In their normal operating mode, the Deep Space 9 defensive shields are energized to repulse a wide range of natural and artificial dangers. The primary system involves three large shield generators, mounted at the ends of the horizontal boom arms just below Ops. A secondary system of short-range emitters is installed at regular intervals around the outer edge of the Docking Ring. Both systems make use of original Terok Nor equipment with Starfleet power supply upgrades.