| Preferred Codec |
G711u |
μ-law — required for fax pass-through |
| Second Preferred Codec |
Unspecified |
|
| Third Preferred Codec |
Unspecified |
|
| Use Pref Codec Only |
no |
|
| Use Remote Pref Codec |
no |
|
| Codec Negotiation |
Default |
|
| G729a Enable |
yes |
(Should be no for fax-only — G.729 mangles fax tones) |
| Silence Suppression Enable |
no |
⭐ Correct for fax — suppression breaks T.30 handshake |
| G726-32 Enable |
yes |
|
| Echo Canc Enable |
yes |
|
| FAX V21 Detect Enable |
yes |
Detects V.21 fax handshake tones |
| FAX CNG Detect Enable |
yes |
Detects "calling fax" tone |
| FAX Codec Symmetric |
yes |
Both legs use the same codec during fax |
| FAX Passthru Codec |
G711u |
μ-law pass-through path |
| FAX Passthru Method |
NSE |
Network Signal Event triggers codec switch |
| DTMF Process INFO |
yes |
|
| DTMF Process AVT |
yes |
|