Abstract: A system for exchanging information by means of transmitted RF signals between a fixed location interrogator and a vehicle transponder moving in the vicinity of the interrogator. The transponder responds to a first trigger signal from the interrogator by transmitting to the interrogator a first data message derived from data stored in a transponder memory. The interrogator then remotely reprograms the transponder memory and generates a second trigger pulse. The transponder responds to the second trigger pulse by transmitting the reprogrammed data it then stores and the interrogator analyzes the last mentioned transmission to determine if the transponder properly received and responded to the reprogramming.

Abstract: An antenna system for mounting in a roadway comprised of an electrically lossy material. The antenna system has a reflector trough shield filled with a solid dielectric. An antenna, preferably comprised of coaxial cable, is positioned in the reflector trough, which prevents electromagnetic waves radiated by the antenna from being lost into the roadway.