Shield generator

From Memory Alpha, the free Star Trek reference

A shield generator is a piece of equipment which generates some type of electromagnetic barrier or force field called a deflector shield, designed to deflect kinetic or electromagnetic energy.

A cloaking device ties into the deflector shield grid of a ship, rendering it unable to shield while cloaked. (TOS: "The Enterprise Incident")

In 2369 Major Kira Nerys suggested a Bajoran tactic to take over the shielded Federation freighter Norkova and overwhelm the mercenaries and Rao Vantika. During the Occupation of Bajor the Bajorans terrorists use to disable the shields of orbiting Cardassian freighters by taking their vessel close to the freighter, and overloading their shield generators with directed phaser fire. (DS9: "The Passenger")

The same year Miles O'Brien ordered the computer to restart all shield generator subsystems and received a 98,3 % efficiency. With this task, O'Brien tried to show Commander Sisko the "strange behavior" of the computer voice. (DS9: "The Forsaken")

In 2372 during the Klingon attack on Deep Space 9, Gowron ordered Martok to concentrate all fire on DS9's shield generators. They destroyed at least two of them, which was reported by Dax later. (DS9: "The Way of the Warrior")

During the Second Battle of Deep Space 9, the Dominion destroyed Deep Space 9's shield generator. (DS9: "Call to Arms")

The shield generators on the USS Defiant were configured differently from those on its predecessor, in order to improve protection against the Breen energy dissipator. (DS9: "The Dogs of War")

One, an advanced Borg drone with 29th-century technology, modified the shield generators of the USS Voyager in 2375, so that they could break free of a Borg sphere's tractor beam. (VOY: "Drone")

[edit] Background

The phrase "shields up," which saw widespread use in Star Trek, probably had its origin in classical warfare, when infantry would raise their shields to defend against incoming arrows or other projectiles. The order would be given when it was time for the soldier to raise his shield from the carry position.