DTMF (Dual-Tone Multi-Frequency)

Dual-Tone Multi-Frequency (DTMF) is a signaling system used for telephone communication. When you press a key on a telephone keypad, it generates a combination of two specific frequencies, one from a set of high frequencies and one from a set of low frequencies. This unique sound allows the phone network to recognize which key was pressed. DTMF is what enables interactive voice response systems, allowing users to navigate menus by pressing numbers on their phone. It's essential for features like voicemail access and automated customer service.