https://www.pcgamer.com/redesigned-link-box-for-vive-pro-gains-a-power-button-loses-hdmi-connectivity/

With the Vive Pro on the horizon, it appears that HTC has also gone and retooled its Link Box accessory, which you can optionally use to connect your VR headset to your PC. The new version will add a power button to the mix, and lose the HDMI connector.

The point of the Link Box is to provide more power to the headset and enable Bluetooth connectivity. It's also a convenience for anyone who might have more than one headset—the original version also works with the Oculus Rift and mixed reality headsets, and we suspect the new model will as well.