The HW allows any combination of recording, playback - to/from modem and to/from speaker/mic at the same time. It's possible to implement a lot of interesting f

The HW allows any combination of recording, playback - to/from modem and to/from speaker/mic at the same time. It's possible to implement a lot of interesting features that way, like DTMF menu system on incoming calls, with or without monitoring of the other side, etc. I have it documented here: https://xnux.eu/devices/feature/audio-pp.html https://xnux.eu/devices/feature/audio-pp.html So it's certainly possible.