Dual-Tone Multi-Frequency Signal Decoding

The dual-tone multi-frequency (DTMF) signaling system is being used in push-button telephone sets worldwide as an improvement over dial-pulse signaling in rotary telephones because of the high dialing speed which can be obtained. Besides telephone call signaling, DTMF is being increasingly used for interactive control applications such as voice mail, electronic mail, and telephone banking. Typically, in such applications, the user selects options from a menu by sending DTMF signals from the keypad of a push-button telephone.