Abstract: A system for dispensing mixed beverages has a processor to control the liquid dispensed at an outlet in dependence upon the demand of a user as input to a keypad. Carbonated water is fed to the outlet by way of tubing and a syrup concentrate is also fed therto by way of a tubing. The water and syrup is mixed in the correct quantities by way of respective proportional valves which adjust the quantity or flow rate of the two consituents fed through a mixing chamber in accordance with flow rate readings provided to the processor by respective flow transducers. The flow transducers measure the speed of flow ultrasonically and are able to provide flow rate readings at a rate of 50 per second. The proportional valves are able to adjust the quantities fed to the mixing chamber at a similar rate such that the mix can be reliably determined even if there are transitory pressure drops or viscosity changes in the system.