Ship-mounted phaser cannon
The ship mounted Federation cannon is an optronically targeted phaser. It was presumably first introduced in the USS Defiant. In the mirror universe the Defiant phaser cannons were called multi-targeting phaser banks by the Klingons.
The four cannons of the Defiant-class have been seen usually firing phaser bolts simultaneously in short rapid fire bursts and in only one direction. The cannons can also fire beams. The combined firepower of the four phaser cannons of the Defiant appears to be almost as powerful as the combined firepower of two wing-mounted disruptor cannons on a Klingon Bird-of-Prey.
The Defiant-class pulse-phaser cannon's blast was described as being layered similar to an onion, to increase the amount of damage actually delivered simultaneously to a shield grid, thus destabilizing it faster. It was formed by storing the phaser blast within a near-perfect crystal capacitor for several seconds and then being released. This storing effect could be shortened by adding in an outside source of power such as the Impulse Engine, thereby improving both output and efficiency.