A Borg subspace transmitter that drones assembled on the navigational deflector of the Enterprise-E in 2063 in order to summon the Collective of that era to Earth.
The interplexing beacon appears in Star Trek: First Contact. Having failed to stop Zefram Cochrane's warp flight directly, the Borg aboard the Enterprise-E begin converting the deflector dish into a beacon that could call the Borg of the twenty-first century, who would find Earth defenceless.
Picard, Worf and Lieutenant Hawk put on environmental suits and walk across the outside of the hull in magnetic boots to stop them. Their plan is to release the three maglock clamps holding the dish so that it floats free.
Hawk is assimilated during the fight and Worf's suit is slashed, but the dish is released and Worf destroys it with a phaser rifle as it drifts away.