A phase pistol is basically a hand phaser with low blood pressure. They were introduced to Earth's Starfleet in the 22nd century. Like later models of hand phaser, the phase pistol has a stun setting and a kill setting; it lacks the wider range of settings available on subsequent phaser weapons.
Like most later phasers, they have obvious design flaws. They have neither sights nor trigger guards, making them dangerous to handle and difficult to aim at greater than point-blank range, although unlike some later phaser pistols, they have a more conventional pistol grip.