This is a software update for WILLIAMS AV DLT 400 units manufactured in January 2021 or later. The update enables the DLT 400 unit to function as a DLT 400-ACM unit, presumably adding or enhancing specific ACM (Advanced Communication Module) capabilities.
This digital download allows for a seamless upgrade of your existing DLT 400 system without requiring hardware replacement, provided your unit's manufacturing date is within the specified range.