A Type-1 phaser was the smallest, most basic weapon carried by Starfleet and other Federation personnel. Type-1 phasers were typically carried when it was inappropriate to carry a larger weapon, such as on diplomatic missions, or "undercover" work.
The Type-1 had eight adjustible settings, ranging from stun to heat through disruption to disintegration. The 23rd century type-1 in use in the 2260's incorporated a small flip-up sight, and was fired by a trigger on the bottom front of the unit. Several versions of the Type-2 Phaser incorporated a Type-1 Phaser into their design.
A low power variant of the Type-1 was also available. This variant only had three settings, from light to heavy stun. 24th century type-1s could be programmed to fire automatically at set intervals.
In 2362, three unsolved homicides were committed by an assailant using a type-1 phaser on burn setting. In 2366, the murderer was determined to be Starfleet officer Dar Ableen.