diff --git a/FDTD/operator.cpp b/FDTD/operator.cpp
index 7b10a54..01dc573 100644
--- a/FDTD/operator.cpp
+++ b/FDTD/operator.cpp
@@ -35,6 +35,7 @@ Operator::Operator() : Operator_Base()
 {
 	Exc = 0;
 	m_InvaildTimestep = false;
+	m_TimeStepVar = 3;
 }
 
 Operator::~Operator()
@@ -1192,11 +1193,11 @@ bool Operator::Calc_EC()
 
 double Operator::CalcTimestep()
 {
-#if 1  //use the new timestep-calc (1) or the old one (0)
-	return CalcTimestep_Var3(); //the biggest one for cartesian meshes
-#else
+	if (m_TimeStepVar==3)
+		return CalcTimestep_Var3(); //the biggest one for cartesian meshes
+
+	//variant 1 is default
 	return CalcTimestep_Var1();
-#endif
 }
 
 ////Berechnung nach Andreas Rennings Dissertation 2008, Seite 66, Formel 4.52
diff --git a/FDTD/operator.h b/FDTD/operator.h
index 223e5a7..38d3bb2 100644
--- a/FDTD/operator.h
+++ b/FDTD/operator.h
@@ -156,6 +156,7 @@ protected:
 	virtual void CalcPEC_Curves();	//internal to CalcPEC
 
 	//Calc timestep only internal use
+	int m_TimeStepVar;
 	virtual double CalcTimestep();
 	double opt_dT;
 	bool m_InvaildTimestep;
diff --git a/FDTD/operator_cylinder.cpp b/FDTD/operator_cylinder.cpp
index 6de018b..9f520a1 100644
--- a/FDTD/operator_cylinder.cpp
+++ b/FDTD/operator_cylinder.cpp
@@ -229,5 +229,6 @@ void Operator_Cylinder::AddExtension(Operator_Extension* op_ext)
 
 double Operator_Cylinder::CalcTimestep()
 {
-	return CalcTimestep_Var1();
+	m_TimeStepVar = 1;
+	return Operator_Multithread::CalcTimestep();
 }