DTMF

DTMF (Dual-Tone Multi-Frequency) is the signaling system used when pressing keys on a telephone keypad, where each key press generates a unique combination of two audio frequencies. In accessibility contexts, DTMF input serves as an alternative interaction method for voice-based systems such as interactive voice response (IVR) systems, voice websites, and telephony-based services. DTMF is particularly important for users who may have difficulty with speech recognition systems — including people with speech disabilities, those speaking minority languages not well supported by speech recognition, or users in noisy environments. Many accessible phone-based services offer both speech and DTMF input to accommodate the widest range of users.