User Interface Posted on 24th December 201513th January 2021 by ThePD (The Project Definition) User Interface refers to the HMI (Human Machine Interface). Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on LinkedIn (Opens in new window) Related Posted in Engineering and tagged control system, electrical, engineering, interface, safety. ThePD (The Project Definition) ThePD has been developing the Preferred Project Definitions based on the actual project execution and operation experiences and knowledge with the Project Language, and sharing with you daily basis.