System information

Configuring Voice
Getting Started with Voice Services
Cisco SPA100 Series Phone Adapters Administration Guide 41
4
STEP 5 In the Audio Configuration section, enter the following settings to support T.38 fax:
• Preferred Codec: G.711u (USA) or G.711a (rest of the world)
• Use pref. codec only: yes
• Silence Supp Enable: no
• Echo Canc Enable: no
• FAX Passthru Method: ReINVITE
STEP 6 Click Submit to save your settings or click Cancel to abandon the unsaved
settings.
STEP 7 If you are using a Cisco media gateway for PSTN termination, disable T.38 (fax
relay) and enable fax using modem passthrough. For example:
modem passthrough nse payload-type 110 codec g711ulaw
fax rate disable
fax protocol pass-through g711ulaw
Note: If a T.38 call cannot be set-up, then the call automatically reverts to G.711
fallback.
STEP 8 If you are using a Cisco media gateway, make sure the Cisco gateway is correctly
configured for T.38 with the dial peer. For example:
fax protocol T38
fax rate voice
fax-relay ecm disable
fax nsf 000000
no vad
Fax Troubleshooting
If you have problems sending or receiving faxes, complete the following steps:
STEP 1 Verify that your fax machine is set to a speed between 7200 and 14400.
STEP 2 Send a test fax in a controlled environment between two ATAs.
STEP 3 Determine the success rate.