The term was first used by AT&T in commerce on July 5, 1960, and was introduced to the public on November 18, 1963, when the first push-button telephone was made available to the public.
As a parent company of Bell Systems, AT&T held the trademark from September 4, 1962, to March 13, 1984.
DTMF was first developed in the Bell System in the United States, and became known under the trademark Touch-Tone for use in push-button telephones supplied to telephone customers, starting in 1963.
The term was first used by AT&T in commerce on July 5, 1960, and was introduced to the public on November 18, 1963, when the first push-button telephone was made available to the public.
As a parent company of Bell Systems, AT&T held the trademark from September 4, 1962, to March 13, 1984.
Until out-of-band signaling equipment was developed in the 1990s, fast, unacknowledged DTMF tone sequences could be heard during the commercial breaks of cable channels in the United States and elsewhere.
Bell's Multi-frequency signaling was exploited by blue box devices. Some early modems were based on touch-tone frequencies, such as Bell 400-style modems. ==See also== Selective calling Special information tone Cue tone ==References== ==Further reading== ITU's recommendations for implementing DTMF services . Frank Durda, Dual Tone Multi-Frequency (Touch-Tone®) Reference, 2006. ITU-T Recommendation Q.24 - Multifrequency push-button signal reception Telephony signals Broadcast engineering
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