internal void CounterThreadHandler(object callbackParam)
        {
            IDuplexCalcCallback callback = (IDuplexCalcCallback)callbackParam;

            timer           = new System.Timers.Timer(interval);
            timer.Elapsed  += (source, e) => TimerHandler(source, e, callback);
            timer.AutoReset = true;
            timer.Enabled   = true;
        }
 internal void TimerHandler(Object source, ElapsedEventArgs e, IDuplexCalcCallback callback)
 {
     callback.CounterIncrement();
 }