AMX NX-1200 Hardware Reference Manual page 40

9. After your PC restarts, you will see a list of startup settings that you can change. Press F7 to select the "Disable driver
signature enforcement" setting.
FIG. 47 displays the Startup Settings screen.
Startup Settings screen
FIG. 47
Your PC will reboot and you will be able to install unsigned drivers without any error messages.
NOTE: You can skip steps 1 - 3 by opening a Command Prompt and entering "shutdown /r /o".
Hardware Reference Guide - NX-Series NetLinx Integrated Controllers
Installation of the USB Gadget Serial Driver for Windows 8.x – 32/64-Bit Operating Systems
40