Whats the difference between an NTDI01 and NTDI02 TUs for Infi90 ?
My understanding, based on discussions with ABB and review of the manuals is that the main difference is that the NTDI01 Termination unit only allowed users to switche "neutral" with digital inputs, unless one used a special "circuit board" dipshunt that you could buy from ABB, which the engineering groups designed for project uses because they found applications which required that the input switch "hot" instead of neutral. The NTDI02 was a modified design of the of the unit that allows one to switch "hot" without requiring the use of a special dipshunt.
Note that because of application uses, both the NTDI01 and the NTDI02 units are both still offered. If you review the manual for the NTDI02, you should note that it says that "the NTDI02 is not a direct replacement for the NTDI01; however, it is a functional replacement for the NTDI01." Also, depending on your application using the NTDI01, "the NTDI01 and NTDI02 may not be interchangeable as the settings may not be the same."