I found an old rotary phone on a flea market and decided toplug it in. My land line goes through the cable modem, which doesn't support this old way of entering the phone number. What I need todo is convert the pulses of the phone to dual tone multi frequency tones. Step one is to reverse engineer the old phone interface. I connected a scope to the connected phone plug and got these signals:
Off hook, with speach.
Dialling a "4".
My initial thoughts is to connect these signals to a microcontroller to count pulses, and then let the microcontroller inject the right dialling tones on the line. First thing to do is to solder phone plug connectors to a perfboard to see if I can convert the 48V signals to logic levels (3.3V on 5V tolerant ports is my thought).