Cisco ATA Configuration and Setup for T.38 and G711 Fax

We use this tutorial for deployment of Cisco ATAs for faxing.  Be sure to update the ATA firmware to the latest available, and set to static IP. When using DHCP these devices tend to stop working from time to time and require a reboot.

  • Select¬†Voice in the Menu Bar, and then select either Line1¬†or¬†Line 2¬†depending on which line you have used for your fax, then select¬†Network. Set the¬†Network Jitter Level¬†to¬†very high¬†and the¬†Jitter Buffer Adjustment¬†to¬†no.
  • Next, in the¬†Supplementary Service Subscription¬†section, select the following settings;¬†Call Waiting Serv¬†to¬†no¬†and the¬†Three Way Call Serv¬†to¬†no.
  • Navigate to the¬†Audio Configuration section¬†and enter the following settings to support¬†T.38 Fax Preferred Codec;¬†G.711u (USA)¬†or¬†G.711a (rest of the world).¬†Select¬†Use pref. codec only¬†as¬†yes,¬†Silence Supp Enable¬†as¬†no,¬†Echo Canc Enable¬†as¬†no,and¬†FAX Passthru Method¬†as¬†ReINVITE.
  • Click¬†Submit¬†to save your settings
  • Since you are are using the Cisco media gateway for PSTN termination; then Disable T.38 (fax relay) and Enable Fax using Modem Passthrough. For example:
    modem passthrough nse payload-type 110 codec g711ulaw. Next set fax rate to disable, and fax protocol pass-through to g711ulaw
    Note: If a T.38 call cannot be set-up, then the call automatically reverts to G.711 fallback.
  • Verify that your fax machine¬†BAUD rate¬†is set to a speed between 7200 and 14400. We suggest¬†9600.

Try to fax as a test and make sure it completes.