State entry beacon system

Abstract

A beacon system wherein a beacon station is placed at a landmark such as a state line adjacent a major highway to broadcast information-containing alternating directional signals. In addition, each vehicle may be equipped with a radio receiver, a receiving decoder and a data analysis processor for receiving data signals from the beacon station. The beacon station includes an information encoder for generating first and second alternating but distinct location signals, first and second directional antennas disposed to radiate in opposite directions along the path of travel, the directional antennas having a significant back attenuation, a radio frequency transmitter for broadcasting the two location signals, preferably as data packets, to vehicle-mounted receivers along the path of travel, and an r.f. switcher for switching signal output of the transmitter between the two antennas in synchronization with the two location signals. The data analysis processor associated with each vehicle-carried receiver includes a half-circular buffer operative to capture a succession of packets received from the receiving decoder, to preserve initially-received complete packets of the first location signals and to preserve last-received complete packets of the second location signals. The data analysis processor further includes means for processing the preserved packets in the half-circular buffer to determine the exact crossover point of the landmark marked by location of the transmitter.