Despite the rise of digital interfaces, DTMF keys remain widely used in IVR (Interactive Voice Response) systems, remote control via phone lines, and even some two-factor authentication methods.
Each key is assigned a unique pair of frequencies: one low-frequency tone and one high-frequency tone. When a key is pressed, the device generates a superposition of these two sine waves. dtmf key
The standard 12-key pad uses four low and three high frequencies . Despite the rise of digital interfaces, DTMF keys