Multi-spectral cloaking system

A multi-spectral cloaking system was a fictional cloaking technology invented by The Doctor in 2378 to dissuade Commander Chakotay from attempting to circumvent the defenses of the also fictional R'Kaal.

According to Kathryn Janeway, it was likely that they could destroy USS Voyager before anyone became aware of their presence. (VOY: "Renaissance Man")