His DTMF decoder box uses a CM8870 DTMF decoder chip ... This was well and good, but he decided that an Arduino-driven LCD display would work far better. When he was finished, he had a compact ...

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 ...