Image Number 6 for United States Patent #4071845.
A radio beacon navigation system wherein buoys placed at predetermined locations in a harbor or channel transmit identification signals. Every buoy is assigned a unique carrier frequency upon which is transmitted a signal capable of identifying the buoy. Each buoy is shown on harbor charts according to the unique properties of its signal. Radio receiving means carried aboard vessels navigating through the harbor or channel include means for determining the identity of the buoy from which signals are received and the direction from which the received signals emanate.