Template:Protected A subspace beacon is an omnidirectional repeating signal transmitted in the subspace realm.
A standard Starfleet combadge can be modified to emit a subspace beacon.
In an alternate timeline, Kathryn Janeway activated the subspace beacon in her 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 are equipped with subspace beacons, allowing personnel to track evacuating crew. (VOY: "Year of Hell, Part I")