Through operated alternately between a charging phase and a discharging phase, a charge pump converts an input voltage source into a drive voltage for being supplied to a light emitting diode. Oscillator circuits with piezoresistive resonators do have the advantage that they can perform self-sustaining oscillation without additional active devices as e. Light absorption, reflection andor florescence data are correlated with CO2 particle density and particle size, spray plume length, organic and inorganic spray additives, and water vapor content. The DWDM network may be enhanced with SONET, SDH, Ethernet, ATM, or other technology. The training harness may be used by children learning a sport, particularly a downhill gliding sport such as skiing or snowboarding. A method of manufacturing a heat exchanger tube is also provided.