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DTMF decode

Telephones have been in existence since the olden days. The only difference between the telephones back then and now is the technology used. As technology continues to evolve, so does the technology applied in the phones. A while back, the cellphone system had to be operated physically. This occurred in a telephone exchange switch room with an operator. The operator helped the caller to connect to the other end of the line with call instructions provided. This proved to be cumbersome. With time, however, the DTMF technology emerged. This provided a solution to challenges brought by the earlier methods by enabling the automatic switching between two lines with the help of the DTMF decoder. Here is an overview of the DTMF technology.

What is DTMF?
Referred to as the Dual Tone Multi-Frequency in full, DTMF refers to some kind of a signalling system. Information passing through phone lines usually uses this type of signal system. When we want to make a phone call, we usually enter the number that we wish to dial in our telephone’s touch keys. When we do this, the signalling system known as DTMF is then applied to identify the dialled numbers. That is, the number pushed on the keypad on your phone is also called the DTMF keypad.

For this to be possible, a key is usually built as a combination of two sine wave tones. As represented on the DTMF keypad, the tones are referred to as frequencies in rows and columns. A voice frequency is used by the DTMF to switch on the long-distance signalling to the number that has just been keyed.

Hence, with the Dual Tone Multi-Frequency technology, two tones with particular frequencies are generated every time we dial a key on our phones. This means that there will be two specific frequencies for the tone. When looking at the first specific frequency, we get that it is the frequency that is high. On the other hand, the second frequency is seen to be a low one. Different particular low and high signals are sent when you press different digits on your phone. For example, when you press the number ‘1’, a low frequency of 697 Hz and a high frequency of 1209 Hz is sent while for a symbol ‘#’, we have a 941 Hz low frequency and a 1447 Hz high frequency.

The Working of the DTMF Decoder
The process of producing a call tone constituting two frequencies is where the DTMF technology is applied. The frequencies are transmitted through a communication medium. When it gets to the telephone exchange switch room, this is where you will find the DTMF decoder. With this, the frequencies of the caller are decoded into digital code. These digital codes are what will provide the address of the receiver of the call. The DTMF decoder is usually able to differentiate the tones from a DTMF. As a result, it can accurately generate digital code equivalent to the key entered in the DTMF keypad. The DTMF keypad is therefore applied in most mobile phones and landlines.

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