An arrangement for cross monitoring two independent signals. The arrangement a calculator configured to calculate a value depending upon a signal value, a drift value and a feedback value, and a determining unit configured to determine a larger of the calculated value and a first predetermined value. The arrangement also includes a comparing unit configured to compared the determine larger value with a second predetermined value and a delaying unit configured to delay the determined larger value and change status of the larger value to become an updated feedback value to be provided to the calculator. The arrangement is characterized in that the signal value includes information about an absolute value of a difference between the two independent generated signals.