22. Modems
All external modems connected via a RS-232 serial port should work.
This includes external ISDN adapters, although some of the extended
features of external ISDN adapaters (such as multilink) may or may
not work.
Internal modems are another story, however. There are many so-called
"winmodems" available now. In fact, it seems that most PCI modems
are winmodems. Some of them do have drivers for Linux now, but many
of the drivers are often binary-only. (See the
note on binary-only drivers.) See
Linmodems.org for more
information on Linux-supported winmodems.
Note that there are external USB winmodems on the market now, so be
very careful when shopping for external modems.
Furthermore, many flash upgradable modems only have
flash programs for Win95/NT. These modems cannot be upgraded under
Linux.
A small number of modems come with DOS software that
downloads the control program at runtime. These can normally be
used by loading the program under DOS and doing a warm boot. Such
modems are probably best avoided as you won't be able to use them
with non PC hardware in the future.
Most 16-bit PCMCIA modems should work with the PCMCIA drivers.
CardBus modems are usually winmodems much like PCI modems. Your best
bet for now is to find a card that lists compatibility with DOS and
Windows 3.1.
All that said, if a modem is known to have a real UART (or hardware
UART emulation), whether it is ISA, PCMCIA, etc., it should work
under Linux.
Fax modems need appropriated fax software to operate. Also
be sure that the fax part of the modem supports Class 2 or Class
2.0. It seems to be generally true for any fax software on unix
that support for Class 1.0 is not available.
An exception to this is the Linux efax program which
supports both Class 1 and Class 2 fax modems. In some cases there
can be a few (minor) technical problems with Class 1 modems. If
you have a choice it is recommend to get a Class 2 modem.
See Appendix B Linux
Incompatible Hardware for specific cards known not to work with
Linux.
The following are other good resources for finding Linux-compatible
modems:
Most of the information below is from those sites.
Other useful documents include the following:
Below is a very incomplete list of modems
currently known to work under Linux.
The following is old information and may not be entirely correct. It
may be removed in a future revision of this document.
Digicom Connection 96+/14.4+ - DSP code downloading
program
here
Motorola ModemSURFR internal 56K. Add a couple of line
to RC.SERIAL to account for IRQ and ports if they are
non-standard.
ZyXEL U-1496 series - ZyXEL 1.4, modem/fax/voice control
program
here
ZyXEL Elite 2864 series - modem/fax/voice control program
here
ZyXEL Omni TA 128 - modem/fax/voice control program
here
Also multimodem cards are supported by Linux.
The following modem is mentioned not to be supported
Take our 
