DTMF dialling

Touch-tone dialing, also know as DTMF dialling, is a method of sending signals from telephone customer's premises to central offices and beyond. The idea of touch-tone dialing was first introduced in 1964. Today, most of the telephones in the in developed countries use touch-tone dialling.

The advantage of touch tone signaling is that the signaling is voice band signal and the dialing can be done faster than with pulse dialing. The fact that DTMF signaling energy is in the voice frequency band, makes it possible to transmit signaling information (12 distinct signals) to any point in the telephone network to which voice can be transmitted. This makes it possible to use DTMF signals for remote control functions in additions to normal dialling. DTMF tones are used for controlling many modern automated telephone answering services.

Useful Links

• Disassembly Of A Touch-tone Phone - what is inside modern telephone
• DTMF - Most Of What You Wanted To Know
• DTMF Encoding and Decoding In C
• Generating DTMF tones using computer soundcard
• Touch-Tone Information - information on touch tone standards
• DTMF Encoding & Decoding: An application of The Goertzel Algorithm - This thesis was awarded the Nokia Telecommunications Electronic Engineering Award for the Best Final Year Thesis in the Faculty of Science and Technology for the year 1994.
• Sample stereo DTMF tones

Useful links

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