diff --git a/src/main.c b/src/main.c
index 4c9bffb..1105f02 100644
--- a/src/main.c
+++ b/src/main.c
@@ -6,9 +6,9 @@
 
 //#define PI 3.141592653584
 
-// extern char* wave_signal; // simple waveform*
-// extern unsigned short duration; // equivalent as 2000 ms duration sound
-// extern unsigned int freq;
+extern char* wave_signal; // simple waveform*
+extern unsigned short duration; // equivalent as 2000 ms duration sound
+extern unsigned int freq;
 
 int main(void)
 {
diff --git a/src/sound4calc.c b/src/sound4calc.c
index e17d11f..27e9f7e 100644
--- a/src/sound4calc.c
+++ b/src/sound4calc.c
@@ -12,9 +12,9 @@ static struct {
       {   -1,   -1 }
   };
 
-  char* wave_signal = "-_"; // simple waveform*
-  unsigned short duration = 2000; // equivalent as 2000 ms duration sound
-  unsigned int freq = 440;
+char* wave_signal = "-_"; // simple waveform
+unsigned short duration = 2000; // equivalent as 2000 ms duration sound
+unsigned int freq = 440;
 
 void CallSequence()
 {