How DTMF works?

DTMF (Dual Tone Multiple Frequency) is a bit sound generated when we touch any one of the telephone key. This sound arises with the combination of two separate frequencies merge together at the same time to produce a unique tone and it is mainly used in TELECOMMUNICATION.

The two sinusoidal signals of frequencies (Analog DTMF telephone signal) is a combination of low and high frequencies.

There are totally 16 pairs of dual tone multiple frequencies arranged in a 4*4 matrix (refer the below table so you can easily grasp and understand the combination of different frequencies)

4 x 4 dtmf matrixDTMF is one of the best signaling method between the telephones and switching centers, so this make much easier to control a robot through an interface from a very far distance.Each and every digit represented in the above table has two distinct LOW and HIGH frequency components. These components uniquely represent the respective telephone keypad number or symbol.

How can we use DTMF to control a robot?

Well, the DTMF was designed in a manner of sending the codes using microphone. Here we clearly pointed out so kind of frequency component codes has been transmitted from micro phones. So to convert these codes to digital ‘0’s and ‘1’s we need an interface and here we are using CM8870 as interface.

The interfacing technique of DTMF and CM8870 will be continued on the next article.

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Author: Raja Sundar

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