My users are experiencing echo sidetone issues on calls from the PSTN to their Polycom SoundPoint IP phones. Various phone models affected (301, 501, 650).
Tried dahdi-linux versions 22.214.171.124 and 126.96.36.199.
Tried asterisk versions 188.8.131.52 and 184.108.40.206
Done fxotune on the PSTN channels
Does not seem to occur on SIP to SIP internal calls.
Using OSLEC as echo canceller.
The person on the PSTN side does not experience echoing. It is only on the SIP/Polycom side. Users of Polycom phones are hearing their own voice echoing.