A method and apparatus for determining the service life of a cyclic system the method including the steps of determining at least one characteristic of the system to determine a characteristic value and determining a cycle time of the system. A Fibonacci number clocked stored-program microcontroller generates a variable duty cycle higher frequency pulse width modulation carrier square wave output which is XOR modulated with a lower therapeutic frequency square wave output to control an H-Bridge driver capacitive coupled to an isolation transformer. The processing units can be controlled in order to place the components. The present invention provides a method of tracing which can be applied to an HBES algorithm structure. The invention is applicable to measurement of single optical or electrical pulses or pulses with a low repetition rate.