Mgetty+sendfax is a collection of programs to send and receive faxes
in a unix environment using a class 2.0 or 2 (they're different)
faxmodem.  vgetty is an extension to mgetty, distributed with it, that
implements incoming voice call handling for certain voice-capable
modems, with new ones added regularly, if specs are available.

More specifically, the program `mgetty' allows you to use a class 2.0
or 2 fax modem for receiving faxes and handling external logins
without interfering with outgoing calls.  `sendfax' is a standalone
program which sends fax files.  `vgetty' is an extended version of
mgetty that can answer the telephone like an answering machine and
record a voice-mail message (if it finds one), or perform `mgetty's
fax or data call handling otherwise.  The mgetty+sendfax distribution
includes vgetty and a good-sized gob of utility programs that help you
manage faxes and voice messages.