Patent ID: 6181259
Filing Date: 2001-01-30
Classification: G07B

Abstract:
A vehicle-mounted device mounted on a vehicle for use in a road-to-vehicle communication system for radio communications with a road radio unit disposed on a road, said device comprising:an RF module for receiving and demodulating a carrier sent from the road radio unit;a receiver for receiving demodulated data from said RF module and outputting a detected signal in response to detection of predetermined data contained in the demodulated data;a frequency switching controller for performing a frequency search process to switch between reception frequencies of said RF module at a preset switching period and a plurality of preset reception frequencies, stopping said frequency search process when supplied with the detected signal from said receiver, and controlling said RF module to keep receiving the reception frequency at the time the detected signal from said receiver is supplied; anda controller for setting the switching period and the reception frequencies in said frequency switching controller, thereafter entering a sleep mode after elapse of a predetermined time, and canceling the sleep mode in response to said detected signal and performing road-to-vehicle communications with the road radio unit using data received by said receiver.