Abstract: In a method of controlling a frequency via an asynchronous transmission network, signals received at the output of the asynchronous transmission network have been clocked at a reference frequency and transmitted by the network with respective varying transit delays and the frequency of a local clock is slaved to the reference frequency by means of an error signal formed from selected received signals with minimal transit delays. Applications include local mobile telephone networks.

Abstract: Passengers on board a vehicle make and receive calls via a satellite network. That network sees each passenger involved in a call as a temporary dummy subscriber of the satellite network. Thus the satellite network is used to manage the roaming of passengers on aircraft. An intermediate network and the terrestrial mobile telephone network therefore do not need to manage the roaming of the aircraft. The terrestrial mobile telephone network sees each node of the intermediate network as a dummy base station and each passenger involved in a call as a dummy mobile subscriber of the terrestrial mobile telephone network, in the service area of one of the dummy base stations. The terrestrial fixed telephone network sees each passenger involved in a call as a subscriber of another fixed network managed by another operator. The intermediate network sees the satellite network as a standard terrestrial mobile telephone network, able to manage the roaming of its subscribers itself.

Abstract: An onboard system determines the position of a vehicle from radio signals from a constellation of navigation satellites and periodically transmits to a traffic control center the position thus determined, a time label supplied by the constellation of navigation satellites and the identity of the vehicle. A central system for accurately locating at least one vehicle provided with a system of the above kind calculates the position at the current time as a function of the position and the speed vector of the vehicle and the time label transmitted by the vehicle. These systems can determine a position periodically and with great accuracy because the time label supplied by the constellation of navigation satellites can be used to compensate fluctuations in the transmission time between the vehicle and the traffic control center when the position is received in the traffic control center.