(covers information from several alternate timelines)
A subspace beacon was an omnidirectional repeating signal transmitted in the subspace realm.
In 2153, Tellarite bounty hunter Skalaar deployed such a beacon as a decoy from the Tellarite shuttle he captained. Its warp signature was tracked by Enterprise NX-01 but the device was ultimately destroyed by that starship. (ENT: "Bounty")
In an alternate 2371, Kathryn Janeway activated the subspace beacon in her Starfleet combadge when she and Tom Paris were thrown back in time on an unknown Class M planet. The senior staff of the USS Voyager used the beacon to locate and attempt to retrieve Janeway and Paris. (VOY: "Time and Again")
Federation escape pods were equipped with subspace beacons, allowing personnel to track evacuating crew. In a specific alternate timeline, Janeway ordered her crew to evacuate Voyager due to its desperate situation. She told them that she would find them by homing in on subspace beacons in the escape pods. (VOY: "Year of Hell")
|amplifier • antenna • bandwidth • beacon • frequency • hyper- • interference • interplexing beacon • link • log • monitor • neural transceiver • relay • relay network • relay station • signal • static • transceiver • transmission • transmitter • transponder • wide-band|