Previously designated as the ‘Type X+’ for security reasons, the Type XII phaser has been used in dedicated planetary defence arrays and as the main armament of heavy fortified starbases since 2363. It was considered that the Type XII was unsuitable for use on a starship because the power requirements were too high and the support systems too bulky. However, by 2368 technical improvements had allowed for considerable shrinkage in the size of the equipment, and ship power systems had become capable of supporting the weapon. The main phaser armament of the new Sovereign class starship therefore comprises Type XII phaser arrays as does the armament of the Prometheus class. These are the most powerful phaser weapons currently in use by the Federation.