DTMF Dial Function In the class you were given the first part of the function na

Question

DTMF Dial Function In the class you were given the first part of the function named "dtmf.m" to implement a DTMF dialer based on the frequency table defined in Figure 1. Figure 2 is the skeleton of the function presented in the class Row/Column 4 1209Hz 1336Hz1477Hz1633Hz 1 697Hz 2 770Hz 3 852Hz 4 941Hz 4 Figure 1: DTMF Frequency Table function xx=dtmfdial (keyNames, fs) %DTMFDIAL Create signal vector of DTMF tones that will dial a Touch Tone telephone. %usage: xx=dtmfdial (keyNames, f3) keyNames . character string with valid key names fs- sampling frequency xx= signal vector that is the concatenation of DTMF tones 10 11-dtmf.keys-.. 13 14-ff rows [697: 770: 852: 941: 15dtmf.colTones ones (4,1)ff cols: 16- dtmf. rowTones=ff rows* nes (1,4) ; ff_cols-[1209, 1336, 1477, 16331: Figure 2: First part of the dtmf.m (a DTMF phone dialer) Complete this function with additional lines of code so that it implements the following 1. The input to the function is a vector of characters, each one being equal to one of the key names on the telephone. ( The MATLAB structure called dtmf contains the key names in the field dtmf.keys which is a 4 × 4 array that corresponds exactly to the keyboard layout in Fig.1)

Explanation / Answer

ANSWER::

function xx = dtmfdial(keyNames,fs)
dtmf.keys = ...
['1','2','3','A';
'4','5','6','B';
'7','8','9','C';
'*','0','#','D'];
dtmf.colTones = ones(4,1)*[1209,1336,1477,1633];
dtmf.rowTones = [697;770;852;941]*ones(1,4);

dur1 = 0.20;
dur2 = 0.05;
tt = 0:1/fs:dur1;
xx = 0;
for ii = 1:length(keyNames)
keyName = keyNames(ii);
[r,c] = find(dtmf.keys==keyName);
if (numel(r) == 0 | numel(c) == 0)
continue
end;
tone = cos(2*pi*dtmf.rowTones(r,c)*tt) + cos(2*pi*dtmf.colTones(r,c)*tt);
xx = [xx, zeros(1, dur2*fs), tone];
end

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