So let's see how this works in a real application here. So I've got here this touchtone telephone sitting here classical telephone So what we are dealing here with or what we would like to to play with is we say This is zero here. Yeah, so this is zero if I press this button here. This zero gives us two tones a tone at 136 hertz and another tone at 941 hertz So what I've done is I've rigged this phone up to the USB ducts board in a very simple fashion. Yeah, so I use a plus five volt here with a resistor of 10k ran this into Into the phone and then That is to to ground here and then this here I just ran into my AD converter Yeah, so this just goes into the AD converter So so the AD converter as a USB ducts board Um, and so so I just starting now. There's also scope program here. So let's just move this here quickly over So what I do is I start this program comedy record here So it was a sampling rate of four kilohertz We're just using one channel and the minus X This gives us our Fourier transform window what I've just shown so this function and plots the Fourier spectrum of that So let's start comedy record. So let's now showing up here Let's just bring this on the screen here So let's now showing us Here the trace and so if I Now pick up the receiver then hopefully We should see something here now we see already a bit of my speech. Let's just Amplify this a bit more so if I know holds the receiver here onto my mouse We see that the speech is Easily recognizable here. So now let's pull our Fourier transform window Also on here just to see that this works So now This is the Fourier transform of me as I as I speak Yeah, so we see a quite a lot of different frequencies of using speech and it's a very complex spectrum generated by that So in order to test this that is really works and actually calculates the right frequencies That's the reason why I've got this phone here. So if I'm pressing now the button zero what we should see now is These two frequencies. So let's do that And we see that we are getting these two frequencies 941 and the 1336 hertz here So if I let's just go here Then we are getting the surrender spectrum of me speaking here. So if I'm pressing other buttons obviously we're getting different frequencies and that's the way how How is these different tones are detected just by running a Fourier transform and Detecting this and so the bottom window here. This is powered by our FFT w3 and this Gives us a beautiful FFT spectrum here while I'm speaking