Introduction: DTMF - Dual Tone Multi-Frequency Project

By VoltageLab
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DTMF (dual tone multi frequency) is the signal to the phone company that you generate when you press an ordinary telephone's touch keys. In the United States and perhaps elsewhere, it's known as "Touchtone" phone (formerly a registered trademark of AT&T).

Step 1: DTMF Circuit Diagram

DTMF ( Dual Tone Multiple Frequency ) is used to send to signals for button presses on telephones. The data is typically sent over voice channels and so in order to distinguish from human voice , when you hit a button the phone generates two tones of different frequencies - one lower frequency and one high frequency.

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Step 2: DTMF PCB

The reason why DTMF continues to be the standard method for signaling between a phone and an IVR is slightly more complicated. It seems logical to assume that as speech recognition technology for computers and mobile devices improved there should be corresponding to improvement when interacting with an IVR over the phone. Unfortunately, the big difference between local speech recognition and calling into an IVR is the resolution of the audio stream. Local speech recognition systems rely on high quality 44.1KHz, 16-bit PCM audio coming directly from your microphone to capture all of the subtlety of spoken language. Meanwhile phone calls are still limited by the public switched telephone network which takes that high quality audio and reduces it to 8KHz, 8-bit u-law (or a-law) audio. This lack of audio resolution means that speech recognition over the phone simply can not provide the same caliber of experience that users have come to expect with modern speech recognition systems.

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