You get to supply AT supplemental commands. Sorry but these will be modem and ISP specific.
However, here's a google groups where a S register was noted. Read both articles.
Windows ME / Ubuntu hoary 5.04
Modem zoom 3049c serial external
After installing Ubuntu and configuring network setting the modem hooked up and able to connect to websites.
Ubuntu on the web is very very slow compared to Windows
Ran c/net bandwith test as comparison to windows with the following results.
Ubuntu Windows ME
6.4 kbps 40.6 KBPS
These number are in the ballpark as it took 30+- minutes to load c/net home page,bandwith page and get return on results with Ubuntu.
When modem connects to Ubuntu the 56K indicator light is off. In windows it is on.
Is this a ISP,modem or software problem? How do I correct this?