[asterisk-users] T.38 gateway ATA

Bryant Zimmerman BryantZ at zktech.com
Tue Sep 25 12:45:02 CDT 2012

 From: "Jeff LaCoursiere" <jeff at sunfone.com>
Sent: Tuesday, September 25, 2012 11:40 AM
To: asterisk-users at lists.digium.com
Subject: Re: [asterisk-users] T.38 gateway ATA

On 09/25/2012 10:34 AM, Sylvain Rochet wrote:
> Hi Jeff,
> On Tue, Sep 25, 2012 at 10:11:27AM -0500, Jeff LaCoursiere wrote:
>> Aha! That is what I am looking for. What firmware rev are you
>> using on the 3102?
> 5.1.12 on SPA8000, 5.1.10(GW) on SPA3102, there is probably new releases
> from Cisco, at the time I builded the T.38 network those were the latest
> releases.
> Here is my SPA3102 configuration that I changed or are relevant to 
> Network Jitter Level: very high
> Jitter Buffer Adjustment: disable
> Call Waiting Serv: no
> Three Way Conf Serv: no
> Echo Canc Enable: no
> Echo Canc Adapt Enable: no
> Echo Supp Enable: no
> FAX CED Detect Enable: yes
> FAX CNG Detect Enable: yes
> FAX Passthru Codec: G711a
> FAX Codec Symmetric: yes
> FAX Passthru Method: NSE
> DTMF Tx Mode: Normal
> FAX Process NSE: yes
> FAX Disable ECAN: yes
> FAX Enable T38: yes
> FAX Tone Detect Mode: caller or callee
> Note that my Asterisk is also configured to do Fax Tone Detect and ask
> my ATA to switch to T.38 before my ATA ask Asterisk to do so, thereforce
> I don't know if ATA Fax Tone Detection work correctly.
>> So if I am parsing you correctly, the asterisk server the ATA is
>> registered to is *also* a T.38 gateway, as you have directly connected
>> ISDN?
> Yes, this is also a T.38 gateway, my goal was to use T.38 from my ATA to
> Asterisk over my non-isochronous IP network. T.38 gateway is supported
> since Asterisk >= 10 and you don't need it since you are doing T.38
> passthru, but you need a device somewhere on the path able to detect the
> FAX preamble and ask to switch the data channel from ulaw/alaw to T.38.
> Sylvain

Thanks for the info Sylvain, that is just what I was looking for. Hoping 
to find that a lower model has the same feature set (don't really need 
the FXO port)... I am playing with an SPA122 right now, which seems to 
have the same options available you mention above. I'll load the latest 
firmware and report my experiences for posterity.




The Grandstream HT-701 (Single Port FXS ATA) is less than $30.00 from 

Working well right now. 

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