56K technology is a bit touchy about the conditions it will work under. People's connection speeds vary widely depending upon circumstances. We have a basic write-up on this at:
http://home.visi.com/support/modems/56k.html
And we have some initialization strings for modems defined on line at:
http://home.visi.com/support/modems/init.html
Here is a site with some links to modem manufacturers and other off-site support:
http://home.visi.com/support/offsite/modems.html