Abstract: A method for monitoring vehicles from a central station, consisting of obtaining the approximate coordinates of each vehicle from signals transmitted by stations of the world omega network and using a vehicle-carried receiver. These approximate coordinates are corrected by reception and processing means, connected to fixed radiogoniometry beacons. Processing means connected to the vehicle-carried receiver supply the real coordinates of the vehicle to a vehicle-carried transmitter, the real coordinates being transmitted in coded form to a receiver of the central station. A bilateral sound communication between the station and the vehicles can be conducted by the communication means. Alarms on board vehicles can be transmitted to the station.

Abstract: The invention relates to a high frequency antenna tuning device. The antenna is connected to a power transmitter, which periodically supplies power signals at predetermined high frequencies. For each frequency, the tuning device comprises a tuning capacitor connected to a switch. These switches are connected to control means, which are in turn connected to identification outputs of the frequencies of the signals supplied by the generator. The device also comprises means for detecting power signals transmitted by the antenna, so as to prevent any switching throughout the duration of a power transmission by the antenna on one of the predetermined frequencies.