Systems and methods are disclosed to provide clock generation. The apparatus comprises a nozzle unit having a nozzle to supply a gas into the duct via the fitting in a case where the nozzle is inserted into the fitting and a base member holding the nozzle member. In some embodiments a bonus is provided to the player if a rating associated with the player is worse than a threshold rating. A voltage controlled oscillator adjusts the switching frequency of the switching half-bridge to maintain zero volt switching and minimum current switching. The color of the digital watermark is calculated, based upon the obtained background color and intensity value.