(covers information from several alternate timelines)
A transporter relay
A transporter relay was a device used to give a transporter something to lock onto in order to beam an inert object from one place to another.
The USS Voyager encountered a subspace sinkhole in the Delta Quadrant in 2375, while searching for a missing shuttlecraft manned by Lieutenant Commander Tuvok, Ensign Tom Paris, and The Doctor. As the crew attempted a rescue operation, they encountered a starship commanded by Yost, supervisor of Renovation Team Nova, who was on a mission to seal the sinkhole. As Yost fired antigraviton beams at the sinkhole, the Voyager crew managed to use the multispatial probe as a transporter relay, transporting Tuvok, Paris, The Doctor, and Noss, a survivor of a previous crash, safely aboard the ship. The sinkhole's opening then closed and eventually the sinkhole collapsed, crushing everything inside. (VOY: "Gravity")
In an alternate 2390, Chakotay placed a transporter relay on the neck of deceased Seven of Nine, who was aboard the crash landed USS Voyager that was frozen under glacial ice, and had Tessa Omond aboard the Delta Flyer lock on to the transporter relay that was placed upon the corpse and beam her to the lab aboard the small ship. (VOY: "Timeless")