You need a "hybrid network" to connect to the telephone system. You'll also need a relay to take it off hook, etc.
There can also be hundreds of volts on the line at various times, not to mention induced voltages during storms.
Once you've handled that, it should be fairly easy to generate the right signals and do handshaking. An RP2040 / raspberry pi pico should be more than adequate.
"The break-out board has been verified by tnt at CCC Camp 2023, where he successfully transmitted a Fax (using spandsp) via pulseaudio - alsa - usb-audio - iCE40 FPGA - AMR riser. Closing."
There can also be hundreds of volts on the line at various times, not to mention induced voltages during storms.
Once you've handled that, it should be fairly easy to generate the right signals and do handshaking. An RP2040 / raspberry pi pico should be more than adequate.