I was doing some digital housekeeping recently and came across an unfinished DTMF decoder that I started in Pd. DTFM is also commonly known as "touch tone" and is a signaling system traditionally used over telephony systems (and things like ham radio repeaters). I opened up the patch and found that it wasn't working quite right, so I tinkered and made something usable/releasable.
The help patch above shows decoding from a recording, live from the computers audio input (mic), and also from a fake DTMF dialpad that I made (which also uses my [dtmf~] abstraction). If you're watching a movie or listening to the radio and hear some gold old-fashioned touch tones, you can now decode the digits using this Pd abstraction. Good times.
Back in the 90s, I built several DTMF decoder circuits by hand, some that even interfaced wiht the computer's parallel port for logging. Wow, that was a long time ago. If you hunt around, I suppose you can still find DTMF decoder ICs, but they're certainly becoming harder to find. I guess these days, it makes sense to use the $2000 general-purpose computer on your desk/lap to do that work instead of $10 in parts. :-)
You can download this DTMF decoder (as well as my other DTMF related pd abstractions) over at my github repo: https://github.com/breedx2/pure-data. Let me know if you find them useful!