Well, I sent the 4020CF board back for exchange because I thought it was defective. It wouldn't answer the phone for a download call.
Got the new board and bench tested it, it worked fine, answered the phone by number of rings, PC link, and answering machine defeat, no problem. I program the board on my bench with PC link, test again, and all is well. The next day, I install the board, connect the phone lines, 4702 bell module, and 4701 phone line module. (Yeah, you need both of those peripheral modules to make the 4020CF an actual commercial fire panel.) Power the panel up, and enroll the modules. Call the panel, and....no answer. Tried again, no luck.
So it looks like the engineer nannies at DSC have disabled unattended downloading in the new s/w, v 3.54, once the panel detects the 4701 module. Yeah, I know you're not supposed to do it, but, well, I kind of like to make that decision myself. (The panel can still initiate a call if someone is at the keypad.)
The funny part is that DSC tech support doesn't know it. Well, the booger eaters who answer the phone don't anyway. Nor did the "senior tech" I spoke with.
Come to think of it, it's not that funny after all.
No more DSC "fire" panels for me.