A Type-X phaser was a type of phaser emitter usually installed on Federation starships.
History[]
By the 2370s decade, Federation starship classes such as the Starfleet Galaxy-class, Nebula-class, Akira-class, Intrepid-class, Norway-class, Nova-class, Saber-class and the Andorian Defense Force Atlira-class were all equipped with a number of phaser arrays consisting of multiple emitters each of this type. At the time, they were the heaviest type of phaser installed on starships. (TNG reference: Star Trek: The Next Generation Technical Manual, DS9 reference: Star Trek: Deep Space Nine Technical Manual, Decipher RPG module: Starships, Last Unicorn RPG module: The Andorians: Among the Clans)