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 ...

Known as the dual-tone multifrequency (DTMF) system, the signal is a combination of the row and column frequencies of the digit key. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other ...

It takes the pulse signal generated by dial, converts it to a DTMF tone and sends that into the microphone to dial a number.” ...