asterisk users - Feb 2010 - Asterisk t38modem Fax gateway evaluation

Hi,

I am trying to fix a Asterisk setup with buggy (POTS) Fax machines. The
setup consists of the following components:

- A Digium TE121 for connectiong to E1 ISDN
- Debian box with Asterisk 1.4
- Grandstream GXW-4008 SIP ATA to which the Fax machines connect

I am aware of the problems with this type of ISDN <-> Asterisk <->
SIP
ATA <-> Fax machine installations, e.G. different "clock source"
of ISDN
and the ATA, ethernet timing issues, etc. So it's no suprise that i
encounter the usual problems: No reliable transmission of faxes, errors
and aborts with multiple page faxes, ...

Unfortunately the installtion is allready completed and purchasing new
hardware is not an option. Thus i have come up with the following idea
und need some small pointer if this is even possible:

remote <=whatever=> PSTN <=ISDN=> Digium <--> Asterisk
<--> t38modem
<=Ethernet=> Grandstream <=POTS=> local
 FAX                        E1     TE121        1.4
SIP       GXW-4008            FAX
machine
t38

Is it possible to decouple the internal Fax communication from ISDN
using t38modem or as an alternative "Fax For Asterisk", perhaps in
conjunction with HylaFAX? 

I was unable to find any current information about theese subjects on
the www. Most postings/articles are 4-6 years old and state that it's
impossible, but this was way before t38modem and "Fax for Asterisk". I
would be really grateful if anybody could come up with some current
information, howtows, etc.

Many thanks in advance

Daniel Leese

Hi!
> Is it possible to decouple the internal Fax communication from ISDN
> using t38modem or as an alternative "Fax For Asterisk", perhaps
in
> conjunction with HylaFAX? 
Look at HylaFax first, and I guess that you will be happier with leaving 
T.38 out of the picture. 

Do note that hardware can also be sold, not only bought. :-) A ISDN BRI-
analog adapter (example. DeTeWe TA33) is a typical partial solution for a 
stable solution - for those who focus on ISDN, and those who can sync 
internal BRI to external BRI/PRI.
> I was unable to find any current information about theese subjects on
> the www. 
Start here: http://www.voip-info.org/wiki/index.php?page=Asterisk+fax

Philipp

P.S.: It does help to understand your situation if you state in which 
country you are.

On 02/18/2010 03:40 PM, DLeese at LStelcom.com wrote:
> Hi,
>
> I am trying to fix a Asterisk setup with buggy (POTS) Fax machines. The
> setup consists of the following components:
>
> - A Digium TE121 for connectiong to E1 ISDN
> - Debian box with Asterisk 1.4
> - Grandstream GXW-4008 SIP ATA to which the Fax machines connect
>
> I am aware of the problems with this type of ISDN<-> 
Asterisk<->  SIP
> ATA<->  Fax machine installations, e.G. different "clock
source" of ISDN
> and the ATA, ethernet timing issues, etc. So it's no suprise that i
> encounter the usual problems: No reliable transmission of faxes, errors
> and aborts with multiple page faxes, ...
>
> Unfortunately the installtion is allready completed and purchasing new
> hardware is not an option. Thus i have come up with the following idea
> und need some small pointer if this is even possible:
>
> remote<=whatever=>  PSTN<=ISDN=>  Digium<--> 
Asterisk<-->  t38modem
> <=Ethernet=>  Grandstream<=POTS=>  local
>   FAX                        E1     TE121        1.4
> SIP       GXW-4008            FAX
> machine
> t38
>
> Is it possible to decouple the internal Fax communication from ISDN
> using t38modem or as an alternative "Fax For Asterisk", perhaps
in
> conjunction with HylaFAX?
>    
If you are trying to get from the PSTN to a FAX machine on an ATA 
neither Fax for Asterisk or HylaFAX will be of much help. You need a 
T.38 gateway function running in the Asterisk box to talk to the ATA. 
There are patches around for adding that function to Asterisk, but its 
not in the standard distribution.
> I was unable to find any current information about theese subjects on
> the www. Most postings/articles are 4-6 years old and state that it's
> impossible, but this was way before t38modem and "Fax for
Asterisk". I
> would be really grateful if anybody could come up with some current
> information, howtows, etc.
>    
4-6 was before Fax for Asterisk, but several options for faxing to and 
from a file, including t38modem, have existed for a long time. Digium 
has just been extremely slow integrating a T.38 gateway function into 
the Asterisk distribution.

Steve

Hi,

Many thanks Steve and Philipp for your input. I am compiling Asterisk
1.6  svn version right now and will try to integrate the T.38 Gateway
patches mentioned at https://issues.asterisk.org/view.php?id=13405 (I
have some Linux coding experience, but unfortunately my
telecommunication knowledge is severly lacking).

The ISDN PRI <-> Analogue Converter solution mentioned by Philipp is
impractical for my situation as the hub of the 2-wire POTS lines is not
in the same Building as the PRI.

I will let you her if my research bears some practical results, as this
seems to be something not very well established/documented.

Daniel