<div dir="ltr"><div class="gmail_default" style="color:rgb(102,0,0)">To add some details to your call flow for clarity, I would write it as:</div><div class="gmail_default" style="color:rgb(102,0,0)"><br></div><div class="gmail_default" style="color:rgb(102,0,0)">
Sending FAX machine (T.30) ==POTS==> Local CO ==PRI/G711/T.30==> (PSTN) ==> VoIP Gateway with T.38 support ==IP/SIP/RTP/T.38==> (INTERNET) ==> Asterisk (with T.38 capable fax modem software) => .TIFF file</div>
<div class="gmail_default" style="color:rgb(102,0,0)"><br></div><div class="gmail_default" style="color:rgb(102,0,0)">I'm using ==protocol/stack==> to indicate the signalling/media methods, and (network) to indicate a large complicated routing network that isn't changing the datastream.</div>
<div class="gmail_default" style="color:rgb(102,0,0)"><br></div><div class="gmail_default" style="color:rgb(102,0,0)">In this diagram, note that:</div><div class="gmail_default" style="color:rgb(102,0,0)"><br></div><div class="gmail_default" style="color:rgb(102,0,0)">
1) POTS Analog to Digital (G711) conversion is done by the CO's SLIC</div><div class="gmail_default" style="color:rgb(102,0,0)"><br></div><div class="gmail_default" style="color:rgb(102,0,0)">2) The VoIP gateway when using T.38 does the G711/T.30 "Modem" conversion to T.38. A way to understand this is that it's like the serial port on the back of the old style modems, only the data is carried in RTP packets and called T.38. Portions of the T.30 decoding still have to be done by a software program inside or alongside Asterisk.</div>
<div class="gmail_default" style="color:rgb(102,0,0)"><br></div><div class="gmail_default" style="color:rgb(102,0,0)">The same sequence where T.38 is not used - just a conventional T.30 fax over G711:</div><div class="gmail_default" style="color:rgb(102,0,0)">
<br></div><div class="gmail_default" style="color:rgb(102,0,0)"><div class="gmail_default">Sending FAX machine (T.30) ==POTS==> Local CO ==PRI/G711/T.30==> (PSTN) ==> VoIP Gateway ==IP/SIP/RTP/G711/T.30 ==> (INTERNET) ==> Asterisk (with fax modem software) => .TIFF file</div>
<div><br></div><div>Note that the "asterisk fax modem software" has to include the entire T.30 stack including all the V.xx protocols, plus T.38 if needed.</div></div><div class="gmail_default" style="color:rgb(102,0,0)">
<br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Thu, Jan 9, 2014 at 5:38 AM, Chandramouli P <span dir="ltr"><<a href="mailto:crazymoonboy@yahoo.com" target="_blank">crazymoonboy@yahoo.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
Hi,<br>
<br>
I have some basis queries about the internal flow (conversion) and
architecture of FoIP. Please note that I have done enough research
on Internet to clarify my queries. But, I didn't get proper
information. I thought of sending you guys an email to clarify my
queries:<br>
<br>
I want to implement a real time fax service with Asterisk (FoIP with
Asterisk) using T38 protocol. For this, first I would like to clear
with the basic internal flow of sending fax over IP.<br>
<br>
<b>Send Fax -> Fax Modem -> Asterisk -> Receive Fax </b><br>
<br>
1) Please correct me, If I am wrong with the above flow.<br>
2) Can we consider "opalvoip" as Fax modem?<br>
3) Can we consider "SpanDSP" as Fax modem?<br>
4) Can we consider "HylaFax" as Fax modem?<br>
5) Can we consider "Fax Modem" as "T38 Gateway" in the above flow?
If not, where I need to put T38 Gateway in the above flow? Can you
please rewrite the flow? <br>
6) Can I use "opalvoip" as Fax modem in the above flow?<br>
7) T38 Gateway contains T38 Receiver and T38 Sender. Is it correct?<br>
<br>
Hence request you to find some time to reply and also reply in
inline.<br>
<br>
I look forward to hearing from you.<br>
<br>
Thanks in advance.<br>
<br>
Regards,<br>
Chandra.
</div>
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