. When the host computer boots, it reads the EDID directly from the CATX-Module, which determines which resolutions are available on its operating system.

To update the CATX-CAM Module with the actual monitors EDID, which may offer different resolutions, the monitor, CATX4000 (AVX4016/AVX4024), CATX-CAM Module and host need to be switched on in a particular order to pass the EDID down the chain. The following instructions assume that the cables are physically connected between each of the components.


  • Connect the Monitor to the local VGA port of the CATX4000.
  • Connect the CATX-CAM to the host computer and CATX4000.
  • Power on the Monitor
  • Power on the CATX4000.
  • The CATX4000 will read the EDID from the Monitor.
  • Power on the host computer.
  • The host computer will, in turn, provide power to the CATX-CAM Module, either via the PS/2 connection or USB depending on the model.
  • The CATX-CAM Module will read the EDID from the CATX4000 and store it locally.
  • The host computer will then read the EDID directly from the CATX-Module.

Further Information

By default, the CATX switch will read the monitors EDID on power up. If you do not want the learned EDID to change, you can change this option through the local OSD menu.

  • Open the OSD menu, press and hold CTRL+ALT+M
  • Press F1 to enter the Configuration Menu.
  • Press F1 again to enter the Advanced Options
  • From the menu, choose DDC Options

There are two options for DDC Refresh, AT START and DISABLED. The default setting is AT START. If you change the setting to DISABLED, it will not update the learned EDID on power up.

Page last modified on Wednesday November 13, 2019 12:35:13 GMT-0000