Issues getting fax working outbound

[Chris A]

I have a customer who has to have outbound faxing from a physical machine (not their requirement but someone they work with so this won't change).

I am using a Grandstream HT801 device connected to my physical fax machine. I have created a fax extension within 3CX, added the FXS device and manually installed the config file on it. When trying to send an outbound fax I hear the fax machine actually dial, ring & send what sounds to be a fax tone. Odd thing is in Telynx I don't see any t38 SDP info coming from the 3CX side. I pulled a PCAP and see the Invite, 100, 180, 200 codes, an eventually an ACK from what is likely the recipients local IP. I have confirmed in 3CX fax transmission mode is set to T.38 & confirmed that setting in the HT801 device as well.

Any ideas?

 

[leejor]

You said you installed the provisioning file manually, which has me wondering about the particular configuration, in which it is operating. Perhaps you could provide additional information.

https://www.3cx.com/community/threads/information-to-provide-when-requesting-help.67558/


https://www.3cx.com/voip-gateways/grandstream-ht-fxs/

 

[Chris A]

When I mean manually I meant Step #7 of the guide you attached. I manually downloaded the config file and applied it to a freshly reset GrandStream HT801 device with the latest firmware installed.

I am using Windows 2019, 3CX v16, GrandStream is connected via VPN to my datacenter where 3CX resides, eventually to be moved to an SBC.

 

[leejor]

Are you able to test it NOT behind VPN (at the 3CX server location)?

 

[Chris A]

Are you able to test it NOT behind VPN (at the 3CX server location)?

My datacenter people might look at me odd if I wheeled a fax machine in haha. I guess I could but would be a huge PIA. Would be easier to get a SBC up and going as I am just testing all this in my lab before I take it to a customer and set it up in their system.

 

[cobaltit]

So if there requirement is a physical fax machine, your requirement should be to put in a PSTN line, or at least put in a FoIP service for this that bypasses 3CX. We've had good success with incoming fax to email via 3CX but we have zero outbound faxing through 3CX and anything important we either put on our FoIP service or put/keep it on PSTN depending on the level of importance for that fax.

 

[Chris A]

Was really hoping to get this working

 

[cobaltit]

Working and reliable are two different things

 

[Chris A]

For now I am okay with working haha

 

[leejor]

If possible (Fax machine settings allow), check to see if there is a VoIP option, or, set the default data speed to a slower rate.

 

[Chris A]

Unfortunately this one doesn't have any options as it is pretty basic. I am going to go try at the customers site with SBC and a full functioning MFP.

 

[NickD_3CX]

Just my 2 cents, Telnyx handles faxing in a "bypass" manner. This means that it is not guaranteed that T38 will be used, they will just pass on what the upstream provider negotiates. If that's T38, then a re-INVITE for T38 will go to your HT801, if not, then it will go over G711.

Now, increasing the success rates of in-band fax delivery, from my experience, you could try the following:

• Make sure in your Provider settings that G711 a/u are the only codecs you have (Telnyx default 1st codec is G722 in the template, also remove G729)
• Make sure the same 2 codecs are in the same order on the HT 801 device
• On the actual fax machine, put the transmission rate to the lowest possible.

The above in no way guarantees a 100% success rate, but should somewhat improve reliability.

The only way to solve the problem 100% is stop using a 30+ year technology and start using emails! (joking)

 

[Chris A]

Finally a helpful response not just someone saying it doesn't work Nick thank you for the details, this should hopefully point me in the right direction!

Trust me I don't want the fax machine either, unfortunately it is the requirement of multiple banks my customer deals with on a regular basis. Yes my customer is setup with email encryption, no the stupid banks won't accept that. We are having to over night documents to them at the moment. If the bank was my customer the story would be different. Unfortunately they aren't and my customer can't tell them to kick rocks because they only accept 30yr old tech

 

[Tou Xiong]

I had the same problem but with incoming faxes. I'm using a Grandstream GXW4216 and I had to change the mode from T.38 to Pass-Through then it started working.

 

[Alphabetic]

Once upon a time I was able to get a Brother MFP set up over an ATA adapter configured for STUN (was testing it).

The Brother MFP in question had a feature specifically for sending fax over voip called "overseas mode".
Im not sure if this increases or decreases the bit rate of the transmission.

But, in another story I attempted to do the same thing to another MFP (big momma of an MFP) and eventually gave up and I will never attempt to use a fax machine over VOIP again... that's the moral of my story.

Go for something like duoFAX.