Question I
Part (a)

1.SOURCE CODE LISTING for numbers 0 - 9:

In this program we are going to load the .wav files into MATLAB code and we can be able to play the required key tones from 0 to 9 by executing the code and listen through the system output devices.

In order to execute the program, the .wav files must be present in the current directory in order to load or play the dial tones.

The time domain plot for the required key tone (including two frequency components) will be observed where the axis will be time on x axis &
Amplitude on Y axis.

Later the frequency Domain plot (indicating the dual frequencies) will be observed using fourier transform
of the time domain of the key tones and with the sampling rate of 8000 Hz .

In this plot the Dual tone Multiple Frequencies is observed in the plot (DTMF Concept) as each keytone is comprised of two frequency
components, one low frequency & one high frequency components. i.e. the Dual frequencies can be viewed separately in the plot for each
number from 0 - 9.