Thanks for posting back with that info, LeeBur. My expertise with Radionics was extensive up to 1992, especially with the now-antiquated D4112, D6112, and D8112 Panels, all of which were programmed with the D5100 Programmer. In mid-1992, (just before my company sold its assets and left all service techs high & dry), Radionics starting its vendor lock-out with the panels and programmer, as I described above. So my real expertise in the programming protocols and hardware is nearly 30 years out of date.
As I recall, the D2212B Panel and D5200 Programmer came out a couple of years later, sometime in the mid-90s, and I did work with a few of them briefly, but not long enough to gain real expertise. I never had occasion (that I recall) to run into a lockout situation, but I assumed that Radionics continued that with their later panels. From what you tell me here, that assumption might have been unfounded. I still suspect that Radionics may have kept some lockout protocol, but they may have made it optional at the dealer's level. IIRC, I believe you have the option to program that panel through the keypad, a new innovation (at the time) for Radionics.
Again, thanks for updating me.