[Asterisk-Users] Asterisk mangling faxes

Lee Howard faxguy at howardsilvan.com
Wed Mar 10 12:50:55 MST 2004

On 2004.03.10 10:18 Jim Sneeringer wrote:

> Do you know if there is other fax software that supports ECM?

Please forgive me for butting in on this thread, but I can't resist 
plugging HylaFAX.

Almost all fax software, including your WinFax 7.0, that supports Fax 
Class 2, Class 2.0, or Class 2.1 will usually therefore support ECM 
when the modem (DCE) itself supports ECM in those Fax Classes.  This is 
because the DCE does the ECM protocol work, and the software (DTE) 
doesn't really notice the difference.  Using Class 2 for faxing you are 
mostly subject to the mercy of the modem manufacturer for quality, so 
any bugs must usually be fixed in firmware.

Modems that I know of that support ECM in some fashion in Class 
2/2.0/2.1 are the MultiTech 5634 V92 family (MT5634ZBA-V92, ISI5634, 
etc.), the Digi AccelePort RAS, and the Eicon Diva Server.  There 
probably are a few more, but yes, this is a very short list.  Most 
modems do not support ECM in their Class 2 firmwares.

However, many (although not all, dare I say most?) modems support Fax 
Class 1 or Class 1.0.  In this mode the faxing is heavily dependent 
upon the DTE and thus the support or lack of support for ECM comes from 
the fax software.  Your average fax software that comes on a CD bundled 
with your modem is not going to support ECM.  Symantec (your WinFax 
people) recently purchased the rights to Procomm Plus (yes, if you're 
an old BBSer you may have this on your shelf), which does support ECM 
in Class 1, so maybe Symantec will get that ECM technology into WinFax 
eventually.  In the open-source world, HylaFAX now supports ECM in its 
Class 1 implementation in its current CVS HEAD (to someday become 

I don't know of many other Class 1 Fax Softwares that support ECM.


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