function touchtone(arg)% TOUCHTONE  Use FFT to synthesize and analyze telephone dialing%% The dual tone multi-frequency (DTMF) standard specifies that the tone% generated by a button on a telephone key pad is the sum of two sinusoids,% with frequencies determined by the button's row and column.%% The dial pad on the upper left allows you to select buttons and generate% the corresponding tones.%% The signal plotted on the upper right is a recording of the FAX number% for the MathWorks being dialed.  You can replay the entire signal, or% select individual segments.  The power plot is the magnitude of the FFT% of the signal being played.  What is the MathWorks FAX number?if nargin == 0   % Initialize   load touchtone         % Dialpad D, recorded signal y.sig, sample rate y.fs   n = length(y.sig);     % Total number of samples   t = (0:n-1)/y.fs;      % Time for entire signal   y = double(y.sig)/128; % Convert from signed 8 bit integers to doubles   clf   shg   set(gcf,'double','on','name','TouchTone', ...      'menu','none','numbertitle','off');   ax.dialpad = axes('pos',[.14 .46 .30 .50]);   imagesc(D)   colormap(gray)   set(ax.dialpad,'tag','dialpad',...      'userdata',[zeros(1,4) fix(10000*membranetx(1,1))],...      'xtick',[],'xcolor',[1 1 1],'ytick',[],'ycolor',[1 1 1]);   ax.signal = axes('pos',[.60 .60 .36 .25]);   plot(t,y,'k')   axis([min(t) max(t) -1 1])   xlabel('t(secs)')   set(ax.signal,'tag','signal','userdata',[t; y])   ax.sample = axes('pos',[.10 .16 .36 .25]);   axis([0 1/64 -5/4 5/4])   xlabel('t(secs)')   ax.power = axes('pos',[.60 .16 .36 .25]);   axis([500 1700 0 600])   xlabel('f(Hz)')   title('Power')   set(gcf,'userdata',ax,'windowbuttonupfcn', ...      'touchtone(get(gca,''tag''))')   uicontrol('units','normal','pos',[.72,.88,.12,.06], ...      'string','play all','callback','touchtone playall');   uicontrol('units','normal','pos',[.38,.02,.12,.05], ...      'string','help','callback','helpwin touchtone');   uicontrol('units','normal','pos',[.52,.02,.12,.05], ...      'string','close','callback','close(gcf)');elseif isequal(arg,'dialpad')   % DTMF, Dual tone multi-frequencies, Hz   fr = [697 770 852 941];   fc = [1209 1336 1477 1633];      % Time (seconds)   Fs = 32768;   t = 0:1/Fs:0.25;   % Plot component frequencies   cp = get(gca,'currentpoint');   k = min(max(ceil(cp(1,2)/50),1),4);   j = min(max(ceil(cp(1,1)/50),1),3);   f = [fr(k) fc(j)];   p = [1/2 1/2];   ax = get(gcf,'userdata');   set(gcf,'currentaxes',ax.power)   plot([f;f],[0*p;p],'c-',f,p,'b.','markersize',16)   axis([500 1700 0 1])   set(gca,'xtick',[fr(k) fc(j)])   xlabel('f(Hz)')   title('Power')   % Superimpose two sinusoidal tones   y1 = sin(2*pi*fr(k)*t);   y2 = sin(2*pi*fc(j)*t);   y = (y1 + y2)/2;   % Plot generated tone   set(gcf,'currentaxes',ax.sample)   plot(t(1:512),y(1:512));   axis([0 1/64 -5/4 5/4])   xlabel('t(secs)')   % Restore signal plot   set(gcf,'currentaxes',ax.signal)   ty = get(ax.signal,'userdata');   plot(ty(1,:),ty(2,:),'k')   axis([min(ty(1,:)) max(ty(1,:)) -1 1])   xlabel('t(secs)')   set(ax.signal,'tag','signal','userdata',ty)   % Play tone   sound(y,Fs)   % Extra   d = get(ax.dialpad,'userdata');   d(1:4) = d(2:5);   if k < 4, d(4) = -3*(k-1)-j; else, d(4) = 2-j; end   set(ax.dialpad,'userdata',d)   p = polyval(d,10);   if p == 7 | p == 2707      load touchtone      y = double(z.msg)/128;      if p > 7, y = fliplr(y); end      set(gcf,'currentaxes',ax.sample)      n = length(y);      t = (0:n-1)/z.fs;      plot(t,y)      axis([0 max(t) -1 1])      set(gcf,'currentaxes',ax.power)      f = (0:n-1)*z.fs/n;      plot(f,abs(fft(y-mean(y))),'color',[0 2/3 0])      axis([0 1000 0 700])      sound(y,z.fs)   endelseif isequal(arg,'playall')   % Restore plots   ax = get(gcf,'userdata');   set(gcf,'currentaxes',ax.signal)   ty = get(ax.signal,'userdata');   t = ty(1,:);   y = ty(2,:);   Fs = 1/t(2);   plot(t,y,'b')   axis([min(t) max(t) -1 1])   xlabel('t(secs)')   set(ax.signal,'tag','signal','userdata',ty)   delete(get(ax.sample,'child'))   % Plot the power of the entire signal   set(gcf,'currentaxes',ax.power)   n = length(y);   f = (Fs/n)*(0:n-1);   p = abs(fft(y));   plot(f,p,'color',[0 2/3 0]);   axis([500 1700 0 600])   xlabel('f(Hz)')   title('Power')   % Play the entire signal   sound(y,Fs);   pause(max(t))   set(get(ax.signal,'child'),'color','k')elseif isequal(arg,'signal')   ax = get(gcf,'userdata');   set(gcf,'currentaxes',ax.signal)   ty = get(ax.signal,'userdata');   t = ty(1,:);   y = ty(2,:);   Fs = 1/t(2);   n = length(y);   segs = 11;        % Number of equally spaced segments   nseg = n/segs;    % Number of samples in one segment   % Highlight segment   cp = get(gca,'currentpoint');   k = ceil(cp(1,1)*segs/max(t));   if k < 1 | k > segs, return, end   j0 = (k-1)*nseg+1;   j1 = k*nseg;   j = j0:j1;   je = [1:j0 j1:n];   plot(t(j),y(j),'b-',t(je),y(je),'k-', ...      [t(j0) t(j0)],[-1 1],'k-',[t(j1) t(j1)],[-1 1],'k-');   axis([min(t) max(t) -1 1])   xlabel('t(secs)')   set(ax.signal,'tag','signal','userdata',[t; y])   % Zoom in   set(gcf,'currentaxes',ax.sample)   jz = j0+round(mean(find(y(j)>.5)));   tz = round(10*t(jz))/10;   jk = find(abs(t-tz) == min(abs(t-tz)))+(-64:64);   plot(t(jk),y(jk))   axis([min(t(jk)) max(t(jk)) -1 1])   xlabel('t(secs)')   % Fourier components   set(gcf,'currentaxes',ax.power)   p = abs(fft(y(j)));   f = (Fs/nseg)*(j-j0);   plot(f,p,'color',[0 2/3 0])   axis([500 1700 0 300])   xlabel('f(Hz)')   title('Power')   % Play segment   sound(y(j))end