T38 Fax

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On 2/08/2011 1:02 AM, Robert Huddleston wrote:
>
> Anyone have any testing experience with T38 and HT-502 Grandstream?
>
> I just want to confirm that t.38 is working on this device.
>
> Thanks
>
>

Yes, it works.

I currently have latest firmware installed and it still works in T.38. I
am using UDP transport for this device as I seem to encounter problems
with TCP or TLS.

I am currently running Asterisk 1.8.5.0.

*Product Model: * HT-502 V1.1C
*Software Version: * Program– 1.0.5.5 Bootloader– 1.0.0.9
Core– 1.0.5.2 Base– 1.0.5.2

Some settings I have set and you may wish to check for the FXS port are;

/Force INVITE: / No Yes (Always refresh with INVITE instead of UPDATE)
/Send Re-INVITE After Fax: / No Yes

/VAD: / No Yes
/Symmetric RTP: / No Yes
/Fax mode: / T.38 (Auto Detect) Pass-Through
/Fax tone detection mode: / Caller Callee Caller or Callee
/Jitter buffer type: / Fixed Adaptive
/Jitter buffer length: / Low Medium High

You will need to ensure you are using redundancy mode instead of FEC.

I am able to send a fax via my voice provider seemingly without errors
even though ECM is not enabled, this is because redundancy mode is
working as expected on the outbound communication.

Unfortunately my voice provider only sends one data item in the incoming
UDPTL hence the occasional missed line.

Here is an extract from my sip.conf

[general]
.
.
t38pt_udptl=yes,redundancy,maxdatagram=400
.
.
[906]
; Grandstream HT502 FXS Port
; Analogue FAX Modem attached
type=friend
defaultuser=906
md5secret=c5bca943c9b0cc303c496fbf9d48a48e
call-limit=1
disallow=g722
transport=udp
qualify=yes
directmedia=no
host=dynamic
context=FAX-T38
faxdetect=no
deny=0.0.0.0/0.0.0.0
permit=10.0.0.0/255.0.0.0
permit=172.16.0.0/255.240.0.0
permit=192.168.0.0/255.255.0.0

Larry.