What is DTMF?

If you have a smartphone or any type of satellite phone at your home, then you must be aware of the DTMF technology introduced in them. The full abbreviation of DTMF is Dual Tone Multiple Frequency. It is also called as Touch Tone. The Dual tone multiple frequency was made as a replacement for the rotatory dial pad used in the past centuries. DTMF is easy to use and is widely accessible in today’s century. It is a general keypad present on the mobile phone and walkie-talkie. Whenever you press any digit on the touch key of your mobile phone, DTMF generates a signal. In this way, you get an answer.

DTMF is a very big achievement in telephone and radio technology. The first-ever DTMF was introduced in November 1963 by the bell system. At that time, the first-ever phone call was made digitally. The specific design for the DTMF was introduced by none other than John E. Karlin. He was an industrial psychologist for the human factor engineering department of Bell’s lab. DTMF was introduced in rectangular shape with all the numbers from 1 to 9 arranged in 3×3 order. And on the last row, there is ‘*’ and ‘#’ on either side of 0. There was another column with A to D digits in it. But later on, this column was omitted by the smartphones as there was no need. But this column is still found in some old CB radios.

Although there were pulse dialers, i.e., rotatory dial pads, there was a slight error in them in the past. The signals were sometimes blocked when the rotatory dial spins and comes to its original position. So, by the technology of this digital keypad in the form of DTMF, there is a lot of ease. As a result, you can make the calls with an increased dialing speed and less stress on the network. Because of all these properties, this new technology was loved by the generation and vice versa.

Through the full abbreviation of DTMF, we can conclude that DTMF produces dual frequencies every time we press a digit. Every digit from 0 to 9 is allocated with two frequencies. One is high tone frequency, and the other one is low tone. When a digit is pressed, both the low tone and high tone frequencies are combined. As a result, each digit produces a specific tone frequency.

For example, the low tone frequency of digit 1 is 697 Hz, and the high tone frequency is 1209 Hz. When you press digit 1, a combined frequency of both high and low tone is sent to the phone company. In this way, the signal will be sent that you have pressed digit 1. This is how DTMF works.

The modification in DTMF from the start to now is that the column that contained the letters A, B, C, and D were removed when DTMF was introduced in the smartphones. All other frequencies and digits are the same till now.

In a nutshell, DTMF is a very big production by the bell system that has provided ease in so many ways. Before this technology, people were not aware of walkie-talkies and wireless phones as rotatory dial pads were only available. But because of DTMF, people can send information and messages over vast distances.