ECE 381: laboratory 2

Touch-tone telephone dialing and music synthesis Part III. Assignment 1. Write a MATLAB function that constructs and plays the DTMF signal

corresponding to a telephone number composed of digits 0—9, and symbols * and

#. The exact specification of your function is as follows: function dialSig = IastnameLabOZEx1(number,digitDur,silenoeDur.fs) "/0 Usage: dialSig = lastnameLabOZEx1(number,digitDur,silenceDur,fs); ‘i’o Inputs: number: Vector of digits to be dialed (i.e., of integers 0,1, 9, 10,

% and 11, where 10 and 11 represent the symbols * and #, respectively) % digitDur: Duration of dual-tone signal per digit in seconds % silenceDur: Duration of silence between digits in seconds % (must be at least 0.005 seconds) % is: Sampling frequency in Hertz

% Output: dialSig: Sampled dial signal as a column vector

"/0 Side effect: Sampled dial signal is also played out Your Implementation goes here, after one blank line following the leading

comment lines. To accomplish this task, create three functions to do the following tasks.

1. Convert a DMTF symbol into the two associated frequencies. (Hint: use a

long list of case statements).

2. Convert the two frequencies into a signal that is the sum of two

cosines.

3. Complete the dialsig function above to loop through the DTMF symbols

and play the sequence of sounds and silence periods. In the lab, experiment with different digit and silence durations to make the

sound match with your everyday experience. Your dial signal will be tested by

this function that is posted on Canvas: function y = getnum( x, is) % Y = GETNUM(X,Fs) is the telephone number extracted from the sampled

% DTMF signal X, where F5 is the frequency in Hertz at which X has been

% sampled. The default value of 8.192 Hz is assumed if F5 is omitted. So, as an example, if your function is right, you will see as well as hear

the dial signal. If you wish, you can make all but the first input argument

to your function optional. » camnnmumumm 312 a 41s 31.031511921319211