Solved Faxing with ATA

[sevenvoip]

Hello all,

I have a Grandstream ATA 812 device that I am using for faxing. I can receive faxes on my number, but I am unable to send. I reached out to my SIP provider (TelNyx) and this is what they replied with...

"The invite you're sending g722 seems to be the preferential codec you are sending. Fax generally isn't supported over g722. We would recommend removing this codec from your invite or have PCMU(g711) and PCMA as the first preference codec. Fax tones work best with G.711 (for which they were designed). The only codecs for fax are G.711 mu-law and A-law. Better, sometimes, is for customers to use T.38 for fax transmissions. Some fax calls may work with G.722, but reliability should not be expected."

My question is, is there a way to send that g711 codec per number? I'd prefer my other numbers at that site go to TelNyx with g722.

 

[leejor]

My question is, is there a way to send that g711 codec per number? I

The codec will be first selected (suggested) in the originating device. So... if the ATA you are using is only used for Fax calls, then there thould be no reason that you cannot eliminate all but the G711 codec. I have not seen a device that associates a Codec with a called number. As long as G711 is available, at the other end (and along the way...TelNyx), then that is what will be used for the fax call. It won't affect other calls on 3CX.

 

[sevenvoip]

So you're saying that I can set the ATA to only send g711?

I thought this was a 3CX setting as I know you can set it under the SIP Trunk

 

[sevenvoip]

Found it on the ATA. I will test and keep you updated. Appreciate the quick response.

 

[sevenvoip]

Still failing to send and I keep getting a "User Busy" on my fax machine. I see the fax hitting our hosted PBX, and I see it hitting our SIP provider. I am reaching out to them for more info.

 

[NickD_3CX]

Hi there!

Quick question, if you Grandstream ATA connected to your 3CX installation via SBC?

 

[sevenvoip]

Yes, it is actually

 

[sevenvoip]

This is what my SIP provider sent me after doing a deep dive…

“
For the sample above, we keep sending you T.38 signals, specifically our "DIS" (Digital Identification Signal) message. However, we have not received any response from you.

The destination then ended the call, most likely due to not receiving anything.”

 

[NickD_3CX]

This is most likely related to an issue we have detected in the SBC that we have already addressed in the new version, that we plan on releasing pretty soon.

I'll PM you just now to verify this with you.

 

[sevenvoip]

I have the latest version of SBC and PBX.

SBC: 18.0.27
Raspberry Pi

PBX is Raspberry Pi
PBX: 18.0.1880

 

[NickD_3CX]

For anyone else having an issue with Faxing, via an ATA/FXS going over an SBC, on V18, when using a provider that uses T.38 for faxing, the new SBC version will solve this.

PM me so we can double-check.