The mark V personal phaser was a model of hand-held directed energy phaser weapon, a hand phaser used by Starfleet in the 24th century. (FASA RPG modules: Star Trek: The Next Generation Officer's Manual, Star Trek: The Next Generation First Year Sourcebook; TNG references: Star Trek: The Next Generation Technical Manual, Star Trek: The Next Generation Technical Journal)
These phasers were a departure from previous designs used by Starfleet with a dual-fire modification, as this type-1 hand unit was not designed to be mated with a type-2 phaser's phaser pistol power-pack grip. The power output of this weapon was rated at nearly three-times that of previous hand phaser models, including the Sestra phaser IB and the Atalskes phaser III. The mark V was wafer-thin, measuring less than ten centimeters in length and 2.5 centimeters wide. This made the weapon easily concealable for traveling members of Starfleet.
The weapon had a dual power-pack that could be recharged from a portable energy pack or from a recharge adapter fitted in a standard tricorder. A large pad on the unit provided user identification, ensuring that lost or stolen phasers could not be activated by unauthorized personnel while the unit was in communication with a ship's computer. Two control pads on the surface could be depressed to key a lethal or nonlethal beam, and a small screen displayed the power setting and beam width selection.
Phasers of this type were in use aboard the USS Enterprise-D after its launch in the early 2360s. They were normally carried by members of the crew at their stations on the bridge and at other places aboard ship. The phaser's control system allowed it to be fired on a timer, and to be set to overload by holding pressure on all control surfaces simultaneously for ten seconds. (FASA RPG modules: Star Trek: The Next Generation Officer's Manual, Star Trek: The Next Generation First Year Sourcebook; TNG references: Star Trek: The Next Generation Technical Manual, Star Trek: The Next Generation Technical Journal; TNG episode: "The Game")
Lieutenant R. Torres attempted to surreptitiously use a mark V phaser in a futile attempt to stun Q in 2364, on the ship's first mission to Farpoint Station. Q sensed the action and froze Torres in ice, leading Jean-Luc Picard to display the phaser to Q, to prove that the stun setting had indicated the Humans meant him no permanent harm. (TNG episode & novelization: Encounter at Farpoint)
Phasers of this type were the only weapons carried by members of the Enterprise-D senior staff when they were transported to Q's game planet where they faced French soldiers with hideous animal faces. While the animal-things were armed with directed energy weapon muskets, the hand phasers were able to simply vaporize them before they fired, until Q deactivated the weapons. (TNG episode: "Hide and Q")
William Riker snuck a phaser of this type into Starfleet Headquarters in 2364, in order to protect himself against conspirators who had been infected with bluegill-type neural parasites. Riker wore a false bluegill to disguise himself, and when the conspirators asked him to join them in a repast of live worms, Riker pretended to eat while drawing his phaser. He disabled a security commander, allowing Picard, who was the only other uninfected person present, to gather up a larger mark VI battle phaser. The pair used the two phasers to destroy the bluegill mother creature that was residing in Lieutenant Commander Dexter Remmick. (TNG episode: "Conspiracy")
Geordi La Forge attempted to use a weapon of this class to assassinate Governor Vagh of Krios in 2367, while La Forge was under the sway of a Romulan mind-control transmission received by his VISOR. Captain Jean-Luc Picard was the only person present who noticed the small phaser in Geordi's hand, and was able to deflect the blast. (TNG episode: "The Mind's Eye")
Wesley Crusher was detailed a sidearm of this type when he was a cadet at Starfleet Academy in 2368. When being pursued by the Enterprise security detail, he set the phaser to automatically fire at a force field put up to capture him. The phaser control computer fired randomly-timed bursts to fool ship's sensors into thinking Wesley was remaining stationary firing at that location. (TNG episode: "The Game")
This phaser was created for the premiere of the 1980s Star Trek: The Next Generation television series as a modernization of the familiar Sestra phaser I of previous productions. The prop ended up being used quite sparingly since it was so hard to see on screen. The production staff of the series called this the "cricket phaser" for that reason.