The device consists of a DTMF decoder attached to the headphone jack of a cheap handy talkie. When a DTMF tone is received, a NodeMCU connected to the decoder calls an IFTTT job to echo the key to ...
But the basic encoding circuit remained very much the same. On the receiving side, DTMF tones are easy to decode — at least now. We’ve got DSP chips to do the job all in one package ...
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