It also allows for the acknowledgment of messages and alarms from pagers and, in banking, the transmission of your account number and sort code. In telephony, the DTMF technology behind tone phones (also known in the UK as MF4) has facilitated many additional features such as caller return, caller display, reminder call, call waiting, three-way calling, call diversion, call barring, call minder and call sign. Then at the phone company end, DSPs (digital signal processors) are used to detect DTMF digits and translate them into numbers and # and * (and less commonly, the ABCD keys).

But one is generated from a high-frequency group and the other from a low frequency group – hence ‘dual tone’ – so that a voice can’t imitate those tones.

More commonly known as ‘touchtone phone’ technology (a registered trade mark of AT&T from its launch in 1963), DTMF is the signal you generate when you press or touch each key on your phone to convey the numbers you’re dialling, which progressively replaced the old loop disconnect (‘pulse’ or IWF) dialling method used by the rotary-dial telephones of yesteryear.Įach touch tone key, when pressed or touched, generates two tones of specified frequencies which can be carried by circuits designed to carry voice traffic. The birth of DTMFīut DTMF has been around for a lot longer than either of the above uses. The engine behind automated IVR menus for many years, it also now facilitates new ‘keypad payment by phone’ technology to help keep customers’ card numbers safe when paying over the phone for goods and services. The image of dual tone multi frequency signalling (DTMF) has come in for a makeover recently in contact centers.

Dual tone multi frequency