As other tips in this section note, if you don’t find an entry for your modem
in the Dial-Up Networking panel, you can add it through the custom modems
panel. You should be able to find the right string in the modem’s
documentation or on the manufacturer’s web site. If you don’t, the single
best place to look for init strings is at ModemHelp.org, which is a massive database
of strings for most modems in existence.
If you’re aware of other good sites with this type of information, let me know.