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 ...

The 35-Type station dial. Source: The Beatrice Company Bell Labs conducted exhaustive research to determine the best methods for tone dialing. They settled on a DTMF system for the control tones ...

Detects the presence of a single tone at a specified centre frequency. Features 16-bit data samples, programmable tone frequency, adjustable detection bandwidth and a high performance Digital Down ...