[Brad] over at LucidScience decided that it would be useful to have a DTMF decoder on hand, and got busy building one. His DTMF decoder box uses a CM8870 DTMF decoder chip, which you might assume ...
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 ...