Abstract: 1. In passive detection and tracking apparatus, in combination, a plurality of directional signal obtaining means for obtaining from radiant energy received from the same source a plurality of signals which vary in predetermined manners with variations in the direction from the passive detection and tracking apparatus to said source, gating means operatively connected to said plurality of signal obtaining means, and indicator means operatively connected to said gating means, said gating means being constructed and arranged to pass to the indicator means certain signals only while said plurality of signals have preselected relative characteristics with respect to each other, said indicator means being constructed and arranged to utilize the passed signals to provide an indication of the direction to said source.