The AT command reference for your Power Macintosh 6500 56Kbps modem is located on your hard disk in:
Hard Disk:Applications:FaxSTF:ATCom56flex(apple).pdf
It is located on the Restore CD in:
Restore CD:Macintosh HD Files:Applications:FaxSTF:ATCom56flex(apple).pdf
The AT command reference for the 56Kbps modem in a Power Macintosh G3 can be found on the Modem Software CD in the Modem Scripts folder.
Note:
Apple cannot provide guidance on the selection of specific modem initialization strings or modem commands. The initialization strings that you use are a function of the type of modem you are calling. Most modems simply require a factory reset (AT&F1 in this case) to enable or reset the basic features of the modem. The selection of such commands is a function of what you are trying to do; your internet service provider is normally the best source of special modem requirements.