said by rugby:Apple's modem was not really a hardware modem, it was software based and had issues being consistent. We have a client running a mac mini server and a 4Sight Fax server that just keeps working with a USR modem.
I am running an older mini with 10.6 for a incoming fax on the Apple modem for several years now without any issues whatsoever.
The USR is running flawless on another mini with 10.8.