After being stranded in the Delta Quadrant in 2371, the USS Equinox received supplies from the Ankari and witnessed the summoning beacon being used. The Equinox crew purchased their own beacon to summon the lifeforms for study, to accidentally discover that the beings could be used to enhance their warp drive.
In early 2376, after the Equinox escaped the USS Voyager, the Voyager crew contacted the Ankari for assistance. In Voyager's cargo bay, an Ankari used the summoning beacon and acted as an intermediary between Kathryn Janeway and the aliens. (VOY: "Equinox", "Equinox, Part II")