Dial-up ISP-in-a-box on o2 Box 6431 - lantiq fxs asterisk connection quality issues

I have compiled the latest openwrt git (with USB 56k modem support, asterisk, asterisk-chan-lantiq and mgetty) for my o2 Box 6431 and am trying to get two 56k dial-up modems to connect to each other.
This is for a Slovenian Computer Museum project I'm working on as a volunteer.

The issue is, the connection quality and the resulting data rate is extermely low (2400 bps). (Here is the recording of the handshake.) Ping from OpenWrt to client machine works (1000-2000 ms), but that's about it.

  • Is my extensions.conf a good way to directly connect the two FXS ports? It does work but maybe some with more asterisk experience can suggest a different method I can try.
  • I have tried different settings and codecs in lantiq.conf but was unable to get any improvements. I experimented with rxgain/txgain and there were some improvements - if I increased them to around 7, sometimes I would get a 28800 bps connection, however it would soon drop due to it still being of bad quality
  • Then I have tried some more changes in lantiq.conf according to the documentation (Google the following to get it, including quote marks: "Pass-Through Mode" "tapi" "infineon") with no improvement
  • I have also contacted mr. Stefan Koch, the last maintainer of asterisk_channel_lantiq but have not received a reply yet :frowning:

What I am planning to try next:

  • I have ordered a different pair of TAE to RJ11 adapters
  • I might consider obtaining a different lantiq-based router with 2 FXS ports to test there

Any feedback/suggestions welcome! Thanks :slight_smile:

Perhaps use an analog PBX to provide the two FXS ports?

Thanks, but I specifically want to have an all-in-one setup with as few extra "boxes" as possible.