diff --git a/src/generate_heartbeat.m b/src/generate_heartbeat.m
index 4173468..40230d6 100644
--- a/src/generate_heartbeat.m
+++ b/src/generate_heartbeat.m
@@ -9,11 +9,14 @@ function x = generate_heartbeat(amplitude, frequency, phase, fs, duration, duty)
 % phase shift is in number of periods
 % fs is the sampling frequency: how many sample points per second
 % duration is time in seconds
-% duty cycle should be a number between 0 and 1.
-    % duty of 0 or less would return -amplitude for all sample points
-    % duty of 0.25 would return +amplitude for first quarter of each cycle
-        % then return -amplitude for the remaining three-fourths
-    % duty of 1 would return all +amplitude
+% duty cycle should be a number between 0 and 0.5.
+    % duty of 0 or less would return 0 for all sample points
+    % duty of 0.5 or less would return a heartbeat signal since there would be
+        % equal amount of space within 1 period to have the right and left sides be equal
+    % duty of greater than 0.5 but less than 1 would return a slope starting at that duty i.e.
+        % the left side but leaving little room to the right side
+    % duty of between 1 and 2 would give a sawtooth wave in the +amplitude.
+    % duty greater than 2 would return 0 for all sample points
    
 
     % initialize local variables from input arguments
@@ -29,11 +32,11 @@ function x = generate_heartbeat(amplitude, frequency, phase, fs, duration, duty)
         t = i * dt; % time at the i'th sample
         st = mod(frequency * t - phase, 1);
 
-        if (duty-0.25 < st && st < duty)
+        if (duty-(duty / 2) < st && st < duty)
             slope = amplitude / duty;
             intercept = -0.5 * amplitude;
             x(i) = slope * st + intercept;
-        elseif (duty < st && st < duty+0.25) 
+        elseif (duty < st && st < duty+(duty / 2)) 
             slope = amplitude / duty;
             intercept = -amplitude;
             x(i) = slope * st + (1.5 * intercept);