Firing a photonic pulse
A photonic pulse was a type of starship-mounted form of evasion technology possessed by Kovin.
Entharan starship generated a photonic pulse, from the aft of his ship, that he fired at the USS Voyager, at a range of 9,000 kilometers. As a result, the pulse took Voyager's sensors offline, allowing Kovin to slip away undetected. In order for Voyager to recover from the pulse, the crew had to re-initialize the entire sensor array. (VOY: "Retrospect")