A tachyon scan, also known as a tachyon sweep or tachyon signal, involved a starship emitting a tachyon beam at a particular location in an attempt to detect cloaked vessels by finding tachyon emissions given off by a cloaking device. Although a tachyon scan would detect most vessels using a cloaking device, its range was relatively limited but could be vastly increased by setting up a tachyon detection grid. (TNG: "Redemption II" , "Face of the Enemy" ; DS9: "Apocalypse Rising") This technique could also be used to scan quantum singularities. (VOY: "Parallax")