diff --git a/src/types/transferfunction.jl b/src/types/transferfunction.jl
index f0b7195..1c16a13 100644
@@ -56,2 +56,6 @@ tf(reshape(Vector[num], 1, 1), reshape(Vector[den], 1, 1), args...)
 
+# tf(sys) converts to TransferFunction
+tf(sys::LTISystem) = convert(TransferFunction, sys)
+
+
 # Function for creation of static gain

