diff --git a/Fir1fixed.cpp b/Fir1fixed.cpp
index 6abfe99..9a2a0d0 100644
--- a/Fir1fixed.cpp
+++ b/Fir1fixed.cpp
@@ -20,7 +20,7 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 */
 
-/* (C) 2013 Graeme Hattan & Bernd Porr */
+/* (C) 2013-2019 Graeme Hattan & Bernd Porr */
 
 #include "Fir1fixed.h"
 
@@ -66,7 +66,7 @@ Fir1fixed::Fir1fixed(const char* coeffFile,
 		rewind(f);
 	}
 
-	assert (taps > 0);
+	if (taps < 1) throw std::invalid_argument("No data in the file.");
 	
 	buffer = new short int[taps];
 	coefficients = new short int[taps];
@@ -74,16 +74,15 @@ Fir1fixed::Fir1fixed(const char* coeffFile,
 	assert( buffer != NULL );
 	assert( coefficients != NULL );
 
-	for(int i=0;i<taps;i++)
+	for(unsigned i=0;i<taps;i++)
 	{
 		float a;
-		// we scan  first as float because C gets
+		// we scan first as float because C gets
 		// upset with numbers written as 6E2.
 		if (fscanf(f,"%f\n",&a)<1)
 		{
 			char tmp[256];
 			sprintf(tmp,"Could not read the coefficients from %s\n",coeffFile);
-			taps = 0;
 			throw std::invalid_argument(tmp);
 		}
 		coefficients[i] = (short int)(a);
diff --git a/Fir1fixed.h b/Fir1fixed.h
index 22068d9..bd1424f 100644
--- a/Fir1fixed.h
+++ b/Fir1fixed.h
@@ -35,7 +35,7 @@ THE SOFTWARE.
 class Fir1fixed {
 public:
         /**
-         * Coefficients as an array of short ints
+         * Coefficients as an array of short ints (and length provided separately)
          * \param coefficients Array of the coefficients scaled up by 2^bitshift
          * \param bitshift Scaling factor of the coefficients as power of 2: 2^bitshift
          * \param number_of_taps Number of taps (= number of coefficients)
@@ -45,7 +45,7 @@ class Fir1fixed {
 		  unsigned number_of_taps);
 
 	/**
-         * Coefficients as an array of const short ints (length automatically detected)
+         * Coefficients as an const array of short ints (and length automatically detected)
          * \param _coefficients Array of the coefficients (const short) scaled up by 2^bitshift
          * \param bitshift Scaling factor of the coefficients as power of 2: 2^bitshift
          **/
diff --git a/demo/fixeddemo.cpp b/demo/fixeddemo.cpp
index d5d40e2..5574ae2 100644
--- a/demo/fixeddemo.cpp
+++ b/demo/fixeddemo.cpp
@@ -20,14 +20,14 @@ int main (int,char**)
 	// inits the filter
 	Fir1fixed fir("coeff12bit.dat",12);
 
-	// resets the delay line to zero
-	fir.reset ();
-      
 	// gets the number of taps
 	int taps = fir.getTaps();
 
 	printf("taps = %d\n",taps);
 
+	const short int averageCoeff[] = {1,1,1,1};
+	Fir1fixed averageFilt(averageCoeff,2);
+
 	FILE *finput = fopen("ecg50hz.dat","rt");
 	FILE *foutput = fopen("ecg_filtered.dat","wt");
 	for(int i=0;i<10000;i++) 
@@ -36,7 +36,11 @@ int main (int,char**)
 		// we scan as float because the %d gets confused
                 // with 6E2 which is outputted by octave
 		if (fscanf(finput,"%f\n",&a)<1) break;
-		short int b = fir.filter((short int)a);
+		short int b = (short int)a;
+		// 50Hz removal
+		b = fir.filter(b);
+		// smoothing
+		b = averageFilt.filter(b);
 		fprintf(foutput,"%f\n",(float)b);
 	}
 	fclose(finput);