Dual-Tone Multifrequency (DTMF)

Dual-Tone Multifrequency (DTMF) is another term for Touchtone, the registered trademark of AT&T. Dual-Tone Multifrequency produces an audible tone when you push a button. The tone is produced from a low frequency and a high frequency tone. There are two types of Dual-Tone Multifrequency, one for homes and businesses, and one for signaling the phone network itself.