Background The touch-tone phone uses combinations of sounds of two frequencies to encode phone numbers The mapping of the frequencies to numbers and letters is given below: Frequency (Hz) 12091336 1477 ABCDEF 697 GHIJKL MNO 770 4 PRS TUV WXY 852 941 0 Therefore, for example, the number 2 (and letters A, B and C) is represented by the sum of equal-amplitude 697 and 1336 Hz sinusoids. A 0.25 sec-long burst of the tone digitized at 8 kHz sampling frequency can be constructed and tested via the following Matlab commands f1-697; %row frequency, units [Hz] f2-1336; %column frequency, fs-8000; %sampling frequency, [Hz ] duration=0.25; %duration of signal, [sec] t=[ 0: (1/fs):duration]; %time variable, (1/fs,-sampling A=0 . 5 ; %amplitude [Hz] period that phi need be tone-A*cos (2+p1 * f1 *t)+A*cos (2+p1*f2 *t); %Note sound (tone ,fs); %test the tone by sounding it not 0 Background The touch-tone phone uses combinations of sounds of two frequencies to encode phone numbers The mapping of the frequencies to numbers and letters is given below: Frequency (Hz) 12091336 1477 ABCDEF 697 GHIJKL MNO 770 4 PRS TUV WXY 852 941 0 Therefore, for example, the number 2 (and letters A, B and C) is represented by the sum of equal-amplitude 697 and 1336 Hz sinusoids. A 0.25 sec-long burst of the tone digitized at 8 kHz sampling frequency can be constructed and tested via the following Matlab commands f1-697; %row frequency, units [Hz] f2-1336; %column frequency, fs-8000; %sampling frequency, [Hz ] duration=0.25; %duration of signal, [sec] t=[ 0: (1/fs):duration]; %time variable, (1/fs,-sampling A=0 . 5 ; %amplitude [Hz] period that phi need be tone-A*cos (2+p1 * f1 *t)+A*cos (2+p1*f2 *t); %Note sound (tone ,fs); %test the tone by sounding it not 0