Type I Phaser
A Type I Phaser is the smallest, most basic weapon carried by Starfleet and other Federation personnel. Type I phasers are typically carried when it would be inappropriate to carry a larger weapon, such as on diplomatic missions, or "undercover" work.
The type I has eight adjustable settings, ranging from stun to heat through disruption to disintegration. The 23rd century type I in use in the 2260s 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 I phaser into their design.
A 23rd century type I phaser did not possess sufficient power to harm a silicon-based lifeform such as a Horta. (TOS: "The Devil in the Dark")
24th century type Is could be programmed to fire automatically at set intervals. (TNG: "The Game")
