A phase modulator could refer to several different devices. In the 22nd century, a phase modulator was the primary component of phase-modulated energy weapons, including phase-pistols and phase cannons, utilized by Starfleet. The modulator was the component which shifts the intensity of the weapon's energy beam. In 2370, while infiltrating Cardassian space in a runabout disguised as the Lissepian transport Martuk, Kira Nerys claimed to a Cardassian border guard that they were having trouble with their phase modulators, as cover for Chief Miles O'Brien's modifications. (DS9: "The Homecoming")