https://en.wikipedia.org/wiki/Echo_suppression_and_cancellation
"Echo control on voice-frequency data calls that use dial-up modems may cause data corruption. Some telephone devices disable echo suppression or echo cancellation when they detect the 2100 or 2225 Hz "answer" tones associated with such calls, in accordance with ITU-T recommendation G.164 or G.165. " https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/voice/voiceport/confi guration/15-mt/vp-15-mt-book/vp-cfg-echo-canc.pdf "Additionally, G.165 defines the disabling of echo cancellers in the presence of 2100 Hz signals with periodic phase reversals in order to support echo cancelling modem technology (V.34, for example), which does not work if line echo cancellation is performed in the connection" /Tomas mån 2018-09-10 klockan 11:04 +0700 skrev Đích Kiều: > Hi everyone, > > Anyone working on Freedv on PSTN network ? I’m have a problem about > hybrid echo cancel in PSTN network. Half-duplex freedv work well. But > when I run full-duplex freedv in PSTN, hybrid echo cancel from PABX > make demodulator don’t work. Anyone can show me how to resolve my > problem? > > Thank you. > > Sent from my iPhone > > _______________________________________________ > Freetel-codec2 mailing list > Freetel-codec2@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 _______________________________________________ Freetel-codec2 mailing list Freetel-codec2@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freetel-codec2
