[asterisk-users] fax / t38 gateway

[Brendan Martens]

On Oct 24, 2008, at 12:49 PM, Wilton Helm wrote:

> I've been following this thread and trying to sort out what is  
> wanted, what is available, and why.  Comments to the following would  
> be appreciated and might be useful to others.
>
> 1.  Why would anyone originate a FAX via VoIP?  If it has to go  
> through a bunch of translation steps at both ends, it would seem  
> better to simply scan the document (assuming it isn't in electronic  
> form to begin with) and attach it to an E-Mail.

Because I don't want to pay to have one single POTS line running into  
my office when it's sole purpose is for fax. I would much rather get  
that fax into my asterisk in some intelligent manner and have one less  
company to pay.
>
> 2.  Why would anyone terminate a FAX call coming through Asterisk in  
> a FAX machine?  Isn't there a way to capture it electronically?  If  
> so, it seems that putting the electronic documents in a queue where  
> people can open them, save them, and if they wish, print them would  
> be much more useful (and planet friendly, since a lot aren't worth  
> putting on paper).
I fully intend to do this, once the faxes gets into my * I email it  
off to someone.
>
> IMHO, there are only three realistic needs:
>
> A.  Electronic end to end document transfer which is best done with  
> E-Mail and not telephony.
As others have already mentioned, faxing is still around due to user  
ease and legal reasons. : (
>
> B.  Receipt of FAX from outside (old school) sources, which is best  
> done electronically.
I agree.
>
> C. Generation of FAX to outside (old school) destination, which  
> could be done either electronically or in the traditional manner.
My user base is fairly intelligent, so I will most likely be doing  
this, but we still have a need to be able to fax someone outside our  
organization, for that reason we still must have a reliable way to get  
faxes to plain old fax machines. I hope to do this with a solution  
that converts an email into a fax then sends it off into the normal  
analog tubes.
>
> If end to end FAX is desired, is there any reason why Asterisk  
> should treat it any differently than any other call?  The FAX  
> machines on each end generate and decode the information, VoIP is  
> simply an audio channel through which is passes.
Voip is a bit too loose of a term for describing this process when it  
comes to faxes. For the audio signals your speaking of to be  
recognized the standard analog audio range must come through clearly,  
lossy voice codecs hack that spectrum up to save bandwidth. While this  
is ok for humans, it kills the fax signal. This is what t.37 and t.38  
try to fix. You can go read up on them elsewhere, but basically they  
allow faxes to be sent in a packetized manner that can coexist well on  
a data network. The trouble obviously being that normal (most anyways,  
some support t.38... as Steve`Underwood has been saying, albeit  
somewhat buggily) fax machines can't understand this. This is why t.38  
must be decoded at some point before getting sent to a plain fax  
machine.

And that is why I am looking for a way to decode/encode my faxes with  
t.38, to avoid having to pay a phone company for one analog line that  
would get used at most a few times a week.
>
> I don't know what T38 defines or implies, but if it is anything  
> other than how to electronically decode a voice call that happens to  
> contain FAX information (rather than passing it on to a real FAX  
> machine) then I'm not sure what use it is.  It would seem to me that  
> the OP needs a way to electronically capture calls that turn out to  
> be FAXes.
Right, see above.
>
> Wilton
>



Anyways, I hope that helped you understand my desire to set things up  
how I am trying to. I'm sure a lot of people are trying to do this /  
have tried / have done it. Hopefully this thread will help those  
having trouble figuring out how this is done when they start  
googling. : )

Brendan Martens
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