For the problem of converting pulses to tones, some time ago I made a small circuit that generates the DTMF tones directly inside the phone. It's basically an i

For the problem of converting pulses to tones, some time ago I made a small circuit that generates the DTMF tones directly inside the phone. It's basically an interface between the rotary dial and the phone line, based on a simple 8-bit PIC microcontroller powered from the phone line (actually coming from an ATA). The idea is to publish it as open source hardware as soon as I find enough time to document it... Downside is that you have to solder it (SMD components) and put it inside the phone...