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Author Topic: Signal of dual tone multi frequency  (Read 1856 times)

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Offline tiofilo75Topic starter

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Signal of dual tone multi frequency
« on: May 07, 2013, 07:54:30 pm »
Hello everyone so I have recently become interested in the different tones emitted by phones when pressing the keypads. I am looking at the signal through an oscilloscope and I am wondering if there is a way to see the individual sinusoidal signals by separating the two that I am currently seeing. Thanks.
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Offline free_electron

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Re: Signal of dual tone multi frequency
« Reply #1 on: May 07, 2013, 08:02:00 pm »
filters. a whole bank of em
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Offline oPossum

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Re: Signal of dual tone multi frequency
« Reply #2 on: May 07, 2013, 08:27:57 pm »
For ordinary DTMF you could try a state variable filter (has HP and LP outputs) centered at about 1050 Hz.
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Offline Rasz

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Re: Signal of dual tone multi frequency
« Reply #3 on: May 07, 2013, 08:29:02 pm »
FFT will let you "see" that there are in fact two tones there
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