Multiple realities
(covers information from several alternate timelines)

A phaser coupling was a component aboard a starship that transferred power to the phaser emitters.

In 2267 in a parallel universe, Captain Kirk ordered Scotty, both of whom were trying to return to their own universe, to disable the main phaser couplings on the ISS Enterprise, in an attempt to stop the destruction of the Halkan homeworld. (TOS: "Mirror, Mirror")

After the USS Voyager was taken over by the Kazon-Nistrim in 2372, Tom Paris instructed The Doctor and Lon Suder, the only crew members still aboard, to block the discharge from Voyager's backup phaser couplings while he attacked the primary couplings from his shuttlecraft. This caused the couplings to overload when the Kazon attempted to switch to backup phaser power during Paris' attack, releasing a massive amount of energy that inflicted significant casualties aboard. (VOY: "Basics, Part II")

When the Delta Flyer was disabled inside a graviton ellipse in 2376, the crew attempted to reroute power from the phaser couplings. (VOY: "One Small Step")