Interplexing Beacon
An Interplexing Beacon is a type of subspace transmitter that allows long distance communication. They are frequently utilized by the Borg Collective to maintain communications with one another across long distances, such as from the Alpha Quadrant to the Delta Quadrant. Interplexing beacons can be found in the Cranial Implants of Borg Drones, and each drone has a distinct Translink Frequency.
In 2063, a group of Borg from 2373 attempted to construct an interplexing beacon on the deflector dish of the USS Enterprise-E, so they could contact the Borg of that time period and call for reinforcements. They were thwarted by Captain Picard, Lieutenant Commander Worf and Lieutenant Hawk, who disengaged the deflector from the ship and then destroyed it. (Star Trek: First Contact)
In 2375, Seven of Nine received a set of phase corrections through her interplexing beacon during USS Voyager's Quantum Slipstream flight, that collapsed the slipstream and saved the ship from destruction. The message had been sent by a future Harry Kim from an alternate timeline. (VOY: "Timeless")
Later that year, a team aboard the Delta Flyer sent Seven of Nine a covert message through her interplexing beacon while she was aboard the Unicomplex. Nevertheless, the Borg Queen detected the transmission and was able to trace it back to the Flyer. (VOY: "Dark Frontier")
