Jeff, thanks for posting that link.
Per Steven R's advice, I've gone back to the store and tested all of the outlets with a remote, a TM751, and an AM466. Also took a SC546A Chime module. I tested with E first and then again with A. Good news is that all but 3 of the outlets will talk to each other. Of the 3, 2 are side by side at the front of the store and one is back in the bathroom. Those 3 outlets will receive ON but not Off commands and sending commands seems to be blocked to the rest of the outlets. Oddly, those 3 outlets talk with each other just fine. The SC546A Chime, which they do want to use, does not work anywhere.
I don't have a clue about those 3 outlets, will ask their electrician about that, but for the rest of the system I'm thinking that there's probably a lot of noise on the lines. The business is located in a strip mall and right next to a restaurant. Noise filters?? I just don't want to end up isolating the 2 breaker panels.
One other question I have is about the Industrial grade extension cords/power strips they have. The X-10 signals are blocked completely by them. Modules plugged into the same power strip can talk to each other but not to another outlet. I've never seen this before. Any ideas???
Thanks in advance, Doyle