Can't help, but just wanted to mention that this was my first modem of all-time, and I really loved it! I forgot if it didn't have tone dialing! I have a couple of them somewhere in the storage bins, for old-time sake. It sure was a nice, cheaper alternative to other modems at the time (either an Atari 830 acoustic, plus cable, plus EXPENSIVE Atari 850 Interface Module, or an Atari 835 (which I've never seen), or even the Atari 1030.)
I remember it had a "variable" baud rate. It could go up to 450 baud. It made a lot of errors at maximum, though. However, I remember a friend sending me an EXE (or XEX in the modern parlance) of "Bruce Lee" at a fairly-reliable 400 baud. The Xmodem blocks only had to retry about every 10th-or-so!!!!