Is there any way to force my modem to use FSK?
Essentially, you need to configure it to operate in '300 bps' mode (though you may be able to squeeze higher speeds out of it; in the BBS days, we used run '300 bps' Bell 103J-compatible modems at 400 bps or even higher, as long as both sides know it and the quality of the conneciton and the modems is sufficient.)
I know there's an AT+MS= command, but I can't figure out the exact
> format for my modem.
It varies from chipset to chipset. Some modems (e.g. most USR modems manufactured in the past 20 years or so) have online help, while other information may be available on the web.
Geoffrey Welsh Never leave until tomorrow what can wait until next week.