Re: DFT taps for DTMF

Hello Roger,


What size of DFT whould be appropriate for DTMF?

I know the bands of the tones are quite large to allow generation
without crystals, which suggests to me that you should not be too
critical.


You could match the BW to the old standard. Don't remember where that was published, could have been Bell. Nowadays it'll almost always be more precise in frequency but that depends on the application, whether or not there is a chance that signals could come from an old phone. Also, there are regs about how fast you must be able to detect each tone event (20msec?) so you can't go too low in BW.

--
Regards, Joerg

http://www.analogconsultants.com
.

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