spa8000 t38 faxing

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Perhaps this will help.

I have a SPA8800 which has 4 x FXS & 4 x FXO ports.

It took me some time to produce a working configuration.

In Asterisk I have the following where 904 is the extension of the
fax-modem and itsp is you VoIP Service Provider.



; Cisco SPA8800 FXS Port 4
; Analogue FAX Modem attached


I am including information from my SPA8800 for one of the FXS ports I
have a Fax Modem attached to, the key to getting it to work I believe is
the “FAX Tone Detect Mode”.

Audio Configuration

Preferred Codec: G711a Second Preferred Codec: Unspecified
Third Preferred Codec: Unspecified Use Pref Codec Only: no
Silence Supp Enable: yes Silence Threshold: medium
G729a Enable: no Echo Canc Enable: yes
G723 Enable: no Echo Canc Adapt Enable: yes
G726-16 Enable: no Echo Supp Enable: yes
G726-24 Enable: no FAX CED Detect Enable: yes
G726-32 Enable: no FAX CNG Detect Enable: yes
G726-40 Enable: no FAX Passthru Codec: G711a
DTMF Process INFO: yes FAX Codec Symmetric: yes
DTMF Process AVT: yes FAX Passthru Method: ReINVITE
DTMF Tx Method: AVT DTMF Tx Mode: Strict
DTMF Tx Strict Hold Off Time: 40 FAX Process NSE: no
Hook Flash Tx Method: None FAX Disable ECAN: no
Release Unused Codec: yes FAX Enable T38: yes
FAX T38 Redundancy: 1 FAX Tone Detect Mode: callee only
Symmetric RTP: yes

Supplementary Service Settings

CW Setting: no Block CID Setting: no
Block ANC Setting: no DND Setting: no
CID Setting: yes CWCID Setting: yes
Dist Ring Setting: yes Secure Call Setting: no
Message Waiting: no Accept Media Loopback Request: automatic
Media Loopback Mode: source Media Loopback Type: media


One thought on - spa8000 t38 faxing

  • Ok thanks I found the problem

    The spa8000 has some bugs with t38 which are fixed in the spa2102 but not in the 8000

    1. If the adapter starts with g711 It doesn’t switch to t38

    2. (This my problem) when it does go to t38 and the itsp asks for it to fallback to 9600 it doesn’t fallback so they never end up speaking to each other

    These were fixed in the 2102 according to the release notes

    Well now I hope I could get someone at cisco to look at it because I have more than a dozen 8000’s

    Thanks for your help