PDT access, is a restricted level of access to the system that is generally only available to Engineer level personnel, and Nortel.
A load is a term used to identify the different software overlays that make up the user interface for the PBX.
Load (usually shortened to LD) 20 for instance is used to print information. LD 10 is used to program analog sets, LD 11 is used to program digital/IP sets, etc.