A phaser gun crew was a group of officers and enlisted crewmembers in the Weapons Department. From a phaser control room, a crew controlled the phasers with phaser stations on a Starfleet starship or installation in the 2250s and 2260s. If the phaser gun crew was killed or suffered heavy casualities during a battle, a standby crew was available to take their position. On the Constitution-class starships, a crew was located on Deck 5. Other names for this crew were phaser crew, weapons control, and weapons crew.
A crew worked in coordination with a navigator or a helmsman on the bridge. This individual was responsible for the performance of the crew. In training, a crew was tested by an exercise, which was a computer simulation program consisting of a series of attacks and evasion maneuvers. Each exercise had an exercise rating. In anticipation of battle, a crew would energize the phasers and acknowledge that they were ready to the bridge. During battle, a bridge officer would lock onto a target with a directional beam and then ordered the crew to fire the phasers.
In 2266, after the destruction of Balok's cube, aboard the USS Enterprise, Captain James T. Kirk felt the phaser gun crews were sluggish and Lieutenant Bailey was slow in locking them into the directional beam. He ordered that a series of exercises be performed until the crews were proficient. On the first exercise, the exercise rating was 94%. Before the crews began a second exercise, the Fesarius appeared on the ship's sensors. (TOS: "The Corbomite Maneuver")
Later that year, during the Neutral Zone Incursion, the weapons crew of Outpost 4 were killed by an attacking Romulan starship. With its weapons crews dead, the outpost couldn't return fire and was eventually destroyed by the ship. Later, on the Enterprise, Lieutenant Robert Tomlinson, a phaser gun crewmember, was the only casuality on the Federation ship in the battle between the two starships. (TOS: "Balance of Terror")
In 2267, after receiving a Code 7-10 from Eminiar VII, Captain Kirk ordered a yellow alert and placed the phaser gun crews on standby. After Kirk and Spock were reported overdue and missing on the surface of the planet Eminiar VII, Lieutenant DePaul reported that the crews had transmitted their readiness. (TOS: "A Taste of Armageddon")
Later that year, after receiving a report from Unit XY-75847 that Klingon ships were in their sector and before beaming down to the surface of Organia, Captain Kirk ordered that Hikaru Sulu have the crews stand by their positions. (TOS: "Errand of Mercy")
In 2268, after a Klingon battle cruiser had been detected, Captain Kirk placed the ship on yellow alert. He ordered the phaser crews to stand by their positions. Later, as the Klingon ship passed close to the Enterprise, the captain ordered the crews to stand by to fire on command; however, when it became clear that the former vessel was passing by without firing a shot, the phaser crews were ordered to hold their fire. (TOS: "Elaan of Troyius")