What is DTMF and how it’s generate and decode and if it have real application.
DTMF (Dual Tone Multi Frequency) or informally named as “Touch Tone”. Which allocation of a unique tone to each button on an appliance (made up of two frequencies - high and low)
The DTMF dialing system traces its roots to a technique AT&T developed in the 1950s called MF (Multi-Frequency) which was deployed within the AT&T telephone network to direct calls between switching facilities using in-band signaling. In the early 1960s, a derivative technique was offered by AT&T through its Bell System telephone companies as a "modern" way for network customers to place calls. In AT&Ts Compatibility Bulletin No. 105, AT&T described the product as "a method for pushbutton signaling from customer stations using the voice transmission path."
The consumer product was marketed by AT&T under the registered trade name Touch-Tone®. Other vendors of compatible telephone equipment called this same system "Tone" dialing or "DTMF".
The DTMF system uses eight different frequency signals transmitted in pairs to represent sixteen different numbers, symbols and letters. This table shows how the frequencies are organized: