A datalink was a connection between devices which allowed for the exchange of information.
In 2372, Nog accessed a 2024 historical database which noted that Gabriel Bell established a wide broadcast data link through Earth's planetary communications system Interface, where residents of Sanctuary District A discussed their day-to-day struggle to survive. (DS9: "Little Green Men")
In a holoprogram titled The Voyager Encounter, the Emergency Medical Android established a datalink between his neural net and the phaser array of the warship Voyager to reconfigure the phaser beam to carry a bio-agent into the atmosphere of the Kyrian and Vaskan homeworld for the targeting of Kyrian cities. (VOY: "Living Witness")