DialABC Logo

DTMF Detection

There are many types of electronic gizmos and software available for detecting and generating DTMF tones. Many answering machines, fax machines, telephone enabled alarm systems, voice mail modems, and switchboards can detect DTMF tones. Some of these contain electronic cirtcuits dedicated to detecting DTMF tones while others contain digital signal processors which use one of several patented algorithms to detect DTMF tones in their digitized input signals.

You can also download a free program from Zeebar's web site for you Windows PC that will let you analyze sound samples on your own desktop.

The DialABC website allows you to look for DTMF tones in audio clips by uploading a data file containing the sound data.

How It Works

You use your browser to send a computer audio file which contains some DTMF tones to our web site, and then our web site sends a web page with the analysis results back to you.

DTMF Detection
Audio Data File
DTMF Detection DTMF Detection
DTMF Tone Detection Report
DTMF Detection Process

Here is more detail on what happens when you use our DTMF-Detecion software:

  1. the audio data is transfered from your system to our server and placed into a file for further processing
  2. our software uses sound file utilities to identify the audio format and to convert the audio data into a standard format (text, mono, 16kHz sample rate)
  3. we run the audio data through a frequency spectrum analysis to find the exact DTMF frequencies. this is necessary since your audio clip may come from an analog recording and these tend to mess up the frequencies
  4. having calibrated the frequency and volume, we use the spectrum analysis data to find DTMF frequencies in the audio data. The spectrum analysis data is left lying around for later processing.
  5. the detected DTMF frequencies are paired up, and the resulting information is run through another piece of magical code that sorts out what numbers are being punched when.
  6. Using Java2D, we draw a picture to help visualize what is going on in the audio sample. The picture essentially consists of the spectrum analysis data (see above) plus scales and is annotated to show where the DTMF tone pairs were found.
  7. A web page is generated containing the table of detected DTMF tones as well as a summary of the above analysis plus the pretty picture.

Further questions are probably already answered in the FAQ.
Last updated Tuesday December 11 2012
For more info contact Zeebar Technology Services, Inc..
(C) Copyright 1996-2006 by Helmut Hissen and Zeebar Technology Services, Inc.
All rights reserved.
Zeebar Technology Services, Inc