A control system includes: a transmission device that transmits a plurality of signals having different frequencies from one of a first communication unit mounted in a vehicle and a second communication unit mounted in a mobile device carried by a user in such a manner that the plurality of signals are combined to generate a predetermined composite signal in an area located at a distance from the first communication unit, the distance being not more than a predetermined distance; and a permission device that permits a predetermined action of the vehicle when the predetermined composite signal generated in the area from the plurality of signals transmitted by the transmission device is detected and an authentication signal transmitted by the second communication unit is authenticated as an authorized authentication signal for the vehicle.