The FaxBIOS is a specification created by the FaxBios Association in 1991.
It describes an API that can be used by programs that work with fax/modem
adaptors to send and receive faxes.

The FaxBIOS API is not universally-accepted, but it is used by some major
OEMs.  It describes several hundred services -- too many and too esoteric
to be covered by TECH Help!.  To get a copy of the printed specification:
COMPUSERVE:  Go FAXBIOS
Fax request:  (510) 540-5835
Mail request:  FaxBios Association
2625 Alcatraz Ave Suite 275
Berkeley CA 94705

  Check FaxBIOS Installed State  
The FaxBIOS uses a "universal" technique for installing the server and
for clients to check for installation.  It installs a MUX service (see
INT 2fH) but rather than picking a hard-coded MUX-ID, it uses an
algorithmic technique that avoid the possibility of other MUX processes
taking the same MUX number.

To test for the presence of FaxBIOS, your program should:

1) Start with a candiateMuxID of 80H.

2) if candiateMuxID >= ffH, FaxBIOS is not present; exit.

3) Invoke INT 2fH, with AH=candiateMuxID.

4) On return, if AL=ffH, check the string at DX:DI to see if it is an
exact match with "FaxBiosjpc" if so you've found the MUX-ID and
FaxBios services are installed.  Go to step 6.

5) If AL was not ffH or the string at DX:DI did not match, then
increment candiateMuxID and loop to step 2.

6) Try the Sys_Login service (for instance):
Set AH=muxID, AL=fbH
BX=0001H (the fn number for Sys_Login), and
DX:DI=addr of a 23-byte LOGIN_CANONICAL_REC structure
Invoke INT 2fH.  On return:
AL will contain ffH if FaxBIOS is still present and
CX will contains a FaxBIOS status code and
the structure at DX:DI will contain lots of data.

Notes:   The FaxBIOS provides lots of capabilities that would take
thousands of programming hours to reproduce.  For instance, it
converts a text file directly into a FAX.  It also provides
structures and file standards for phonebooks, activity logs, a
scheduling system, etc. (along with easy-to-use APIs to access
these data).

  When you examine existing fax/modem control programs, you will
often find a one-to-one comparison between features of the
control program and the features of the FaxBIOS API.

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INT 2fH xxfbH: FaxBIOS Functions