Phase weapon
From Memory Alpha, the free Star Trek reference
Phase weapons, or Phase-modulated energy weapons, were a type of directed energy device, a particle weapon, used by the Earth Starfleet. They were first used in the early 2150s, and had both non-lethal stun and lethal firing settings
Malcolm Reed showed Jonathan Archer a phase pistol for the first time in 2151 shortly before the first time Archer faced down Silik, recovering the Klingon agent Klaang from Silik's Suliban Helix. (ENT: "Broken Bow")
The Enterprise (NX-01) was refitted with internaly mounted retractable phase cannons during the first year of its interstellar exploration mission. (ENT: "Silent Enemy")
- Spock remarked that the Earth-Romulan War was fought with atomic weapons (TOS: "Balance of Terror"). Given that phase weapons are fundamentally different technology, it can be assumed Earth Starfleet was only able to outfit Enterprise, Columbia, and scant other ships with such weapons, falling back to nuclear-based spatial torpedoes for the rest of the fleet.
