When the ProxmarkPro first boots, it will try to enumerate as a CDC modem over USB to allow the user to issue commands through the client software. The ProxmarkPro is primarily designed for use in the field without a PC.
To unchain your ProxmarkPro, place the power switch in battery mode and follow the instructions on-screen.
Once unchained, use the friendly on-screen menu to perform various tag operations. The menu is hierarchical and can be navigated using the up (↑), down (↓), left (←), and right (→) buttons.
Note: When you enter "Unchained mode", USB communication will not be permitted and the device will not longer show up as connected to your computer. To get USB communication back, all you need to do is exit unchained mode by pressing the left (←) until you get back to the boot menu.
More information on Unchained mode can be found here.
In addition to ProxmarkPro's primary functions, you can make several settings selections and perform tests while still in the field.