A group of ship-mounted phaser emitters fired together, the main energy weapon of Starfleet vessels in the 23rd century before phaser arrays replaced it.
Phaser banks are the main guns of Kirk's USS Enterprise. They are named in The Corbomite Maneuver and are fired in Balance of Terror, which shows a phaser control room where a crew carries out the firing orders passed down from the bridge.
The banks draw on the ship's main power and can be set to stun targets on a planet, as in A Piece of the Action, or tuned to act as proximity blasts. In Star Trek: The Motion Picture the refitted Enterprise channels phaser power through the warp engines, which leaves them useless when the engines fail in a wormhole.
The films show the banks firing short pulses, and they exchange fire with the USS Reliant in Star Trek II: The Wrath of Khan. By the 24th century the long phaser array, as on the Enterprise-D, has largely taken over, though the term is still used.