Kenneth Finnegan writes:
As part of a few projects I’m working on, I want circuits to be able to decode DTMF tones played over an amateur radio link for remote control. This can be done with a moderately powerful processor in DSP, but I opted to buy a handful of MT8870D dedicated DTMF decoder chips on eBay.
I wired together a quick little test circuit, and it worked right away.
Check out the video after the break.