UD-ULTCDL use with USB Switch

I have a UD-ULTCDL and I’ve tried to use it with a switch so I can switch from my PC to Mac. It works fine without a switch but on the PC when I use a switch it only displays 2 monitors. I have tried many switches C’s and 3,0’s alike.


Hi Bobby,

Thank you for contacting Plugable! I’m sorry that the UD-ULTCDL isn’t working as expected with the USB switch, and I’d be happy to assist.

The HDMI ports on the rear-side of the UD-ULTCDL are labelled “HDMI 1”, “HDMI 2”, and “HDMI 3”. “HDMI 1” uses DP-alt mode to send video from the computer’s graphics processor to the display, whereas “HDMI 2” and “HDMI 3” use DisplayLink technology. Since the various HDMI ports on UD-ULTCDL use different technologies to send video, there may be different reasons for the issue you’re seeing depending on which of the HDMI ports isn’t working through the USB switch.

Most commonly in situations like this, the “HDMI 1” port will be the one not working. This is because many USB switchers do not support the full features of USB-C. More specifically, they often do not support DP-alt mode. All pieces between the laptop’s USB-C port and the dock must support DP-alt mode in order to pass video from the computer to the “HDMI 1” port of the dock. As a result, using a USB switch which does not support DP-alt mode would result in no video from the port.

With all this said, can you please advise which of the HDMI ports on UD-ULTCDL isn’t working as expected through the USB switch?

We’ve also written about this topic in detail in a blog post on our site. Here’s a direct link if you’re interested: https://plugable.com/blogs/news/all-you-need-to-know-about-plugable-switch-kvm-options-for-sharing-two-displays-and-more-between-two-computers

My apologies for the frustration, and thank you for giving us the chance to assist!

Plugable Technologies

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