re set in the manner proper for starting to use a new half barrel keg when the button 10 is held in for ten 10 seconds the display means shows a flashing or blinking 34 3 5 34 and the microprocessor unit 8 is held ready for the next 30 seconds or other predetermined period of time to receive when the button 10 is held in for two 2 seconds the order to reset in the manner proper for starting the use of a quarter barrel keg 8 the reset button 10 is also used to allow for the adjustment needed in the case of using a different value for the pressure of carbon dioxide employed in the system in the event that some value other than 8 pounds per square inch gage is employed for example there is used a program such that if the reset button is held down for a period of fourteen 14 seconds then the display shows a flashing or blinking 34 8 34 the program being such that the pressure of 8 pounds per square inch gage is the 34 default value 34 presumed by the program in the absence of the setting of any other alternative value there may be provided for example the capability of changing the pressure counted upon as being used in the delivery system to such other values as 10 12 14 and 6 pounds per square inch gage when the display is displaying a flashing 34 8 34 then pressing the reset button for two 2 seconds will change the pressure setting from 8 pounds per square inch gage to 10 and successive further pressing of the reset button for intervals of two 2 seconds will change the pressure.