DTMF Decocde

DTMF Decoder

   While working on the next version of WinRepeat,
I wrote a simple DTMF decoder program that uses
the sound card and FFT to decode DTMF..

   It uses Murphy McCauley's FFTAudio code for Visual
Basic 5. You can check out some of his other programs at

   Operation is very simple..Just hook audio to
the the line in of the sound card, start the program. When a
correct pair of tones appear the number will apear in the text
box...As with all DSP software false numbers may apear...If too
many are apearing, try turning the input volume down...The peaks
of the dtmf tones should just reach the top of the display...

Here is a screen shot.....

If it sounds like a program you would like to try, you can
download it here...DTMF.ZIP

Several people have emailed and asked for the source so
I have decided to put it on the web....Good luck...DTMF source

If you find it useful or have a suggestion you can send me

Thanks...Scott (KB5RYO)

Johnny Booth sent the following mods to help stop false readings..
Put the follwing on the declrations..
Private Declare Sub Sleep Lib "kernel32" (ByVal dwMillisonds as Long)
Then add Sleep(40) after the DoEvents routine...
Hope this helps and good luck with you projects....

Go back to the home page What I have in the shack Places to go and things to do A few pictures of the radios Repeater software