Component of both a target-designating system and a target-indicating system; it is an off-carriage observing instrument provided for the purpose of selecting an initial or new target, and it is electrically connected to the gun mount in such a manner as to slew the gun to the approximate azimuth and elevation of a selected target (when the selector is a component of a target-designating system), and to give the tracker an indication of the direction of approach of selected target (when the selector is a component of a target-indicating system).