One late night many decades ago, I chanced upon a technical description of the Touch-Tone system ... channels to generate the dual tones, I bet I can dial the phone! I sprang out of bed and ...

Housed in a separate box are a microcontroller and a dual tone multiple frequency IC used to dial the numbers. These are patched into a PCB from a standard telephone. The result looks great and ...

The dialing technology in an analog telephone. Each digit has a physical button that transmits a different audio tone when depressed. Known as the dual-tone multifrequency (DTMF) system ...