[asterisk-users] How to enable T.38 between SPA3102 PSTN Line port and ReceiveFAX app ?

Olivier oza_4h07 at yahoo.fr
Thu Nov 7 10:58:31 CST 2013

2013/11/5 Larry Moore <lmoore at omninet.net.au>

> On 5/11/2013 6:09 PM, Olivier wrote:
>> Hello,
>> I've got an analog phone which is currently receiving unsollicited FAX
>> calls from PSTN.
>> For learning purpose, I'm preparing an Asterisk/SPA3102 setup that would
>> let voice calls come in and out and translate incoming FAX calls to TIF
>> files (forwarded through email)).
>> My target setup is :
>> PSTN <-- analog--> SPA3102 Line Port <-- SIP --> Asterisk <-- SIP -->
>> SPA3102 Phone Port <-- analog --> Analog phone
>> When a call comes in, analog phone rings.
>> If callee answers and a fax tone is detected, then the incoming call is
>> sent by Asterisk to ReceiveFAX application which translates incoming
>> audio to TIF file.
>> My setup is working ok when I'm using ReceiveFAX in fallback mode (with
>> f option).
>> Then I would like to improve my setup letting ReceiveFAX negociate T.38
>> with SPA3102.
>> The trouble is SPA3102, as I configured it, seems to refuse T.38
>> negociation as I'm reading lines like this in Asterisk logs:
>>    == Using UDPTL CoS mark 5
>> [2013-11-05 10:36:50] WARNING[3061][C-00000007]: res_fax.c:1698
>> receivefax_t38_init: channel 'SIP/myline-0000000e' refused to negotiate
>> T.38
>> My question is:
>> Any hint on how to configure SPA3102 PSTN Line port so that it  would
>> accept to upgrade to T.38 ?
> The SPA3102 only supports T.38 on the FXS port, the FXO port uses G711 for
> a fax session.

That explains why I couldn't find the option  ;-)

> The Grandstream HT503 supports T.38 on both the FXO and FXS ports.

I never tried this one.
How would you rate this product ?

Is it easy to auto-provision an HT503 over TFTP or HTTP ?
Is it easy to localize FXO/FXS setttings for non-US countries (those having
played with a SPA3102 sure know what I'm thinking about) ?
Do it T.38 implementation works ok with Asterisk ?

> What problem do you have receiving a fax over G711?

I tried few calls in G711 fax mode and it worked OK but I rated T.38 as
more reliable solution in the long run and in general.

> Larry.
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