A while back (probably two years, now) I was able to drill down and find the actual distributor for the actual manufacturer of one of these products, which as I said, all seem to share the same hardware and software, just in different form factor housings. At the time, I was intrigued by the very large number of features, including the Auto Attendant feature, and flexible numbering plan. You'll notice, if you compare these critters, that they all have extension jacks numbered 601 through 6xx, or 801 through 8xx. But according to the technical documentation, you can reprogram the ext's for any three-digit number. I wanted to use one as a "911" simulator for my fire department's education program, but in the mean time I found a cheaper solution.
Back when I was researching these, it became apparent that they had not gotten *all* of the North American features exactly correct: They were programmed to use ZERO, rather than 9, as the escape digit for seizing an outside trunk, and NINE was being used for the local attendant or OPERATOR. This is the way Japanese PBX's are/were generally programmed. When I finally got through to them, via email, I explained this conflict. Lo and behold, a few moths later, the product info on EBAY reflected the changes I had suggested. I can't take credit, because maybe a few other people brought it to their attention, but now they seem to be programmed correctly for North American dial plans.
