Pulse to Tone Converter

Hello,

I'd like to build a pulse to tone converter so that my father can run his old telephones on his current phone like. Unfortunately I'm not even sure where to start. Has anyone built one of these before, or could point me in the right direction on how to create the specific tones the phone line is looking for? I have some basic uC programming skills so if I knew what I needed to look for from the pulses, and what I need to output for the tones, it would be a great start.

Thanks.

Here are some ideas.

A pulse phone should work on a tone line, but I suspect it may not work on VoIP type services.

One other thing to watch out for is the REN or ringer equivalence that the VOIP device can handle. I think 5 REN was standard for a dial line. The old bells were 1 Ringer each. The NID has a 1/2 Ringer in it usually so the telco can run tests. Modern phones might use a 0.1 REN or less. I've heard that some VOIP system might be somewhere between 1 and 3.

If the VoIP box is too low, the phone won't ring.

Instead of actually doing the pulse to DTMF, you could just put a DTMF keypad nearby. I had a few in my time that you just held up to the phone mouthpiece when you wanted to dial. It had number storage too.