Page "Dual-tone multi-frequency signaling" Paragraph 6

AT & Ts Compatibility Bulletin No. 105 described the product as " a method for pushbutton signaling from customer stations using the voice transmission path.

" In order to prevent consumer telephones from interfering with the MF-based routing and switching between telephone switching centers, DTMF's frequencies differ from all of the pre-existing MF signaling protocols between switching centers: MF / R1, R2, CCS4, CCS5, and others that were later replaced by SS7 digital signaling.

DTMF, as used in push-button telephone tone dialing, was known throughout the Bell System by the trademark Touch-Tone.

This term was first used by AT & T in commerce on July 5, 1960 and then was introduced to the public on November 18, 1963, when the first push-button telephone was made available to the public.

It was AT & T's registered trademark from September 4, 1962 to March 13, 1984, and is standardized by ITU-T Recommendation Q. 23.

It is also known in the UK as MF4.